Experimental study on primary breakup of diesel spray under cold start conditions

Studies on primary breakup of diesel spray under room temperature (25 °C) and low temperature (−2 °C), were carried out by mass flow rate measurement and microscopic imaging. It was shown that under low injection pressure and low temperature, raised viscosity and surface tension caused slower penetration and poorer breakup. Under high injection pressure, higher chances of mushroom formation under low temperature due to higher viscosity surprisingly leaded to quicker penetration but still poorer dispersion during the initial spray stage. Low temperature retarded the start of atomization as the needle rose. The end of injection showed a large amount of compact liquid fuel with little dispersion, which was deteriorated by low temperature. In addition, a new equation including the influences of ambient gas on breakup, was proposed to quantify the spray stability, allowing quantitative analysis of the effects of temperature and ambient gas.