Research On Three-Dimensional Temperature Field Measurement By Acoustics And Its Application On Combustion Optimization In Power Plant Boiler

The temperature field distribution in furnace directly reflects the combustion condition in furnace. Accurate knowledge of the temperature field distribution in furnace can provide a basis for combustion optimization. Operators can optimize combustionin furnace by monitoringcombustion condition in real time. However, it is difficult for the existingtemperature measurement technology to measure the temperature distribution in furnace especially for 3D temperature distribution measurementdue to the hot, dusty, corrosive harsh environment in furnace. Therefore, an accurate measurement of 3D temperature field distribution in furnace has an important significance for combustion process research and combustion optimization. This paper puts forward a 3D temperature field acoustic measurement method and studies its application on combustion optimization in power plant boiler from acoustic theory.This paper establishesa mathematical model for 3D temperature field reconstruction by acoustics based on acoustic theory. Many reconstruction algorithms are proposed for solving the reconstruction model.Advantage and disadvantage of these reconstruction algorithms are analyzed in terms of reconstruction accuracy, reconstruction speed, noise immunity and the ability to solve serious ill-posed problems by simulation. Simulation results indicate that all of thesereconstruction algorithms can solve 3D reconstruction modeland LSQR algorithm is the best reconstruction algorithm.The influence of the number and arrangement of acoustic measuring points ontemperature field reconstruction is studied. The arrangement of acoustic measuring points is optimized. An optimized arrangement of acoustic measurement system is proposed. The influence of the number and arrangement of acoustic measuring points and the number of acoustic paths on reconstruction accuracy and reconstruction speed is analyzed bysimulation. Basic principles of acoustic measurement system design are summarized. Studies indicate that too many or too few acoustic measuring points go against temperature field reconstruction. The system design musttake many factors into considerationbased on the basic principles, such asreconstruction accuracy, reconstruction speed, installation costs, security and so on.A3D temperature field experimental acoustic measurement system is designed. Experiments are carried out in cold state and hot state, measuring different temperature fields. Experimental results indicate that the 3D temperature field acoustic measurement method can accurately depicttemperature fielddistribution. The measurement method can reconstruct the location and temperature of the hot spots for the temperature fieldwith hot spots, and the resulting temperature gradient can accurately reflect the trends of temperature field. The measurement method has certain accuracy and reliability, In order to ensure the accuracy ofmeasurement of time of flight, time delay estimation algorithms are studied. Studies show that PHAT cross-correlation algorithm can effectively remove indoor reverberation effect and get accurate time delay estimation.A combustion optimization model is established between 3D temperature field information and boiler operating parameters based on acoustic pyrometry. Combustion optimization control strategy is studied based on this model.The combustion process is simulated numerically by Fluent.The simulation results indicate that the combustion optimization model can accurately predict the impact of changes in boiler operating parameters to temperature distribution in furnace. Simulated annealing algorithm can be used as combustion optimization control strategy. The control strategy is feasible and can solve the problem of temperature field center deviation.