Determination of the Heat Release Distribution in Turbulent Flames by a Model Based Correction of OH* Chemiluminescence

Imaging of OH* or CH* chemiluminescence with intensified cameras is often employed for the determination of heat release in premixed flames. Proportionality is commonly assumed, but in the turbulent case this assumption is not justified. Substantial deviations from proportionality are observed, which are due to turbulence-chemistry interactions. In this study a model based correction method is presented to obtain a better approximation of the spatially resolved heat release rate of lean turbulent flames from OH* measurements. The correction method uses a statistical strain rate model to account for the turbulence influence. The strain rate model is evaluated with time-resolved velocity measurements of the turbulent flow. Additionally, one-dimensional simulations of strained counterflow flames are performed to consider the nonlinear effect of turbulence on chemiluminescence intensities. A detailed reaction mechanism, which includes all relevant chemiluminescence reactions and deactivation processes, is used. The result of the simulations is a lookup table of the ratio between heat release rate and OH* intensity with strain rate as parameter. This lookup table is linked with the statistical strain rate model to obtain a correction factor which accounts for the nonlinear relationships between OH* intensity, heat release rate, and strain rate. The factor is then used to correct measured OH* intensities to obtain the local heat release rate. The corrected intensities are compared to heat release distributions which are measured with an alternative method. For all investigated flames in the lean, partially premixed regime the corrected OH* intensities are in very good agreement with the heat release rate distributions of the flames.

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Determination of the Heat Release Distribution in Turbulent Flames by a Model Based Correction of OH* Chemiluminescence

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2011-45105 ◽

2011 ◽

Cited By ~ 9

Author(s):

Martin Lauer ◽

Mathieu Zellhuber ◽

Thomas Sattelmayer ◽

Christopher J. Aul

Keyword(s):

Strain Rate ◽

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Correction Method ◽

Turbulent Flames ◽

Lookup Table ◽

Rate Model ◽

Non Linear

Imaging of OH* or CH* chemiluminescence with intensified cameras is often employed for the determination of heat release in premixed flames. Proportionality is commonly assumed, but in the turbulent case this assumption is not justified. Substantial deviations from proportionality are observed, which are due to turbulence-chemistry interactions. In this study a model based correction method is presented to obtain a better approximation of the spatially resolved heat release rate of lean turbulent flames from OH* measurements. The correction method uses a statistical strain rate model to account for the turbulence influence. The strain rate model is evaluated with time-resolved velocity measurements of the turbulent flow. Additionally, one-dimensional simulations of strained counterflow flames are performed to consider the non-linear effect of turbulence on chemi-luminescence intensities. A detailed reaction mechanism, which includes all relevant chemiluminescence reactions and deactivation processes, is used. The result of the simulations is a lookup table of the ratio between heat release rate and OH* intensity with strain rate as parameter. This lookup table is linked with the statistical strain rate model to obtain a correction factor which accounts for the non-linear relationships between OH* intensity, heat release rate, and strain rate. The factor is then used to correct measured OH* intensities to obtain the local heat release rate. The corrected intensities are compared to heat release distributions which are measured with an alternative method. For all investigated flames in the lean, partially premixed regime the corrected OH* intensities are in very good agreement with the heat release rate distributions of the flames.

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On the Adequacy of Chemiluminescence as a Measure for Heat Release in Turbulent Flames With Mixture Gradients

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4000126 ◽

2010 ◽

Vol 132 (6) ◽

Cited By ~ 61

Author(s):

Martin Lauer ◽

Thomas Sattelmayer

Keyword(s):

Heat Release ◽

Wavelength Range ◽

Heat Release Rate ◽

Turbulence Intensity ◽

Release Rate ◽

Reference Method ◽

Turbulent Flames ◽

First Law Of Thermodynamics ◽

Spatially Resolved

The determination of the heat release in technical flames is commonly done via bandpass filtered chemiluminescence measurements in the wavelength range of OH∗ or CH∗ radicals, which are supposed to be a measure for the heat release rate. However, these indirect heat release measurements are problematic because the measured intensities are the superposition of the desired radical emissions and contributions from the broadband emissions of CO2∗. Furthermore, the chemiluminescence intensities are strongly affected by the local air excess ratio of the flame and the turbulence intensity in the reaction zone. To investigate the influence of these effects on the applicability of chemiluminescence as a measure for the heat release rate in turbulent flames with mixture gradients, a reference method is used, which is based on the first law of thermodynamics. It is shown that although the integral heat release can be correlated with the integral chemiluminescence intensities, the heat release distribution is not properly represented by any signal from OH∗ or CH∗. No reliable information about the spatially resolved heat release can be obtained from chemiluminescence measurements in flames with mixture gradients.

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On the Adequacy of Chemiluminescence as a Measure for Heat Release in Turbulent Flames With Mixture Gradients

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-59631 ◽

2009 ◽

Cited By ~ 4

Author(s):

Martin Lauer ◽

Thomas Sattelmayer

Keyword(s):

Heat Release ◽

Wavelength Range ◽

Heat Release Rate ◽

Turbulence Intensity ◽

Release Rate ◽

Reference Method ◽

Turbulent Flames ◽

First Law Of Thermodynamics ◽

Spatially Resolved

The determination of the heat release in technical flames is commonly done via bandpass filtered chemiluminescence measurements in the wavelength range of OH* or CH* radicals, which are supposed to be a measure for the heat release rate. However, these indirect heat release measurements are problematic, because the measured intensities are the superposition of the desired radical emissions and contributions from the broadband emissions of CO2*. Furthermore, the chemiluminescence intensities are strongly affected by the local air excess ratio of the flame and the turbulence intensity in the reaction zone. To investigate the influence of these effects on the applicability of chemiluminescence as a measure for heat release rate in turbulent flames with mixture gradients, a reference method is used, which is based on the first law of thermodynamics. It is shown that although the integral heat release can be correlated with the integral chemiluminescence intensities, the heat release distribution is not properly represented by any signal from OH* or CH*. No reliable information about the spatially resolved heat release can be obtained from chemiluminescence measurements in flames with mixture gradients.

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Heat release rate determination of pool fire at different pressure conditions

Fire and Materials ◽

10.1002/fam.2515 ◽

2018 ◽

Vol 42 (6) ◽

pp. 620-626 ◽

Cited By ~ 5

Author(s):

Qiuju Ma ◽

Jiachen Chen ◽

Hui Zhang

Keyword(s):

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Pool Fire

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

10.32920/14639259.v1 ◽

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.

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Determination of the heat release rate of large scale hydrocarbon pool fires in ventilated compartments

Fire Safety Journal ◽

10.1016/j.firesaf.2013.01.014 ◽

2013 ◽

Vol 62 ◽

pp. 192-205 ◽

Cited By ~ 9

Author(s):

H. Pretrel ◽

W. Le Saux ◽

L. Audouin

Keyword(s):

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Large Scale ◽

Pool Fires ◽

Hydrocarbon Pool ◽

Hydrocarbon Pool Fires

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A Comparison of the Behaviour of Spruce Wood and Polyolefins during the Test on the Cone Calorimeter

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.4280 ◽

2013 ◽

Vol 726-731 ◽

pp. 4280-4287 ◽

Cited By ~ 4

Author(s):

Jozef Martinka ◽

Emília Hroncová ◽

Tomáš Chrebet ◽

Karol Balog

Keyword(s):

Heat Flux ◽

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Cone Calorimeter ◽

Lower Sensitivity ◽

Average Heat ◽

Fire Propagation ◽

Spruce Wood

This article deals with comparison of the behaviour of spruce wood and polyolefins (polyethylene PE and polypropylene PP) during the test on the cone calorimeter. Samples were tested on the cone calorimeter at heat flux of 20 and 40 kW/m2. An evaluation of the behaviour of examined materials was based on the determination of the maximum and the average heat release rate, yield of carbon monoxide (CO), and relative comparison of tendency to fire propagation in a flashover phase. The tendency of materials to fire propagation in the flashover phase was evaluated based on the Pearson ́s correlation, the Spearman ́s correlation and the Kendall ́s correlation coefficient of HRR-CO and CO2-CO. Spruce wood showed better properties in comparison with PE and PP in all evaluated parameters (the maximum and the average heat release rate, the yield of CO, and also the resistance to fire propagation in the flashover phase. Additionally, spruce wood showed significantly lower sensitivity of dependence of the maximum and also the average heat release rate on external heat flux.

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