tag:blogger.com,1999:blog-253506342024-03-13T11:32:24.561-07:00Mechanical EngineeringAll About Mechanical EngineeringNanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.comBlogger28125tag:blogger.com,1999:blog-25350634.post-21249912114047914412009-02-10T01:12:00.000-08:002009-02-10T01:23:47.070-08:00Coomber Rotary Engine<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCg2dmJwOesmXDFrTt3zro2OkwkCxCsM-xnHcI67wZDdH4pf7eBdPzexF1jiZjYQmYM2MN5qWerPg-buhjLD-sYeEh1tsvGsn0YP8IDcN9FtTTCvFBgOMD2c2uK_djCKcZCM0UZg/s1600-h/coomber.gif"><img style="cursor: pointer; width: 400px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCg2dmJwOesmXDFrTt3zro2OkwkCxCsM-xnHcI67wZDdH4pf7eBdPzexF1jiZjYQmYM2MN5qWerPg-buhjLD-sYeEh1tsvGsn0YP8IDcN9FtTTCvFBgOMD2c2uK_djCKcZCM0UZg/s400/coomber.gif" alt="" id="BLOGGER_PHOTO_ID_5301096916163995762" border="0" /></a><br />First learned of this delightful engine while attending the PRIME show in Oregon. A most prolific modeler, Marlyn Hadley, had one on display.<br /><br />Its have not illustrated the valve linkage, as not exactly sure what it looks like, It appears to be a rotary type, incorporated into the main drive shaft. Steam would be admitted to one end of the cylinder at a time, just as in any other double-acting steam engine.<br /><br />The inner dimension of the stationary ring is not circular, but is slightly elliptical. The main bearing is offset from the center of this ellipse by a one half the stroke length.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com14tag:blogger.com,1999:blog-25350634.post-90687382806519999612009-01-28T01:00:00.000-08:002009-01-28T01:05:33.796-08:00CO2 Motor<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVB_qSIrFFF7NWZBNN9kvuBlUjBp8EmWTAz_Y4ic7A1InFw99a8nCx3bGM7hTyynD8c9GwCvHgZtvP0l2xK4oSqG7aDIM1eWh6Rexp0K6i_az3CaEDhReqyeywCvQ9th6s7ovCrQ/s1600-h/co2.gif"><img style="cursor: pointer; width: 278px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVB_qSIrFFF7NWZBNN9kvuBlUjBp8EmWTAz_Y4ic7A1InFw99a8nCx3bGM7hTyynD8c9GwCvHgZtvP0l2xK4oSqG7aDIM1eWh6Rexp0K6i_az3CaEDhReqyeywCvQ9th6s7ovCrQ/s320/co2.gif" alt="" id="BLOGGER_PHOTO_ID_5296267607199211474" border="0" /></a><br />This style engine could be powered by steam (I've heard of at least one) but is more commonly seen in small model airplane engines powered by compressed air or CO2 (carbon dioxide) gas. The popular Air Hogs toy airplanes are propelled by this style motor.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgahzPCfCfE7AVh4dNn-30edJgIu_RjdBFMO8Hc9HAFL1cpN1qE579A0NjBYKGOXxIiD6BRQ8M-1jOchyImAbFPUdI1SfqBWgCyQfe1UuAUaTzCJ9jRLSSrNB7e5MtVyYNVo5xq-A/s1600-h/co2_1.gif"><img style="cursor: pointer; width: 234px; height: 292px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgahzPCfCfE7AVh4dNn-30edJgIu_RjdBFMO8Hc9HAFL1cpN1qE579A0NjBYKGOXxIiD6BRQ8M-1jOchyImAbFPUdI1SfqBWgCyQfe1UuAUaTzCJ9jRLSSrNB7e5MtVyYNVo5xq-A/s320/co2_1.gif" alt="" id="BLOGGER_PHOTO_ID_5296267608446278882" border="0" /></a><br />At the top of the stroke, the pin on the cylinder presses the ball valve upward, admitting high pressure gas into the cylinder. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhh4SnlNiSLnPhKBK-tcoKzYgsmi3j2DoYAWYfzRzkQP-Q17TYOCThC-4exRZr6oJusLjFfUz_fBlwK8a_rb8zh6s5BVZMloJrIczP1RAoLEjpvR9fR1rkhlOw1STT3_sEMa9pykg/s1600-h/co2_2.gif"><img style="cursor: pointer; width: 234px; height: 292px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhh4SnlNiSLnPhKBK-tcoKzYgsmi3j2DoYAWYfzRzkQP-Q17TYOCThC-4exRZr6oJusLjFfUz_fBlwK8a_rb8zh6s5BVZMloJrIczP1RAoLEjpvR9fR1rkhlOw1STT3_sEMa9pykg/s320/co2_2.gif" alt="" id="BLOGGER_PHOTO_ID_5296267608697611042" border="0" /></a><br />The gas expands, driving the piston downward. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiN3q5JbiDwD5Ys6b9LyYFM6nDZnEj8YvgrPBmHoFeIojiQ_ZZgK3QazuVCa9LD1sblbGxkkj4BZgRPUM2rZQ7gi6TY2rqdD-LokKpsROBHMGtlQVMZEeGx_iykPupc7h1XK4lpMw/s1600-h/co2_3.gif"><img style="cursor: pointer; width: 234px; height: 292px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiN3q5JbiDwD5Ys6b9LyYFM6nDZnEj8YvgrPBmHoFeIojiQ_ZZgK3QazuVCa9LD1sblbGxkkj4BZgRPUM2rZQ7gi6TY2rqdD-LokKpsROBHMGtlQVMZEeGx_iykPupc7h1XK4lpMw/s320/co2_3.gif" alt="" id="BLOGGER_PHOTO_ID_5296267607777527058" border="0" /></a><br />when the piston advances past the exhaust port, the high-pressure gas is released. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhojneHgKCHymZ8fL4-ZGttYwbEwLTBz9_8NNAc06toJzwZOIUEfoxqcZP-c8mFSj5RbBhc_bSZTzht5-Z2-D2RrG4gnohx20IKlB8UXLMbm3uSqUp48KSCv3X_E2k_KCTS3Qxe2g/s1600-h/co2_4.gif"><img style="cursor: pointer; width: 234px; height: 292px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhojneHgKCHymZ8fL4-ZGttYwbEwLTBz9_8NNAc06toJzwZOIUEfoxqcZP-c8mFSj5RbBhc_bSZTzht5-Z2-D2RrG4gnohx20IKlB8UXLMbm3uSqUp48KSCv3X_E2k_KCTS3Qxe2g/s320/co2_4.gif" alt="" id="BLOGGER_PHOTO_ID_5296267615216648514" border="0" /></a><br />Flywheel (or propeller) momentum carries the piston upward to complete the cycle. <br /><br />This animation also illustrates the CO2 reservoir, or "fuel tank." Compressed CO2 is a liquid and becomes a gas as the pressure is released. Another way to state this is that the liquid CO2 boils at normal atmospheric temperature and pressure, so one might say this engine runs on "CO2 steam."Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com180tag:blogger.com,1999:blog-25350634.post-52204668321104395302009-01-28T00:54:00.000-08:002009-01-28T01:00:09.206-08:00Oscillating Steam Engine<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUTuSz-6OFUHITKY2pC-2nnY1EHK50ZKbuxN6QmZsBbGth4GS_RhfgDRdMyDNJCJuiEkfjhhFJKnXVba_N9holLDrFTK0W-GFFDyZFhQA99zY5AVHfMw3exu-UvocWDhrJVQvtiQ/s1600-h/oscillator.gif"><img style="cursor: pointer; width: 244px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUTuSz-6OFUHITKY2pC-2nnY1EHK50ZKbuxN6QmZsBbGth4GS_RhfgDRdMyDNJCJuiEkfjhhFJKnXVba_N9holLDrFTK0W-GFFDyZFhQA99zY5AVHfMw3exu-UvocWDhrJVQvtiQ/s320/oscillator.gif" alt="" id="BLOGGER_PHOTO_ID_5296265725060332930" border="0" /></a><br />This style steam engine employs the cylinder as the steam valve. It operates on the same principle as the locomotive steam engine.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisy_6Z4Ot109m2ZhbFEDlppMrFyAWkct7vNq_5wG5TUeJeZc6e6An-58APKNl24L94Npr77qWVJm8KcMwPOHfJyXdeJkqONRnMo68rssfAHBMrNZ-QNTRnaH2OvDzeDMNv5gF43A/s1600-h/osc_1.gif"><img style="cursor: pointer; width: 288px; height: 242px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisy_6Z4Ot109m2ZhbFEDlppMrFyAWkct7vNq_5wG5TUeJeZc6e6An-58APKNl24L94Npr77qWVJm8KcMwPOHfJyXdeJkqONRnMo68rssfAHBMrNZ-QNTRnaH2OvDzeDMNv5gF43A/s320/osc_1.gif" alt="" id="BLOGGER_PHOTO_ID_5296265728966154322" border="0" /></a><br />Steam from the boiler enters the power manifold and is and is admitted to the top end of the cylinder when the cylinder port aligns with the manifold port. The steam presses the piston downward, driving the flywheel around one half turn.<br /> <a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDrbdy-nNYeAp37_v34T4UtEXD3nsPhYs8jpRfz5535LE2IDA106oLZWmvQ16VKDbF-NIA1xvCwVV8GpjjNYlvbQllI6cFQtC_5WLdv0VjD95QrwTyZZ2ZSodxFDCqcxze5bNZgw/s1600-h/osc_2.gif"><img style="cursor: pointer; width: 288px; height: 242px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDrbdy-nNYeAp37_v34T4UtEXD3nsPhYs8jpRfz5535LE2IDA106oLZWmvQ16VKDbF-NIA1xvCwVV8GpjjNYlvbQllI6cFQtC_5WLdv0VjD95QrwTyZZ2ZSodxFDCqcxze5bNZgw/s320/osc_2.gif" alt="" id="BLOGGER_PHOTO_ID_5296265727284856642" border="0" /></a><br /><br />At the end of the stroke the cylinder shifts, exposing the top port to the exhaust manifold. The expended steam is released.<br /> <a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihymR7j99RRsUXirws3yAeCcK5d7bP7gZPH2w3HFOBfpcORg8klORquHzdMYhzx4IoWD7I_CRJedYo1EN_J6mPK-kzmpEfyyPdam_GpzdW42QcvKuGp7UbaAWFvqFXFXQ-iv0feQ/s1600-h/osc_3.gif"><img style="cursor: pointer; width: 288px; height: 242px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihymR7j99RRsUXirws3yAeCcK5d7bP7gZPH2w3HFOBfpcORg8klORquHzdMYhzx4IoWD7I_CRJedYo1EN_J6mPK-kzmpEfyyPdam_GpzdW42QcvKuGp7UbaAWFvqFXFXQ-iv0feQ/s320/osc_3.gif" alt="" id="BLOGGER_PHOTO_ID_5296265729199536834" border="0" /></a><br />At the same time, the bottom cylinder port, aligns with the power manifold, admitting steam to the bottom end of the cylinder. This presses the piston upward, driving the flywheel around another half turn. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVZh6KM1w-fCNBhVMQ9d6CwAFQ2nbK9JTQxP2uyKljSZ7-DnIEwO3z7oprsmowQwm3Wubl3OQlLLHKso64sOmn7YWbhKE5sti34hvifhyphenhyphen1v3N2G0G0qM4ovn239jUTTSD4c2-j5Q/s1600-h/osc_4.gif"><img style="cursor: pointer; width: 288px; height: 242px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVZh6KM1w-fCNBhVMQ9d6CwAFQ2nbK9JTQxP2uyKljSZ7-DnIEwO3z7oprsmowQwm3Wubl3OQlLLHKso64sOmn7YWbhKE5sti34hvifhyphenhyphen1v3N2G0G0qM4ovn239jUTTSD4c2-j5Q/s320/osc_4.gif" alt="" id="BLOGGER_PHOTO_ID_5296265731792264290" border="0" /></a><br />At the end of the stroke, the bottom port aligns with the exhaust manifold, releasing the expended steam. <br /><br />Due to its exceedingly simple construction, this type of engine is popular in working toy steam engines, including one I had as a kid. An even simpler type employs power in only one direction, relying on flywheel momentum to carry the piston around for the remainder of the cycle. This is called a single acting engine. The type illustrated here is a double acting engine.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-60038429026663069552009-01-28T00:44:00.000-08:002009-01-28T00:51:31.674-08:00Steam Locomotive EngineSteam engines like this drove trains from the early 1800s to the 1950s. Though the engines varied in size and complexity, their fundamental operation remained essentially as illustrated here.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUxRxvTfX2iN5c0bMoFe9tCaUVhfB49CcRjr0WDbjV6yO0GnKjJlDs_ekNOtwHIvoKlt97XG6Tf8EjWiDC7bgjk41oN1Bvkh0kPobT_-oNVRRVfJLl096AHyK9SvbyNByVWPXl1w/s1600-h/locomotive.gif"><img style="margin: 0pt 10px 10px 0pt; cursor: pointer; width: 320px; height: 110px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUxRxvTfX2iN5c0bMoFe9tCaUVhfB49CcRjr0WDbjV6yO0GnKjJlDs_ekNOtwHIvoKlt97XG6Tf8EjWiDC7bgjk41oN1Bvkh0kPobT_-oNVRRVfJLl096AHyK9SvbyNByVWPXl1w/s320/locomotive.gif" alt="" id="BLOGGER_PHOTO_ID_5296263521287199138" border="0" /></a><br />In a steam engine, the boiler (fueled by wood, oil, or coal) continuously boils water in an enclosed chamber creating high-pressure steam.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD_oMl6oUISD6y0dxU3Fehd6_W5kTPwY3ZmMfRW8GcM1BfsHDXy07lUV9FDyrJNOSdOqgFKak6rSAwHrpfj9TuJnFLfCVNWvxrh8jeDX-AdtrqXg-HSrwAwdcNNpRl48UclNggTA/s1600-h/loco_1.gif"><img style="margin: 0pt 10px 10px 0pt; cursor: pointer; width: 259px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD_oMl6oUISD6y0dxU3Fehd6_W5kTPwY3ZmMfRW8GcM1BfsHDXy07lUV9FDyrJNOSdOqgFKak6rSAwHrpfj9TuJnFLfCVNWvxrh8jeDX-AdtrqXg-HSrwAwdcNNpRl48UclNggTA/s320/loco_1.gif" alt="" id="BLOGGER_PHOTO_ID_5296263525069111762" border="0" /></a><br />Steam from the boiler enters the <i>steam chest</i> and is admitted to the front end of the cylinder by the valve slide (illustrated in blue). The high pressure steam presses the piston backward, driving the engine wheels around one half turn.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5pGj9e2emWx4RETFH2SBilbk5jA662PzTGNxkDQpKe8FDAgWNJ-uLpej2Zmeg2SG1-1SSdpjNrZxtytQxY0j_N364E1viok5IW_Y8IbcUiOQKpIXXVOLIhgnFbZeFy9MK0aIC5A/s1600-h/loco_2.gif"><img style="margin: 0pt 10px 10px 0pt; cursor: pointer; width: 259px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5pGj9e2emWx4RETFH2SBilbk5jA662PzTGNxkDQpKe8FDAgWNJ-uLpej2Zmeg2SG1-1SSdpjNrZxtytQxY0j_N364E1viok5IW_Y8IbcUiOQKpIXXVOLIhgnFbZeFy9MK0aIC5A/s320/loco_2.gif" alt="" id="BLOGGER_PHOTO_ID_5296263525582269618" border="0" /></a><br />At the end of the piston stroke the valve shifts, allowing the expended steam to escape through the exhaust port (underneath the blue valve slide). The high pressure steam escapes in a quick burst giving the engine its characteristic <i>choo choo</i> sound. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjx_2Ak2O3MHI6oEaBhFNgsB505bCfVHbBlmlaEC3zzwL-G48tZH8l3WDChDfwS74gb2jO8Ilb1doqKty7yFb8wdu70THcW_1b704l5JKb7Zxf8TEkdirXPL81PAjlDty7eS8JjUA/s1600-h/loco_3.gif"><img style="margin: 0pt 10px 10px 0pt; cursor: pointer; width: 259px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjx_2Ak2O3MHI6oEaBhFNgsB505bCfVHbBlmlaEC3zzwL-G48tZH8l3WDChDfwS74gb2jO8Ilb1doqKty7yFb8wdu70THcW_1b704l5JKb7Zxf8TEkdirXPL81PAjlDty7eS8JjUA/s320/loco_3.gif" alt="" id="BLOGGER_PHOTO_ID_5296263523403295266" border="0" /></a><br />At the same time, the valve slide begins admitting high pressure steam to the back end of the cylinder. This presses the piston forward, pulling the engine wheels around another half turn. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8eHlgAXOGCukKaVgJF4_kkcqW8FAnAfgvvIq2gWSER_Sxq9Jap_wg4KPolrNtGAY11fIN875rsd_pk1X_w_68e7yEZDmcy1ySrN5_8X16HRR1eh9HJ8vGGmUtY4a5eJdHuytggQ/s1600-h/loco_4.gif"><img style="margin: 0pt 10px 10px 0pt; cursor: pointer; width: 259px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8eHlgAXOGCukKaVgJF4_kkcqW8FAnAfgvvIq2gWSER_Sxq9Jap_wg4KPolrNtGAY11fIN875rsd_pk1X_w_68e7yEZDmcy1ySrN5_8X16HRR1eh9HJ8vGGmUtY4a5eJdHuytggQ/s320/loco_4.gif" alt="" id="BLOGGER_PHOTO_ID_5296263529224016562" border="0" /></a><br />At the end of the forward stroke, the steam is released from the rear portion of the cylinder (another <i>choo</i>). <br /><br />The steam engine has a 'dead' spot at the extreme end of each stroke while the valve is transitioning from power to exhaust. For this reason, most engines had a cylinder on each side of the engine, arranged 90 degrees out of phase, so the engine could start from any position. This illustration only shows one side of the engine.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-38247875951720800072008-11-20T22:14:00.000-08:002008-11-20T22:18:16.593-08:00Jet Propulsion Part 2<span style="font-weight: bold;">Turboprop</span><br /><br />The turboprop is similar to the turbojet, except that most of the nozzle gas pressure drives the turbine shaft -- by the time the gas gets past the turbine, there's very little pressure left to create thrust.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhD4575HJ3yQMcwsHkaMnaZQdv3qDiwSg37zEdwtm2yHNB1C5_7z4XG7YX9NH1lyjW0XjMcJtoML_95Sr9dcA09peymIP2UubR0cQfbG8bTkICxYd2KeUedkhQ1faOUm-hK_QNy9g/s1600-h/tprop.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 114px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhD4575HJ3yQMcwsHkaMnaZQdv3qDiwSg37zEdwtm2yHNB1C5_7z4XG7YX9NH1lyjW0XjMcJtoML_95Sr9dcA09peymIP2UubR0cQfbG8bTkICxYd2KeUedkhQ1faOUm-hK_QNy9g/s320/tprop.gif" alt="" id="BLOGGER_PHOTO_ID_5270991016620925954" border="0" /></a>Instead, the shaft is geared to a propeller which creates the majority of the thrust. 'Jet' helicopters work the same way, except that their engines are connected to the main rotor shaft instead of a propeller.<br /><br />Turboprops are more fuel efficient than turbojets at low altitudes, where the thicker air gives a propeller a lot more 'traction.' This makes them popular on planes used for short flights, where the time spent at low altitudes represents a greater percentage of the overall flight time.<br /><br /><span style="font-weight: bold;">Turbofan</span><br /><br />The turbofan is something like a compromise between a pure turbojet and a turboprop. It works like the turbojet, except that the turbine shaft also drives an external fan, usually located at the front of the engine.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7urCr5Zchbp_YHTHCLaAU8Q6OaRQOA94a6jjlqpLNayi1ruz8S1_jp2R3yjkipKMv7_VT6p_nJ_4BbrItqUtynDB-gfe6-dJuGOWUuHu-zKiuG2qgoh13tIdAuk7GcT5V86tv0A/s1600-h/tfan.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 160px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7urCr5Zchbp_YHTHCLaAU8Q6OaRQOA94a6jjlqpLNayi1ruz8S1_jp2R3yjkipKMv7_VT6p_nJ_4BbrItqUtynDB-gfe6-dJuGOWUuHu-zKiuG2qgoh13tIdAuk7GcT5V86tv0A/s320/tfan.gif" alt="" id="BLOGGER_PHOTO_ID_5270991022357081282" border="0" /></a>The fan has more blades than a propeller and spins much faster. It also features a shroud around its perimeter, which helps to capture and focus the air flowing through it. These features enable the fan to generate some thrust at high altitudes, where a propeller would be ineffective.<br /><br />Much of the thrust still comes from the exhaust jet, but the addition of the fan makes the engine more fuel efficient than a pure turbojet. Most modern jetliners now feature turbofan engines.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com17tag:blogger.com,1999:blog-25350634.post-6048371422413702992008-11-20T19:52:00.000-08:002008-11-20T22:14:52.768-08:00Jet Propulsion Part 1<span style="font-weight: bold;">Rocket</span><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhC34W59VogeZNDvj33p6oNl32d9ETK83rrS00v5B8YcGaoWvg8Sa0Yn0U5apUl6AydtdrKlAMxv19tcErt8haUazgq2S92UY__1yUzRUFPNVPOtoGRxtfE7L1FBf4Pvw2wNqupOg/s1600-h/rocket.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 107px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhC34W59VogeZNDvj33p6oNl32d9ETK83rrS00v5B8YcGaoWvg8Sa0Yn0U5apUl6AydtdrKlAMxv19tcErt8haUazgq2S92UY__1yUzRUFPNVPOtoGRxtfE7L1FBf4Pvw2wNqupOg/s320/rocket.gif" alt="" id="BLOGGER_PHOTO_ID_5270954503665825106" border="0" /></a>The rocket engine is the simplest of this family. In order to work in outer space, rocket engines must carry their own supply of oxygen as well as fuel. The mixture is injected into the combustion chamber where it burns continuously. The high-pressure gas escapes through the nozzle, causing thrust in the opposite direction.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjI-XUKSh9rdla4jluqvuMmTLMyWkTCWgF-M1Cg1kY_7UpLyMBTcVwrYtFxwZU8BwPiSO23BRSFP8GsLpbk99ZeBJdK7Z2it3iWy_sE5XOi1i5R18XrVzK7yOVbx67WbonTFJyHeQ/s1600-h/rocket1.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 230px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjI-XUKSh9rdla4jluqvuMmTLMyWkTCWgF-M1Cg1kY_7UpLyMBTcVwrYtFxwZU8BwPiSO23BRSFP8GsLpbk99ZeBJdK7Z2it3iWy_sE5XOi1i5R18XrVzK7yOVbx67WbonTFJyHeQ/s320/rocket1.gif" alt="" id="BLOGGER_PHOTO_ID_5270954711197848146" border="0" /></a><br /><span style="font-weight: bold;">Turbojet</span><br /><br />The turbojet employs the same principle as the rocket. It burns oxygen from the atmosphere instead of carrying a supply along.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih5OSG30Y0i5pzd3ZdnxDVD4KMSlBqdGMFH7CNBnTkjv4gT4PPEqkiOiiPOCZEsWcfrayRGtvGlgbmGXZl8C8oS9Jb3qRkxOuGFtc94OAsNMNw6vCHIv1hOv_KKiXAYqmXGGP64g/s1600-h/tjet.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 118px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih5OSG30Y0i5pzd3ZdnxDVD4KMSlBqdGMFH7CNBnTkjv4gT4PPEqkiOiiPOCZEsWcfrayRGtvGlgbmGXZl8C8oS9Jb3qRkxOuGFtc94OAsNMNw6vCHIv1hOv_KKiXAYqmXGGP64g/s320/tjet.gif" alt="" id="BLOGGER_PHOTO_ID_5270988830724370338" border="0" /></a>Notice the similarities: Fuel continuously burns inside a combustion chamber just like the rocket. The expanding gasses escape out the nozzle generating thrust in the opposite direction.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVcDJLoPUC3tZBjzAtUJlxlBCqNZdPpWFXmpNA84Vb9oOpomHERM2TuML58qQ9EF-qpiKbWmi-BOTurLADtiDJKH4xLJjNzFKqdXEH0J4UuBCdIIdxfJfIJv8bIrou2Y-SyYmcfw/s1600-h/tjet1.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 240px; height: 200px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVcDJLoPUC3tZBjzAtUJlxlBCqNZdPpWFXmpNA84Vb9oOpomHERM2TuML58qQ9EF-qpiKbWmi-BOTurLADtiDJKH4xLJjNzFKqdXEH0J4UuBCdIIdxfJfIJv8bIrou2Y-SyYmcfw/s320/tjet1.gif" alt="" id="BLOGGER_PHOTO_ID_5270988836783090290" border="0" /></a>Now the differences: On its way out the nozzle, <i><b>some</b></i> of the gas pressure is used to drive a <i>turbine</i>. A turbine is a series of <i>rotors</i> or fans connected to a single shaft. Between each pair of rotors is a <i>stator</i> -- something like a stationary fan. The stators realign the gas flow to most effectively direct it toward the blades of the next rotor.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuLUE-NOCgBqjzoyQj6ujRFiNrAjjM36H9yNfguCPuALP-VaU3215nQT8V9fWFMbiABO0l6ZXyux1_BkciTD49E5BPqeiRpuNDyjrf10mmlqikM7KYtWM1mJs5bE4x7P1DufLaeA/s1600-h/tjet2.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 240px; height: 200px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuLUE-NOCgBqjzoyQj6ujRFiNrAjjM36H9yNfguCPuALP-VaU3215nQT8V9fWFMbiABO0l6ZXyux1_BkciTD49E5BPqeiRpuNDyjrf10mmlqikM7KYtWM1mJs5bE4x7P1DufLaeA/s320/tjet2.gif" alt="" id="BLOGGER_PHOTO_ID_5270988835635951234" border="0" /></a>At the front of the engine, the turbine shaft drives a <i>compressor</i>. The compressor works a lot like the turbine only in reverse. Its purpose is to draw air into the engine and pressurize it.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRTXDuPVWOqqqxNTDEG09R9Mw7XIuGSKRYxt2EZnuUd6Ik6Og3iWS1CAmXqZxqVg1Y4rRSWj2otZb97-kXhJnyn4rVnyks-EPF3rD9PsPh-tUy9UY3iC1mlT9_5_7YGU4nUKAW9g/s1600-h/tjet3.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 240px; height: 200px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRTXDuPVWOqqqxNTDEG09R9Mw7XIuGSKRYxt2EZnuUd6Ik6Og3iWS1CAmXqZxqVg1Y4rRSWj2otZb97-kXhJnyn4rVnyks-EPF3rD9PsPh-tUy9UY3iC1mlT9_5_7YGU4nUKAW9g/s320/tjet3.gif" alt="" id="BLOGGER_PHOTO_ID_5270988836198189298" border="0" /></a>Turbojet engines are most efficient at high altitudes, where the thin air renders propellers almost useless.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-15199794900646910202008-11-20T19:44:00.000-08:002008-11-20T19:50:25.723-08:00GnomeThe Gnome was one of several <i> rotary engines</i> popular on fighter planes during World War I. In this type of engine, the crankshaft is mounted on the airplane, while the crankcase and cylinders rotate with the propeller.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBvwyzgX-FTnEGgu0UTUTGzJLFRE1CaDe4YD4SKz6ETN5wzs3cA75RY8HmQUqWYWTnKZFpakOT0WzM9BUE_o6QoVdIvYyR-r59A48JpyNo7v1jf5uUyMCua65tzgFCfd9_LLHujQ/s1600-h/gnome.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBvwyzgX-FTnEGgu0UTUTGzJLFRE1CaDe4YD4SKz6ETN5wzs3cA75RY8HmQUqWYWTnKZFpakOT0WzM9BUE_o6QoVdIvYyR-r59A48JpyNo7v1jf5uUyMCua65tzgFCfd9_LLHujQ/s320/gnome.gif" alt="" id="BLOGGER_PHOTO_ID_5270952995326612882" border="0" /></a>The Gnome was unique in that the intake valves were located within the pistons. Otherwise, this engine used the familiar Otto four stroke cycle. At any given point, each of the cylinders is in a different phase of the cycle. In the following discussion, follow the <i>master</i> cylinder with the green connecting rod.<br /><br />During this portion of the stroke, a vacuum forms in the cylinder, forcing the intake valve open and drawing the fuel-air mixture in from the crankcase.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJWNKp0gF6VI64-Zty_MOza4vISlXIHnwsRLfuFyICgMqhfiUOw3ueTCnNQhysHdTaoDgEuo1VDCRkZNrgOmULyJ07h1ie68r55r8GkemXdlPOk-ZGMB7F-Z0J31-vwrpr7jy0Hg/s1600-h/Gnome_intake.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 295px; height: 294px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJWNKp0gF6VI64-Zty_MOza4vISlXIHnwsRLfuFyICgMqhfiUOw3ueTCnNQhysHdTaoDgEuo1VDCRkZNrgOmULyJ07h1ie68r55r8GkemXdlPOk-ZGMB7F-Z0J31-vwrpr7jy0Hg/s320/Gnome_intake.gif" alt="" id="BLOGGER_PHOTO_ID_5270952330382609074" border="0" /></a>The mixture is compressed during this phase. The spark plug fires toward the end of the compression stroke, slightly before <i>top dead center.<br /></i><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHubJAf3Sqka4J5rmu86CF9QTHcCfWXhi4RPUyniHGaRBw05nGkaYhkJYMbYKgWp9oPO_Lc_VsDwUxn76rAydvKS5fOjfjFnmwNJymmhDUQwx-UW4vaMrslQ04TTp24yR9BqfCNg/s1600-h/Gnome_compression.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 295px; height: 294px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHubJAf3Sqka4J5rmu86CF9QTHcCfWXhi4RPUyniHGaRBw05nGkaYhkJYMbYKgWp9oPO_Lc_VsDwUxn76rAydvKS5fOjfjFnmwNJymmhDUQwx-UW4vaMrslQ04TTp24yR9BqfCNg/s320/Gnome_compression.gif" alt="" id="BLOGGER_PHOTO_ID_5270952330133512082" border="0" /></a>The power stroke happens here. Note that the exhaust valve opens early -- well before <i>bottom dead center.</i><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh05PWo4xXhTyHjrRn_mG2Uht0T0EX9kwgVFMnjwjbfpquYZzhSLX2wfxXtRLYYX5r6M7ScKuIUqmbdeo5onoJrioIXA9o9WmkCMf9kJ0fVSxER2ZwfyT0qRsqgN-Os6JPboVqPxQ/s1600-h/Gnome_power.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 295px; height: 294px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh05PWo4xXhTyHjrRn_mG2Uht0T0EX9kwgVFMnjwjbfpquYZzhSLX2wfxXtRLYYX5r6M7ScKuIUqmbdeo5onoJrioIXA9o9WmkCMf9kJ0fVSxER2ZwfyT0qRsqgN-Os6JPboVqPxQ/s320/Gnome_power.gif" alt="" id="BLOGGER_PHOTO_ID_5270952333026826610" border="0" /></a>This engine has a fairly long exhaust stroke. In order to improve power or efficiency, engine valve timing often varies from what one might expect.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbiS33vk_LAe_iigKYdRejbMtuothKayO5pX4FYbEznB1LjRYygdVFueJUK2FM4DNaPIqzcKbzypCaInOBEjcOpccwH26nF8Q5hPKYNjw1eyUAat9c-tbeDqaVLy4sCFX2x-vsdw/s1600-h/Gnome_exhaust.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 295px; height: 294px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbiS33vk_LAe_iigKYdRejbMtuothKayO5pX4FYbEznB1LjRYygdVFueJUK2FM4DNaPIqzcKbzypCaInOBEjcOpccwH26nF8Q5hPKYNjw1eyUAat9c-tbeDqaVLy4sCFX2x-vsdw/s320/Gnome_exhaust.gif" alt="" id="BLOGGER_PHOTO_ID_5270952334273339202" border="0" /></a>When I first learned how these engines worked, I thought the only person crazier than the engine designer was the one who paid money for it. At first glance it seems ridiculously <i>backwards</i>. <p>Nonetheless, a number of engines were designed this way, including the <i> Gnome, Gnome Monosoupape, LeRhone, Clerget,</i> and <i> Bentley</i> to name a few. It turns out there were some good reasons for the configuration:</p> <table border="0"><tbody><tr> <td colspan="2"><br /></td> </tr> <tr> <td width="50"><br /></td> <td> <p><b>Balance.</b> Note that the crankcase and cylinders revolve in one circle, while the pistons revolve in another, offset circle. Relative to the engine mounting point, there are no reciprocating parts. This means there's no need for a heavy counterbalance.</p> <p><b>Air Cooling.</b> Keeping an engine cool was an ongoing challenge for early engine designers. Many resorted to heavy water cooling systems. Air cooling was quite adequate on rotary engines, since the cylinders are always in motion.</p> <p><b>No flywheel.</b> The crankcase and cylinders provided more than adequate momentum to smooth out the power pulses, eliminating the need for a heavy flywheel.</p> </td> </tr> <tr> <td colspan="2" height="15"><br /></td> </tr> <tr> <td colspan="2" height="40"><p>All these factors gave rotary engines the best power-to-weight ratio of any configuration at the time, making them ideal for use in fighter planes. Of course, there were disadvantages as well:</p> </td> </tr> <tr> <td colspan="2" height="15"><br /></td> </tr> <tr> <td width="50"><br /></td> <td> <p><b>Gyroscopic effect.</b> A heavy spinning object resists efforts to disturb its orientation (A toy gyroscope demonstrates the effect nicely). This made the aircraft difficult to maneuver.</p> <p><b><i>Total Loss</i> Oil system.</b> Centrifugal force throws lubricating oil out after its first trip through the engine. It was usually castor oil that could be readily combined with the fuel. (The romantic-looking scarf the pilot wore was actually a towel used to wipe the slimy stuff off his goggles!) </p> <p>The aircraft's range was thus limited by the amount of oil it could carry as well as fuel. Most conventional engines continuously re-circulate a relatively small supply of oil.</p></td></tr></tbody></table>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-54307121782175049312008-11-20T19:38:00.000-08:002008-11-20T19:43:54.644-08:00Atkinson EngineThe Atkinson engine is essentially an Otto-cycle engine with a different means of linking the piston to the crankshaft. It was originally designed to compete with the Otto engine, but without infringing on any of Otto's patents.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ-GmfMwPEtqN4cfbxpGqxLAQ7x350-sUVFgC0IF8x8yJJybVZTddoPmbYE1cpU2XKNWeav_wKlbMAjy17kZ50C75Ux2_AC618u2LhlwahEJ9sBMs9lQ_5bPeMvQZzyOMuRj_JRQ/s1600-h/atkinson.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 281px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ-GmfMwPEtqN4cfbxpGqxLAQ7x350-sUVFgC0IF8x8yJJybVZTddoPmbYE1cpU2XKNWeav_wKlbMAjy17kZ50C75Ux2_AC618u2LhlwahEJ9sBMs9lQ_5bPeMvQZzyOMuRj_JRQ/s320/atkinson.gif" alt="" id="BLOGGER_PHOTO_ID_5270951375382500722" border="0" /></a>The clever arrangement of levers allows the Atkinson to cycle the piston through all four strokes in only one revolution of the main crankshaft, and allows the strokes to be different lengths -- the intake and exhaust strokes are longer than the compression and power strokes (In this illustration... see below).<br /><br />This also obviates the need for a separate cam shaft. The intake (if used), exhaust, and ignition cams are located on the main crank shaft. My illustration shows only an exhaust cam.<br /><br />Everything I know about the Atkinson engine came out of Building the Atkinson cycle Engine. This illustration draws heavily from that excellent book.<span style="font-weight: bold;"></span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-8546651737369196572008-11-20T09:57:00.000-08:002008-11-20T10:01:42.192-08:00Wankel EngineThe Wankel radial engine is a fascinating beast that features a very clever rearrangment of the four elements of the Otto cycle. It was developed by Felix Wankel in the 1950s.<sup>1</sup><br /><br />In the Wankel a triangular rotor incorporating a central ring gear is driven around a fixed pinion within an oblong chamber.<br /><br />The fuel/air mixture is drawn in the intake port during this phase of the rotation.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcPv7xWPJCK2b6mVv0enIyz4fC4eetVNf46d-j2DBakU-KvmdzspPXd0HaLPsmtbCyciRCyCxbDBI4VL6LCvVwtACMW2_zo8MjF7XZzI1Vdz8aoQGfU_ClUNlosPDxVa010hEOnw/s1600-h/wankel_in.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 298px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcPv7xWPJCK2b6mVv0enIyz4fC4eetVNf46d-j2DBakU-KvmdzspPXd0HaLPsmtbCyciRCyCxbDBI4VL6LCvVwtACMW2_zo8MjF7XZzI1Vdz8aoQGfU_ClUNlosPDxVa010hEOnw/s320/wankel_in.gif" alt="" id="BLOGGER_PHOTO_ID_5270800996084587090" border="0" /></a>The mixture is compressed here.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJuu1nRW6sKDIPusRLJZqRWsqAq3JQXZnsJVZbew7-OcoUtpojhyphenhypheni-57A-8b-MGJuVFrgikrKqq68BVdav8Q-ucrsCZ6CsK1l4Zd8DT_QUw5fdDxfahswRMbez8E1UFLVH3KxQ2A/s1600-h/wankel_cmp.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 298px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJuu1nRW6sKDIPusRLJZqRWsqAq3JQXZnsJVZbew7-OcoUtpojhyphenhypheni-57A-8b-MGJuVFrgikrKqq68BVdav8Q-ucrsCZ6CsK1l4Zd8DT_QUw5fdDxfahswRMbez8E1UFLVH3KxQ2A/s320/wankel_cmp.gif" alt="" id="BLOGGER_PHOTO_ID_5270800996913536034" border="0" /></a>The mixture burns here, driving the rotor around.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpgF7D3JJXX29XmBqdH46qmS2nsvkkFYwu_UT9pSt1OdTZkvAMzp4p0LAtM7R8toVbThcNA3N2Fl39q-oYYRUcD8s6FLwd77_lLAz0VW2mByss_87-IncqVxce7tG61B1JYq2gyA/s1600-h/wankel_pwr.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 298px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpgF7D3JJXX29XmBqdH46qmS2nsvkkFYwu_UT9pSt1OdTZkvAMzp4p0LAtM7R8toVbThcNA3N2Fl39q-oYYRUcD8s6FLwd77_lLAz0VW2mByss_87-IncqVxce7tG61B1JYq2gyA/s320/wankel_pwr.gif" alt="" id="BLOGGER_PHOTO_ID_5270801002390760898" border="0" /></a>And the exhaust is expelled here.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjshDMshdfwQxMjbIHlNM-b1m-Ya2RmoBf_zogXwgi2PMGoJduvwSpGvyEVBu8Ln0f-qAG8K2FcJz_cO9vzyudixdyC4YZHGp4UkkAax_ubMXmu4w3p07QwwbpMxZ5r5OySX2Lzcw/s1600-h/wankel_exh.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 298px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjshDMshdfwQxMjbIHlNM-b1m-Ya2RmoBf_zogXwgi2PMGoJduvwSpGvyEVBu8Ln0f-qAG8K2FcJz_cO9vzyudixdyC4YZHGp4UkkAax_ubMXmu4w3p07QwwbpMxZ5r5OySX2Lzcw/s320/wankel_exh.gif" alt="" id="BLOGGER_PHOTO_ID_5270801001877631618" border="0" /></a>The rotory motion is transferred to the drive shaft via an eccentric wheel (illustrated in blue) that rides in a matching bearing in the rotor. The drive shaft rotates once during every power stroke instead of twice as in the Otto cycle. <p>The Wankel promised higher power output with fewer moving parts than the Otto cycle engine, however technical difficulties have apparently interfered with widespread adoption. In spite of valiant efforts by Mazda, the four stroke engine remains much more popular.</p>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-20475465178892775812008-11-20T09:50:00.000-08:002008-11-20T09:55:51.673-08:00Two Stroke EngineThe two stroke engine employs the crankcase as well as the cylinder to achieve all the elements of the Otto cycle in only two strokes of the piston.<br /><br /><b>Intake.</b> The fuel/air mixture is first drawn into the crankcase by the vacuum created during the upward stroke of the piston. The illustrated engine features a poppet intake valve, however many engines use a rotary value incorporated into the crankshaft.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6ms7fvfHxIOd_OCWsUjygnbxfaBBX0xl1VZBdCZR8aT21Q-q8xcwi59xUAsR_BJ42GeRn-iJUmrt9ICXr2t9icSiu1Rt57Ijty2ae-u98OyCGBvWkE0ZXZe3BFavAwpTSt2LZVg/s1600-h/twos_in.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6ms7fvfHxIOd_OCWsUjygnbxfaBBX0xl1VZBdCZR8aT21Q-q8xcwi59xUAsR_BJ42GeRn-iJUmrt9ICXr2t9icSiu1Rt57Ijty2ae-u98OyCGBvWkE0ZXZe3BFavAwpTSt2LZVg/s320/twos_in.gif" alt="" id="BLOGGER_PHOTO_ID_5270799306608511458" border="0" /></a>During the downward stroke the poppet valve is forced closed by the increased crankcase pressure. The fuel mixture is then compressed in the crankcase during the remainder of the stroke.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimzQC0vCfdJXK9jJo9LdlrYlMZOnLdXKs7RjLbufyYZ_gSMfTrBEhENLzbRT4KPR52T9MM4ZeC5gSwAuvE_qinnQuHNN7liztRtDz-Za0nWROEIRsa9awu6jljBs2wqPvTzpnpqA/s1600-h/twos_cmpC.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimzQC0vCfdJXK9jJo9LdlrYlMZOnLdXKs7RjLbufyYZ_gSMfTrBEhENLzbRT4KPR52T9MM4ZeC5gSwAuvE_qinnQuHNN7liztRtDz-Za0nWROEIRsa9awu6jljBs2wqPvTzpnpqA/s320/twos_cmpC.gif" alt="" id="BLOGGER_PHOTO_ID_5270799313722284434" border="0" /></a><b>Transfer/Exhaust.</b> Toward the end of the stroke, the piston exposes the intake port, allowing the compressed fuel/air mixture in the crankcase to escape around the piston into the main cylinder. This expels the exhaust gasses out the exhaust port, usually located on the opposite side of the cylinder. Unfortunately, some of the fresh fuel mixture is usually expelled as well.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9sfTBfgaeHZhBZB_VciSYGM4j99_NhyW48xwoxkZh9_RnWMhn7vhs9dOxOdoAQYrXdH-KMPqDbJ1j3Y9NlAYLjj3w1sFVmGY4c6ksjNbhjLqYcxAnFrJmicRtxvfJCu-sE0fS2g/s1600-h/twos_xfer.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9sfTBfgaeHZhBZB_VciSYGM4j99_NhyW48xwoxkZh9_RnWMhn7vhs9dOxOdoAQYrXdH-KMPqDbJ1j3Y9NlAYLjj3w1sFVmGY4c6ksjNbhjLqYcxAnFrJmicRtxvfJCu-sE0fS2g/s320/twos_xfer.gif" alt="" id="BLOGGER_PHOTO_ID_5270799314922845970" border="0" /></a><b>Compression.</b> The piston then rises, driven by flywheel momentum, and compresses the fuel mixture. (At the same time, another intake stroke is happening beneath the piston).<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgah3otrfljF8wnMvcpL32QlEkcysso-3HjOTugDUMBqcCZYQfWPpCUwEk8c-lV8xbMYL1z0C7fH-k14wb-tRqsCD__dgmDFYnufML_gce8Y8GLr91C2FPUqURpx5fF5EQ31M-xCw/s1600-h/twos_cmp.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgah3otrfljF8wnMvcpL32QlEkcysso-3HjOTugDUMBqcCZYQfWPpCUwEk8c-lV8xbMYL1z0C7fH-k14wb-tRqsCD__dgmDFYnufML_gce8Y8GLr91C2FPUqURpx5fF5EQ31M-xCw/s320/twos_cmp.gif" alt="" id="BLOGGER_PHOTO_ID_5270799308278876482" border="0" /></a><br /><b>Power.</b> At the top of the stroke the spark plug ignites the fuel mixture. The burning fuel expands, driving the piston downward, to complete the cycle.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjI0jwhmIp8XZcVTHfk3J4NP_FxgUXiMV-FHF4rwTXHF9skyoyU7pF6m4ZRXzIov7U_asHU_V7Ewp4K1hpcBrzwLrjXpIzNbJxjypj2SVTcYs9YXiHAl4He-PbOOnCfMX-ULabVGg/s1600-h/twos_pwr.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 230px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjI0jwhmIp8XZcVTHfk3J4NP_FxgUXiMV-FHF4rwTXHF9skyoyU7pF6m4ZRXzIov7U_asHU_V7Ewp4K1hpcBrzwLrjXpIzNbJxjypj2SVTcYs9YXiHAl4He-PbOOnCfMX-ULabVGg/s320/twos_pwr.gif" alt="" id="BLOGGER_PHOTO_ID_5270799316433117970" border="0" /></a>Since the two stroke engine fires on every revolution of the crankshaft, a two stroke engine is usually more powerful than a four stroke engine of equivalent size. This, coupled with their lighter, simpler construction, makes two stroke engines popular in chainsaws, line trimmers, outboard motors, snowmobiles, jet-skis, light motorcycles, and model airplanes. Unfortunately most two stroke engines are inefficient and are terrible polluters due to the amount of unspent fuel that escapes through the exhaust port.Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-10070684999509091822008-11-20T09:39:00.000-08:002008-11-20T09:48:39.587-08:00Four Stroke EngineThe four stroke engine was first demonstrated by Nikolaus Otto in 1876<sup><a href="http://www.keveney.com/bibliography.html">1</a></sup>, hence it is also known as the <i>Otto cycle</i>. The technically correct term is actually <i>four stroke cycle</i>. The four stroke engine is probably the most common engine type nowadays. It powers almost all cars and trucks.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7IA3PiNKWP5NkerF3ek2JJc-8akVTUZlzs5agbNwyfDhCG6Q7QhF0DjvF6lgKuJgASfPCEBspI6G0bxTbFTI8E82KEwA4nuv5yCMCp47gLz77oZOTK8IvKAekQu5Reaid5qai4Q/s1600-h/otto.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 200px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7IA3PiNKWP5NkerF3ek2JJc-8akVTUZlzs5agbNwyfDhCG6Q7QhF0DjvF6lgKuJgASfPCEBspI6G0bxTbFTI8E82KEwA4nuv5yCMCp47gLz77oZOTK8IvKAekQu5Reaid5qai4Q/s320/otto.gif" alt="" id="BLOGGER_PHOTO_ID_5270797053511178546" border="0" /></a><br /><br />The four strokes of the cycle are intake, compression, power, and exhaust. Each corresponds to one full stroke of the piston, therefore the complete cycle requires two revolutions of the crankshaft to complete.<br /><br /><b>Intake. </b>During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a 'poppet' intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way, however most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring (not illustrated here).<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgilIvJ-VfxsIyzOEVJ_v5SlKPN-CYdK-xdo1D3OHJitEU03RZ3Psf5wU_7jhm17YN3XwuHDlMN9_pZbABnfqg-05e2C79zcF-Fvdh2y4OLOcIMXq8L0UAUILQc2NuK6TTgJD8wpA/s1600-h/otto_in.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 186px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgilIvJ-VfxsIyzOEVJ_v5SlKPN-CYdK-xdo1D3OHJitEU03RZ3Psf5wU_7jhm17YN3XwuHDlMN9_pZbABnfqg-05e2C79zcF-Fvdh2y4OLOcIMXq8L0UAUILQc2NuK6TTgJD8wpA/s320/otto_in.gif" alt="" id="BLOGGER_PHOTO_ID_5270797612287284418" border="0" /></a><b>Compression.</b> As the piston rises the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCz1csSbwP2em5UW92ggr-8WQZK3B1vfL06NkwuPALGM5G-3FioZaR2a3CECbTzz2vi7tkVQR-NDgjFhGQtFNrShmxrgRt11cW7J-xPkwXzHQuCZWig4HAIcUHGl1pbECO38QUNA/s1600-h/otto_cmp.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 186px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCz1csSbwP2em5UW92ggr-8WQZK3B1vfL06NkwuPALGM5G-3FioZaR2a3CECbTzz2vi7tkVQR-NDgjFhGQtFNrShmxrgRt11cW7J-xPkwXzHQuCZWig4HAIcUHGl1pbECO38QUNA/s320/otto_cmp.gif" alt="" id="BLOGGER_PHOTO_ID_5270797620957801794" border="0" /></a><b>Power.</b> At the top of the compression stroke the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjiTq-o5xRCYzFainmwvdcfGjPbpsdLaMVXpBHBnNyav2D8dsoQ7vyoHOmWGIQci1est4FxZb1IwZSFLEOxEsVsP4cdhRmQ9TOKlXzQD2wYZfFFb1b0H0gUXh6MDUhWnw4AImjKwg/s1600-h/otto_pwr.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 186px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjiTq-o5xRCYzFainmwvdcfGjPbpsdLaMVXpBHBnNyav2D8dsoQ7vyoHOmWGIQci1est4FxZb1IwZSFLEOxEsVsP4cdhRmQ9TOKlXzQD2wYZfFFb1b0H0gUXh6MDUhWnw4AImjKwg/s320/otto_pwr.gif" alt="" id="BLOGGER_PHOTO_ID_5270797625091173170" border="0" /></a><b>Exhaust.</b> At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6kGfV9fcfGqYZ9TWx14k9fk3J1X9osIBHdCwsXXC234Ly-EWj-M0K06VYHwRDIJ5fdGit2CNOycyTEvsi-gJFuAAka8eYEMlCyRI3Jq0JoKRNNLFLOLqUGTv-H30OJZkH_giOaQ/s1600-h/Otto_exh.gif"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 186px; height: 298px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6kGfV9fcfGqYZ9TWx14k9fk3J1X9osIBHdCwsXXC234Ly-EWj-M0K06VYHwRDIJ5fdGit2CNOycyTEvsi-gJFuAAka8eYEMlCyRI3Jq0JoKRNNLFLOLqUGTv-H30OJZkH_giOaQ/s320/Otto_exh.gif" alt="" id="BLOGGER_PHOTO_ID_5270797628536031698" border="0" /></a>This animation also illustrates a simple ignition system using breaker points, coil, condenser, and battery. <p>Larger four stroke engines usually include more than one cylinder, have various arrangements for the camshaft (dual, overhead, etc.), sometimes feature fuel injection, turbochargers, multiple valves, etc. None of these enhancements changes the basic operation of the engine.</p>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-41136475493670066862008-05-06T10:08:00.000-07:002008-05-06T10:09:22.190-07:00SIKLUS MESIN 4-TAK (Bagian Sepuluh)<span class="postbody"><span style="font-weight: bold;">RELASI EFISIENSI TERMAL DAN RASIO KOMPRESI</span><br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeenginerun-ani.gif" border="0" /><br /><br />Merujuk kpd uraian sebelumnya diatas, krn<br /><br />TE = [1 - (T4 - T1) / (T3 - T2)] x 100%<br /><br />dan<br /><br />CR = V2 / V1 = (T3 - T2) / (T4 - T1)<br /><br />shg<br /><br />TE = (1 - 1 / CR) x 100%<br /><br /><br />Seluruh formulasi dan kalkulasi diatas menggunakan aproksimasi ideal dimana panas jenis (spesific heat) dianggap bernilai smdgn 2.<br /><br />Jika, panas jenis diperhitungkan, maka formula efisiensi termal real menjadi<br /><br />TE = [1 - 1 / CR^(h-1)] x 100%<br /><br />dimana h adalah panas jenis gas campuran udara dan bahanbakar, yg mana utk nilai h = 2,<br /><br />TE = (1 - 1 / CR) x 100%<br /><br />Jika CR = 9 dan h = 1,5 [utk udara, nilai h mendekati 1,4], maka<br /><br />TEi = (1 - 1 / 9) x 100% = 0,889 x 100% = 88,9%<br />TEr = [1 - 1 / [9^(1,5 - 1)]] x 100% = (1 - 1 / 9^0,5) x 100% = (1 - 1/3) x 100% = (1 - 0,333) x 100% = 0,666 x 100% = 66,6%<br /><br />Rasio kompresi mesin Suzuki Thunder, berdasarkan data spesifikasi teknik, adalah 9,2, berarti efisiensi termal mesin Suzuki Thunder adalah<br /><br />TEi = (1 - 1/9,2) x 100% = 0,891 x 100% = 89,1%<br />TEr = [1 - 1 / [9.2^(1,5 - 1)]] x 100% = (1 - 1 / 9.2^0,5) x 100% = (1 - 1/3,033) x 100% = (1 - 0,33) = 0,67 x 100% = 67%<br /><br />Kembali pd pernyataan pertama diatas bahwa hampir seluruh kalkulasi diatas menggunakan aproksimasi ideal, namun dlm kenyataan, pd mesin pembakaran dalam 4-tak dgn bahanbakar bensin, banyak faktor lain mesin yg mempengaruhi keseluruhan proses, shg menurunkan efisiesi termal mesin, al.<br /><br />* 1. dinding silinder adalah bukan metal ideal, shg ada tenaga panas hilang krn penyerapan panas oleh metal dinding silinder.<br />* 2. gesekan|friksi antara bagian2 mesin tdk nol krn mesin menggunakan oli | minyak pelumas bukan ideal shg tak ada tenaga gerak hilang utk mengatasi gesekan.<br />* 3. udara yg memasuki silinder mesin, tak berlaku sbg gas ideal yg memiliki kapasitas panas tetap, dimana panas jenis (specific heat) 1,4, dan dimana gas campuran udara dan bahanbakar dlm silinder mengalami turbulensi|gejolak.<br />* 4. mesin, dlm prakteknya, tak selalu dlm status "idle", tanpa beban, kendaraan tak diam alias bergerak, shg ada akselerasi|percepatan dan dekselerasi|perlambatan dlm gerak mesin, shg seluruh proses adalah tak "quasi-static" alias berlangsung dgn perubahan labil.<br /><br /><br /><br />Jadi, dlm praktek, secara teknis, mesin dgn efisiensi antara 60% s/d 70% sdh dianggap cukup efisien, atau memiliki efisiensi normal.<br /><br />Efisiensi termal mesin dpt ditingkatkan dgn bbrp cara,al.<br /><br /> * 1. meningkatkan rasio kompresi antara 9 dan 10 [hrs turun mesin].<br />* 2. meningkatkan suhu penyalaan dan pembakaran via peningkatan tegangan elektroda busi, dgn cara menambahkan SPB (spark-plug booster) antara koil dan busi, dan mengganti busi dgn yg lbh tahan panas.<br />* 3. meniadakan endapan kerak arang|karbon dlm ruang silinder mesin, dgn cara meningkatkan pembakaran menjadi lbh sempurna, al via cara 2.<br /> * 4. melapisi permukaan metal mesin dgn bahan gel anti-friksi [minimasi friksi].<br />* 5. meningkatkan nilai kekentaan|viskositas oli | minyak pelumas, dgn mengganti pelumas dgn yg memiliki viskositas lbh kental pd suhu tinggi.<br />* 6. meningkatkan nilai oktan bahanbakar, shg tak terjadi pembakaran dini (pre-ignition) yg menimbulkan letupan (detonation) dan ketukan (knocking) pd mesin,<br /> dgn cara mengganti bahanbakar dgn yg memiliki nilai oktan lbih tinggi [tapi tentu dgn harga lbh mahal].<br />* 7. melumasi dgn baik seluruh bagian bergerak | mekanisme kendaraan, dan memelihara agar tekanan angin ban selalu pd ukuran tepat [ini juga minimasi friksi].</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-6372833689882929022008-05-06T10:07:00.000-07:002008-05-06T10:23:44.565-07:00SIKLUS MESIN 4-TAK (Bagian Sembilan)<span class="postbody"><span style="font-weight: bold;">FORMULASI DAN KALKULASI RASIO KOMPRESI MESIN</span><br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeenginerun-ani.gif" border="0" /><br /><br />Merujuk kpd uraian sebelumnya diatas, dari relasi 6 fase termodinamik siklus Otto mesin 4-tak diatas, diperoleh bahwa<br /><br />V2 / V1 = T2 / T1 = T3 / T4<br /><br />dan juga bisa diperoleh bahwa<br /><br />(T2 - T1) / T2 = (T3 - T4) / T3<br /><br />atau<br /><br />1 - T1/T2 = 1 - T4/T3<br /><br />Nilai perbandingan V2 / V1 adalah rasio ekspansi|pemuaian (expansion ratio, XR, Rx) atau rasio kompresi|pemampatan (compression ratio, CR, Rc) isentropik volume silinder.<br /><br />Berdasarkan dua relasi diatas diperoleh bahwa<br /><br />CR = V2 / V1 = (T3 - T2) / (T4 - T1)<br /><br />Dgn kata lain, rasio ekspansi atau rasio kompresi isentropik volume silinder adalah perbandingan volume total silinder dan volume kamar bakar (combustion chamber}, yg mana setara dgn perbandingan beda suhu pemampatan dan beda suhu pembuangan.<br /><br />Utk lbh jelas, silahkan lihat kembali ilustrasi dlm diagram PVT.<br /><br /><img style="width: 409px; height: 306px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />Dlm kenyataan, pd mesin pembakaran dalam 4-tak dgn bahanbakar bensin, rasio kompresi tak dapat dibuat lbh besar drpd 10, krn jika rasio kompresi lbh besar drpd 10, maka peningkatan suhu dlm proses kompresi gas campuran udara dan bahanbakar akan dpt memanaskan dan membakar gas tsb sebelum gas tsb dibakar oleh percikan listrik busi, shg menimbulkan penyalaan dini (premature ignition) atau pra-penyalaan (pre-ignition) shg terjadi letupan (detonation) yg menimbulkan suara ketukan (knocking) dan gelitik (pinking) pd mesin.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-18648654279088592522008-05-06T10:06:00.002-07:002008-05-06T10:16:16.227-07:00SIKLUS MESIN 4-TAK (Bagian Delapan)<span class="postbody"><span style="font-weight: bold;">FORMULASI DAN KALKULASI EFISIENSI TERMAL VIA BEDA TEMPERATUR</span><br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeenginerun-ani.gif" border="0" /><br /><br />Merujuk kpd uraian sebelumnya diatas, aliran tenaga panas masukan|input Q1 berlangsung selama proses pemanasan dan penyalaan dan pembakaran dalam garis T2-T3 dan tenaga panas keluaran|output Q2 berlangsung selama proses pendinginan dan pembuangan T4-T1.<br /><br />Relasi termodinamik menunjukkan bahwa kuantitas tenaga panas Q1 dan Q2 memiliki hubungan langsung dengan suhu panas T2 dan T3 dan T4 dan T1, dimana kuantitas tenaga panas masukan|input Q1 dgn perubahan suhu pemanasan T2 dan T3, dan kuantitas tenaga panas keluaran|output Q2 dgn perubahan suhu pendingan T4 dan T1.<br /><br />Proses pemasukan|pengambilan gas campuran bahanbakar dan udara dlm garis T0-T1, dan proses pengeluaran|pembuangan sisa gas pembakaran dlm garis T1-T0, bukan merupakan sistem tertutup termodinamik (thermodynamic closed system), tp sistem terbuka termodinamik (thermodynamic open system), shg bukan merupakan bagian inti dr konversi energi dlm siklus Otto yg merupakan sistem tertutup termodinamik. Dua proses ini mengambil tenaga|energi mesin shg mengurangi efisiensi.<br /><br /><br />Relasi termodinamik menunjukkan bahwa efisiensi termal (thermal efficiency TE, Et) siklus Otto dlm sistem ini adalah, persentasi perbandingan kuantitas tenaga mekanik keluaran (mechanical energy quantity output) dan kuantitas tenaga panas masukan (heat energy quantity input), yg bila dijabarkan secara matematik fisika adalah sbb.<br /><br />TE = W / Q1 x 100% = [(Q1 - Q2) / Q2] x 100% = [1 - Q2 / Q1] x 100%<br /><br />dimana jika W = Q1 atau Q2 = 0, maka efisiensi 100%.<br /><br />Jika dinyatakan hubungan dalam suhu, maka<br /><br />TE = [1 - (T4 - T1) / (T3 - T2)] x 100%<br /><br />shg efisiensi termal setara dgn persentasi satu dikurangi perbandingan beda suhu pembuangan dan beda suhu pemampatan.<br /><br />Tp ini adalah formula aproksimasi gas ideal. Utk gas real berlaku formula sbb.<br /><br />TE = [1 - [(T4 - T1) / (T3 - T2)]^(h-1)] x 100%<br /><br />dimana h adalah panas jenis gas campuran udara dan bahanbakar, yg mana utk nilah h = 2,<br /><br />TE = [1 - (T4 - T1) / (T3 - T2)] x 100%<br /><br /><img style="width: 385px; height: 288px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />Sbg contoh, suhu pemasukan gas campuran bahanbakar dan udara T1 adalah sekitar 25 derajat, kemudian memanas selama kompresi menjadi T2 sekitar 230 C. Lalu ketika penyalaan dan pembakaran memanas menjadi T3 sekitar 644 C, dan kemudian mendingin selama pengeluaran menjadi T4 sekitar 70 C, sampai akhirnya kembali mencapai T1 sekitar 25 C.<br /><br />Jadi, krn,<br /><br />T1 = 25<br />T2 = 230<br />T3 = 644<br />T4 = 70<br /><br />TEi = [1 - (70 - 25) / (644 - 230)] x 100% = [1 - 45 / 414] x 100% = [1 - 0,109] x 100% = 0,891 x 100% = 89,1%<br />TEr = [1 - [(70 - 25) / (644 - 230)]^0,5] x 100% = [1 - (45 / 414)^0,5] x 100% = [1 - 0,33] x 100% = 0,67 x 100% = 67%<br /><br />dimana,<br /><br />TEi = efisiensi termal ideal<br />TEr = efisiensi termal real</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-69346308575665891132008-05-06T10:06:00.001-07:002008-05-06T10:12:47.411-07:00SIKLUS MESIN 4-TAK (Bagian Tujuh)<span class="postbody"><span style="font-weight: bold;">DISKUSI, FORMULASI DAN KALKULASI TERMODINAMIK</span><br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeengine-ani.gif" border="0" /><br /><br />Merujuk kpd uraian sebelumnya diatas, sepasang proses isobarik T0-T1 dan T1-T0 adalah setara dan berlawanan arah, positiv dab negativ, shg secara matematik saling membatalkan satu thdp yg lain, alias hasilnya nol, shg tak perlu dilibatkan dlm perhitungan lbh lanjut. Sisanya adalah 4 proses pasangan adiabatik dan isokorik, namun hanya pasangan proses isokorik yg melibatkan penyerapan dan pelepasan tenaga panas, yakni penyerapan kuantitas tenaga panas Q1 antara T2-T3 dan pelepasan kuantitas tenaga panas Q2 antara T2-T1. Aliran panas (heat flow, heat transfer) sbg tenaga (energy) inilah yg menjadi obyek termodinamika.<br /><br />Dengan asumsi bahwa kapasitas|tampungan panas adalah tetap (constant) sepanjang garis T2-T3, dan juga sepanjang garis T4-T1, diperoleh bahwa<br /><br />Q1 = Ch x (T3 - T2)<br /><br />Q2 = Ch x (T4 - T1)<br /><br />dimana,<br /><br />Q, kuantitas tenaga panas (quantity of heat energy, heat quantity).<br />Ch, kapasitas tenaga panas (capacity of heat energy, heat capacity).<br /><br />shg diperoleh hubungan antara kuantitas tenaga panas dgn perubahan suhu,<br /><br />Q2 / Q1 = T4 - T1 / T3 - T2</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-48901457307969212562008-05-06T10:05:00.000-07:002008-05-06T10:12:35.153-07:00SIKLUS MESIN 4-TAK (Bagian Enam)<span class="postbody"><span style="font-weight: bold;">4. LANGKAH PEMBUANGAN|PENGELUARAN GAS [GARIS T4-T1 DAN GARIS T1-T0, T4 = 70 C, T1 = 25 C]</span><br /><br /><img style="width: 207px; height: 311px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/14exhaust.jpg" border="0" /><img style="width: 213px; height: 313px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/24exhaust.jpg" border="0" /><br /><img style="width: 385px; height: 288px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />GARIS T4-T1, T4 = 70 C<br />4.A. Garis T4-T1 adalah garis fase proses isovolumik|isokorik quasi-statik termodimamik, menggambarkan proses pendinginan dan pengeluaran tenaga panas hasil pembakaran, ketika klep|katup keluar|buang membuka. Dlm proses ini, volume gas tetap pd V2, bobot gas campuran tetap m2, tekanan gas merosot turun dr P4 ke P1, shg suhu gas merosot turun dari T4 ke T1.<br /><br />(P4 - P1) . V2 = m2 . R . (T4 - T1)<br /><br />dimana gas sisa pembakaran didinginkan sampai mencapai tekanan dan suhu udara luar, shg tekanan dan suhu gas merosot sekitar 1/2,8 x lipat, 70 ke 25 derajat.<br /><br />Dlm proses ini, klep|katup keluar|buang membuka, shg sistem melepaskan tenaga panas ke reservoir panas luar dgn suhu 25 C, yakni knalpot.<br /><br /><br />GARIS T1-T0, T1 = 25 C<br />4.B. Garis T1-T0 adalah garis fase proses isobarik quasi-statik ireversibel termodimamik, menggambarkan langkah pembuangan sisa pembakaran, piston naik, ruang silinder mengecil. Dlm proses isobarik quasi-statik ini, dimana tekanan gas P dan suhu gas T tetap dan setara tekanan atmosfir [udara luar] krn klep|katup keluar|buang terbuka. Volume silinder V mengecil dr V2 ke V1, shg bobot gas sisa pembakaran berkurang dr m2 ke m1.<br /><br />P1 . (V2 - V1) = (m2 - m1) . R . T1<br /><br />dimana gas sisa pembakaran mencapai tekanan dan suhu udara luar, dan dimana pada akhir proses volume dan molekul gas mendekati nol, pd tekanan dan suhu udara luar.<br /><br />P1 . V1 = m1 . R . T1<br /><br />Sampai disini 6 fase siklus Otto dlm siklus mesin 4-tak berakhir dan berulang kembali menjalani daur ulangnya.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-31511522266878064372008-05-06T10:03:00.000-07:002008-05-06T10:10:00.952-07:00SIKLUS MESIN 4-TAK (Bagian Lima)<span class="postbody"><span style="font-weight: bold;">3. LANGKAH PENYALAAN|PEMBAKARAN DAN PENDAYAAN|KONVERSI GAS [GARIS T2-T3 DAN KURVA T3-T4, T3 = 644 C DAN T4 = 70 C]</span><br /><br /><img style="width: 196px; height: 297px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/13power.jpg" border="0" /><img style="width: 205px; height: 296px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/23power.jpg" border="0" /><br /><br /><img style="width: 388px; height: 291px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />GARIS T2-T3, T3 = 644 C<br />3.A. Garis T2-T3 adalah garis fase proses isovolumik|isokorik quasi-statik termodimamik, menggambarkan proses pemanasan dan penyalaan dan pembakaran gas campuran bahanbakar dan udara oleh percikan busi, ketika pasangan klep|katup tertutup. Dlm proses ini, Volume gas tetap pd V1, tp krn pemanasan, tekanan gas meningkat naik dr P2 ke P3, shg suhu gas meningkat naik dari T2 ke T3.<br /><br />(P3 - P2).V1 = m2 . R . (T3 - T2)<br /><br />dimana gas dibakar, shg tekanan dan suhu gas meningkat sekitar 2,8 x lipat, dari 230 C ke 644 C.<br /><br />Dlm proses ini, pasangan klep|katup dlm keadaan tertutup, shg tak ada gas masuk ke dan keluar dr silinder, tp silinder menyerap tenaga panas dr serangkaian reservoir panas luar dgn rangkum suhu panas dr T2 ke T3, yakni peledakan gas campuran bahanbakar dan udara oleh percikan listrik busi.<br /><br /><br />KURVA T3-T4, T4 = 70 C<br />3.B. Kurva T3-T4 adalah kurva fase proses adiabatik isentropik quasi-statik reversibel termodinamik, menggambarkan langkah pendayaan krn pembakaran gas campuran udara dan bahanbakar dlm silinder ketika pasangan klep|katup tertutup shg piston turun 180 derajat, ruang silinder membesar. Dlm proses adiabatik quasi-statik ini, volume silinder dan volume V membesar dr V1 ke V2, bobot gas campuran tetap m2, tekanan gas P merosot turun dr P3 ke P4, dan suhu gas T merosot turun dr T3 ke T4<br /><br />(P3 - P4)(V2 - V1) = m2 . R . (T3 - T4)<br /><br />dimana gas dimuaikan, shg tekanan dan suhu gas merosot sekitar 1/9,2 x lipat, dari 644 C ke 70 C.<br /><br />Perubahan volume berbanding terbalik dgn perubahan suhu, krn volume membesar dan suhu merosot.<br /><br />(V1 / V2)^(h-1) = T4 / T3<br /><br />dimana h, panas jenis (spesific heat) gas campuran udara dan bahanbakar.<br /><br />Utk aproksimasi ideal, h = 2, formula menjadi<br /><br />V1 / V2 = T4 / T3<br /><br />V1 . T3 = V2 . T4</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-13331204204020280732008-05-06T01:29:00.000-07:002008-05-06T10:09:38.658-07:00SIKLUS MESIN 4-TAK (Bagian Empat)<span class="postbody"><span style="font-weight: bold;">2. LANGKAH PEMAMPATAN|KOMPRESI GAS [KURVA T1-T2, T2 = 230 C]</span><br /><br /><br /><img style="width: 202px; height: 309px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/12compression.jpg" border="0" /><img style="width: 209px; height: 306px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/22compression.jpg" border="0" /><br /><br /><img style="width: 427px; height: 320px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />KURVA T1-T2, T2 = 230 C<br />Kurva T1-T2 adalah kurva fase proses adiabatik isentropik quasi-statik reversibel termodinamik, menggambarkan langkah pemampatan gas campuran udara dan bahanbakar dlm silinder ketika pasangan klep|katup tertutup dan piston naik 180 derajat, ruang silinder mengecil. Dlm proses ini, volume silinder dan volume gas V mengecil dr V1 ke V2, bobot molekul gas campuran bahanbakar dan udara tetap m2, tekanan gas P meningkat naik dr P1 ke P2, dan suhu gas T meningkat naik dr T1 ke T2<br /><br />(P2 - P1).(V2 - V1) = m2.R.(T2 - T1)<br /><br />dimana gas dimampatkan, shg tekanan dan suhu gas meningkat sekitar 9,2 x lipat, dari 25 C ke 230 C.<br /><br />Perubahan volume berbanding terbalik dgn perubahan suhu, krn volume mengecil dan suhu meningkat.<br /><br />(V1 / V2)^(h-1) = T1 / T2<br /><br />dimana h, panas jenis (spesific heat) gas campuran udara dan bahanbakar.<br /><br />Utk aproksimasi ideal, h = 2, formula menjadi<br /><br />V1 / V2 = T1 / T2<br /><br />V1 . T2 = V2 . T1</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-34954351352313294092008-05-05T03:35:00.000-07:002008-05-05T11:51:54.987-07:00SIKLUS MESIN 4-TAK (Bagian Tiga)<span class="postbody"><span style="font-weight: bold;">1. LANGKAH PENGAMBILAN|PEMASUKAN | PENGISAPAN GAS [GARIS T0-T1, T1 = 25 C]</span><br /><br /><img style="width: 261px; height: 394px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/11intake.jpg" border="0" /><br /><br /><br /></span><span class="postbody"><img style="width: 281px; height: 364px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/21intake.jpg" border="0" /></span><span class="postbody"><img style="width: 420px; height: 314px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br />GARIS T0-T1, T1 = 25 C<br />Garis T0-T1 adalah garis fase proses isobarik-isotermik quasi-statik termodimamik, menggambarkan langkah pemasukan | pengambilan dan penyedotan gas campuran udara dan bahanbakar pd tekanan dan suhu tetap dr karburator ke silinder mesin, ketika klep|katup masuk|ambil membuka dan piston turun 180 derajat, ruang silinder membesar. Dlm proses ini, tekanan gas P dan suhu gas T, tetap dan setara tekanan dan suhu standar normal udara luar (normal standard atmospheric pressure and temperature), krn klep|katup masuk|ambil terbuka. Volume silinder V membesar dr V1 ke V2, shg bobot molekul gas campuran bahanbakar dan udara dlm silinder bertambah dr m1 ke m2.<br /><br />P1 . (V2 - V1) = (m2 - m1). R . T1<br /><br />P1 = P0 = Patm, tekanan atmosfir | udara luar<br />T1 = T0 = Tatm, suhu atmosfir | udara luar<br />m1 = mo = nol [ideal nol, praktis mendekati nol]<br /><br />dimana suhu awal silinder setara suhu udara luar, sekitar 25 C.<br /><br />Dlm proses ini, klep|katup masuk|ambil membuka, shg sistem menyerap tenaga panas dr reservoir panas luar dgn suhu 25 C, yakni karburator.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-92038669130430815332008-05-05T03:34:00.000-07:002008-05-05T03:35:36.974-07:00SIKLUS MESIN 4-TAK (Bagian Dua)<span class="postbody"><span style="color: blue;"><span style="font-weight: bold;">FORMULA DASAR TERMODINAMIK GAS IDEAL</span></span><br /><br />Utk informasi anda saja, bagian ini mengandung batasan istilah (term definition) proses dlm termodinamika yg digunakan utk menjelaskan rangkaian proses berlangsung dlm mesin bakar bensin 4-tak, dan formula matematik fisika, dasar termodinamika, yd digunakan utk melakukan perhitungan teknik dan memperoleh kesimpulan.<br /><br />Dlm sistem termodinamik ada bbrp istilah utk proses, yg dlm konteks ini, al sbb.<br /><br /> <span style="font-weight: bold;">reversibel (reversible)</span>: proses bisa-dibalik, bisa-dikembalikan, bisa bolak-balik.<br /> <span style="font-weight: bold;">ireversibel (irreversible)</span>: proses tak bisa-dibalik.<br /> <span style="font-weight: bold;">quasi-statik (quasi-static)</span>: proses dgn statik infinitesimal, hampir statik, hampir stabil.<br /> <span style="font-weight: bold;">adiabatik (adiabatic)</span>: proses dgn aliran panas (heat flow) atau perpindahan panas (heat transfer), dimana efek kompresi adiabatik adalah pemanasan gas, dan sebaliknya, efek ekspansi adiabatik adalah pendinginan gas.<br /> <span style="font-weight: bold;">isentropik (isentropic)</span>: proses pd entropi tetap (constant entropy). Suatu proses adibatik reversibel adalah isentropik, dimana selama berlangsung perubahan adibatik, entropi tetap tak berubah.<br /> <span style="font-weight: bold;"> isobarik (isobaric) atau isopiestik (isopiestic)</span>: proses pd tekanan tetap (constant pressure).<br /> <span style="font-weight: bold;"> isotermik, isotermal (isothermic, isothermal)</span>: proses pd suhu tetap (constant temperature).<br /> <span style="font-weight: bold;">isovolumik, isovolumetrik (isovolumic, isovolumetric)</span> atau isokorik (isochoric): proses pd volume tetap (constan volume).<br /><br /><br />Disini tak akan dibahas lbh lanjut ttg bbg istilah termodinamik ini, cukup hanya sbg pengetahuan dasar utk membedakan kelangsungan suatu proses termodinamik dlm mesin pembakaran dalam 4-tak dgn bahanbakar bensin akan dikupas secara rinci disini.<br /><br /><br />Berikut adalah formula dasar termodinamika.<br /><br />Buat yg gerah dgn matematika, cukup sbg pengetahuan saja, dan silahkan lewatkan, dan lihat ringkasan dan kesimpulan pd bagian akhir.<br /><br /><br />Sistem termodinamik adalah merupakan fungsi 4-dimensional dlm suatu sistem tertutup,<br /><br />f (P, V, T, m) = 0<br /><br />dengan formula dasar keseimbangan termodinamik (themodynamic equilibrium)<br /><br />P . V = m . R . T<br /><br />dimana,<br /><br />p = pressure (tekanan, desakan), dlm unit Pa (Pascal) atau N/m2 (Newton per square metre).<br />T = temperature (suhu), dlm unit K (Kelvin) atau C (Celcius, Centigrade).<br />V = volume (isi, kandungan), dlm unit m3 (cubic metre).<br />m = mass (masa, bobot), dlm unit kg (kilogramme).<br />R = universal gas constant (konstanta gas universal), dlm unit Pa.m3/kg.K.<br /><br />Unit|satuan ukuran digunakan disini adalah unit sistem internasional (SI unit, systeme international d'unites). Dlm rekayasa termodinamik (thermodynamic engineering) digunakan satuan rekayasa Inggris (British engineering unit). Dlm uraian ini tak dibahas lbh jauh ttg unit ukuran, dan diluar cakupan tulisan ini.<br /><br />Jika kandungan panas jenis gas diperhitungkan, maka formula diatas menjadi<br /><br />P . V^h = m . R . T = K<br /><br />dan<br /><br />h = cp / cv<br />R = cp - cv, utk gas ideal.<br /><br />dimana,<br /><br />h = panas jenis (specific heat) gas, rasio tampungan|kapasitas panas jenis gas.<br />c = tampungan|kapasitas panas jenis (specific heat capacity) gas.<br />cp= c pd tekanan tetap; kapasitas panas jenis isobarik.<br />cv= c pd volume tetap; kapasitas panas jenis isovolumik.<br />C = tampungan|kapasitas panas (heat capacity, thermal capacity) gas, yakni kuantitas panas dibutuhkan utk meningkat 1 derajat suhu suatu gas.<br />K = tetapan|konstanta (constant).<br /><br />Q = C . T<br />dQ = C . dT<br /><br />dimana,<br /><br />Q = kuantitas panas (quantity of heat, heat quantity).<br />dQ= perubahan kuantitas panas.<br />dT= perubahan suhu (temperature difference).<br /><br />Q = S . T<br />dQ = dS . T<br /><br />S = Q / T<br />dS = dQ /T<br /><br />dimana,<br /><br />S = entropi (entropy), ukuran relativ kuantitas energi tak-bisa-diperoleh dlm suatu sistem.<br />dS= perubahan entropi.<br /><br />H = U P . V<br /><br />dimana,<br /><br />H = entalpi (enthalpy), kandungan panas (heat content).<br />U = tenaga internal (internal energy).<br /><br /><br />catatan penulisan:<br />tanda . atau * atau x berarti kali.<br />tanda ^ atau ** berarti pangkat (exponent).<br />tanda ^(1/2) atau **0,5 berarti pangkat setengah atau akar kuadrat (square root).</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-2987467201209724852008-05-05T03:27:00.000-07:002008-05-05T11:52:18.621-07:00SIKLUS MESIN 4-TAK (source suzuki-thunder forum)<span class="postbody"><span style="color:red;"><span style="font-weight: bold;">FASE TERMODINAMIK SIKLUS OTTO DALAM SIKLUS MESIN 4-TAK,<br />FORMULASI DAN KALKULASI RASIO KOMPRESI DAN EFISIENSI TERMAL MESIN,<br />DAN EFEK NUFTON SPB TERHADAP KINERJA MESIN</span></span><br /><br /><br /><span style="font-weight: bold;">BAGIAN PERTAMA</span><br /><br />Perilaku mesin bensin 4-tak dpt dijabarkan dlm termodinamika menggunakan formula matematika fisika sederhana.<br /><br />Untuk menyederhanakan masalah dan memudahkan perhitungan, dilakuan pendekatan dgn pengandaian keadaan ideal, sbb.<br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeenginerun-ani.gif" border="0" /><br /><br /><br /><br /> 1. dinding silinder adalah metal ideal, shg tak ada tenaga panas hilang krn penyerapan panas oleh metal dinding silinder.<br />2. gesekan|friksi antara bagian2 mesin dianggap nol atau mendekati nol krn mesin menggunakan oli | minyak pelumas ideal shg tak ada tenaga gerak hilang utk mengatasi gesekan.<br />3. udara yg memasuki silinder mesin, berlaku sbg gas ideal yg memiliki kapasitas panas tetap, dimana koeefisien panas jenis (specific heat) dianggap smdgn 2.<br />4 mesin dlm status "idle", tanpa beban, kendaraan diam, shg tak ada akselerasi|percepatan dan dekselerasi|perlambatan dlm gerak mesin, shg seluruh proses adalah "quasi-static" alias berlangsung dgn perubahan stabil penuh.<br /><br /><br />Dgn menggunakan semua asumsi diatas, siklus mesin 4-tak dpt dijabarkan dlm termodinamika sbg 6 fase siklus Otto standar-udara (air-standard Otto Cycle), yg terdiri dari 6 proses sederhana gas ideal, sbb.<br /><br /><br /><img src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/004strokeengine-ani.gif" border="0" /><br /><br />1.X. pengambilan|pemasukan | penyedotan gas [campuran bahanbakar dan udara].<br />2.X. pemampatan|kompresi gas<br />3.A. pemanasan dan pembakaran gas<br />3.B. pendayaan|konversi gas, dr tenaga panas ke tenaga gerak.<br />4.A. pendinginan gas sisa pembakaran.<br />4.B. pembuangan|pengeluaran gas sisa pembakaran.<br /><br />6 fase siklus Otto ini dpt digambarkan dlm diagram PVT (pressure, volume, temperature; tekanan, isi, suhu) 3-dimensi, atau diagram PV 2-dimensi sbb.<br /><br /><br /><img style="width: 403px; height: 301px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/otto-cycle-1.gif" border="0" /><br /><br /><br />dimana, masing2 proses digambarkan dgn garis PVT atau kurva PVT.<br /><br /> 1.X. garis. T0-T1<br /> 2.X. kurva T1-T2<br /> 3.A. garis. T2-T3<br /> 3.B. kurva T3-T4<br /> 4.A. garis. T4-T1<br /> 4.B. garis. T1-T0<br /><br /><br />Lihat gambar.<br /><br /><img style="width: 381px; height: 286px;" src="http://i222.photobucket.com/albums/dd96/thunderianz/mechanic/35engine-ani.gif" border="0" /></span><span class="gensmall"><br /></span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-19334428334433373922008-05-05T03:25:00.000-07:002008-05-05T11:44:58.786-07:00Membuat Sendiri Command Aliases AutoCAD<span class="postbody"> Salah satu kemudahan dalam AutoCAD adalah kita bisa menggunakan banyak cara untun memasukan perintah. Kita bisa menggunakan command line, toolbar, maupun menu.<br /><br />Bagi yang sudah lama menggunakan AutoCAD tertuama dari mulai versi DOS, tentu sangat terbisa untuk menginput perintah AutoCAD melalui keyboard. Bagi pengguna baru pun sangatlah baik bila membiasakan diri menggunakan keyboard sebagai input utama. Pengguna AutoCAD dapat menggunakan kedua tangannya secara efektif yakni tangan kiri pada keyboard dan tangan kanan pada mouse, atau sebaliknya bagi para pengguna kidal/ left handed.<br /><br />AutoCAD memberikan kemudahan untuk setiap command yang diinput melalui kerboard berupa AutoCAD Commad Ailases. Pengguna hanya menginput sedikit hurup saja untuk menggantikan perintah aslinya yang terkadang cukup panjang.<br /><br />Misalnya pada perintah untuk membuat garis, maka pengguna cukup menginput “L” untuk menggantikan “LINE” atau “C” untuk menggantikan “CIRCLE”. AutoCAD akan menterjemahkan huru L tersebut sebagai alias perintah LINE begitu pula dengan C sebagai alias perintah CIRCLE.<br /><br /><img style="width: 436px; height: 89px;" src="http://my-image-hosting.com/images.php/i470_a1.JPG" border="0" /><br /><br />Kita dapat melihat konfigurasi alias perintah yang terdapat pada AutoCAD. Pada versi-versi yang lebih baru, biasanya disediakan sendiri fasilitas yang disebut dengan AutoCAD Command Aliases Editor. Untuk panduannya kita dapat mencari pada search index yang tersedia pada menu HELP. Untuk versi AutoCAD yang lebih tua, kita harus mengedit secara manual pada file acad.pgp. Cara ini juga dapat digunakan pada versi terbaru.<br /><br />Bukalah file acad.pgp yang biasanya tersimpan pada direktori dimana kita menginstall AutoCAD. Pada versi 2006 kita dapat dengan mudah membuka file ini melalui menu Tools > Customize > Edit Program Parameter (acad.pgp).<br /><br />Komputer akan memanggil file acad.pgp melalui Notepad.<br /><br /><img src="http://my-image-hosting.com/images.php/i471_a2.JPG" border="0" /><br /><br />Kita dapat melhat alias-alias standar untuk perintah-perintah yang sudah ada. Dengan mengikuti format yang sama kita dapat menambahkan alias perintah yang baru. Misalnya kita akan manambahkan command alias KOTAK atau KO untuk RECTANGLE.<br /><br /><span style="font-style: italic;">Tips: Sebelum mencoba, buatlah file acad.pgp cadangan untuk berjaga-jaga dan mempermudah ketika akan mengembalikan ke setingan awal.</span><br /><br /><img src="http://my-image-hosting.com/images.php/i472_a3.JPG" border="0" /><br /><br />Setelah menambahkan alias perintah yang baru, simpanlah file acad.pgp tersebut (save), kemudian restart program AutoCAD agar setingan tersebut dapat dipanggil.<br /><br />Cobalah apakah alias perintah yang kita buat dapat digunakan.<br /><br /><img style="width: 415px; height: 236px;" src="http://my-image-hosting.com/images.php/i473_a4.JPG" border="0" /><br /><br /><span style="font-weight: bold;">Selamat mencoba !!!!</span></span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0tag:blogger.com,1999:blog-25350634.post-1672887067488592702008-05-05T03:23:00.000-07:002008-05-05T03:24:17.263-07:00Persamaan Navier-Stokes<span class="postbody"> Persamaan Navier-Stokes (dinamakan dari Claude-Louis Navier dan George Gabriel Stokes) adalah serangkaian persamaan yang menjelaskan pergerakan dari suatu fluida seperti cairan dan gas. Persamaan-persamaan ini menyatakan bahwa perubahan dalam momentum (percepatan) partikel-partikel fluida bergantung hanya kepada gaya viskos internal (mirip dengan gaya friksi) dan gaya viskos tekanan eksternal yang bekerja pada fluida. Oleh karena itu, persamaan Navier-Stokes menjelaskan kesetimbangan gaya-gaya yang bekerja pada fluida.<br /><br />Persamaan Navier-Stokes memiliki bentuk persamaan diferensial yang menerangkan pergerakan dari suatu fluida. Persaman seperti ini menggambarkan hubungan laju perubahan suatu variabel terhadap variabel lain. Sebagai contoh, persamaan Navier-Stokes untuk suatu fluida ideal dengan viskositas bernilai nol akan menghasilkan hubungan yang proposional antara percepatan (laju perubahan kecepatan) dan derivatif tekanan internal.<br /><br />Untuk mendapatkan hasil dari suatu permasalahan fisika menggunakan persamaan Navier-Stokes, perlu digunakan ilmu kalkulus. Secara praktis, hanya kasus-kasus aliran sederhana yang dapat dipecahkan dengan cara ini. Kasus-kasus ini biasanya melibatkan aliran non-turbulen dan tunak (aliran yang tidak berubah terhadap waktu) yang memiliki nilai bilangan Reynold kecil.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com1tag:blogger.com,1999:blog-25350634.post-18129402383611516912008-05-05T03:22:00.001-07:002008-05-05T03:22:58.169-07:00Hipotesis Kontinum<span class="postbody">Fluida disusun oleh molekul-molekul yang bertabrakan satu sama lain. Namun demikian, asumsi kontinum menganggap fluida bersifat kontinu. Dengan kata lain, properti seperti densitas, tekanan, temperatur, dan kecepatan dianggap terdefinisi pada titik-titik yang sangat kecil yang mendefinisikan REV (‘’Reference Element of Volume’’) pada orde geometris jarak antara molekul-molekul yang berlawanan di fluida. Properti tiap titik diasumsikan berbeda dan dirata-ratakan dalam REV. Dengan cara ini, kenyataan bahwa fluida terdiri dari molekul diskrit diabaikan.<br /><br />Hipotesis kontinum pada dasarnya hanyalah pendekatan. Sebagai akibatnya, asumsi hipotesis kontinum dapat memberikan hasil dengan tingkat akurasi yang tidak diinginkan. Namun demikian, bila kondisi benar, hipotesis kontinum menghasilkan hasil yang sangat akurat.<br /><br />Masalah akurasi ini biasa dipecahkan menggunakan mekanika statistik. Untuk menentukan perlu menggunakan dinamika fluida konvensial atau mekanika statistik, angka Knudsen permasalahan harus dievaluasi. Angka Knudsen didefinisikan sebagai rasio dari rata-rata panjang jalur bebas molekular terhadap suatu skala panjang fisik representatif tertentu. Skala panjang ini dapat berupa radius suatu benda dalam suatu fluida. Secara sederhana, angka Knudsen adalah berapa kali panjang diameter suatu partikel akan bergerak sebelum menabrak partikel lain.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com1tag:blogger.com,1999:blog-25350634.post-12026420835338681892008-05-05T03:21:00.000-07:002008-05-05T03:22:28.676-07:00Sekilas Mengenai Mekanika Fluida<span class="postbody">Mekanika fluida adalah displin ilmu yang mempelajari fluida (yang dapat berupa cairan dan gas). Mekanika fluida dapat dibagi menjadi fluida statik dan fluida dinamik. Fluida statis mempelajari fluida pada keadaan diam sementara fluida dinamis mempelajari fluida yang bergerak.<br /><br />Dalam pandangan secara mekanis, sebuah fluida adalah suatu substansi yang tidak mampu menahan tekanan tangensial. Hal ini menyebabkan fluida pada keadaan diamnya berbentuk mengikuti bentuk wadahnya.<br /><br />Seperti halnya model matematika pada umumnya, mekanika fluida membuat beberapa asumsi dasar berkaitan dengan studi yang dilakukan. Asumsi-asumsi ini kemudian diterjemahkan ke dalam persamaan-persamaan matematis yang harus dipenuhi bila asumsi-asumsi yang telah dibuat berlaku.<br /><br />Mekanika fluida mengasumsikan bahwa semua fluida mengikuti:<br /><br /> * Hukum kekekalan massa<br /> * Hukum kekekalan momentum<br /> * Hipotesis kontinum, yang dijelaskan di bagian selanjutnya.<br /><br />Terkadang, akan lebih bermanfaat (dan realistis) bila diasumsikan suatu fluida bersifat inkompresibel. Maksudnya adalah densitas dari fluida tidak berubah ketika diberi tekanan. Cairan terkadang dapat dimodelkan sebagai fluida inkompresibel sementara semua gas tidak bisa.<br /><br />Selain itu, terkadang viskositas dari suatu fluida dapat diasumsikan bernilai nol (fluida tidak viskos). Terkadang gas juga dapat diasumsikan bersifat tidak viskos. Jika suatu fluida bersifat viskos dan alirannya ditampung dalam suatu cara (seperti dalam pipa), maka aliran pada batas sistemnya mempunyai kecepatan nol. Untuk fluida yang viskos, jika batas sistemnya tidak berpori, maka gaya geser antara fluida dengan batas sistem akan memberikan resultan kecepatan nol pada batas fluida.</span>Nanang Suryanahttp://www.blogger.com/profile/01246288191295866961noreply@blogger.com0