A Multi-dimensional Transient Numerical Study On Homogeneous Direct Injection Gasoline Engine

With the rapid promotion of car ownership, not only the limited petroleum resources are accelerating consumption, but also a formidable challenge for environmental protection being posed. The energy and emission saving are the main direction of automotive industry at the current day. Direct injection gasoline engine become the mainstream of development for its operation response and fuel economy.In view of the traditional engine development mainly rely on the experience of designers, its cost a lot of time and money, so the paper use computational fluid dynamics software STAR-CD analyzed a homogeneous direct injection gasoline engine, mainly studies the mixture and spray formation and combustion process.First, the constant volume spray simulation and a diesel combustion were analyzed to verify the reliability of spray and combustion model. Then the effect of nozzle angle and nozzle number to spray shape and penetration were researched. The results showed when the nozzle angle less than20degrees, the spray shape and penetration will be impacted greatly, and at the same circulation area the six hole nozzle will get a better atomization effect.Second, different nozzle angle with different injection start angle and different spark time schemes were discussed. Including established the moving grid, parameter setting, compute and visualization post-processing analysis. Through the analysis of the results shows that the smaller angle of the nozzle and horizontal, the larger cylinder tumble ratio will be got, turn the balance in favor the mixture formation and follow-up of the combustion process in low engine speed. But too small angle will allow the spray hit the back wall of intake valve to form a film and dilute mixture. The best angle should be the critical value that will not impact valve. In addition, the earlier the injection start angle, the more uniform gas mixture will be formatted and the pressure and temperature are more high. When the spark time is13℃A, we can get the highest thermal efficiency and the cylinder pressure curve is the most plump.