Research On Heat Transfer Characteristic And Simulation Model Of Transient Temperature Of Braking Resistor

With the rapid development of economics and society, The high-speed locomotive is more and more common in each big city; In the movement process, the high-speed locomotive will be accelerated or decelerated frequently, so it is needed to have a good braking performance and stability. At present, the resistance braking is widely used in high-speed locomotive. In order to prevent resistor from being distorted or even being damaged due to the excessive high temperature, the transient temperature of the resistor must be predicted accurately and monitored to ensure the safe and reliable operation of locomotive. Based on the numerical analysis of heat transfer characteristics of the resistor, the simulation model of the transient temperature of the resistor was proposed and the corresponding simulation software was developed, which provides powerful theoretical foundation with the thermal design of the braking resistor.In the thesis, the heat transfer process of the braking resistor was analyzed, the corresponding two dimensional model was proposed and solved numerically. The standard k-εturbulent model was employed to compute the turbulent developing and heat transfer in the parallel channel between the resistor band. The computation region was discretized with the quadrangle meshes, and the turbulence close to the wall was treated by employing the wall function method. The numerical computations for different conditions were performed, the corresponding heat transfer empirical criteria were deduced with the computed results, which was compared with the empirical criteria for developing turbulent heat transfer problem with the flow being developed.Then the simulation model of the transient temperature of the resistor was proposed based on lumped parameter system method, and the corresponding simulation computational procedure and software were developed, by which the transient temperature was simulated for a running condition of the braking resistance of Nanjing subway. The highest temperature and the time occurred that were closed the actual data very much, which implies that the simulation model is correct and can be used to predict the transient temperature variation of the braking resistor.Finally, the three-dimensional model of flow in the resistor cabinet was proposed to investigate the velocity non-uniformity in it. The corresponding mathematical model was solved numerically by employing the control volume finite element method, in which the convection item of the governing equations was discretized with second-order upwind scheme, the diffusion term was discretized with the linear interpolation multinomial, and the coupling of pressure and velocity variable was calculated by the SIMPLE algorithm. The numerically computed results revealed the flow fields for the case with and without baffle on the outlet plane of fan, and the corresponding velocity into the cabinet was obtained, which provides theoretical instruction for thermal design of the braking resistor.