Orifice Orientation Research Articles

Validation and modification of a semi-empirical model for sound absorption by perforated liners in the absence of flow based on comparisons with data from full scale measurements

There is much current interest in improving the efficiency gas turbines used in aircraft engines and thereby reducing their carbon emissions. The perforated combustor liners in gas turbine silencers absorb the sound associated with thermo-acoustic instabilities and thereby reduce them. A semi-empirical model has been developed to predict the absorption of perforated liners in the absence of bias flow as a function of frequency in terms of liner characteristic such as orifice diameter, thickness, spacing, orientation and perforation ratio and liner configuration which requires an additional model for the impedance of the cavity behind the liner. The expression used for impedance includes a cavity factor which corrects for the change in combustor liner diameter. Predictions of energy absorption coefficient spectrum are compared with data from measurements on several configurations of full-scale liners. It is found that predictions using the standard tangent term in the cavity impedance do not agree with data at frequencies below 500 Hz as well as predictions that use a cosine term instead. The resulting model, which is validated by the data comparisons, should be useful in optimising liner characteristics for manufacture.

Optical evaluation of orifice orientation and number effects on active pre-chamber spark ignition combustion

Pre-chamber spark ignition combustion has shown several advantages for its implementation in engines, mainly related to its capability to achieve stable operation at lean or diluted mixtures and increased combustion speed. However, such systems have two challenges compared to traditional spark-ignition combustion: on the one hand, the stratification of the combustion process implies the usage of advanced tools for the analysis and optimization of the combustion system; on the other hand, the ignition process and overall combustion development is very sensitive to variations in the pre-chamber geometry. Previous works have explored particularly the effects of the pre-chamber volume compared to the engine displacement, the relationship between this volume and the total flow area of the nozzle connecting it to the rest of the cylinder, as well as the number and distribution of the nozzle orifices. In this work, the effect of the orientation of such orifices is explored on an optically-accessible rapid compression-expansion machine. Two main configurations are used: straight nozzle, where the axes of all the orifices intersect in a single point approximately in the center of the pre-chamber volume; and tilted nozzle, where the axes of two opposed orifices are displaced 1.5 mm, inducing a swirling motion both in the pre-chamber during the compression process and in the main chamber once ejection starts. Additionally, a sensitivity to the number of orifices is performed for the tilted nozzle layout. The results show that the induced swirling motion has little effect on the pre-chamber combustion development and initial ejection velocity, but it has a positive impact on the subsequent flame propagation and combustion efficiency, especially for ultra-lean conditions.

Evaluation of Pre-Chamber Orifice Orientation in an Ethanol-Fueled Spark-Ignition Engine for Passenger Car Applications

Evaluation of Pre-Chamber Orifice Orientation in an Ethanol-Fueled Spark-Ignition Engine for Passenger Car Applications

Laser based visualization of plumes evolving from circular orifice: Effect of orifice orientation

The present paper is about Kelvin-Helmholtz instability and its visualization using laser-based techniques. The smoke is produced by burning an incense material which acts as a tracer. The flow field is illuminated by a pointer laser by making a laser sheet for recording the image. The images were recorded using a digital mobile camera and were used for further assessment. The flow field shows the evolution of plume from the paper cup, the formation of Kelvin-Helmholtz vortices, and its transition to turbulent flows.

Experimental and Numerical Assessment of Water Leakages in a PVC-A Pipe

Nowadays, in the definition of effective approaches for the sustainable management of water pressurized systems, the assessment of water leakages in water supply and distribution systems represents a key aspect. Indeed, the large water volumes dispersed yearly provoke relevant environmental, technical and socio-economic costs. Worldwide, many water systems show alarming levels of water losses, due to both the poor sealing of joints and the presence of cracks, enhanced by a high pressure level greater than that strictly required for assuring a proper service level to users. With the aim of analysing the correlation between pressure and leakages, in this work the results of an experimental and a numerical Computational Fluid Dynamics (CFD) investigation are provided and discussed. With reference to a drilled PVC-A (Polyvinyl Chloride-Alloy) pipe, a new-generation plastic material for water systems use, an experimental investigation was first carried out at the Laboratory of Hydraulics of the University of Naples Federico II, aimed at assessing the leakage-pressure relation for transversal rectangular orifices. A CFD model was then implemented and calibrated with experimental results, to different geometric configurations of the orifice, with the aim of assessing the dependence of the orifice geometry and orientation on the calibration of leakage law parameters.

Comprehensive 4-stage categorization of bicuspid aortic valve leaflet morphology by cardiac MRI in 386 patients.

Bicuspid aortic valve (BAV) disease is heterogeneous and related to valve dysfunction and aortopathy. Appropriate follow up and surveillance of patients with BAV may depend on correct phenotypic categorization. There are multiple classification schemes, however a need exists to comprehensively capture commissure fusion, leaflet asymmetry, and valve orifice orientation. Our aim was to develop a BAV classification scheme for use at MRI to ascertain the frequency of different phenotypes and the consistency of BAV classification. The BAV classification scheme builds on the Sievers surgical BAV classification, adding valve orifice orientation, partial leaflet fusion and leaflet asymmetry. A single observer successfully applied this classification to 386 of 398 Cardiac MRI studies. Repeatability of categorization was ascertained with intraobserver and interobserver kappa scores. Sensitivity and specificity of MRI findings was determined from operative reports, where available. Fusion of the right and left leaflets accounted for over half of all cases. Partial leaflet fusion was seen in 46% of patients. Good interobserver agreement was seen for orientation of the valve opening (κ = 0.90), type (κ = 0.72) and presence of partial fusion (κ = 0.83, p < 0.0001). Retrospective review of operative notes showed sensitivity and specificity for orientation (90, 93%) and for Sievers type (73, 87%). The proposed BAV classification schema was assessed by MRI for its reliability to classify valve morphology in addition to illustrating the wide heterogeneity of leaflet size, orifice orientation, and commissural fusion. The classification may be helpful in further understanding the relationship between valve morphology, flow derangement and aortopathy.

Developing the USDA ARS Spray Nozzle Models for Rotary Wing Applications

Abstract. Optimizing aerial spray applications requires proper setup of the sprayer system, particularly with respect to nozzle selection and operation, which significantly affects spray deposition, product efficacy, and spray drift. Droplet size from an aerial application is a function of the combination of nozzle type, nozzle orifice size, spray pressure, orientation angle, and airspeed of the aircraft. A set of computational models for 14 commonly-used aerial application nozzles were developed and released for use by applicators. These models allow applicators to determine the droplet size characteristics associated with their specific nozzle and operational setup, determining the proper combination of orifice, pressure, orientation, and airspeeds from 22 to 54 m/s (50 to 120 mph), which are commonly-associated with applications made from rotary wing aircraft (i.e., helicopters). Both spreadsheet and smartphone user interfaces are available for applicators to use to ensure that their application conforms to the legal droplet size requirements specified on an agrochemical product label. Keywords: Aerial application, Atomization, Droplet size, Droplet size models, Spray nozzles.

Impact of orifice orientation on a finite-span synthetic jet interaction with a crossflow

The formation and evolution of flow structures associated with a finite-span synthetic jet issued into a zero-pressure gradient boundary layer were investigated experimentally using stereoscopic particle image velocimetry. A synthetic jet with an aspect ratio of AR = 18 was mounted on a flat plate and its interaction with a free stream, having a velocity of U∞ = 10 m/s (Reδ = 2000) at momentum coefficients of Cμ = 0.08, 0.33, and 0.75, was studied. The effect of the orifice pitch (α = 20∘–90∘) and skew (β = 0∘–90∘) angles on vortex formation as well as the global impact of the synthetic jet on the flow field was explored in detail. It was found that the orifice orientation had a significant impact on the steady and unsteady flow structures. Different orifice skew and pitch angles could result in several types of vortical structures downstream, including: no coherent vortex structure, a single (positive or negative) strong vortex, or a symmetric vortex pair. In all cases, the velocity near the wall was increased; however, cases with higher blockage (i.e., more wall-normal, transverse orifice) resulted in a strong velocity deficit in the free stream where orifices with lower pitch angles yielded in an increase in velocity throughout. The analysis is concluded with a summary of quantitative metrics that allude to flow control effectiveness.

A Practical Interpretation and Use of theUSDA Aerial Fixed-Wing Nozzle Models

<abstract> <b><sc>Abstract. </sc></b>Proper selection and operation of spray nozzles associated with aerial applications is critical to insuring efficacy while mitigating off-target movement. Labels for most agrochemical products applied in the United States specifically define the droplet size or spray classification that can be used to apply that product. Droplet size associated with most aerial application nozzles is a function of the combination of orifice size, spray pressure, orientation angle, and airspeed used. Recently, a set of computational models for the most commonly used aerial application nozzles were developed and released for use by applicators. While these models allow applicators to determine the droplet size characteristics associated with their specific nozzle and operational setup, determining the proper combination of orifice, pressure, orientation, and airspeed, can be an interactive process, leading to frustration and ultimately non-use of the models. To minimize the iterative calculations and provide a more intuitive, visual interpretation of the computational droplet size models, a series of graphical representations of each nozzle‘s complete operational space were developed for use by applicators. These graphical interfaces allow for optimal operational combinations to be more quickly identified and integrated into the application system setup decision matrix. The ultimate goal of this work is to increase the usage rate of the spray droplet size models by aerial applicators by providing a more intuitive and efficient user interface.

Effects of Orifice Orientation and Gas-Liquid Flow Pattern on Initial Bubble Size

In many gas-liquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gas-liquid flow pattern. Bubble formation models for variant gas-liquid flow patterns have been developed based on force balance. The effects of the orientation of gas-liquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient air-water system, the suitable gas-liquid flow pattern is important to obtain smaller bubbles under the low velocity liquid cross-flow conditions with stainless steel spargers. Among the four types of gas-liquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found to be insignificant when liquid velocity is higher than 3.2 m·s−1 or the orifice diameter is small enough.

A comparison of three turbulence models for the prediction of parallel lobed jets in perforated panel optimi zation

The general context of the present study is the design of high induction HVAC air diffusers by means of passive jet control. When the diffuser is a perforated panel with lobed orifices ( Meslem et al. 2010), the optimization of jet induction consists in improving the orifice’s geometry, the spacing between orifices and their arrangement on the panel. In this study, the flow field of a turbulent twin cross-shaped jet is investigated numerically using the standard k-ε model, the Shear Stress Transport (SST) k-ω model and the Reynolds Stress Model (RSM). The results are compared with PIV measurements. The objective is to assess their capability and limitations to predict the significant features of twin jet flow when the flow is numerically resolved through a lobed diffuser. It is shown that the k-ε and RSM models are more appropriate for predicting potential jet core length, the change in jet centreline streamwise velocity, and flow expansion in the symmetry plane of the twin jet flow. However, these models overestimate the overall flow expansion and the jet volumetric flow rate. The SST k-ω model seems more appropriate for the prediction of such dynamic integral quantities. A high level of turbulent kinetic energy predicted by the k-ε and RSM models in the near field of jets is probably the reason for this overestimation of jet induction. The SST k-ω model would appear to be the most appropriate tool for optimizing orifice design, orifice to orifice spacing and relative orifice orientation on a perforated panel diffuser.

Experimental study on horizontal wellbore cleanout by rotating jets

Horizontal wellbore cleanout by rotating jets has been developed rapidly in the past decades. To improve the sand cleanout efficiency, the strength of helical flow as one of the most important factors is necessary to be investigated and optimized. The flow rate, nozzle size, nozzle orientation and annular size have the major influence on the arising, performing and attenuating of annular helical flow. This paper presents the experimental results of a horizontal wellbore cleanout with varying nozzle assemblies in orifice size and orientation, tubing size, solid size, and flow rate. The tests of stationary circulation and wiper trip were carried out respectively. In the stationary circulation stage, there exists a critical length between sand bed and cleaning tool which results the two kinds of mechanisms to transport the sand. When the distance is shorter than the critical length, the primary mechanism of sand suspend is annular helical flow. As the distance is longer than it, the mechanism turns into straight annular flow which results in lower cleanout efficiency. In this study, the critical length increases rapidly with the increase of flow rate, tubing size and sand size. The sand bed moving velocity changing with the distance was also investigated and it is beneficial to optimize the wiper trip speed of cleaning tool. For the wiper trip stage, there exists the maximum wiper speed which can fulfill the requirement of completely sand cleanout when the tool is pulled out of the hole(POOTH), and it increases with the increase of flow rate and tubing size, and the decrease of sand size. The nozzle assembly is one of the most important factors to affect the helical flow profile and sand cleanout efficiency. The optimum lateral nozzle size and nozzle orientation were also obtained to get a best performance in annular helical flow and wiper trip speed. This study can contribute to the optimum design of nozzle assemblies, operation procedures and hydraulic parameters so that the highest efficiency of horizontal wellbore cleanout can be achieved.

Flow pattern, mass flow rate, pressure distribution, and temperature distribution of two-phase flow of HFC-134a inside short-tube orifices

New experimental data on the influence of short-tube orifice configuration, including diameter, length, length-to-diameter ratio ( L/ D), and orientation on the flow pattern, mass flow rate, and pressure distribution of HFC-134a inside the short-tube orifice are presented. Short-tube orifice diameters ranging between 0.605 and 1.2 mm with L/ D ranging between 1.87 and 33 are used in the experiments. Three different forms of the metastable liquid flow, which are metastable liquid core flow, conical metastable liquid core flow, and full metastable liquid flow are visually observed. The short-tube orifice diameter has a significant effect on the increase in the flow rate. Conversely, the change in the orientation of the test section has no significant effect on the flow rate. The choke flow phenomenon disappears inside the short-tube orifice when L/ D is less than 2.91. Based on the present data, a correlation for predicting the mass flow rate through short-tube orifices is proposed.

Dye visualisation of inclined and skewed synthetic jets in a cross flow

AbstractDye visualisation of both inclined synthetic jets and skewed synthetic jets was undertaken in a cross-flow experiment and the results were compared with those of normal synthetic jets. The process of vortex roll-up near the orifice exit and how the structure develops and interacts with the cross-flow as it propagates downstream was investigated so as to obtain an understanding of the effect of orifice orientation on the behaviour of synthetic jets. The effects of varying Reynolds number, velocity ratio and Strouhal number due to changes in diaphragm displacements and freestream velocities on the characteristics of synthetic jets were also examined. It is observed that in comparison to the normal jets vortical structures produced by both inclined and skewed jets tend to stay closer to the near wall region where maximum flow control effect is required. In both cases, at a relatively low Reynolds number and velocity ratio the active structures produced by the synthetic jet appear to be hairpin vortices which turn into vortex rings that migrate away from the wall as the Reynolds number and velocity ratio increase. These hairpin vortices are persistent in the near wall region hence are believed to be desirable structures for delaying flow separation.

Investigation of the prechamber geometrical configuration of a natural gas spark ignition engine for cogeneration: part I. Numerical simulation

The effects and consequences of transferring the ignition point of the conventional combustion chamber into a small unscavenged prechamber were evaluated through a numerical simulation based on the CFD-code KIVA-3V. The prechamber flow characteristics at the location of the gap between the spark plug electrodes and in the crank angle period where the ignition is expected to occur were compared to the corresponding conditions in the conventional combustion chamber. The influence of the prechamber geometrical configuration was evaluated through variations of the nozzle orifice diameter, number and orientation, as well as prechamber volume and internal shape. The results show that the velocity magnitude is mainly dependent on the prechamber shape, and that it is generally of the same order as with direct ignition. Further, the turbulence intensity varies strongly with the geometrical configuration and reaches, in most cases, a much higher value in the prechamber. The partial dilution of the unburnt mixture with unscavenged prechamber residual gas generally leads to a slightly lower fuel to air equivalence ratio. However, nozzle orifices imparting a swirl motion or a prechamber shape with an almost uniform cross section can result in fuel concentration very close to or beyond the flammability limit. The prechamber charge and thereby the amount of energy available for the main chamber ignition depends on the prechamber volume and on the pressure drop across the nozzle orifices.

Effects of sparger height and orifice orientation on solids dispersion in a slurry bubble column

AbstractThe effects of gas distributor height and the orientation of its orifices are investigated on solids dispersion and gas holdup profiles in a three‐phase slurry bubble column. The height of the distributor was varied to cover locations from near column bottom to above the settled solids bed height. The orifice orientations were changed from upward facing to downwards facing directions. The measurements were conducted in a Plexiglas column of 0.15 m ID and 2.5 m height. The gas phase was oil‐free compressed air while tap water was used as liquid phase. Glass beads with an average particle diameter of 35 μm and density of 2450 kg/m3 constituted the solid phase. The settled bed height was about 0.4 m which provided an average slurry concentration of about 15% (v/v) when all solids were dispersed. Both axial and column average phase holdups were measured. Effects of sparger location, gas jets formation and liquid circulation patterns on gas holdups and solids dispersion are analyzed. Empirical correlations are developed to relate sparger location to solids dispersion as a function of gas velocity. Optimum sparger height and orifice orientation is proposed based on the measurement of this study.

Penetration of Windborne Long Fibers into Openings

ABSTRACT A study was conducted to provide a set of experimental data on penetration of long fibers (0.635 cm) with a diameter of 8 μm through orifices of various dimensions under controlled wind speeds ranging between 130 and 450 cm/sec. The dependence of fiber penetration on orifice shape, size, and orientation was examined systematically for several airflow rates. The measurements demonstrate that the penetration efficiency of fibers varies widely for different experimental conditions. The fiber penetration through an orifice drilled on a plate was found to increase sharply with increasing wind velocity. It is believed that this work represents the first study that systematically measures the penetration of windborne long fibers into openings.

正常のえん下圧波形

The resting pressure and the pressure changes of the pharyngoesophageal segment during swallowing were recorded in 15 normal subjects.A specially designed intracorporeal type of measuring device which had three strain gauge type microtransducers was used for the pressure measurements. The three recording orifices were separated by arcs of 120° and by 5-cm intervals in the vertical direction.C. S. Winans showed in 1972 that the resting pressure within the pharyngoesophageal high pressure zone was dependent upon orifice orientation. According to the present results, the deglutition pressure changes within the high pressure zone was also closely related to orifice direction.We obtained some useful informations through the analysis of the wave form of pressure changes.

Normal Lower Esophageal Sphincter Pressure: A Comparison of Rapid vs. Slow Pull-Through Techniques

This study simultaneously compared radially oriented normal lower esophageal sphincter pressure in 18 volunteers measured by motorized rapid pull through, hand withdrawn slow pull through, and motorized slow pull through. Slow pull-through pressures were scored four ways: peak pressure, mean pressure, highest minimum pressure, and pressure at respiratory phase reversal. Motorized and hand withdrawn slow pull-through methods gave identical average pressures, but the motorized method was slightly less variable except for the peak pressure scoring method where minimum variability did not require motorized withdrawal (average coefficient of variation = 18%). Rapid pull through pressures varied significantly more than all other methods (average coefficient of variation = 38%). Radial pressure asymmetry occurred with all methods with leftward pressures ranging from 62% greater for rapid pull through to 21% greater for respiratory reversal scored slow pull through. The peak, mean respiratory reversal and minimum slow pull-through methods correlated very well with each other (r ranged from 0.89 to 0.98) but not with rapid pull through (r ranged from 0.45 to 0.58). The interobserver correlation coefficient was poorest with respiratory reversal slow pull through (0.86), and excellent for all other pull-through methods (0.96-0.99). In conclusion, the method and recording orifice orientation chosen to record lower esophageal sphincter pressure markedly influenced the magnitude and variability of recorded pressure. Slow pull through is more reliable than rapid pull through and the peak method appears to be the easiest way to score slow pull through pressures.

Oleopneumatic shock strut dynamic analysis and its real-time simulation

An analog simulation representing dynamic shock absorption characteristics of a conventional oleopneumatic landing gear strut has been developed. This simulation includes both airplane and strut dynamics. The basic equations of motions are those used for a two-degree-of-freedom system. The hydraulic, pneumatic, and mechanical aspects of the shock strut dynamics have been analyzed. The metering orifice and snubber orifice discharge coefficients have been treated as a function of Reynolds number, orifice shape, and orifice orientation. The snubber valve hydraulic force during compression and rebound has been accounted for. Other factors considered in the system simulation are internal friction in the shock strut, wing lift, inclination of the landing gear, and the effects of wheel spinup and drag loads. A special circuit was devised on the analog simulation which allows the operator to vary the shape of the metering pin, observe the effects on shock strut load instantly, and optimize the load stroke curve(s). The simulation has the capability of high-speed, iterative operation. Good correlation has been established between flight/drop test data and the simulation predicted results. The simulation therefore provides an important design tool for optimizing pin profile, as well as evaluating existing shock strut designs.