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Numerical simulation of unsteady interaction of hot

streams with HPT rotor blades using harmonic

balance method

A.I. Iakunin, N.B. Kuznetcov, N.N. Kortikov ,A.E.Tcvetaev

Klimov JSC, St. Petersburg, Russia

Theoretical Foundations of Thermotechnics Department,

St. Petersburg State Polytechnical University, Russia

LaGraff, J. E., Ashpis, D. E., Oldfield, M. L. G. & Gostelow, J. P. (2006).

Unsteady flows in turbomachinery, NASA/CP-2006-214484.

Frequency-length scales of unsteady

phenomena in turbomachinery

1

The main generating factors of unsteady flows

Hot streaks Unsteady rotor-stator

interaction

2

NUMERICAL METHODS OF ROTOR-STATOR

INTERACTION

3

Transient Rotor/Stator (TRS) Method

(Moving Rotor - STAR CCM+)

THE IMPLICIT UNSTEADY

SOLVER WITH COUPLED FLOW

AND COUPLED ENERGY MODELS

(5-20 inner iterations in each

time step).

SOLVE FULL 360 DEGREES OR

EQUAL SECTOR FOR BLADE

ROWS.

TYPE OF CONNECTION ON THE

INTERFACES - IN-PLACE OR

REPEATING TOPOLOGY.

CONVERGENCE OF TIME DOMAIN

SOLVER PERIODIC BEHAVIOR OF

SOLUTION IS ACHIEVED

COMPUTATIONAL MESH FOR THE TIME

DOMAIN SIMULATION OF THE 36-42-36

(equal sector 60 degrees 6-7-6)

4

Harmonic Balance Method

Solution function W is periodic in time

and represents by the Fourier series:

M is the number of modes or harmonics

-Non-reflecting, far field boundary

conditions

Single passage in each row and

complex periodicity conditions

5

)mtiexp()r( M

Mm mW)t,r(W

N

kT tk

1M2N - number of time levels

k-th discrete time level

Z

ji 1i

ijii

j

Bm

Frequencies for blade row j

)tkmiexp()tk,r( 1N

0k k W

N

1 )r(Wm

*

Merits and demerits of HB and TRS methods

HB TRS

Turbulence model Spalart-Allmares, k-e Any

Thermophysical properties Constant Variable

Conjugate problem Non available Available

Frequency spectrum Discrete Continuous

Number of solvable equations Depends on the number of

modes

Constant

Time step Time step is not used as the

problem is a steady one

Depends on the type of the

problem and the dimension of

the grid

Computational grid volume One blade passage is used Depends on the number of

blades in rows

Volume of stored and processes

data

Only average values of

variables and Fourier

coefficients are stored

Depends on the number of

recorded time steps and the

number of analyzed variables. It

is difficult to obtain average

values

6

Experimental setup (gas turbine)

SCHEMATIC OF EXPERIMENTAL FACILITY PHOTOGRAPH OF EXPERIMENTAL SETUP

7

TURBINE STAGE SUPPORT OF THE

TURBINE ROTOR

HYDRAULIC

BRAKE

Re2=3.710 5 M2=0.464

Basic parameters for physical modeling

SECTION D m

g1 m

g2 m

c1 m

C2 m

1 DEGREES

1 DEGREES

2 DEGREES

BOTTOM 0.36 0.0471 0.0269 0.078 0.035 25010’ 34016’ 36030’

MID - SPAN 0.43 0.0562 0.0322 0.078 0.037 26020’ 58025’ 34032’

TOP 0.50 0.0654 0.0374 0.078 0.043 28020’ 94050’ 30016’

Z S =24

Z R =48

Re2=3.710 5

Mw2=0.464

=5000 rpm

FLOW SCHEME AND MEASUREMENT LOCATIONS IN THE

TURBINE STAGE

8

Measurement results of instant velocity behind NGV

9

Measurement results of instant velocity

behind wheel in three sections

10

Mesh = 1.3 million Hex cells

Y

+

= 1.0 16.

CFL number = 5.0

Time step for TRS = 5*10 -5

s

Numerical simulation: computational grid

11

Harmonic balance solution

residuals for a five modes trial

Periodic behavior of velocity -

TRS solver model

Convergence history

12

Fourier mode 0 on the stator

(a)

COMPUTATIONAL RESULTS

0-fourier mode

13

Comparing of experimental and numerical results

position No.28

14

Role of turbulence level in prediction of

instant velocity

15

Pressure and temperature amplitude-frequency characteristics

Stator Rotor

4000 Hz 2000 Hz

8000 Hz 4000 Hz

12000 Hz 6000 Hz

16000 Hz 8000 Hz

20000 Hz 10000 Hz

5 mode

16

Press. Point 1 3180

Temper. Point 1 0.0011

Temper. Point 2 0.0011

Velocity Point 3 0.0278

Velocity Point 4 0.0111

Maximum Power Spectral Density

17

18

Boundary conditions for non-uniformity total

temperature at NGV inlet

T*max/T*aver.=2.16

19

TRS calculation results : Blade temperature in monitoring points

20

TRS calculation results : Temperature AFC

21

Temper. Point 1 6.28

Temper. Point 2 20.3

Stator Rotor

4000 Hz 2000 Hz

8000 Hz 4000 Hz

12000 Hz 6000 Hz

3 mode

Maximum Power Spectral Density

HB and TRS calculation results

22

HB and TRS calculation results

23

HB and TRS calculation results

24

HB and TRS calculation Results

25

HB and TRS calculation results

26

HB and Mixing Plane calculation results

27

HB and Mixing Plane calculation results

28

Calculation results : T* behind NGV

29

Calculation results

30

Conclusions

• During calculation of unsteady time and space periodic gas flows in

turbomachines the HB method is considerably more effective in terms of the

calculation costs in comparison with TRS method;

• Comparison of the calculation results with the experimental data has shown a

good match for both methods excluding the interaction of the NGV wake with

the rotor wheel at the turbine outlet;

• Calculations of effect of the circular temperature non-uniformity on the

temperature of the rotor blades have proved a possibility of use of the HB

method for the engineering analyses with a possible inaccuracy of up to 8-9%;

• Similar match of the calculation results using HB and TRS methods permits to

use effectively the HB method for optimization calculations.

31

Thank you very much

for your attention

TRS method

32

HB method

TRS calculations results

Velocity Flow lines

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