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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Simulation of Turbulent Lifted Flames Using a Partially Premixed Coherent Flame Model

[+] Author and Article Information
Yongzhe Zhang, Rajesh Rawat

J. Eng. Gas Turbines Power 131(3), 031505 (Feb 10, 2009) (10 pages) doi:10.1115/1.3026559 History: Received April 04, 2008; Revised August 25, 2008; Published February 10, 2009

Abstract

Partially premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially premixed turbulent combustion. In this paper we propose modifications to the coherent flame model so that it can be brought to the simulation of partially premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent nonpremixed zone, a laminar flamelet presumed probability density function (PPDF) methodology, which accounts for the nonequilibrium and finite-rate chemistry effects, is adopted. The model is validated against the experimental data on a lifted $H2∕N2$ jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results, the flame stabilization mechanism for lifted flames is investigated.

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Figures

Figure 1

Schematic of the burner

Figure 2

Computed and measured radial profiles of mean temperature in the nonreacting jet. Symbols: experimental measurements. Lines: computation.

Figure 3

Computed and measured axial profiles of mean temperature and mean mass fractions of H2, H2O, N2, O2, and OH at the centerline. Symbols: experimental measurements. Lines: computation.

Figure 4

Computed and measured radial profiles of mean temperature. Symbols: experimental measurements. Lines: computation.

Figure 5

Computed and measured radial profiles of mean mass fraction of H2. Symbols: experimental measurements. Lines: computation.

Figure 6

Computed and measured radial profiles of mean mass fraction of O2. Symbols: experimental measurements. Lines: computation.

Figure 7

Computed and measured radial profiles of mean mass fraction of H2O. Symbols: experimental measurements. Lines: computation.

Figure 8

Computed and measured radial profiles of mean mass fraction of OH. Symbols: experimental measurements. Lines: computation.

Figure 9

Computed and measured radial profiles of mean mass fraction of N2. Symbols: experimental measurements. Lines: computation.

Figure 10

Computed contours of progress variable, flame area density, mixture fraction, and scalar dissipation rate

Figure 11

Computed radial profiles of mean flame area density

Figure 12

Computed radial profiles of mean progress variable rate

Figure 13

Computed radial profiles of mean mixture fraction

Figure 14

Computed radial profiles of mean scalar dissipation rate

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