Exploratory Study On Acoustic Transducers With Acoustic Ducts In High-temperature

Thermodynamic temperature is one of the seven fundamental physical quantities in theInternational System of Units(SI), with the unit K, which is the scale of the material energy ofthermal motion. International temperature scale(ITS) is the approximation of thermodynamictemperature, therefore, accurate measurement of thermodynamic temperature is the physicalfoundation formulated or revised ITS. At present, acoustic thermometer is one of thereference methods to determine the thermodynamic temperature unit, which has the smallestuncertainty of measurement in all reference methods. In the current international temperaturemeasurement field, thermodynamic temperature measurement value of the acousticthermometer has an important effects on the ITS revised. In the paper, based on the acousticresonance method of fixed-path-length cylindrical, designed the thermodynamic temperaturemeasurement of high temperature zone device. By measuring the stability resonantfrequencies of cavity, analyzed the random deviation of frequency.The principle of acoustic thermometer is use the relationship between the ideal gasvelocity of single atomic gas and temperature to obtain thermodynamic temperature, which isacquired by measuring the resonant frequencies and size of cavity. Therefore, the acoustic andmicrowave resonant frequencies measurement are one of the key problems in the acousticthermometer. The commercially manufactured capacitive microphones and piezoelectrictransducers are unable to meet the requirements of high temperature measurement, so the firstquestion is to resolve acoustic sensor, which apply to the high temperature region.The piezoelectric ceramic(PZT) and condenser microphone are compared, themicrophone has higher sensitivity as the receiver through the experiment measurement. ThePZT has higher excitation voltage as the resource. Then, founded a suitable method ofacoustic sensor coupled with duct by experiment. Using this method, measured the acousticfrequency at the ambient temperature and50~500kPa. The random deviation of resonancefrequencies were less than2×10-6for the four pure axial modes(200~500). The experimentsshowed that the method is feasible, which uses a duct to conduct sound from a remote PZT at ambient temperature into a cavity resonator and a second duct to conduct sound out of thecavity to a remote sound detector at ambient temperature. Subsequently, design ahigh-temperature resonator cavity and other systems, compile the relevant pressure,temperature and frequency measurement procedures based on the labview software,implementation to the experiment of automatic control and data acquisition processing. At600K，673K,773K and873K, launched the experiment into acoustic resonance frequency andsignal-to-noise. The data suggest that the random deviation of resonance frequency of singlemode is superior to10×10-6. In addition, the study demonstrates the availability of the roomtemperature acoustic transducers for high-temperature thermometry.