| Hydrodynamic transmission is the kind of transmission which mainly makes use of the liquid kinetic energy. The hydrodynamic coupling is one kind of general hydrodynamic transmission part. It is installed between the engine and the working machine,transmitting their power. It can guarantee the flexible joint between the driveshaft and the driven-shaft , and transmits equally the torque for the driven-shaft from the driveshaft. The hydrodynamic coupling has the advantage of structure simple,performance reliable,energy conservation,improvement of transmission quality and so on. It is widely used in industries,such as shipping,metallurgy,power generation,mining,petrochemical,textile,lifting and transportation. To increase the performances of the hydrodynamic coupling and decrease the consumes of energy sources are important for the fuel economy, especially,today the energy sources are scanty in all of the world. In this paper,the advanced technique of Computational Fluid Dynamic(sCFD) has been used to calculate the two-phase flow of the partially filled hydrodynamic coupling,and then factors deciding the efficiency of the hydrodynamic coupling are found out by analyzing the calculated results. The performance of the hydrodynamic coupling is tested by using the test-bed experiments. The experimental data is analyzed and compared with the numerical results,and the results indicate that the numerical simulation method is correct.This paper mainly researches several aspects as the followings:①The computation models of the gas-liquid two-phase flow are introduced. Through the introduction of the two-phase definition and the characteristic as well as several numerical simulation methods of the two-phase flow,this paper elaborates three kinds of multiphase model in the CFD software,such as VOF model,Mixture model and Eulerian model. According to the method of selecting the multiphase model,the suitable multiphase model and model fundamental equations are foundation. The introduction of the two-phase flow provides the foundation for the numerical simulation.②The numerical simulation of the partially filled hydrodynamic coupling. Based on the elementary theory of the flow field numerical simulation,the Finite Volume Method is chosen to solve the equation. Second Order Upwind method is the way to accomplish the space discretion. SIMPLE,SIMPLEC and PISO are three strategies for coupling the pressure between continuity equation and momentum equation. For this paper , the SIMPLEC is more favorable. The k ?εtwo-equation model is used in the turbulence models. Actually the inner flow field of the partially filled hydrodynamic coupling is very complex , so some simplification and basic supposal are made before numerical simulation. First,the three-dimension geometric model and computational mesh model of the hydrodynamic coupling is finished. Then the model is computed in CFD software by using unsteady flow method,and sliding mesh model theory is employed to define the interface between the flow passages of the pump and turbine. The divided face of flow passage is defined as periodic boundary conditions. With the help of the CFD software,the flow characteristics of distribution in different working situation and different quantity of liquid are achieved after numerical simulation.③The analysis of the inner flow field in partially filled hydrodynamic coupling. Based on the numerical simulation results,this paper analysis the performance of flow field in pump and turbine in detail. In the pump,there is wide range secondary flow,because of the whirlpool in the viscosity cutting level,the flow deflection,the Coriolis force and the centrifugal force. There is high pressure region in the entrance region of the turbine blade and peripheral region because of the impact from the high energy liquid. Along with gear ratio elevation,the main circulation of the flow field between the pump and the turbine changes gradually from the turbine flow channel circumferential circulation to the majority of the flow channel axial circulation.④Experimental research and performance prediction in partially filled hydrodynamic coupling. The performance of the hydrodynamic coupling with different sufficient fluid rate is tested by using the test-bed experiments,and according to the experimental data the primary performance is computed. Contrast to the experimental data,the numerical results are high precision. The numerical results agree well with the experimental data,and the most tolerance is less than 10%. The method and theories of calculating the two-phase flow in partially filled hydrodynamic coupling are viable and right. The results of this paper are very valuable for the analysis of three-dimension two-phase flow field in hydrodynamic coupling. On the base of that,some further researches on the simulation of the hydrodynamic coupling can be well continued. |
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