LOW SPEED vs HIGH SPEED TESTING OF LP TURBINE BLADE WAKE

INTERACTION

M.Vera and H.P.HodsonWhittle Laboratory

University of CambridgeU.K.

Sponsored by ITP

Contents

Introduction

High speed vs. Low speed

Facilities

Results

Conclusions

Introduction

• Experiments simulating blade wake interaction at high Mach numbers are needed

BUT

• Only IF they are worth it

This seminar presents

• Techniques for testing of low and high speed LPT cascades

• The extent to which results from low speed are meaningful

High speed vs. low speed

200mm50mmChord

rrStream tube divergence

üüExit angle

rüMach number

üüReynolds number

Low speedHigh speed

60Hz3KHzBar passing frequency

2mm0.4mmBar diameter

Choosing the size

Chord

PitchVexit

Vinlet

αinlet

TURBOMACHINE

Pitch ratio

Yp

F

φ

Ubar

fbar

β

Pitchbar

dbar

FEEDBACK FEEDBACK

CASCADE

Determination of bar losses

Stagnation pressure across the bar row changes due to

• Losses due to the drag of the bars

• Work input

Mixed out conditions downstream the bars are needed

β0

β1

βmD

xy

S

P00, Ps0, T00P01, Ps1, T01

D=d•Cd•(P00-Ps0)

1/2•?•W2 Low speed

High speed

Frame of reference fixed to the bars

Calculation procedure

Determination of bar losses

Red

0.0

0.4

0.8

1.2

1.6

1200 1550 1900 2250 2600

Ma0=0.50Ma0=0.58Ma0=0.63

U/U50%

(P00-P01)/(P01-Ps1)Cd

•A good estimation of Cd is needed

•The calculation procedure is validated

0.00

0.02

0.04

0.06

0.08

0.950 0.975 1.000 1.025 1.050

Experimental data

Numerical procedureCalculated data

Facilities•Variable wake passing frequency

•Variable inlet flow coefficient

•Variable wake strength

•Variable incidence

High SpeedLow Speed

Facilities. High speed rotating bar rig

Results

Reexit x 105

LossesLow speed: Yp

High speed: KSI

0

0.01

0.02

0.03

0.04

0.00 1.00 2.00 3.00 4.00

Low speed-Steady High speed-Steady Low speed-Unsteady High speed-Unsteady

0.5

1.0

1.5

2.0

0.0

Results

Non-dimensional ensemble averaged quasi shear stress Ma=Madesign, Re=0.65Redesign

Bar passing periodMa/Madesign

KSI/KSIdesign

•Independency of Mach number below the transonic range

•Existence of becalmed region following the wake induced path

High lift, high turning profile

0

1

0.7 1.0 1.30.43 0.62 0.80

Conclusions

High speed testing presents greater challenges.

At all speeds below transonic:

• Same quantitative results are obtained for loss

• Same wake interaction phenomena are found

Low speed approach is valid below the transonic range

and it is EASIER

ACKNOLEDGEMENTS:ITP for the funding and the permission to publish this work