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

# Flashback and Turbulent Flame Speed Measurements in Hydrogen/Methane Flames Stabilized by a Low-Swirl Injector at Elevated Pressures and Temperatures

[+] Author and Article Information
David Beerer

e-mail: djb@ucicl.uci.edu

Vincent McDonell

e-mail: vgm@ucicl.uci.edu
UC Irvine Combustion Laboratory
Irvine, CA 92697-3550

Peter Therkelsen

e-mail: ptherkelsen@lbl.gov

Robert K. Cheng

e-mail: rkcheng@lbl.gov
Lawrence Berkeley National Laboratory
Berkeley, CA 94720

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 2, 2013; final manuscript received September 16, 2013; published online November 5, 2013. Assoc. Editor: Klaus Dobbeling.

The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States government purposes.

J. Eng. Gas Turbines Power 136(3), 031502 (Nov 05, 2013) (9 pages) Paper No: GTP-13-1223; doi: 10.1115/1.4025636 History: Received July 02, 2013; Revised September 16, 2013

## Abstract

This paper reports flashback limits and turbulent flame local displacement speed measurements in flames stabilized by a low swirl injector operated at elevated pressures and inlet temperatures with hydrogen and methane blended fuels. The goal of this study is to understand the physics that relate turbulent flame speed to flashback events at conditions relevant to gas turbine engines. Testing was conducted in an optically accessible single nozzle combustor rig at pressures ranging from 1 to 8 atm, inlet temperatures from 290 to 600 K, and inlet bulk velocities between 20 and 60 m/s for natural gas and a 90%/10% (by volume) hydrogen/methane blend. The propensity of flashback is dependent upon the proximity of the lifted flame to the nozzle that is itself dependent upon pressure, inlet temperature, and bulk velocity. Flashback occurs when the leading edge of the flame in the core of the flow ingresses within the nozzle, even in cases when the flame is attached to the burner rim. In general the adiabatic flame temperature at flashback is proportional to the bulk velocity and inlet temperature and inversely proportional to the pressure. The unburned reactant velocity field approaching the flame was measured using a laser Doppler velocimeter with water seeding. Turbulent displacement flame speeds were found to be linearly proportional to the root mean square of the velocity fluctuations about the mean velocity. For identical inlet conditions, high-hydrogen flames had a turbulent flame local displacement speed roughly twice that of natural gas flames. Pressure, inlet temperature, and flame temperature had surprisingly little effect on the local displacement turbulent flame speed. However, the flow field is affected by changes in inlet conditions and is the link between turbulent flame speed, flame position, and flashback propensity.

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## Figures

Fig. 1

Low-swirl injector, back view (left) and front view (right)

Fig. 2

Low-swirl methane flame with illustrative streamlines superimposed. The diverging lines represent the inner flow, while the ellipses represent the swirling outer flow. Flow direction is top to bottom.

Fig. 3

High-pressure vessel and facility

Fig. 4

Cross-sectional image of pressure vessel and combustor test section

Fig. 5

Nonreacting radial profiles of normalized mean and rms axial velocities for LSI-P1. (Inlet conditions: Po = 1–8 atm, To = 380–470 K, Uo = 25–47 m/s.)

Fig. 6

Nonreacting radial profiles of normalized mean and rms axial velocities for LSI-P2. (Inlet conditions: Po = 4–5 atm, To = 440–450 K, Uo = 35–48 m/s.)

Fig. 7

Images of 90%/10% hydrogen/methane flames from LSI-P1 and LSI-P2 at similar inlet conditions (Po = 3 atm, To = 294 K, Uo = 45 m/s, AFT = 1870 K)

Fig. 8

Sequential images of a flashback event

Fig. 9

Pressure drop and axial velocity measurements during a flashback event

Fig. 10

Flashback results for LSI-P1 for To = 400 K

Fig. 11

Effect of To on flashback limit for LSI-P1

Fig. 12

Correlation for flashback limit of LSI-P1

Fig. 13

Axial profiles of normalized mean, rms axial and rms radial velocities for a high-hydrogen flame with LSI-P2

Fig. 14

ST,LD as a function of u′

Fig. 15

U/Uo and u ′/UO near the nozzle exit for nonreacting and reacting flows for LSI-P2

Fig. 16

Turbulence intensity at leading edge of flame as a function of AFT for flames H-1 through H-10

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