Aerodynamic Drag Reduction Of Wheel And Heat Transfer In It

Research was carried out about the holes pass and structure of wheel spoke by aerodynamic theory. Based on the lightweight and conditions in a variety of conditions, the object of making the drag coefficient to minimize was implemented and the heat flow in the cooling effect of air was took into account. Theoretical basis of the holes pass and structure of wheel spoke was provided through the analysis of the relationship between aerodynamic drag reduction of wheel and heat transfer in it.In this thesis, numerical models coupled heat transfer and aerodynamics was analyzed by mathematical method for the independently rotating wheels and the brake disc in it. The perfect simulation model of dynamic wheels were founded,including: computational domain was defined,the form of frontal area,moving mesh with various body grid coexistence was adopted,convergence criterion with unsteady operation and small time step sizes was adopted in the dynamic simulation.In this thesis, the improvement was brought forward on models:①The parameters of actual use of wheels and brake disc was adopted to be the original parameters,the purposes is that making the selected wheel be representation and the model be consistent with the actual situation.②The program of moving mesh was adopted,computational domain was divided into several different domain,the interface was adopted t between different domain to ensure the data to change.③Processing of local details to the mesh and wheel deformation were adopted to the domain between wheel and ground,processing of local details to the mesh was adopted to the question of grid singularity in the holes of wheel spokes.④In order to realizing the condition of rotating wheels,the motion type of wheel was set up to the type of moving mesh. ⑤In the process of numerical simulation,combined with the actual situation of rotating wheels ,convergence criterion with unsteady operation and small time step sizes was adopted in the dynamic simulation to get the accurate results of the aerodynamic drag coefficient.In this thesis, aerodynamic drag characteristics and flow field was acquired by the analyzing the different shell form of independent wheels.①Drag coefficient of wheels without holes is higher than that of cylinder-shaped wheels by the effect of rim structure. The main structure of the regional impact is the internal structure of the wheel cavity.②In the premise of a fixed diameter hole,the way of moderate increase in the number of openings can reduce the aerodynamic drag coefficient. In the premise of a fixed number hole,the way of moderate increase in the opening aperture can reduce the aerodynamic drag coefficient.③In the premise of a fixed total opening area,the way of change in the number of openings can not have a larger influence of the aerodynamic drag coefficient.④In the premise of a fixed single hole of the opening area,aerodynamic drag coefficient of different opening form can be decreased with increasing the number of openings. But,in the premise of the same number of holes,aerodynamic drag coefficient can be decreased with increasing the number of openings due to the degrees of difference by opening form.The results show that: In a separate case wheels, the way of holes in wheel spokes can reduce the aerodynamic drag coefficient. The larger the openings, the better the effect of aerodynamic drag reduction. In the premise of a fixed total opening area,the way of change in the number of openings can not have a larger influence of the aerodynamic drag coefficient. The way of opening form changed can reduce the aerodynamic drag coefficient.The law of coupled aerodynamic characteristics and cooling characteristics was acquired by the analyzing the different shell form of independent wheels with brake.①The difference of surface static pressure distribution in the internal rim by the not opening wheel having a brake mainly comes from the domain of rim back side of gas to flow direction. The flow inside the rim area was divided into two different regions, one is the region surrounded with brake disc and wheel spokes, another is the region surrounded with brake disc and wheel rims. The former, flow disturbance within the region is not very strong by no holes in wheel spokes, the later, flow into the wheel rim does not form a strong vortex by with the brake.②When the opening form is hole, the law of coupled aerodynamic characteristics and cooling characteristics is different due to the region surrounded with brake disc and wheel spokes. When the flow field for the wide range of flow irregular disturbances is the main disturbance, aerodynamic characteristics and cooling characteristics show the same growth characteristics with less. When the flow field for airflow around the axis of rotation disturbances is the main disturbance, cooling characteristics of brake disc and the opening of the aperture only show the same growth characteristics with less, cooling characteristics of brake and aerodynamic characteristics are not necessarily linked.③In the premise of a fixed total opening area,coupled aerodynamic characteristics and cooling characteristics can not have significant changes with increasing the number of openings. The reason of flow field disturbance is the interaction of opening's irregular disturbance and disturbance around the axis of rotation, opening's irregular disturbance have no large extent affect.④In the premise of a fixed single hole of the opening area,aerodynamic drag coefficient of different opening form can be decreased with increasing the number of openings. But, rate of increase aerodynamic drag coefficient is not significant, the main reason is that affected by opening the flow area becomes very small due to having brake disc. The greater the irregular degree of the opening, the worse the cooling degree of brake disc. In order to ensure better heat dissipation, the inerratic holes form should be adopted as much as possible.The results show that: In a separate case wheels with brake disc, the way of holes in wheel spokes can not reduce the aerodynamic drag coefficient. The effect of heat dissipation can be increased with increasing the number of openings. In the premise of a fixed total opening area, the number of openings can not affect aerodynamic drag characteristics and the cooling effect of the brake disc. The way of different opening form can not reduce the aerodynamic drag coefficient, but the way of increasing the number of openings can increase heat dissipation.