Design And Numerical Study Of Pressure Amplified Diesel Injector

Common rail fuel injection system merges mechanic, computer controlling, theapplication of new material, advanced design philosophy and machining techniques,displays great advantage in achieving much higher pressure, flexibility and accuracy,making it one of irreplaceable means of reducing emissions of diesel engine andprotecting the environment. In order to meet much tougher emission legislation andreduce oil consumption, the combustion process should be further improved, whichmakes higher demand on fuel injection system. Pressure amplified common railsystem has better electronic control flexibility and pressure-time adjustmentcharacteristics, which possibly makes it a development trend of common rail fuelinjection system in the future.A new pressure amplified common rail fuel injection system based on Pascalprinciple is proposed, and the core component of the system–pressure amplifieddiesel injector（PADI） is designed innovatively. PADI comprises of amplificationmodule and injection module, which are controlled by solenoid separately and operaterespectively, thus making the hydraulic amplification process and the fuel injectionprocess independent of each other. Hence, PADI can work under two different modes,namely, common rail mode and pressure amplification mode. The newly inventedpressure amplified common rail injection system can achieve super high injectionpressure, and has better electrical control flexibility and pressure-time adjustmentcharacteristics.This paper focuses on the design of the newly invented pressure amplified dieselinjector. The design process, structure, composition and the working principle andprocess of PADI are stated in detail. Finally, experiment and simulation researches aredone aiming at pressure amplification module.In order to verify the feasibility of the design philosophy, a test bench comprisesof the pressure generating system, control system and data acquisition system wasdesigned aiming at amplification module. Based on the function, structurecomposition and the working principle of PADI, a one-dimensional simulation modelof PADI was established with software FLOWMASTER, and the simulation modelwas testified on the test bench. It was found that the response of Direction Change Valve had a great influence on the pressure amplified curve. So, The influence ofdesigning parameters such asA₁,A₂, the common rail pressurePrand the leakagecoefficient of Direction Change Valve on the response of Direction Change Valvewas simulated. The simulation results show that these designing parameters have agreat influence on the response of Direction Change Valve, and eventually on thetiming of the build of high pressure. In detail,T_o2andT_o3increase with the increase ofA₁andA₂, whileT_c2andT_c3decrease as A₁andA₂increase. andT_c2keep stable asP_rincreases,T_o3andT_c3decrease with the increase of P_r.T_o2keeps stable with theincrease ofλ,T_o3increases slightly asλ increases,T_c2andT_c3increase with theincrease of λ.