Detection And Study Of High Pressure Bypass Leakage Of Large Thermal Power Units

The bypass system plays a very important role in the start-up,operation and shutdown of large thermal power units,and is an important part of the thermal system of power plants.When the high pressure bypass occurs internal leakage,some steam does not enter the high-pressure cylinder to do work and enters the reheater through the high pressure bypass.At the same time,the leakage of the high pressure bypass is easy to be caused by overpressure of the boiler and the overheating of the reheater tube wall,which threatens the safety of the operation of the unit.Therefore,the current thermal power unit needs to study the scientific and effective method of measuring the leakage of high voltage bypass,and get the leakage of the high voltage bypass in time.It has important theoretical significance and application value for the safe operation of the unit,the maintenance of the equipment state and the improvement of the efficiency of the power generation.The research contents and achievements in this paper include the following aspects:(1)based on the current research status and research trends of high pressure bypass internal leakage at home and abroad,combined with the current noise signal analysis technology,a method of measuring the leakage of high pressure bypass by using the noise signal of the fluid is proposed to measure the noise data of the pipeline system under different flow conditions and obtain the noise by numerical analysis.The calculation model of sound and flow;(2)using FLUENT software to establish a high temperature and high pressure steam flow model to simulate the internal leakage of high pressure bypass system.The amount of leakage detection into the inside of the pipe flow measurement,setting different boundary conditions change into the steam flow in the model,then the simulation of flow field and noise calculation under different working conditions.From experimental data,the relationship between the univariate and multiple logistic regression analysis and univariate and multivariate AR model of noise and the traffic noise and traffic,the establishment of calculation model of steam and tested with the data.The research of working fluid pipeline water flow model,in order to simulate data flow under different conditions,using regression analysis and AR model method to deal with noise and traffic data.Comparing the flow calculation models obtained by the two kinds of working fluids,it is found that the two models have the same form and different coefficients,so the concept of flow measurement system is put forward;(3)measure the system with sensors,preamplifiers,special filters and spectrum analyzers,and verify their correctness in the laboratory.In order to adjust the flow of fluid inside the pipe through the opening of the outlet valve,the fluid noise signal is detected by the acoustic sensor and transmitted to the spectrum analyzer by the acoustic sensor,then the noise data is obtained by filtering and digital signal processing.The flow rate is calculated through the software of the flow measurement system,and is compared with the measured results of the standard flowmeter.The simulation test and laboratory test data verification results show that the measurement system has good accuracy,as do follow-up units in the field leakage measurement test the full preparatory work.