Experimental and numerical investigation on the jet characteristics of spark ignition direct injection gaseous injector

Natural gas has widely been used as a fuel in conventional Diesel and spark ignition engines. The better understanding of injector parameters on the jet structure is helpful for the combustion optimization. This paper presents an experimental and numerical study on the jet structure of gaseous fuel injector in spark ignition direct injection engine by Schlieren technique and numerical procedure. Helium was injected through a gaseous injector at the different pressure ratios and nozzle diameters to understand the effects of nozzle geometry and pressure ratio for a dedicated correlation of CNG–SIDI injector. It was found that higher pressure ratio and exit nozzle diameter led to more tip penetration except the initial stages of jet development. Numerical simulation at the initial stage of jet development was not in exact agreement with experimental data due to transient effects of the needle lift within the injector tip and experimental errors while reliable results was observed after 1 ms from the start of injection. It is also notable that tip angle of the jet did not have a specific trend when jet develops.