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26-10-12 14:15 Age: 5 years

By:  Dr. Matthew P. Juniper (Univ of Cambridge, UK)

Sensitivity Analysis in Combustion Dynamics Based on Adjoint Equations


Abstract

We apply adjoint-based sensitivity analysis to a time-delayed thermo-acoustic system: a Rijke tube containing a hot wire. We calculate how the growth rate and frequency of small oscillations about a base state are affected either by a generic passive control element in the system (the structural sensitivity analysis) or by a generic change to its base state (the base-state sensitivity analysis). We illustrate the structural sensitivity by calculating the effect of a second hot wire, with a small heat release parameter. We find the positions at which it has an optimal influence on the oscillations. We illustrate the base-state sensitivity by calculating the effects of tiny variations in the the damping factor, the heat-release time-delay coefficient, the heat-release parameter, and the hot wire location. The successful application of sensitivity analysis to thermo-acoustics opens up new possibilities for the passive control of thermo-acoustic oscillations, by providing gradient information that can be combined with constrained optimization algorithms in order to reduce linear growth rates.


Files:
 Juniper Cambridge (53 KB)
26-10-12 14:15 Age: 5 years

By:  Dr. Matthew P. Juniper (Univ of Cambridge, UK)

Sensitivity Analysis in Combustion Dynamics Based on Adjoint Equations


Abstract

We apply adjoint-based sensitivity analysis to a time-delayed thermo-acoustic system: a Rijke tube containing a hot wire. We calculate how the growth rate and frequency of small oscillations about a base state are affected either by a generic passive control element in the system (the structural sensitivity analysis) or by a generic change to its base state (the base-state sensitivity analysis). We illustrate the structural sensitivity by calculating the effect of a second hot wire, with a small heat release parameter. We find the positions at which it has an optimal influence on the oscillations. We illustrate the base-state sensitivity by calculating the effects of tiny variations in the the damping factor, the heat-release time-delay coefficient, the heat-release parameter, and the hot wire location. The successful application of sensitivity analysis to thermo-acoustics opens up new possibilities for the passive control of thermo-acoustic oscillations, by providing gradient information that can be combined with constrained optimization algorithms in order to reduce linear growth rates.


Files:
 Juniper Cambridge (53 KB)

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