Lift Enhancement for Upper Surface Blowing (USB)...

Copyright © 2013 Boeing. All rights reserved.

Lift Enhancement for Upper Surface Blowing (USB)

Airplanes

Yoram Yadlin and Arvin Shmilovich Huntington Beach, CA

12th Symposium on Overset Composite Grids and Solution Technology

Atlanta, Georgia

October 6-9, 2014

Engineering, Operations & Technology | Boeing Research & Technology


• Introduction

− Powered lift concepts

• Current Study

− Analysis approach

− Numerical method

− Validation

− Baseline configuration

• USB Enhancement Techniques

− Geometrical modifications

− Active Flow Control (AFC)

− AFC concept

− Actuation modes

− Constant

− Pulsed

− Sprinkler

Outline

| 2 12th Symposium on Overset Composite Grids and Solution Technology,

October 6-9, 2014



• Coanda Effect “Deviation of a plain jet of a fluid

that penetrates another fluid in the

vicinity of a convex wall”

Powered lift concepts

• Increase lift production by exploiting engine exhaust jet • Externally Blown Flaps (EBF)

• Internally Blown Flaps (IBF)

• Upper Surface Blowing (USB)

EBF

USB

Avrocar circa 1958


October 6-9, 2014

//upload.wikimedia.org/wikipedia/commons/5/59/C-17_no169_landing.jpg



Experimental confirmation

Boeing V/STOL (Philadelphia, July 2007)

Power off

Power on Power

USB

Single element, simple hinge flap

3-element slotted slat and flap

Speed Agile Concept Demonstrator

- AFRL

- Advanced Joint Air Combat System (AJACS)


October 6-9, 2014



Current study

• Problem

− Premature jet peeling-off degrades lifting capability

• Ratio of Jet thickness to surface radius of curvature:

− Thin jet

− Large radius of curvature

• Edge effects

− Spanwise extent of nozzle

− Edge vortex formation

• Objective

−Develop technologies for enhanced USB systems

• Approach −Geometrical modifications

−Active Flow Control


October 6-9, 2014



Analysis approach

•CFD based evaluation of the new technologies • Validation

• Application to USB enhanced concepts

•Numerical tool • Unsteady RANS (OVERFLOW with Boeing’s modification)

• Overset grid system

• Upwind scheme

• One-equation (S-A) turbulence model

• Time-varying boundary conditions


October 6-9, 2014



Numerical validation

Illinois Institute of technology 2007 test:

•CFD Model: •10.5 million points •34 zones


October 6-9, 2014



CT = 0.8 near sonic nozzle

Numerical validation - sample


October 6-9, 2014



USB baseline configuration

Computational test bed is based on the IIT model

•Wing of constant chord between 2 vertical walls

•Full span flap

•Nozzle aspect ratio of 6

•AFC slots embedded in flap upper surface

•Height of slot is 0.2% chord


October 6-9, 2014



USB flow features

Separation bubble

Engine plume (M=0.7)

Cross sectional vorticity

Power off Power on (takeoff)

Analysis tools •Extent of separation

•Shape of engine plume

•Vorticity field

Flow Features •Lift increment of 16%

•Flow reattachment behind engine

•Roll-up of engine plume at edge of nozzle


October 6-9, 2014



Techniques for enhanced USB

Enhanced Coanda effect:

─ Reshape flap upper surface

─ Elongated nozzle

Mitigate nozzle edge effects:

─ Nozzle edge effects

─ Flow control methods:

Constant blowing

Pulse actuation

Sprinkler actuation


October 6-9, 2014



High curvature flap

• 4.7% increase in wing chord

• Lift increase of 12%

•Augmented Coanda effect over only 28% of wing

R = r

R = 2r


October 6-9, 2014



High aspect ratio nozzle

• Double nozzle width

• Fix nozzle exit area (fixed ṁ)

Reducing thickness of jet plume

Larger USB affected area

Flow is effectively more 2D

• Smoother spanload distribution AR=20

AR=6


October 6-9, 2014



fence

Flap fences

• Control edge effects

• Prevent vortex roll-up

• Reduce three-dimensionality of flow

• Variable height

• Fixed or automatically deployed

Y

Z

X


October 6-9, 2014



Power Off

Flap fences effects

Flow separation

Power On Flap fences

Engine Plume (M=0.7) Cross sectional vorticity contours Flow separation

Power On Power On Flap fences

Engine Plume (M=0.7) Cross sectional vorticity contours

Fully attached flow

Elongated nozzle = 16

Wider plume

Weaker edge vortices

Fully attached flow over flap

High LE pressure suction due to increased circulation


October 6-9, 2014



Flap fences performance

CL

4 8 12 16 20 240.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

3.6

4.0

4.4

4.8

5.2

5.6

Power on andfences deployed

Power off

Power on

• Higher load distribution is achieved across the entire span

• The flow becomes more “2d”-like between fences


October 6-9, 2014



Active Flow Control

• Lift enhancement through delayed flow separation at

high angles of attack − Zero mass flow devices

− Fluidic device

o Source of air

− Engine bleed

− Dedicated compressor

o Actuation type

− Constant blowing from a fixed orifice

− Variable blowing

Pulse actuation ---periodic variation of jet velocity

Sprinkler actuation ---continuous swiveling of blowing jet


October 6-9, 2014

C17.pulse.short.zoom.avi

C17.sprinkler.zoom.avi

C17.sprinkler.zoom.avi



Active Flow Control setup

Engine cowl Nozzle exit plane

Controller

Distribution valve

Extraction tube

Deflected wing flap

Engine exhaust

Ejection slots

Cut through the engine

Bleed off engine exhaust for

actuation at plume’s edges


October 6-9, 2014



Constant blowing

AFC Off

AFC On

Control Off

Control On

Top view Exhaust plume Vertical cut through ports

Engine Plume (M=0.7)

Higher exhaust turning results in increased circulation

Actuation results in increased USB effectiveness


October 6-9, 2014



Constant blowing (cont.)

Baseline Pattern 1 Pattern 2 Pattern 3

Alternative actuation patterns:

• multiple flight conditions

• uncertainties in plume location

no actuation


October 6-9, 2014



•Reduce bleed air requirement

−Reduce engine size/weight

•Wide range of actuations modes

− Physical distribution

− Frequency

− Phase

Pulsed actuation


October 6-9, 2014



Engine exhaust

Baseline

Separated flow

Intermittent (instantaneous)

Pulsed actuation cleans up flow separation

Pulsed actuation flow field


October 6-9, 2014



Alternate between left and right blowing

Constant actuation

Intermittent actuation

RHS stroke

LHS stroke

Pulsed actuation effectiveness

1

2

mBl

- Bleed for actuation

mEng

- Nozzle mass flow rate

3 pairs

2

1

3 pairs

mBl

/ mEng

C

L

0.00 0.05 0.10 0.150.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Constant

Intermittent

Original nozzle = 10


October 6-9, 2014



Constant engine bleed Constant lift increment

C

L/

mA

FC

c

8 12 16 20 24 28 320.0

0.4

0.8

1.2

1.6

Efficiency

Advantages of pulsed actuation

Constant engine bleed Constant lift increment

11.2% bleed

Power off

3.7% bleed

CL

8 12 16 20 24 28 32

3.2

4.0

4.8

5.6

6.4

7.2

Baseline (no actuation)ConstantIntermittent

Power off

3.7% bleed

CL

8 12 16 20 24 28 32

3.2

4.0

4.8

5.6

6.4

7.2


October 6-9, 2014



Pulsed actuation animation

Elongated nozzle


October 6-9, 2014



Sprinkler Actuation

•Multiple flight conditions requires flexibility:

• Edge of jet plume might vary

• A-priori placement of ports may not be practical

• Need a “wide area coverage” device

Sprinkler actuator :

• Continuous/swiveling blowing

• Swiveling nozzle

• Louver/vanes system

Vane


October 6-9, 2014



Sprinkler actuation - results

Baseline

Instantaneous flow structure (limit cycle)

• Pair of jets

• Oscillating ±30º from side to side

• Frequency of 10Hz


October 6-9, 2014

usb.sprinkler.avi



Summary

• Upper surface blowing is an effective tool in lift enhancement

• Degradation in USB effectiveness due to − Premature separation

− Nozzle edge effects

• Techniques for lift enhancement: − Geometrical modifications:

Flap upper surface

Larger aspect-ratio nozzle

Flap fences

− Active Flow Control

Constant actuation

Pulsed actuation for increase efficiency

Sprinkler actuation for increased flexibility


October 6-9, 2014

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Lift Enhancement for Upper Surface Blowing (USB)...

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