A Research On The Methods For Designing And Calculating Performances Of Engine Cooling Fans

Cooling fan is one of the important parts of the engine's cooling system, and its role is to keep the engine cooling. The power consumption of a fan accounts for 5% to 8% of the engine output power. The noise of the fan is also one of the major sources of vehicles. With the engine becoming more and more powerful, the engine's mechanical load and thermal load issues also become more prominent. Therefore, the higher requirements of the engine cooling fan are proposed: on the one hand, the cooling capacity of fan should be more powerful to meet the greater cooling system; the other hand, in order to reduce noise pollution, a lower noise cooling fan of radiation is required. So study the aerodynamic performance and noise of engine cooling fan is significant.Firstly, this paper describes the theoretical basis of the engine cooling fan design and performance analysis. Such as computational fluid dynamics (CFD), computational aero-acoustics (CAA), the working principles of a fan, and so on.Secondly, this paper describes the parametric design of engine cooling fan based on NURBS and completes the development of fan auto-modeling program. The parametric reconstruction of the airfoil and stacked lines for fan are achieved via NURBS. The engine cooling fan automatically modeling software was developed by using VC++. The result of reconstruction of certain airfoil and fan verify the accuracy and feasibility of parametric method and the software.Then, Modeling and solution techniques for estimating aerodynamic performances of engine cooling fans with a single blade are presented in this paper. The relations between static pressure, power consumption, efficiency and flow rate of a fan are calculated and validated with the experimental results. With the Large Eddy Simulation model in FLUENT, the noise levels of a fan under 11 rotational speeds are calculated respectively. It shows that the calculated values are about 10dB lower than the experimental ones, but the tendency of the two results is the same, which validates that the calculation model can be used in comparison between fans.At last, the theory of the orthogonal tests which play an important role in engineering is introduced. This paper selects airfoil setting angle, chord length, the height of the airfoil center line as the test factors through the analysis of the structural parameters of the fan. Using the parameters of the root and tip cross-section of the leaf, the orthogonal tests are performed and the modified design for the fan is achieved. Investigations on influences on the flow rates and noises are also performed. And the optimal parameters combination has been found. Aerodynamic performance has been greatly improved and the noise level is almost the same with the existing one, meeting the new requirement of engine cooling.