Research On The Multi-flow Field And Parameter Optimization Of Torque Limited Hydrodynamic Coupling

Torque limited hydrodynamic coupling is widely used in industrial machinery and equipment because of its reliable function, low price and simple maintenance. All kinds of torque limited hydrodynamic couplings have features which can improve the transmission quality and save energy. With the development of machinery and equipment in the field of industrial to the high-power, high-speed direction, correspondingly the performance of torque limited hydrodynamic coupling has been put a higher requirements. While the domestic research and development of torque limited hydrodynamic coupling are based on the Voith product, the independent research and development of key technologies are lacked. Meanwhile the theoretical research on torque limited hydrodynamic coupling is less, and the research on flow mechanism is not deep enough for its three-dimensional two-phase flow. In this paper torque limited hydrodynamic coupling that it’s cycling circle diameter is 560 mm with the front and rear auxiliary chamber has been studied systematically in terms of numerical methods,analysis of multi-domain coupling internal flow mechanism and characteristics prediction, bench test, multiple-objective optimization, and so on. The main research works and conclusions are as follows:1. The Methods of Flow Field Analysis for Torque Limited Hydrodynamic CouplingIn the calculation process of CFD simulation for torque limited hydrodynamic coupling, the turbulent model and two-phase flow model have great influences on the calculation results. The standard k-ε model was selected as the turbulent model for numerical simulation of limit torque hydrodynamic coupling by comparing the torque limited hydrodynamic coupling’s flow field calculation results and computation period of three kinds of turbulent model DNS model, LES model and the standard k-ε model. Through analyzing the adaptability, advantages and disadvantages of two-phase flow model such as VOF model, MIX model and the Euler model, the VOF model is selected for circulation characteristics analysis of torque limited hydrodynamic coupling, the MIX model is chosen for analyzing the pressure and velocity in torque limited hydrodynamic coupling’s flow field and its original characteristic is predicted.2. The Numerical Calculation and Results for Multi-flow Coupled Field of Torque Limited Hydrodynamic CouplingThe multi-flow domain is formed by the working chamber, front auxiliary chamber and rear auxiliary chamber of torque limited hydrodynamic coupling, and the purpose of limiting moment can be achieved by changing the circulation patterns of working fluid in the multi basin. To investigate its circulation patterns and flow mechanism, the three-dimensional model of limit torque hydrodynamic coupling is established. And the three-dimension geometric model of the impeller passage is extracted and meshed. Finally, CFD simulation was analyzed and calculated. The VOF model is used to track the two-phase distribution interface of torque limited hydrodynamic coupling. And the circulation patterns are analyzed under different charging ratio at three typical working conditions of axial plane, blade pressure surface and blade suction surface. Both velocity of axial surface and pressure distribution of torque limited hydrodynamic coupling are obtained by the MIX model, and the flow mechanism of hydrodynamic coupling is analyzed and its original characteristic is calculated.3. The Bench Test Research of Torque Limited Hydrodynamic CouplingThe torque limited hydrodynamic coupling has been tested by using hydrodynamic transmission test bench. Torque values at 19 conditions under three liquid charging ratios(q=0.4, q=0.625 and q=0.8) and speed ratios i(28)0 ~0.96 were measured, and then the original characteristic curves of the torque limited hydrodynamic coupling are fitted by handling torque values. The predictive veracity of the torque limited hydrodynamic coupling with the MIX model is analyzed by comparing the original characteristic curves of simulation with MIX model to the test curves.4. The Multi-objective Optimization Design for Torque Limited Hydrodynamic CouplingIn order to obtain better performance, the structure of hydrodynamic coupling is optimized. Many parameters can affect the performance of torque limited hydrodynamic coupling, parameters which are obtained by the traditional design method may not achieve the best performance of hydrodynamic coupling, so parameters of global optimization is necessary to find the optimal parameter scheme. The overload coefficient and pump torque coefficient of hydrodynamic coupling are regarded as the objective function. The design variables are selected and the corresponding constraints are given. Firstly the experimental sample points and detection sample points are got by taking advantage of Latin hypercube experimental method, then the agent model is builded by utilizing radial basis function(RBF) model, finally the optimization calculation is conducted by making use of NSGA-II(NonDominated Sorting Genetic Algorithm). It is showing that the torque limited hydrodynamic coupling optimized ability of overload protection is improved and the ability of transmission torque is appropriate by comparing before and after optimization overload coefficient and pump torque coefficient of torque limited hydrodynamic coupling.