Influence of Heat Transfer and Material Temperature on Combustion Instabilities in a Swirl Burner

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 17948 The current work focuses on the large eddy simulation (LES) of combustion instability in a laboratory-scale swirl burner. Air and fuel are injected at ambient conditions. Heat conduction from the combustion chamber to the plenums results in a preheating of the air and fuel flows above ambient conditions. The paper compares two computations: In the first computation, the temperature of the injected reactants is 300 K (equivalent to the experiment) and the combustor walls are treated as adiabatic. The frequency of the unstable mode (% 635 Hz) deviates significantly from the measured frequency (% 750 Hz).In the second computation, the preheating effect observed in the experiment and the heat losses at the combustion chamber walls are taken into account. The frequency (% 725 Hz) of the unstable mode agrees well with the experiment. These results illustrate the importance of accounting for heat transfer/losses when applying LES for the prediction of combustion instabilities. Uncertainties caused by unsuitable modeling strategies when using computational fluid dynamics for the prediction of combustion instabilities can lead to an improper design of passive control methods (such as Helmholtz resonators) as these are often only effective in a limited frequency range.

Flame Extinction and Re-Ignition in a Swirl Stabilized Prevaporized Liquid Fuel Flame Close to Lean Blow-Out

“…Further, the design allows for several identical burners to be combined into a combustor array, in order to investigate cross-flame interactions [25]. Previous studies have focused on the feedback mechanism of the thermo-acoustic cycle [21], the variations of the thermo-chemical state throughout the acoustic cycle [22], the influence of the air split ratio on the dynamics of a precessing vortex core (PVC) [23] and the impact of the material temperature on thermo-acoustic properties of the burner [26].…”

Coupling heat transfer and large eddy simulation for combustion instability prediction in a swirl burner

“…The PIV measurements were performed by DLR Stuttgart [18] . Figure 7 shows the mean velocity profiles and Fig.…”

“…Another example is the study by Kraus et al [18] , who compared an adiabatic LES and an LES with basic modeling of heat transfer between fluid and solid material. Both LESs show the same mode structure, but taking into account heat transfer effects leads to a higher accuracy in terms of frequency.…”

“…where R is roughly evaluated from the combustor wall characteristics [18,[30][31][32] . This is a cheap method to account for dual heat transfer between reacting flow and conduction through walls.…”

Combustion Characteristics of n-heptane Through Temperature Variation Measurements Using Ignition Quality Tester

“…The heated IQT chamber is pressurized with charge air through intake valve from a high pressure and ambient temperature air cylinder and kept for few seconds before fuel injection. Prior to the fuel injection, air pressure inside the IQT chamber is almost constant with a thermal gradient along the chamber due to cooling effects on both ends Switching walls to heat transfer case has no effects on combustion process [133] which lasts only a very short period.…”