| The working thermal fluids of loader cooling system flows through theradiators and conducts convection transfers with cooling air in the underhood,which maintains its temperature in the normal range to ensure the machine worksproperly. Therefore, the state of the air flow is very important to thermal balanceof loader. The cooling fan improves the air flow state and heat transfer effect,which develops the capability of loader and enhances the competitiveness in themarket. The performance of cooling fan is not only about a single structureparameters, but it is very about a good combination of structural parameters, agood relationship with radiators, and reasonably arrangement in loader underhood.Taking the above factors in account, This paper analyzed aerodynamiccharacteristics of cooling fan in the following aspects.Firstly, the poor state of air flow and the problem of vehicle thermal balanceare analyzed by the arrangement characteristics of a domestic loader underhood.It is analyzed that four common kinds of loader cooling fan and threedevelopment trends of cooling fan. The current state of cooling fan research isconcluded and the major studies in this paper are proposed.Secondly, The performance of cooling fan was analyzed by wind tunneltesting and numerical simulation method. By wind tunnel testing which wasestablished by cooling fan manufacturers, static pressure curve, power curve andstatic pressure efficiency curve of a cooling fan were measured and fitted underthe conditions of seven kinds of resistance states and six kinds of fan speed. Theperformance of the cooling fan was simulated and analyzed with numericalsimulation method at a fan speed of1800r/min, and performance curves werefitted compared with the test curves at the same time. The results shows that the numerical error is less than5%at high flow conditions, so the numericalsimulation method is feasible.Thirdly, through variable circulation design and improvement of blade skewangle, several new cooling fans were designed. By numerical simulation methodin a virtual wind tunnel model, pressure changes and axial velocity changes onthe outlet of the cooling fans were analyzed, as well as the static pressuredistribution of blade pressure surface was displayed. The results show that thecooling fan with circulation coefficient-0.1has small static pressure gradient ofblade and lower secondary flow loss, and compared with the cooling fan withcirculation coefficient-0.2, the static pressure increases28.94Pa, the totalpressure increases65.73Pa, the static pressure efficiency increases1.49%, and thetotal pressure efficiency increases5.74%at the same flow; at the improvement ofblade skew angle, it shows an appropriate skew angle can reduce blade tip lossand obtain a good performance of cooling fan, but it will increase blade root lossand lower pressure efficiency when the skew angle is too big. The author suggeststhe cooling fan at a skew angle of6°is better.Finally, for the heat-dissipation and engine underhood of the domestic loader,the influences of the distance between cooling fan and radiators, the distancebetween cooling fan and engine, different combinations of components anddifferent cooing fan speeds were simulated and analyzed in a virtual windchamber model with CFD method. The results show that the distance betweencooling fan and radiators has a little influence on air flow, and the non-uniformdistribution of cooling air has a big influence on resistance resistance of radiators,when the distance large than120mm, the non-uniform velocity coefficient and theradiator pressure drop have little change; as the distance between cooling fan andengine increases, air flow increases and the non-uniform velocity coefficientdecreases, when the distance changes from90mm to180mm, air flow increases16.60%and the radiator pressure drop increases22.39%; as cooling fan speed increases, air flow increases, backflow velocity of radiator inlet surface increasesand backflow area decreases, the performance of radiators are improved. |
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