Investigation Of Spray Characteristics Of Gasoline Multiple Injections At Boundary Conditions Of Super-charge DISI Engine

Turbocharge and GDI is the main trend in developments of the downsized SI engine. However, both the narrow cylinder volume and the short duration of spray atomization and evaporation lead to the wall wetting and over inhomogeneous of stratified mixture, which cause lubricant dilution, fuel economy deterioration and emissions increase. It is effective to reduce the penetration by means of enhancing the charge density, which avoid the wall wetting. The multiple injections flexibly adjust the mixture quantity for different loads. The macroscopic spray characteristics were investigated under forceful gas-liquid interaction through enhancing the charge density. Investigation on the method of enhancing fuel efficiency and emissions characteristics was conducted by avoiding wall wetting and optimizing stratified charge mixture quality.In this study, one of the main missions is designed a new type of constant volume vessel based on the experimental research requirements. It included constant volume vessel body, ambient temperature and pressure control system, injection pressure control system and the most important is injector drive circuit. The constant volume vessel designed to meet the requirements of the spray and combustion test observation. It can set different ambient temperature and pressure boundary conditions within a certain range, and meet the capacity of the peak pressure in combustion test. Based on the control requirements of multi-holes GDI injector, besides the fast response and quick recovery performance requirements of injector drive circuit for multi-injection, designed the injector drive circuit by us. Through simulation and experiment determined the type and location of components, manufactured the PCB broad of final product. To ensure the performance of injector drive circuit is reliable and steady, the circuit was calibrated.In order to study the spray characteristics impact of different charge density and injection strategy. The spray characteristics of multi-holes GDI injector were investigated by the Schlieren images in a constant volume vessel. At the same condition of injection pressure, injected fuel quantity and ambient temperature, this paper discussed the penetration length, spray concentration distribution and spray velocity with respect to the influence of charge density and injection regularity according to the SAE-J2715criterion. Results showed that the penetration length deceased sharply when the ambient pressure increased, then it changed slightly when the ambient pressure increased further. The injection regularity not only impacts the penetration length, but also affects the spray concentration distribution. The penetration length deceased with the comment effect of the ambient pressure and injection regularity. Besides, the concentration of single injection spray front area was higher, the double injection spray was uniformity, and triple injection spray back area was higher. Therefore, the continuous multi-injection can form a high quality mixture palpably.