| The rapid development of roads and improvement of the quality of roads makethe percentage of vehicle transport increase in transportation. In recent years, the ac-cidents caused by braking failure and braking inefficiency are still accounted for asignificant proportion of all accidents. For that, the retarders are forced to be thestandard equipment for vehicles in abroad, whereas the eddy current retarders arepopularized only in motorbuses in China. Because the heat generated by the eddycurrent retarder (ECR) and new generation permanent magnet retarder (PMR) istransferred by air forced convection, the poor efficiency of heat transfer leads to thesevere fading of braking torque. Moreover, their structures are complicated. Besides,the braking torque of PMR is small, and its cost performance is low. All aspects aboveresult in the lack of satisfaction of the ECR and PMR for the needs of continuousbraking and large braking torque of heavy vehicles. Thus, research and developmentof new types of retarders for heavy vehicles are very important, and their characteris-tics are the ability of braking in continuous working conditions, large braking torque,simple structure and low product costs. It is significant to break the monopoly of re-tarders from abroad, popularize the installing of retarders in heavy vehicles, improvethe safety of heavy vehicles and prevent the travel accidents caused by braking fail-ures.The ECR and PMR generate braking torque by electronic field and magneticfield, so they are collectively called the “electromagnetic retarder”(EMR). There arecoupled fields including the electronic field, magnetic field, thermal field, flow fieldand stress field in the EMR, whereas most researches focus on sigle physical field andlittle on coupled fields. Besides, the researches on optimization of the retarder are lessrelatively.To solve the problems of severe fading of braking torque, complicated structureand low cost performance and so on, many new types of retarders were proposed inthis dissertation. Then a lot of analyses of multi-physical fields and their coupledfields, optimizations and experiments were reported in the dissertation. The mainchapters and contents of the dissertation are: The opening chapter summarized the functions of the retarder for vehicle, relatedlaws and regulations, classification and importance of this research, etc. The charac-teristics of ECR and PMR were compared. The present situations of these two retard-ers were described. Finally, to solve current problems, the contents and methodologiesof the dissertation were proposed.In chatper2, a coupled field analysis method was presented to obtain the brakingtorque of the new type liquid-cooled eddy current retarder with doubly salient polesstructure. Firstly, the basic structure and working principle of the new retarder wereproposed. Then a method to calculate the braking torque was presented. Thirdly, thestatic magnetic analysis model and flow-thermal coupled field analysis model werebuilt. After that, a coupled method of the flow-thermal-magnetic field analysis andbraking torque calculation was presented. Finally, the experiment method and proce-dure were introduced, and the comparision of the braking torque obtained by analysesand tests were carried out. Thus, a way was provided to compute the braking torque ofthe new retarder for further design and optimization.Chapter3was devoted to the optimization of the new type liquid-cooled perma-nent magnetic retarder (PMR-LC) based on the response surface methodology (RSM).At the beginning, the basic structure and working principle of the new retarder werepresented. Next, the transient magnetic analysis model of the retarder was establishedand the braking torque was calculated. Then, respectively, to maximize the brakingtorque (subjected to the product costs) and minimize the product costs (subjected to acertain braking torque demand), two approximating optimization models were builtby the RSM. Finally, the braking torque was increased and the product cost was de-creased under a certain braking torque demand. So, an effective way to optimize thestructure of retarder was proposed.Chapter4gave a thorough understanding of the characteristics of the mul-ti-physical fields in the PMR-LC, and the residual braking torque of a new type of re-tarder named rotor-liquid-cooled permanent magnet retarder (PMR-RLC) was calcu-lated. First of all, the thermal field, the magnetic field and the stress field analysismodels of the PMR-LC were built respectively. Firstly, the thermal field analysismodel of stator was established. The heat transfer theory was used to reasonably cal-culate the mean surface coefficient of heat transfer of the cooling duct and otherboundary conditions. The temperature distributions of the stator under the experiment conditions and working conditions in vehicle were analyzed. Secondly, the thermalfield analysis model of permanent magnet was built. Based on the results of thermalanalysis of the stator, the thermal boundary conditions were calculated reasonably,and the temperature distribution of permanent magnet under the experiment condi-tions and working conditions in vehicles were analyzed. Then, the static magneticfield analysis model of the retarder was established. Fourthly, the static structureanalysis model of the stator was built, and the boundary conditions of forces werecalculated based on the real working conditions. The stress field and displacementwere analyzed. Besides, the influence of geometry parameters of cooling duct on theefficiency of thermal transfer was discussed based on the heat transfer theory. Finally,the basic structure and working principle of the PMR-RLC were proposed. The re-sistance of the rotor in the cavity that is full of liquid was calculated. All analysesprovided the theoretical basis for further design and optimization of the new retarders.Chapter5mainly analyzed the features of the coupled field of the flow field andthermal field in the PMR-LC. Firstly, based on the experiments in a literature, thecharacteristics of three low Reynolds turbulent models named SST, SST-CC and BSLSMC were compared in the numerical simulations of heat transfer of a curved ductheated at outer curved surface. The feasibility of the application of three models in thecoupled analysis of flow-thermal field in the retarder was explored. Then, based onthe analyses of flow-thermal field in the retarder, the influence of rate of flow, thetemperature of liquid at the inlet, the height of duct and the height of conduction zonein the stator on the temperature of the stator and permanent magnet were understood.The research provided the theoretical basis for further design and optimization of heattransfer enhancement of the cooling duct in new retarders.In the final chapter, the performances of multi-physical fields of a new disk typeof permanent magnet retarder (PMR-D) and a new disk type of liquid-cooled perma-nent brake dynamometer (PBD-DLC) were analyzed, and the structure of PMR-D wasoptimized. After the basic structure and working principle of the retarder and dyna-mometer were presented, the transient thermal model of the magnetic equipment inthe retarder was built firstly. According to the thermal data in the tests of the retarder,transient thermal analyses were carried out with the boundary conditions of thermalconduction and thermal radiation. Then, the static magnetic field analysis model ofthe retarder was established，and the suction between the rotor and stator was calcu- lated by virtual work method. Based on the static magnetic field analysis, five param-eters of the retarder were optimized by the first order method. Finally, the static ther-mal analysis model of the brake dynamometer was built. The heat transfer theory wasused to reasonably calculate the mean surface coefficient of heat transfer of the cool-ing duct. The thermal field distribution was obtaioned and compared with the datafrom the experiments.The final part of the dissertation was the conclusion and the expectation of fur-ther researches in the future. |
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