Experimental and Numerical Analysis of a High-Pressure Outwardly Opening Hollow Cone Spray Injector for Automotive Engines

In the aim of reducing CO2 emissions and fuel consumption, theimprovement of the diesel engine performance is based on theoptimization of the whole combustion system efficiency.The focus of new technological solutions is devoted to theoptimization of thermodynamic efficiency especially in terms ofreduction of losses of heat exchange.In this context, it is required a continuous development of the enginecombustion system, first of all the injection system and in particularthe nozzle design. To this reason in the present paper a new conceptof an open nozzle spray was investigated as a possible solution forapplication on diesel engines. The study concerns some experimentaland numerical activities on a prototype of an open nozzle.An external supplier provided the prototypal version of the injector,with a dedicated piezoelectric actuation system, and with anappropriate choice of geometrical design parameters. Thecharacteristics of nozzle open spray concept (in terms of spraypenetration and diffusion) were evaluated in a constant volumecombustion bomb and validated by numerical simulations with theOpenFOAM libraries in the lib-ICE version of the code.The considered injector configuration is proved to be a promisingsolution for the realization of a high-pressure diesel cone spray. Itwas assessed that spray atomization and penetration are sensible tothe injection control parameters, in particular to the injection pressurelevel, and to the HV (stationary level of the voltage command at theactuator). This could mean, in a certain sense, the possibility tograduate injection control parameters in order to assure anappropriate control of spray penetration and atomization levels in adedicated engine combustion chamber.The numerical results show that the adopted setup of spray sub-models,well assessed in previous work in capturing the whole spray behaviorfor high pressure MHN injectors, indicates a quite good prevision ofthe radial tip penetration (TP) but a sensible overestimation of axial TPover all the injection event. CFD simulation describes a rapid breakupprocess immediately after the fuel discharge providing a finelyatomized spray along the whole circumference