Abstract: To improve the effect of energy-saving and emission-reduction of diesel engine, the brief analysis of the form and function of multiple injection is firstly made. Six typical working conditions of diesel engine for vehicle are determined based on operation in different road conditions, and then the distribution method of multiple injection is proposed based on the working condition emission limit. The emission limit value of typical working conditions is determined by the emission-sharing rate of the working condition and the injection times and injection combination solutions are optimized. Finally, combined with the bench test of 4JB1 high-pressure common rail diesel engine, taking NO_x and smoke as the evaluation parameters and taking into consideration of the change of fuel consumption rate, the influence of different injection combinations on the emission of diesel engine is analyzed. The results show that it is advisable to use two injections for idle speed and medium speed and heavy load conditions, triple injections for low speed and small load conditions and medium speed and medium load conditions, quadruple injections for medium speed and light load conditions, one injection for high speed and heavy load conditions, which shows that the distribution method of multiple injection based on the restriction of emission value is valid

Key words: diesel engine, injector, typical working condition, multiple injection, distribution