Impact of Hydrogen Addition on the Thermoacoustic Instability and Precessing Vortex Core Dynamics in a CH4/H2/Air Technically Premixed Combustor

Datta, A and Gupta, S and Chterev, I and Boxx, I and Hemchandra, S (2022) Impact of Hydrogen Addition on the Thermoacoustic Instability and Precessing Vortex Core Dynamics in a CH4/H2/Air Technically Premixed Combustor. In: Journal of Engineering for Gas Turbines and Power, 144 (2).

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Abstract

We study the impact of H2 enrichment on the unsteady flow dynamics and thermoacoustic instability in the prediction and control of instabilities in industrial turbines (PRECCINSTA) swirl combustor. The experiments were performed at atmospheric conditions with H2=CH4 fuel mixtures at a global equivalence ratio of 0.65 and a constant thermal power of 20 kW. We analyze data with three fuel compositions: 0; 20, and 50 H2 in two operating modes, premixed (PM) and technically premixed (TPM). A new multiresolution modal decomposition method, using a combination of wavelet transforms and proper orthogonal decomposition (WPOD) is performed on time resolved flow velocity and OH planar laser induced fluorescence (OH planar laser induced fluorescence (OH-PLIF)) measurements. Thermoacoustic oscillations are observed in the TPM operating mode alone, indicating that the primary heat release driving mechanism is due to fuel-air ratio oscillations. WPOD results for the 0 H2 TPM case reveal intermittent helical precessing vortex core (PVC) oscillations along with axisymmetric hydrodynamic flow oscillations due to the thermoacoustic oscillations. These oscillations cause local flame extinction near the nozzle centerbody resulting in liftoff. A PVC then develops in the flow and enables intermittent flame reattachment. In the 0 H2 premixed case, the flame remains lifted off the centerbody despite the presence of PVC oscillations. H2 enrichment results in the suppression of flame liftoff and the PVC in both operating modes. We show from flow strain rate statistics and extinction strain rate calculations that the increase of the latter with H2 addition, allows the flame to stabilize in the region near the centerbody where the pure CH4 cases show lift off.

Item Type:	Journal Article
Publication:	Journal of Engineering for Gas Turbines and Power
Publisher:	American Society of Mechanical Engineers (ASME)
Additional Information:	The copyright for this article belongs to the American Society of Mechanical Engineers (ASME).
Keywords:	Combustion; Flow velocity; Fluorescence; Fuels; Hydrogen; Laser optics; Laser produced plasmas; Plasma oscillations; Principal component analysis; Vortex flow, CH 4; Core dynamics; Flow dynamics; Hydrogen addition; Operating modes; Precessing vortex core; Premixed; Thermoacoustic instability; Thermoacoustic oscillations; Wavelets transform, Combustors
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	27 Jun 2022 05:33
Last Modified:	27 Jun 2022 05:33
URI:	https://eprints.iisc.ac.in/id/eprint/73875

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