In order to research the cooling performance of engine water jacket, the CFD method and the software Fluent were used to analyze and optimize the capability. After building and meshing the three-dimensional jacket model, the coolant flow distribution and heat transfer coefficient distribution in jacket were obtained by simulating, and the deviation between simulation results and experimental data dose not exceed 5.3%. The current imbalance problem of heat transfer in water jacket was studied, and an optimization scheme was proposed according to the analysis of flow distribution in each cylinder water hole. The result of optimization program analysis and comparison indicates that the water jacket cooling performance has been significantly increased, the overall structure of water jacket is more reasonable, and these make engine get better cooling.

In order to seek methods of reducing the coolant resistance of radiators in mini-vehicle, the resistance distribution in minicar radiators was obtained by carrying out numerical simulation to coolant flow field of the radiators. The analysis indicated that the coolant resistance mainly composed of two parts: the resistance along radiating pipes, the inlet and outlet resistance of the water tank. Reducing the surface roughness of coolant pipes could lower the resistance along pipes. Slowing down the changes of the inlet and outlet section could reduce the local resistance.

To research the relationship between the coolant heat power and engine working conditions, and to guide the reasonable design of all heat-radiating components, an experiment method of heat balance at all operating modes was developed and implemented for a certain type of small gasoline engine. Based on the multivariate regression analysis, the correlation between the coolant thermal power and the engine rotation speed and torque was obtained. Tested by the experimental results and significant approach, the multivariate regression equations established have a high precision, and a certain theoretical and practical value for the cooling system analysis and design for small gasoline engine.

In order to study the cooling performance of cooling system of some subcompact, this article used GT-SUITE to build a one-dimensional model for it. Then the main factors for cooling performance were analyzed by the model, and some improvement measures were put forward after finding problems in the cooling system. The experiment data shows that the cooling performance has been significantly improved. At the same time, this research gives important technical parameters for the design and matching analysis of cooling system.

To get more appropriate louvered fin structure of a series of subcompact radiators, Fluent was used to analyze the subcompact radiator louvered fins numerically. The fin model was verified availably by testing the error between the simulation results and experimental ones. Through modifying the critical dimension of louvered fin models, the friction factor f and the heat factor j of subcompact radiator louvered fins under different fin height were obtained. The regression analysis indicated that the friction factor was linear with fin height, and the heat factor was the power function of fin height. The dimensionless parameter j/f1/3was introduced to evaluate the comprehensive performance of fins, and the research indicated that the performance would be best when the fin height was 8.94mm. The result has a certain practical value for improving the performance of subcompact radiators.