| In the air-cooled closed cooling water system,the need to increase the system to provide a constant pressure water supply device to provide a reference pressure,centrifugal pump start and stop will cause a large pressure fluctuation pressure,so that the cooling medium in the pipe network and tank which is influenced by the amplitude and time of pressure fluctuation of constant pressure point by experiment and numerical simulation on the test platform.The numerical simulation of the pressure flow fluctuation of the pipe network is carried out when the valve of the closed water system is connected to find the optimal adjustment scheme.The factors influencing the flow increment of the multi-pump parallel pipe network and the layout and analysis of the pipe arrangement are summarized and the reference is given to the engineering design.Using the existing experimental platform,through the experimental study of centrifugal pump start and stop time,the pump stable operation of different working conditions start and stop,different balloon tank pressure,the same pump operating conditions of different water capacity,double pump at the same time to take a single or double pressure point and the ratio of the volume of the air tank and the capacity of the pipe network to the pressure fluctuation of the centrifugal pump start and stop the constant pressure point.The numerical control is used to compare the different pipe length and diameter on the pump start and stop pressure fluctuations.The pressure fluctuation amplitude of the balloon cans is 30.4% ~ 76.4%,and the difference is between the time of shutdown and the difference of the pressure fluctuation of the balloon tank with the capacity of 2%,8% and 100% of the experimental platform 53.1% ~ 141.5%;the greater the steady flow,the greater the amplitude of the pressure fluctuation,the longer the settling time;the fixed pressure 0.3MPa is less than the stabilization time of 0.2MPa 6 ~ 7s;the same operating condition large,the smaller the amplitude of the pump start fluctuation,the greater the amplitude of the closed fluctuation;the double pump to run the constant pressure point when the first open from the fixed pressure point near the pump pressure drop smaller than the first open pump small 6.7%~ 8.4%.Through the numerical simulation of water system valve joint process in the process of convergence point of the dynamic pressure and flow fluctuations,the first to adjust the pump speed adjustment valve opening path caused by the flow and pressure peak when the maximum pressure when the valve at the same time,The stability time of the system is the shortest,the peak value of the pump before the valve is the smallest,the maximum difference between the three pressure modes is 20%,the maximum peak of the flow is 9.6%;the adjustment should be selected according to the actual demand.Based on the actual double pump parallel pipe network flow increment problem,the characteristics of pipe network characteristic curve,pump performance curve and parallel number are analyzed by graph and numerical simulation.The more stable the pipe network characteristic curve is,the steeper the pump performance curve is more parallel,The more the number of pumps in parallel,the worse the flow increase effect.This thesis analyzes different factors of constant pressure water pump transient pressure fluctuation effect on the air tank,and the valve adjustment process of different pressure and flow fluctuation,provide a reference to the actual pipe network pressure design selection and variable load adjustment of security issues. |
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