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Research Papers: Gas Turbines: Turbomachinery

# Operability Limits of Tubular Injectors With Vortex Generators for a Hydrogen-Fueled Recuperated 100 kW Class Gas Turbine

[+] Author and Article Information
Stefan Bauer

Lehrstuhl für Thermodynamik,
Technische Universität München,
Garching 85748, Germany
e-mail: bauer@td.mw.tum.de

Balbina Hampel, Thomas Sattelmayer

Lehrstuhl für Thermodynamik,
Technische Universität München,
Garching 85748, Germany

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received December 23, 2016; final manuscript received January 4, 2017; published online March 28, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(8), 082607 (Mar 28, 2017) (8 pages) Paper No: GTP-16-1595; doi: 10.1115/1.4035842 History: Received December 23, 2016; Revised January 04, 2017

## Abstract

Vortex generators are known to be effective in augmenting the mixing of fuel jets with air. The configuration investigated in this study is a tubular air passage with fuel injection from one single orifice placed in the side wall. In the range of typical gas turbine combustor inlet temperatures, the performance vortex generator premixers (VGPs) have already been investigated for natural gas as well as for blends of natural gas and hydrogen. However, for highly reactive fuels, the application of VGPs in recuperated gas turbines is particularly challenging because the high combustor inlet temperature leads to potential risk with regard to premature self-ignition and flame flashback. As the current knowledge does not cover the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is currently being conducted at the Thermodynamics Institute of the Technical University of Munich, Garching, Germany, which is particularly focused on reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. For the study presented in this paper, an atmospheric combustion VGP test rig has been designed, which facilitates investigations in a wide range of operating conditions in order to comply with the situation in recuperated microgas turbines (MGT), namely, global equivalence ratios between 0.2 and 0.7, air preheating temperatures between 288 K and 1100 K, and air bulk flow rates between 6 and 16 g/s. Both the entire mixing zone in the VGP and the primary combustion zone of the test rig are optically accessible. High-speed OH* chemiluminescence imaging is used for the detection of the flashback and blow-off limits of the investigated VGPs. Flashback and blow-off limits of hydrogen in a wide temperature range covering the autoignition regime are presented, addressing the influences of equivalence ratio, air preheating temperature, and momentum ratio between air and hydrogen on the operational limits in terms of bulk flow velocity. It is shown that flashback and blow-off limits are increasingly influenced by autoignition in the ultrahigh temperature regime.

## Figures

Fig. 1

Schematic drawing of the test rig

Fig. 2

Technical drawing of the heated tip, including measuring TTip and the optical accessibility part of the VGP

Fig. 3

Vortices in the VGP—penetration for J < 1 in the lower and penetration for J > 1 in the upper region

Fig. 4

Schematic drawing of the VGP

Fig. 5

Picture of the three injector types: full metal (a), quartz short (b), and quartz long (c)

Fig. 6

Mean OH* chemiluminescence images at the same test conditions with different fuel ratios—injector B, TAir=677 °C, and uMix 100 m/s: (a) Φ=0.555,J = 4.8, (b) Φ=0.4,J = 2.47, (c) Φ=0.25,J = 0.96, and (d) Φ=0.2,J = 0.61

Fig. 7

Lift-off height as a function of air temperature ( → injector A, → injector B, and → injector C)

Fig. 8

Lift-off height as a function of mixture outlet velocity (→ injector A, → injector B, and → injector C)

Fig. 9

Ignition stability as a function of air temperature—bulk flow velocity 100 m/s and injector A ( →Φ=0.555, → Φ=0.4,  →Φ=0.25, and →Φ=0.2)

Fig. 10

Ignition stability as a function of lift-off—bulk flow velocity 70 m/s and injector B (→Φ=0.4, →Φ=0.333, □ →Φ=0.285, →Φ=0.25, →Φ=0.222, and →Φ=0.2)

Fig. 11

Lift-off as a function of air mixture temperature—fuel ratio Φ=0.25 and injector A ( → uMix=140 m/s,  → uMix=100 m/s, and + → uMix=70 m/s

Fig. 12

Lift-off as a function of air mixture temperature—bulk flow velocity 70 m/s, injector B, and standard deviation ( → Φ=0.4, → Φ=0.333, □ → Φ=0.285, → Φ=0.25, → Φ=0.222, and → Φ=0.2)

Fig. 13

Lift-off as a function of air mixture temperature (, ) and lift-off as a function of tip temperature (, )—bulk flow velocity 100 m/s, heat plate, and Φ=0.4 ((, ) → TTip<420 °C and (, ) → TTip>500 °C)

Fig. 14

Lift-off as a function of air mixture temperature (, ) and lift-off as a function of tip temperature (, )—bulk flow velocity 100 m/s, heat plate, and Φ=0.25 ((, ) → TTip<410 °C and (, ) → TTip>500 °C)

Fig. 15

Lift-off as a function of air mixture temperature () and lift-off as a function of hydrogen volume fraction ()—bulk flow velocity 100 m/s, TAir=740°C, Φ=0.37, and natural gas ( → TMix,  → ψH2)

Fig. 16

Lift-off as a function of air mixture temperature—bulk flow velocity 100 m/s (, , ) and 70 m/s (), injector A, and secondary air ( → α=0%,  → α=4%, → α=7.7%, and → α=11%)

Fig. 17

Ignition stability as a function of air mixture temperature—bulk flow velocity 100 m/s (, , ) and 70 m/s (), injector A, and secondary air ( → α=0%,  → α=4%, → α=7.7%, and → α=11%)

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