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Research Papers: Flows in Complex Systems

Influence of Stator Blade Geometry on Torque Converter Cavitation

[+] Author and Article Information
Cheng Liu

National Key Laboratory for Vehicular
Transmission,
Beijing Institute of Technology,
Beijing 100081, China
e-mail: liuchengbit@gmail.com

Wei Wei

National Key Laboratory for Vehicular
Transmission,
School of Mechanical Engineering,
Beijing Institute of Technology
Beijing 100081, China
e-mail: weiweibit@bit.edu.cn

Qingdong Yan

National Key Laboratory for Vehicular
Transmission,
School of Mechanical Engineering,
Beijing Institute of Technology,
Beijing 100081, China
e-mail: yanqd@bit.edu.cn

Brian K. Weaver

Rotating Machinery and Controls Laboratory,
Mechanical and Aerospace Engineering
Department,
University of Virginia,
122 Engineer’s Way,
Charlottesville, VA 22904-4746
e-mail: bkw3q@virginia.edu

Houston G. Wood

Rotating Machinery and Controls Laboratory,
Mechanical and Aerospace Engineering
Department,
University of Virginia,
122 Engineer’s Way,
Charlottesville, VA 22904-4746
e-mail: hgw9p@virginia.edu

1The authors contributed equally to the paper.

2Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received April 10, 2017; final manuscript received September 15, 2017; published online November 23, 2017. Assoc. Editor: Devesh Ranjan.

J. Fluids Eng 140(4), 041102 (Nov 23, 2017) (10 pages) Paper No: FE-17-1222; doi: 10.1115/1.4038115 History: Received April 10, 2017; Revised September 15, 2017

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.

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References

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Figures

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Fig. 1

Torque converter schematic diagram

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Fig. 2

Blade profile layout

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Fig. 3

Blade profile under variant leaning angles

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Fig. 4

Periodic CFD model

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Fig. 5

CFD and test hydrodynamic performance comparison (top), error bar for TR (middle), and error bar for capacity constant (bottom) under various operating conditions

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Fig. 6

Stator blade nose shape comparison of bullet nose (solid line) and dull nose (dashed line)

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Fig. 7

Nondimensionalized capacity constant and volume of vapor with more than 0.1 fraction under various σ, derived from the base torque converter CFD models

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Fig. 8

Velocity distributions in the stator flow passage at stall with variant stator blade geometry: (a) φ = 18.056 deg and cnt = 18, (b) φ = 27.084 deg and cnt = 18, and (c) φ = 27.084 deg and cnt = 26 with identical hmax = 2.8 mm

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Fig. 9

Velocity distribution along the stator passage at stall from inlet (0) to outlet (1) with variant stator blade geometry and identical hmax = 2.8 mm

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Fig. 10

Isosurface of 0.1 vapor volume fraction at stall with variant stator blade geometry: (a) φ = 18.056 deg and cnt = 18, (b) φ = 27.084 deg and cnt = 18, and (c) φ = 27.084 deg and cnt = 26 with identical hmax = 2.8 mm

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Fig. 11

Pump and stator blade load at stall from inlet (0) to outlet (1) with identical hmax = 2.8 mm and φ = 27.084 deg: (a) stator blade load when cnt = 18, (b) pump blade load when cnt = 18, (c) stator blade load when cnt = 26, and (d) pump blade load when cnt = 26

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Fig. 12

Cavitation number distribution with varying ΔNPT, i.e., SR

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Fig. 13

Nondimensionalized capacity constant distribution with varying ΔNPT

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Fig. 14

Axial velocity distribution under variant SRs for the stator blade (e) hmax = 4.2 mm, φ = 27.084 deg, and cnt = 26 and (f) hmax=4.2 mm, φ = 27.084 deg, and cnt = 18

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