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Research Papers: Flows in Complex Systems

On the Measurement and Modeling of High-Pressure Flows in Poppet Valves Under Steady-State and Transient Conditions

[+] Author and Article Information
Stephan Mohr

Wolfson School of Mechanical, Electrical
and Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK
e-mail: S.Mohr@lboro.ac.uk

Henry Clarke

Dearman Technology Centre,
Unit 5 Stafford Cross Business Park,
Stafford Road,
Croydon, Greater London CR0 4TU, UK
e-mail: Henry.Clarke@Dearman.co.uk

Colin P. Garner

Wolfson School of Mechanical, Electrical and
Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK
e-mail: C.P.Garner@lboro.ac.uk

Neville Rebelo

Wolfson School of Mechanical, Electrical
and Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK
e-mail: N.J.Rebelo@lboro.ac.uk

Andrew M. Williams

Wolfson School of Mechanical, Electrical and
Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK
e-mail: A.M.Williams@lboro.ac.uk

Huayong Zhao

Wolfson School of Mechanical, Electrical and
Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK
e-mail: H.Zhao2@lboro.ac.uk

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 28, 2016; final manuscript received January 12, 2017; published online April 24, 2017. Assoc. Editor: Mark R. Duignan.

J. Fluids Eng 139(7), 071104 (Apr 24, 2017) (8 pages) Paper No: FE-16-1635; doi: 10.1115/1.4036150 History: Received September 28, 2016; Revised January 12, 2017

Flow coefficients of intake valves and port combinations were determined experimentally for a compressed nitrogen engine under steady-state and dynamic flow conditions for inlet pressures up to 3.2 MPa. Variable valve timing was combined with an indexed parked piston cylinder unit for testing valve flows at different cylinder volumes while maintaining realistic in-cylinder transient pressure profiles by simply using a fixed area outlet orifice. A one-dimensional modeling approach describing three-dimensional valve flow characteristics has been developed by the use of variable flow coefficients that take into account the propagation of flow jets and their boundaries as a function of downstream/upstream pressure ratios. The results obtained for the dynamic flow cases were compared with steady-state results for the cylinder to inlet port pressure ratios ranges from 0.18 to 0.83. The deviation of flow coefficients for both cases is discussed using pulsatile flow theory. The key findings include the followings: (1) for a given valve lift, the steady-state flow coefficients fall by up to 21% with increasing cylinder/manifold pressure ratios within the measured range given above and (2) transient flow coefficients deviated from those measured for the steady-state flow as the valve lift increases beyond a critical value of approximately 0.5 mm. The deviation can be due to the insufficient time of the development of steady-state boundary layers, which can be quantified by the instantaneous Womersley number defined by using the transient hydraulic diameter. We show that it is possible to predict deviations of the transient valve flow from the steady-state measurements alone.

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Figures

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Fig. 1

Schematic of the pneumatic valve flow models for a piston-expander and an indexed piston

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Fig. 2

Schematic of the dynamic valve flow rig used

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Fig. 3

Sketch for the calculation of the geometrical valve area at different lift (L)

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Fig. 4

Comparison between the modeled pressure traces used to calculate the transient flow coefficients and the measured pressure traces for all transient flow conditions

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Fig. 5

Steady-state nitrogen valve flow results with an open cylinder configuration

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Fig. 6

Valve flow as a function of cylinder/manifold pressure ratio. Top: the effective and geometrical inlet valve area at a valve lift of 0.5 mm. Bottom: the flow coefficient as a function of pressure ratio for an inlet valve lift of 0.5 mm for steady-state and transient flow. The solid black line is Perry's polynomial with a scaling factor of 0.456. The vertical dashed line represents the critical pressure ratio.

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Fig. 7

Left steady-state nitrogen valve flow coefficients (for choked conditions) compared with the transient flow coefficients (at pressure ratio zero) derived from fitting modified Perry polynomials to the experimental results for three cylinder volumes (declining flow coefficient with increasing pressure ratio) at comparable valve lifts (right). The vertical dashed line represents the critical pressure ratio.

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Fig. 8

Ratio of the measured steady-state and transient flow coefficients as a function of Womersley number

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Fig. 9

Comparison of modeled and measured maximal cylinder pressure and average mass flow rate for three different nitrogen inlet pressures. The exhaust valve lift is held constant for all three test points.

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Fig. 10

Comparison of the measured (bottom) and modeled (center) pressures in the manifold (solid line) and the cylinder (broken line) for two different cylinder volumes. The inlet valve lift is shown on top.

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