8. 250 HP Engine for Unmanned Helicopter

7/29/2019 8. 250 HP Engine for Unmanned Helicopter

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250 HP engine for unmanned helicopterwith reduced infrared signature

Advisor - Dr. Boris Glezer

Jessica Yana (aerothermodynamic/ stress specialist)

Yonatan Lobovikov (designer)

Akiva Sharma (combustor/heat exchanger specialist)

GAS TURBINE DESIGN PROJECT
http://en.wikipedia.org/wiki/File:RQ-8A_Fire_Scout.jpg


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Preview

1. Project goals and objectives

2. Component selection

3. Thermodynamic cycle

4. Compressor geometry

5. Turbine geometry

6. Cooling

7. Stress analysis

8. Combustion chamber & heat exchanger

9. Design

10. Competiting products


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Project Goals and Objectives

Overall mission : fly autonomously to the battlefield, provide fighting

troops with ammunition and evacuate wounded to rear hospital

Output power 250HP

Light weight

Simple design

Compact

Low cost

Reduced heat signature

Dusty enironment (low altitude mission)


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Components Selection Compressor

Centrifugal Compressor:

Compact design

Lower weight

Lower cost (size and weight lower)

Higher efficiency

2 stages (Improved efficiency)

1 shaft (more simple - cheaper)


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Components Selection Turbine

Axial Turbine:

suitable for high temperatures

Better efficiency

First two stages drive the compressor

Third (last) stage Provide output power (via gear box)


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Components Selection Hot Section

Spiral Recuperator

Compact

Lightweight

Combustor

Annular combustor

Simple design


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Thermodynamic Cycle - Scheme


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Thermodynamic Cycle - Inputs

Flight conditions

Standard atmosphere

Mach 0.2

Additional parameters selected (hystorical data)

Pressure ratio 9

TIT 1400K

Thermal efficiency 38%

Fuel to air ratio (converged value) 0.015

Cooling air

Stage 1 nozzle & blade 2.3%

Stage 2 blisk1%

Stage 1 blisk2%

Losses & Efficiency

PRESSURE LOSSES

Air intake 3%

Exhaust 5%

Combustion chamber 3.5%

Heat exchanger 5%

EFFICIENCY

Compressor 0.75

Turbine 0.85

HEX effectiveness 0.85

Mechanical losses 1%


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Thermodynamic Cycle - Outputs

0.75kg/s

0.23kg / kW-hr

airm

SFC

St. T(K) PR

Compressor

1 290 2.5

2 400 3.6

Turbine

1 1400 1.44

2 1195 2.5

3 1036 6.85


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Compressor Parameters

First

stage

Second

stage

Mass flow rate [kg/s] 0.75 0.75

Pressure ratio 3.5 2.6

Inlet temperature [K] 290K 400K

efficiency 0.85 0.85

Rotation speed [rpm] 63,000 63,000

Total diameter [mm] 174 144


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Compressor Geometry

First

stage

Second

stage

Total diameter [mm] 174 144

Eye root diameter [mm] 40 40

Eye tip diameter [mm] 154.8 125

Root incidence angle [deg] 27.3 27.3

Tip incidence angle [deg] 7.6 9.4

Impeller channel depth [mm] 23 7


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Turbine Parameters

1st

stage

2nd

stage

Power

turbine

Mass flow rate

[kg/s]0.76 0.76 0.76

Pressure ratio 1.44 2.5 6.85

Inlet temperature

[K]1400 1191 1036

efficiency 0.85 0.85 0.85

Rotation speed

[rpm]63 000 63 000 40 000

Total diameter

[mm]183.1 190.4 245


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Turbine Geometry

1st stage 2nd stage Power turbine

St. Rot. St. Rot. St. Rot.

Total diameter [mm] 183.1 183.1 187 193.8 232 244.5

No. of blades 24 33 26 37 18 32

Mean blade height [mm] 8.1 8.1 9.3 9.6 20 22.2

Blade chord [mm] 16 6.2 17 7.4 40 18

L.E diameter [mm] 0.8 0.8 0.9 0.9 2.0 2.3

root [deg] 10 27 10 21 10.5 54

tip [deg] 10 25 9.5 19 9.5 46

root [deg] 39 48.5 43 48.5 46 51.5

tip [deg] 36 46 40.5 45.5 43 43

Pitch to chord ratio chart

2 /b mN R s

Height to chord ratio:

Stator ~ 2

Rotor ~ 1.3

umber of blades


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Turbine Flow Path

Untwisted blades


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CoolingSwirl cooling method

Metal temperature limit =1250K=950C

1st stage (nozzle and blade) had to be cooled

Cooling air

Stage 1 nozzle & blade 2.3%

Stage 2 blisk1%

Stage 1 blisk2%


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Life Time Prediction - Uncooled Blades

Blade temperature

Stage 2 1076K

age 3 877K

Centrifugal stress (max)

Stage 2 185Mpa

Stage 3 350Mpa

Life time estimation

Critic section at the root

Material Waspalloy

Stage 2: 10 000 hours (SF=1.3)

Stage 3: 20 000 hours (SF=1.3)


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Cooled Blades - Stress

Centrifugal & bending stress

Life time fixed to 10 000 hours

Larson miller chart

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11

Stress[MP

a]

Blade section

Blade Section Stress

Safety Factor

Bending Stress

Centrifugal Stress


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Cooled Stage Temperatures

0

1

2

3

4

5

6

7

8

9

1100 1300 1500

BladeHeight[cm

]

Temperature [K]

Temperature Profile

Metal

Temperature

1D

Gas temperature pattern factor 1.1

Safety margins 30%.

3D


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Airfoil external heat transfer coefficient 12.4 kW/m2K

Cooling effectiveness 28%

cooling flow parameter 0.8

Coolant mass flow rate 2.3%

Cooling


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0

0.02

0.04

0.06

0.08

0.1

0.12

300 500 700 900 1100 1300

Diskradius[m]

Temperature [K]

Blisk metal temperature

stage1

stage 2

stage 3

15

35

55

75

95

0.02 0.04 0.06 0.08 0.1

Stress[MPa]

Radius [m]

Blisk radial stress

stage 1

stage 2

stage 3

Blisk Life Time Prediction

50

100

150

200

250

300

0.02 0.04 0.06 0.08 0.1

Stress[Mpa]

Radius [m]

Blisk tangential stress


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Blisk Life Time Prediction

Critical sction towards the tip

Stage 1 blisk: 42 000 hours (SF=1.5)

Stage 2 blisk: 16 000 hours (SF=1.5)

Stage 3 blisk: 1 560 000 hours (SF=1.5)


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Combustor Design Considerations

Performance Objectives:

High combustion efficiency ~ 99%

Low overall system total pressure loss ~

3%

Stable combustion at all operating

conditions

Minimum size, weight, cost.

Effective hot part cooling

Required TIT met

Proper temperature distribution at the

exit

Low emissions

Relightability


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Design Parameters

34.0)05.0exp(1

ref

L

D

L

q

P

L

LPF

6110.130075.1

3

3

bK

Tair

VoleP

m

016.1* ,*

pr

combustoroutpcombustorpturbi ne

h

TCTITCf

=f/ fstoi= 0.255

%5.3

3

34

P

P

SFC = Fuel Flow / Power Produced

= 0.23 kg/kW-hr


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Dimensions

Combustor Cross sectional area= 0.0055 m2

Radius Liner = 0.003 m

Length of Primary Zone = 0.1048 m

Length of Dilution Zone = 0.0698 m

Total Combustor Length = 0.1746 m

Volume = 0.0061 m3


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Air Distribution

:

Primary Zone Air ~ 24%

Dome Air ~ 5 %

Dilution ~ 28%

Nozzle Air ~ 2 %

Liner Cooling ~ 32%

Turbine Cooling ~ 9%


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Recirculation Zone

6943.2tan)/(1

)/(1

3

22

3

swhub

swhubn

DD

DDS


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Materials & CoolingCombustor Liner - Silicon Nitride

High temperature strength

High oxidation resistance

Low cycle fatigue strength

High cycle fatigue strength

High corrosion resistance

Combustor Housing - Inco 909

Elevated high temperature strength

Low cycle fatigue strength

Thermal Barrier Coating - SN-220

Low emmisivity

Low thermal conductivity

Oxidation resistant

Chemically inert

Resistant to thermal shock

Resistant to wear/erosion


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Heat Exchanger

m26.04

)*(6.2 min U

CNTU

A

)1

1)(log

1

1(

rC

rC

NTU

1

1 1

i o

U

h h

z

i H

kh Nu

H

1.25 0.40.023 Re PrH HNu


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Heat Exchanger - Pressure Drop

f LP gh

2

2L L Vh f

H g

If it is known that for turbulent flow: f = 0.316/Re1/4

For hot gas, pressure drop of 0.245 atm is obtained.

For cold air the pressure loss is 0.003 atm.

hL = frictional head loss [m]


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Engine Design


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Shafts


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1st Stage Compressor

d


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2nd Stage Compressor


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Combustor


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Stage 1


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Stage 1

Turbine

b


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Stage 1 Turbine

d b


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Second & Power Turbines


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H E h


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Heat Exchanger

H E h


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Heat Exchanger

H E h


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Heat Exchanger

F l S


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Fuel System

F l S


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Fuel System


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O ll Fl P th


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Overall Flow Path

Cl


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Clearances

Seals


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Seals

M ti


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Mountings

Competing products


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Competing productsPower plant of Northrop Grumman UAV helicopter : Roll Royce 250

RR300 designed for light helicopter and general aviation aircraft Optimized in the 240-300

HP power range

Competing products


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Competing products


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8. 250 HP Engine for Unmanned Helicopter

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