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Port, Valve, Intake, and Exhaust System Design
Published in John B. Heywood, Eran Sher, The Two-Stroke Cycle Engine, 2017
The value of CD and the choice of reference area are linked together: their product CDAR is the effective flow area of the valve and port assembly AE. The discharge coefficient of a port is, in effect, the ratio between the actual mass flow rate through the port and the theoretical mass flow rate assuming an isentropic expansion. Figure 5-20 shows how, for a simple radial port, the discharge coefficient depends on the pressure ratio across the port and the port open fraction. The discharge coefficient varies significantly with pressure ratio. The effect of the port open fraction depends on the port geometric details. The effects of scavenge port open fraction and port geometry on coefficient of discharge for square and circular ports, with sharp and rounded entries, are shown in Fig. 5-21. Geometry effects are most significant at the larger open fractions.
Physical similarity and dimensional analysis
Published in Bernard S. Massey, John Ward-Smith, Mechanics of Fluids, 2018
Bernard S. Massey, John Ward-Smith
The discharge coefficient is an important dimensionless parameter that relates the flow rate through a differential-pressure flow-metering device, such as an orifice plate, nozzle or Venturi tube, to the pressure distribution the flow generates. It was first introduced in Chapter 3, where it was used to adjust theoretical values of mass flow rate (or volumetric flow rate), derived from simplistic mathematical models of fluid motion that ignored the effects of viscosity, to yield improved comparisons with the behaviour of real flows. The method of dimensional analysis provides a more rigorous justification for the use of the discharge coefficient, since, from the outset, the analysis takes full account of the viscous nature of real fluids.
Flow in Atomizers
Published in Arthur H. Lefebvre, Vincent G. McDonell, Atomization and Sprays, 2017
Arthur H. Lefebvre, Vincent G. McDonell
The result from Figure 5.10 implies a few interesting features that were mentioned at the beginning of this section. First, the discharge coefficient does not depend on downstream pressure. Furthermore, it only depends on upstream pressure. It is no longer a function of Reynolds number. Hence, the discharge coefficient behavior is indeed much different than it is for noncavitating conditions.
Morphology and formation of crystalline leucine microparticles from a co-solvent system using multi-orifice monodisperse spray drying
Published in Aerosol Science and Technology, 2021
Zheng Wang, Mani Ordoubadi, Hui Wang, Reinhard Vehring
The powder production rate for monodisperse spray drying using a single-orifice plate, was estimated as (Ivey et al. 2018) where is the solids concentration of the feed solution, is the discharge coefficient of the orifice, is the orifice diameter (assuming a circular orifice), is the pressure difference across the orifice and is the liquid density. The discharge coefficient, is defined as the ratio of the actual or experimental flow rate to the theoretical flow rate. The discharge coefficient does not change significantly during atomization (assuming no clogging occurs) and varies only with different orifice geometry (Bayvel and Orzechowski 1993); thus it can be considered close to a constant for orifices with the same geometry. For example, the discharge coefficient is typically in the range of 0.7-0.8 for the circular orifice used in the vibrating orifice atomizer.
An orifice shape-based reduced order model of patient-specific mitral valve regurgitation
Published in Engineering Applications of Computational Fluid Mechanics, 2021
J. Franz, K. Czechowicz, I. Waechter-Stehle, F. Hellmeier, F. Razafindrazaka, M. Kelm, J. Kempfert, A. Meyer, G. Archer, J. Weese, R. Hose, T. Kuehne, L. Goubergrits
In general, the discharge coefficient describes the ratio of the actual flow rate to the theoretical flow rate without irreversible losses and it can differ depending on orifice shape (e.g. degree of restriction, edge sharpness and orifice eccentricity) and flow state (i.e. laminar or turbulent) (Abd et al., 2019; Athar et al., 2003; Hollingshead et al., 2011). In the context of heart valves, flow coefficients have been mainly investigated for stenotic mitral and aortic valves, which are characterized by a restrictive opening area and impaired leaflet motion. Empirically found values are for stenotic mitral valves and for stenotic aortic valves (Cohen & Gorlin, 1972; Gorlin & Gorlin, 1951). While it is difficult to study the influence of the valve shape on the flow coefficient in-vivo, experimental in-vitro studies have shown that orifice eccentricity and leaflet shape influence the flow coefficients through (idealized) stenotic mitral and aortic valve geometries (Flachskampf et al., 1990; Gilon et al., 2002). Regurgitant mitral valves show a variety of different morphologies, ranging from more circular to very elongated orifices, including complex 3D shapes with prolapsed or flail leaflets (Buchner et al., 2011). Flow coefficients of regurgitant mitral valve flow can thus be expected to vary depending on the orifice shape, but this has, to our knowledge, not been investigated to date.
Experimental investigation on pressure–leakage relation for high-density polyethylene pipe
Published in Urban Water Journal, 2019
Syed Ali Sadr-Al-Sadati, Mohammadreza Jalili Ghazizadeh
The results of Figure 3 show that the discharge coefficient for the experiments is within the range of (0.72 ≤ Cd ≤ 0.86) which is compatible with Coetzer’s study on orifice leakage (0.7 ≤ Cd ≤ 0.9) for uPVC and HDPE pipes (Coetzer, Van Zyl, and Clayton 2006). Also, the results of Figure 3 suggest that the discharge coefficient is slightly reduced by increasing pressure. Moreover, it can be concluded that for the same pressure, the leakage discharge coefficient in free flow is generally greater than the submerged flow but as the pressure increases, the discharge coefficients for both cases approach to the same value. The results are compatible with other studies (Thomas 1986). Assuming no deformation in leak area, the average discharge coefficient of these experiments is 0.77.