Active control of low‐speed turbofan tonal noise

2003 ◽  
Vol 114 (4) ◽  
pp. 2385-2385
Author(s):  
Scott D. Sommerfeldt ◽  
Paul J. Remington
Keyword(s):  
Active Control ◽  
Tonal Noise ◽  
Low Speed

Active control of multimodal tonal noise propagated in circular duct with axial subsonic mean flow until M=0.3

2008 ◽  
Vol 123 (5) ◽  
pp. 3574-3574
Author(s):  
Martin Glesser ◽  
Emmanuel Friot ◽  
Muriel Winninger ◽  
Cédric Pinhède ◽  
Alain Roure
Keyword(s):  
Active Control ◽  
Mean Flow ◽  
Tonal Noise ◽  
Circular Duct

Energy Regenerative and Active Control Suspension

2003 ◽  
Author(s):  
Yohji Okada ◽  
Sang-Soo Kim ◽  
Keisuke Ozawa
Keyword(s):  
Active Control ◽  
Dead Zone ◽  
Simple Experiment ◽  
Damping Force ◽  
Fundamental Idea ◽  
Nonlinear Characteristics ◽  
Low Speed ◽  
Variable Resistance ◽  
Damping Characteristics ◽  
Ac Motor

This paper introduces a variable resistance type energy regenerative suspension using PWM step-up chopper. The energy regenerative suspension has nonlinear characteristics with dead zone for low speed motion. Hence the energy is not regenerated nor has it damping force. In order to overcome this problem, a step-up chopper is introduced between the actuator and the charging circuit. This chopper is controlled by velocity-dependent PWM signal to improve the damping characteristics and the efficiency of the regenerative suspension. The suspension system changes its height according to the carrier load. Hence linear AC motor is used to the isolation actuator. A simple experiment was performed and the results showed better performance than the standard regenerative suspension. The system is planned to be modified incorporating active control. The fundamental idea and the configuration are introduced.

scholarly journals Active control of periodic fan noise in laptops: spectral width requirements in a delayed buffer implementation

2009 ◽  
Vol 7 (02) ◽  
Author(s):  
H. A. Cordourier-Maruri ◽  
F. Orduña-Bustamante
Keyword(s):  
Active Control ◽  
High Performance ◽  
Active Noise Control ◽  
Spectral Width ◽  
Tonal Noise ◽  
Successful Operation ◽  
Noise Sources ◽  
Fan Noise ◽  
Audio Processing ◽  
Cooling Fans

An active control system intended for the reduction of strictly periodic noise components in computer cooling fans is described, which is based on high‐performance digital sound device architectures found in some personal computers. The system overcomes causality and synchronization constrains imposed by delayed buffering, as usually found in computer audio processing. Performance of the system is demonstrated and evaluated through measurements in a physical implementation of active noise control of synthetic tones combined with laptop fan noise, carried out under anechoic and slightly everberant conditions. Tests on other types of tonal noise sources, like an electrical transformer, were also carried out. However, its wider applicability to the cancellation of tonal noise has been proved compromised by weak periodicity issues found and reported in this work. Also, a study of noise spectral width requirements for successful operation is presented.

A compact active control system for tonal noise reduction in axial fans

Noise Notes ◽  
2007 ◽  
Vol 6 (3) ◽  
pp. 37-46
Author(s):  
Anthony Gerard ◽  
Alain Berry ◽  
Patrice Masson
Keyword(s):  
Control System ◽  
Noise Reduction ◽  
Active Control ◽  
Tonal Noise ◽  
Axial Fans ◽  
Active Control System

scholarly journals On active control of laminar–turbulent transition on two-dimensional wings

2011 ◽  
Vol 369 (1940) ◽  
pp. 1382-1395 ◽  
Author(s):  
Ralf Erdmann ◽  
Andreas Pätzold ◽  
Marcus Engert ◽  
Inken Peltzer ◽  
Wolfgang Nitsche
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Active Control ◽  
High Speed ◽  
Control Algorithm ◽  
Frequency Range ◽  
Wind Tunnel Experiments ◽  
Low Speed ◽  
Turbulent Transition ◽  
Mach Numbers

This paper gives an overview of drag reduction on aerofoils by means of active control of Tollmien–Schlichting (TS) waves. Wind-tunnel experiments at Mach numbers of up to M x =0.42 and model Reynolds numbers of up to Re c =2×10 6 , as well as in-flight experiments on a wing glove at Mach numbers of M <0.1 and at a Reynolds number of Re c =2.4×10 6 , are presented. Surface hot wires were used to detect the linearly growing TS waves in the transitional boundary layer. Different types of voice-coil- and piezo-driven membrane actuators, as well as active-wall actuators, located between the reference and error sensors, were demonstrated to be effective in introducing counter-waves into the boundary layer to cancel the travelling TS waves. A control algorithm based on the filtered- x least mean square (FxLMS) approach was employed for in-flight and high-speed wind-tunnel experiments. A model-predictive control algorithm was tested in low-speed experiments on an active-wall actuator system. For the in-flight experiments, a reduction of up to 12 dB (75% TS amplitude) was accomplished in the TS frequency range between 200 and 600 Hz. A significant reduction of up to 20 dB (90% TS amplitude) in the flow disturbance amplitude was achieved in high-speed wind-tunnel experiments in the fundamental TS frequency range between 3 and 8 kHz. A downstream shift of the laminar–turbulent transition of up to seven TS wavelengths is presented. The cascaded sensor–actuator arrangement given by Sturzebecher & Nitsche in 2003 for low-speed wind-tunnel experiments was able to shift the transition Δ x =240 mm (18%  x / c ) downstream by a TS amplitude reduction of 96 per cent (30 dB). By using an active-wall actuator, which is much shorter than the cascaded system, a transition delay of seven TS wavelengths (16 dB TS amplitude reduction) was reached.

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