Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
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Effects of Tip-Clearance Flows
Effects of Tip-Clearance Flows
Pages 959-972
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From page 959... ...
A numerical method solving the Reynolds averaged Navier Stokes equations is used to explore various detail features of the tipleakage flows. Calculation results for the cascade provide an assessment for predicting flow past a non-rotating blade passage with zero and 2% chord clearances.
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From page 960... ...
quantitatively compared their predicted tip flow with the measured data at the design tip gap size. The cascade experiments were obtained with a stationary wall so that the gap flows are driven by pressure drop alone, while the pump rotor experiment involves the effects (in the relative frame)
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From page 961... ...
The formation and the transport of the tip-leakage vortex for both cases are then examined in detail in the results section. In particular, we present numerical solutions for two tip gap clearances for both the cascade and the pump rotor.
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From page 962... ...
la, the embedded grid provides a good representation of both the blade leading and trailing edge regions while also providing a smooth grid change from the blade tip to the tip-clearance region. The grid has 95 nodes in the axial direction, 51 nodes from blade to blade, and
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From page 963... ...
In Fig. 3, the blade surface pressure distributions for both the zero and 2% tip gap cases are presented at three span locations, 50%, 85% and 98.5%.
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From page 964... ...
Tip-Gap Flow In the HIREP Rotor As compared to a stationary blade, a rotating pump stage facilitates the gap flow because the blade rotates in the opposite direction to the gap flow, and hence, the casing tends to pump the flow in the tip region and to enhance the gap flow effects. Obviously, the degree of such rotational effects depends on the tip gap height, the RPM, the blade loading and the blade thickness.
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From page 965... ...
For both the predictions and the measurements, the path of the tip-leakage vortex moves radially inward by approximately 1% of the casing radius in the near wake and then levels off at an essentially constant radius from the near wake to the far wake. The sudden change in radial location may relate to the development of the blade passage boundary layer to the free-shear wake flow.
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From page 966... ...
The grid topology used in the tip gap region is an embedded grid approach, which ensures the precise representation of the blade tip geometry and the smooth grid variation from the blade region to the tip clearance region. The tip clearance sizes studied in this paper are 0% and 2~c chord for the cascade, and 0.64%, 1.77% and 3.22% casing radius for the pump rotor.
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From page 967... ...
5. Inoue, M., Kuroumaru, M., and FuLuhara, M., "Behavior of Tip Leakage Flow Behind an Axial Compressor Rotor," ASME Journal of Engineering for Gas Turbines and Power, Vol.
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From page 968... ...
3 Pressure distributions on blade surface 968
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From page 969... ...
(4b) Tip-leakage vortex on suction side o.o -0.2 -0.4 -0.6 -0.8 -1 .0 _ ~ _ _ ,( r 0 ° O _ _ _ ~ STAT]
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From page 970... ...
6 Velocity comparisons along blade passage BETA=29.3, TAU=2% (EXPT)
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From page 971... ...
I O EXPT vx ~ ~ EXPT V' _ ~ALC vx — '..ALC Vl 1 1 1 0.7 0.8 r l rT~p 1 oc 1.0 FiV. 8 fIlilow `elocit~ ~I pump lC'ro EMBEDDED GRID FiV.
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From page 972... ...
0.7 0.6 0.5 Fig. 12 Blade pressure distributions for three clearances ,,°, 04 0.3 0.2 -v.o 0 20 40 60 80 1 00 % CHORD ,, , ,~ /\ EXPr(1 0~SPAN)
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