Numberical Simulation Investigation About Wall Temperature Of Ultra Supercritical Boiler At High Temperature Surface

With the rapid development of social economy,demand for electricity is increasing.Thermal power generating units is also growing toward high-capacity and high-parameter direction.Ultra supercritical unit set up at the historic moment With the further improvement of temperature parameters,High temperature heated surfaces work in a worse environment But the problem of tube explosion is inseparable from the tube wall overheating Getting the comprehensive and accurate the wall temperature of heat exchangers is the fundamental way to solve the tube explosion problem.The thermal conductivity of the ash and the oxide skin is very small,which hinders the heat transfer and aggravates the overtemperature deterioration.Many domestic and foreign scholars have done a lot of research on the wall temperature calculation,there are few studies on the effect of dirt on the wall temperature.Therefore,the analysis of the influence on the wall temperature has an important guiding significance for the safe operation of the power plant.This paper takes a 1000 MW Ultra Supercritical Boiler as the research object,And Fluent software is used to simulate the combustion of the furnace.under four conditions of combustion under rated load that BCDEF layer AA wind tangent,ABCDE layer AA wind Fanqie,BCDEF layer AA wind tangent and ABCDE layer AA wind Fanqie.The flow field and temperature field in the furnace are analyzed,and the distribution of smoke temperature and smoke velocity in the region of superheater and reheater is analyzed.emphatically Sixth segments,fifty-fourth rear screens,ninety-second high temperature superheater and seventieth high temperature reheater have the highest smoke temperature,which is the easiest to explode.The selected four pieces of pipe screen using the method of flue gas and steam side coupling were studied when the Clean pipe,outer wall ash pipe,Tubes with oxide skin and A tube with fouling in the inner and outer walls under four wall model of various factors on the tube wall temperature distribution.The simulation results show that the temperature distribution of the single tube in the four kinds of tube displays the trend that the wall temperature rise along the direction of steam flow.Due to the difference of radiation and convective heat,the temperature of outermost coil is the highest.The closer to the inside,the lower the temperature.the smaller the temperature difference between the outer and the inner adjacent tubes.The difference is that the highest point of the screen superheater appears on the bottom due to the radiation of the high temperature flue gas.The highest wall temperature appears on the elbow and horizontal pipe section,The closer to the outer ring wall,the more obvious the distribution.The inner ring wall temperature is less affected by the smoke radiation,and the highest wall temperature appears at the outlet of the steam.The superheater and reheater are affected by transverse scour of flue gas and the highest wall temperature appears at the elbow and the outlet of the steam.In this paper,The influence of the presence of oxide and ash accumulation and the change of the thickness of the fouling on distribution of wall temperature.are also studied.The results show that the formation of the oxide skin increases the temperature of the tube wall,and the existence of ash deposits reduces the temperature of the tube wall.The wall temperature that the presence of ash in the outer is higher than the wall temperature that the inner and outer walls have grey pollution.The influence on the wall temperature has just started to increase linearly,and then it is basically exponential growth.The location of the dangerous point is determined by the simulation of the wall temperature distribution,which provides the basis for the optimization design of the high temperature heating surface and the selection of the wall temperature detection points.