Effects of different dilution methods on Fuel Consumption for Gasoline Direct Injection Engine under Different Compression Ratio

Abstract:

Based on a 1.0 L turbocharged engine, stoichiometric, lean burn and exhaust gas recirculation (EGR) conditions were tested under the compression ratios (CR) of 9.6 and 12 to study their combustion and fuel consumption characteristics. The results show that the fuelsaving effect of EGR is better than that of lean combustion under heavy loads with higher compression ratio, and the fuelsaving effect of lean combustion is better under other conditions. By changing CR together with lean burn or EGR, brake specific fuel consumption (BSFC) can be reduced by at most 7.5%, 10.4% and 9.3% comparing with CR9.6 stoichiometric conditions under light, medium and heavy loads respectively. Combined with onedimensional simulation, the reasons and different characteristics of fuel saving under lean burn and EGR conditions under heavy loads are analyzed and compared. The results show that lean burn under high compression ratio and heavy load when excess air ratio (λ)<1.4 cannot suppress knocking, and the fuel saving effect is not obvious; under the same working condition EGR can effectively suppress knocking and reduce fuel consumption up to 5.5%. The fuelsaving of lean burn and EGR under heavy loads are mainly due to the reduction of heat transfer loss and exhaust loss. The sum of their contribution to fuel economy is higher than 90%.

Key words:gasoline engine; compression ratio; lean burn; exhaust gas recirculation; fuel saving mechanism