Cylindrical Orifice Research Articles

Experimental investigation of nozzle cavitating flow characteristics for diesel and biodiesel fuels

This study was performed to clarify criteria for cavitation inception and the relationship between flow conditions and cavitation flow patterns of diesel and biodiesel fuels. The goal was to analyze the effects of injection conditions and fuel properties on cavitating flow and disintegration phenomena of flow after fuel injection. To accomplish this goal, it was utilized a test nozzle with a cylindrical cross-sectional orifice and a flow visualization system composed of a fuel supply system and an image acquisition system. In order to analyze the rate of flow and injection pressure of the fuel, a flow rate meter and pressure gauge were installed at the entrance of the nozzle. A long distance microscope device equipped with a digital camera and a high resolution ICCD camera were used to acquire flow images of diesel and biodiesel, respectively. The effects of nozzle geometry on the cavitating flow were also investigated. Lastly, a detailed comparison of the nozzle cavitation characteristics of both fuel types was conducted under a variety of fuel injection parameters. The results of this analysis revealed that nozzle cavitation flow could be divided into four regimes: turbulent flow, beginning of cavitation, growth of cavitation, and hydraulic flip. The velocity coefficient of diesel fuel was greatly altered following an increase in flow rate, although for biodiesel, the variation of the velocity coefficient relative to the rate of flow was mostly constant. The cavitation number decreased gradually with an increase in the Reynolds number and Weber number, and the discharge coefficient was nearly equal to one, regardless of cavitation number. Lastly, it could not observe cavitation growth in the tapered nozzle despite an increase in fuel injection pressure.

Light‐activation of resin cement through ceramic: Relationship between irradiance intensity and bond strength to dentin

This study investigated the relationship between the irradiance transmitted through ceramic and the bond strength of a resin cement to dentin. After application of an adhesive system, elastomer molds with cylindrical orifices (1.2 mm in diameter) were placed onto bovine dentin surfaces and filled with a photoactivated luting agent (Enforce; Dentsply Caulk). Light-activation was performed through a 0.6-mm-thick ceramic disc using different intensities: 250, 400, 550, 700, or 850 mW/cm(2). Control specimens were irradiated without ceramic (1050 mW/cm(2)). The radiant exposure was kept at 30 J/cm(2). Light spectral distribution was analyzed with a spectrometer. Microshear test was conducted and modes of failure were classified under SEM. Bond strength data were analyzed with ANOVA and Student-Newman-Keuls' test (alpha < or = 0.05), and failure scores with the Kruskal-Wallis test (alpha < or = 0.05). A linear regression model assessed the relationship between irradiance and bond strength. Groups light-cured at 250 and 400 mW/cm(2) presented lower bond strengths than groups activated at 850 and 1050 mW/cm(2). The linear regression showed that a decrease in light irradiance predicts a decrease in bond strength (r(2) = 0.955; p = 0.004). A predominance of mixed failures was observed. No significant alteration in the spectral wavelengths was observed. Despite the constant energy dose, the bond strength was dependent upon the irradiance level.

Prediction of Fluid Inertance in Nonuniform Passageways

The dynamic response, stability, and noise characteristics of fluid components and systems can be strongly influenced by the inertance of the fluid in passageways, which are often of complex geometry. The inertance is a parameter that has often proved to be very difficult to accurately quantify, either theoretically or experimentally. This paper presents a method of numerical calculation of the inertance in a passageway, assuming inviscid, incompressible flow and zero mean flow. The method is simple to apply and can be applied to geometries of arbitrary complexity. Two simple but unorthodox ways of calculating inertance using a computational fluid dynamics and a finite element solid-modeling package are also demonstrated. Results are presented for a simple cylindrical orifice, a simple spool valve, and a conical poppet valve. The effect of the inertance on the response of a poppet valve is demonstrated.

Flow rate of some pharmaceutical diluents through die-orifices relevant to mini-tableting

The effects of cylindrical orifice length and diameter on the flow rate of three commonly used pharmaceutical direct compression diluents (lactose, dibasic calcium phosphate dihydrate and pregelatinised starch) were investigated, besides the powder particle characteristics (particle size, aspect ratio, roundness and convexity) and the packing properties (true, bulk and tapped density). Flow rate was determined for three different sieve fractions through a series of miniature tableting dies of different orifice diameter (0.4, 0.3 and 0.2 cm) and thickness (1.5, 1.0 and 0.5 cm). It was found that flow rate decreased with the increase of the orifice length for the small diameter (0.2 cm) but for the large diameter (0.4 cm) was increased with the orifice length (die thickness). Flow rate changes with the orifice length are attributed to the flow regime (transitional arch formation) and possible alterations in the position of the free flowing zone caused by pressure gradients arising from the flow of self-entrained air, both above the entrance in the die orifice and across it. Modelling by the conventional Jones–Pilpel non-linear equation and by two machine learning algorithms (lazy learning, LL, and feed-forward back-propagation, FBP) was applied and predictive performance of the fitted models was compared. It was found that both FBP and LL algorithms have significantly higher predictive performance than the Jones–Pilpel non-linear equation, because they account both dimensions of the cylindrical die opening (diameter and length). The automatic relevance determination for FBP revealed that orifice length is the third most influential variable after the orifice diameter and particle size, followed by the bulk density, the difference between bulk and tapped densities and the particle convexity.

Experimental investigation of the flow characteristics of small orifices and valves in water hydraulics

This paper describes an experimental investigation of the flow characteristics of water passing through small sharp-edged cylindrical orifices and valves of different shapes in water hydraulics. The test results using orifices with aspect ratios, l/d, of 1–15 and diameters of 0.8-3 mm show that the flow coefficients in the case of non-cavitating flow are larger than those of flow with cavitation and decrease with increase in the aspect ratio. However, the flow coefficients of flow with cavitation tend to be of constant value close to the contraction coefficient, Cc at small aspect ratios. Orifices with large aspect ratios have the effect of suppressing cavitation. Experimental results concerning the spool valve illustrate that the sharp-edged valve is less cavitation stricken at large opening than at small opening. Throttles with a triangular notch have better anticavitation ability than those with a square notch. The flow of the throttle with a square notch is significantly affected by the flow direction and the shape of the flow passage.

円筒オリフィス内部に発生するキャビテーション挙動の可視化

It is important to explain a high-speed liquid flow phenomenon because of high developments of various fluid machines. Cavitation is one of the most important phenomena in the high-speed liquid flow. When cavitation appears in the flow, it causes some troubles like a performance decrement of the fluid machine, vibrations, noise, and cavitation damage. So, it is important to observe the cavity behavior to solve such problems. In this study, fundamental experimental research about behavior of the cavitation was performed. The aspect of the cavitation in a circular cylindrical orifice was observed by the high-speed video camera with a laser sheet method. As a result, unsteady shedding behavior of vortex cavity was characteristically observed. In addition, pairing and coalescence behavior of vortex cavitation on the separated shear layer were clearly observed with the laser sheet method.

Characteristics of flow through small sharp-edged cylindrical orifices

The discharge coefficients for flow through small sharp-edged cylindrical orifices of diameters between 0.3 and 2 mm and aspect ratios between 1 and 50 are evaluated. The characteristics of flow in the separated, attached and cavitated flow regions are determined. It is shown that while the discharge coefficient scales with the Reynolds number and aspect ratio in the attached flow regions, the diameter influences the discharge coefficient in the separated flow region. The onset of cavitation in the orifice is also seen to be dependent on the diameter and aspect ratio. The hysteresis in the flow and the violent disintegration of the jet observed for an aspect ratio of about 5 are discussed.

Fast determination of the state in a cylindrical probe in the free-molecular regime

The present study is concerned with the physical properties governing in a tube of arbitrary size with a cylindrical orifice. The probe is placed into a hypersonic free-molecular flow at a 0°-angle of attack, and its surface is supposed to reflect diffusely. By solving the underlying integral-equation numerically, the moments of the distribution function are derived. This approach is, due to the free-molecular regime, much faster than any Monte Carlo particle method. Special interest is taken in the pressure distribution in the gauge volume; a comparison is drawn to the well-known case of a completely accommodated gas.

Superconducting open-gradient magnetic separator utilizing the braking effect of an axial component of magnetic force

The computer simulation of particles' trajectories in a simple cylindrical coil shows that the magnetic force acting on paramagnetic particles at the bottom part of the coil bore has a predominantly axial component which aims upwards and opposite to the force of gravity. In case of a superconducting coil and depending on the value of the particle mass susceptibility, the axial force component can exceed several times the force of gravity. As a result, an expressive braking of the motion of particles in the vertical downwards direction appears. This effect was utilized in an unconventional design of magnetic separator, the main advantage of which is the high selectivity of separation process. The separator operates either in a deflecting or attracting mode. The cylindrical orifice feeder and the splitter are located in the warm bore of a liquid helium cryostat with the inner diameter of 140 mm. A Magnetic force field with a magnetic flux density up to 7 T is generated by the NbTi superconducting coil. The experiments with the siderite and quartz classified particles have been performed and compared with the theory.

キャビテーション壊食に関する研究 第４報： 絞り形状および上流圧力変動の影響

Experiment was made of cavitation erosion due to the impingement of a cavitating jet using aluminum alloy specimens in petroleum based hydraulic fluid. Clarification was made of the effects of nozzles shape on cavitation erosion. Two short orifices were compared with the cylindrical orifice reported previously. It is clarified that the mass losses using either of the former exceeded that of the latter.The effects of unsteady flow field on cavitation erosion were also studied for the three orifices. Upstream orifice pressure was changed sinusoidally, its amplitude was less than 0.33 the mean value, 11.9MPa, and frequency, below 100 Hz. Downstream pressure remained essentially unchanged. Consequently, the peak erosion rate was not larger than the estimated as a function of nth power of upstream pressure (n>1). The frequency of upstream pressure caused slight increase in the peak erosion rate.

Impedance Characteristics of Hydraulic Orifices

The impedance characteristics of cylindrical and sharp-edged hydraulic orifices under non-zero mean flow conditions have been investigated through experimental measurement and computational fluid dynamics (CFD) simulation studies. Based upon these investigations a generic model of the impedance characteristics of orifices has been developed. This model can be adopted in computer simulations of pressure ripple in hydraulic systems. The results of this investigation also provide the basis for modelling more complex hydraulic components.

Nozzles for jet stabilization of rocks

The shape of the exit nozzles has great importance when developing the working part of a hydraulic jet monitor. All possible types of nozzles have already been investigated in certain experimental works of A. D. Al'tshul', I. E. Idel'chik, B. N. Siov, S. S. Shavlovskii, et al. [1, 2, 4]. In the present article the authors make an attempt to generalize collected data and to substantiate the type of nozzle which can be used in jet technology of rock stabilization. During discharge of a fluid through a round orifice without an extension (Fig. la), i.e., a sharp-edge orifice, the fluid particles smoothly round it. The extreme streams impart to the jet a conoidal shape and cause its contraction at the exit from the orifice. Contraction of the jet occurs also during discharge of a fluid through a cylindrical orifice having an extension (Fig. lb). But after that the discharge can flow differently. In the ftrst case, behind the smallest section of the jet its gradual expansion occurs. It reaches the inside walls of the orifice and flows out without contraction. An isolated annular cavity forms. This is that region which is filled with air and is located between the orifice walls and contracted section of the jet. The pressure in this region is Pc. In the second case the discharge differs in no way from discharge from a orifice without an extension, but the velocity in the contracted section can be described by the equation

Effects of effusing molecules on a suspended target

Knowledge of the angular distribution of velocity vectors of molecules streaming from an office into vacuum in effusion experiments is important in a variety of applications. Particular applications are in torsion-effusion experiments, where the recoil force depends on angular distribution, and in target-collection experiments, where the fraction of effusing vapor collected by the target depends on angular distribution. Recently, commercial vapor pressure balances based on the target-collection principle have become available. We present a theoretical analysis of the needed angular distribution for the general case of effusion orifices which are frustums of right circular cones, a case which includes cylinders. We apply this analysis to target-collection problems in which the target, collimator, or collector is circular or ring-shaped and coaxial with the orifice. Both mass effects and force effects are included. We consider the case in which a fraction ν (0 ⩽ ν ⩽ 1) of the impinging molecules stick permanently to the target and in which reflected molecules have a different “temperature” than do the impinging ones. We have available a FORTRAN program which calculates angular distributions and fractions of effusing molecules which strike a given target or collimator. For the special case of cylindrical orifices, closed-form equations based on derivations by Clausing are presented for the target-collection probability.

Current-Phase Relation for Flow of an S-Wave Paired Superfluid through a Cylindrical Channel of Finite Length

The Ginzburg-Landau equations are used to investigate superflow through a cylindrical orifice of radius R and length L. The order parameter is taken to be a complex scalar ψ, appropriate to an s-wave paired superfluid. It is assumed that ψ=0 on the surfaces of the orifice and that rigid boundary conditions may be employed at the ends of the tube. The use of a variational form for the radial variation of ψ reduces the problem to a one dimensional one. The critical value of L for each value of R has been calculated at which changeover from a single-valued to a multivalued current-phase relation occurs. The maximum supercurrent for tubes of various geometries has also been calculated.

Study on an Oil Damper with Variable Damping Mechanism : 1st Report, Damping Characteristics of the Damper with a Piston Having Cylindrical Orifices

The purpose of this work is how to design the variable oil damper whose damping is adjustable by varying the area of orifice in the piston. In this report, we deal with an oil camper having a few cylindrical orifices in order to study the fundamental characteristics of the variable oil damper. Two new method for analyze the damper are proposed. The first method of analysis is based on the assumption that the diameter of the piston is equal to the inner diameter of the cylinder but no friction occurs between the contact surfaces. However the assumption is far from being satisfactory in the actual oil damper. The second can be applied to the oil damper whose piston is smaller than the cylinder (in other words, the oil flows through the annular clearance and the cylindrical orifices). In these analyses, the flow through the channels is assumed to be incompressible, unsteady and laminar. Consequently, it is made clear that the magnitude of the damping in the latter type of oil damper is heavily subject to variation of the frequency of the oscillating piston.

Study on the oil damper with variable damping mechanism. 1st report Damping characteristics of the dashpot with a piston having cylindrical orifices.

本論文はピストンにあけられた孔の開口面積を変えることによって減衰を調整することのできる減衰可変オイルダンパを設計・製作することを目的としている.その理論的準備として,本報ではピストンに同一直径の複数個の円形孔流路を有するオイルダンパ,およびピストンとシリンダのすきまも流路として利用するオイルダンパの解析も試みた.その結果,後者のような形式のオイルダンパは非定常流の影響を受け易くなることがわかった.

Critical flowmetering: The characteristics of cylindrical nozzles with sharp upstream edges

A detailed study of the influence of axial length on the critical discharge coefficient of cylindrical orifices with sharp upstream edges is reported. Systematic consideration is given to the full range of geometries from the thin plate orifice up to the largest thickness/diameter ( t d ) ratios of practical interest. A simple theoretical approach is used together with a more complete description of the physical nature of the flow. A range of orifice geometries is identified for which the critical discharge coefficient is independent of Reynolds number and t d . Cylindrical nozzles in this range are particularly suited to critical flowmetering. They are simple to manufacture. Some new measurements are reported and these, together with existing experimental data, are shown to be consistent with the present analysis.

The approximate calculation of transmission probabilities for the conductance of tubulations in the molecular flow regime

Simple empirical expressions are given to calculate the transmission probability W (Clausing- factor) of cylindrical orifices and tubes. One expression covers the range for the ratio length/diameter × from 0.01 to 17, another from 11 to 100. The error is within ±0.5% with respect to the exact values from Nawyn and Meyer 5 .

Studies on the Coulter Counter Part II. Investigations into the Effect of Flow Direction and Angle of Entry of a Particle on both Particle Volume and Pulse Shape

In this paper the effect of the geometry and alignment of the flow straightener in the IITRI modification to the Coulter Counter are reported. For particle size analysis, the diameter of the flow straightener hole is shown to have no significant effect on the size distribution for diameters as low as 250 μm, but the alignment is highly significant when cylindrical orifices are used. The channel number of the mode and the broadness of the size distribution are shown to increase with increasing angle, the effect being more significant with a corresponding increase in current. When the size distribution measurement is perfomred using a constant total count for each angular measurement, the height of the mode decreases linearly with angle, the particles moving to higher voltage channels. This means that particles entering a sharp-edged orifice at wide angles are detected as particles of larger size. Pulse shape measurements confirmed the presence of sharp voltage spikes superimposed on conventional particle pulses from these particles, suggesting that pulse distortion had occurred. With the contoured orifice, there is no change in either the mode position or the breadth of the distribution with angle, and the height of the mode does not decrease. Pulse shape observations also show the absence of sharp spiked pulses from particles entering a contoured orifice, irrespective of the angle. In consequence, it is concluded that the distortion in the pulse shape and the resulting error in sizing is an orifice edge effect, and for the most accurate size analysis the use of a flow-directional collar aligned at 0° rotation to a contoured orifice is recommended. As a final section to the paper, the IITRI work is related to other recent work in the field, and the significance of this total work to particle size analysis is discussed.

Surface effects on the angular distributions of samarium vapor effusing from cylindrical orifices

A mass-spectrometric investigation has been made of the angular distributions of atomic samarium vapor effusing from cylindrical orifices of varying geometries and materials. Neither the theoretical angular distribution curves obtained from the Clausing theory nor any of the existing modifications of this theory coincided with the experimental distributions. The substantial effect of orifice material on the angular distribution curves suggests the possibility of bulk diffusion in the orifice walls as a contributory factor.