Full Scale Testing of a Centrifugally Powered Pneumatic Deicing System for Helicopter

Rotor Blades

Matthew Drury - Graduate Research Assistant, Aerospace Engineering

Dr. Joseph Szefi – President, Invercon

Dr. Jose Palacios – Assistant Professor, Aerospace Engineering

Funded by NASA LEARN NNX14AF54A

NASA Aeronautics Research Mission Directorate (ARMD)

2015 LEARN Technical Seminar

September 30, 2015

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 2

Aircraft icing is introduced by both its mission requirements and operation environments:

• Urgent transportation

• Search and rescue

• Low altitude

• Low temperature

• High humidity, icing cloud possible

Unique features of helicopter icing:

– Increased torque required to maintain RPM

– Excessive vibration due to blade imbalance

– Loss of control and maneuverability

– Loss of autorotation capability

– Ballistic impacts from ice shedding

Ultimate goal of aircraft icing research: All weather aircraft

Need for fundamental research to:

Improve and validate ice accretion tools

Develop and evaluate ice protection systems and protective surfaces

Develop facilities and testing procedures

A rescue helicopter waiting to be rescued

Source: BBC NEWS, Mar 2nd 2006 (http://news.bbc.co.uk/2/hi/in_pictures/4768180.stm)

Introduction to Icing

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 3

• Only system qualified by the FAA and the DoD

• Heavy system (4 Blades 12,000 lbs Model: >160 lbs.)

• Does not allow for continuous application due to high power

consumption

(4 Blades, 12,000 lbs Vehicle: >20 KW, ~25 W/in2)

• Allows ice accretion up to 0.3 in (10% Torque Increase)

• Melted ice may flow aft and refreeze further

• Difficult to integrate with polymer erosion-resistant materials

ARMY HISS Icing Certification Testing

Ice Protection System (S-92TM)

A low-power, non-thermal IPS is

desired to have an impact on

all-weather capabilities:

• Compatibility with smaller

vehicles

• Compatibility with polymer

leading edges

Motivation – Electrothermal Deicing

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 4

Penn State AERTS Facility

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 5

Icing Nozzles control

LWC and MVD

AERTS Facility Description

2009: Freezer, motor installed

2010: Ballistic wall, rotor assem., slip ring, actuators, load cell (Boeing, ARMY)

2011: Icing cloud nozzles/controls

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 6

Background

• Pneumatic de-icing boots used on fixed-wing aircraft for decades

• In the 80’s, NASA and Goodrich attempted to develop rotorcraft de-icing boots

• Boots were successful in de-icing rotor blades, several problems were identified:

1) Complicated pneumatic slip-ring transferred engine bleed air out to rotating frame

2) Erosion of polymer boots

3) Altered airfoil shape led to rotor performance degradation

• These problems were technology development barriers

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 7

Patented by Invercon LLC:

“Pneumatic Actuator System for a Rotating Blade”, EFS

ID: 9369871, Application Number:13020333

Centrifugally Powered Pneumatic De-Icing Concept

Channel to Low

Dynamic

Pressure

3-Way Microvalve Off under Non-icing

Conditions, Diaphragm Connected to

Low Pressure

During Icing Conditions,

Microvalve Oscillated at Low

Frequency to Cycle Diaphragm

through Inflation and Deflation

Goal: Surface De-Icing Treatment can be Retrofitted to Existing Blades

• No Pneumatic Slip Ring• Insignificant Electrical Power Use• Insignificant Added Blade Weight

Channel Sealed at Tip

Under Non-Icing

Conditions, Erosion

Cap is “Vacuumed”

onto Airfoil using Low

Tip Pressure

2)( rrdr

dp

p = Pressure, ρ =

Density, r = Radius,

Ω = Rotor Speed

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 8

On-Blade Pressure Generation Testing

Pressure Drop in Full-Scale Rotor

Experimentally Demonstrated: 7.5 PSI

2 Pressure Sensors on Root

2 Pressure Sensors on Tip

280 RPM, 24 ft. Radius Rotor

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 9

On-Blade Pressure Generation Testing

OPEN CLOSED

OPENVALVE

ROOT TIP

7.5 PSI

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 10

Prior Work – Prototype I

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 11

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 12

1. Design a centrifugally powered pneumatic deicing system without the use of inflatable rubberized structures.

2. Evaluate the new system design under rotor icing conditions at the AERTS facility.

3. Integration of the selected system to the outer tip region of a full-scale K-MAX rotor blade.

4. Design and testing of a portable icing cloud generator.

5. Rotor ice testing of the full-scale prototype.

Objectives

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 13

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 14

Pneumatic De-Icing Prototype II Design

Goals:

1. Replace neoprene bags with metallic

pressurized zones.

2. Total system thickness comparable to

existing leading edge caps.

Pressurized Zone

Exaggerated

Displacement

Stainless steel leading

edge cap

Spring steel ribs

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 15

Pneumatic De-Icing Prototype III Design

Goals:

1. Reduce aerodynamic penalty caused by

trailing edge jump

2. Increase transverse shear stresses at

desired chord locations

Segmenting leading edge cap

spanwise creates localized

stresses

Elastomer seals pressurized

zone

Stainless steel

leading edge cap

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 16

• Cohesive interaction used to “attach”

ice to leading edge cap in Abaqus

• Two types of cohesive interactions

defined in Abaqus:

1. Cohesive elements

2. Cohesive surfaces

• Cohesive surfaces have been shown

to be best for ice/leading edge

interface

• Damage models used to predicted

when this cohesive bond fails

Sample Ice Delamination Prediction – Cohesive

Interactions

• Derived from fracture mechanics

• Pneumatic deicing system creates

mixed mode stresses when

pressurized

– Combination of peel and shear

stresses

• Traction separation laws used to model

cohesive damage

• Damage and cohesive parameters were

measured in Phase I

Sample Ice Delamination Prediction – Damage

Modeling

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 19

Sample Ice Delamination Prediction – Blade Tip

• Ice shape geometry created with

LEWICE

• Abaqus cohesive zone methods

predict interfacial delamination

• Centrifugal forces and aerodynamic

pressures not included in analysis

• Ice delamination predictions using

cohesive models used to guide

system design

1

2

1 2

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 20

Rotor Ice Testing

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 21

24 ft. K-MAX Blade

Prototype Ice Testing – Full Scale Representation

Test Method:• Characterize prototype

performance for input pressures produced along a 24 ft. blade

• Centrifugal loads representative of K-MAX 0.5R at 280 RPM Conservative approach

Regime Tested

Full-Scale

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 22

Regime Tested

in AERTS

Rotor Ice Test Results – Prototype II

Prior Pneumatic Deicing Post Pneumatic Deicing

450 RPM

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 23

Pressures reproduced using pneumatic slip-ring

Rotor Ice Test Results – Prototype III

Prior Pneumatic Deicing Post Pneumatic Deicing

385 RPM

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 24

Pressures reproduced using pneumatic slip-ring

Rotor Ice Test Results - Prototype Performance

• Increased input pressure

delaminate smaller ice

thicknesses

• 58% decrease in ice thickness

for delamination from

prototype II to prototype III

0.172 in.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 52

4

6

8

10

12

14

16x 10

-4

Input Pressure (psig)

Ice

Th

ick

ne

ss

(in

/g)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 52

4

6

8

10

12

14

16x 10

-4

Input Pressure (psig)

Ice

Th

ick

ne

ss

(in

/g)

Prototype 2

Prototype 3

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 25

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 26

Cap Section

Spring steel

8 ft.

1 ft.

Full Scale Blade Modifications

• Prototype II selected for full scale testing

• Installed on outboard 8 ft. section (0.6R-tip)

• Input pressure provided entirely from centrifugal pumping

• Hall sensor used to monitor cap deflection

De-icing system

installed at blade tip

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 27

Agenda

• Background and Motivation

• Objectives

• Prototype Designs

• Rotor Ice Testing Results

• Full Scale Blade Modifications

• Full Scale Testing Results

• Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 28

Icing Cloud Generator

• NASA Standard icing nozzles

produce an icing cloud

• Water droplet size controlled via input

air and water pressures

• Controllable within FAR 25/29 icing

envelop

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 29

Full Scale Icing Test - Icing Cloud

Icing cloud generator:

• Droplet size controlled via

atomizing nozzles

• Low LWC

High pressure water nozzles:

• Large, uncontrolled droplet size

(assumed 200µm)

• LWC=0.6 g/m3

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 30

Full Scale Icing Test Method

0 5 10 15 20 25 304

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

Time (sec)

Vo

lta

ge

Maintain rotor

speed

Spool up rotor RPM

Icing cloud ON,

accrete ice to blades

Icing time has elapsed

Deicing system ON,

cycle at 0.07 Hz

Icing cloud OFF

Deicing time has

elapsed, deicing

system OFF

Spool down rotor

Deicing system OFF

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 31

Full Scale Icing Test Results

No

Pneumatic

De-Icing

Centrifugally

Powered

Pneumatic De-

Icing

• Successful shedding of 8

ft. tip region (270 RPM)

• Max ice thickness of 0.08

in. successfully shed

• Temperatures from -

10°C to -15°C tested

• Low power consumption

(~1 W)

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 32

1. Full-scale centrifugally powered pneumatic de-icing tested on a full-scale rotor blade

2. The de-icing system consumes virtually no power (~1 W)

3. Capability of centrifugal forces to create pneumatic pressures to debond ice demonstrated

4. De-icing system weight is comparable to that of existing erosion caps.

5. Minimum ice thickness is a fraction of that required by electro-thermal systems (32% of typical electrothermal ice accretion)

Conclusions

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 33

Questions?

September 30, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 34