Research On Hydrodynamic Retarder With Double-row Blades And Its Control System

Speed control and braking of vehicles are extremely important for driving safety. As anauxiliary braking device, the hydrodynamic retarder is characterized by the large high-speedbraking torque, the smooth and comfortable braking process, the good heat dissipationperformance and constant braking speed, so that it has been widely used. The standard in thetransportation industry requires clearly that the extra large passenger buses, the large passengerbuses of the higher level1, higher level2and higher level3and the medium-sized passengerbuses of higher level2must be installed the retarder device. More than60%of the heavytrucks were installed the hydrodynamic retarder although there is no compulsory execution.Foreign auxiliary braking device of vehicles mainly include the eddy current retarder and thehydrodynamic retarder, and the hydrodynamic retarder accounts for98%market shares. Withthe development of the heavy trucks and the large buses, the market requires the superiorhydrodynamic retarder with the higher capacity, smaller size, and faster response. Around thenew requirements on the hydrodynamic retarder, in this thesis, the systematic study of thehydrodynamic retarder was carried out in terms of the structure design and multi-objectiveoptimization, the analysis of the internal flow mechanism and improvement of the mechanical-electrical-hydraulic control system. The main research works and conclusions are listed asfollows:1. Structure Design and Multi-objective Optimization of the Hydrodynamic Retarderwith Double-row BladesThe structure of the hydrodynamic retarder was improved based on a single-row one. Theradial space was made full use, and the axial space was shortened accordingly, then a new typeof the hydrodynamic retarder with double-row blades was designed. There are manyparameters can affect the performance of the hydrodynamic retarder, and every parameter hasan optimal value range respectively. The hydrodynamic retarder with double-row blades thatwas designed according to the empirical parameters would not be able to achieve the best performance, so it is necessary to optimize the parameters of the hydrodynamic retarder withdouble-row blades to find the optimal design scheme. The braking torque and the capacity ofthe hydrodynamic retarder with double-row blades were confirmed as the objective functions.The design variables were selected by considering the real work conditions and requirements,at the same time, it also need to meet the structure of the hydrodynamic retarder with double-row blades. And according to the research experience on the hydrodynamic retarder, theconstraint conditions were determined. The sample points were obtained by using Latinhypercube sampling, and the surrogate model was built by using radial basis function. Bycomparing three frequently-used algorithm of multi-objective optimization, the non-dominated sorting genetic algorithm-II was selected to do the multi-objective optimization ofthis paper. Moreover, by comparing the braking torque and the capacity of before and afteroptimized hydrodynamic retarder with double-row blades, the results show that the brakingperformance of the optimized hydrodynamic retarder with double-row blades promotesdrastically and the capacity declines within a narrow range.2. The Flow Mechanism Analysis and The Braking Performance Comparison of TheOptimized Hydrodynamic Retarder with Double-row BladesThe different filling ratio and the different rotational speed conditions of thehydrodynamic retarder with single-row blades and the optimized hydrodynamic retarder withdouble-row blades were calculated. The velocity distribution and the pressure distribution ofthe optimized hydrodynamic retarder with double-row blades on the axial section, the bladepressure surfaces and the blade suction surfaces were analyzed under one condition of thesame rotational speed and the different filling ratio, and the other condition of the same fillingratio and the different rotational speed. By comparing the braking performance of thehydrodynamic retarder with single-row blades and the optimized hydrodynamic retarder withdouble-row blades, the results show that the braking performance of the optimizedhydrodynamic retarder with double-row blades is more superior to the hydrodynamic retarderwith single-row blades.3. Analysis and Modeling of the Control System of the Hydrodynamic Retarder withDouble-row Blades The flow characteristic of the hydraulic control system was analyzed to find theparameters that can affect the charging time of the hydrodynamic retarder. By improving thecontrol valve structure of the hydrodynamic retarder and the control signal of outlet throttlevalve, these influence parameters were adjusted to improve the response speed of thehydrodynamic retarder. The pressure flow characteristic and the valve core dynamicequilibrium equation of valves in the hydrodynamic retarder control system before and afterimproved were analyzed respectively. The simulation model of the electro-hydraulicproportional pilot valve, the hydrodynamic retarder, the control valve before and afterimproved hydrodynamic retarder and the hydraulic control system before and after improvedwere built respectively.4. Mechanical-electrical-hydraulic Joint Simulation Analysis in Dynamic Liquid-filled Process of the Hydrodynamic Retarder with Double-row BladesThe hydraulic control systems before and after improved were simulated jointly toextract and analyze the inlet and outlet flow of the hydrodynamic retarder with double-rowblades, the inlet and outlet flow difference, the charging time and the inlet flow of thelubrication device of the transmission. The inlet and outlet flow of the hydrodynamic retarderwith double-row blades, the inlet and outlet flow difference, the charging time, the inlet flowof transmission lube system of the control system of hydrodynamic retarder with double-rowblades before and after improved were analyzed comparatively, the results show that theresponse speed of the improved control system is rapider than that before improved, and theflow rate of shunt section in the improved control system was increased and there is a littleeffect on the changing speed and the time to reach steady state for the flow rate of othersections.