3D Numerical Simulation Of In-cylinder Flow And Spray Process In Non-road Diesel Engine

The major power of non-road motor vehicles is diesel engine. As people pay more and more emphasis to energy and environmental protection, our nation has established strict non-road diesel engine emission regulation. To satisfy the more and more strict emission criterion, it is necessary to take measures to reduce the exhaust emissions of non-road diesel engine. For small non-road diesel engines, optimized matching among the fuel injection, in-cylinder air movement and the combustion chamber is an important means to reduce exhaust emissions. With the development of numerical simulation, people can penetrate deeply in studying the in-cylinder flow and injection process, and can assist to the optimization design of combustion system. In this thesis, simulation on intake and injection process of the TY3100 non-road diesel engine was carried out by using CFD software STAR-CD.Firstly, the three dimensional entity including intake and exhaust port, cylinder, combustion chamber was established by using reverse engineering and 3D drawing software. Then the three dimensional dynamic mesh model was built by ES-ICE software. 1D software GT-POWER was also used to provide boundary conditions and initial conditions for the 3D model.Secondly, the intake and compress process were simulated, the flow field, temperature field, pressure field distribution were discribed, the parameters such as turbulent energy and swirl ratio via engine crank angle were calculated. Research was focused on the flow movement in intake port and in-cylinder, and the turbulent flow during compress stage. Analysis was emphasized on the effects of spiral intake port shape and eccentric location of combustion chamber to in-cylinder flow. The results showed that the flow movement became vortex motion from disorder motion. There is a flow intersection in the spiral intake port, which increases flow resistance. Dumbbell combustion chamber can obviously increase the intensity of swirl in cylinder, and the combustion chamber located eccentricly can make in-cylinder flow asymmetry, which make against fuel-air mixing process.Thirdly, the injection process was simulated. Research was focus on the atomization progress of fuel spray, and the movement of gas mixture. Analysis is emphasized on the effects of injector position, swirl intensity to fuel injection etc. The research showed that because of the position of nozzle tip and combustion chamber, the spray penetration of every spray hole was different. So was the fuel injection process. The fuel distribution in combustion chamber was extremely heterogeneous.In addition, the effects of the combustion chamber shape on flow and spray process were discussed. In allusion to widely used dumbbell-shaped combustion chamber, three schemes were designed. Analysis was emphasized on the effects of combustion chamber structural parameters to swirl characteristic, Squish movement, atomization. A better one among these three schemes was chosen by comparing the simulation results, which has been proved to make a better emission quality by engine emission testing. The simulation has deepened author's cognition of flow field and fuel atomization of diesel engine. The results can provide references for further improvements to the TY3100 engine.