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Research Papers: Fundamental Issues and Canonical Flows

The Parametric Modeling of Local Resistance and Pressure Drop in a Rotary Ball Valve

[+] Author and Article Information
Dan Wang

State Key Laboratory for Strength
and Vibration of Mechanical Structures,
School of Aerospace,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: wd862570137@163.com

Changqing Bai

State Key Laboratory for Strength
and Vibration of Mechanical Structures,
School of Aerospace,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: baichq@mail.xjtu.edu.cn

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received April 12, 2017; final manuscript received September 2, 2017; published online October 19, 2017. Assoc. Editor: Daniel Livescu.

J. Fluids Eng 140(3), 031204 (Oct 19, 2017) (11 pages) Paper No: FE-17-1224; doi: 10.1115/1.4037946 History: Received April 12, 2017; Revised September 02, 2017

In this paper, a theoretical study of ball valves is carried out for investigating the local resistance and pressure drop of ball valves in operating process. An equivalent model of ball valves is proposed based on the inherent mechanism of the resistance loss, which can be divided into three equivalent throttling components: a thick orifice, two variable-opening eccentric orifice plates, and a Z type elbow. Through analysis of the flow resistance of the three components, a general parametric modeling of ball valves is presented for the flow resistance analysis, and then an analytical formula of pressure drop is demonstrated. The results obtained from the presented model are compared with the prior test data to validate this model, and good agreement is observed. Indicate that the presented model has high accuracy in predicting the resistance and pressure loss in various openings. The results show that the influences of thin orifice plates play an important role in the total flow resistance coefficient and pressure drop, especially in the small opening. The effects of thick orifice plates and the Z type elbow gradually increased as the valve opening rises and becomes significant when the opening is more than 70%.

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References

Figures

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Fig. 1

Orifice area of ball valves: (a) longitudinal section of a ball valve and its coordinate system and (b) projection of orifice area on x–y plane

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Fig. 2

Variety of the orifice projected area with increasing opening (the shaded area indicates the flow area, and the unshaded area is the valve spool)

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Fig. 3

Top view of valve flow channel

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Fig. 4

Equivalent model of a ball valve

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Fig. 5

Three types of throttling elements

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Fig. 6

Orifice plates [29]: (a) thin orifice plate and (b) thick orifice plate

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Fig. 8

Elbows: (a) Z type elbow, (b) elbow, and (c) bending elbow

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Fig. 10

The relationship of flow area and valve rotational angel

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Fig. 9

The relationship of flow area and valve opening

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Fig. 11

Comparison of resistance coefficients obtained from the presented model and the results in Ref. [42]

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Fig. 12

Comparison of resistance coefficients obtained from the presented model and the results in Ref. [43]

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Fig. 13

Comparison of ξ1, ξ2, ξ3, and μ of DN50 ball valve

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Fig. 14

Comparison of ξ1, ξ2, ξ3, and μ of DN75 ball valve

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Fig. 15

Comparison of the pressure drop obtained from presented model and the results in Ref. [42]

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Fig. 16

Comparison of resistance coefficients obtained from the presented model and the experimental data under cavitation in Ref. [44]

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Fig. 17

SMFP⌢ and SMEP⌢ : (a) SMFP⌢ and (b) SMEP⌢

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