Experimental Investigation of Fuel-Spray Droplet Size Distribution Relating to Cold Start Conditions in Diesel Engines

It is crucial to investigate the droplet diameter distribution properties of spray during cold start conditions in diesel engines in order to comprehend the low-temperature fuel atomization process. A low-temperature fuel atomization test system comprising a constant-volume chamber, a low-temperature fuel supply and injection system, and He-Ne laser measurement technology was constructed. Based on this experimental system, the droplet size distribution characteristics were measured at injection pressures between 40 and 80 MPa, ambient pressure between 1.8 and 2.6 MPa, and fuel temperatures between 20°C and −40°C. The results demonstrated that the increase of injection pressure leads to a higher initial velocity after the fuel leaves the injector nozzle. It was evident that the increase in injection pressure led to a decrease in droplet size of 3.5–9.7 μm based on the Dv10, Dv50, Dv90, and Sauter mean diameter. Compared with the injection pressure, the influence of ambient pressure on the droplet diameter was much smaller, and the droplet diameter was larger under higher ambient pressure. The relative span factor (RSF) values under all experimental conditions were also computed in the work. The increase in fuel temperature led to an increase in the RSF value, which occurred within the range of 0.008–0.012. The research results in this work compensated for the experimental blank of the atomization characteristics of low-temperature fuel at −40°C and provided a foundation for further understanding the droplet breakup process of low-temperature fuel and the subsequent development of computational fluid dynamics simulation models pertaining of diesel engine cold start.