Comparisons of Diesel Spray Liquid Penetration and Vapor Fuel Distributions With In-Cylinder Optical Measurements

The performance of two spray models for predicting liquid and vapor fuel distribution, combustion and emissions is investigated. The model predictions are compared with extensive data from in-cylinder laser diagnostics carried out in an optically accessible heavy-duty, D. I. diesel engine over a wide range of operating conditions. Top-dead-center temperature and density were varied between 800 K and 1100 K and 11.1 and 33.2 kg/m3, respectively. Two spray breakup mechanisms were considered: due to Kelvin-Helmholtz (KH) instabilities and to Rayleigh-Taylor (RT) instabilities. Comparisons of a wide range of parameters, which include in-cylinder pressure, apparent heat release rate, liquid fuel penetration, vapor distribution and soot distribution, have shown that a combination of the KH and the RT mechanisms gives realistic predictions. In particular, the limited liquid fuel penetration observed experimentally was captured by including these two competing mechanisms in the spray model. Furthermore, the penetration of the vapor fuel ahead of the liquid spray was also captured. A region of high soot concentration at the spray tip was observed experimentally and also predicted by the KH-RT spray breakup model. [S0742-4795(00)01504-0]