Application Of CAE Technique In Modification Design Of Diesel Engine

With the development of global industry, energy and environmental protection have become two main themes of the contemporary world. As the non-road machine widely used, the problem caused by non-road diesel engine emission has been widely drawing people's attention. Because the four-valve technology can improve the charging efficiency of engines, and make the injector decorated in the middle to create good conditions for fuel and air mixing, the diesel engine has good performance in economy, dynamic property and emission. The thesis applied CAE technology synthetically including one-dimensional and three-dimensional numerical analysis to study the numerical simulation research work of tetrofiting the TY495 two-valve diesel engine to four-valve diesel engine, which provided important theoretical basis to the diesel engine modification design optimization scheme.Firstly, the design scheme of the four-valve ports was determined, and a three-dimensional entity model including four-valve ports was built by using three-dimensional modeling software, and the flow in the ports was simulated by using the CFD fluid analysis software STAR-CD. Through the comparison and analysis of the two-valve and four-valve advantages and disadvantages, the structure characteristics of four-valve diesel engine were cleared. On the basis of Non-road diesel engine TY495, the design method of intake ports was investigated when four-valve technology was used in the TY495 diesel engine and intake-port layout scheme was put forward and the dimensions were gotten. According to the design size, the three-dimensional entity model of the intake and exhaust ports was built, and the software STAR-CD was used to simulate and analyze the flow characteristics of the intake and exhaust ports. Through calculation, it obtained the flow coefficient and swirl ratio of inlet ports, and the flow coefficient of the ports in different valve lift, for providing the parameters to the intake valve and exhaust valve model in the four-valve diesel engine simulation model.Secondly, this thesis established the calculation model of the non-road TY495 two-valve and four-valve diesel engine based on the software GT-POWER to analyze the influence of four-valve technology on the comprehensive performance of diesel engine and optimize the inlet pipe of diesel engine. According to simulation results, the performance of the two-valve and four-valve diesel engines, such as the power, torque, air flow and fuel consumption were compared and analyzed which provided important information to the retrofit design and comprehensive performance enhancement of the non-road TY495 diesel engine. According to the structure characteristics of the four valve diesel engine, and based on the analysis of the intake pipes arrangement effecting on the main performance of the four-valve diesel engine, the layout of the intake ports was determined and optimized.Finally, this thesis established the kinematics model of the valve actuating mechanism of the non-road TY495 four-valve diesel engine to design the cam contour by using the software AVL-Tycon, and it optimized the valve timing of the diesel engine based on the simulation model of TY495 integrated system. In the process of design, it designed the four-valve drive mechanism for a good economy on the manufacture and application, and used the High Order Polynomial Dynamic Cam (POLYDYNE) to the cam contour based on the kinematics model of the valve actuating mechanism. Based on the model of TY495 integrated system, the Design of Experiments (DOE) was utilized to analyze the intake and exhaust timing for optimizing the valve timing to improve the engine's comprehensive performance.