Numerical Simulation For Effects Of Fuel Injector Parameters On Combustion And Emission Of DI Diesel Engine

The combustion process and emission characteristics in DI diesel engine mainly depend on the mixture formation in cylinder. Spray characteristic is an important factor which affects the mixture formation and combustion process. Further, parameters of the fuel injector directly influence the spray characteristic. Therefore, the study of effects of fuel injector parameters on combustion and emission of DI diesel engine is a meaningful work.The three-dimensional numerical modeling of engine combustion process is introduced in this paper. The turbulence models, diesel engine spray models and combustion models are explained in detail. The in-cylinder turbulence flow, spray and combustion process of 135 diesel engine are simulated by three-dimensional CFD package-AVL FIRE 8.5. Effects of the main parameters of fuel injector, such as number of nozzle holes, nozzle hole angle, injection timing and arrangement form of nozzle hole, are analyzed. Flow evolution process, spray distribution, fuel/air ratio equivalence ratio distribution, temperature distribution and emissions formation are analyzed detailedly. Through comparing with experimental results, calculation models are proved to be reasonable and simulation effectively predicts the emission.The results show that: number of nozzle holes has a great effect on spray atomization and fuel-air mixture; nozzle hole angle influences spray distribution; injection timing effects ignition delay period; the nozzle, which has two row and staggered nozzle holes, can enlarge scope of spray distribution and avoid impingement between two sprays. Mixture formation quality can be improved if selecting the above parameters appropriately, and therefore combustion process will be improved and emissions will be reduced.