| Cavitation is a common physical phenomenon in hydraulic machinery.Its generation and development will adversely affect the performance of hydraulic machinery.When it develops to a certain extent,it will cause damage to the flow components.In severe cases,it will cause strong vibration and noise.The complexity of the cavitation phenomenon has driven experts to carry out a lot of research work on it,but its understanding in engineering is still in the stage of continuous exploration,so it is of great significance to quantify and classify the cavitation flow inside hydraulic machinery.This paper uses a combination of numerical simulation and model tests to compare and analyze the internal cavitation development of axial flow pumps.On this basis,the cavitation phenomenon is studied in depth,and the results are summarized under different blade placement angles and under different working conditions.The law between the initial cavitation margin and the critical cavitation margin of the axial flow pump.At the same time,the concept of cavitation rate is introduced to quantify the development of cavitation,so as to classify the interval between primary cavitation and critical cavitation.The specific innovations and research contents are as follows:This paper takes a vertical axial flow pump with a specific speed of 837 as the research object.The calculation model in the numerical simulation calculation uses SST k-? as the turbulence model and ZGB as the cavitation model.Y+ensures the accuracy of numerical calculations,and then compares the numerical simulation results with the test results to verify the accuracy of the numerical calculations.Based on the analysis of the suction surface pressure,cavitation distribution and static pressure load of the blade,the numerical calculation of the 0 degree blade placement angle under different inlet pressures shows that the internal cavitation of the axial flow pump is first born in the impeller close to the blade.At the tip of the inlet side of the blade,and when the inlet pressure continues to decrease,cavitation will appear at the outlet side of the blade and the hub one after another.In order to analyze the cavitation performance of the pump under three groups of different flow conditions,by studying different working conditions under the same cavitation margin,it was verified that the large flow conditions and the small flow conditions are better than the design flow conditions.The area of the cavitation zone of the blade will be significantly enlarged,and the critical cavitation margin of the design flow condition will be smaller than the high flow condition and the small flow condition.In order to verify the accuracy of the numerical simulation results,the cavitation performance test and high-speed camera observation method test were carried out on the vertical axial flow pump device respectively,and the cavitation margin-flow curve under different flow conditions and the cavitation primary and The morphology of vacuoles in the deteriorating stage.Comparing it with the numerical simulation analysis,the two results confirm each other,which proves that the numerical simulation results are highly reliable.Aiming at the problem of quantifying the cavitation of axial flow pumps in engineering,this paper innovatively analyzes the initial cavitation margin and critical cavitation margin of different blade installation angles and different working conditions,and the distance between the two is obtained.With the decrease of the flow rate,the law shows a trend of first decreasing and then increasing.At the same time,the cavitation rate was established as the criterion for determining the critical cavitation margin of the axial flow pump,and the cavitation rate was used to classify the primary cavitation and the critical cavitation,and the corresponding cavitation safety of each stage was calculated.The coefficient provides a certain guiding value for the actual project to determine the installation elevation of the pump. |
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