Research On Acoustical Tomography Method For Simultaneous Reconstruction Of Temperature, Concentration And Velocity Distributions

The acquisition of the concentration, temperature and volecity distributions in a mixed gas system plays a crucial role in ensuring the safety and high-efficience operation and reducing the pollutant emission. Due to the coupling effects of the temperature, concentration and velocity, obtaining the high-accuracy measurement of the state parameters in a mixed gas system is challenging.With the distinct advantages, including non-invasive sensing, field measurement and on-line monitoring, acoustic tomography (AT) is considered as a promising visualization measurement method. In this dissertation, the acoustic relaxation attenuation is chosen as another parameter to measure the multiple parameters in the the complex multi-physical field.Different from existing measurement methods, in this dissertation an AT based method is developed for the simultaneous reconstruction of the concentration, temperature and volecity distributions.The main contributions can be summarized as:(1) Acquiring the basic acoustics theory plays an important role in simultaneous reconstruction of the concentration, temperature and volecity distributions. The generation and transmission mechanisms of the acoustic wave are studied, which indicates that the ray model is suitable for calculation. The method of calculating the classical attenuation is given, and the model that describes the relaxation progess is determined. A numerical method is proposed to calculate the relaxation attenuation in a high temperature environment.(2) The determination of the coupling model of the acoustical parameters and the multiple parameters in a complex multi-physical field is vital. The relationship between the temperature, concentration and velocity with the acoustical parameters is revealed. A numerical method is proposed to simultaneously reconstruct the temperature, concentration and velocity distributions. Numerical simulation is implemented to validate the feasibility and effectiveness of the proposed method.(3) A generalized Tikhonov regularization method is proposed to solve the AT inverse problem by converting the original problem into an optimization problem. In this proposed objective functional, the M-estimation is developed to alleviate the influence of the measurement outlies. The split Bregman iteration method is developed to solve the proposed objective functional. Numerical simulation results indicate that the proposed algorithm is feasible, and can ensure a stable numerical solution and improve the reconstruction quality, which paves the way for the simultaneous recosnrtuction of the multiple thermal-physical parameters in the systems.(4) The temperature distribution of the exhausted gas in a funace, the temperature and concentration distributions, and the temperature and velocity distributions of atmospheric surface layer are simultaneously reconstructed, and the fesibility and effectiveness of the propoed measurement method are verified.(5) The experimental system is set up to achieve the simulataneous measurements of the acoustic velocity and the acoustic attenuation. The propagation parameters of the acoustic wave in different mixed gas systems are measured, the coupling models that describe the relationships of the gas temperature are modified, and the feasibility of the proposed simultaneous measurement method is validated.By extending available measurement approaches, this study proposes a new measurement method to achieve the simultaneous measurement of the multiple thermal-physical parameters, including temperature, concentration and vecolity, which is distinctly different from existing AT based measurement methods. As a result, a promising measurement method is introduced for the multiple parameter measurement in the complex thermal-physical fields.