Experiment and Numerical Study on Critical Conditions for Auto-Ignition of Tpgme Spray under Engine Cold-Start Conditions

The development of alternative fuels and the study of low temperature combustion performance are key to solving the difficulties of cold-starting diesel engines. However, current research on TPGME has mainly focused on its effect on soot emissions and there is a lack of research on the auto-ignition of TPGME spray under cold start conditions. In this paper, the critical ignition temperature of TPGME spray and the misfire mechanism are investigated using experimental and simulation methods. Results show that the critical ignition temperature of TPGME decreases with increasing ambient density, and the critical ignition temperature is 653 K at the ambient density of 15.7 kg/m3. There are several main reasons for misfires at critical temperature conditions. There are equivalence ratio boundaries for high-temperature reactions, where the OH concentration in the flame decreases by orders of magnitude when F<0.5 or F>1.75. As the initial temperature decreases, the equivalence ratio in the area of higher OH concentration within the spray decreases and the spray misfire when the ignitable equivalence ratio boundary is exceeded. As the initial temperature decreases, the TPGME low-temperature core reaction L3(ROO→QOOH) and the main exothermic reaction CH2O+OH<=>HCO+H2O rates are reduced, which is not conducive to the onset of ignition.