Effect of CO2 Dilution on the Laminar Burning Velocities of Premixed Methane/Air Flames at Elevated Temperature

Abstract

With increased interest in reducing emissions, the staged combustion concept for gas turbine combustors is gaining in popularity. For this work, the effect of CO2 dilution on laminar burning velocities of premixed methane/air flames was investigated at elevated temperature through both experiments and numerical simulations. Validation of the experimental setup and methodology was completed through experimental testing of methane/air mixtures at 1 bar and 298 K. Following validation, high temperature experiments were conducted in an optically accessible constant volume combustion chamber at 1 bar and 473 K. Laminar burning velocities of premixed methane/air flames with 0%, 5%, 10%, and 15% CO2 dilution were determined using the constant pressure method enabled via schlieren visualization of the spherically propagating flame front. Results show that laminar burning velocities of methane/air mixtures at 1 bar increase by 106–145% with initial temperature increases from 298 K to 473 K. Additions of 5%, 10%, and 15% CO2 dilution at 1 bar and 473 K cause a 30–35%, 51–54%, and 66–68% decrease in the laminar burning velocity, respectively. Numerical results were obtained with CHEMKIN (Kee et al., 1985, “PREMIX: A Fortran Program for Modeling Steady Laminar One-Dimensional Premixed Flames,”) using the GRI-Mech 3.0 (Smith et al., 2019) and the San Diego (“Chemical-Kinetic Mechanisms for Combustion Applications,” San Diego Mechanism Web Page, Mechanical and Aerospace Engineering (Combustion Research), University of California at San Diego, San Diego, CA) mechanisms. It is concluded that the GRI-Mech 3.0 (Smith et al.., 2019) better captures the general overall trend of the experimental laminar flame speeds of methane/air/CO2 mixtures at 1 bar and 473 K. Additionally, the dilution, thermal-diffusion, and chemical effects of CO2 on the laminar burning velocities of methane/air mixtures were investigated numerically by diluting the mixtures with both chemically active and inactive CO2 following the determination of the most important elementary reactions on the burning rate through sensitivity analysis. Finally, it was shown that CO2 dilution suppresses the flame instabilities during combustion, which is attributable to the increase in the burned gas Markstein length (Lb) with the addition of diluent.

Experimental and Numerical Investigation of the CO2 Dilution Effect on Laminar Burning Velocities and Burned Gas Markstein Lengths of High/Low RON Gasolines and Isooctane Flames at Elevated Temperatures

“…The chemical, or kinetic, effect occurs when there is an alteration in reaction kinetics . For instance, CO 2 participates in the reaction CO 2 + H = CO + OH according to a detailed sensitivity analysis . It competes for H radicals with the chain-branching reaction H + O 2 = O + OH and, by doing so, impedes the isooctane/air combustion.…”

“…49 For instance, CO 2 participates in the reaction CO 2 + H = CO + OH according to a detailed sensitivity analysis. 51 It competes for H radicals with the chain-branching reaction H + O 2 = O + OH and, by doing so, impedes the isooctane/air combustion. This last reaction is important as it is the dominant reaction that produces reactive radicals, which in part control the laminar flame speed.…”

An Optimized Methane Reaction Model for Oxyfuel Combustion

“…For the current work, a comprehensive set of experimental data including IDT, LFS, and species profile measurements was collected. For CH 4 , 1418 shock tube IDT data from refs and − , 1278 LFS measurements from refs and − , and 200 species profile measurements from refs , , and in jet-stirred reactor (JSR) were collected. Among the experimental data, 204 IDT and 522 LFS measurements were diluted in CO 2 and hence are relevant to oxyfuel combustion.…”

Achieving Net-Zero CO2 Emissions from Indirect Co-combustion of Biomass and Natural Gas with Carbon Capture using a Novel Amine Blend

“…Laminar burning velocity is defined as the speed of a steady, one-dimensional adiabatic laminar flame (Duva et al, 2020). It is the speed at which a flame will propagate through a homogeneous mixture of unburned reactants under adiabatic conditions.…”