HOMOGENEOUS AND HETEROGENEOUS SENSORS FOR COMBUSTION SYSTEMS
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Due to increasingly stringent emission regulations, it is important to develop clean combustors. Combustion behavior is very complex in almost all practical power plant systems. Measurement of temperature, pressure, local flow, and chemical composition inside the flame provides critical information to develop cleaner combustors. This would result in significant improvement in energy efficiency and reduce the environmental impact. A high density sensor network system would assist in understanding the various ongoing processes occurring within the combustors. This dissertation is focused on how much additional information can be gathered from multiple sensors. Four different time delay estimation methods (using cross correlation, phase transform, generalized cross correlation with maximum-likelihood estimation, and average square difference function) were examined using two sensors. Phase transform offered better results to calculate the time delay between a given pair of microphones. This has the potential to determine local noise generation sources from within flows and flames with the additional information on local noise generation source. As a step towards the development of a sensor network, different sensors were examined. A micro-thermocouple, microphone and microphone probes were utilized to enhance understanding of the flame with detailed information on the various ongoing processes in a premixed swirl flame. High frequency temperature and pressure measurements were used to identify the thermal and acoustic characteristics of the flame and combustor. The local distributions of fluctuating pressure and temperature were measured in different regions, in and around the flame. Pressure fluctuation showed significant variation in different directions for the combustive case relative to non-combustive flow. Also a comparison of the pressure and temperature fluctuations revealed that maximum temperature fluctuations occur mostly near to the visible flame boundary while maximum pressure fluctuation occur further away from the flame. Acoustic data from the premixed swirl combustor showed variation in fuel to air ratio changes the spatial distribution of noise as measured by different sensors placed around the combustor. A comparison of different sensors showed that a single sensor does not capture all the information with changes in fuel to air ratio.