Modeling And Research On Gas Flow Field Of Rectangular Short Air Passage In Thermal Power Plant

In the thermal power plant,the continuous improvement of power of generation unit makes the power plant air duct system becomes large and complex.There are a lot of large-diameter air ducts and lots of straight pipes are too short.This makes the gas flow field in the duct becoming very uneven and the measurement of flow becomes more and more difficult.At present,in order to ensure the safety of the unit operation and environmental protection,thermal power plant puts forward higher requirements to the accuracy of the flow measurement of the boiler feed air and exhaust emissions.Therefore,it is very important to design a kind of detection device which can adapt to the harsh conditions of the field to monitor the gas flow accurately.First of all,this paper briefly describes the development of gas flow measurement.The distribution of flow field of large-diameter rectangular air duct with rectangular bends is studied in detail.According to the principle of computational fluid dynamics,the GAMBIT is used to establish the actual air duct in the thermal power plant and the three-dimensional air duct model of the test duct,which is set up in the laboratory.In the FLUENT software,two numerical simulations with two models were respectively carried out to analyze the distribution of velocity field and pressure field in short air duct,and the numerical relationship,which is existed between these physical quantities.At the same time,the numerical simulation results of the simulated duct and the practical duct of the thermal power plant are compared and analyzed.In order to distribute the location of speed points of the air duct rectangular sectionand then determine the optimal location of the sensor installation,we must accord to the specified value of "Log-Chebyshev" mathematical model.The velocity on the cross section of 0.5 times the diameter before and after the curve was measured by hot wire anemometer.The velocity data were collected,and the insertion depth of the instrument was fitted with the measured velocity.The relation between velocity and depth of insertion is derived at different locations.In industrial field measurement,the flowmeter is generally fixed in a certain position,and the speed of the fixed point on behalf of the average speed of the cross section.Therefore,when the depth is fixed,the velocity of the fixed point and the average velocity of the cross section are fitted,and deduces the function relation.It can improve the calculation of the flow field distribution in large diameter and short duct,and provide effective technical support for further development of flow measurement device which can accurately measure the complex gas environment of the channel.