Numerical Studies Of The Transient Convection Heat Transfer Coefficient Of The Surface Of The Rolling Wheel

The high speed and overloaded put forward the higher requirements on the train speed and axle load, and the wheel failure problem has become increasingly serious which caused by the wheel/rail wear, fatigue and thermal damage. Moreover, the friction heat generated by the relative sliding between the wheel/rail is the main reason for wheel/rail thermal damage. As we all know, the wheel/rail friction heat production area is very small, so the temperature of the surface of the wheel soared rapidly, which influences the performance of the wheel material, the wear of the wheel/rail, the thermal stress, the creep rate and adhesion coefficient, to bring a big hidden trouble for the safety of the train. The transient convection heat transfer coefficient of the wheel surface plays a decisive role for the temperature distribution of wheel surface and the law of the fiction heat transfer. The convection heat transfer coefficient provide the theoretical basis for studying the relationship of the wheel/rail.This paper use the Fluent software to analyze the convective heat transfer characteristics of the ambient air and the wheel. The standard k-ε and RNG k-ε two equation turbulence model and the standard wall function method are introduced detailed. The structure grid is used to discrete the flow area of wheel/rail. The average and the distribution of the transient convective heat transfer coefficient of the surface of the wheel were obtained. The main research results are as follows:(1) The increase with the speed of the average convection heat transfer coefficient of the surfaces is approximately linear. The average convection heat transfer coefficient of the surface of flange is maximal, the next is the inner surface of wheel, the outer surface and tread the average convective heat transfer coefficient is minimal.(2) According to experimental values, it is found that the simulation results of lateral surface number Nu highly agree with the experimental values, but the tread and flange alignment is low.(3) In the contact region of wheel/rail, the convection heat transfer coefficient of the tread has a drastic change. The convection heat transfer coefficient of the curve between 265° to 270° is kept higher value, and then reduces quickly towards both sides.(4) The convection heat transfer coefficient of inner surface is at a higher level when the radius between 0.22 m and 0.28 m, and then reduced gradually both sides.(5) In the windward area, the convection heat transfer coefficient located the small radius at outer surface is larger than the big radius. On the contrary, in the wind shadow area, the convection heat transfer coefficient located the small radius at outer surface is smaller than the big radius. In radial direction, it is a inflection point for the variation of the convection heat transfer coefficient when the radius equal to 0.15 m. Before this point, the convection heat transfer coefficient of the four curves has the same change trend, after the inflection point, the convection heat transfer coefficient has the different change trends.(6) Based on the ratio of the maximum and the minimum about different surface convective heat transfer coefficient, it is found that the change of the surface of the tread is most intense, next is the inner surface times, the change of outer surface and wheel rim is minimal.(7) According to the tread and flange surface area in the wind area, the wind shadow area and the contact area of convective heat transfer coefficient is the ratio of the maximum and minimum values can be found that the contact area change is the most severe, followed by the wind shadow area, the minimum of the windward area.