Optical Transfer Function Measurements for a Swirl Burner at Atmospheric Pressure

Guyot, Daniel; Paschereit, Christian Oliver

doi:10.2514/6.2009-5413

Cited by 3 publications

(4 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mean heat releaseq increases strongly too, consistent with observations reporting a power-law variation of I OH * with Φ (e.g. exponent 4.93 in [10] and 5.23 in [11]). Figure 2(c) shows the probability density function (PDF) P ( p 1 ) of the filtered acoustic pressure, which evolves continuously from unimodal (single peak centred around p 1 = 0) for Φ ≤ 0.532, to bimodal (two symmetric peaks centred around finite values | p 1 | > 0) for Φ ≥ 0.538, typical of stable systems (noise-driven fixed point) and unstable systems (noise-driven limit cycle), respectively.…”

Section: Experimental Measurementssupporting

confidence: 88%

Quantifying acoustic damping using flame chemiluminescence

Boujo¹,

Денисов

Schuermans³

et al. 2016

J. Fluid Mech.

View full text Add to dashboard Cite

Thermoacoustic instabilities in gas turbines and aeroengine combustors falls within the category of complex systems. They can be described phenomenologically using nonlinear stochastic differential equations, which constitute the grounds for output-only model-based system identification. It has been shown recently that one can extract the governing parameters of the instabilities, namely the linear growth rate and the nonlinear component of the thermoacoustic feedback, using dynamic pressure time series only. This is highly relevant for practical systems, which cannot be actively controlled due to a lack of costeffective actuators. The thermoacoustic stability is given by the linear growth rate, which results from the combination of the acoustic damping and the coherent feedback from the flame. In this paper, it is shown that it is possible to quantify the acoustic damping of the system, and thus to separate its contribution to the linear growth rate from the one of the flame. This is achieved by post-processing in a simple way simultaneously acquired chemiluminescence and acoustic pressure data. It provides an additional approach to further unravel from observed time series the key mechanisms governing the system dynamics. This straightforward method is illustrated here using experimental data from a combustion chamber operated at several linearly stable and unstable operating conditions.

show abstract

Section: Experimental Measurementssupporting

confidence: 88%

Quantifying acoustic damping using flame chemiluminescence

Boujo¹,

Денисов

Schuermans³

et al. 2016

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…Numerous experimental studies of lean premixed flames have shown that the global chemiluminescence intensity increases linearly with increasing velocity at a fixed equivalence ratio [12]; in other words, with the increasing heat release rate. Similarly, it has been observed that the global chemiluminescence intensity increases nonlinearly with the increasing equivalence ratio at a fixed inlet velocity [11,15], which again corresponds to the increasing heat release rate. Therefore, the relationship between the intensity of the chemiluminescence emission and the heat release rate depends on whether the change in th heat release rate is the result of a change in the inlet velocity, as in the mixture-forced tests, or a change in the inlet equivalence ratio, as in the fuel-forced tests.…”

Section: Introductionmentioning

confidence: 89%

“…The technique that is used to measure the fluctuation in the flame's rate of heat release is based on the flame's chemiluminescence emission [7][8][9][10][11][12][13][14][15]. Numerous experimental studies of lean premixed flames have shown that the global chemiluminescence intensity increases linearly with increasing velocity at a fixed equivalence ratio [12]; in other words, with the increasing heat release rate.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Validation of Heat Release Rate Fluctuation Measurements in Technically Premixed Flames

Orawannukul¹,

Quay²,

Santavicca

2013

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

Understanding the effects of inlet velocity and inlet equivalence ratio fluctuations on heat release rate fluctuations in lean premixed gas turbine combustors is essential for predicting combustor instability characteristics. This information is typically obtained from independent velocity-forced and fuel-forced flame transfer function measurements, where the global chemiluminescence intensity is used as a measure of the flame's overall rate of heat release. Current lean premixed combustors operate in a technically premixed mode where the flame is exposed to both velocity and equivalence ratio fluctuations and, as a result, the chemiluminescence intensity does not provide an accurate measure of the flame's rate of heat release. The objective of this work is to experimentally assess the validity of a technique for measuring heat release rate fluctuations in technically premixed flames based on the linear superposition of fuel-forced and velocity-forced flame transfer function measurements. In the absence of a technique for directly measuring heat release rate fluctuations in technically premixed flames, the heat release rate reconstruction is validated indirectly by comparing measured and reconstructed chemiluminescence intensity fluctuations. The results are reported for a range of operating conditions and forcing frequencies which demonstrate the capabilities and limitations of the heat release rate reconstruction technique. A variation of this technique, referred to as a reverse reconstruction, is also proposed, which does not require a measurement of the fuel-forced flame transfer function. The results obtained using the reverse reconstruction technique are presented and compared to the results from the direct reconstruction technique.

show abstract

“…Several approaches to use these relations for the calculation of the integral heat release rate have been conducted, either by only using one species (e.g., Ref. [15]) or multiple chemiluminescent species at atmospheric pressure [20,21] and full engine pressure [22].…”

Section: Introductionmentioning

confidence: 99%

Optical Measurement of Local and Global Transfer Functions for Equivalence Ratio Fluctuations in a Turbulent Swirl Flame

Bobusch¹,

Ćosić²,

Moeck³

et al. 2013

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

Equivalence ratio fluctuations are known to he one of the key factors controlling thermoacoustic stability in lean premixed gas turbine combustors. The mixing and thus the spatiotemporal evolution of these perturbations in the combustor flow is, however, difficult to account for in present low-order modeling approaches. To investigate this mechanism, experiments in an atmospheric combustion test rig are conducted. To assess the importance of equivalence ratio fluctuations in the present case, flame transfer functions for different injection positions are measured. By adding known perturbations in the fuel flow using a solenoid valve, the influence of equivalence ratio oscillations on the heat release rate is investigated. The equivalence ratio fluctuations in the reaction zone are measured spatially and temporally resolved using two optical chemiluminescence signals, captured with an intensifled camera. A steady calibration measurement allows for the quantitative assessment of the equivalence ratio fluctuations in the flame. This information is used to obtain a mixing transfer function, which relates fluctuations in the fuel flow to corresponding fluctuations in the equivalence ratio of the flame. The current study focuses on the measurement of the global, spatially integrated, transfer function for equivalence ratio fluctuations and the corresponding modeling. In addition, the spatially resolved mixing transfer function is shown and discussed. The global mixing transfer function reveals that, despite the good spatial mixing quality of the investigated generic burner, the ability to damp temporal fluctuations at low frequencies is rather poor. It is shown that the equivalence ratio fluctuations are the governing heat release rate oscillation response mechanism for this burner in the low-frequency regime. The global transfer function for equivalence ratio fluctuations derived from the measurements is characterized by a pronounced low-pass characteristic, which is in good agreement with the presented convection-diffusion mixing model.

show abstract

Optical Transfer Function Measurements for a Swirl Burner at Atmospheric Pressure

Cited by 3 publications

References 12 publications

Quantifying acoustic damping using flame chemiluminescence

Quantifying acoustic damping using flame chemiluminescence

An Experimental Validation of Heat Release Rate Fluctuation Measurements in Technically Premixed Flames

Optical Measurement of Local and Global Transfer Functions for Equivalence Ratio Fluctuations in a Turbulent Swirl Flame

Contact Info

Product

Resources

About