Venturi Nozzle Research Articles

Gas dilution system using critical flow Venturi nozzles for generating primary trace-moisture standards in multiple gas species

Gas dilution systems are commonly used to generate calibration gas mixtures for secondary gas standards. However, if a gas dilution system is used to generate gas mixtures for primary trace-moisture standards in multiple gas species, difficulty arises; flow control with relative stability of better than 0.009% is required although the relative uncertainty of the best gas flow meter to date is around 0.3%. In this study, we developed a novel gas dilution system using critical flow Venturi nozzles to address this problem. The developed dilution system can measure and control the flow rates of gases in the range of approximately 0.05 l min−1 to 7 l min−1 (when converted to those measured at 101 325 Pa and 273.15 K) with relative stability of better than 0.007%. Using the dilution system, we developed a magnetic suspension balance/diffusion-tube humidity generator capable of generating trace moisture in N2 in the range of approximately 10 nmol mol−1 to 5 µmol mol−1 in amount fraction. The accuracy of the generated trace-moisture standard was verified by measurement with cavity ring-down spectroscopy.

Experimental and numerical investigation of the cavitation-induced choked flow in a herschel venturi-tube

Due to their simple geometry, cavitating Venturi nozzles (CV) are a long time subject of experimental as well as numerical investigations. However, research mostly focused on certain aspects like the comparison of experimental data with numerical cavitation models or the spray development of diesel injection nozzles, but rarely on the choked flow condition itself, especially with regard to liquid flow measurement.If the pressure decreases due to the local acceleration of the flow to the respective vapor pressure, a choked flow condition similar to the well-known critical flow Venturi-nozzles (CFVN) develops. For the purpose of gaining further insight into the choked flow condition with respect to liquid flow measurement, high-speed camera investigations of a transparent Herschel Venturi-tube configuration, also known as classical Venturi-tube, were performed. Together with pressure and flow rate measurements, they demonstrated the overall stable flow behavior under choked conditions. With additional numerical investigations, phenomena during the onset of the choked condition were clarified. Furthermore, a simple correlation for the calculation of the actual flow rate during the choked condition, including a temperature correction was proposed.

Silicon micro venturi nozzles for cost-efficient spray coating of thin organic P3HT/PCBM layers

Improvements on spray coating are of particular interest to different fields of technology as it is a scalable deposition method and processing from solutions offer various application possibilities outside of typical facilities. When it comes to the deposition of expensive and film-forming media such as organic semiconductors, consumption and nozzle cleaning issues are of particular importance. We demonstrate the simple steps to design and fabricate micro venturi nozzles for economical spray coating with a consumption as low as 30–50 µl · min−1. For spray coating an active area of 25 cm2 a 2.45–4.01 fold coating efficiency is observed compared to a conventional airbrush nozzle set. The electrical characterization of first diodes sprayed with an active layer thickness of ~750 nm using a single micronozzle at a coating speed of 1.7 cm2 · min−1 reveals a good external quantum efficiency of 72.9% at 532 nm and a dark current of ~7.4 · 10−5 mA · cm−2, both measured at −2 V. Furthermore, the high resistance of the micronozzles against solvents and most acids is provided through realization in a silicon wafer with silicon dioxide encapsulation, therefore allowing easy and effective cleaning.

Effect of sprayer settings on spray drift during pesticide application in poplar plantations (Populus spp.)

This study assessed spray drift generated by sprayer settings commonly used for pesticide application in poplar plantations (Populus spp.). Tests were conducted per the ISO 22866 methodology using a mounted air-assisted sprayer (Tifone VRP600) equipped with a swivel-cannon air conveyor (model Cannone 50S). Trials evaluated sprayer settings, combinations of nozzle types, airflow rates, and air direction in both adult and young poplar plantations.Overall, spray drift amounts registered downwind of poplar plantations were less than those obtained to derive reference drift curves during the EU Plant Protection Product registration process that used late-growth-stage fruit crops. In the adult poplar plantation, Venturi nozzles (TVI 8004 red) yielded the highest drift reductions compared to reference sprayer setting, especially at distances farthest from the sprayed area (86% between 40 and 47m). Highest total drift reductions were achieved when conventional nozzles (1.81mm ceramic disc-core) were combined with their spray direction modified for an inclined cannon spray unit. Alternatively, the young poplar plantation showed no drift reduction for distances farthest from the sprayed area, regardless of sprayer settings, which likely resulted from lower foliage density and widely-spaced rows. Yet, both Venturi nozzles combined with high fan flow rates and conventional nozzles combined with reduced fan flow rate showed total spray drift reductions of over 70% within the downwind sampling area.These experimental results represent the first set of data on spray drift amounts in poplar plantations, which is key for defining the reference curves and best practices to reduce spray drift in tall tree plantations.

Nucleation of super-critical carbon dioxide in a venturi nozzle

Pressure reduction at the entrance of the compressor in supercritical CO2 Brayton cycles may cause nucleation and create a mixture of vapor and liquid droplets due to operation near the saturation conditions. Transient behavior of the flow after nucleation may cause serious issues in operation of the cycle and degrade the materials used in the design. The nucleation behavior of supercritical carbon-dioxide inside a venturi nozzle near the critical point is computationally studied. A transient compressible 3D Navier–Stokes solver, coupled with continuity, and energy equations have been implemented. In order to expedite the simulations, Fluid property Interpolation Tables (FIT) based on a piecewise biquintic spline interpolation of Helmholtz energy have been integrated with OpenFOAM to model S-CO2 properties. The mass fraction of vapor created in the venturi nozzle has been calculated using homogeneous equilibrium model (HEM). Nucleation behavior has been shown to be very sensitive to the inlet pressure, inlet temperature, and flow rate. The flow conditions that led to nucleation were identified. Nucleation was observed in the throat area and divergent section of the nozzle for mass flow rates from 0.050kg/s to 0.065kg/s, inlet pressure from 7.8 to 7.4MPa for fixed exit pressure equal to 7.28MPa. The inception of high-vapor-content nucleation was first observed in the throat area away from the side walls that remained confined to the throat region in later times. However, near the walls, a high liquid-content two-phase region was detected, first in the divergent section. At later times, the two-phase region was convected downstream toward the nozzle exit.Nucleation in central plane was associated with larger pressure drop and higher vapor-content (higher volume fraction); whereas lower pressure drop and more liquid-content (lower volume fraction) was observed near the walls.

Micro-Venturi injector: design, experimental and simulative examination

This paper reports the first factorial design of a micro Venturi injector completed by a simulative investigation of the device. For the first time, a comprehensive correlation between the point of the maximum vacuum pressure generated by the Venturi nozzle and the variation of the inlet pressure is shown. The device reported in this contribution enables a new solution for robust low-pressure generation in parallel fluidic channels.

MQL machining: from mist generation to tribological behavior of different oils

Minimum Quantity Lubrication (MQL) is a solution towards cutting fluids reduction. This technology requires a deeper understanding of local mechanisms (in particular tribology) occurring at micrometer levels. A previous study showed that two oils with similar lubricating performance (full lubrication) could differ when applied through MQL. The following study aims at closing the loop between local tribologigal results and mist generation phenomenon by observing the mist generated (particle size distribution, oil flow rate) for both oils. The following conclusions can be drawn: an oil with low viscosity will be easily pumped into the venturi nozzle leading to a higher quantity of oil which can be sent to the pipeline. Different sizes of droplets are observed at the generator outlet: 8, 100 and 450 μm. Even though big particles appear sporadically, they do represent approximately 70 % of the volume sprayed. Neither the air pressure nor the oil properties seem to influence the size of the droplets produced. Droplets coagulation/break up and film breakup are not observed inside the pipeline for the chosen configuration. However, when traveling through the pipeline, the smallest droplets interact with the inner wall by forming an oil film and a spatter flow (laminar) is generated in addition to the spray flow (turbulent). The mist at the pipeline outlet is mainly composed of spray droplets (85 % for the first oil and 66 % for the second oil). Furthermore, the spray for both oils is composed of similar types of particles with similar proportions. As a consequence, the main differentiation between oils is in terms of number of particles in the sprayed mist. The MQL performance is therefore explained from the mist generation to the tribological behavior of the cutting interface.

Thermal effect on body temperature distribution of the critical flow Venturi nozzle

The expansion of the gas through a critical flow Venturi nozzle (CFVN) leads to a 50°C temperature drop of the gas at the nozzle throat. The body of CFVN is also cooled, which produces several effects on the flow characteristics called thermal effects. Thus, there is an urgent necessary to investigate the dynamic temperature distribution of CFVN body. Firstly, experiments were conducted by a multipoint temperature acquisition system. The dynamic temperatures of 12 sampling points for each stainless steel CFVN were obtained. It is found that the dynamic response time of CFVN body temperature can be hundreds to thousands of seconds. The maximum body temperature drop of 16.5°C was observed. Then some isotherm maps of CFVN body were obtained by the Kriging interpolation method. Finally, CFD simulations were carried out to explain the experimental results because the flow field of axisymmetric nozzle is difficult to be observed. The results revealed the position of shock wave is the main influence on body temperature distribution of CFVN. All the results can be used to further analyze the thermal effect of CFVN.

Recommendations on Selection and Design of Pulsation Dampeners for Oil-Gas Field Separating Plants

Processes in pulsation dampeners are described and recommendations on the selection and design of pulsation dampeners are given. Pulsation dampeners should be installed before the separators or heat exchangers at the inlet of the first separation stage. Pulsation dampeners are not needed before other separation stages. Three-pipe pulsation dampeners with a Venturi nozzle at the inlet are installed before the separators that have separate liquid and gas inlets. A Venturi nozzle is installed before the separators and heat exchangers that have a single mixture inlet. The flow area of the Venturi nozzle neck should be smaller than the flow area of the pulsation dampener–throttle track leading to the next separation stage.

Research on the Coaxial Connection between Gas Flowmeter and Critical Flow Venturi Nozzle Gas Flow Standard Device

As an important measurement instruments of trade metering, gas flowmeter has been more and more widely used, and the quantity value transfer of the flow meter is becoming increasingly significant. In order to realize the accurate measurement, the method of the coaxial connection between gas flowmeter and critical flow Venturi nozzle gas flow standard device is studied in this paper, and the coaxial error between this gas flowmeter and standard device within ±1mm is achieved.

Computational study of different venturi and orifice type hydrodynamic cavitating devices

This paper reports optimization of various geometrical parameters of two types of hydrodynamic cavitation reactors (HC) such as venturi type and orifice type. Mostly orifice and venturi nozzles are used as HC reactor, a simple valve can also be used to cause cavitation which depends on geometry and area of opening. Different operating and geometrical parameters such as divergence angle, throat height/diameter to length ratio, number of holes and inlet pressure to the cavitating device were selected to study the inception, growth and dynamics of cavities. In this work, a comprehensive computational fluid dynamics simulation is performed to numerically investigate the 3-D flow behaviors within HC reactors using cavitational model with standard k - ɛ Turbulence model. The study of different geometries of venturi type HC reactor (like slit, circular and elliptical) shows that 1:1 of the ratio of throat height/diameter to length and 6.5° of divergence angle is an optimum geometry for best cavitational activity. In case of orifice, 1:3 of the ratio of diameter to length is best for cavitation and an increase in the total flow area increases the cavitational yield.

The experimental study of a water-saving wet electrostatic precipitator for removing fine particles

A water-saving wet electrostatic precipitator was designed and tested to study fine particles emission. A Venturi nozzle was added to the front of electrostatic precipitator, which replaced the spray washing in the electric field. The experimental results indicated that the performance of spray-type ESP was superior to that of film-type ESP and other treatment processes. It was worth noticing that the lowest collection efficiency for spray-type ESP varied under different parameters, which distinguished from other types. Furthermore, the efficiency difference of spray-type ESP during given experimental time only had a slight fluctuation in range of ±2.8%.

Determining the drift potential of Venturi nozzles compared with standard nozzles across three insecticide spray solutions in a wind tunnel.

Previous research has sought to adopt the use of drift-reducing technologies (DRTs) for use in field trials to control diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae) in canola (Brassica napus L.). Previous studies observed no difference in canopy penetration from fine to coarse sprays, but the coverage was higher for fine sprays. DBM has a strong propensity to avoid sprayed plant material, putting further pressure on selecting technologies that maximise coverage, but often this is at the expense of a greater drift potential. This study aims to examine the addition of a DRT oil that is labelled for control of DBM as well and its effect on the drift potential of the spray solution. The objectives of the study are to quantify the droplet size spectrum and spray drift potential of each nozzle type to select technologies that reduce spray drift, to examine the effect of the insecticide tank mix at both (50 and 100 L ha(-1) ) application rates on droplet size and spray drift potential across tested nozzle type and to compare the droplet size results of each nozzle by tank mix against the drift potential of each nozzle. The nozzle type affected the drift potential the most, but the spray solution also affected drift potential. The fine spray quality (TCP) resulted in the greatest drift potential (7.2%), whereas the coarse spray quality (AIXR) resulted in the lowest (1.3%), across all spray solutions. The spray solutions mixed at the 100 L ha(-1) application volume rate resulted in a higher drift potential than the same products mixed at the 50 L ha(-1) mix rate. The addition of the paraffinic DRT oil was significant in reducing the drift potential of Bacillus thuringiensis var. kurstkai (Bt)-only treatments across all tested nozzle types. The reduction in drift potential from the fine spray quality to the coarse spray quality was up to 85%. The addition of a DRT oil is an effective way to reduce the spray solution drift potential across all nozzle types and tank mixes evaluated in this study. The greatest reduction in drift potential can be achieved by changing nozzle type, which can reduce the losses of the spray to the surrounding environment. Venturi nozzles greatly reduce the drift potential compared with standard nozzles by as much as 85% across all three insecticide spray solutions. Results suggest that a significant reduction in drift potential can be achieved by changing the nozzle type, and can be achieved without a loss in control of DBM. © 2016 Society of Chemical Industry.

Ion transfer from an atmospheric pressure ion funnel into a mass spectrometer with different interface options: Simulation-based optimization of ion transmission efficiency.

We optimized an atmospheric pressure ion funnel (APIF) including different interface options (pinhole, capillary, and nozzle) regarding a maximal ion transmission. Previous computer simulations consider the ion funnel itself and do not include the geometry of the following components which can considerably influence the ion transmission into the vacuum stage. Initially, a three-dimensional computer-aided design (CAD) model of our setup was created using Autodesk Inventor. This model was imported to the Autodesk Simulation CFD program where the computational fluid dynamics (CFD) were calculated. The flow field was transferred to SIMION 8.1. Investigations of ion trajectories were carried out using the SDS (statistical diffusion simulation) tool of SIMION, which allowed us to evaluate the flow regime, pressure, and temperature values that we obtained. The simulation-based optimization of different interfaces between an atmospheric pressure ion funnel and the first vacuum stage of a mass spectrometer require the consideration of fluid dynamics. The use of a Venturi nozzle ensures the highest level of transmission efficiency in comparison to capillaries or pinholes. However, the application of radiofrequency (RF) voltage and an appropriate direct current (DC) field leads to process optimization and maximum ion transfer. The nozzle does not hinder the transfer of small ions. Our high-resolution SIMION model (0.01mm grid unit(-1) ) under consideration of fluid dynamics is generally suitable for predicting the ion transmission through an atmospheric-vacuum system for mass spectrometry and enables the optimization of operational parameters. A Venturi nozzle inserted between the ion funnel and the mass spectrometer permits maximal ion transmission. Copyright © 2015 John Wiley & Sons, Ltd.

POD study of aerated cavitation in a venturi nozzle

The fact of injecting bubbles into a cavitating flow influences typical cavitating behavior. Cavitation and aerated cavitation experiments has been carried out on a symmetrical venturi nozzle with convergent/divergent angles of 18° and 8°, respectively. A snapshot Proper Orthogonal Decomposition (POD) technique is used to identify different modes in terms of discharge flow velocity, pressure and injected quantity of air. The energy spectrum per given mode is also presented. The first four modes are outlined in the present paper for an aerated and non-aerated cavitating flows.

Humidity effect on the calibration of discharge coefficients of critical flow Venturi nozzles in a pVTt facility

The available research on the humidity effect when calibrating the discharge coefficients of critical flow Venturi nozzles has mostly treated the humid air as a mixture of vapor and dry air. In this paper, atmospheric air with normal humidity was used to calibrate the discharge coefficients of critical flow Venturi nozzles in a pVTt facility. The calibration results were found to depend on the initial pressure in the collection tank, which reduced the discharge coefficient by 1.17%. The results suggest that vapor condensation in the diffuser section of the CFVN and the inventory volume or collection tank and adsorption of water molecules on the surface of the collection tank are additional humidity effects in a pVTt facility. An empirical model was developed for the humidity effect with the critical pressure for each facility determined from the experimental results. With the humidity correction, the NIM and PTB results compare very well.

Experimental study of aerated cavitation in a horizontal venturi nozzle

The injection of bubbles into an already cavitating flow is a way of influencing the typical cavitating behaviour. The present article deals with experiments on aerated and non-aerated cavitation in a transparent horizontal venturi nozzle. The observations are done by means of a high-speed camera. In such a way the extremely rapid cavitation and cavitation–aeration flows are captured and further analysed. The post-processing techniques is based on the detection of the grey level on the series of images. As a result, three different regimes are identified: sheet cavitation, cloud cavitation and “supercavitation”. Those regimes are further aerated by injecting air bubbles. Standard deviations, time–space diagrams and frequency spectrum based on the vertical distribution of the grey level along a monitored line are plotted for all of the observed regimes. In the pure cavitation cases we obtain statistically symmetrical structures with characteristic lengths and frequencies. On the other hand, with aeration present, the symmetry is broken and characteristic lengths and frequencies are deeply modified, until a complete disappearance when “supercavitation” is reached.

A Practically Validated Intelligent Calibration Circuit Using Optimized ANN for Flow Measurement by Venturi

Design of an intelligent flow measurement technique using venturi flow meter is reported in this paper. The objectives of the present work are: (1) to extend the linearity range of measurement to 100 % of full scale input range, (2) to make the measurement technique adaptive to variations in discharge coefficient, diameter ratio of venturi nozzle and pipe (β), liquid density, and liquid temperature, and (3) to achieve the objectives (1) and (2) using an optimized neural network. The output of venturi flow meter is differential pressure. It is converted to voltage by using a suitable data conversion unit. A suitable optimized artificial neural network (ANN) is added, in place of conventional calibration circuit. ANN is trained, tested with simulated data considering variations in discharge coefficient, diameter ratio between venturi nozzle and pipe, liquid density, and liquid temperature. The proposed technique is then subjected to practical data for validation. Results show that the proposed technique has fulfilled the objectives.

Discharge coefficient equation for critical-flow toroidal-throat venturi nozzles covering the boundary-layer transition regime

A single, simple correlating equation between the discharge coefficient of critical-flow Venturi nozzles (CFVNs) having an ISO 9300 toroidal throat and their Reynolds number is proposed in the Reynolds number range from 2.1×104 to 3.2×107. The equation covers the whole Reynolds number range from laminar to turbulent boundary-layer regimes and can thus be used instead of the two correlating equations defined in ISO 9300 : 2005. The deviation of the discharge coefficients of well-made CFVNs is expected to be less than ±0.2% throughout the Reynolds number range. Tolerances for the diffuser length, inlet curvature and inlet diameter are also proposed. It is shown that the widely-accepted theories that estimate the core flow distribution result in significant error when the inlet curvature is small and that removing the third term in Hall׳s equation results in very good agreement with the experimental data regardless of the magnitude of the inlet curvature. The use of CFVNs with the inlet curvature of 1.0D is discussed in order to reduce the uncertainty owing to undefined boundary-layer transition Reynolds number. A possibility is shown that such a CFVN may not have an apparent boundary-layer transition in the investigated Reynolds number range from 1.5×104 to 2.0×106.

Discharge coefficient of small sonic nozzles

The purpose of this investigation is to understand flow characteristics in mini/micro sonic nozzles, in order to precisely measure and control miniscule flowrates. Experimental and numerical simulation methods have been used to study critical flow Venturi nozzles. The results show that the nozzle?s size and shape influence gas flow characteristics which leading the boundary layer thickness to change, and then impact on the discharge coefficient. With the diameter of sonic nozzle throat decreasing, the discharge coefficient reduces. The maximum discharge coefficient exits in the condition of the inlet surface radius being double the throat diameter. The longer the diffuser section, the smaller the discharge coefficient becomes. Diffuser angle affects the discharge coefficient slightly.