The Study Of Flow Characteristics And Control Optimization Of Pumping System For Volatile Liquid

The efficiency of the pumping system for volatile media like gasoline is generally low due to the low viscosity and easy vaporization of volatile media. Moreover, the porosity condition of the filter will change a lot(even blocked) frequently because of its long-time work without replacing or low cleanliness of oil in the actual oil station, which will make pumping system produce the problem of inefficiency and insufficient flow.In view of the above problems existing in the present volatile media pumping system, this subject firstly uses a combination of theoretical analysis, experimental measurements and numerical simulation to study the influence of the variation of the filter’s porosity condition on the flow characteristic of volatile media pumping system as well as its internal mechanism. Then this paper proposes some effective optimization methods based on present frequency conversion pumping system for volatile media to solve the problem of inefficiency and insufficient flow existing in the pumping system. Meanwhile, the operating efficiency of the pumping system under different operating conditions can be improved a lot as well. The main contents are as followings:Firstly, the efficiency model of the volatile media pumping system is analyzed. In order to explore the effects of variation of filter’s porosity on each internal leakage channel, a new three channel equivalent internal leakage model of EPZ vane pump is established, and the result indicated that the variation of the equivalent internal leakage in third channel caused by pump cavitations is the main reason for the low volume efficiency and insufficient flow of the EPZ vane pump. After that the effect of variation of filter’s porosity on the cavitations status in vane pump is deeply studied through experimental method, and then the different cavitations phenomenon can be distinguished from analyzing pressure fluctuation signal of outlet based on spectrum analysis and autocorrelation function method.Secondly, this paper mainly uses a combination of theoretical analysis, experimental measurements and numerical simulation to research the flow characteristics of volatile media in the filter. Through deducing further the contracting-expanding channel model and establishing the equivalent Reynolds coefficient, a comprehensive analysis of the flowing resistance characteristic for volatile media in the filter can be carried out. And then the internal flow characteristic of the filter is simulated further for three different flow states. The simulation results indicated that the flowing resistance characteristic for the volatile media in the filter,the void fraction in gas-liquid two-phase flow and the flow characteristic in solid-liquid two-phase flows with impurity particles will change a lot due to the variation of porosity, which will have dramatic effects on the performance of the pump.Then, an optimized design scheme of control model for present frequency conversion pumping system for volatile media is proposed based on above researches on the mechanism of flow characteristics. By means of parameter optimized design and experimental test,this best efficiency point control model is proved to be effective and practical in different working condition which including the variation of filter’s porosity condition. Furthermore, real-time monitoring and early-warning of the porosity condition of the filter on this optimized control model basis can be realized.Finally, an excess flow valve design scheme which can be applied in the gas-liquid two-phase flow with low void fraction is proposed to limit the maximum flow rate of the pumping system and realize the early-warning of the flow.