scholarly journals Stability Characteristics of a Model Trim Adjustment System for Open Loop Active Control of Thermoacoustic Instability

2019 ◽  
Vol 11 ◽  
Author(s):  
Varghese M Thannickal ◽  
T John Tharakan ◽  
Satyanarayanan R Chakravarthy
Keyword(s):  
Active Control ◽  
Open Loop ◽  
Thermoacoustic Instability ◽  
Adjustment System

Suppression of Instabilities in Gaseous Fuel High-Pressure Combustor Using Non-Coherent Oscillatory Fuel Injection

2003 ◽  
Author(s):  
D. Shcherbik ◽  
E. Lubarsky ◽  
Y. Neumeier ◽  
B. T. Zinn ◽  
K. McManus ◽  
...  
Keyword(s):  
High Pressure ◽  
Active Control ◽  
Fuel Injection ◽  
Injection Rate ◽  
Open Loop ◽  
Combustion Instabilities ◽  
Open Loop Control ◽  
Pressure Oscillations ◽  
Loop Control ◽  
Fuel Injection Rate

This paper describes the application of active, open loop, control in effective damping of severe combustion instabilities in a high pressure (i.e., around 520 psi) gas turbine combustor simulator. Active control was applied by harmonic modulation of the fuel injection rate into the combustor. The open-loop active control system consisted of a pressure sensor and a fast response actuating valve. To determine the dependence of the performance of the active control system upon the frequency, the fuel injection modulation frequency was varied between 300 and 420 Hz while the frequency of instability was around 375 Hz. These tests showed that the amplitude of the combustor pressure oscillations strongly depended upon the frequency of the open loop control. In fact, the amplitude of the combustor pressure oscillations varied ten fold over the range of investigated frequencies, indicating that applying the investigated open loop control approach at the appropriate frequency could effectively damp detrimental combustion instabilities. This was confirmed in subsequent tests in which initiation of open loop modulation of the fuel injection rate at a non resonant frequency of 300Hz during unstable operation with peak to peak instability amplitude of 114 psi and a frequency of 375Hz suppressed the instability to a level of 12 psi within approximately 0.2 sec (i.e., 75 periods). Analysis of the time dependence of the spectra of the pressure oscillations during suppression of the instability strongly suggested that the open loop fuel injection rate modulation effectively damped the instability by “breaking up” (or preventing the establishment of) the feedback loop between the reaction rate and combustor oscillations that drove the instability.

Modelling and Control of HSFDs for Active Control of Rotor-Bearing Systems

1994 ◽  
Author(s):  
A. El-Shafel ◽  
J. P. Hathout
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Transient Behavior ◽  
Pressure Control ◽  
Fast Response ◽  
Open Loop ◽  
Loop System ◽  
Squeeze Film ◽  
Open Loop System ◽  
Loop Control

This paper summarizes the development of hybrid squeeze film dampen (HSFDs) for active control of rotor vibrations. Previously, it was shown both theoretically and experimentally that HSFDs can be used for controlling rotor vibrations (El-Shafei, 1993). This is done by controlling the flow in a squeeze film damper through movable end seals, thus achieving the ability to change the damper from a short damper to a long damper and vice versa. However, the control of the HSFD was manual. In this paper, an automatically controlled circuit is developed for the HSFD, incorporating a pressure control servovalve for controlling the pressure in the scaling chambers. A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. The transient behavior of the system, including the sealing ring dynamics, illustrates that the open-loop system exhibits well behaved, stable, and fast response. In addition it is shown that the HSFD can achieve any amount of damping between the short and long damper modes through the accurate positioning of the sealing rings. The simulation results illustrate that the automatically controlled HSFD can be a very useful device for the active control of rotors. A closed loop control strategy with feedback on rotor speed is also investigated both from the points of view of steady state and transient behaviors. It is shown that this closed loop strategy results in a much improved behavior of the rotor system.

Integrated Rotor Performance Improvement and Vibration Reduction Using Active Camber Morphing

2019 ◽  
Author(s):  
Sumeet Kumar ◽  
Dominik Komp ◽  
Manfred Hajek ◽  
Jürgen Rauleder
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Vibration Reduction ◽  
Fish Bone ◽  
Open Loop ◽  
Beam Elements ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line ◽  
Lifting Line Theory

Abstract This paper discusses open-loop and closed-loop active control investigations of a full-scale Bo 105 helicopter rotor with active camber morphing. The potential of an active camber morphing concept to reduce non-rotating vibratory hub loads and rotor power using active control was investigated. The mechanism employed was a dynamically actuated airfoil camber morphing concept known as Fish Bone Active Camber (FishBAC) that smoothly deforms the camber over the aft section of the airfoil. A comprehensive rotorcraft aeromechanics analysis was used that modeled the blade elastic motion using one-dimensional finite beam elements combined with multibody dynamics. Aerodynamic forces were calculated with a free-vortex wake model together with lifting line theory for the blade aerodynamics. The open-loop investigation comprised of a parametric study of relevant control parameters that govern the active camber deflection cyclic actuation profile and their effects on rotor performance and hub vibration. It was found that active camber morphing using superimposed once-per-revolution (1P) and 2P control inputs was able to simultaneously reduce rotor power by 4.3% and overall vibratory hub loads by 27%. Additionally, a closed-loop adaptive multicyclic controller was used to identify the potential of this morphing concept for hub vibration reduction using multicyclic active control inputs. Active camber actuation using a sum of four control harmonic inputs, i.e. 1-4P, resulted in a maximum hub vibration reduction of 50%.

Active control of thermoacoustic instability using microsecond plasma discharge

2020 ◽  
Vol 127 (3) ◽  
pp. 033301
Author(s):  
Mingxuan Zhang ◽  
Jingxuan Li ◽  
Wenwang Cheng ◽  
Ting Li
Keyword(s):  
Active Control ◽  
Plasma Discharge ◽  
Thermoacoustic Instability

Active Control of Combustion Noise by a Twin Resonator Trim Adjustment System

2021 ◽  
pp. 1-24
Author(s):  
Varghese M. Thannickal ◽  
T. John Tharakan ◽  
Satyanarayanan R. Chakravarthy
Keyword(s):  
Active Control ◽  
Combustion Noise ◽  
Adjustment System

Open loop characterization of an active control system of MHD modes

2005 ◽  
Vol 74 (1-4) ◽  
pp. 555-560 ◽  
Author(s):  
G. Marchiori ◽  
A. Masiello ◽  
P. Brunsell ◽  
D. Yadikin
Keyword(s):  
Control System ◽  
Active Control ◽  
Open Loop ◽  
Active Control System

Modelling of a Hybrid Constrained Layer/Piezoceramic Approach to Active Damping

1997 ◽  
Vol 119 (1) ◽  
pp. 120-130 ◽  
Author(s):  
J. A. Rongong ◽  
J. R. Wright ◽  
R. J. Wynne ◽  
G. R. Tomlinson
Keyword(s):  
Active Control ◽  
Laboratory Experiments ◽  
Dynamic Behaviour ◽  
Flexural Vibration ◽  
Open Loop ◽  
Structural Vibration ◽  
Constrained Layer Damping ◽  
Element Analysis ◽  
Cantilevered Beam ◽  
And Performance

It has been shown that significant reductions in structural vibration levels can be achieved using a hybrid system involving constrained layer damping and active control with piezoceramics. In this paper, mathematical models based on the Rayleigh Ritz approach, are developed to describe the longitudinal and flexural vibration behaviour of a cantilevered beam when excited using piezoceramic patches bonded to a constrained layer damping treatment. Predictions of static and steady state dynamic behaviour, obtained using the models are validated by comparison with results from finite element analysis and laboratory experiments. The models are then used in open loop and closed loop velocity feedback control simulations to demonstrate the improvements in stability and performance achieved using this method over that achieved using conventional active control.

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