A Mathematical Model for the Cranking Period in the Cold Start of Diesel Engines

A mathematical model is developed to predict the length of the cranking period of direct injection diesel engines at low ambient temperatures. The model takes into consideration the physical and chemical process that develop in the cylinder over the whole cranking period. The model accounts for the variation in the following: (a) fuel accumulated in the cylinder in both the liquid and the vapor phases, (b) gas temperature and pressure, (c) wall temperature and (d) the autoignition reactions rate. An “Autoignition Index” (AI) is developed to account for the combined effects of fuel volatility and its Cetane Number. The model considers that autoignition starts in the cycle where AI reaches a critical value at the end of the cranking period. The model predictions are compared with the experimental data obtained on a single cylinder diesel engine tested in a cold room using four distillate fuels having different volatilities and Cetane numbers.Copyright © 2003 by ASME