Research On Matching Design And Control Method Of Multi-fan Cooling Module

As the requirements of vehicle energy-saving and emission-reduction are gradually strengthened,it is an inevitable trend of the development of automotive technology that various functional components become controllable.Multi-fan cooling module(MFCM)with several non-polar speed electronic fans is one of the important products for a high-power commercial vehicle cooling system.Although MFCM has been preliminarily used in the commercial vehicle,especially in the rear-engine bus,but the key problems are still not systematically studied,such as the matching design,control strategy installation and layout in vehicle and so on.There are still bottlenecks in the application of MCFM.In this paper,the flow heat transfer law and basic control strategy of MFCM were studied by the numerical simulation method combined with the test method.MFCM installation and layout in rear-engine bus and fuel efficiency verification also been researched.The main research contents and major conclusions are as follows:1.Study on the numerical method of MFCM.The heat exchanger heat transfer model with the discrete method based on the hot side unit is established,the calculation accuracy is about 3%better than the existing heat exchanger heat exchange model.And this new model can be used to simulate the inside and outside flow field coupling heat transfer problem.At the same time,the influence of the rotation region selection and the turbulence model on the calculation accuracy of the cooling fan is studied in the fan MRF model.Based on the above method,a numerical method of MFCM was established,and the maximum calculation error is-5.68%.2.Study on the influence of the structural parameters of MFCM on the module heat transfer performance.Based on the numerical model of MFCM,the influence of key structural factors such as air flow direction,series-parallel arrangement and shroud structure on the flow and heat transfer performance of the module is studied systematically.The results showed that:the blow airflow is more favorable to the heat transfer efficiency of MFCM than the suction airflow.The parallel MFCM can realize the independent control of CAC and radiator while reducing the module size and weight,so,it's more suitable for MFCM.Among the shroud structure parameters,the area ratio and aspect ratio have the greatest influence on module performance.3.Study on the basic control strategy of MFCM.A MFCM performance testing platform was set up to study the basic control strategy with minimizing power consumption of the fan.The results showed that:the MFCM segmented control can achieve the minimum power consumption of the fan.Adding shutters in fan duct can enhance module cooling performance under some fans working conditions.Setting different speed of the fans located in low and high temperature zones can achieve better module performance than the same speed strategy.4.Study on the impact of the installation parameters of MFCM on the module performance in rear-engine bus.The influence of the parameters such as the cabin ventilation duct,grille type,grille slanting angle,grille opening ratio and the module mounting angle on the module performance are studied by numerical method.The optimization research was carried out by the response surface method(RSM).The results showed that:the guiding effect of the vertical grille is better than the cross grille.The optimal grille slanting angle is 30°.The bigger the grille opening ratio is,the better the ventilation effect is.The influence of the module installation angle depend strongly on the cabin structure.The difference is less than 1%between the RSM prediction value and the numerical test results.5.Study on the MFCM matching design method and the fuel-saving effect in real operation.The matching design method of MFCM with the numerical method as the main tool was put forward.The engine thermal equilibrium experiment was carried out to determine the heat transfer boundary condition of MFCM.The results of the fuel-saving effect of the numerical rmethod showed that:compared with the cooling system with traditional direct-connected mechanical fan and electromagnetic clutch fan,the cooling system with MFCM PID control algorithm can accurately control the coolant temperature and the intake air temperature respectively.So,the engine can work in the optimal working condition with the minimal fan power consumption.The results of the road fuel economy test and the actual operation fuel economy test showed that the rate of fuel saving of MFCM is better than 5%,compared with the cooling module adopted the electromagnetic clutch fan.