Experimental investigation of atomization characteristics at low temperature environments during diesel engine cold start

Abstract

Exploring the atomization characteristics of fuel in low-temperature environments is crucial for improving the cold start performance of diesel engines. In this work, based on LIEF-PIV laser testing technology, a diesel engine cold start fuel atomization experimental system was built, which could simulate the internal environment of a diesel engine's cylinder during cold start. The concentration and velocity distributions of free-jet spray and wall-impinging spray at low temperature were measured experimentally. The results showed that the decrease in ambient temperature had a significant impact on the rate of evaporation of fuel droplets, which was mainly reflected in two aspects: the total evaporation of the fuel and the uniformity of the distribution of vapor phase. The decrease in fuel temperature led to a decrease in the conversion efficiency of vapor/liquid phases of the fuel. When the fuel temperature was −20 °C, the distribution range of vapor equivalence ratio near the wall area was 0.11–0.59, which is significantly lower than the other two conditions. In addition, the increase in environmental pressure resulted in a certain decrease in the maximum flow velocity and turbulent flow energy of the mixture, with an average decrease of 0.32 m/s in the maximum flow velocity at the three fuel temperatures of 0 °C, −20 °C, and −40 °C.