scholarly journals The potential air flow through diver’s breathing apparatus

2021 ◽  
Vol XXIV (1) ◽  
pp. 41-47
Author(s):  
STANCIU T.
Keyword(s):  
Gas Flow ◽  
Cfd Simulation ◽  
Air Flow ◽  
External Pressure ◽  
Gas Flows ◽  
Second Stage ◽  
Breathing Apparatus ◽  
Flow Through ◽  
Laval Nozzles ◽  
Dynamic Phenomena

The gas admission through the divers' breathing apparatus is done with a critical flow. The gas storage pressure is reduced to the value of the external pressure 𝑝𝑒 . The paper approaches the gas-dynamic phenomena that occur when the gas flows through the second stage regulator, respectively: the variable restrictor A (between the seat and the cylindrical piston) and the fixed restrictor B (the orifice of cylindrical piston). The two main pressure restrictors can be considered Laval nozzles. Mathematical modeling of airflow through restrictors was done following the notions of the theory of potential gas flow through tubes and nozzles. The air flow was calculated numerically and by CFD simulation and was experimentally verified at a professional stand for the second stage.

scholarly journals The Viscous and Inertial Flow of Air through Perforated Papers

1989 ◽  
Vol 14 (5) ◽  
pp. 253-260
Author(s):  
RR Baker
Keyword(s):  
Viscous Flow ◽  
Gas Flow ◽  
Air Flow ◽  
Total Flow ◽  
Cellulose Fibres ◽  
Perforation Hole ◽  
Paper Making ◽  
Inertial Flow ◽  
Flow Through ◽  
Cigarette Paper

AbstractInherently porous cigarette paper consists of an interlocking network of cellulose fibres interspersed with chalk particles. Spaces in this matrix are of the order of 1 AAµm wide which is small compared to the paper thickness (usually 20 AAµm to 40 AAµm). However, when cigarette paper is perforated after the paper-making process, e.g. by an electrostatic or mechanical process, the perforation holes are relatively large, usually having mean diameters of the same order of magnitude as the paper thickness. The total flow of air through perforated cigarette paper thus consists of two components: viscous flow through the porous structure of the paper inherent from the paper-making process, and inertial flow through the perforation holes. Since the air flow / pressure relationships due to these two components of flow differ and since the two components are additive, the total flow through perforated paper may be expressed as: Q = Z A P + Z’ A Pn, where Q is the air flow (cm3 min-1), A is the area of paper (cm2) exposed to the flowing air, P is the pressure difference across the paper (kilopascal), Z is the base permeability of the paper due to viscous flow through the spaces inherent from the paper-making process (cm min-1 kPa-1 or Coresta unit), Z’ is the permeability of the paper due to inertial flow through the perforation holes (cm min-1 kPa-1/n) and n is a constant for a given set of perforation holes. This equation adequately describes gas flow through a variety of perforated cigarette and tipping papers. By using different gases, it is confirmed that Z depends on viscous forces and Z’ depends on inertial forces. By examining the flow of air through a large number of papers with perforation holes of different sizes, it is shown that Z’ is dependent on the total area of perforation holes, and that a jet-contraction effect occurs as the air travels through the paper. The parameter n is shown to have a value between 0.5 and 1.0, and this value is related to mean perforation-hole size. The permeability of cigarette paper is defined as the flow of air through the paper when the pressure across the paper is 1 kilopascal. Thus from the above equation the “total permeability” of perforated cigarette paper is equal to Z + Z'.

Nonideal Isentropic Gas Flow Through Converging-Diverging Nozzles

1990 ◽  
Vol 112 (4) ◽  
pp. 455-460 ◽  
Author(s):  
W. Bober ◽  
W. L. Chow
Keyword(s):  
Mach Number ◽  
Gas Flow ◽  
Accurate Solution ◽  
Gas Flows ◽  
Kutta Method ◽  
Runge Kutta Method ◽  
Nonideal Gas ◽  
Reservoir Conditions ◽  
Flow Through ◽  
Isentropic Gas

A method for treating nonideal gas flows through converging-diverging nozzles is described. The method incorporates the Redlich-Kwong equation of state. The Runge-Kutta method is used to obtain a solution. Numerical results were obtained for methane gas. Typical plots of pressure, temperature, and area ratios as functions of Mach number are given. From the plots, it can be seen that there exists a range of reservoir conditions that require the gas to be treated as nonideal if an accurate solution is to be obtained.

Experiments on the Resistance Law for Non-Darcy Compressible Gas Flows in Porous Media

1974 ◽  
Vol 96 (4) ◽  
pp. 353-357 ◽  
Author(s):  
B. A. Masha ◽  
G. S. Beavers ◽  
E. M. Sparrow
Keyword(s):  
Reynolds Number ◽  
Porous Material ◽  
Incompressible Flow ◽  
Gas Flow ◽  
Strong Support ◽  
Reynolds Numbers ◽  
Gas Flows ◽  
Pressure Distributions ◽  
Flow Through ◽  
Compressible Gas

Experiments were performed to examine the resistance law for non-Darcy compressible gas flow through a porous material. A particular objective of the investigation was to determine whether a resistance law deduced from incompressible flow experiments could be applied to flows with significant density changes. To this end, the coefficients appearing in the Forchheimer resistance law were first determined from experiments in the incompressible flow regime. These values were then used in an analytical model employing the Forchheimer resistance law to predict streamwise pressure distributions for subsonic compressible flow through the porous material. Corresponding experimental pressure distributions were measured for flow Reynolds numbers up to 81.6. At the highest Reynolds number of the tests the density changed by about a factor of two along the length of the porous medium. The greatest discrepancy between experimental and predicted pressures at any Reynolds number was 2 percent. This agreement lends strong support to the validity of using the incompressible Forchheimer resistance law for subsonic flows in which density changes are significant.

Numerical Analysis of Flow Behavior Inside the Blast Furnace

2009 ◽  
Author(s):  
Dong Fu ◽  
Fengguo Tian ◽  
Guoheng Chen ◽  
D. Frank Huang ◽  
Chenn Q. Zhou
Keyword(s):  
Blast Furnace ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Furnace Productivity ◽  
Gas Distribution ◽  
Furnace Shaft ◽  
Parametric Studies ◽  
Flow Through

Gas and burden distributions inside a blast furnace play an important role in optimizing gas utilization versus the furnace productivity and minimizing the CO2 emission in steel industries. In this paper, a mathematical model is presented to describe the burden descent in the blast furnace shaft and gas distribution, with the alternative structure of coke and ore layers being considered. Multi-dimensional Ergun’s equation is solved with considering the turbulent compressible gas flow through the burden column. The porosity of each material will be treated as a function of three dimensional functions which will be determined by the kinetics sub-models accordingly. A detailed investigation of gas flow through the blast furnace will be conducted with the given initial burden profiles along with the effects of redistribution during burden descending. Also, parametric studies will be carried out to analyze the gas distribution cross the blast furnace under different cohesive zone (CZ) shapes, charging rate, and furnace top pressure. A good agreement was obtained between the CFD simulation and published experimental data. Based on the results, the inverse V shape is proved to be the most desirable CZ profile.

Structure and Pressure Drop in Particle-Laden Gas Flow Through a Pipe Bend: A Numerical Analysis by the Euler/Lagrange Approach

2009 ◽  
Author(s):  
S. Lai´n ◽  
M. Sommerfeld
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Gas Flows ◽  
Wall Roughness ◽  
Mass Loading ◽  
Particle Collisions ◽  
Pipe Bend ◽  
Flow Through ◽  
Fully Coupled ◽  
Lagrange Approach

The structure of particle-laden gas flows in a horizontal-to-vertical elbow is investigated numerically for analysing the required modelling depth. The numerical computations are performed with the fully coupled Euler-Lagrange approach considering all the relevant forces: drag, gravity-buoyancy and lift forces (slip-shear and slip-rotational). Moreover, interparticle and particle-rough wall collisions are taken into account by means of stochastic approaches. The effect of the different mechanisms, i.e. wall roughness, inter-particle collisions and mass loading, on the flow structure in the bend and the resulting pressure drop are investigated.

Theoretic Analysis of Middle Ear Gas Composition under Conditions of Nonphysiologic Ventilation

1992 ◽  
Vol 101 (5) ◽  
pp. 445-451 ◽  
Author(s):  
Ervin J. Ostfeld ◽  
Alexander Silberberg
Keyword(s):  
Steady State ◽  
Eustachian Tube ◽  
Middle Ear ◽  
Gas Flow ◽  
High Rate ◽  
Gas Flows ◽  
Gas Composition ◽  
Flow Through ◽  
Pressure Changes ◽  
Patulous Eustachian Tube

As gas flows in and out of the nasopharynx, the pressure in that region fluctuates. It drops below or rises above atmospheric pressure, which is itself not constant but is subject to changes in altitude and weather. Such pressure changes in the nasopharynx produce a pumping of gas into and out of the middle ear. The net amount of middle ear gas transferred from or to the nasopharynx will, component for component, in steady state exactly equal the amount of middle ear gas transferred to or from the microcirculation by means of diffusional absorption by (or release from) the mucosa. In the case of a permanently patulous eustachian tube, a single parameter, characteristic of the rate of ventilation through the open eustachian tube, is found to determine the gas composition in the middle ear, whereas in the case of a middle ear ventilated by tympanostomy, two rate-of-ventilation parameters, one for gas flow through the ventilation tube and one for flow through a periodically open eustachian tube, determine the steady state gas composition. A high rate of ventilation favors absorption of oxygen and venting of carbon dioxide from the middle ear in both cases.

The Influence of Exhaust Poppet Valve Gas Flow on Reciprocating Engine Noise

1975 ◽  
Vol 189 (1) ◽  
pp. 461-469 ◽  
Author(s):  
T. J. Williams ◽  
J. B. Cox
Keyword(s):  
Gas Flow ◽  
Combustion Engine ◽  
Flow Characteristics ◽  
Exhaust System ◽  
Gas Flows ◽  
Frequency Spectra ◽  
Reciprocating Engine ◽  
Flow Through ◽  
Field Noise ◽  
Good Agreement

The far field noise generated by cold air flowing through stationary and reciprocating exhaust poppet valves into a cylindrical duct or pipe has been investigated. A method of predicting the intensity and frequency spectrum of the noise generated in such circumstances in terms of the known or assumed geometry and flow characteristics of the valves is presented. Comparisons of the predicted frequency spectra with measured values show good agreement for steady gas flows through stationary valves and for unsteady flow through a simplified exhaust system of a motored single cylinder internal combustion engine.

Heat Transfer Characteristics of Turbulent Gas Flow Through Micro-Tubes

2010 ◽  
Author(s):  
Chungpyo Hong ◽  
Yuki Uchida ◽  
Takaharu Yamamoto ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Gas Flow ◽  
Gas Flows ◽  
Heat Transfer Characteristics ◽  
Total Temperature ◽  
Flow Through ◽  
Turbulent Gas Flow

This paper presents experimental results on heat transfer characteristics of turbulent gas flows though a micro-tube with constant wall temperature. The experiments were performed for nitrogen gas flows through a micro-tube with 242μm in diameter and 50 mm in length. The wall temperature was maintained at 5K, 20K and 30K higher than the inlet temperature by circulating water around the micro-tube, respectively. In order to measure heat transfer rate of gas flow through a micro-tube, the total temperature at a micro-tube exit was measured. The stagnation pressure was chosen in such a way that the Reynolds number ranges from 3000 to 12000. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy. A correlation for the prediction of the heat transfer rate of the turbulent gas flow through a micro-tube was proposed.

scholarly journals Analysis of gas flows in ships turbines

2019 ◽  
Vol XXII (1) ◽  
pp. 318-322
Author(s):  
Aftaniuk V.
Keyword(s):  
Gas Flow ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Experimental Tests ◽  
Gas Flows ◽  
Steam Turbines ◽  
Cfd Modelling ◽  
Preliminary Calculation ◽  
Solid Models ◽  
Modelling Methods

In this paper comparison was made of an experimental study of gas flows and CFD simulation of turbine blades steam turbines for ships. For CFD simulation develop solid models, samples were taken from three blades similarly studied in the experiment. An analysis of experimental data and CFD simulation results of the gas flow near lattice the considered type shows the inappropriateness of their application at supersonic speeds. The calculations performed on the CFD model show that the use of CFD modelling methods allows, at the early stages of designing turbine blades, to select the most optimal (in terms of energy losses) forms of profiles for specific modes of operation of the ship's turbine. Further improvement of the profiles that have passed the preliminary calculation check is advisable to conduct on the basis of more detailed experimental tests to obtain dependences of losses in the lattice, the exit angle of the flow from the parameters of the lattice and the angle of gas flow.

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