Comparison of Hydrogen Micromix Flame Transfer Functions Determined Using RANS and LES

McClure, Jonathan; Abbott, David; Agarwal, Parash; Sun, Xiaoxiao; Babazzi, Giulia; Sethi, Vishal; Gauthier, Pierre

doi:10.1115/gt2019-90538

Cited by 5 publications

(6 citation statements)

References 28 publications

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“…From instantaneous OH PLIF images, the authors identified flame annihilation [99] as the main instability driving mechanism for the compact hydrogen flames. McClure et al [100] numerically investigated the forced response of hydrogen micro-diffusion flames using a single injector element in a jet-in-crossflow arrangement. FTF results, computed using steady-state Reynolds-Averaged Navier-Stokes simulation , showed that the gain of the FTF did not decrease substantially until very high frequencies (>2000 Hz).…”

Section: Micromix Combustionmentioning

confidence: 99%

Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

et al. 2021

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Hydrogen is receiving increasing attention as a versatile energy vector to help accelerate the transition to a decarbonised energy future. Gas turbines will continue to play a critical role in providing grid stability and resilience in future low-carbon power systems; however, it is recognised that this role is contingent upon achieving increased thermal efficiencies and the ability to operate on carbon-neutral fuels such as hydrogen. An important consideration in the development of gas turbine combustors capable of operating with pure hydrogen or hydrogen-enriched natural gas are the significant changes in thermoacoustic instability characteristics associated with burning these fuels. This article provides a review of the effects of burning hydrogen on combustion dynamics with focus on swirl-stabilised lean-premixed combustors. Experimental and numerical evidence suggests hydrogen can have either a stabilising or destabilising impact on the dynamic state of a combustor through its influence particularly on flame structure and flame position. Other operational considerations such as the effect of elevated pressure and piloting on combustion dynamics as well as recent developments in micromix burner technology for 100% hydrogen combustion have also been discussed. The insights provided in this review will aid the development of instability mitigation strategies for high hydrogen combustion.

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Section: Micromix Combustionmentioning

confidence: 99%

Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

et al. 2021

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“…As indicated in Figure 4 the FTF may be determined by experiment, LES modelling or the use of analytical models. FTFs for a micromix flame determined by both LES modelling and the use of analytical models and RANS CFD have been reported by McClure [17] and Cranfield University is currently developing test rigs to investigate micromix combustion characteristics over a wide range of operating conditions, including the measurement of the FTFs, but this data is not available for this study.…”

Section: Flame Transfer Functionmentioning

confidence: 99%

“…The estimation of the time delay from steady state information provided by RANS CFD, effectively limits the possible delays to convective times within the flame. The most common method of determining the time delay is to assume that the relevant time delay is the time from fuel injection to the flame front [17], [24], [25], [26] and to track particles from fuel injection to the flame front. This requires an assumption as to what constitutes the flame front.…”

Section: Ftf For Micromix Combustionmentioning

confidence: 99%

Thermoacoustic Behaviour of a Hydrogen Micromix Aviation Gas Turbine Combustor Under Typical Flight Conditions

Abbot

Giannotta

Sun

et al. 2021

Volume 6: Ceramics and Ceramic Composites; Coal, Biomass, Hydrogen, and Alternative Fuels; Microturbines, Turbochargers, and Sm

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Hydrogen micromix is a candidate combustion technology for hydrogen aviation gas turbines. The introduction and development of new combustion technologies always carries the risk of suffering from damaging high amplitude thermoacoustic pressure oscillations. This was a particular problem with the introduction of lean premixed combustion systems to land based power generation gas turbines. There is limited published information on the thermoacoustic behaviour of such hydrogen micromix combustors. Diffusion flames are less prone to flashback and autoignition problems than premixed flames and conventional diffusion flames are less prone to combustion dynamics issues. However, with the high laminar flame speed of hydrogen, lean fuel air ratio (FAR) and very compact flames, the risk of combustion dynamics for micromix flames should not be neglected and a comparison of the likely thermoacoustic behaviour of micromix combustors and kerosene fueled aviation combustors would inform the early stage design of engine realistic micromix combustors. This study develops a micromix combustor concept suitable for a modern three spool, high bypass ratio engine and derives the acoustic Flame Transfer Function (FTF) at typical engine operating conditions for top of climb, take-off, cruise, and end of runway. The FTF is derived using CFD and FTF models based on a characteristic flame delay. The relative thermoacoustic behaviour for the four conditions is assessed using a low order acoustic network code. The comparisons suggest that the risk of thermoacoustic instabilities associated with longitudinal waves at low frequencies (below 1kHz) is small, but that higher frequency longitudinal modes could be excited. The sensitivity of the combustor thermoacoustic behaviour to key combustor dimensions and characteristic time delay is also investigated and suggests that higher frequency longitudinal modes can be significantly influenced by combustion system design. The characteristic time delay and thus FTF for a Lean Premixed Prevapourised (LPP) kerosene combustor is derived from information in the literature and the thermoacoustic behaviour of the micromix combustor relative to that of this kerosene combustor is determined using the same low order modelling approach. The comparison suggests that the micromix combustor is much less likely to produce thermoacoustic instabilities at low frequencies (below 1kHz), than the LPP combustor even though the risk in the LPP combustor is small. It is encouraging that this simple approach used in a preliminary design suggests that the micromix combustor has lower risk at low frequency than a kerosene combustor and that the risk of higher frequency longitudinal modes can be reduced by appropriate combustion system design. However, more detailed design, more rigorous thermoacoustic analysis and experimental validation are needed to confirm this.

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“…This project explores feasibility of liquid hydrogen as an aircraft fuel and includes the fuel system as well. The micromix development focuses on Reynolds-averaged Navier-Stokes (RANS) and large eddie simulations (LES) adapted for micromix hydrogen combustion and their limitations [15][16][17][18][19], the design of the micromix geometry [20,21], and thermoacoustic modeling [22][23][24].…”

Section: Stationary Gas Turbine Combustionmentioning

confidence: 99%

“…The aim of this work is to investigate a technology transfer of hydrogen combustion in aero applications to stationary gas turbines. The research presented in this paper builds on the ongoing work and generated knowledge at Cranfield University [15][16][17][18][19][20][21][22][23][24] to develop a micromix hydrogen combustor for aero applications. In this paper, RANS CFD is used to model design adaptations and to assess their impact on flame structure, outlet conditions, and nitrogen oxide (NOx) emissions.…”

Section: Introductionmentioning

confidence: 99%

Scaling of an Aviation Hydrogen Micromix Injector Design for Industrial GT Combustion Applications

Berger

2021

Aerotec. Missili Spaz.

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Decarbonising the energy grid through renewable energy requires a grid firming technology to harmonize supply and demand. Hydrogen-fired gas turbine power plants offer a closed loop by burning green hydrogen produced with excess power from renewable energy. Conventional dry low NOx (DLN) combustors have been optimized for strict emission limits. A higher flame temperature of hydrogen drives higher NOx emissions and faster flame speed alters the combustion behavior significantly. Micromix combustion offers potential for low NOx emissions and optimized conditions for hydrogen combustion. Many small channels, so-called airgates, accelerate the airflow followed by a jet-in-crossflow injection of hydrogen. This leads to short-diffusion flames following the principle of maximized mixing intensity and minimized mixing scales. This paper shows the challenges and the potential of an economical micromix application for an aero-derivative industrial gas turbine with a high-pressure ratio. A technology transfer based on the micromix combustion research in the ENABLEH2 project is carried out. The driving parameter for ground use adaption is an increased fuel orifice diameter from 0.3 mm to 1.0 mm to reduce cost and complexity. Increasing the fuel supply mass flow leads to larger flames and higher emissions. The impact was studied through RANS simulation and trends for key design parameters were shown. Increased velocity in the airgates leads to a higher pressure drop and reduced emissions through faster mixing. Altering the penetration depth shows potential for emission reduction without compromising on pressure loss. Two improved designs are found, and their performance is discussed.

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Comparison of Hydrogen Micromix Flame Transfer Functions Determined Using RANS and LES

Cited by 5 publications

References 28 publications

Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

Thermoacoustic Behaviour of a Hydrogen Micromix Aviation Gas Turbine Combustor Under Typical Flight Conditions

Scaling of an Aviation Hydrogen Micromix Injector Design for Industrial GT Combustion Applications

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