Study On Measurement Method Of Large Diameter Flue Gas Flow

Under the background of rapid development of global economy, on the one hand, it accelerates the process of urbanization and people’s living standards can be improved; on the other hand, it also brings about the problems of environmental pollution. Haze weather even spread throughout the country, which has affected people’s health and daily life seriously. Air pollution, mainly refers to the decline of the air quality caused by emissions of dust, waste gas, automobile exhaust emissions and coal combustion, etc. Therefore, establish on-line monitoring device for the flue gas flow effectively is very important.First of all, this paper provides a brief introduction of the development of gas flow measurement, especially, large diameter duct flow field distribution with rectangular elbow is researched. Based on computational fluid mechanics, the three-dimensional flue model is established in GABMIT software, then simulate it with FLUENT to explore flow law of fluid in the flue duct and contrast the simulation data with laboratory test data. Finally, the correction function of average velocity of flue gas is established and find out the compensation coefficient.According to the results of the numerical simulation, the ultrasonic flow measuring device with large diameter, rectangular bend and comes with compensation function is designed. The main control unit adopts C8051F120 singlechip. Completing the ultrasonic transmitter and receiver circuit, signal processing circuit and the man-machine interface circuit software and hardware design. Then convert the calculation results into the standard 4-20mA current signal output by D/A conversion circuit. Using RS232 serial communication interface to accomplish the purpose of auto-control of ultrasonic testing process, data collection and storage.Finally, adopting cross-correlation algorithm to process the ultrasonic signal, which ensure getting effective signal detection in strong noise jamming environment, in order to improve the signal to noise ratio.