Mean Reaction Rate Research Articles

Simulation of Spherically Expanding Turbulent Premixed Flames

Statistically spherical expanding turbulent premixed flames are computed using an unsteady Reynolds-averaged Navier–Stokes (URANS) approach. Mean reaction rate is closed using strained and unstrained flamelet models and an algebraic model. The flamelets are parametrized using the scalar dissipation rate in the strained flamelet model. It is shown that this model is able to capture the measured growth rate of methane–air turbulent flame ball, which is free of thermo–diffusive instability. The spherical flames are observed to accelerate continuously. The flame brush thickness grows in time and the role of turbulent diffusion on this growth seems secondary compared to the convection due to the fluid velocity induced by the chemical reaction. The spherical flames have larger turbulent flame speed, the leading-edge displacement speed st, compared to the planar flames for a given turbulence and thermochemical condition. The computational results suggest with 0.57 ≤ n ≤ 0.58, where Re t is the turbulence Reynolds number and is the unstrained planar laminar flame speed, for both spherical and planar flames.

The Effect of Particle Size and Heating Rate on Pyrolysis of Waste Capsicum Stalks Biomass

With pyrolysis as an attractive way to reduce CO2 and degrade residues, the effect of particle size and heating rate on pyrolysis of capsicum stalks has been investigated by thermogravimetry-differential gravimetric analysis and kinetic studies. Results show that pyrolysis reaction rate increases with increasing particle size. It is supposed that the contents of hemicelluloses, cellulose, lignin, and ash of various particle sizes have significant influence on the pyrolysis of biomass. Meanwhile, high heating rate does not mean high reaction rate, there is a complex competition effect between thermal hysteresis effects and the driving force originated from different heating rates.

Simulations of transient n-heptane and n-dodecane spray flames under engine-relevant conditions using a transported PDF method

Time-dependent Reynolds-averaged CFD is performed for transient turbulent spray flames in a high-pressure, constant-volume chamber for two single-component fuels using skeletal chemical mechanisms. The simulations span a range of initial pressures, temperatures and compositions that correspond to conventional and advanced (e.g., low-temperature) compression-ignition engine combustion. The objectives are to establish the extent to which turbulent fluctuations in composition and temperature influence ignition delays and lift-off lengths and turbulent flame structure under engine-relevant conditions, and to provide insight into turbulence-chemistry interactions. This is done by comparing results from a model that accounts for turbulent fluctuations using a transported composition probability density function (PDF) method with those from a model that ignores the influence of turbulent fluctuations on local mean reaction rates (a locally well-stirred reactor – WSR – model). For robust diesel combustion conditions, the WSR and PDF computed ignition delays and lift-off lengths are close to each other, and both are in good agreement with experiment. For lower initial temperatures, ignition delays and lift-off lengths from the two models are significantly different, and the results from the PDF model are in better agreement with experiment. The differences are especially striking for n-dodecane. There the PDF-model computed ignition delays and lift-off lengths are within 10% of measured values for initial temperatures of 900K and higher (for 22.8kg/m3 density, 15% oxygen), while the WSR model predicts an ignition delay that is three times the measured value at 900K. At an initial temperature of 800K, the WSR model fails to ignite, whereas the PDF model computed ignition delay and lift-off length are within 30% of the measured values. In all cases, the WSR and PDF models produce significantly different turbulent flame structures, and the differences increase with decreasing initial temperature and oxygen level. The WSR model produces a thin laminar-like flame, while the PDF model gives a broadened turbulent flame brush that is qualitatively more consistent with what is expected for these highly turbulent flames and what is observed experimentally. Thus, while it may be possible to reproduce some global ignition characteristics using a WSR model (depending on the choice of chemical mechanism), turbulent fluctuations play an increasingly important role at lower initial temperatures and oxygen levels.

Experimental Study on a Reaction Rate in a Reactive Liquid Jet

A reaction rate in a planar liquid jet with a second-order chemical reaction A+B→R is experimentally investigated. The jet flow contains the reactant A and the ambient flow contains the reactant B. The concentrations of reactive species are simultaneously measured by using the optical fiber probe based on the light absorption spectrometric method. The measurement result of mean reaction rate shows that the chemical reaction mainly occurs near the jet centerline in the upstream region, and the mean reaction rate is small in the downstream region. In the upstream region, lateral profiles of concentration correlation of reactants A and B have two local minimum values located away from the jet centerline, whereas the local minimum value of concentration correlation in the downstream region is located on the jet centerline. Comparison of concentration correlation of species A and B between the reactive and non-reactive cases shows that the chemical reaction makes the concentration correlation large near the edge of jet in the upstream region, whereas the opposite effect of chemical reaction on the concentration correlation can be seen in the other region. The concentration correlation of reactants A and B are estimated by using the Toor's hypothesis or the 3E model. The results show that the concentration correlation of reactants A and B estimated by using the Toor's hypothesis is smaller in magnitude than the experimental values, and the 3E model also fails to accurately estimate the concentration correlation.

Conditional Statistics in a Liquid Jet with a Chemical Reaction

Instantaneous velocity and reactive concentrations are simultaneously measured in a planar liquid jet with a secondorder chemical reaction (A+B→R) by combining an I-type hot film probe with an optical fiber probe based on the light absorption spectrometry. Conditional statistics conditioned on the mixture fraction ξ are investigated experimentally. The results show that the reactive concentrations strongly depend on ξ . It is also shown that the conditional mean concentration is close to the concentration at the frozen limit in the upstream region of the jet, and in the downstream direction, the conditional mean concentration becomes close to the concentration at the equilibrium limit because of the reaction progress. The rms value of reactive concentration fluctuation is small compared with the conditional mean concentration. In the conditional moment closure methods, the conditional mean reaction rate is often approximated by using the conditional mean concentration of reactant species. The results show that the conditional mean reaction rate is well approximated by using the product of conditional mean concentrations of reactant species A and B. It is found that the conditional statistics measured in the downstream region is little dependent on the lateral position of the jet flow.

1052 CONDITIONAL STATISTICS OF REACTIVE CONCENTRATIONS IN A PLANAR LIQUID JET

Conditional statistics, conditioned on mixture fraction, are experimentally investigated in a planar liquid jet with a second-order chemical reaction A + B → R. Here, reactants A and B are separately premixed into the jet and the ambient flows, respectively. In this study, instantaneous concentrations of reactive species are simultaneously measured by an optical fiber probe based on the light absorption spectrometry to investigate the conditional statistics, conditioned on mixture fraction. The results show that the conditional mean concentration of reactive species and the conditional mean reaction rate are independent of the lateral position of the jet flow in the downstream region, whereas they change with the lateral position in the upstream region near the jet centerline.

Scalar Dissipation Rate in a Planar Liquid Jet with a Chemical Reaction (Experimental Study on the Evaluation of the Conditional Moment Closure Equation)

Conditional scalar dissipation rate <N | ξ = η> conditioned on a mixture fraction ξ and mean scalar dissipation rate <N> in a planar liquid jet are experimentally investigated. Streamwise velocity and reactive concentrations are simultaneously measured in the planar liquid jet with a second-order chemical reaction A+B→R. <N | η> on the jet centerline is obtained from a conditional moment closure (CMC) equation and measured conditional mean values. To calculate <N | η>, we derive the equations which represent conditional mean concentrations by assuming that the ratio of the conditional mean concentration of product R and the conditional mean reaction rate does not depend on the mixture fraction. The conditional dissipation rate is obtained from the budget of CMC equation. The results show that <N | η> becomes small in the downstream direction. It is also shown that the profiles of <N | η> change in the downstream direction; in the downstream region, <N | η> has a local minimum value at η ≈ ξS, where ξS is the stoichiometric ratio in mixture. <N> can be obtained from <N | η> and the probability density functions of mixture fraction. It is observed that <N> on the jet centerline decays in the downstream (x) direction as x-2.9, which is close to the -3 power expected from scaling arguments.

Dynamics of mixing and bimolecular reaction kinetics in aquifers

Descriptions of chemical transformation kinetics and hydrologic transport need to be coupled to understand the composition of flowing waters. The coupling of a bimolecular transformation reaction (reactant 1 + reactant 2 → product; rate \( r = \kappa c_{1} c_{2} \)) with spatially heterogeneous subsurface flows is addressed here. The flow microstructure—that controls the spreading rate of solutes and the mean reactant concentrations (C 1, C 2)—creates concentration microstructure whose intensity is characterized by the variances \( \sigma_{{c_{1} }}^{2} \), \( \sigma_{{c_{2} }}^{2} \), and the cross-covariance \( \overline{{c_{1} c_{2} }} \). In addition to the macroscopic overlap of the reactants, that is quantified by the product of the mean concentrations that are routinely modeled using effective dispersion coefficients \( D_{ij} \), the concentration microstructure plays an important role in determining reaction macro-kinetics as the mean reaction rate is \( \overline{r} = \kappa (C_{1} C_{2} + \overline{{c_{1} c_{2} }} ) \). For initially non-overlapping reactants \( \overline{{c_{1} c_{2} }} + C_{1} C_{2} = 0 \) and \( \overline{r} = 0 \) under pure advection. It is shown that due to the action of local dispersion, at large time, the \( \overline{{c_{1} c_{2} }} \) budget is characterized by a balance between its rate of production and dissipation, which results in \( \overline{{c_{1} c_{2} }} \approx 2\tau D_{ij} ({{\partial C_{1} } \mathord{\left/ {\vphantom {{\partial C_{1} } {\partial x_{i} )({{\partial C_{2} } \mathord{\left/ {\vphantom {{\partial C_{2} } {\partial x_{j} )}}} \right. \kern-0pt} {\partial x_{j} )}}}}} \right. \kern-0pt} {\partial x_{i} )({{\partial C_{2} } \mathord{\left/ {\vphantom {{\partial C_{2} } {\partial x_{j} )}}} \right. \kern-0pt} {\partial x_{j} )}}}} \), where τ is the dissipation time-scale characteristic to the destruction of concentration fluctuation by local dispersion. This results in \( \overline{r} = \kappa_{\text{eff}} C_{1} C_{2} \), where \( \kappa_{\text{eff}} \approx \kappa [1 + 2\tau D_{ij} ({{\partial { \ln }C_{1} } \mathord{\left/ {\vphantom {{\partial { \ln }C_{1} } {\partial x_{i} )({{\partial { \ln }C_{2} } \mathord{\left/ {\vphantom {{\partial { \ln }C_{2} } {\partial x_{j} )}}} \right. \kern-0pt} {\partial x_{j} )}}}}} \right. \kern-0pt} {\partial x_{i} )({{\partial { \ln }C_{2} } \mathord{\left/ {\vphantom {{\partial { \ln }C_{2} } {\partial x_{j} )}}} \right. \kern-0pt} {\partial x_{j} )}}}}] \), which accounts for the influence of concentration microstructure and small-scale mixing on the macroscopic bimolecular kinetics. The effective rate parameter κeff is greater than the intrinsic rate constant κ measured under well-mixed conditions if the macroscopic concentration gradients have the same sign (initially overlapping reactants). For the initially non-overlapping reactants which result in macroscopic gradients having opposite signs, κ eff < κ. The macroscopic reactant concentration gradients, effective dispersion coefficients, and the dissipation time-scale control the reaction macro-kinetics, in addition to the intrinsic rate constant κ and the mean reactant concentrations. The formulation for reaction macro-kinetics developed here helps explain previously reported disparities between laboratory and field-scale transformation rates and also provides a way to represent the influence of reactant concentration microstructure in large-scale descriptions of reactive transport.

Analysis of Algebraic Closures of the Mean Scalar Dissipation Rate of the Progress Variable Applied to Stagnating Turbulent Flames

In the turbulent premixed reactive flows considered in this study, i.e. large Damkohler and Reynolds numbers, the flamelet regime of turbulent combustion applies and the scalar dissipation rate and mean reaction rate are inter related. In this situation various algebraic models for the mean chemical rate that are obtained from an equilibrium of the dominant terms of the transport equation for the scalar dissipation rate, are evaluated through their application to flames stabilized in a turbulent stagnating flow. An asymptotic analysis is first performed and results obtained through the resulting one-dimensional calculation are compared with the experimental data of Li et al. (Proc Combust Inst 25:1207–1214, 1994). Eventually, three-dimensional CFD calculations including suited algebraic closures to represent the turbulent transport terms are carried out. Results are satisfactorily compared to the experimental data of Cho et al. (Proc Combust Inst 22:739–745, 1988). As a first outcome, the analysis confirms the interest and the relevance of the corresponding algebraic closures to deal with turbulent premixed combustion in such conditions. In the search of a satisfactory representation of such premixed impinging flames, the computational results also clearly emphasize the strong intertwinment that exits between the mean reaction rate, i.e. scalar dissipation rate or micro-mixing taking place at the smallest scale of the reactive flowfield, and the Reynolds fluxes modelling, i.e. turbulent macro-mixing.

A Presumed Joint pdf Model for Turbulent Combustion with Varying Equivalence Ratio

Modeling of the joint probability density function of the mixture fraction and progress variable with a given covariance value is studied. This modeling is validated using experimental and direct numerical simulation (DNS) data. A very good agreement with experimental data of turbulent stratified flames and DNS data of a lifted hydrogen jet flame is obtained. The effect of using this joint pdf modeling to calculate the mean reaction rate with a flamelet closure in Reynolds averaged Navier–Stokes (RANS) calculation of stratified flames is studied. The covariance effect is observed to be large within the flame brush. The results obtained from RANS calculations using this modeling for stratified jet- and rod-stabilized V-flames are discussed and compared to the measurements as a posteriori validation for the joint probability density function model with the flamelet closure. The agreement between the computed and measured values of flame and turbulence quantities is found to be good.

Pore network modelling to determine the transport properties in presence of a reactive fluid: From pore to reservoir scale

The study of CO2 sequestration evolution during a reservoir storage project depends on the accurate determination of three macroscopic parameters governing the solute displacement, namely the solute velocity, the dispersion and the mean reaction rate. These parameters are computed for a surface reaction by a pore network modelling technique. A pore network, extracted from micro tomography images is used in order to calculate the macroscopic transport parameters and porosity–permeability evolution during reactive transport as functions of the dimensionless numbers characterizing the reaction and flow rate regimes. Finally, the influence of these macroscopic parameters on CO2 plume evolution is studied for a synthetic reservoir field.

Conditional Moment Closure for Turbulent Premixed Flames

The conditional moment closure (CMC) method has been successfully applied to various non-premixed combustion systems in the past, but its application to premixed flames is not fully tested and validated. The main difficulty is associated with the modeling of conditional scalar dissipation rate of the conditioning scalar, the progress variable. A simple algebraic model for the conditional dissipation rate is validated using DNS results of a V-flame. This model along with the standard k–ϵ turbulence modeling is used in computations of stoichiometric pilot stabilized Bunsen flames using the RANS-CMC method. A first-order closure is used for the conditional mean reaction rate. The computed non reacting and reacting scalars are in reasonable agreement with the experimental measurements and are consistent with earlier computations using flamelets and transported PDF methods. Sensitivity to chemical kinetic mechanism is also assessed. The results suggest that the CMC may be applied across the regimes of premixed combustion.

DNS of EGR-type turbulent flame in MILD condition

Three-dimensional direct numerical simulation (DNS) of exhaust gas recirculation (EGR)-type turbulent combustion operated in moderate and intense low-oxygen dilution (MILD) condition has been carried out to study the flame structure and flame interaction. In order to achieve adequate EGR-type initial/inlet mixture fields, partially premixed mixture fields which are correlated with the turbulence are carefully preprocessed. The chemical kinetics is modelled using a skeletal mechanism for methane–air combustion. The results suggest that the flame fronts have thin flame structure and the direct link between the mean reaction rate and scalar dissipation rate remains valid in the EGR-type combustion with MILD condition. However, the commonly used canonical flamelet is not fully representative for MILD combustion. During the flame–flame interactions, the heat release rate increases higher than the maximum laminar flame value, while the gradient of progress variable becomes smaller than laminar value. It is also proposed that the reaction rate and the scalar gradient can be used as a marker for the flame interaction.

Spatial correlation of heat release rate and sound emission from turbulent premixed flames

The two-point spatial correlation of the rate of change of fluctuating heat release rate is central to the sound emission from open turbulent flames, and a few attempts have been made to address this correlation in recent studies. In this paper, the two-point correlation and its role in combustion noise are studied by analysing direct numerical simulation (DNS) data of statistically multi-dimensional turbulent premixed flames. The results suggest that this correlation function depends on the separation distance and direction but, not on the positions inside the flame brush. This correlation can be modelled using a combination of Hermite–Gaussian functions of zero and second order, i.e. functions of the form (1-Ax2)e-Bx2 for constants A and B, to include its possible negative values. The integral correlation volume obtained using this model is about 0.2δL3 with the length scale obtained from its cube root being about 0.6δL, where δL is the laminar flame thermal thickness. Both of the values are slightly larger than the values reported in an earlier study because of the anisotropy observed for the correlation. This model together with the turbulence-dependent parameter K, the ratio of the root-mean-square (RMS) value of the rate of change of reaction rate to the mean reaction rate, derived from the DNS data is applied to predict the far-field sound emitted from open flames. The calculated noise levels agree well with recently reported measurements and show a sensitivity to K values.

A numerical study of air pollutant dispersion with bimolecular chemical reactions in an urban street canyon using large-eddy simulation

A large-eddy simulation is performed on a turbulent dispersion of chemically reactive air pollutants in a two-dimensional urban street canyon with an aspect ratio of 1.0. Nitrogen monoxide emitted from a line-source set on the bottom of the street canyon disperses and reacts with Ozone included in a free stream. The reactions have significant influences on the concentrations of pollutants in the canyon space, and they increase the concentrations of the reaction products relative to of the concentrations of the reactants. The transport of air pollutants through a free shear layer above the canyon is closely related to the structure of the turbulence. Gases in the canyon are mainly exhausted when low-speed regions appear above the canyon. In contrast, pollutants in the free stream flow into the canyon with high-speed fluid bodies. Consequently, the correlation between the time fluctuations of the reactants' concentrations strongly affects the reaction rates in the region near the free shear layer. In this calculation, the correlation term reaches to a value of 20% of the mean reaction rate at a maximum there.

Intensification of 1‐phenylethanol production by periodical membrane extraction of the product from fermentation broth

AbstractBACKGROUND: Enantioselective bioreduction of acetophenone to S‐(−)‐1‐phenylethanol by Saccharomyces cerevisiae under non‐growth conditions is inhibited by the product created. This study investigated the possibility of intensification and mathematical simulation of 1‐phenylethanol production using periodic product removal carried out by membrane extraction in a hollow fiber membrane module.RESULTS: The highest reaction rate was observed at the beginning of the biotransformation. With increased product concentration in the reaction medium, the reaction rate gradually decreased by about 50% after 20 h of biotransformation. The low concentration of product maintained in the reaction medium using membrane extraction had positive influence on the 1‐phenylethanol production with a high yield (96%) and mean reaction rate of 0.226 mg h−1g−1, 35% higher than biotransformation without product removal. The equilibrium change and membrane fouling caused by biomass were not significant. It was possible to mathematically simulate the whole course of the extractive biotransformation with good agreement with experimental data.CONCLUSION: Bioreductive production of 1‐phenylethanol is more effective when using periodic membrane extraction of the product from the fermentation broth, which gives higher reaction rate, higher yield and simpler downstream process than biotransformation without product removal. Copyright © 2012 Society of Chemical Industry

Kinetic Monte Carlo Annealing Simulation of Cascade Damage in α-Fe

Molecular dynamics is a useful tool for simulating cascade damage in metals and alloys, but the time scale accessible to molecular dynamics is only about 10 -10 s. Kinetic Monte Carlo can be used to simulate annealing of cascade damage to permit analysis of the longer time evolution of cascade damage. We conducted a series of such annealing simulations in α-Fe. The number of surviving displacements before annealing is ~0.3 of the Norgett-Robinson-Torrens (NRT) value in the case of primary knock-on atoms with energy more than ~10 keV, and it decreased by ~30% during the annealing at 300 K because of recombination of vacancies and self-interstitial atoms. The recombination ratio increased as the annealing temperature increased. These results can be meaningfully applied in models such as mean field reaction rate theory used to simulate long-term radiation damage accumulation. We also demonstrated that 1D motion of small SIA clusters can substantially influence the long-term accumulation of cascade damage.

A Physics and Tabulated Chemistry Based Compression Ignition Combustion Model: from Chemistry Limited to Mixing Limited Combustion Modes

This paper presents a new 0D phenomenological approach to predict the combustion process in multi injection Diesel engines operated under a large range of running conditions. The aim of this work is to develop a physical approach in order to improve the prediction of in-cylinder pressure and heat release. Main contributions of this study are the modeling of the premixed part of the Diesel combustion with a further extension of the model for multi-injection strategies. In the present model, the rate of heat release due to the combustion for the premixed phase is related to the mean reaction rate of fuel which is evaluated by an approach based on tabulated local reaction rate of fuel and on the determination of the Probability Density Function (PDF) of the mixture fraction (Z), in order to take into consideration the local variations of the fuel-air ratio. The shape of the PDF is presumed as a standardized <i>β<i/>-function. Mixture fraction fluctuations are described by using a transport equation for the variance of Z. The standard mixture fraction concept established in the case of diffusion flames is here adapted to premixed combustion to describe inhomogeneity of the fuel-air ratio in the control volume. The detailed chemistry is described using a tabulated database for reaction rates and cool flame ignition delay as a function of the progress variable c. The mixing-controlled combustion model is based on the calculation of a characteristic mixing frequency which is a function of the turbulence density, and on the evolution of the available fuel vapor mass in the control volume. The developed combustion model is one sub-model of a thermodynamic model based on the mathematical formulation of the conventional two-zone approach. In addition, an extended sub-model for multi injection is developed to take into account interactions between each spray by describing their impact on the mixture formation. Numerical results from simulations are compared with experimental measurements carried out on a 2 liter Renault Diesel engine and good agreements are found.

A lymphoblast model for IDH2 gain-of-function activity in d-2-hydroxyglutaric aciduria type II: Novel avenues for biochemical and therapeutic studies

The recent discovery of heterozygous isocitrate dehydrogenase 2 (IDH2) mutations of residue Arg 140 to Gln 140 or Gly 140 (IDH2 wt/R140Q, IDH2 wt/R140G) in d-2-hydroxyglutaric aciduria ( D-2-HGA) has defined the primary genetic lesion in 50% of D-2-HGA patients, denoted type II. Overexpression studies with IDH1 R132H and IDH2 R172K mutations demonstrated that the enzymes acquired a new function, converting 2-ketoglutarate (2-KG) to d-2-hydroxyglutarate ( D-2-HG), in lieu of the normal IDH reaction which reversibly converts isocitrate to 2-KG. To confirm the IDH2 wt/R140Q gain-of-function in D-2-HGA type II, and to evaluate potential therapeutic strategies, we developed a specific and sensitive IDH2 wt/R140Q enzyme assay in lymphoblasts. This assay determines gain-of-function activity which converts 2-KG to D-2-HG in homogenates of D-2-HGA type II lymphoblasts, and uses stable-isotope-labeled 2-keto[3,3,4,4- 2H 4]glutarate. The specificity and sensitivity of the assay are enhanced with chiral separation and detection of stable-isotope-labeled D-2-HG by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Eleven potential inhibitors of IDH2 wt/R140Q enzyme activity were evaluated with this procedure. The mean reaction rate in D-2-HGA type II lymphoblasts was 8-fold higher than that of controls and D-2-HGA type I cells (14.4 nmol h −1 mg protein −1 vs. 1.9), with a corresponding 140-fold increase in intracellular D-2-HG level. Optimal inhibition of IDH2 wt/R140Q activity was obtained with oxaloacetate, which competitively inhibited IDH2 wt/R140Q activity. Lymphoblast IDH2 wt/R140Q showed long-term cell culture stability without loss of the heterozygous IDH2 wt/R140Q mutation, underscoring the utility of the lymphoblast model for future biochemical and therapeutic studies.

Heat release rate correlation and combustion noise in 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.