A turbulent combustion noise model

Abstract

A turbulent combustion noise model based on first principles is developed in this thesis. The model predicts (1) the pressure time series, (2) Sound Pressure Level (SPL) spectrum, (3) Over-All Sound Pressure Level (OASPL), (4) the thermoacoustic efficiency, (5) the peak frequency, and (6) the sound power of combustion generated noise. In addition, a correlation for sound power is developed based on fundamental burner and fuel variables known to affect the acoustic characteristics of turbulent combustion. The predicted pressure time series exhibits consistency with reality in that it has no steady component. It also confirms speculation in the literature that the predominant noise mechanism in open turbulent flames results from a "transition burning" phenomenon at the flame front. The predicted Sound Pressure Level spectrum, Over-All Sound Pressure Level, and the thermoacoustic efficiency are in excellent agreement with the results available in the literature. The shifts in the peak frequency with basic burner and fuel parameters are consistent with experimental observations from the literature. The disagreements between the predicted and the observed exponents of fuel and burner parameters for sound power are shown to be well within the standard deviation of the experimental observations. Certain areas for further analytical research on the combustion noise mechanism are identified.