Mathematical model of service life of precision injection nozzle pairs of motor-and-tractor internal combustion engines

Abstract

This paper discusses a theoretical description of the wear process of precision injection nozzle pairs of diesel engine injectors taking into account various contributions to the dissipation of the needle impact energy against the valve seat. To evaluate the influence of various factors affecting the wear and service life of precision pairs, the paper presents a functional (physical) model of precision injector mating which allows determining the service life of its parts. The developed model takes into account the influence of various factors of wear: material properties of mating parts; part surface patterns (roughness); fuel layer properties in the nozzle working gap; fatigue processes in the surface layer of parts, etc. The research goal consists in the necessity of theoretical substantiation, mathematical modeling and research of parameters of serviceable condition of precision injection nozzles of diesel engine injectors. The functional dependence of hydraulic density of precision injection nozzles is determined taking into account the operational properties of fuel affecting the gap in the precision mating of “needle - nozzle body”. Theoretical dependences of energy dissipation of the needle impact on the nozzle body seat, the rate of change of the gap between the cone surfaces of the needle and the nozzle body, etc. allow describing the wear process of the mating parts. It is revealed that the wear of the surface layer of the nozzle parts is mainly due to the fatigue strength of the material.