Air Standard Analysis for Internal Combustion Engines

Air-standard analysis treats the fluid flow through the entire engine as air and approxi¬mates air as an ideal gas. In a real engine inlet flow may be all air, or it may be mixed, up with 7% fuel, either gaseous or as liquid droplets, or both. In air-standard analysis, even if all fluid in an engine cycle were air, some error would be introduced by assuming it to be an ideal gas with constant specific heats. At the low pressures of inlet and exhaust, air can accurately be treated as an ideal gas, but at the higher pressures during combustion, air will deviate from ideal gas behavior.