Placement of Helmholtz resonators in series for passive control of thermoacoustic instabilities from a time-delay perspective

2016 ◽  
Author(s):  
Umut Zalluhoglu ◽  
Nejat Olgac
Keyword(s):  
Time Delay ◽  
Passive Control ◽  
Thermoacoustic Instabilities ◽  
Helmholtz Resonators ◽  
In Series

Observer-based reliable passive control for uncertain T–S fuzzy systems with time-delay

2019 ◽  
Vol 50 (5) ◽  
pp. 905-918 ◽  
Author(s):  
Hao Yan ◽  
Jianwen Wang ◽  
Fuzhong Wang ◽  
Zhiqiang Wang ◽  
Shuangquan Zou
Keyword(s):  
Time Delay ◽  
Fuzzy Systems ◽  
Passive Control

Acoustic Damper Placement and Tuning for Annular Combustors: An Adjoint-Based Optimization Study

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Georg A. Mensah ◽  
Jonas P. Moeck
Keyword(s):  
Helmholtz Equation ◽  
Gas Turbines ◽  
Algebraic Models ◽  
Combustion Chambers ◽  
Thermoacoustic Instabilities ◽  
Helmholtz Resonators ◽  
Major Threat ◽  
Optimization Study ◽  
Annular Combustor ◽  
Parameter Values

Thermoacoustic instabilities pose a major threat to modern gas turbines. The use of acoustic dampers, like Helmholtz resonators, has proven useful for the mitigation of such instabilities. However, assessing the effect of acoustic dampers on thermoacoustic modes in annular combustion chambers remains an intricate task. This results from the implicit nature of the thermoacoustic Helmholtz equation associated with the high number of possible parameter values for the positioning of the dampers and their impedance design. In the present work, the principal challenges of the effective placement and the design of the impedance of acoustic dampers in annular chambers are discussed. This includes the choice of an appropriate objective function for the optimization, the combinatorial challenges when dealing with different possible damper arrangements, and the numerical complexities when using the thermoacoustic Helmholtz equation to approach this issue. As a key aspect, the paper proposes a new adjoint-based approach to tackle these problems. The new algorithm establishes algebraic models that predict the effect of acoustic dampers on the growth rates of the thermoacoustic modes. The theory is exemplified on the basis of a generic annular combustor model with 12 burners.

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

2016 ◽  
Vol 139 (5) ◽  
Author(s):  
Christian Kraus ◽  
Laurent Selle ◽  
Thierry Poinsot ◽  
Christoph M. Arndt ◽  
Henning Bockhorn
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Passive Control ◽  
Unstable Mode ◽  
Combustion Instabilities ◽  
Ambient Conditions ◽  
Swirl Burner ◽  
Helmholtz Resonators ◽  
Eddy Simulation ◽  
Limited Frequency

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.

A Novel PID Controller with Second Order Lead/Lag Filter for Stable and Unstable First Order Process with Time Delay

2018 ◽  
Vol 13 (1) ◽  
Author(s):  
Praveen Kumar Medarametla ◽  
Manimozhi Muthukumarasamy
Keyword(s):  
Time Delay ◽  
Pid Controller ◽  
Chemical Reactor ◽  
Initial Guess ◽  
Second Order ◽  
Maximum Sensitivity ◽  
Tuning Parameter ◽  
First Order ◽  
In Series ◽  
Made In

AbstractA novel Proportional-Integral-Derivative (PID) controller is proposed for stable and unstable first order processes with time delay. The controller is cascaded in series with a second order filter. Polynomial approach is employed to derive the controller and filter parameters. Simple tuning rules are derived by analysing the maximum sensitivity of the control loop. Formulae are provided for initial guess of tuning parameter. The range of tuning parameter around the initial guess and the corresponding range of maximum sensitivity is specified based on time delay to time constant ratio. Promising results are obtained with the proposed method is compared against recently proposed methods in the literature. The comparison is made in terms of various performance indices for servo and regulatory responses separately. The proposed method is implemented for an isothermal chemical reactor at an unstable equilibrium point.

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