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A commercially available computational fluid dynamics (CFD) code was tested for feasibility of application to automotive engine-cooling fans. Presence of the fan housing (shroud) and engine block makes the problem complex, as the computation has to deal with both stationary and moving frames of reference. One foreseeable benefit of CFD is the reductionæif not eliminationæof the number of prototype fans to make and test, in order to determine the design. Numerical experimentation could be carried out, in place of actual testing, to arrive at the optimum design. A couple of existing fans were chosen to assess the capabilities of the CFD code, and performance predicted. The computa- tional model is a fan set up on the fan wind tunnel. While predictions of the static pressure curve saw generally good agreement with measurements, those of fan torque suggested room for further improvement.

Vibration and fatigue study of glass-reinforced nylon, as an alternative material to steel for engine driven fans, is discussed. The use of nylon, which has a lower density than steel, offers a significant weight reduction and consequently less burden on the related underhood components and result in longer life for water pumps, fan clutches and drive belts. The temperature and humidity-dependent properties of nylon fan often works favorably from the view point of fatigue life, by shifting the fan's natural frequencies away from the occurrence of resonance. Nylon fans also offer more design flexibility without significantly affecting the cost. Despite such apparent advantages very little literature in the automotive field has dealt with vibration and fatigue of nylon fans. In this paper, computer-based finite element method (FEA) is used as the analytical tool to determine the frequencies and stresses produced at different values of temperature, humidity, and vibration excitations.

In this paper a method of research approach adopted by USUI International Corporation (UIC) for structural analysis of automotive plastic fan is described. The fan material used and perfected by UIC for engine-driven fans is polypropylene. The analysis is carried out by finite element method and complemented by experiments in some cases. Structural analysis procedure specific to automobile engine-driven fan is described. Polypropylene fan offers several advantages over other plastic/metal fan. Polypropylene is lightest of all plastics having specific gravity of 0.9. However plastic fans pose certain challenging structural problems. Plastic properties such as modulus of elasticity are temperature dependent and properties detoriate with increase in temperature. Also continuous or repetitive loading of plastic fan over the period of life of fan results in creep of plastic material at high stress areas on the hub of fan. In actual practice plastic fan with molded-in steel insert is used.