A Study On The Methods For Calculating Performances Of Engine Cooling Fans

Cooling fan is one of the important parts of the engine's cooling system, and its performances have important influence on the engine performances. Also, the power consumption of a fan accounts for 5% to 8% of that of an engine. The noise of a fan is also one of the major sources of noise inside and outside a vehicle. The design principles of engine cooling fans are meeting the cooling demands of a engine, improving the efficiency of fans and reducing the fan noise. With the continuously strict laws and increasing vehicle comfort people pursue, reducing the power consumption and noise of engine cooling fans are the priorities in vehicle design. As a result, improving the design level of engine cooling fans is an important research subject of the engine's cooling system.This paper explains the working principles of a fan, including velocities on an elementary stage, parameters of blade types and cascades and the aerodynamics formulas of cascades. The development process of aeroacoustics and classification and mechanism of fan noise are summed up. The development process of computational fluid dynamics(CFD), the modeling and solving of mathematical calculation formulas of flow fields and turbulence models are introduced. The characteristics of Fluent is also briefly introduced.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 caculated and validated with the experimental results. With the broad band acoustics model in Fluent, the noise levels of a fan under seven rotational speeds are caculated respectively. It shows that the calculated values are about 11dB 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.According to the design operating point given by the customer, the orthogonal tests are performed using a existing engine cooling fan. Investigations on influences on the flow rates and noises by hub ratios, chords and blade angles on the tip are performed. And the optimal parameters combination has been found. The flow rate of the optimized fan is improved by 8 percent, and its noise level is almost the same with the existing one, meeting the new requirement of engine cooling.