The effect of cooled EGR on combustion and load extension in a kerosene spark-ignition engine

It's currently a trend to use aviation kerosene as the fuel for aviation spark-ignition reciprocating engines because of its good safety compared with gasoline during the transportation, storage and use. However, when converting the gasoline engines to kerosene, power density is constrained by knock combustion for its lower octane number, especially for four-stroke engines. In this study, cooled exhaust gas recirculation (EGR) was adopted to extend the output of a kerosene engine at knock limits based on a four-cylinder, four-stroke, horizontally opposed engine. First, the effects of cooled EGR on combustion characteristics are studied, including the in-cylinder pressure, heat release rate, knock intensity etc. Then, load extension via cooled EGR was experimental analyzed. The results show that when the EGR rate increased from 0% to 10%, the indicated mean effective pressure (IMEP) at knock limits improved by 7%. At the same time, because of higher specific heat ratio and reduced heat transfer loss, specific fuel consumption decreased by 8.1%, and the indicated thermal efficiency increased from 23.5% to 25.6%.