Combustion Emissions Modeling and Testing of Conventional Diesel Fuel

This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using conventional No. 2 diesel fuel. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform engine combustion simulations. The simulation approach is a predictive combustion simulation, direct-injection jet modeling, which is primarily used to predict the burn rate and NOx emissions. Crank angle dependent fuel injector sac pressure profiles have been measured during combustion tests and used as fuel jet inputs in the combustion modeling to predict injected fuel mass and fuel jet velocity as a function of time. In each emissions test, an in-cylinder pressure profile was measured and used for combustion model calibration to assure a correct burn rate profile was predicted and the exhaust emissions prediction was based on a calibrated burn rate profile which closely resembled the one measured in the test. Engine emissions, which include NOx , HC, CO, and CO2 , measured at various engine speeds and loads were compared to those predicted by the combustion simulations. The maximum differences between simulation-predicted and test-measured emissions data are 30% for the NOx emissions and 68% for the CO2 emissions. However, the results for CO and HC emissions could differ by more than an order of magnitude under the conditions tested. The modeling and testing evaluation of conventional diesel was chosen to provide a comparative baseline analysis that can be extended for predicting combustion emissions of renewable feedstock fuels in development.