基于废气再循环的乙醇-生物柴油发动机性能试验研究

Experiment study on performance of engine fueled with ethanol-biodiesel using EGR

通过在单缸柴油发电机上燃用5种混合比的乙醇-生物柴油燃料,并采用了16%和28%两种废气再循环(Exhaust Gas Recirculation,EGR)率,对比分析了乙醇-生物柴油混合燃料的经济性,NOx,HC,CO的排放特性和光吸收系数,及EGR对以上性能参数的影响,结果发现:燃用E30B70时,燃烧状况不佳,NOx排放量较低,但HC,CO排放和尾气的光吸收系数较高;随乙醇比例增加,体积油耗增加;在10%的乙醇混合比附近能获得较高的热效率;20%的乙醇混合比,采用EGR可以降低油耗;乙醇混合比为20%以下时,混合燃料的NOx排放量相差较小;采用EGR后,NOx排放量明显降低,且降低量随EGR率增大而增大;各混合比燃料的HC和CO的排放量均随乙醇混合比的增大而增大;随EGR率增大,CO排放量增大。光吸收系数在1/3负荷左右时有极大值,在2/3负荷左右时有最小值;在不同的负荷范围内存在某一混合比的燃料有较优的烟度排放,不同混合比燃料有各自较优的EGR率以获得较低的油耗和HC排放。

In this work, blend fuels were tested. Experiments were carried out on a singlecylinder, 4-cycle, direct injected, air-cooled, naturally aspirated diesel engine at ten loads between no load and a full load of 3000 r/min using 0%, 16% and 28% exhaust gas recirculation （EGR） rate. Fuel economy, emission characteristics and light absorption coefficient of the engine fueled with these ethanol-biodiesel blends were analyzed. The results show that,when fueled with E30B70, the NOx emission is lower, but HC and CO emission and light absorption coefficient are significantly higher. Because of the worse combustion process, the E30B70 blend fuel is not suitable for the engine. As ethanol concentrations in blends increase, the fuel consumption by volume increases, HC and CO emissions increase. A higher thermal efficiency can be obtained when fueled with EIOB90 blend fuel. When fueled with E20B80 and E30B70 blend fuels and using EGR, fuel consumption can be decreased. When the ethanol concentration is 20% or less, the differences of NOx emissions are smaller. The use of EGR can significantly reduce NOx emissions. As the EGR rate increase, CO emissions increase, while NOx emissions are decreased. Light absorption coefficient has a relative maximum value at about 1/3 load, and has a global minimum value at about 2/3 load. At different load range lower smoke emissions can be got when fueled with one of these blends. In order to obtain lower fuel consumption and HC emissions, each one of these blends need to use its respectively optimum EGR rate.