Research On The Gas-Liquid Two Phases Flow Characteristics And Impeller Optimization Of Tesla Disc Pump

Tesla disc pump,invented by Nikola Tesla,has a bladeless area inside,which makes the flow passage of impeller is wide.Because of the unique impeller structure and working mechanism,the disc pump is widely used in petrochemical,medical,food,multiphase flow and other fields.However,there is still a huge room to improve the working efficiency of the disc pump,so it is of great academic and engineering value to study the design method of the disc pump which not only retains its own characteristics but also makes the performance highly efficient and stable.The research methods of numerical simulation and experimental test are used to reveal the influence of inlet gas void fraction(IGVF)on the performance and internal flow characteristics of the disc pump under the gas-liquid flow condition.Through the response surface optimization method,the influence of the impeller structural parameters of disc pump on its performance is analyzed,and the optimal combination of the impeller structural parameters is obtained.The specific research contents of this paper are as follows:(1)Experimental study on the disc pump under the condition of gas-liquid two-phase flow were carried out.The influence of rotational speed,flow rate,inlet gas void fraction and other factors on the performance of the disc pump are analyzed.The results show that a small amount of gas fraction has almost no significant effect on the head and efficiency performance of the disc pump.The performance will be deteriorated when the IGVF is more than 3%at 1500rpm and more than 7%at 2000 rpm above.Under the condition of pure water and gas-liquid flow,the head and efficiency of the disc pump show a slow decline trend.The disc pump satisfies the rotational speed similarity law under the pure water condition.When the IGVF is less than 5%,the disc pump still meets the similarity law under the gas-liquid condition.However,with the IGVF increasing,the similarity law is not applicable.The changes of the water flow rate in the inlet pipe and the disc pump performance will go through four processes:slow drop process,rapid drop process,re-slow drop process and cut-off process.The flow patterns in the inlet pipe are bubble flow,accumulation bubble flow,slug flow and stratified flow,respectively.(2)Numerical simulation study on the disc pump under the condition of gas-liquid two-phase flow were carried out.The internal flow characteristics of the disc pump under the gas-liquid working condition are analyzed based on the case of n=1500 r/min and Q_l=41 m~3/h.The results show that when the IGVF is 1%,there is only a small amount of gas in the low pressure area near the blade suction face and the outlet of the impeller.When the IGVF is 5%,the gas in the blade area diffuses to the middle of the flow channel,especially in the blade area of the shroud disc.When the IGVF increases to 11%,the accumulation of gas phase is observed in the area close to the suction face of the blade area,and the range of airbags formed in the blade area is further expanded.Under each IGVF value,the gas volume fraction is the largest in the blade area of the shroud disc,the second in the blade area of the hub disc,and the smallest in the non-blade area.The gas accumulation aggravates the flow instability in the impeller,which affects the working capacity of impeller.This is the direct reason for the performance deteriorating of the disc pump.In the range of IGVF from 1%to 11%,the time domain characteristics of the pressure fluctuation in the disc pump volute show obvious periodicity.The main frequency is the blade passing frequency,which indicates that the pressure fluctuation in the volute is mainly induced by the rotor-stator interaction.(3)Based on the response surface method,the multi-objective optimization research is carried out by taking the impeller structural parameters as optimization variables and the disc pump performance as target variables.The results show that the response surface equation between the impeller structural parameters and the disc pump performance meets the high accuracy requirements.Blade height,disc spacing and blade number all have significant effects on the performance of disc pump.In the multi-factor combination effect,the combination of blade height and disc spacing has the most significant effect on the performance,the combination of disc spacing and blade number is the second,and the combination of blade height and blade number is the smallest.Through the response surface equation,the optimal combination of the impeller structural parameters is obtained.The performance of the optimized disc pump is improved obviously by the comparison of experimental tests.The research results in this paper fill the research gap in the direction of gas-liquid two-phase flow and optimization design of disc pump.Meanwhile,it also provides a reference for the structural design of high-performance disc pump.