Investigation On The Gas-Liquid Two-Phase Flow Characteristics Of Inducer

As the most widely used vane pump,centrifugal pump plays an important role in petrochemical industry,agriculture and other fields.With the rapid development of aerospace and nuclear power technology,the medium transported by centrifugal pump gradually expands from a single single-phase medium to a mixed multi-phase medium such as vapor/gas-liquid,which puts forward higher requirements for its performance.In order to improve the performance of the centrifugal pump,inducer is usually installed ahead of the impeller.The inducer can effectively improve the anti-cavitation ability and improve the flow instability of the pump under gas-liquid two-phase conditions.However,compared with the main impeller,the working space and internal turbulence field of the inducer are more complex.Especially,the complexity of the internal flow can be further aggravated when the incoming flow contains gas.It is of great engineering significance and theoretical value to study the characteristics of gasliquid two-phase flow inside an inducer.Therefore,an inducer was taken as the research object.In order to investigate the gas-liquid two-phase flow characteristics of the inducer,experimental and numerical methods were combined.Also,and the influence mechanism of different liquid flow rates and ventilation on the two-phase flow characteristics was obtained.The main work and achievements of this paper are as follows:1.Domestically and overseas,the research status of gas-liquid two-phase flow test and numerical simulation is summarized.And the study of gas-liquid two-phase flow pattern is overviewed.2.A multi-physical field synchronous test platform was built to study the effects of different ventilation rates on the energy characteristics of the test system.Meanwhile,pressure pulsation characteristics and the internal flow pattern were obtained.The experimental results show that:(1)With the increase of IGVF,the energy characteristic of the model pump are reduced sharply.In addition,the corresponding IGVF increases with the decrease of liquid flow.(2)Under the rated flow condition,obvious stripshaped bubbles appeared at the blade edge of the inducer.With the increase of IGVF,strip-shaped bubbles gradually expanded to the top position of the inducer blade,showing the unsteady evolution process such as periodic growth,development and shedding.(3)With the different ventilation,the flow state inside the inducer was different,and the number and size of bubbles increased with the increase of IGVF.(4)The outlet pressure pulsation of the model pump presents an obvious periodic fluctuation rule,and the peak value of pressure pulsation first increases.Then,the peak value decreases with the increase of IGVF.The frequency of the main blade is dominated.At the same time,the main frequency is highest when IGVF=3%.3.Based on the VOF model,a numerical calculation method for gas-liquid twophase flow in the inducer was established.The accuracy of the numerical calculation method was verified based on the experimental results.The results show that:(1)the energy characteristics of the inducer decrease with the increase of IGVF.Under the large flow and IGVF greater than 1%,the inducer loses its ability to work due to gas blocking.(2)The range of high pressure zone on inducer blade surface gradually expands with the increase of ventilation.However,the pressure value on blade surface decreases when IGVF exceeds 5%.In addition,with the increase of IGVF,the bubbles tend to gather near the blade working edge and the exit edge.(3)The gas phase volume fraction perpendicular to the axial section of the inducer peaks at the leading edge and gradually expands to the trailing edge.On the same axial section,the volume of gas phase increases with the increase of flow rate.(4)Compared with other positions,the pressure pulsation at the trailing edge of the inducer was the largest.With the increase of IGVF,the periodicity of pressure pulsation in the time domain was gradually weakened.Also,its peak value in the frequency domain is mainly concentrated in the axial and blade frequency.At the low frequency,the amplitude gradually increases.4.Based on the visualization platform,the typical gas-liquid flow patterns were obtained.In addition,the influences of different flow patterns were explored.The results show that:(1)The inducer gas-liquid incoming flow pattern is affected by the liquid flow rate and ventilation volume.And there are mainly three flow patterns:bubbly flow,wavy flow and plug flow.The incoming flow pattern of the inducer was drawn based on the test results.(2)Bubbly inflow discharge under current rated flow condition with IGVF≤3%,and under large flow condition.Meanwhile,the flow pattern is dominated by discrete bubbles,and the gas-liquid mixture is uniform in the flow field.A clear tip vortex structure can be observed in the flow passage,and the average pressure at the axial position of the inducer is the largest.(3)Under the condition of low flow rate,the wavy inflow is composed of large bubble groups.Obviously,the tip vortex structure doesn’t appear.(4)Under the condition of the current rated flow and IGVF≥5%,the bubbles in the flow field of this flow pattern adhere to each other.In addition,tip vortex structure is also observed.Also,the average velocity of axial section under this flow pattern is maximum.