LN02 - Internal Combustion Engines ME422 Ideal Standard...

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1 Internal Combustion Engines – ME422 Ideal Standard Cycles Prof.Dr. Cem Soru ş bay Internal Combustion Engines – ME422 Ideal Air Standard Cycles ¾ Introduction ¾ Comparison between thermodynamic and mechanical cycles ¾ Performance parameters imep, bmep, mechanical efficiency, indicated eff., volumetric eff. ¾ Ideal cycles and thermal efficiencies Otto cycle, Diesel cycle, Dual cycle ¾ Comparison of cycles ¾ Deviations from actual engine cycles
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2 Assumptions Air standard cycles, serve as introduction to the more detailed and accurate models of IC engines provide insight into some of the important parameters that effect engine performance Assumptions; Neglect heat transfer to and from cylinder walls, Replace combustion process by a heat addition process that occurs at constant volume (in Otto cycle ) or at constant pressure (in Diesel cycle ), Do not consider gas exchange process, Assume cylinder charge as a perfect gas (c p and c v are assumed constant) which is pure air. Otto Cycle The Otto cycle is used as a basis of comparison for SI engines The cycle consists of four processes, 1 – 2 isentropic compression from V 1 to V 2 2 – 3 addition of heat Q 23 at constant volume 3 – 4 isentropic expansion to the original volume 4 – 1 rejection of heat Q 41 at constant volume
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