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, the improvement of the diesel engine performance is based on the optimization of the whole combustion system efficiency. The focus of new technological solutions is devoted to the optimization of thermodynamic efficiency especially in terms of reduction of losses of heat exchange. In this context, it is required a continuous development of the engine combustion system, first of all the injection system and in particular the nozzle design. To this reason in the present paper a new concept of an open nozzle spray was investigated as a possible solution for application on diesel engines. The study concerns some experimental and 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 an appropriate choice of geometrical design parameters. The characteristics of nozzle open spray concept (in terms of spray penetration and diffusion) were evaluated in a constant volume combustion bomb and validated by numerical simulations with the OpenFOAM libraries in the lib-ICE version of the code. The considered injector configuration is proved to be a promising solution for the realization of a high-pressure diesel cone spray. It was assessed that spray atomization and penetration are sensible to the injection control parameters, in particular to the injection pressure level, and to the HV (stationary level of the voltage command at the actuator). This could mean, in a certain sense, the possibility to graduate injection control parameters in order to assure an appropriate control of spray penetration and atomization levels in a dedicated 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 behavior for high pressure MHN injectors, indicates a quite good prevision of the radial tip penetration (TP) but a sensible overestimation of axial TP over all the injection event. CFD simulation describes a rapid breakup process immediately after the fuel discharge providing a finely atomized spray along the whole circumference