GENERATION OF ENTROPY WAVES BY FULLY PREMIXED FLAMES IN A NON-ADIABATIC COMBUSTOR WITH HYDROGEN ENRICHMENT

Alexander J. Eder, Bayu Dharmaputra, Marcel Désor, Camilo F. Silva, Alex M. Garcia, Bruno Schuermans, Nicolas Noiray, Wolfgang Polifke

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

Thermoacoustic combustion instability is a major concern in gas turbine combustors with hydrogen-enriched fuels. Unsteady combustion not only generates acoustic waves, but it may also result in ŕuctuations of burnt gas temperature, referred to as entropy waves. They are convected by the mean ŕow through the combustor and can cause indirect combustion noise when they are accelerated at the exit. In this work, we demonstrate that entropy waves occur in a fully premixed burner due to unsteady heat transfer at the combustion chamber wall. This mechanism of entropy generation is often neglected in the literature. This work shows an additional mechanism in CH4-H2-air ŕames, through which entropy may be created even in the fully premixed case. This is due to differential diffusion which generates local ŕuctuations in equivalence and carbon-to-hydrogen ratios. An adiabatic ŕame temperature is deőned based on these two quantities to examine the inŕuence of differential diffusion on the generation of entropy ŕuctuations. The generation of entropy waves is investigated by applying system identiőcation (SI) to time series data obtained from a broadband forced large eddy simulation (LES) coupled with a heat conduction solver. The entropy transfer function (ETF) and ŕame transfer function (FTF) identiőed are then compared to experimental data obtained with tunable diode laser absorption spectroscopy with wavelength modulation spectroscopy (TDLAS-WMS) for measuring temperature ŕuctuations, and the multi-microphone method (MMM), respectively. After validating the computational setup, the entropy frequency response is identiőed at various positions within the combustion chamber, and the effects of generation and convective dispersion of entropy waves are qualitatively investigated. We show that a fully premixed turbulent system may exhibit signiőcant entropy waves caused by wall heat losses and differential diffusion of hydrogen.

Original languageEnglish
Title of host publicationCombustion, Fuels, and Emissions
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791886960
DOIs
StatePublished - 2023
EventASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023 - Boston, United States
Duration: 26 Jun 202330 Jun 2023

Publication series

NameProceedings of the ASME Turbo Expo
Volume3B-2023

Conference

ConferenceASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023
Country/TerritoryUnited States
CityBoston
Period26/06/2330/06/23

Keywords

  • Entropy waves
  • hydrogen enrichment
  • indirect combustion noise
  • large eddy simulation
  • laser absorption spectroscopy
  • system identiőcation

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