Experimental Study On Acoustic Characteristics Of Impinging Flame In Entrained-flow Gasifier And Hot-oxygen Flame Noise

Experimental study on impinging flame noise in enclosed space is made based on OMB bench-scale gasifier. Combined with acoustic theory and experimental data, composition of impinging flame noise is distinguished and characteristics of impinging flame noise is studied through analysis on frequency spectrums under different conditions. The influencing factors on flame noise in enclosed space is studied with combination of analysis on flame images, flame noise and pressure fluctuations. Finally the hot-oxygen CWS(Coal Water Slurry) gasification flame noise is studied. The conclusions are as follows:1. Impinging flame noise in enclosed space consists of jet flame noise, jet-flow noise and flame noise from impinging flame zone. The flame noise from impinging flame zone is proved through analysis on spectrums of flame noise and pressure fluctuations. Study on impinging flame noise with inequable oxygen speed between two nozzles is made and proved that the impinging flame with equable speed has better stability. Impinging flame noise with four nozzles is more stable and louder than that with2nozzles.2. The influencing factors on impinging flame noise in gasifier is studied through CWS gasification experiments. The results show that the flame noise corresponds with flame pulse and pressure field around in gasifier. The unsteady heat transfer caused by the uniform component concentration in flame with low [O/C] ratio results in the vortex shedding with high amplitude, which induces the flame pulse and generates pressure fluctuations and flame noise with high amplitude. With the increase of oxygen speed, the flame pulse frequency and flame noise decrease, and the flame tends to be stable. And the flame is distorted by the amplified shear force caused by flame and high speed oxygen with the higher oxygen speed, causing the flame pulse with high frequency and amplitude, and the flame noise and pressure fluctuations are also enhanced.3. The special frequency peak in frequency spectrums of hot-oxygen gasification flame noise in open space can be observed obviously. With the increase of [O/C] ratio, the stability of hot-oxygen flame increases, the amplitude of special frequency peak decreases and flame noise decreases. The process of flame tending to be stable is accelerated when the mass flow rate of fuel increases and the gasification process is promoted. Hot-oxygen flame noise is on the rise with the increase of [O/C] ratio and the status of combustion becomes severe in enclosed space. So the hot-oxygen CWS gasification process and status of flame could be diagnosed with analysis on frequency in spectrums of flame noise.