| The proportion of clean energy in the power grid is increasing.Measures such as deep peak-regulating make power station boilers have to operate at low-load for a long time,Due to changes in load,fuel,air supply and other conditions in the operation of power station boilers,it is easy to cause unoptimized conditions or failures such as excessively large,small,or skewed furnace combustion aerodynamic fields,which affect combustion efficiency and emissions,and even cause safety accident.As a non-contact flow field and temperature field measurement method,the acoustic wave method can reflect the state of the combustion field in the furnace in real time and reliably.However,because the speed of sound in medium affected by temperature and flow velocity,which in turn affects the distribution of the sound propagation path,When reconstructing a hot aerodynamic field in furnace by the acoustic method,the coupling mechanism of sound propagation with temperature and flow of the medium is of particular importance.In this regard,this paper introduces the triangle forward expansion method to establish the path tracing model of the acoustic wave in the coupled field of temperature and flow velocity.First,the Lagrangian particle tracing method is used to verify the model results by numerical experiments:different typical simulated temperature fields and flow fields are established,and the path bending effect of sound wave propagation is compared and studied based on the two methods.For the influence of the flow field on sound propagation,a one-dimensional flow field model theory was established to verify the feasibility and reliability of the method,and the law of sound wave propagation in the coupled field of temperature and flow velocity was studied for the first time;in addition,the sound propagation in the tube was designed and built.The test bench has carried out basic experimental verification on the related acoustic path bending model.The following conclusions are drawn through numerical and experimental research:1.The acoustic propagation path in the coupled field of temperature and flow velocity can be effectively tracked by the corresponding theoretical model to obtain its complex distribution,which will provide the necessary foundation for the model algorithm for the accurate and reliable measurement and reconstruction of the flow velocity and temperature distribution in the acoustic wave furnace.2.The acoustic wave path distribution in the temperature field of the model considers the sound ray bending and the sound propagation time error is 10.4%,which seriously affects the reconstruction of the physical field;the sound wave path obtained by the established triangular forward expansion method model and the particle tracking model accords with Fermat’s principle and Snell’s law describe the change of refractive index.The relative error of the sound propagation time of the two models in the temperature field and the flow field is less than 0.001%,The two-phase verification of the sound ray tracking model is accurate and reliable.3.The flow velocity,gradient,etc.will affect the acoustic path in the flow field.For the simulated model flow field,when the tangential velocity reaches 15 m/s,the acoustic path will bend to a certain extent.For the actual power station boiler in the tangential furnace,the burner The slicing circle speed can reach 50 m/s or higher.Under the influence of flow velocity and temperature,if the sound path bending effect is ignored,serious reconstruction distortion will occur.Based on the comparative research and experimental results of different theories and numerical methods,this article effectively reveals the path curvature distribution characteristics of the acoustic wave propagation in the coupled field of velocity and temperature,and gives the corresponding mathematical model.In the acoustic wave measurement in the furnace and other applications,the optimization and reliable realization of reconstruction temperature and flow field methods provide a basic reference. |
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