Characterization and prediction of the discharge coefficient of non-cavitating diesel injection nozzles

Abstract

An experimental and theoretical study about the characterization of the discharge coefficient of diesel injection nozzles under non-cavitating conditions is presented in this paper. A theoretical development based on the boundary layer equations has been performed to define the discharge coefficient of a convergent nozzle. The discharge coefficient has been experimentally obtained for a standard diesel fuel under a wide range of Reynolds numbers by two different techniques: mass flow rate measurements and permeability measurements. Five different nozzles have been used: two multi-hole nozzles that have been tested in the frame of this work, and three other single-hole nozzles, the data of which have been taken from previous studies. The experimental results show good agreement with the theoretical expressions, proving that it is possible to predict the discharge coefficient of a non-cavitating nozzle with the equations shown in this paper.