Aerodynamic Focusing of Microparticles in Gas Flows With Shock Waves

2013 ◽  
Author(s):  
Alexander Osiptsov ◽  
Irina Golubkina ◽  
Oyuna Rybdylova
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Gas Flow ◽  
Particle Beam ◽  
Gas Flows ◽  
High Concentration ◽  
Interaction Point ◽  
Processing Technologies ◽  
Focusing Effect ◽  
Aerodynamic Focusing

The effect of aerodynamic focusing of microparticles in gas-particle flows is employed mainly for creating collimated particle beams. These beams are used in various technical applications, such as coating, “direct-write”, surface processing technologies, needle-free injections, etc. In this study, we propose and investigate two new flow schemes in which the effect of aerodynamic focusing of small low-inertia particles may be realized in high-speed gas flows with shock waves. The first one is a steady-state dusty-gas flow behind the point of interaction of two crossing shock waves. The convergence of the carrier-phase streamlines and the presence of particle inertia result in the formation of a high-concentration particle beam behind the shock interaction point. In the second flow scheme considered, the particle focusing effect is attributable to the action of the Saffman lateral force, exerting on the particles in boundary layers behind a shock wave travelling in a narrow channel with a constant cross-section. In both cases, the ranges of governing parameters are found for which the focusing is “optimal”, i.e. a very thin collimated beam of microparticles is formed.

Focusing of inertial particles after the shock-wave intersection point

2007 ◽  
Vol 5 ◽  
pp. 145-150
Author(s):  
I.V. Golubkina
Keyword(s):  
Shock Wave ◽  
Mass Concentration ◽  
Gas Flow ◽  
Intersection Point ◽  
Plane Shock ◽  
Inertial Particles ◽  
Dusty Gas ◽  
Focusing Effect ◽  
Aerodynamic Focusing ◽  
Particle Mass Concentration

The effect of the aerodynamic focusing of inertial particles is investigated in both symmetric and non-symmetric cases of interaction of two plane shock waves in the stationary dusty-gas flow. The particle mass concentration is assumed to be small. Particle trajectories and concentration are calculated numerically with the full Lagrangian approach. A parametric study of the flow is performed in order to find the values of the governing parameters corresponding to the maximum focusing effect.

scholarly journals IMPROVING THE EFFICIENCY OF THE FUNCTIONING OF GAS PIPELINES, TAKING INTO ACCOUNT THE STRUCTURAL FEATURES OF GAS FLOWS

2021 ◽  
Vol 447 (3) ◽  
pp. 34-39
Author(s):  
Elman Kh. Iskandarov
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Structural Changes ◽  
Oil And Gas ◽  
Structural Features ◽  
Transportation Systems ◽  
Gas Condensate ◽  
Gas Flows ◽  
Gas Pipelines ◽  
Processing Depth

The multi-phase and different composition of gas flows during the development of offshore oil and gas-condensate fields leads to high costs of energy in the system of in-field storage and transportation of well products. The analysis of the existing storage and transportation systems of gas-condensate mixtures shows that the geophysical nature and complexity of the internal structure of the transported fluids must be taken into account when choosing the mode parameters and calculation schemes of the pipelines. High-speed gas lines can be operated in a so-called "dry" mode, in which the liquid is carried along with the gas, the pipeline profile is relatively straight, without ups and downs. In this case, the formation of so-called "stagnant zones" in the pipeline is excluded. However, if the processing depth of the gas does not allow it to be transported in a single-phase state, then the condensing gas factor manifests itself. The hydraulic characteristics of vertical ups and downs on offshore pipelines are complicated, and pipelines are often filled with water and condensate. As a result, the pressure in the pipeline increases and the location of the collection point for condensing gases away from the production site can cause major problems. If we characterize oil and gas-condensate flows as a dynamic system in which alternating structural changes take place, the question of whether these systems are fractal is of great scientific interest. Based on the change in the fractal value, it is possible to diagnose structural changes during the transportation of various systems, including condensing gases in the pipelines. In this article the modes of change of basic parameters of a gas flow (pressure, flow rate and temperature) on various lines of a gas pipeline for the purpose of the producing of diagnostic criterion for revealing of liquid inclusions as a part of transported gas are investigated in this article. It is established, that in the presence of liquid inclusions at movement of gas flows there are the structural changes peculiar to fluid systems, systems which can be identified by variations of fractal dimensions of flowcharacteristics. Studies have shown that the study of the dynamics of structural changes in gas flows can play a role in diagnosing the formation of liquid phase embryos in gas pipelines. For this purpose, diagnostics for the movement of gas streams accompanied by liquid deposits in the pipelines has been proposed.

scholarly journals Edge Detection and Machine Learning Approach to Identify Flow Structures on Schlieren and Shadowgraph Images

2020 ◽  
pp. paper15-1-paper15-14
Author(s):  
Irina Znamenskaya ◽  
Igor Doroshchenko ◽  
Daria Tatarenkova
Keyword(s):  
Machine Learning ◽  
Shock Wave ◽  
Shock Waves ◽  
Edge Detection ◽  
High Speed ◽  
Gas Flow ◽  
Flow Structures ◽  
Learning Approach ◽  
Wave Detection ◽  
Machine Learning Approach

Schlieren, shadowgraph and other types of refraction-based techniques have been often used to study gas flow structures. They can capture strong density gradients, such as shock waves. Shock wave detection is a very important task in analyzing unsteady gas flows. High-speed imaging systems, including high-speed cameras, are widely used to record large arrays of shadowgraph images. To process large datasets of the high-speed shadowgraph images and automatically detect shock waves, convective plumes and other gas flow structures, two computer software systems based on the edge detection and machine learning with convolutional neural networks (CNN) were developed. The edge-detection software utilizes image filtering, noise removing, background image subtraction in the frequency domain and edge detection based on the Canny algorithm. The machine learning software is based on CNN. We developed two neural networks working together. The first one classifies the image dataset and finds images with shock waves. The other CNN solves the regression task and defines shock wave position (single number) based on image pixels tensor (3-D array of numbers) for each image. The supervised learning code based on example input-output pairs was developed to train models. It was shown, that the machine learning approach gives better results in shock wave detection accuracy, especially for low-quality images with a strong noise level. Software system for automated shadowgraph images processing and x-t curves of the shock wave and convective plume movement plotting was developed.

Modeling Piston-Ring Dynamics, Blowby, and Ring-Twist Effects

1998 ◽  
Vol 120 (4) ◽  
pp. 843-854 ◽  
Author(s):  
T. Tian ◽  
L. B. Noordzij ◽  
V. W. Wong ◽  
J. B. Heywood
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Great Influence ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Gas Flows ◽  
Ring Groove ◽  
Ring Dynamics ◽  
Low Load ◽  
Groove Configurations

A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered, as well as different keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.

scholarly journals Effect of the location of a gas flow control element in an ejector unit on the flow pattern

2020 ◽  
Vol 2020 (3) ◽  
pp. 54-63
Author(s):  
O.D. Ihnatev ◽  
◽  
H.M. Shevelova ◽  
Keyword(s):  
Numerical Simulation ◽  
Flow Control ◽  
Flow Pattern ◽  
Flow Rate ◽  
Gas Flow ◽  
Energy Carrier ◽  
Control Element ◽  
Gas Flows ◽  
Control Parameters ◽  
Processing Technologies

This article is devoted to a numerical simulation of the flow in a jet mill ejector equipped with a gas flow control element. This element is a channel wherefrom an additional gas flow enters the accelerating tube of the ejector. The gas flows in the mill ejector are controlled using the energy of additional gas flows, thus increasing the velocity of the main flow at the outlet of the ejector accelerating tube and producing a protective layer around the tube walls to prevent their wear. At the same time, there is no substantiation for the choice of optimal control parameters, a methodology, or scientific methods for gas flow control in the ejector channels. The purpose of this work is to investigate the effect of the location of the gas flow control element on gas-dynamic ejector performance and the flow pattern in the ejector channels. A numerical study was carried out using the Ansys Fluent software package and the SST k-? turbulence model. In the course of the study, the pressure of the additional gas flow and the distance from the accelerating tube inlet to the energy carrier supply channel were varied. The angle of the additional gas flow was 20 ?. The numerical simulation gave flow patterns in the ejector as a function of the location of the gas flow control element. Streamlines of the additional gas flow were constructed. The article presents the average flow velocity at the accelerating tube outlet and the energy carrier flow rate as a function of the pressure of the additional flow of the energy carrier and the location of the gas flow control element and the maximum values of the average outlet velocity for given pressure ranges. The article substantiates the choice of the gas flow control parameters that maximize the velocity of the mixed flow at the accelerating tube outlet at a minimum gas flow rate. The results may be used in improving material processing technologies.

scholarly journals Selected Mathematical Models Describing Flow in Gas Pipelines

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 478
Author(s):  
Andrzej J. Osiadacz ◽  
Marta Gburzyńska
Keyword(s):  
Differential Equations ◽  
High Speed ◽  
Gas Flow ◽  
Complex Structure ◽  
Hyperbolic Model ◽  
Gas Flows ◽  
Gas Pipelines ◽  
One Dimensional ◽  
Network Operation ◽  
The Mathematical Model

The main aim of simulation programs is to study the behavior of gas pipe networks in certain conditions. Solving a specified set of differential equations describing transient (unsteady) flow in a gas pipeline for the adopted parameters of load and supply will help us find out the value of pressure or flow rate at selected points or along selected sections of the network. Transient gas flow may be described by a set of simple or partial differential equations classified as hyperbolic or parabolic. Derivation of the mathematical model of transient gas flow involves certain simplifications, of which one-dimensional flow is most important. It is very important to determine the conditions of pipeline/transmission network operation in which the hyperbolic model and the parabolic model, respectively, should be used. Parabolic models can be solved numerically in a much simpler way and can be used to design simulation programs which allow us to calculate the network of any structure and any number of non-pipe elements. In some conditions, however, they describe the changes occurring in the network less accurately than hyperbolic models do. The need for analysis, control, and optimization of gas flows in high-pressure gas pipelines with complex structure increases significantly. Very often, the time allowed for analysis and making operational decisions is limited. Therefore, efficient models of unsteady gas flows and high-speed algorithms are essential.

scholarly journals Effect of Local Gas Flow in Full Penetration Laser Beam Welding with High Welding Speeds

2020 ◽  
Vol 10 (5) ◽  
pp. 1867
Author(s):  
Leander Schmidt ◽  
Klaus Schricker ◽  
Jean Pierre Bergmann ◽  
Christina Junger
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Laser Beam Welding ◽  
Deep Penetration ◽  
Gas Flows ◽  
Pressure Balance ◽  
Melt Pool ◽  
Full Penetration ◽  
Loss Of Mass ◽  
Deep Penetration Welding

Spatter formation is a major issue in deep penetration welding with solid-state lasers at high welding speeds above 8 m/min. In order to limit spatter formation, the use of local gas flows represents a technically feasible solution. By using the gas flow, the pressure balance inside the keyhole, and therefore the keyhole stability, is affected. Existing investigations demonstrate a reduction in spatter and pore formation for partial penetration welding up to a welding speed of 5 m/min. However, the effect of the gas flow is not yet clarified for full penetration welding at welding speeds above 8 m/min. By using a precisely adjustable shielding gas supply, the effect of a local gas flow of argon was characterized by welding stainless steel AISI304 (1.4301/X5CrNi18-10). The influence of the gas flow on the melt pool dynamics and spatter formation was recorded by means of high-speed videography and subsequently analyzed by image processing. Schlieren videography was used to visualize the forming flow flied. By the use of the gas, a change in melt pool dynamics and gas flow conditions was observed, correlating to a reduction in loss of mass up to 70%. Based on the investigations, a model of the acting effect mechanism was given.

Three-Dimensional Imaging through Shock-Waves at Ultra-High Speed.

2018 ◽  
Author(s):  
Yi Chen Mazumdar ◽  
Michael E. Smyser ◽  
Jeffery Dean Heyborne ◽  
Daniel Robert Guildenbecher
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Three Dimensional ◽  
Three Dimensional Imaging ◽  
Ultra High Speed
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