| Submersible sewage pump is mainly used for pumping sewage,industrial wastewater and the liquid containing solid particles and fibrous suspensions in industrial process.It is widely used in municipal engineering,light industry,chemical industry,construction,mining,metallurgy and other industries.This paper studied the submersible sewage pump with impeller using a design of ultra-thick blades.It was found in previous researches that this design can achieve the unity of high efficiency and non-overload,but easily lead to vibration and noise.The numerical calculation and experimental research were carried out to solve the problems of vibration and noise in submersible sewage pump in this paper.The characteristics of pressure pulsation,radial force,sound field and radiation sound field were analyzed,and the multi-objective optimization was also studied to reduce the noise.The main contents and achievements of this paper are as follows:(1)The researches about flow-induced noise and vibration in the pump at home and abroad were systematically investigated,and the main influencing factors of the flow-induced noise and vibration in submersible sewage pump were determined.The hydraulic design method of high efficiency,low noise and non-overload was also improved.(2)A model pump was built by reducing the scale of the prototype submersible sewage pump of WQS150-48-45 in proportion.And the steady flow simulation in the whole field was carried out in this model.The numerical simulation results are in good agreement with the experiment results.The simulation results of pressure fluctuation are coincident with the measurement results.Thus the simulation results can reflect the unsteady characteristics of pressure fluctuation in pump,which can provide reliable sound source information for sound field calculation.(3)Based on the direct boundary element method,the sound field in submersible sewage pump was calculated by using the pressure pulsation on volute and blade surfaces as dipole sources,and the distribution characteristics of SPL(Sound Pressure Level)at different flow rates in different volutes were obtained.Through the analysis of SPL distribution in frequency domain at inlet and outlet of pump,the transmission characteristics of sound source were acquired.The relationship between the pressure pulsation and the sound field in pump was established,which is used to seek methods for active control of sound source.The effects of matching ability between volute and impeller on the acoustic field distribution were studied.The noise simulation calculation results show good agreement with the noise measurement results at outlet,which can be used as the evaluation reference of the internal flow noise level and frequency domain characteristics in the submersible sewage pump model.(4)Based on acoustic-structure coupling model,the outer sound field calculation of submersible sewage pump was carried out.The noise radiation characteristics were obtained by calculating directivity field points,plane field points and spherical field points.Correlation between the noise level and pressure fluctuation was established.The relationship between noise distribution and radial force was also built.The pressure fluctuation is an important effect on the noise level and the position of maximum and minimum noise is closely related to the orientation of radial force.The sound power level of the whole machine which provided a uniform noise evaluation standard for noise reduction was calculated in this paper.(5)The test system of flow-induced vibration and noise in submersible sewage pump was established.Vibration and noise signals of different impeller and volute combinations were collected.And the distribution characteristics in time domain and frequency domain were analyzed respectively.The flow noise presents broadband characteristics,and the BPF(Blade Passing Frequency)and its harmonic frequency show obvious discrete features.The head and the efficiency of the pump 2# are the highest,and the flow-induced noise in this pump is less than that of the other two combinations.The rotor-stator interaction affects the main frequency of the flow-induced vibration,which is also the main cause of the induced noise.The flow noise is more likely to spread toward the outlet of volute.(6)The multi-objective optimization was applied for noise reduction in prototype submersible sewage pump.The optimal Latin hypercube experimental design was adopted to obtain the sample points of relevant variables,and the response values were also obtained by numerical calculation.The Kriging model of variables and their response values was constructed.Under the premise of high head and efficiency,the global optimization was adopted and the Pareto distribution was obtained.The numerical simulation of optimal noise reduction scheme was carried out to verify the accuracy of the approximate model.The pressure distribution in the optimized model is more uniform,the turbulent kinetic energy and the noise reduce obviously. |
