Investigation of noise radiation from a swirl stabilized diffusion flame with an array of microphones

•Acoustic spectral characteristics independent of equivalence ratio and flow velocity.•Combustion noise dependent on global equivalence ratio and flow velocity.•Increased global equivalence ratio decreased the frequency of peak.•Decay and growth coefficients largely independent of different flow conditions.•Acoustic radiation coherent up to 1.5kHz for spatially separated microphones. Next generation of combustors are expected to provide significant improvement on efficiency and reduced pollutants emission. In such combustors, the challenges of local flow, pressure, chemical composition and thermal signatures as well as their interactions will require detailed investigation for seeking optimum performance. Sensor networks with a large number of sensors will be employed in future smart combustors, which will allow one to obtain fast and comprehensive information on the various ongoing processes within the system. In this paper sensor networks with specific focus on an array of homogeneous microphones are used examine the spectral characteristics of combustion noise from a non-premixed combustor. A non-premixed double concentric swirl-flame burner was used. Noise spectra were determined experimentally for the non-premixed swirl flame at various fuel–air ratios using an array of homogeneous condenser microphones. Multiple microphones positioned at discrete locations around the turbulent diffusion flame, provided an understanding of the total sound power and their spectral characteristics. The growth and decay coefficients of total sound power were investigated at different test conditions. The signal coherence between different microphone pairs was also carried out to determine the acoustic behavior of a swirl stabilized turbulent diffusion flame. The localization of acoustic sources from the multiple microphones was examined using the noise spectra. The results revealed that integration of multiple sensors in combustors and reactors does allow one to obtain additional information which can be further tailored for the quest to develop advanced combustors.