<title>Sensors for measuring primary zone equivalence ratio in gas turbine combustors</title>

Abstract

In lean-premixed combustion, the narrow range of operating conditions where stable, low-emissions combustion, is achieved make it necessary for a fuel-air equivalence ratio sensor to be incorporated into the combustor. Such a sensor should be capable ofdeterminining nozzle-to-nozzle variations in the equivalence ratio, and have a reasonably fast response time so that the control mechanism can meter the flowrates accordingly. This paper describes the development ofa flame chemilummescence based equivalence ratio sensor, which can be installed in the individual nozzles ofa gas turbine combustor. The first stage ofthe development involves studying the chemiluminescence characteristics of CH* and CO2 in a dump combustor. It was observed that fuel-air mixedness does not affect the overall flame chemiluminescence, and inlet temperature variations over 50 K have not produced discernible differences in the chemiluminescence intensities. Combustor velocities do affect the flame chemiluminescence intensities, and this parameter has to be taken into account while developing the sensor. An optical fibre based sensor, which can be easily installed in a combustor, has been designed. Based on this study, a methodology for determining the equivalence ratio from the chemiluminescent intensities and flowrates is proposed for use with the sensor under development.

Basic aspects of OH(A), CH(A), and C2(d) chemiluminescence in the reaction zone of laminar methane–air premixed flames

“…Chemiluminescence-based fuel-air ratio measurements are becoming a standard approach in industrial applications as several researchers have employed this technique in internal combustion engines and model gas turbine combustors [9][10][11][12][13]. A principle idea for the chemiluminescence-based F/A sensing is to use the ratio of the chemiluminescence intensity of one species to another such as OH(A) to CH(A) [11,14,15].…”

Effect of fuel type on equivalence ratio measurements using chemiluminescence in premixed flames

“…As a consequence, the normalisation of the chemiluminescent intensity by the fuel mass flowrate has been commonly used in the literature. However, flame strain rate and/or high turbulence levels can also influence flame chemistry and introduce non-linear effects between emitted intensity and mass flowrate [22][23][24][25]. In the present study, Reynolds number is in the range 4000-8000 and the flow is mildly turbulent.…”

Characteristics of Gliding Arc Plasma and Its Application in Swirl Flame Static Instability Control

“…For example, CH2O is the symbol of the preheat region, OH represents the high-temperature region [34], and CH is regarded as the indicator of the flame front [35]. According to previous research [36][37][38], CH could better reflect the local or global heat release rate. In the experiment, the high-speed camera with bandpass filter was used to capture the instantaneous structure of CH radical, which could reveal the distribution of heat release rate in both pulsating flow mode and plasma-pulsating flow mode, as shown in Figure 16.…”