Combustion and emission characteristics of RCEM and common rail diesel engine working with diesel fuel and ethanol/hydrous ethanol injected in the intake and exhaust port: Assessment and comparison

In this article, experiments are performed to evaluate and compare the combustion and emission characteristics of a rapid compression-expansion machine (RCEM) and a common rail diesel engine run with diesel fuel and ethanol/hydrous ethanol injection individually in the exhaust and intake manifold. The RCEM is run under diesel engine conditions with two different temperatures, which are 120 degrees C and 180 degrees C to simulate the intake and exhaust state. The flame ionization detector (FID) and gas chromatography (GC) are used to estimate the amount of ethanol introduced in the engine cylinder. The results for RCEM display that the ignition delay significantly diminishes by about 50% with enlarging the mixture temperature of ethanol while the NOx and soot formation enlarge. Regarding the diesel engine results, the proportion of ethanol introduced in the engine cylinder is approximately 80%, 43%, and 47% at ethanol injection duration of 2620 mu s, 3488 mu s, and 4497 mu s, respectively. The peak cylinder pressure, heat release rate, and flame temperature are reduced for pure ethanol injection exhaust mode compared to the intake approach. Moreover, the ignition delay increases as the water content in the aqueous ethanol solution increased. From the combustion and exhaust emission results, it can be deduced that the exhaust mode is recommended, particularly at the low concentration of ethanol in the mixtures, which could be exploited in the commercial combustion applications.