Effects of intake air temperature on combustion, performance and emission characteristics of a HCCI engine fueled with the blends of 20% n-heptane and 80% isooctane fuels

In this study, the effects of intake air temperature on the cylinder pressure, heat release rate, start of combustion, combustion duration, engine performance and exhaust emissions were investigated in a HCCI gasoline engine fueled with the blends of 20% n-heptane and 80% isooctane fuels. Intake air temperature was changed from 40 degrees C to 120 degrees C. The experiments were performed with a single-cylinder, four-stroke HCCI gasoline engine at two different excessive air coefficients at 1200 rpm. The results showed that in-cylinder pressure and heat release rate increased with the increase of intake air temperature. The increase of intake air temperature caused combustion to advance and the combustion duration to decrease. At 70 degrees C intake air temperature, brake torque decreased by 3.1% when the engine operated with lambda = 0.6 compared to lambda = 0.7. The specific fuel consumption and NO emissions tend to increase at higher intake air temperatures of 100 degrees C and 120 degrees C. It was also found that CO and HC emissions firstly increased and then started to decrease after the 90 degrees C intake air temperature. (C) 2014 Elsevier B.V. All rights reserved.