A Green’s function approach to the rapid prediction of thermoacoustic instabilities in combustors
| Autor: | Alessandra Bigongiari, Maria A. Heckl |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
Bistability 020209 energy Mechanical Engineering 02 engineering and technology Mechanics Condensed Matter Physics Combustion 01 natural sciences Turbine 010305 fluids & plasmas symbols.namesake Nonlinear system Mechanics of Materials Green's function 0103 physical sciences 0202 electrical engineering electronic engineering information engineering symbols Combustor Reflection (physics) Boundary value problem |
| Zdroj: | Journal of Fluid Mechanics. 798:970-996 |
| ISSN: | 1469-7645 0022-1120 |
| DOI: | 10.1017/jfm.2016.332 |
| Popis: | The prediction of thermoacoustic instabilities is fundamental for combustion systems such as domestic burners and industrial gas turbine engines. High-amplitude pressure oscillations cause thermal and mechanical stress to the equipment, leading to premature wear or even critical damage. In this paper we present a new approach to produce nonlinear (i.e. amplitude-dependent) stability maps of a combustion system as a function of various parameters. Our approach is based on the tailored Green’s function of the combustion system, which we calculate analytically. To this end, we assume that the combustor is one-dimensional, and we describe its boundary conditions through reflection coefficients. The heat release is modelled by a generalised $n{\it\tau}$ law. This includes a direct-feedback term in addition to the usual time-lag term; moreover, its parameters (time lag, coupling coefficients) depend on the oscillation amplitude. The model provides new insight into the physical mechanism of the feedback between heat release rate and acoustic perturbations. It predicts the key nonlinear features of the thermoacoustic feedback, such as limit cycles, bistability and hysteresis. It also explains the frequency shift in the acoustic modes. |
| Databáze: | OpenAIRE |
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