Study And Design For The Experiment System Of Aerodynamic Field Measurement In Furnace By Acoustic Method

The aerodynamic field in furnaces is an important factor determining the safety of furnaces and economical operation. But there are no fast and effective methods on measurement of the aerodynamic field in large-scale furnaces all the time. Not to mention that there are the techniques of online test. Apparently, the traditional methods is consuming with long time and low precision. However, the acoustic method is nonintrusive in full-field of measurement with the advantage of low cost, short time of test and so on, and the online test of velocity field in furnaces will be likely to be realized. The Study Group the author study in have established the system for measurement of the cold aerodynamic field, which can correctly show the centre position of the tangential flow field, and get the basic situation of velocity distribution. Based on the predecessors'study, the author try to improve the system for measurement of cold aerodynamic field, so as to adapt to requirement of the thermal-state environment with high temperature, severe corrosion and loud noise, making a foundation for the industrial application of the acoustic measurement of aerodynamic field in furnace.Because of the fact that the electric loudspeaker is adopted for the cold-state experiment system as a sound source, which phonate with a signal generator. Although the level of sound pressure can up to 120dB, it is still hard to meet the requirement of hot state with high temperature, severe corrosion, and loud noise. Many scholars argue that the pneumatic sound source is feasible to be used in acoustic measurement in furnace. So, the author try to take the place of original electric sound source with the pneumatic. Four kind of pneumatic sound source device are adopted in the experiment. According to the acoustic characters analysis, it is found that the resonant cavity whistle is the best choice with the frequency from 1000-7000Hz, being louder than background noise in furnace and a good correlation feature.The resonant cavity whistle was used as the equipment of the system sound source. The experiments are carried out for the sound wave transmit time in single path. In order to simulate factual signal detected, the background noises of furnace were added to sound signal detected in the laboratory. A great number of experiment show that the measurement deviation is increased with the length increase of sound transmit path. The reasons lie in the attenuation of sound, leading to low the ratio of signal to noise. When the outlying signal's magnitude decline to the noise level, the deviation of tested transmitting time is obviously increased. But the deviation is lower than 13% in the range of 13m. As the sound becomes louder with a higher air pressure, it will be realized to meet the requirement of thermal-state fundamentally.