Development And Research Of Large-flow Common Rail Injector For High-power Density Diesel

Today’s rapid economy and productivity growth have created demands on the performance of diesel.Among them,the most important indicator for measuring the performance of diesel is the power density,thus the name of the high-power density diesel was born.In order to solve the urgent needs of the domestic high-power density diesel,it is necessary to study its key technology,high-pressure common rail injection system.Among them,the core of the high-pressure common rail injection system is the common rail injector,and common rail injector technology in China is relatively behind,so this thesis is devoted to the study of a common rail injector with high rail pressure,low delay and large-flow to meet current mainstream high power density diesel performance requirements.In this thesis,the Bosch 0445 B29081-00 common rail injector is tested on the EFS high pressure common rail test bench.The fuel injection characteristics and response characteristics are measured,then the Bosch common rail injector is disassembled,analyzed structure and principle.Finally I built a one-dimensional simulation model that the Bosch common rail injector is adopted as prototype machine by AMESim and compares the simulation results with the experimental results to verify the credibility of the simulation model.Through the simulation model,the influence of the key structural parameters of the common rail injector on the performance of the common rail injector is studied.Based on this,the structural parameters of the large-flow common rail injector meeting the performance requirements of the high-power density diesel are explored.And the first round of three-dimensional design was completed.Finally,on the basis of prototype machine,the transformation design and manufacturing are completed.The main contents of the research results are as follows:The methods for improving the fuel injection rate of common rail injectors include increasing the common rail pressure,increasing the number of nozzle orifices,increasing the nozzle orifice diameter,and appropriately increasing the needle valve lift.The methods for improving the needle valve response speed of the common rail injector include increasing the diameter of the oil inlet orifice,increasing the diameter of the oil outlet orifice.Ordinary common rail injectors cannot meet the demands of high-power density diesel due to the inherent defects of the ball valve structure,insufficient amount of fuel injection,and slow response speed.Therefore,the working principle of common rail injector is improved,including adopting the balance valve structure,increasing the number of nozzle holes and the diameter of nozzle holes,improving the lift of needle valve,increasing the diameter of inlet and outlet throttle holes and adopting the design of variable diameter.After multi-wheel simulation optimization,the structural parameters of the large-flow common rail injector are determined.Simulation results show that the large-flow common rail injector can complete fuel injection of280.476mm~3 within 1.3ms under the common rail pressure of 250MPa,the pressure loss rate is 5.324%,and the high-pressure fuel efficiency is 90.7%.This design solves the contradiction between needle valve response speed and high-pressure fuel efficiency,meets the demand of high-power density diesel,and provides a theoretical reference for the development of large-flow common rail injector prototype for high-power density diesel.