Investigation of Temperature Fluctuations and Acoustic Sources in a Non-Premixed Swirl Combustor with Heterogeneous Sensor Systems

摘要

Next generation combustors are expected to be significantly more efficient while reducing pollutants andeliminating carbon emissions. In such a combustor, the challenges of local flow, pressure, chemical compositionand thermal signatures as well as their interactions are far more complex to seek for optimum performance of thesystem. The current practice of using a single sensor to measure certain parameters at a single location cannotprovide sufficient information to achieve desirable and optimum overall performance of the combustor. A highdensity sensor network with a large number of sensors will be required by future smart combustors, which canprovide detailed information on the various ongoing processes within the system. As an initial step towards thedevelopment of such sensor networks, the effect of mean and fluctuating temperature distribution on the distributionof acoustic sources within the flame has been examined by using a thermocouple and an Electret condensermicrophone. A co- swirl diffusion flame burner was used for the present study that enabled the formation of differentflame types and shapes. The measurement of high frequency temperature signal allows for the observation ofcharacteristic mean and fluctuating temperatures, and thermal stratification characteristics within the flame. Thethermal characteristics data presented here provided a better insight on the thermal behavior of co-swirl diffusionflames. Noise spectra for varying air-fuel ratios were determined using an Electret condenser microphone. Resultsof time average and fluctuating temperature and sound pressure level spectra have shown that the source of noiseemission in flames was the region of maximum time random temperature fluctuations which in turn gives rise topressure fluctuations within the flame. The results are complemented with CFD simulations that supported thelocalization of the acoustic sources within the turbulent diffusion flames.