Numerical Analysis And Optimization Of Desulfurization Circulating Pumps In Million-kilowatt Thermal Power Plant

The development and application of desulfurization circulating pumps in thermal power plants have important practical significance and significant economic and social benefits for reducing sulfur dioxide pollution discharged by thermal power plants and treating the environment.Studying the design method and theory of the desulfurization pump in the absorption tower of the thermal power unit,and analyzing the complex flow field inside the desulfurization circulating pump can provide a basis for the efficiency improvement and optimization design of the desulfurization circulating pump.The thesis uses the desulfurization circulating pump to perform numerical simulation and analysis under the conditions of clean water and two-phase flow.The main research contents and results are as follows:(1)According to the basic design parameters of the desulfurization pump given,the liquid-solid two-phase flow theory is used as the design basis,and the flow components of the desulfurization pump are hydraulically designed,and then the flow of the desulfurization pump is passed through the Pro/E software.The components are modeled in three dimensions,and the ICEM software is used for meshing.Finally,the CFX software is used to perform numerical simulation calculations on the desulfurization pump under clean water conditions.The results show that the internal flow characteristics of the desulfurization pump under clean water conditions meet the theoretical design requirements.The desulfurization pump can carry out the following numerical simulation calculation work.(2)Based on the calculation of the clean water medium,the mixed multi-phase flow model(Mixture Model)is used to numerically simulate the solid-liquid two-phase flow inside the desulfurization pump,and compare and analyze the internal flow characteristics of the desulfurization pump under clean water conditions,The following conclusions are obtained:the change trend of the external characteristic curve of the desulfurization pump under the conditions of clear water and two-phase flow is the same,but the head and efficiency of the desulfurization pump will be lower than the value under the conditions of clear water under the two-phase flow;Under the same flow conditions,the inlet pressure of the impeller under the two-phase flow condition is lower than the pressure under the condition of the clear water medium,but the outlet pressure is higher than the value under the condition of the clear water medium;when the particle size of the solid phase of limestone is the same,the particle volume fraction is Increasing will cause the wear of the flow components of the desulfurization pump to increase.The most severely worn area in the pump is the inlet side of the blade,the back of the blade,the working surface of the blade and the rear cover of the impeller decrease in order;when the volume fraction of limestone solid phase particles At the same time,the increase of particle size will increase the wear of the flow components in the desulfurization pump.The most severely worn area in the pump is the working surface of the blade.The wear of the inlet edge of the blade,the rear cover of the impeller and the back of the blade decreases in turn.(3)The mixed multiphase flow model(Mixture Model)and Schnen-Sauer cavitation model are used to numerically simulate the cavitation flow inside the desulfurization pump,and the following conclusions are obtained: critical cavitation of the desulfurization pump The margin is related to the properties of the fluid medium.The value of the critical cavitation margin is higher under the condition of limestone solid phase particles than that under the condition of clear water medium;under the condition of clear water medium and limestone solid phase particles,the inside of the desulfurization pump The distribution of vapor bubbles is roughly the same;under the same inlet pressure,the volume fraction of vapor bubbles under the condition of solid limestone particles is higher than that under the condition of clear water medium.The existence of solid particles of limestone will promote the development of cavitation;As the volume fraction of solid phase particles of limestone increases,the volume fraction of vapor bubbles will increase,and the critical cavitation margin NPSHc of the desulfurization pump will increase.(4)According to the optimized design of the pressurized water chamber structure of the desulfurization circulating pump,two optimized schemes for installing partitions in the pressurized water chamber were designed.The diaphragm position of the pressurized water chamber is designed on the V to VIII section.After numerical analysis,it is determined that the performance of a pair of desulfurization circulating pumps is better.After the optimization,the head and efficiency of the desulfurization circulating pump under clean water conditions are increased by 3 % And 2.56%,the head and efficiency values have increased by 2% and2.4% under two-phase conditions.After optimization,the pressure and limestone solid particles at the junction of the outlet of the impeller working face and the front and rear cover plates have been reduced,and the wear at this position will be reduced.