The thermo-acoustic response of a premixed swirl burner

Abstract

Application of the theory of thermo-acoustic excitation of flames requires a detailed knowledge of the flame response to plane-wave velocity fluctuations of a given frequency through the burner. A model of the type of swirl burner used in some designs of industrial gas turbine is investigated, chemiluminescent emission being used as a marker of the hear release from both methane and propane premixed flames. The effects of the equivalence ratio and the withdrawal of the swirler so as to allow an annulus of unswirled premixture are also examined. It is found that there are two distinct modes of self-excitation. The response of different burner configurations in the mode with the higher frequency is analysed in terms of four parameters. These characterize the position and spread of the axial distribution of heat release fluctuations, and the origin and effective velocity of convection of disturbances. From these parameters, the Rayleigh integral can be calculated and this defines the frequency range over which excitation is possible. If the acoustic conditions require that the flame is lengthened, retracting the swirler, reducing the equivalence ratio or changing from propane to methane are all shown to be possible control measures for this particular burner.

Large Eddy Simulations of gaseous flames in gas turbine combustion chambers

“…These FTF's can then be used along with thermo-acoustic solvers (Helmholtz or network models) to determine the thermo-acoustic stability map of a burner [298,299,347,348]. For such LES [349], the compressible solver needs to consider an acoustically open numerical setup (no acoustic reflection at the inflow and outflow conditions of the LES computational domain).…”

Linear Instability Analysis of Lean Premixed Combustion

“…The acoustic system equations are formulated from basic equations of the fluid dynamics and are considered that heat release can fluctuate because gas flow rate fluctuates acoustically, even if the heat source is steady. In formulating the heat release fluctuation equations, the advection delay time between the fuel nozzle position and the flame position is considered, by referenced the prior reports [7]- [11]. Also, as a more important parameter, the reaction delay time between fuel increase and combustion is considered.…”

A Discrete-Time, State-Space Approach for the Investigation of Non-Normal Effects in Thermoacoustic Systems

“…7, which shows rather erratic behavior with large jumps in operator norm every 10 time advances due to the large time increment of that case, the increased temporal resolution resulted in physically more plausible behavior. Finally, a heat source with a spread of time lags [26,29,30,33,34],…”