Abstract
A measurement technique for determination of the global and local equivalence ratios from the flame chemiluminescence for a swirl-stabilized lean premixed combustion of natural gas and kerosene is presented. First, we conducted spectrally resolved chemiluminescence studies using an imaging spectrometer to correlate the ratio of individual chemiluminescence signals to the equivalence ratio. Flame spectra were recorded for a multitude of different lean operating conditions for natural gas and kerosene combustion. The spectra show that, without background correction, the CH*/CO2* ratios for both natural gas and kerosene combustion exhibited a monotonic relationship to the equivalence ratio in the investigated range. Subsequently, bandpass-filtered images of CH* and CO2* chemiluminescence were acquired simultaneously on one camera chip using an image doubler to investigate the local relationship of the CH*/CO2* ratio with the equivalence ratio. The ratio images corroborate the monotonic relationship of the CH*/CO2* ratio to the equivalence ratio. Furthermore, the ratio was found to be influenced by the local reaction zone temperature. The presented technique allows high temporal resolution determination of the local equivalence ratio in lean premixed natural gas and kerosene flames and can thus be applied to quantify equivalence ratio oscillations during unstable combustion.
Highlights
Lean premixed combustion is utilized in modern gas turbine systems to reduce nitrogen oxide emissions and comply with current emissions regulations
The spectra show that, without background correction, the CH*/CO2* ratios for both natural gas and kerosene combustion exhibited a monotonic relationship to the equivalence ratio in the investigated range
This paper introduces an optical measurement method for quantifying global and local equivalence ratios in the reaction zone of a dual fuel burner for natural gas and kerosene based on the measurement of CH* and CO2* chemiluminescence of the flame
Summary
Lean premixed combustion is utilized in modern gas turbine systems to reduce nitrogen oxide emissions and comply with current emissions regulations. Lean premixed combustion is susceptible to the formation of thermoacoustic instabilities caused by a coupling between acoustic waves in the combustion chamber and fluctuations in the heat release rate [1]. Previous studies of lean premixed combustion dynamics in gas turbine engines have revealed that the fluctuations in the heat release rate are attributable to two coupling mechanisms [4,5]. Thermoacoustic instabilities are driven by acoustically induced velocity fluctuations at the burner outlet. In technically premixed combustion systems, equivalence ratio fluctuations were found to be an important driver in triggering thermoacoustic instabilities
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