Fan shroud is one of the critical components in an engine cooling system. It helps in achieving optimum air flow across the heat exchangers. The major challenge is to design a fan shroud which meets noise, vibration and harshness (NVH) requirements without compromising on air flow targets [1]. An improperly designed fan shroud will cause detrimental effects such as undesirable noise and vibration, which will further damage the surrounding components. In current days, multiple simulations and test iterations are carried out in order to optimize its design. The objective of this paper is to provide a design framework to achieve optimized fan shroud that meets NVH requirements in quick turnaround time using Design for Six Sigma (DFSS) approach [2].
The purpose of the Engine cooling system is to maintain the coolant temperature across the vehicle. Fan shroud accommodates the fan which in turn provides necessary air distribution across the radiator in order to have effective engine cooling. In this paper, DFSS approach is adopted to identify and optimize the factors which govern the NVH design of fan shroud. DFSS approach - nominal the best is used for this analysis which has an output, control factors and the noise factors. The modal frequency of the fan shroud is the output from the analysis and is evaluated in two modes, flexible mode and pumping mode. All the design parameters such as wall thickness, number of ribs, structural embossing which affects the output are considered as control factors. The under hood air temperature and the reduction in structural rigidity due to aging are considered as the noise factors.
L18 Orthogonal experiment is used for this analysis, 18 design models are created in order to capture different combinations of control factor levels. Multiple control factors are examined to find out which would actually controls the designing of fan shroud in NVH perspective .Structural embossing and number of ribs for fan support are found to be the important design factors which contribute to better shroud NVH characteristics. A CFD simulation is also carried to check the airflow rate of the optimized design. The optimized design suggested in this paper had met both NVH and CFD targets. This study can be used further in order to reduce weight of the shroud and as best practice guidelines for future vehicles fan shroud designing which would ultimately reduce development time and cost.