Vol. 41, No. 1 (2018) (4)

ABSTRACT: Because of increasingly strict environmental regulations, reducing the emission of pollutants of diesel engines has become a major challenge faced by researchers. At, the most common approach to reducing emissions is to increase the injection pressure of the fuel. However, when the injection pressure is increased, the matched needle valve assembly undergoes deformation which will tend to increase the leakage of the needle valve assembly and interfere with the normal operation of a diesel engine. Thus, the sealing performance of a needle valve assembly must be considered when raising the injection pressure of an injector. This paper examines the effects of machining annular grooves on the needle valve in order to reduce the leakage of a needle valve assembly. To begin with, fluid lubrication and tribology principles are used to analyze the sealing mechanism of an annular groove needle valve assembly. As a second part of the study, the fuel film thickness and leakage of different annular groove needle valve assemblies were numerically simulated. Ultimately, an experimental apparatus was set-up to test the leakage of different annular groove needle valve assemblies under different pressures. The research results show that annular groove needle valves could reduce the leakage of needle valve assemblies. The paper has important findings for improving the sealing performance and structural optimization of needle valve assemblies.

Keywords : Needle valve assembly; Sealing performance; Theoretical; Numerical; Experimental leakage flow determination.