3D Numerical Simulation Research Of Spray And Combustion Process In TY3100 Non-road Diesel Engine

Diesel engine is widely used in non-road machinery, due to high thermal efficiency and good economy. Diesel spray and combustion is the core of its working cycle, which directly affect the engine's power, economy and emission performance. Thus, in order to meet the increasing stringent emission standards, optimization of spray and combustion process of non-road diesel engine has a very important significance under the pressure of energy crisis and environmental protection.Compared with the experimental research, multi-dimensional numerical simulation of spray and combustion in internal combustion engine has some advantages in the predication of engine performance, easy data acquisition, reduction of development cost and shorter development cycles. So it widely adopted to investigate the complicated spray and combustion process of diesel engine. In this thesis, based on the analysis of domestic developments and numerical model of numerical simulation of diesel engine spray and combustion, the numerical simulation of spray and combustion process of the direct injection TY3100 non-road diesel engine was carried out by using CFD software.Firstly, the three dimensional computational model of spray and combustion process of the TY3100 diesel engine was established. In the process of establishing the calculation model, it was mainly focused on studying the effects of computational mesh and empirical parameter Aebu of EBU LATCT combustion model on the numerical simulation results of diesel spray. Among them, the entity model including intake and exhaust ports, cylinder, combustion chamber was established by using 3D drawing software UG. Then, the moving mesh model was built in STAR-CD by using ES-ICE software. 1D software GT-POWER was also used to provide boundary conditions and initial conditions for the 3D model. The research showed that the computational mesh and the empirical parameter Aebu of EBU LATCT combustion model mainly affected the spray and combustion simulation results. As the mesh refinement, spray jet velocity and spray penetration increased and the geometric shape of spray became slim, and the mesh scheme D was suitable for the research of the spray process simulation. The combustion reaction rate was increased with the increase of Aebu parameter, and value 4 for the Aebu was used in the simulation.Secondly, simulation works of original machinery spray and combustion process of TY3100 non-road diesel engine were carried out. The in-cylinder gas fluid, spray and combustion process, and concentration were predicted. The research showed that the fuel concentration distribution was apparent uneven among every spray hole as the combustion chamber located eccentrically. Lower fuel injection pressure led to the poor quality of fuel atomization, and decreased the air utilization rate in the pits area of combustion chamber. The NOx was generated in the pits and above area of combustion chamber with high temperature and oxygen-enriched, and the SOOT was generated in the area between the combustion shrink mouth and cylinder head. According to the analysis of the calculation result, it was better to make the evaluation and improvement for the original combustion system.Finally, the effects of fuel injection pressure and combustion chamber geometry on combustion and emissions of a diesel engine were investigated. After the injection pressure increasing from original 60MPa to 120MPa, improved the atomization quality, increased the area of fuel distribution, the combustion temperature, and the air utilization rate in the combustion chamber. Meanwhile, SOOT emissions reduced and the NOx emissions increased, but the reduction ratio of SOOT is larger 13% than NOx increase ratio. In addition, in order to match the increased injection pressure, three different shapes of combustion chamber were designed on the condition of the original compression ratio remains unchanged. And the effects of combustion chamber geometry on mixture formation and combustion quality were investigated. The results showed that chamber B possesses a better swirl intensity retention, stronger squish and higher turbulence kinetic energy, contributing to a better combustion situation and a good compromise between the soot and NOx emissions.