Effect of fuel and compression ratio on Exergetic efficiency of a gasoline engine

The first law of thermodynamics expresses the conservation of energy in all processes and does not apply any restriction on the transfer of energy. However¡ in recent years¡ in order to quantify the quality of energy¡ the concept of exergy has been defined widely used in design¡ simulation and evaluation of various thermal and thermochemical systems. In this study¡ the impact of the fuel and compression ratio on fuel chemical availabilities¡ thermomechanical and total availability in a spark ignition engine was examined. The results showed that by increasing the compression ratio¡ the shift process of the fuel chemical availability graph change. The parameter (a_th) at a compression ratio of 12 for the fuels E_0¡ E_20¡ E_40¡ E_60 and E_85increase to 9.2¡ 11¡ 10.9¡ 10.9 and 10.9% respectively¡ in comparison with compression ratio of 8. Also¡ total availability (a) at compression ratio of 12 is faster. exergy efficiency at compression ratio of 12 for fuels E_0¡ E_20 〖 ¡E〗_(40 )¡E_60 and E_85 increase to 11.7¡ 13.8¡ 11.3¡ 8.9 and 9.9% respectively¡ in comparison with compression ratio of 8%. It should be noted¡ that by increasing the amount of ethanol¡ terms exergy (thermo-mechanical¡ chemical fuel¡ and total) reduced. The efficiency of the second law of thermodynamics increased with increasing volume percent of ethanol.