The Study Of Sound Waves Incidence Angle On Acoustic Propagation Through Tube Arrays

For the furnace heat exchanger boiler in power plants, low heat transfer efficiency and leak detection and location has been one of the major problems. At present, the acoustics application is the solution, which is more efficient and potential. The basic principle of acoustics is that the dust which have been attached to the pipes is removed by the vibrations caused by sound waves. Monitoring and positioning the fault source by the jet noise information of the leakage. However, due to the heat exchanger tubes arranged in an array of complex, high-temperature furnace inherently non-uniform radiation fields and negative pressure and the noise characteristic leak jet will have an impact on the sound propagation, it will directly lead to the acoustic behavior of a clear understanding of the furnace. The study of sound propagation characteristics of the furnace is necessary.Based on the theory of phonon crystals, the tube array is converted into a two-dimensional phononic crystal structure. The mathematical modeling and simulation by the finite element software COMSOL study acoustic sound propagation characteristics obliquely incident after the tube array and get SPL tube array insertion loss and acoustic incident direction, the tube through which sound waves relationship between number of rows. The Study about the influence of sound waves incidence angle on acoustic propagation through tube arrays contents are as follows: By changing incidence angle and number of tube rows and making the math model construction and simulating calculation on tube array of utility boiler by using plane wave expansion method and Comsol finite element software, we can get the relations among the insertion loss of sound pressure level, sound waves incidence direction and the number of tube rows passed by sound waves. The results show that frequency domain section and peak of sound transmission stopband of incident elastic waves when getting through different arrays of number of tube rows will change with oblique incidence angles.Research results are as follows: The acoustic wave propagation direction along the tube row structure, its central location of the first frequency band gap does not vary with changes in the tilt angle is changed. However, the center position of the second sub-band gap move to the low frequency with the oblique incident angle. The other band gap always change with incident angle. The sound transmission characteristics of the wave vector along the direction has significant change with the incident angle. Firstly, the center of band gap moves to the high frequency.And the secondly, sub-band gap center moves to the low frequency, and the entire frequency range of "forbidden zone" and "conduction band" will appear change. The results provided for a new theoretical basis for the design of acoustic sootblowers in power plant boiler and location of the furnace pipeline leak location.