| 摘要 |
PURPOSE:To improve the measuring accuracy of the internal volume, by detecting the acoustic pressure ratio or the phase difference of the detected sound waves in a plurality of acoustoelectric converters, measuring the internal volume to be measured based on the acoustic pressure ratio or the phase difference, thereby reducing the time change of microphones. CONSTITUTION:The sound wave of each frequency from a generator 31 is emitted from a speaker 33. The acoustic pressure ratio (p) between the positions of microphones 41 and 42 at this time is measured by a gain phase difference meter 47. A frequency fb at the time of resonance, i.e. the time when the acoustic pressure ratio (p) becomes the minimum value, is measured. Then the internal volume V0 of a combustion chamber 18 is obtained from an expression or a characteristic curve. The phase difference phi between the sound waves at the positions of the microphones 41 and 42 is measured by the gain phase difference meter 47, and the resonance frequency fb is obtained. The accuracy of this reading is better than the value obtained by the measurement of the acoustic pressure ratio (p). After the measurement of the resonance frequency, it is necessary to express the frequency by the value, which is converted at a reference temperature, e.g., 20 deg.C. Thus the measuring accuracy of the internal volume can be improved. |
