Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 1 - Hydraulic performance

Nozzle hydraulic performance has a significant impact on diesel spray development and combustion characteristics. Thus, it is important to understand the links between the nozzle geometry, the internal flow features and the spray formation. In this paper, a detailed analysis of the impact of the nozzle orifices inclination angle on its hydraulic performance is performed. For this purpose, three different nozzles with included angles of 90, 140 and 155 degrees are evaluated. Instantaneous injection rate and momentum flux are measured on a set of injector operating conditions (mainly injection pressure and discharge pressure). The results show that higher inclination angles lead to smaller mass flow and momentum flux at steady-state conditions, due to the higher losses at the orifice inlet. These losses are translated in lower both area and velocity coefficients. Nevertheless, the impact of this parameter is limited thanks to the counter-acting effect of the hydrogrinding process, which produces larger rounding radii at the orifice inlet as the included angle increases. Based on the experimental results, correlations of the discharge coefficient as a function of the Reynolds number are obtained and evaluated.