Active Gurney Flaps: Their Application in a Rotor Blade Centrifugal Field

Abstract

Miniature trailing-edge effectors are segmented gurney flaps that can deploy to achieve multipurpose functions, such as performance enhancement, noise/vibration control, and/or load control on rotor blades. The unsteady aerodynamics of miniature trailing-edge effectors and a déployable plain flap (with an equivalent lift gain) are quantifled experimentally at a reduced frequency of 0.21 and a Reynolds number of 1 x lO". These experiments are also simulated using computational fluid dynamics. The combination of the wind tunnel experiments and computational fluid dynamics are used to quantify the aerodynamic effects of miniature trailing-edge effector deployment to compare their unsteady aerodynamics to plain flaps, and to evaluate the fluid dynamics of miniature trailing-edge effectors against experimental data. The current experiments display unsteady aerodynamics that corroborate previous computational fluid dynamics flndings that indicate that miniature trailing-edge effectors shed on-surface vortices during deployment, affecting the unsteady aerodynamics of the system. Computational fluid dynamics also predicted that miniature trailing-edge effectors require 1/55 power to deploy compared to a plain-flap configuration. Power reduction is a key attractor for the integration of de vices on smart rotors. This work is concluded with an effort that displays that the low power requirement of miniature trailing-edge effectors enable simple deployment methods, such as the use of pressure differentials inherent to the rotor blades. The proposed pneumatic miniature trailing-edge effector configuration was tested at centrifugal forces representative of helicopter rotor blades.Ci cf" (-norm Cf C CL CM

Linear Reduced-Order Model for Unsteady Aerodynamics of an L-Shaped Gurney Flap

“…Many CFD results on GFs are available in the literature [25,30,33], which employ computational grids with no slots between the GF surface and the airfoil. Because the grid of the present work is conceived to present a finite slot between the airfoil and the L-tab, it is important to estimate the effects of such a gap on the numerical solutions.…”

“…Moreover, classical sliding actuation solutions, widely used for fixed wing GFs, are likely to fail, under high centrifugal loads that affect rotor blades. Palacios et al [33] carried out several experimental tests to investigate the behavior of MITEs under centrifugal loads comparable to those encountered on rotor blades. They found that such devices can operate in these conditions.…”

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

“…In addition, active Gurney flaps (deployable flaps or miniature trailing-edge effectors) have been under investigation [88,92]. Byerley et al [96] presented the need to retract the Gurney flap with high Reynolds numbers when separation does not occur, which would make the Gurney flap an active flow control method.…”

“…Better lift augmentation at higher Re [82] 2015 Gurney flap 2%c 255,000; 360,000 35-40% increase in tangential force [84] 2015 Gurney flap Axial pump 0.7-1.4%c 690,000 25% increase in pump head, widened operating range, decreased efficiency [59] 2014 Microtab Wind turbine 0.5-1.2%c 1,000,000 Increased lift and drag [88] 2014 Gurney flap 2%c 1,000,000 Lift augmentation, vibration control [86] 2013 Gurney flap 1.04-2.38%c 1,000,000 Effect on max. lift coefficient depends on airfoil shape [89] 2012 Gurney flap Centrifugal fan 15.9%b 2 30,000-82,000 Pressure ratio and operating range improved at Re < 69,000 [81] 2012 Gurney flap 3-7%c 20,000-35,000 Lift augmentation [90] 2011 Gurney flap Axial fan 10, 20, 30%c < 100,000 Max 18% increase in efficiency with q v,max [83] 2011 Gurney flap 0.7-6%c 254,000 Lift and drag augmentation [91] 2011 Gurney flap 1-6%c 105,000 Wake vortex control [92] 2011 Gurney flap 1.5%c 2,100,000 Vibration reduction [93] 2010 Jet-flap LPT cascade 25,000-200,000 12.5% reduction in solidity [94] 2010 Gurney flap LPT cascade 0.5-3%c 25,000-200,000 12.5% reduction in solidity [8] 2010 Microtab Wind turbine 1-1.5%c 460,000 Max 37% increase in lift [35] 2010 Gurney flap 3000-20,000 Lift augmentation [95] 2010 Gurney flap 40,000-80,000 Lift augmentation [96] 2003 Gurney flap Turbine cascade 0.6-2.7%c 28,000-167,000 Max 9% increase in lift force [85] 2000 Gurney flap 0.5-2%c 1,000,000 Increased lift and drag Outcome: Lift augmentation…”

Method for Calculating Rotors with Active Gurney Flaps

“…In their study, a Gurney flap was deployed over the entire span of the blade. Finally, Palacios et al [16] compared both experimentally and numerically the power required to deploy a Gurney flap against a plain flap on a K-max rotor blade, as well as the efficiency of those devices. According to the authors, Gurney flaps appear to be most suitable where the devices can enable improved reliability or the deployment mechanisms heavily favour Gurney flaps over plain flaps.…”