Outlet Nozzle Research Articles

Vortex tube modelling: outlet parameter dependencies of cold air production

A model of a counterflow vortex tube has been prepared to study the dependence of the influence of the parameters of cold and hot outlets on the production of cold air. For a fixed geometry of the vortex tube, a simulation is performed with an independent change of the length of the cold outlet nozzle, the angle of the widening of the cold outlet nozzle, and the hot outlet area. In a series of experiments, the pressure of air supplied to the inlet varies in order to take into account the possible effects of computational and model errors. An anomalous increase in the temperature of the outgoing air was observed with a hot outlet area of ∼30 cm2. Conclusions were drawn about the range of reasonable values of the outlet parameters for the considered configuration of the vortex tube.

Supersonic jet and nozzle flows in uniform-flow and free-vortex aerodynamic windows of gas lasers

The mathematical models and computational tools for design, analysis and predictions of supersonic jet and nozzle flows in the aerodynamic windows of high-power gas lasers are considered. The steady-state Euler equations describing strong shock waves, contact discontinuities, rarefaction waves and their interactions are solved with the finite-volume solver and space-marching method. The results of numerical simulation of steady-state supersonic flows of inviscid compressible gas in nozzles and under- and over-expanded jets are obtained and analyzed for different pressure ratios in the laser cavity and ambient atmosphere. The flowfields corresponding to the uniform velocity profile and free-vortex velocity profile in the outlet nozzle boundary are compared. Nozzle profiling tools are developed on the basis of numerical solution of a sequence of direct problems. The aerodynamic performance of the window is evaluated in terms of the simulated laser cavity pressure and plenum pressure of the free-vortex supply nozzle. The pressure support characteristic for the aerodynamic window is established by determining the ambient to cavity pressure ratio over a range of aerodynamic window supply pressures.

The results of the analysis of the continuous input of additives in the lubricating system of the engine operating on gaseous fuel

The issue of ensuring the reliability of internal combustion engines is an urgent complex task, solved in different directions. Important among which are the operating conditions, the type of fuel used, monitoring the condition of engine oils, as well as the rationale for the service life of oils. When improving the design of tractors, it is necessary to take into account the issue of increasing their reliability and durability during operation. The studies show that 40-45 % of failures of agricultural machinery are caused by engine breakage. It is rational to solve the problem of improving the reliability of the engine, determining the state of the aggregates and machine parts on the content of wear products in the oil during engine operation, and making informed decisions to improve the condition of the oil. In order to improve the performance properties the additives are used. In order to determine the effect of the continuous use of additives to the oil, a cylinder was designed, comprising a housing, a cylindrical element for the additive, a cap, an inlet nozzle and an outlet nozzle. The element located inside the housing is filled with an additive. Engine oil lubrication system is supplied from the outside, i.e. in the annular gap between the housing and the element for the additive. In the housing, due to the temperature difference, the process of oil diffusion and additives take place. The purpose of the development of the laboratory setup was to study the influence of external factors on the process of continuous input of additives and the determination of their rational values. Studies have shown that the base number with continuous input of additives increased 1,5 times higher compared to samples of oils, used without a device for continuous input of additives. A device for introducing the additive with a filter element was tested. The operating mode of the installation was set according to the results of studies T = 85 °C, ν = 2 m/s and the concentration of mechanical impurities was 0,25 %. Operational tests of the device were carried out over a period of time until the base number dropped below 2 mgKOH/g. It follows that the oil life cycle increases on average by 15-20 %.

DEVELOPMENT AND APPLICATION OF ULTRASONIC INSPECTION EQUIPMENT FOR THE WELD OF STEAM GENERATOR OUTLET NOZZLE IN AP1000 NPP

For AP1000 NPP, the connection weld between the steam generator and main pump is the only butt weld for the main equipment. This weld works in high temperature, high pressure, high vibration etc.. It has important significance and necessity to ensure its integrity by in-service inspection. The outlet nozzle of the steam generator is a highly radioactive area and is usually inspected from the outside. According to requirements of ASME-2004, ultrasonic inspection should be carried out more than 1/3 of thickness from inner wall , so ultrasonic probes must approach the weld from inner wall of the nozzle, one kind of special inspection equipment should be developed. It is difficult to design the inspection equipment because of the high irradiation environment, risk of internal contamination, small inlet size for equipment, large nozzle diameter to be inspected. Besides, it has a long distance between equipment installation and inspected weld, and is crossed-axis in space. In order to meet inspection needs, developed inspection equipment has 10 moving joints and multiple parts, each part is connected by fast connection structure. Installation personnel install inspection equipment outside of the steam generator manhole, then remotely control 10 moving joints to achieve inspection equipment's carrying, positioning, fixing and scan process, completing ultrasonic testing of the weld internally. Inspection equipment has been applied to Unit 1 and 2 of Sanmen NPP and Unit 2 of Haiyang NPP in China.

Development of an experimental laboratory sample of foam extinguishing system using compressed air (CAFS)

The analysis of known structures of foam generating systems with compressed air, as well as the results of research on operational experiments, tests and research of systems carried out abroad, allowed to formulate basic principle requirements to technological and constructive parameters of foam generating systems with compressed air.
 The general trend in the design of various structures, especially complex, built on the internal interaction of individual structural units – is the development of a mathematical model, preceding a constructive solution and often is the calculated basis for them. The created mathematical model of the process of foaming made it possible to determine the dependence of the quality of the foam obtained on the structural and technological parameters. On the basis of the developed mathematical model of foaming, a principal scheme of the process is proposed and a small-sized test facility is created for studying the possibilities of obtaining a compression foam according to the proposed scheme. The peculiarities of the work are an attempt to obtain compression foam according to the proposed scheme with the use of domestic general purpose foam generators using the modernized existing portable fire extinguishing equipment, which is at the disposal of fire units of Ukraine. Particular attention is paid to the analysis of development of small-sized mobile and portable plants, which can be used as an addition to existing fire-fighting equipment. During the experiments, the variables were the brands and concentrations of foam generators, the magnitude of air pressure in the system, and the ratio of water to air. The dependence of the quality of the foam on the change in pressure on the outlet nozzle was established, therefore, during each experiment it was controlled and maintained constant during its conduct. As a result of previous tests, the possibility of obtaining a compression foam according to the proposed scheme with the use of synthetic domestic general purpose foam generators with the use of existing fire equipment has been confirmed. The following are ways of developing work.

Failure analysis of an oil refinery sour water stripper overhead piping loop: Assessment and mitigation of erosion problems

This study investigated the integrity of the outlet nozzle and elbow of the piping system downstream the finfan cooler in sour water stripping unit. The piping system in these locations experienced severe thinning and occasional leaks. The unit was modelled using process simulation software with the use of the appropriate thermodynamic methods for electrolyte models to accurately estimate the flow rates, properties in vapour and liquid phases in the piping system. The results from the process simulation were subsequently used in the Computational Fluid Dynamics (CFD) simulation. The CFD simulation results matched the erosion pattern that caused the loss of wall thickness. The eroded nozzles were also visually and optically examined using scanning electron microscopy (SEM) and Energy Dispersion X-ray (EDX). The results have indicated that the erosion is inevitable regardless of the fluctuation in the throughputs to the unit. Iron sulfide, indicative of the synergy between erosion and corrosion, was observed in the pipes elbows. For mitigation, an option has been recommended to change the operating mode of the finfan cooler so as to alleviate alloy change.

The dependence of the Ranque–Hilsch effect on the cold outlet geometry

The effect of such parameters of the cold outlet nozzle of the counter flow vortex tube as the length and widening angle on temperature separation is investigated. Mathematical model of gas dynamics is written with viscosity component. Computational simulation is performed in the OpenFOAM package, using the sonicFoam solver. It is shown that the temperature of the exhaust air decreases along the cold exit nozzle. The presence of the angle of widening of the nozzle affects the amount of cooling, but is not the root cause of the effect. The nonmonotonic dependence of the temperature of the exhaust gas on the length of the cold exit nozzle is demonstrated. When studying the effect on the temperature of the widening angle of a cold-exit nozzle at a fixed length, it was shown that at a fixed volume flow rate, a pronounced non-monotonic dependence is observed, while at a constant pressure drop, there is no non-monotony down to the maximum considered angle.

NUMERICAL RESEARCH OF THE MOISTURE CONDENSATION ELIMINATION IN THE CABIN OF THE UNIFIED TECHNOLOGICAL ELECTRIC TRANSPORT VEHICLE

Introduction. This article deals with the problem of moisture condensation inside the cabin of the technological electric transport vehicle. The hypothesis of using the forced air ventilation in the cabin is substantiated, by which such problem could be solved.Materials and methods. The article describes the application of the ANSYS Fluent Software Package to assess the effect of the location and shape of the ducts on the ventilation process inside the cabin. Accordingly, the key stages of air flow modeling in this program are considered.Results. The main content of the research is to analyze the modeling airflow process in the cabins with a different configuration of inlet and outlet nozzles. Therefore, basing on the analysis of the obtained airflow velocity contours, the conclusion is made about the rational arrangement of the inlet and outlet channels.Discussion and conclusions. The conclusion is made about the necessity of the further research that would refer to creating a three-dimensional model of the cabin. The results of the research as well as resolutions are taken into account.

Numerical investigation of a novel manifold micro-pin-fin heat sink combining chessboard nozzle-jet concept for ultra-high heat flux removal

In this paper, a novel heat sink combining the manifold flow distributor, impinging nozzle-jet, and micro-pin-fin concepts is proposed. The flow distribution structure of the heat sink is inspired by black and white fields of the chessboard. Every inlet nozzle is surrounded by four outlet nozzles and vice versa. A 3-dimensional numerical simulation model of the basic heat sink structure is introduced to investigate the thermal and hydrodynamic performances. Several configurations with different pin-fin and nozzle geometries and its sensitivity to the geometrical parameters are discussed for optimization. Designs with different numbers of pin-fins in the unit cell of heat sink are also compared. The results show that, for a 2 × 2 cm2 chip or photovoltaic, a total thermal resistance of 9.37 × 10−6 Km2/W is achieved at a flow rate of 1 L/min and a pressure drop of 4928 Pa. A maximum cooling capacity of 700 W/cm2 can be satisfied with the temperature difference between the fluid inlet and chip of 65.5 K, and the temperature non-uniformity of the heating surface of only 2.33 K. The numerical results indicate that the novel heat sink shows great advantages of both uniform flow distribution and ultra-high heat flux cooling.

Analysis of Fatigue–Creep Crack Growth in the Superheater Header of a Power Plant Boilers and Estimation of Its Remaining Lifetime

As superheater header is exposed to high pressure and temperature in power plant boilers, it is one of the most sensitive parts in a power plant.Cracks may form where tubes and main steam outlet (nozzle) are connected to reservoir. This article examines a quarter-circle crack at the corner of a nozzle junction and its propagation steps under the influence of simultaneous interaction of creep and fatigue. Header loading in each cycle includes transient steps (increase and decrease in temperature and pressure) at the beginning and at the end of a cycle and intermediate steady state (fixed pressure and temperature) during operation. For crack growth calculations, stress distribution in a track-free part was calculated. Fatigue–creep crack growth was achieved using crack growth rules and the remaining lifetime was obtained. Research result shows that creep phenomenon is responsible for maximum crack growth.

Numerical and experimental study of flow distribution in tubular space of fin-and-tube heat exchanger with modified inlet manifold

This paper presents the experimental and numerical investigation of flow distribution in the tubular space of cross-flow fin-and-tube heat exchanger. The tube bundle with two rows arranged in staggered formation is considered. A modified heat exchanged manifold, with inlet nozzle pipe located asymmetrically is considered. The outlet nozzle pipe is located in the middle of the outlet manifold, with a standard shape. An experimental stand allows one to investigate the volumetric flow rate in heat exchanger tubular space using the ultrasonic flowmeters. Various inlet mass flow rate i.e. 3 m3/h, 4 m3/h and 5 m3/h are considered. The experimental results are compared with CFD simulation performed in ANSYS CFX program using the SSG Reynolds Stress turbulence model. A relatively good agreement is found for tube Re numbers varied from 1800 to 3100.

Experimental investigation of five parallel plane jets with variation of Reynolds number and outlet conditions

This article describes an experimental investigation in the near field of five parallel plane jets. The study applies 2D Particle Image Velocimetry (PIV) for ventilated and unventilated jets, where ventilated means exiting into a duct with expansion ratio 3.5 and unventilated means exiting to the free atmosphere. Results are presented for Reynolds numbers 1408, 5857 and 10510. The Reynolds number is calculated for the middle channel and is based on the height of the nozzle (channel) equivalent diameter 2h. All characteristic regions of the methodology to describe multiple interacting jets are observed by the PIV measurements - converging, merging and combined. Each of the five parallel channels has an aspect ratio of 25 defined as nozzle width (w) to height (h). The channels have a length of 185 times the channel height guaranteeing a fully developed velocity profile at the exit from the channel. Spacing between the single plane jets is 3 times the channel height. The near field of multiple mixing jets is depended on outlet nozzle geometry. Blunt geometry of the nozzle was chosen (sudden contraction).

Numerical investigation of flow distribution in tubular space of fin-and-tube heat exchanger

This paper presents the experimental and numerical investigation of flow distribution in the tubular space of cross-flow fin-and-tube heat exchanger. The tube bundle with two rows arranged in staggered formation is considered. A standard heat exchanged manifold, with inlet nozzle pipe located asymmetrically is considered. The outlet nozzle pipe is located in the middle of the outlet manifold. A developed experimental setup allows one to measure volumetric flow rate in heat exchanger tubes using the ultrasonic flowmeters. The measurement results are then compared with CFD simulation in ANSYS CFX code using the SSG Reynolds Stress turbulence model, and a good agreement is found for tube Re numbers varied from 1800 to 3100.

Experimental study of the diffusion-controlled corrosion of copper in the bottom of a jet stirred reactor

Abstract Jet stirred tank reactors are usually preferred to mechanically stirred tank reactors in the case of high pressure stirred tank reactors in order to avoid the mechanical problems inherent with mechanically agitated reactors. Owing to the impact force exercised by the fluid jet on the tank bottom, the tank bottom is subjected to severe corrosion. The aim of the present work is to address this problem using an accelerated system which simulates natural diffusion-controlled corrosion of metals. Diffusion-controlled corrosion of a fixed copper disc, at the bottom of a cylindrical tank, under a single phase forced jet flow of acidified dichromate solution was investigated. Variables studied were: physical properties of the solution, solution velocity through different diameters of jet nozzle, distance between the jet outlet nozzle and the copper disc surface; and the effect of using a drag reducing polymer. An overall correlation was obtained: Sh = 0.579 Sc 0.33 Re 0.975 (h/d) 0.049 valid for 850 < Sc < 1322, 1852 < Re < 5000 and 0.3 < h/d < 1.2. Addition of polyethylene oxide as a drag reducing polymer was found to diminish the rate of corrosion under single phase forced jet flow by an amount depending on the operation conditions.

Effect of Mechanical Heterogeneity on the Crack Driving Force of a Reactor Pressure Vessel Outlet Nozzle DMW Joint

The welding mechanical heterogeneity, load complexity, material and geometrical structure makes it very difficult to assess the structural integrity of dissimilar metal weld (DMW) joints. Based on a numerical simulated approach of the continuous change of material mechanical property in the buttering layer, a reactor pressure vessel (RPV) outlet nozzle DMW joint with service loads is studied, effect of mechanical heterogeneity on the stress-strain field and stress triaxiality at the semi-elliptical surface crack front are discussed. The analyses show that once the crack extends into the high hardness zone of Alloy 182 buttering, the strain decreases sharply, the strain gradient increases and the crack propagation slows down. The influence of strength mismatch on the stress triaxiality at the shallow crack front is greater than that at the deep crack front. The interaction between strength mismatch and crack depth directly affects the crack growth direction.

Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling

This article focuses on combustion instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, and outlet nozzle), while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, and circular nozzle at the outlet). A large eddy simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, dynamic mode decomposition (DMD) is used to visualize, analyze, and model the complex phasing between different processes affecting the reacting zones. Using these data, a zero-dimensional (0D) modeling of the premixed flame and of the diffusion flame is proposed. These models provide an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

Near fields of gasper jet flows with wedged nozzle in aircraft cabin environment

The geometry of the outlet nozzle has a direct effect on the near fields of turbulent jets. An attempt is made to modify the gasper jet nozzle by adding wedges of different sizes. The near fields of the wedged gasper jets are measured by a hot-wire anemometer. For the with-wedges cases, the mean velocity exhibits a more rapid decay in the axial direction, and the turbulent intensity is attenuated after the “second potential core.” The higher-order statistics, such as skewness and kurtosis, indicate no obvious difference in the downstream region. As the turbulent structures are formed, the energy spectra indicate that their average energy increases under the wedges' perturbation. Then, the anti-axial-symmetry of the transition flows is observed in two characteristic planes. The mean velocity does not exhibit a significant difference between the two planes, but the turbulent intensity in the perturbed plane embodies the wedges' influence. The wedged nozzle affects the energy intensity and diffusion angle of the turbulent structures in the perturbed plane, and the difference from the unperturbed plane is confirmed by the discrepancy spectra. Furthermore, the anti-axial-symmetry is characterized by turbulent intermittency and entrainment. The turbulent intermittency in the perturbed plane performs with a lower value in the near-nozzle region, and evolves into axial-symmetry in the further downstream region. For turbulent entrainment, the entrainment ratio manifests that wedged nozzle reduces the flow mass in the entrainment of ambient air in the downstream region.

Development and Validation of a Stationary Water-Spray Cleaning System for Concentrated Solar Thermal (CST) Reflectors

Abstract This study presents a novel analysis of a non-contact cleaning system for Concentrated Solar Thermal (CST) reflectors. The analysis is essentially divided in two parts, the first aims at developing a robust computational fluid dynamic model of a stationary water-spray impingement upon flat surfaces to investigate CST flat reflector cleaning techniques. An in-depth investigation on shear stress profiles obtained at different inlet pressure levels and standoff distances, with impinging angle set at 90°, has been developed with ANSYS CFX V 15.0. Findings outline that cleaning effectiveness, as determined by the generation of fluid flow shear stresses on the target surface, is improved as inlet pressure increases in the optimal standoff distance range of 5D-26D, with D as outlet nozzle diameter. Beyond 26D, the water-jet loses cleaning ability due to insufficient jet velocity whereas before 5D backward flows and turbulent eddies obstruct the central jet-flow of the cleaning system. The second part of this analysis focuses on the validation of the fluid dynamic model through the comparison of Smedley’s and Young’s experimental tests. A normalisation of shear stress (τ/τmax) and radial distances (r/H) has been utilised to compare flows characterised by different nozzle types, standoff distances and measures of computational domains.

Enhancement of thin air jets produced by ring-shaped dielectric barrier discharges using an auxiliary electrode

A ring-shaped dielectric barrier discharge (DBD) was explored as a small form factor ionic wind device. Using a concentric ring electrode geometry, the DBD produced a converging ionic wind that leads to a vertical flow away from the DBD electrodes. The vertical flow was channeled through an outlet nozzle to produce a thin air jet, and a grounded auxiliary electrode was placed at the nozzle to enhance the exit velocity. The inner diameter of the ring-shaped DBD electrode and the auxiliary electrode ranged 3.18–9.54 mm and 1.0–4.0 mm, respectively. Results showed that the auxiliary electrode generated an ionic wind velocity up to 3.7 m/s and increased the conversion efficiency from discharge to flow power by a factor of 30 by strengthening the electric field where the ions are accelerated.

Natural oscillations of a gas in an elongated combustion chamber

For the analysis of the frequencies and shapes of the natural oscillations of a gas in an elongated rectilinear combustion chamber, this chamber can be treated as a kind of an organ pipe that has the following specific features:1. the chamber has an inlet and outlet nozzles;2. a gas mixture burns in the combustion chamber;3. the combustion materials flow out from the outlet nozzle;4. the gas flows in such a way that its velocity in the larger part (closer to the outlet nozzle) of the chamber exceeds the speed of sound (Mach number M > 1). There are only separate domains (one or several), where M < 1.The excitation of the natural oscillations of the gas and an increase in the amplitude of such oscillations can lead to instability of the combustion process [1].