Papers by Author: Wei Dong Shi

Abstract: Traditional square current driving method has deficiencies in muting and efficiency when controlling the brushless DC motor. This paper presents a method of space vector pulse width modulation for BLDCM, which is in five-segment type. A mathematical model of BLDCM, which is in d-q coordinate system, was established. Then, the experimental platform was constructed with the STM32F103 for BLDCM of electric vehicle. And the experiment results verify the properties of little torque ripple, smooth operation and low switching losses. Besides, the system dynamic and static performance is greatly improved, and has strong robustness. The method proposed overcomes the shortcomings of square current driving method in control efficiency and motor noise.

Abstract: The method for setting the boundary condition of the pool surface was studied. Using the FLUENT 6.3 CFD software,the RNG k-ε turbulence model and SI MPLE algorithm,the sewage treatment pool where a submersible mixer with two leaves was numerically simulated by describing the surface as wall,VOF model and rigid-lid assumption respectively. Meanwhile, the velocity distribution in the pool was analyzed. The results showed that: the contribution of the three different treatments to the flow in the pool are small except the area near the pool surface. In the first case ( describe the surface as wall), pool surface fluid velocity is zero, which is inconsistent with the actual situation obviously. In the other two cases (describe the surface as VOF model and rigid-lid assumption), the pool surface fluid velocity has the same velocity and is not zero,which is consistent with the actual situation. In the case of rigid-lid assumption,convergence was reached easily,and it is undemanding for the computer configuration,so it ( rigid-lid assumption) is the best boundary conditions setting method for the surface and provides guidance for the mixer numerical simulation.

Abstract: Pro/E software was utilized to build the three-dimensional model. Then, the large-scale computational fluid dynamics software ICEM software was used to build unstructured grid of wastewater treatment pool. Based on the CFX software，the wastewater treatment pool was numerically simulated by dynamic coordinate system technology and RNG k-ε turbulent model and PIOS algorithm, and fluid flew in the wastewater treatment pool was analyzed. Considering motor rotor system participates as part of the rotor system in calculation, rotor system of submersible mixer was strength analysis and modal analysis based on fluid-solid coupling. The results show that: the fluid in wastewater treatment pool can be propelled by the submersible mixer, and diffuses along the radial. The rotating speed of the submersible mixer is far smaller than critical speed, so the rotating speed is safe and reliable. This methold has certain significance. It can guide submersible mixer hydraulic performance in design, simulation and Engineering application.

Abstract: The performance curves of a submersible axial flow pump were predicted based on mixture multiphase flow model, RNG k-ε turbulence model and SIMPLEC algorithm, and the solid-liquid two-phase flow in the impeller was simulated. The numerical results show that the performance prediction of the head and efficiency curves show good agreement with the experimental data in the whole flow rate range, and the solid particles in the impeller are mainly distributed on pressure side of blades, while less on the suction side.The solid particles are mainly concentrated in the blade inlet and region near the hub of the pressure side. The experimental results also show that the blade pressure sides have serious erosion, particularly near the hub, but less wear and tear on the suction side.The accuracy of the numerical simulation results are verified by the experiments.

Abstract: The full flow field numerical simulation of the axial-flow pump model is carried out to predict the pump performance based on RNG k-ε model and SIMPLE algorithm and the method of calculating head and efficiency. The numerical results show that the head and efficiency prediction curves have a good agreement with the experimental results. In the optimal operating condition, the prediction error of head is 0.04% and the efficiency error is 0.39% which could meet the requirements of engineering applications. The prediction error based on RNG k-ε turbulence model is larger in the off-design condition owing to the complex flow field of axial-flow pump. The predicted head is lower than the experimental results in the small flow rate conditions and its maximum error is 5.12%, while is higher than the experimental data in the large flow rate conditions and its maximum error is 17.39%. The conclusions will provide the basis and reference for the performance prediction of axial-flow pumps based on CFD.

Abstract: Multi-stage centrifugal pumps for mining are widely used in mining and smelting industry. The operational environment in coal mine sewage is very harsh, so pump shaft and bearing failure happens frequently. In order to avoid disaster damage caused by failure of the pump shaft due to resonance, it is quite necessary and urgent to calculate critical rotation speed of the pump shaft. A calculation program of critical rotation speed for multi-stage centrifugal pumps for mining was developed using the secondary development tool of Object ARX, to give the computational method of the pump shaft load and static deflection and to achieve calculation of the critical speed, and which avoided the disadvantage of the traditional method. The practical application indicates that the program of critical rotation speed is convenient, intuitive and calculation accurate. It not only improves the work efficiency, but also reduces the labor intensity, so the program will have a good application prospect.

Abstract: In order to rebuild 3D models for pump impeller, the total inner complex construction data must be obtained at first. With the help of ICT, 367 ICT images with high quality of two typical impellers of centrifugal Pump were collected respectively, and format conversion from RAW to BMP was fulfilled though a developed program. Volume rendering was fulfilled based on these fault images, VC++ 6.0, MFC, ADO, VTK, and a series of digital image processing. A program named ReImpeller3D was developed on reverse engineering for pump impeller. The software is object-oriented and has several input and output interfaces, and also can supply geometrical models for numerical simulation, FEM, RP, digitized production, and redesign to production either. The practical application shows that it is feasible to use volume rendering to rebuild 3D model for pump impeller.

Abstract: Axial force is one of the main factors which affect the pump safety and reliability during the operation of pumps, especially in multi-stage centrifugal pumps. 150QJ20 type deep-well centrifugal pump (DCP) is selected as an example to research the pump performance and axial force with the numerical simulation and experiment method. The numerical simulation results were compared with experimental measurements, and such result was analyzed. The results show that the change trend of the pump performance and axial force acquired by numerical and experiment is similar. At rated operating point, the error of axial force between the numerical simulation and experimental measurements is less than 3%. This confirmed the feasibility of predict the pump performance by numerical simulation method.

Abstract: In this paper in order to develop high efficiency and high head deep-well pump, a L9 (34) orthogonal experiment was performed with four factors and three values including outlet angle, outlet width, the outside diameter of impeller back shroud, etc. 9 impellers were designed. The whole flow field of new-type two-stage deep-well pump at the operating point for design was simulated by FLUENT 6.2 using the standard model, SIMPLEC algorithm, second-order upwind scheme to solve, and analyze the independent of the number of the grid. 9 groups of the efficiency and head in design scheme were obtained. The effects of geometrical parameters on efficiency, head were researched using Latin square test method. The primary and secondary factors of the design parameters were acquired by way of variance analysis. According to the test result, an optimum program to further design was put forward. After manufactured and tested, the efficiency and head of the final optimal design models were significantly improved. The productions show good energy saving and material saving characters and could replace traditional pumps for deep well in the future, the comprehensive technical indicators achieve international advanced levels. The results would be instructive to the design method of new-type deep well pump.

Abstract: Under water aerator is one of the most important biological wastewater treatment equipments, and it is one of the main power of the sewage treatment plant equipments as well, therefore, effects of aeration is good or bad just as oxygenation capacity is good or bad that is the main basis for the under water aerator . In this paper fuzzy control theory and frequency control principle are used to research running method of the double-impeller underwater aerator and by the demand for dissolved oxygen in water through the aerator variable frequency control, the aerator is controlled to adjust the operating speed, so that to achieve energy savings.