Ratio Of Orifice Research Articles

Cavitation indices for high pressure orifice plate energy dissipators

A problem of providing a simple device for pressure dissipation in mine underground high pressure water reticulation systems was investigated; a required feature of this device was operation without cavitation. An orifice plate was selected, and various orifice diameter ratios (0.206–0.444) for a range of upstream pressures (2000–7000 kPa) were examined for their incipient cavitation points and flow/pressure drop behaviour. Experimental work was conducted in two parts, low pressure and high pressure; the low pressure part of the work was carried out at the University of the Witwatersrand and the high pressure part at the East Driefontein Gold Mine. Both sets of experiments yielded data that were inconsistent with previously predicted values of incipient cavitation under conditions of relatively low head (up to 137 m of water); analysis of the results yielded a new simple cavitation prediction method based on cavitation inception and orifice pressure drop data which is easily presented in graphical form. The results showed that upstream pressure affected the pressure drop required for incipient cavitation, for the same orifice size; and that the orifice ratio affected the pressure drop required for incipient cavitation, for the same upstream pressure.

Two-dimensional focusing of a supersonic free jet by a rectangular orifice

Supersonic free jets issuing from rectangular orifices have been observed by using a laser-induced fluorescence technique. Anisotropy of expansion in two directions, the orifice length (z) and width (y), apparently occurs in the jet structure at a large pressure ratio (between reservoir and vacuum chambers); the jet spreads in the y direction whereas it converges in the z direction. This effect is enhanced by interaction of lateral shocks from both ends of the orifice when a small aspect ratio orifice is used. Under a flow condition whereby the shocks reflect normally on the axis, the jet becomes very thin in the z direction.

The flame structure and vorticity generated by a chemically reactingtransverse jet

An analytical model describing the behavior of a turbulent fuel jet injected normally into a cross flow is developed. The model places particular emphasis on the contrarotating vortex pair associated with the jet, and predicts the flame length and shape based on entrainment of the oxidizer by the fuel jet. Effects of buoyancy and density variations in the flame are neglected in order to isolate the effects of large-scale mixing. The results are compared with a simulation of the transverse reacting jet in a liquid (acid-base) system. For a wide range of ratios of the cross flow to jet velocity, the model predicts flame length quite well. In particular, the observed transitional behavior in the flame length between cross-flow velocity to jet velocity of orifice ratios of 0.0 to 0.1, yielding an approximate minimum at the ratio 0.05, is reproduced very clearly by the present model. The transformation in flow structure that accounts for this minimum arises from the differing components of vorticity dominant in the near-field and far-field regions of the jet.

A study on characteristic of pressure reduction of compressed air in a long pipe. (2nd report A numerical analysis)

In this paper, equations of the one-dimensional, unsteady and compressible flow are transformed into characteristic equations to analyze the flow in a long pipe, and the characteristics of the pressure reduction in a long pipe is investigated numerically by the method of characteristics. The calculations are performed for pipes which have four kinds of bore, three lengths and five orifice ratios, and are compared with the experimental results. It was shown that the calculated results agree with the experimental results qualitatively well and that the characteristic method is available to analyze the flow in a long pipe.

Theoretical and experimental investigations on the formation of air core in a swirl spray atomizing nozzle

Theoretical and experimental studies have been made to investigate the variations of air core diameter, the most important hydrodynamic picture inside a swirl nozzle, with the pertinent guiding parameters like injection condition expressed as the Reynolds number at inlet to the nozzle and the geometrical dimensions of the nozzle, namely, the length and diameter of the swirl chamber, angle of spin chamber and the orifice diameter. The theoretical relations have been established through an approximated analytical solution of the hydrodynamics of flow of a viscous incompressible fluid in a swirl nozzle. A series of experiments have been carried out to support and compare the theoretical results. Finally, it has been recognized that for any nozzle, the air core diameter becomes a direct function of Reynolds number Re i at inlet to the nozzle only at its lower range and then remains constant. Amongst the nozzle geometrics, the ratio of orifice to swirl chamber diameter D 2/D 1 has got the most predominant effect on the air core diameter. An increase in the ratio of orifice to swirl chamber diameter D 2/D 1, and in the spin chamber angle 2α and a decrease in the swirl chamber length to diameter ratio L 1/D 1 increase the ratio of air core to orifice diameter and vice versa.

Comments on a ‘new method for sticking probability and coverage determination on crystal surfaces’

The determination of sticking probability by the method suggested in the recent paper by Morris and King 1 involves a calculated geometrical factor f describing the transmission probability between a small surface element to a rectangular crystal surface, coaxial with its centre and lying in a parallel plane. In this work a correction to their factor f is derived. The new values of f give closer agreement between the measured results reported and those obtained earlier by another method. An improved procedure is proposed here based on the direct transmission probability between two coaxial disc surfaces in parallel planes. One may optimise the new arrangement taking measurement sensitivity and response time into account. This could be achieved with an almost equal diameter, relatively large, but closely spaced disc configuration. It is shown that in this case a more general expression needs to be employed to evaluate the sticking probability from the measured pressures and geometric factors. This is reduced to the earlier expression 1 when the ratio of orifice to crystal area becomes sufficiently small.

St. Jude Medical cardiac valve prosthesis: In vitro studies

The St. Jude Medical cardiac valve prosthesis is an all-pyrolitic carbon, bileaflet, low profile, central flow device. Prior to clinical use on intensive program of in vitro and in vivo testing was undertaken. Simulated radiographic studies determined that the tungsten impregnation needed to make the valve leaflets radiopaque was 0.013 inch. Steady-state flow and pulse duplicator studies demonstrated a high ratio of flow orifice to tissue anulus diameter with low transvalvular pressure gradients. Regurgitation was found to be acceptable. Flow visualization revealed central flow through all three flow orifices with minimal turbulence and vorticeal current formation. In vitro comparison with other available cardiac valve devices of various sizes demonstrated superior hemodynamic performance of the St. Jude Medical cardiac valve.

Experimental Study of the Effects of Orifice Plate Eccentricity on Flow Coefficients

An experimental program was undertaken to evaluate orifice flow coefficient variations with changes in plate concentricity. The tests were conducted on four Beta ratio orifice plates, ranging from 0.4 to 0.7, mounted in a special flange tap test fixture in a four-inch water line. The results are presented as the percent variation in flow coefficient, from the centered value, for a given eccentricity in an X, Y coordinate system in the plane of the orifice plate. The results indicate that the change in flow coefficient is a function of the magnitude and direction of the eccentricity and the Beta ratio. The coefficients were higher than the centered value independent of orifice center motion with an X, Y coordinate system. The relationship of these results to the concentricity specifications of existing codes and available literature is also presented.

Profiles for Low Reynolds Number Flows

The characteristics of the orifice meter are well known and have been thoroughly explored by a number of investigators over a considerable range of Reynolds numbers, yet the low Reynolds number range—i.e. below ( Re D = 4000, where ( Re) D is the upstream pipe Reynolds number, has received comparatively little attention, although recent work by two of the authors has supplemented the available data substantially. This work concentrates on very accurate measurements with small diameter orifices, but where less exacting standards of metering accuracy, e.g. ±2-2 1/2 per cent, can be allowed, a closer analysis reveals that there is a choice of orifice profiles which can be used successfully. Consideration is also given to the recommendations of the various standardizing bodies for the allowable tolerances in the diameter of the pipeline in which the orifice meter is situated. These tolerances are often unnecessarily severe and a ‘tolerance number’ depending upon discharge coefficient and the area ratio of orifice to pipe is suggested.

Experimental Evaluation of Expansion Factors for Steam

Abstract The empirical expansion factor for the orifice-metering of compressible fluids is based largely on tests of natural gas and air. This paper presents data on superheated steam for orifice ratios from 0.30 to 0.82, superheats from 29 to 255 F, and pressures of 44 to 102 psia. Expansion factors obtained were in close agreement with those of natural gas and air.

空氣マイクロメータを利用した觸針式仕上面檢査機の試作

The attempts to utilize the pneumatic micrometer as a magnifying device for measurement of surface roughness have been made by some researchers. But there are some other problems in that field yet left untouched. Here we studied about the response phenomenon of the manometer reading due to a "step" or "sinusoidal" displacement at the delivery orifice to find the dynamic character of pneumatic micrometer.From the results obtained, the fundamental conditions of measurements were determined and a tracer method surface tester with a pneumatic micrometer was constructed.The magnification of this instrument can be set for any desired value by adjusting the length of water-column or the ratio of orifice and it was not difficult to get vertical magnification of 50, 000 times, but considering the radius of curvature of the extreme point of tracing needle or the measuring pressure the magnification was determined 4, 000 times in vertical and 88 times in longitudinal. These values are sufficient for the measurement of surface roughness from 1S to 4S.The profile curves gained in this way show very actual feeling (as to be seen in the figure) and repeating character and accuracy are never worse than those of "Nippon Kogaku Surface Tester".

Orifice Coefficients — Data and Results of Tests

Abstract This paper discusses the results of experimental work conducted at the Research Laboratory of the Republic Flow Meters Co., of Chicago, on the use of orifice plates for measuring the flow of fluids in pipes. Extensive tests were carried on for a period of several years to determine the effect of the varying factors such as the orifice ratio, the size of the pipe, and the distance of the upstream and downstream connections upon the pressure difference across the orifice plate. The tests were conducted on seven sizes of pipes, from 2-in. to 12-in. standard. Fourteen orifice ratios were used in each size and twelve connections were tested on each side of the orifice plate. The tests were made on the flow of atmospheric air, supplied by a Sturtevant blower having a maximum capacity of 6000 cu. ft. per min., at a pressure of 10 in. of water. The air passing through the orifice was measured by five calibrated impact tubes ranging from 1 in. to 4 in. in internal diameter. A detailed account is given of the calibration of the impact tubes, and curves were plotted showing the coefficient as a function of the impact head through the tube. The arrangement of the installation for the final tests is described and illustrated in detail, and an account is given of the method of testing the various orifices. The theoretical relation of the functions is given briefly, preceded by elaborate definitions of the terms involved. The paper includes a number of tables and a collection of characteristic curves that may be employed for determining the flow through orifice plates in a given size of pipe.