Research On Unsteady Hydraulic Characteristics And Flow Induced Noise In Deep-well Pump

The deep-well pump is one kind of pump which operates in the water,whose shape is small,and is widely used in farmland irrigation and drainage,industrial and mining production,oil and gas transportation and urban water supply and drainage and other fields due to its small size.During its operation,the dynamic and static interference between the impeller and the guide vane will cause strong turbulent pulsation in the flow channel,which will seriously affect the running stability of the pump,and will induce vibration and noise,which will affect the service life of the pump.The MJ157-130 deep-well pump is chosen as the prototype aiming at working out the unsteady hydraulic characteristics and flow induced noise characteristics of the pump.When numerical simulation being carried out,the characteristics of internal flow,pressure fluctuation and internal sound field under unsteady flow are analyzed.The research procedures and conclusions are as follows:1.Analysis of unsteady characteristics of internal flow field in deep-well pumpThe results of analysis of the time-average distribution characteristics of the flow field show that,for every operating condition,the variation trend of internal pressure in impeller and guide vane is basically the same.With the increase of flow rate,the pressure at the outlet of guide vane decreases gradually.Meanwhile,there is a low-speed “stripping zone” near the pressure side of the vane blade.The area of "stripping zone" decreases gradually and moves towards the outlet with the increase of flow rate.Under the condition of large flow rate,the low-speed "stripping zone" disappears.The maximum position of the turbulent kinetic energy is located at the intersection of the static and dynamic cascades,whereas,the distribution of turbulent kinetic energy varies significantly under different operating conditions.The analysis results of pulsation strength of flow field show that under different working conditions,the trend of pressure pulsation intensity in the flow channel is increasing first and then decreasing and the maximum pulsation strength appears near the interface between the impeller and the vane all along.The velocity pulsation intensity is most obvious in the inlet region of guide vane.The pulsation intensity distribution of turbulent kinetic energy varies greatly under different working conditions.With the increase of flow rate,the pulsation intensity at the interface increases gradually.Under each working condition,the streamlines in the impeller are very uniform and there is no vortex.However,in the guide vanes it is obviously different with the impeller,which appears that there are obvious vortices inside the guide vanes under small flow conditions,and the flow condition is improved as the flow rate increases.2.Analysis of pressure fluctuation characteristics of internal flow fieldThe time-domain and frequency-domain characteristics of pressure fluctuation at four components in the computational domain are studied.Here are the conclusions: the fluctuation of the pulsation time domain of the monitoring section of the import section is weak.Under different working conditions,as the flow rate increases,the pressure decreases as a whole.Under various working conditions,the main frequency of the pressure pulsation and the harmonic frequency are at the frequency multiplication of the pump shaft frequency.The pressure fluctuations at different monitoring points in impeller have the same number of waveforms as the number of guide vanes blade in a rotating cycle of impeller and the main frequency of the pressure fluctuations is the guide vane frequency.Similar to this,in the guide vane,the pressure pulsation of the monitoring points at different positions of the guide vanes shows the same number of similar waveforms as the number of impeller blades in one impeller rotation period,and the main frequency of the pulsation is the blade frequency of the impeller.The fluctuation of the pulsation time domain of the monitoring points in the exit section is relatively weak.Under each working condition,the main frequency of the pressure pulsation is at the frequency multiplier of the pump shaft frequency,and also at the impeller leaf frequency and its multiple frequency.3.Noise Induced by fluid flowThe results suggest that the noise induced by impeller is mainly discrete noise with the corresponding frequencies being axial and double frequency.And the noise induced space guide vane is consisted of discrete and broadband noise,with the corresponding frequency being impeller blade frequency.