Discharge coefficient of an orifice jet in cross flow: influence of inlet conditions and optimum velocity ratio

Berger, Sandrine; Gourdain, Nicolas; Bauerheim, Michaël; Devillez, Sébastien

doi:10.2514/6.2019-3497

Cited by 1 publication

(2 citation statements)

References 21 publications

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“…The gas flow through the sampling orifice was interpreted in terms of a jet in cross-flow configuration. Under ambient air conditions, which correspond to the calibration procedure in experimental studies, the discharge coefficient at the orifice was found to be in the range 0.6-1.2 and to pass a maximum at a pressure drop ΔP ≈ 150 Pa, in agreement with previous literature data (Berger et al, 2019). Under the hot (1000 K) conditions met in free-standing dilution tubes, the discharge coefficient dropped to values below 0.4.…”

Section: Discussionsupporting

confidence: 88%

“…where 𝜌 is the fluid density, A orf is the orifice cross-section and C d is the discharge coefficient, which is around 0.7 typically (Borutzky, Barnard, & Thoma, 2002;Lafferty, 1998;Oertel, Prandtl, & Böhle, 2008), but may exceed 1 due to the presence of a cross-flow (Berger, Gourdain, Bauerheim, & Devillez, 2019). Isentropic flow occurs under adiabatic conditions and, for pressure drops ΔP orf < 200 Pa, the adiabatic cooling is expected to be less than 5 K (for diatomic gas) in horizontal flame gas sampling tubes under atmospheric conditions.…”

Section: Orifice Flow Revisitedmentioning

confidence: 99%

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A computational fluid dynamics study of flame gas sampling in horizontal dilution tubes

Mätzing,

Vlavakis,

Trimis

et al. 2022

Flow

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The performance of horizontal dilution tubes is investigated by Reynolds-averaged Navier–Stokes and large-eddy simulations. The flame gas enters the dilution tube through a pinhole. The orifice flow and the dilution process inside the tube are studied. The volume flow through the orifice is shown to be proportional to the square root of the pressure drop. The discharge coefficient is 0.9 ± 0.3 in the cold air (calibration) case and drops to 0.35 under hot (flame) conditions. The resulting dilution ratio is roughly a factor of five below typical literature data. The gas sample remains in the wall boundary layer and the mixing process is not complete at the end of the dilution tube. Turbulence decays rapidly behind the tube inlet, which shifts the flow into the laminar to turbulent transition regime. Turbulence increases significantly in the outlet section which has much smaller pipe cross-sections. Despite its relatively low Reynolds number, the outlet flow to the particle sizer (or to the gas analyzer) is clearly turbulent, and interactions with the wall are probable. The results are in agreement with previous findings from laminar jets in cross-flow. Guidelines for optimization of the sampling conditions are suggested.

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Section: Discussionsupporting

confidence: 88%

Section: Orifice Flow Revisitedmentioning

confidence: 99%