Study On Acoustic Diagnosis And Acoustic Characteristic Of Air-blast Atomization Flame

Based on the close relationship between acoustic characteristics and combustion states of flame, air-blast atomization flame noise was studied. Combined with acoustic theory and experimental data, the sound pressure distribution, the spectrum characteristic and the generation mechanism of air-blast atomization flame were analyzed comprehensively. The changes of flame noise were studied and the reasons were analyzed by changing the structure of burner and liquid fuel types. Water-cooled jacket was designed for flame noise measurement in gasifier, the flame noise characteristic in gasifier was analyzed and the effects of reverberation in gasifier, sound transmission in pipe and water-cooled jacket on noise spectrum were analyzed. Eigenvalue TE was obtained to diagnose the combustion condition in gasifier. The main conclusions are as follows:1. Sound pressure distribution of different flame length shows the same rule, and with the increase of flame length, the direction of flame noise is more obvious and the noise intensity is greater. Flame turbulence causes greater noise intensity and wider frequency distribution. Main peak frequency of turbulent atomization flame noise is generated from the flame front, and high frequency noise is produced from the total flame part. The generation mechanism of turbulent atomization flame noise is related to the scale and the burst frequency of vortex.2. The atomization flame noise of 30°and 45°jet angle nozzle is low-frequency noise with main frequency around 50Hz, and the noise of 60°jet angle nozzle is high-frequency noise with main frequency around 3000Hz.45°jet angle nozzle has a better flame stability and produce a lower flame noise. The type of fuel has a little effect on sound pressure level of spray noise and has a great impact on atomization flame noise. The flame noise of diesel combustion is much higher than noise of alcohol and kerosene combustion.3. Four nozzles impinging in gasifier causes less low-frequency energy and more stable flame. The characteristic peak amplitude was used as the eigenvalue of each spectrum which was called TE. The changes of combustion conditions in gasifier can be diagnosed by analyzing the changes in eigenvalue TE.