実験的音響特性評価による排気ダクト延長型ガス給湯器の熱音響不安定性診断

抄録

During the operation of gas water heaters, a self-excited oscillation phenomenon known as combustion oscillation may occur, where the combustion reaction excites acoustic oscillations of the gas at the system's eigenfrequencies. Combustion oscillation can generate noise and compromise safety and reliability. Even gas water heaters tested to avoid combustion oscillation may still experience it if the exhausting duct shape is altered to meet practical requirements. During the development phase, repeated tests are necessary to ensure stability across various duct configurations, which can be time-consuming. To address this issue, we propose a method of diagnosing combustion oscillation in gas water heaters with only minimal experimentation. We experimentally determine the frequency dependence of the acoustic impedance of a household gas water heater, which is then used to estimate the natural oscillation frequency when an exhausting duct of arbitrary length is attached. Additionally, the energy balance between the acoustic power supplied by the gas water heater and the acoustic power dissipated in the duct is evaluated using the measured acoustic impedance. Verification experiments confirmed the occurrence of combustion oscillations at the predicted duct lengths and frequencies.