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Title: On the measurement and modelling of high pressure flows in poppet valves under steady-state and transient conditions
Authors: Mohr, Stephan
Clarke, Henry
Garner, Colin P.
Rebelo, Neville
Williams, Andrew M.
Zhao, Huayong
Keywords: Poppet valve
Transient valve flow coefficient
Indexed piston
Womersley number
Issue Date: 2017
Publisher: © American Society of Mechanical Engineers (ASME)
Citation: MOHR, S. ... et al., 2017. On the measurement and modelling of high pressure flows in poppet valves under steady-state and transient conditions. Journal of Fluids Engineering, 139 (7), 071104, Paper No: FE-16-1635
Abstract: 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 whilst maintaining realistic in-cylinder transient pressure profiles by simply using a fixed area outlet orifice. A one-dimensional modelling 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 steadystate 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: 1. For a given valve lift, the steady-state flow coefficients fall by up to 21 percent with increasing cylinder/manifold pressure ratios within the measured range given above; 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.
Description: This paper is closed access until 7th March 2018.
Sponsor: This project was partially funded by Innovate UK (Project no.: 101561).
Version: Accepted for publication
DOI: 10.1115/1.4036150
URI: https://dspace.lboro.ac.uk/2134/24041
Publisher Link: http://dx.doi.org/10.1115/1.4036150
ISSN: 1528-901X
Appears in Collections:Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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