Fuel variability effect on flickering frequency of diffusion flames

Abstract

It is known that fuel variability of different gas suppliers may cause combustion instability in a gas turbine combustor. Mechanisms that control the time scale of the heat release oscillations and acoustic pressure perturbations are both physical and chemical in nature, and thus can be influenced by changes in fuel composition. The intent of this study is to investigate the fuel variability on the flickering frequency of diffusion flames in the hope of understanding some of the fundamental aspects of fuel variability effect on the dynamics of combustion. Experiments were conducted at atmospheric pressure with a matrix of methane and propane blends. An optical fibre system was applied to capture simultaneously the flame flickering at two different light frequencies (430 nm and 516 nm), which provided a means of comparing the chemistry change. It was found that the low frequency oscillation of flow and flame structures depended only weakly on the exit velocities of the fuel, while ambient conditions had a significant effect on flickering frequencies and spectrum. The results of using CH 4 and C 3 H 8 as test fuels at different flow rates showed very little variations, with peak frequencies at 11-13 Hz. When the jet flame was not disturbed, harmonics to at least the third mode were obtained in most of these cases. However, the cases which included CH 4 /C 3 H 8 splits of 90/10, 85/15 and 80/20 by volume showed that unstable flickering frequencies and flame harmonics were not observed. When a mixture of methane/propane at a ratio of 1:1 was used the peak flickering frequency was around 6 Hz, and slight disturbance in the environment would cause the harmonics to disappear. Mechanisms thought to produce changes in the dynamic response and frequency harmonics were discussed.

Investigation of the flame properties and fire behavior of carbon‐reinforced PEKK, BMI and phenolic composites impacted by Jet‐A1/air flames

“…The decrease in the temperature with the increase in thermocouple position may be attributed to the dissipation of heat energy and the decrease in the concentration of fuel and air as the flame gets away from the burner. The effect of the equivalence ratio was also observed, with changes in flame appearance due to buoyancy, which may have contributed to the observed temperature variations 36 . In this study, the calculated standard deviation was 0.5, demonstrating the high level of confidence in the temperature measurements and the overall reliability of the results.…”

“…The effect of the equivalence ratio was also observed, with changes in flame appearance due to buoyancy, which may have contributed to the observed temperature variations. 36 In this study, the calculated standard deviation was 0.5, demonstrating the high level of confidence in the temperature measurements and the overall reliability of the results. The flame temperature trends for both FAR (Table 2A) and AFR (Table 2B) equivalence ratios show how the heat output from the flame changes with the proportion of fuel and air in the combustion process.…”

Experimental investigations of the fire behavior of composites impacted by kerosene/air turbulent flame

“…The effect of the equivalence ratio was also observed, with changes in flame appearance due to buoyancy, which may have contributed to the observed temperature variations. 39 According to the equation model of Kang et al (2024) below whose work is aimed at accurately obtaining the temperature distribution of the flame which is crucial for a comprehensive understanding of the combustion behavior of the kerosene flame. The correction method is needed to compensate for the measurement error when the temperature is measured by a bare-bead K-type thermocouple in the open-fire experiment.…”

“…The effect of the equivalence ratio was also observed, with changes in flame appearance due to buoyancy, which may have contributed to the observed temperature variations. 39…”

Analysis of industrial flame characteristics and constancy study using image processing technique

“…Physical flame characteristics, i.e. its geometric and luminous parameters, temperature distribution or its oscillation frequency, provide detailed information about combustion efficiency and stability, which can be used to develop optimization strategies of monitoring and control algorithms [1][2][3][4][5][6]. Different research groups have investigated pulverized fuel flames by using advanced digital processing of flame images acquired with CCD (charge-coupled device) cameras, enabling the extraction of relevant flame features [7][8][9][10][11][12][13].…”