| At the present time, traffic accidents are happening with frequency in China. And acertain proportion of the accidents are caused by the failure of brake system, so the vehicle’sbraking performance received special attention of human. The appearance of the hydraulicretarder greatly improved the vehicle braking performance and strengthened the drivingsafety. This is due to the retarder has the following characteristics: vehicles generated biggerbraking torque when they drive at high-speed; the vehicle security for a long time continuousbraking is improved; the working life of the service brake system is extended; the brakingcomfort and environmental protection performance are improved. A hydrodynamic retardermainly consists of oil work cavity, cooling system, air intake system and electronic controlsystem. When the hydraulic works, it transforms the kinetic energy of vehicle into heatenergy of the work oil. With heat conduction of the work oil and through the cooling systemit will let the heat release into the air to reach the purpose of auxiliary braking.The research of the retarder internal flow field is not deep enough in domestic, Thereforethis paper based on the computational fluid dynamics proceed the numerical calculation ofthe internal flow field of the retarder and make depth analysis of its distributioncharacteristics. Using brake torque, brake torque coefficient and oil-filled time as theevaluation index to optimize the structural parameters of hydraulic retarder. The mainresearch contents have the following three aspects:1. Number Calculation and Analysis of Internal Flow Field of Hydraulic RetarderThe three-dimensional geometric model of the working flow pass of the hydraulicretarder is established. Then the grid model is established using the Gambit software. Theboundary conditions, initialization conditions and convergence criteria are set. The internalflow field of the hydraulic retarder using number calculation is analyzed. The methods of thenumber calculation are the RNG k εmodel, wall function method used in near-wall ofthe flow field, SIMPLEC algorithm, sliding-grid method used in interface between the stator and rotor. The chord coordinate, nodle coordinate and wing coordinate are defined in orderto analysis the internal flow field of the stator and rotor conveniently. The pressure field andrelative velocity field of the chord surface, nodle surface and wing surface of the stator androtor are analyzed. The flow field of the inside ring and outside ring are analyzed too. Theinternal flow field distribution law of the hydraulic retarder is revealed and the typicalproblems discovered.2. The Experimental Verification of Hydraulic RetarderThe performance test of the prototype retarder is performed on hydraulic transmissiontest bench. Then the number calculation result and test result are contrasted. The errorsbetween simulation and test are within the allowable engineering range, which proves thatanalyzing the internal flow field performance of hydraulic retarder using the numbercalculation is trustworthy.3. Structural Parameters Optimization of Hydraulic RetarderIn order to solver the typical problems which are discover in analyzing the internal flowfield, some structural parameters of hydraulic retarder are optimized. First in order to makethe vortex in the middle chord face of the stator flow pass near outside ring weakened, theblade parameters are optimized. Second the oil inlet and outlet parameters are optimizedbased on the blade parameters optimization in order to make the flow separationphenomenon of the outside ring face in the stator and the secondary flow near the oil outletweakened. Then the structural parameters of the inside flow pass are optimized in order tomake the big vortex weakened and narrow the gap of relative velocity in different oil inlet.At last the brake performance of the hydraulic retarder based on the prototype retarder andthe optimization are contrasted and analyzed. |
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