A STUDY OF THE ACOUSTICAL TERMINATION ON PRACTICAL GAS PULSATION MEASUREMENT

It has been well recognized in the past that an anechoic termination, which can effectively eliminate the reflective acoustic wave, is required for measurement of exhaust gas pulsation from engines or machinery. In academic environment, the acoustic termination on the exhaust line can be well controlled by appropriate treatment. However, it is not unusual in practical industrial applications that the anechoic termination is not available. Therefore, a theoretical investigation was performed in order to understand the impact on the gas pulsation measurement without an anechoic termination. A simplified model of an exhaust line with different acoustic terminations was analyzed by both analytical and experimental approaches. Both one-microphone and two-microphone measurement methods, which are commonly used, were evaluated. The results clearly demonstrate that without an anechoic termination, the variations of the measurements will be substantial due to the reflective acoustic wave, as has been argued for years in the industry.