In order to study the effect of rail pressure

main injection timing

pre-injection timing and pre-injected fuel amount on the fuel consumption and NOx emission characteristics of the auxiliary power unit(APU) engine for an electric vehicle

according to the operating characteristics of the APU engine under different operating conditions

together with the vehicle's power demand and optimal operating area of the matched generator

the basic control strategy of multi-mode was adopted

and three steady-state operating points were selected as the operating conditions of the APU engine. Then

based on the space filled+V optimal design method

the hybrid test was adopted

and an engine performance and emission fitting model was established by using the regression calculation and neural network model. Under the given conditions of engine performance optimization conditions and optimization objectives

the normal boundary intersection optimization method was used to optimize the double target with minimum fuel consumption and NOx emissions

and the optimal fuel injection strategy for three steady-state operating points was determined. Results show that compared to the original engine

the optimized fuel consumption of each mode is reduced by 4.03% on average

and the average NOx emissions is reduced by 30.51%.