Pitchwise distributions of ensemble average velocites · 2003. 4. 18. · FEM for Turbomachinery...

FEM for Turbomachinery Flows

Alessandro Corsini, BUTE - 28 November 2000

Corsini and Rispoli Inoue and Kuroumaru free vortex rotor (1984)

Navier-Stokes prediction obtained with XENIOS finiteelement code (1991) - grid 59 × 21 × 31

tip clearance t = 1.8% lc tip clearance t = 1.2% lc

Pitchwise distributions of ensemble average velocites

Trailing vortextrailing vortex

Va/Uc

Vp/Uc

Vr/Uc

PS SS

passage vortex

wake



Corsini and Rispoli Inoue and Kuroumaru free vortex rotor (1984)

Navier-Stokes prediction obtained with XENIOS finiteelement code (1991) - grid 59 × 21 × 31

tip clearance t = 1.8% lc tip clearance t = 1.2% lc

Pitchwise distributions of ensemble average velocites

Leakage vortex

PS SS

Vp/Uc

Va/Uc

Vr/Uc

wake



Corsini and Rispoli Storer and Cumpsty linear cascade (1991)

Navier-Stokes prediction obtained with XENIOS finiteelement code - grid 59 × 21 × 31

Navier-Stokes prediction obtained with Dawes finite volume code(1987) - grid 61 × 25 × 33

tip clearance t = 1.8% lc tip clearance t = 4% lc

Blade surface static pressure distribution (Cp) - pressure side

0.5

0.4

0.3

te le







Blade surface static pressure distribution (Cp) - suction side

-0.6

te le

leakage flow influence







Chordwise distribution of averaged tip leakage flow velocity

Leakage velocity







prediction measurement

Blade surface static pressure distribution (Cp) - pressure side

0.5

0.4 0.3

0



CFD ORIENTED AXIAL FAN DESIGN IMPROVEMENT (1)

• CFD INTER-BLADE FLOW PHYSICS PREDICTION

• Blade lift synthesized by use of “cone couple” model

separate optimization of blade pressure and suction sides

extend the validity of 2D cascade concept

blade tip

Velocity field close to the blade suction side

fraction of chord lenght

Rpredicted streamtracesmodeled streamtraces

Velocity field close to the blade pressure side

fraction of chord lenght

blade tip modeled streamtraces

predicted streamtraces

R



CFD ORIENTED AXIAL FAN DESIGN IMPROVEMENT (2)

• on the basis of computed pitch-averaged flow

force factor is evaluated ( ) ll ct

optimum lc * is defined (Howell, 1942) ⇒ optimum solidity values ( )tl *

lc * ( ) ll ct ( )tl *

SS cone 0.893 1.004 1.124

PS cone 0.591 0.859 1.453

• optimized axial fan rotor geometry with FORWARD SWEPT blades

midspan

hub

casing

**sssssspspsps TLTL ll =>=



SWEPT AXIAL FAN ROTOR

• NON FREE VORTEX DESIGN

• CIRCULAR ARC CAMBERED

PLATE

Unswept bladedrotor

Swept bladed rotor

blade number 12 12hub-to-casing diameter ratio 0.676 0.676tip clearance (percent span) 2 % 2 %flow coefficient Φ 0.50 0.50Ideal total head risecoefficient Ψ

0.70 0.70

hub mid tip hub mid tipblade solidity l / t 1.53 1.24 1.05 1.79 1.23 1.13forward sweep angle, deg 0 0 0 30 30 30stagger angle, deg 47.9 42.2 38.3 56.3 43.1 37.4camber angle, deg 27.4 23.1 19.9 35.4 25.4 20.3



SWEPT AXIAL FAN ROTOR FLOW SURVEY (1)

Pitchwise-averaged flow data for FSW and USW rotors(circles: FSW; squares: USW)

ϕ3a

RR

a) b)

ϕ1a

ψth,FSW

ψth,USW

ψ3




[deg]

[deg]

R

R

FSW

USW

SSPS

ST

W

C

SSPS

ST

W

C

0.60.3

0.2

0.6

0.2

0.3

0.25

Axial flow coefficient behind the rotor

Uc




Fig. 5: Local ideal total head rise coefficientbehind the rotor

0.55

0.8

1.25

[deg]

R

FSW

SSPS

ST

W

C

1.2

0.55

0.8

[deg]

R

USW

SSPS

ST

W

C

Uc

Ideal total head rise coefficientbehind the rotor




[deg]

R

USW

SS

PS

ST

W

C

Uc

[deg]

R

FSW

SS

PS

ST

W

C

Uc

0.08

-0.08

0.06

0.0

0.05

-0.05

radial flow coefficientbehind the rotor



SWEPT AXIAL FAN ROTOR LOADING

R

DF

Diffusion factor profile along the span(circles: FSW; squares: USW)

inpinout w/www)R(DF σ∆ 21 +−=



SWEPT AXIAL FAN ROTOR LOSS BEHAVIOR

[deg]

[deg]

R

R

FSW

USW

SS

PS

SS

PS

0.1

0.6

0.1

0.6

0.7

Loss coefficient distributionat 98% blade chord

Uc

R

∆ω

Loss improvement factor

∆ω(R) = RUSWFSW |ωω −

ω = 2inout0in0 V5.0pp ρ−




streamlines on blade suction side streamlines on blade pressure side

8% pitch from blade pressure side

Pitchwise distributions of ensemble average velocites · 2003. 4. 18. · FEM for Turbomachinery...

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