Optimize Investigations On Acoustic Detecting Techniques And Measurement Of 3-D Temperature Field

The detection of the temperature field is very important in scopes of researches, the agricultural and industrial production and heating and the daily life. However, because of the complexity of measurement, it is very difficult to achieve the accurate measurements of the whole temperature field by using the traditional technology of thermocouple or radiation pyrometer. As a new-style temperature measuring method, acoustic method has many advantages such as wide temperature range measurement, large space of measuring object, high-precision, non-contact, continuous measurement, easy maintenance and so on .It will be more and more useful in industry production and science researches. In order to adapt to the requirement of measurement in temperature field, some key issues to temperature field measurement by acoustic tomography are discussed in this thesis.At first, an analysis on the realistic importance of the temperature field monitoring has been given, and the principle and develop instance of acoustic thermometry has been introduced in the thesis and gained the advantage of this method.Secondly, several methods about acoustic travel time has been introduced in the temperature field. The result shows that cross-correlation function is a useful algorithm for signal analysis in condition of strong background noise and using this method to calculate the acoustic travel time is feasible.In addition, because the acoustic wave refraction in temperature gradient field is an important factor that affects the reconstructing accuracy of temperature field by acoustic method, the ray tracing and simulation of the true propagation paths of 2-D and 3-D acoustic wave by forward deploying triangle and deploying regular tetrahedrons are carried out.At last, 3-D temperature field reconstruction based on the least-square algorithm is expatiated. The influences of the sensor location and the measurement space division on the temperature reconstruction precision are investigated. Computer simulations using a single-peak and circular symmetrical temperature field as the temperature model to test above two factors'influence on the reconstruction precision are implemented. A comparison and analysis have been made on the reconstructing quality of the temperature field whether considering the acoustic wave refraction or not. The analyzing result shows that the increase of the amount of acoustic sensors can improve the reconstructing accuracy to some extent; it will improve the reconstructing accuracy considering the acoustic wave refraction in the reconstructing process. The results are satisfying. It is particular to the temperature fields with great temperature gradient, although the method has disadvantage in the reconstruction velocity.