Rotor Performance Enhancement and Vibration Reduction in Presence of Dynamic Stall Using Actively Controlled Flaps

نویسندگان

  • Li Liu
  • Peretz P. Friedmann
  • Insung Kim
  • Dennis S. Bernstein
چکیده

A computational study of helicopter vibration and rotor shaft power reduction is conducted using activelycontrolled trailing-edge flaps (ACFs), implemented in both single and dual flap configurations. Simultaneous vibration reduction and performance enhancement is demonstrated under level flight condition at high advance ratios, where dynamic stall effects are significant. Power reduction is achieved using the adaptive Higher Harmonic Control (HHC) algorithm in closed loop, with 2-5/rev flap control harmonics. This approach is compared with an off-line, nonlinear optimizer available in MATLAB, and favorable comparisons are obtained. A parametric study of flap spanwise location is also conducted to determine its optimal location for power reduction. The effectiveness of the ACF approach for power as well as simultaneous vibration and power reduction is also compared with conventional individual blade control (IBC) approach. Rotor power reduction and simultaneous reduction of vibration and power are shown to be larger at higher rotor thrust and advance ratio. Finally, the effect of active flap on dynamic stall is examined to determine the mechanisms of rotor power reduction. The simulation results clearly demonstrate the potential of the ACF system for power reduction as well as simultaneous vibration and power reduction. Nomenclature c Blade chord cc Flap chord CT Rotor thrust coefficient D Matrix defined as TTQT+R fb(.) Blade equations of motion ft(.) Trim equations FHX4,FHY4, FHZ4 4/rev hub shears, nondimensionalized by MbΩR MHX4,MHY4, MHZ4 4/rev hub moments, nondimensionalized by MbΩR J Quadratic-form objective function to be minimized Presented at the American Helicopter Society 62nd Annual Forum, Phoenix, AZ, June 9-11, 2006. 1 Mb Blade mass mc Flap mass per unit length, nondimensionalized by Mb/R MHz1 Yawing moment about rotor hub Nb Number of rotor blades PR Rotor shaft power, nondimensionalized by MbΩR qt Vector of trim variables qti Vector of trim variables at i-th control step Q Weighting matrix for objectives to be minimized R Weighting matrix on control input R Rotor blade radius Rt Trim residuals vector T Sensitivity, transfer matrix between control inputs and objective function uk Control input vector, kth control step uk,opt Optimum value of control input vector xc Spanwise location of center of control surface zk Objective vector, kth control step αR Rotor shaft angle of attack δ f Flap deflection angle ∆Cd,flap Additional drag due to flap deflection δNc,δNs N/rev cosine and sine amplitude of δ βp Blade precone angle γ Lock number μ Helicopter advance ratio ωF , ωL, ωT Blade flap, lead-lag and torsional natural frequencies Ω Rotor angular speed ψ Rotor azimuth angle φR Lateral roll angle θ0,θ1c,θ1s Collective and cyclic pitch components θ0t Tail rotor collective pitch θtw Built-in twist angle σ Rotor solidity Introduction and Background Specifications for noise and vibration levels in rotorcraft are continuously increasing in stringency, thus motivating research related to active noise and vibration reduction. Desirable vibration levels have been identified to be below 0.05g to provide passengers with “jet smooth” ride (Ref. 1). A number of active control techniques have emerged for effective vibration reduction (Refs. 1,2), as illustrated schematically in Fig. 1. These approaches generally fall into one of two categories: (a) active control approaches aimed at reducing vibrations in the rotor before they propagate into the fuselage, and (b) active control approaches

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Vibration Reduction and Performance Enhancement in Rotorcraft Using Active Flaps at High Advance Ratios

A computational study of helicopter vibration and rotor shaft power reduction is conducted using actively-controlled trailing-edge flaps (ACFs), implemented in both single and dual flap configurations. Simultaneous vibration reduction and performance enhancement is demonstrated under level flight condition at high advance ratios, where dynamic stall effects are significant. Power reduction is a...

متن کامل

Simultaneous Vibration Reduction and Performance Enhancement in Rotorcraft Using Actively Controlled Flaps

A computational study of helicopter vibration and rotor shaft power reduction is conducted using activelycontrolled trailing-edge flaps (acfs), implemented in single and dual flap configurations. Simultaneous vibration reduction and performance enhancement is demonstrated under level flight condition at high advance ratios, where dynamic stall effects are significant. Power reduction is achieve...

متن کامل

Vibration Reduction and Performance Enhancement of Helicopter Rotors Using an Active/Passive Approach

Active/passive optimization of helicopter rotor blades for vibration reduction and performance enhancement at high advance ratios is studied. Dynamic stall is the dominant source of high vibration levels for this flight regime. In the active/passive approach, active control of vibration and required rotor power is implemented with partial span trailingedge flaps operating according to a closed-...

متن کامل

Hysteresis Characterization in Piezoceramic Stack Actuators and Its Influence on Vibration and Noise Reduction in Helicopters Using Actively Controlled Flaps

In this study, a characterization of hysteresis in a piezoceramic stack actuator similar to those employed in an actively controlled flap (ACF) system is performed to assess the effects of hysteresis on system performance. The effect of unmodeled actuation hysteresis may significantly reduce vibration and noise reduction capabilities. A hysteresis model based on the classical Preisach model has...

متن کامل

Numerical Evaluation of Microflaps for On Blade Control of Noise and Vibration

Active Gurney flaps, or microflaps, are studied to determine their effectiveness in reducing noise and vibration in rotorcraft, as well as improving rotor performance. The effectiveness of the microflap is examined using a comprehensive rotorcraft simulation code. The aerodynamic properties of the microflap is modeled using a nonlinear CFD based reduced order aerodynamic model that takes into a...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2008