Research Papers: Design of Energy, Fluid, and Power Handling Systems

Control of Flow Limitation in Flexible Tubes

[+] Author and Article Information
Ruo-Qian Wang

Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: rqwang@mit.edu

Teresa Lin, Pulkit Shamshery

Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139

Amos G. Winter, V

Assistant Professor
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: awinter@mit.edu

1Corresponding author.

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received February 5, 2016; final manuscript received August 28, 2016; published online October 3, 2016. Assoc. Editor: Yu-Tai Lee.

J. Mech. Des 139(1), 013401 (Oct 03, 2016) (8 pages) Paper No: MD-16-1106; doi: 10.1115/1.4034672 History: Received February 05, 2016; Revised August 28, 2016

This paper proposes a new Starling resistor architecture to control flow limitation in flexible tubes by introducing a needle valve to restrict inlet flow. The new architecture is able to separately control the activation pressure and the flow rate: The tube geometry determines the activation pressure and the needle valve determines the flow rate. A series of experiments were performed to quantify the needle valve and the tube geometry's effect on flow limitation. The examined factors include the inner diameter, the length, and the wall thickness. A lumped-parameter model was developed to capture the magnitude and trend of the flow limitation, which was able to satisfactorily predict Starling resistor behavior observed in our experiments.

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Fig. 1

Starling resistor design and behavior: (a) a conventional Starling resistor design; (b) the concept of pressure compensation, where flow rate becomes constant if the driving pressure is beyond an “activation pressure” threshold

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Fig. 2

The experimental setup used in the present study: the modified Starling resistor architecture is enclosed in the dashed line and the pressure chamber is the same as that shown in Fig. 1(a)

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Fig. 3

Characteristic experimental results from a single trial, without averaging: (a) mode 1 (case E with kvn = 21): at low pressure, the flexible tube retains a circular shape (fully open). Oscillation occurs when P ≈ Pa; (b) mode 2 (case C with kvn = 4): the flexible tube retains a circular shape (fully open) at P < Pa, and then steadily collapses as P > Pa until the oscillation starts at a higher pressure (solid line: the pressurizing scenario; dashed line: the depressurizing scenario; and arrows: the direction pressure was varied).

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Fig. 4

The peak-to-peak pressure amplitude at various oscillation frequencies for the case of Fig. 3(a)

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Fig. 5

Sketch of the two types of oscillation discovered in Ref. [19]. (a) Type I: the wall oscillates between two nonaxisymmetric extremes. (b) Type II: the wall performs small-amplitude oscillations about one of the two nonaxisymmetric extremes.

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Fig. 6

The effect of the needle valve on flow limitation: (a) the pressure drop coefficient kv with different valve openings and flow rates; (b) the effect of the needle valve openings for case B—a decreased opening corresponded to a low flow rate, but the activation pressure was roughly unchanged (the stopping point indicates a flow cutoff at the highest pressure in the pressurizing scenario and the spike indicates a sudden opening of the flexible tube in the depressurizing scenario)

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Fig. 7

The effect of tube geometry on flow limitation: (a) the effect of the tube diameter with kvn = 4; (b) the effect of the wall thickness with kvn = 21

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Fig. 8

The effect of the tube length on flow limitation: (a) the comparison of cases A and B with kvn = 4; (b) the comparison of cases C and D with kvn = 21

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Fig. 9

An example of the relationship expressed by Eq. (10) with n = 3/2

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Fig. 10

Comparison of experimental results with theory: (a) the comparison of activation pressure (dashed line: the prediction by Eq. (11)); (b) the comparison of limited flow rates (solid lines: experimental results; dashed line: the prediction by Eq. (13) with A0/Av = 1 to compare with cases A, B, E, and F; and dotted-dashed line: the prediction by Eq. (13) with A0/Av = 4 to compare with cases C and D)




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