Abstract:This paper deals with time series analysis on the emission of light from methane-air lean premixed flames. Planar flames formed on a flat burner at the equivalence ratio of unity; cellular flames formed at low equivalence ratios, because diffusive-thermal effects have a destabilizing impact in this range. We measured the light emission to get time series of intensity, and obtained the root mean square (RMS) and power spectrum density of the emission intensity normalized by its average value. The RMS increased … Show more
“…In the field of combustion science and physics, nonlinear time series analysis has been applied to the study of dynamic motion in a thermal pulse combustor, 10,11 detonation, 12 and cellar flames. 13 in recent years. Regarding the instability of swirling flames, the suitability of nonlinear time series analysis for characterizing the dynamic behavior of an unstable fluctuating flame front was demonstrated.…”
We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics. Periodic and chaotic behavior in combustion dynamics that can be observed as a result of combustion instabilities in fundamental and practical combustion systems are of importance to present-day combustion physics and nonlinear science research. In this paper, we experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. As the equivalence ratio / increases from 0.43 to 0.55, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. This is clearly demonstrated by a nonlinear time series analysis in combination with a surrogate data method, which has not been reported in details in previous fundamental combustion research. On the basis of the deterministic nature of the dynamic behavior extracted by the nonlinear time series analysis, a nonlinear forecasting method was performed to predict the time series of the pressure fluctuations. The short-term predicted pressure fluctuations obtained by updating the data library of the phase space coincide very closely with the measured pressure fluctuations, which shows that the nonlinear forecasting method we applied in this work has potential use for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor.
“…In the field of combustion science and physics, nonlinear time series analysis has been applied to the study of dynamic motion in a thermal pulse combustor, 10,11 detonation, 12 and cellar flames. 13 in recent years. Regarding the instability of swirling flames, the suitability of nonlinear time series analysis for characterizing the dynamic behavior of an unstable fluctuating flame front was demonstrated.…”
We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics. Periodic and chaotic behavior in combustion dynamics that can be observed as a result of combustion instabilities in fundamental and practical combustion systems are of importance to present-day combustion physics and nonlinear science research. In this paper, we experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. As the equivalence ratio / increases from 0.43 to 0.55, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. This is clearly demonstrated by a nonlinear time series analysis in combination with a surrogate data method, which has not been reported in details in previous fundamental combustion research. On the basis of the deterministic nature of the dynamic behavior extracted by the nonlinear time series analysis, a nonlinear forecasting method was performed to predict the time series of the pressure fluctuations. The short-term predicted pressure fluctuations obtained by updating the data library of the phase space coincide very closely with the measured pressure fluctuations, which shows that the nonlinear forecasting method we applied in this work has potential use for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor.
“…By performing FFT on the time series, he showed that the peak frequency is also lower at low equivalence ratios. This peak frequency is the same as the general frequency of premixed flames, mainly due to the shear current between hot burned gases and atmospheric gases 7 .…”
Section: Introductionmentioning
confidence: 58%
“…5 ). This range is included in similar articles, such as those by Kadovaki et al 7 . Figure 5 Spectral power diagram of a photodiode with an equivalence ratio of 0.79 and a heat capacity of 12.77 kW.…”
Section: Resultsmentioning
confidence: 99%
“…The detection of flame instability in premixed flames by time series analysis and using frequency analysis by the photodiode is done so that analyzing a set of typical oscillation frequencies (peak frequency) can be ratios of the same recognized currency in which the flame is unstable. The instability of premixed flames is observed in experiments as cellular flames 7 . The intrinsic instability of premixed flames mainly includes the hydrodynamic effects of thermal expansion between the flame fronts and the perturbation-temperature effects of mass penetration and overheat penetration (Lewis number less than one) 8 .…”
Radiation spectroscopy can be effective in identifying pollutants and species. By examining a photodiode, the frequency peaks obtained from the analysis, and the range in which the cell flame is converted to a surface flame, we obtained the value ratio of the cell flame to the surface flame in the range of 0.7–0.74 in different powers. The frequency peak in this range decreases from the maximum value of 9.9823 Hz to its minimum value of 9.058 Hz in different powers. By analyzing the temperature compared to the frequency peak, we found that in the range of equivalence ratio 0.7–0.75, the frequency peak decreases from 9.5 to 9.9 Hz to 8.7–9 Hz. The temperature has an increasing behavior, and in the equivalence ratio, the temperature is in the range of 1400–1500 °C, i.e., at its maximum value. We observed the cell formation process and its conversion to surface flame by flame detection. The flame height in the cellular and superficial regions is in the range of 0.65–0.85, which is the minimum flame height of 3–10 mm, and NO and CO were examined in the ratio of different equations and compared with temperature. In the ratio equivalence ratio of 0.77–0.81 in the temperature range of 1500 °C (maximum), the value of NO is about 16 ppm (maximum), and the value of CO is about 2 ppm (minimum). That is, when the temperature is at its maximum, it becomes CO minimum and NO maximum. This can be used for different applications such as similar and industrial burners.
“…This study focuses on the combustion of biogas because of wide applications in Thailand. In the past, the combustion of low-carbon fuel such as methane/air, butane/propane/air, and hydrogen/air [3][4][5] were investigated. In order to reduce the emission, the lean combustion was studied and found the effects of air/fuel ratio owing by thermal-diffusive instability [6][7].…”
Abstract.To compare the effects of biogas compositions, cellular premixed flames of synthetic biogas on flat burner was investigated. As the variation of main composition of biogas such as methane (CH4) and carbon dioxide (CO2), the biogas produced from agricultural waste (54.9:45.1), food waste (73.4:26.6) and cow dung (85.1:14.9) were used to investigate for this study. Moreover, the lean combustion system was experimented on flat burner to reduce the greenhouse gases. The variation of equivalence ratio between Φ=0.65-1.00 and firing rate with 45 L/min of mixture flow rates were studied. The results showed the cellular flame from agricultural waste, food waste and cow dung were found between Φ=0.75-1.00, Φ=0.70-0.90 and Φ=0.65-0.80, respectively. In addition, the blown off flames were also observed at Φ < 0.75, Φ < 0.70 and Φ < 0.65 from agricultural waste, food waste and cow dung compositions, respectively. The results showed the variation of biogas compositions, equivalence ratio and firing rate affected to cellular flames owing to the intrinsic instability. Moreover, it was concluded that small cell size, higher light emission and narrower unstable range and wider flame range obtained in the combustion of biogas produced from cow dung composition, was more stable compared to biogas from agricultural waste and food waste compositions.
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