Heat Release Rate Measurements in Premixed Flames using Chemiluminescence and Reaction Rate Imaging

2006 ◽  
Author(s):  
Yannis Hardalupas ◽  
Christos Panoutsos ◽  
Alexander Taylor
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Reaction Rate ◽  
Premixed Flames

scholarly journals Heat release rate correlation and combustion noise in premixed flames

2011 ◽  
Vol 681 ◽  
pp. 80-115 ◽  
Author(s):  
N. SWAMINATHAN ◽  
G. XU ◽  
A. P. DOWLING ◽  
R. BALACHANDRAN
Keyword(s):  
Spatial Distribution ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Time Scale ◽  
Reaction Rate ◽  
Laminar Flame ◽  
Premixed Flames ◽  
Length Scale ◽  
Turbulent Premixed Flames

The sound emission from open turbulent flames is dictated by the two-point spatial correlation of the rate of change of the fluctuating heat release rate. This correlation in premixed flames can be represented well using Gaussian-type functions and unstrained laminar flame thermal thickness can be used to scale the correlation length scale, which is about a quarter of the planar laminar flame thermal thickness. This correlation and its length scale are observed to be less influenced by the fuel type or stoichiometry or turbulence Reynolds and Damkohler numbers. The time scale for fluctuating heat release rate is deduced to be about τc/34 on an average, where τc is the planar laminar flame time scale, using direct numerical simulation (DNS) data. These results and the spatial distribution of mean reaction rate obtained from Reynolds-averaged Navier–Stokes (RANS) calculations of open turbulent premixed flames employing the standard model and an algebraic reaction rate closure, involving a recently developed scalar dissipation rate model, are used to obtain the far-field sound pressure level from open flames. The calculated values agree well with measured values for flames of different stoichiometry and fuel types, having a range of turbulence intensities and heat output. Detailed analyses of RANS results clearly suggest that the noise level from turbulent premixed flames having an extensive and uniform spatial distribution of heat release rate is low.

scholarly journals Predicting the consumption speed of a premixed flame subjected to unsteady stretch rates

2021 ◽  
Author(s):  
Meysam Sahafzadeh ◽  
Seth B. Dworkin ◽  
Larry W. Kostiuk
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Time Scale ◽  
Transfer Functions ◽  
Laminar Flame ◽  
Premixed Flames ◽  
Turbulent Flames ◽  
Response Analysis ◽  
Phase Lag

The stretched laminar flame model provides a convenient approach to embed realistic chemical kinetics when simulating turbulent premixed flames. When positive-only periodic strain rates are applied to a laminar flame there is a notable phase lag and diminished amplitude in heat release rate. Similar results have being observed with respect to the other component of stretch rate, namely the unsteady motion of a curved flame when the stretch rates are periodic about zero. Both cases showed that the heat release rate or consumption speed of these laminar-premixed flames vary significantly from the quasi-steady flamelet model. Deviation from quasi-steady behaviour increases as the unsteady flow time scale approaches the chemical time scale that is set by the stoichiometry. A challenge remains in how to use such results predictively for local and instantaneous consumption speed for small segments of turbulent flames where their unsteady stretch history is not periodic. This paper uses a frequency response analysis as a characterization tool to simplify the complex non-linear behaviour of premixed methane air flames for equivalence ratios from 1.0 down to 0.7, and frequencies from quasi-steady up to 2000 Hz using flame transfer functions. Various linear and nonlinear models were used to identify appropriate flame transfer functions for low and higher frequency regimes, as well as extend the predictive capabilities of these models. Linear models were only able to accurately predict the flame behaviour below a threshold of when the fluid and chemistry time scales are the same order of magnitude. Other proposed transfer functions were tested against arbitrary multi-frequency stretch inputs and were shown to be effective over the full range of frequencies.

On the correlation of heat release rate in turbulent premixed flames

2011 ◽  
Vol 33 (1) ◽  
pp. 1533-1541 ◽  
Author(s):  
N. Swaminathan ◽  
R. Balachandran ◽  
G. Xu ◽  
A.P. Dowling
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed

Response of Heat Release Rate to Flame Straining in Swirling Hydrogen-Air Premixed Flames

2020 ◽  
Vol 104 (2-3) ◽  
pp. 451-478
Author(s):  
Kozo Aoki ◽  
Masayasu Shimura ◽  
JoonHwi Park ◽  
Yuki Minamoto ◽  
Mamoru Tanahashi
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames

Spatially resolved heat release rate measurements in turbulent premixed flames

2006 ◽  
Vol 144 (1-2) ◽  
pp. 1-16 ◽  
Author(s):  
B.O. Ayoola ◽  
R. Balachandran ◽  
J.H. Frank ◽  
E. Mastorakos ◽  
C.F. Kaminski
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames ◽  
Turbulent Premixed Flames ◽  
Spatially Resolved ◽  
Turbulent Premixed

scholarly journals Investigation of flame behavior and dynamics prior to lean blowout in a combustor with varying mixedness of reactants for the early detection of lean blowout

2018 ◽  
Vol 11 ◽  
pp. 175682771881251 ◽  
Author(s):  
Somnath De ◽  
Arijit Bhattacharya ◽  
Sirshendu Mondal ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames ◽  
Early Prediction ◽  
Lean Blowout ◽  
Partially Premixed Flames ◽  
Rate Oscillations ◽  
Partially Premixed ◽  
Flame Behavior

Lean blowout is one of the major challenges faced when the gas turbine combustors are operated with lean fuel–air mixture to meet the emission norm. We experimentally study the flame behavior and the dynamics of heat release rate fluctuations during a transition to lean blowout. The study comprising flame visualization and estimating several measures to predict lean blowout for both premixed and partially premixed flames (using fuel ports F1 to F5) in a swirl stabilized dump combustor. To that end, we acquire unsteady heat release rate in terms of CH* chemiluminescence obtained through a photomultiplier tube with a narrow band-pass filter. For evaluating different statistical measures, we use National Instrument Labview software while acquiring the heat release rate oscillations. For premixed and partially premixed flames, such measures and the flame behavior show a different and, in some cases, even opposite trends as lean blowout is approached. However, in both premixed and partially premixed flames, the mean and root mean square values of the heat release rate fluctuation decrease as we decrease the equivalence ratio. Further, we show that the value of mean frequency calculated using Hilbert transform of the heat release rate fluctuations is a good indicator of lean blowout. Apart from the early prediction of lean blowout, different statistics of heat release rate oscillations, such as kurtosis and skewness, are shown to identify only the occurrence of lean blowout for premixed (F1 and F2) and flames with lower level of premixing (F3). They are not useful for the flames with high levels of unmixedness like F4 and F5. On the other side, probability density function is seen useful for both premixed and partially premixed flames. In short, we present the relative importance of different measures stated earlier for the identification and early prediction of lean blowout for both premixed and partially premixed flames.

Assessment of Chemical Markers for Heat-Release Rate Correlations in Laminar Premixed Flames

2013 ◽  
Vol 185 (10) ◽  
pp. 1482-1508 ◽  
Author(s):  
Anna Gazi ◽  
George Vourliotakis ◽  
George Skevis ◽  
Maria A. Founti
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames ◽  
Chemical Markers

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

2013 ◽  
Author(s):  
Poravee Orawannukul ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Reconstruction Technique ◽  
Chemiluminescence Intensity ◽  
Lean Premixed ◽  
Rate Of Heat Release

Knowledge of the effects of inlet velocity and inlet equivalence ratio fluctuations on the rate of heat release 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. The flame in an actual lean premixed combustor is referred to as a technically premixed flame and is exposed to both velocity and equivalence ratio fluctuations. Under these conditions the chemiluminescence intensity does not provide a reliable measure of the flame’s rate of heat release. The objective of this work is to experimentally assess the validity of a technique for making heat release rate measurements 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 the heat release rate fluctuations in an air-forced technically premixed, the heat release reconstruction is validated indirectly by comparing measured to reconstructed chemiluminescence intensity fluctuations. Results are reported for a range of operating conditions and forcing frequencies which demonstrate the capabilities and limitations of this technique. A variation of this technique, referred to as a reverse reconstruction, is proposed which does not require a measurement of the fuel-forced flame transfer function. The air-forced flame transfer function gain and phase obtained using the reverse reconstruction technique are presented and compared to the results from the direct reconstruction technique.

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