scholarly journals Distal projection of insufflated gas during tracheal gas insufflation

2002 ◽  
Vol 92 (5) ◽  
pp. 1843-1850 ◽  
Author(s):  
Christopher S. Carter ◽  
John R. Hotchkiss ◽  
Alexander B. Adams ◽  
Mary K. Stone ◽  
John J. Marini
Keyword(s):  
Endotracheal Tube ◽  
Gas Injection ◽  
Central Projection ◽  
Flow Rates ◽  
Tracheal Gas Insufflation ◽  
Mixing Behavior ◽  
Expired Gas ◽  
Percent Nitrogen ◽  
Direction Opposite ◽  
Substantial Distance

Tracheal gas insufflation (TGI) flushes expired gas from the ventilator circuitry and central airways, augmenting CO2 clearance. Whereas a significant portion of this washout effect may occur distal to the injection orifice, the penetration and mixing behavior of TGI gas has not been studied experimentally. We examined the behavior of 100% oxygen TGI injected at set flow rates of 1–20 l/min into a simulated trachea consisting of a smooth-walled, 14-mm-diameter tube. Models incorporating a separate coaxial TGI injector, a rough-walled trachea, and a bifurcated trachea were also studied. One-hundred percent nitrogen, representing expiratory flow, passed in the direction opposite to TGI at set flow rates of 1–25 l/min. Oxygen concentration within the “trachea” was mapped as a function of axial and radial position. Three consistent findings were observed: 1) mixing of expiratory and TGI gases occurred close to the TGI orifice; 2) the oxygenated domain extended several centimeters beyond the endotracheal tube, even at high-expiratory flows, but had a defined distal limit; and 3) more distally from the site of gas injection, the TGI gas tended to propagate along the tracheal wall, rather than as a central projection. We conclude that forward-directed TGI penetrates a substantial distance into the central airways, extending the compartment susceptible to CO2 washout.

Clarification of Performance Curve Instability Mechanism Using Large Eddy Simulation of Internal Flow of a Mixed-Flow Pump

2015 ◽  
Author(s):  
Isao Hagiya ◽  
Chisachi Kato ◽  
Yoshinobu Yamade ◽  
Takahide Nagahara ◽  
Masashi Fukaya
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Low Flow ◽  
Performance Curve ◽  
Instability Mechanism ◽  
Positive Slope ◽  
Mixed Flow ◽  
Flow Rates ◽  
Direction Opposite ◽  
Flow Pump

We analyzed the internal flows of a test mixed-flow pump exhibiting performance curve instability at low flow rates by using LES to clarify the performance curve instability mechanism. The LES was conducted using the open source software FrontFlow/blue [1]. In particular, we investigated in detail the flows at the flow rates, where the head curve had a positive slope under low flow rate condition. We clarified that Euler’s head drop caused by a stall near the tip of the rotor-blades is a dominant factor at the instability of the test pump. At the bottom point of the positive slope of the head curve, stall regions covered all the rotor-blade passages on the tip side. The drop of the angular momentum in the impeller caused by the stall on the leading edge side exceeds the increment caused by the decrease in the flow rate on the trailing edge at the bottom point of the positive slope. At the middle point of the positive slope of the head curve we also found regions with low-velocities in some blade passages. Such regions, namely stall cells, rotated around the impeller for one revolution while the impeller rotated almost about 20 revolutions in the direction opposite to the impeller’s rotation. The region with low-velocity first appears at the trailing edge and expands toward the leading edge. The angle of attack of the neighbouring blade in the direction opposite to the rotation of the blade increases and that blade pitch begins to stall. When that blade pitch is fully stalled, it is no longer loaded and the positive pressure gradient in that blade pitch decreases. The blade pitch is most likely to accept the excess flow. It recovers from the stalled state.

Submerged Gas Injection in Microgravity

2002 ◽  
Author(s):  
J. Carrera ◽  
R. N. Parthasarathy ◽  
S. R. Gollahalli
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Gas Flow ◽  
Capillary Tube ◽  
Bubble Formation ◽  
Gas Injection ◽  
Flow Regimes ◽  
Flowing Liquid ◽  
Flow Rates ◽  
Reduced Surface

The effects of buoyancy on the flow regimes of submerged gas injection were studied in this investigation. A capillary tube submerged in water was used for gas injection in microgravity and terrestrial conditions, and the resulting flow regimes and bubble sizes were documented. The effects of liquid co-flow and reduced surface tension were also analyzed. Under reduced gravity, three flow regimes were observed over the range of conditions tested. At low gas flow rates, the bubbles did not detach from the injector, forming an interconnected bubble cluster that adhered to the injector. Single bubbles started detaching and moving away from the injector when the Weber number reached a value around 3. At gas flow rates corresponding to a Weber number value of 10, the bubble coalescence regime was observed near the injector. It was found that the absence of buoyancy prevented the formation of the jetting regime. For all gas throughputs, the co-flowing liquid aided the detachment of the bubbles, resulting in the generation of more uniform bubbles than in quiescent liquids. The presence of co-flow resulted in a smaller bubble size accompanied by an increased frequency of bubble formation. Reduced surface tension produced a similar effect, resulting in smaller bubbles.

Cuffed endotracheal tubes in cats

2020 ◽  
Vol 25 (3) ◽  
pp. 1-3
Author(s):  
David Yates ◽  
Albert Holgate
Keyword(s):  
Endotracheal Tube ◽  
Gas Flow ◽  
Assisted Ventilation ◽  
Flow Rates ◽  
Endotracheal Tubes ◽  
Cuffed Endotracheal Tube ◽  
Volatile Agents

A cuffed endotracheal tube may improve the airway seal in anaesthetised feline patients, compared to use of an uncuffed tube. This may improve capnography and decrease theatre pollution with volatile agents. However, two significant risks are associated with the technique. First, over-inflation of the cuff could occur, with associated iatrogenic tracheal damage; this may be prevented by use of a cuff manometer for inflation. Second, as a result of the improved seal, barotrauma may be more likely with high gas flow rates and assisted ventilation.

Simultaneous gas and water flow in a damage-susceptible bedded argillaceous rock

2015 ◽  
Vol 52 (1) ◽  
pp. 18-32 ◽  
Author(s):  
T.S. Nguyen ◽  
A.D. Le
Keyword(s):  
Water Flow ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Gas Injection ◽  
Injection Pressure ◽  
Opalinus Clay ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Inherent Anisotropy

A mathematical model that couples the governing and constitutive equations of two-phase flow and mechanical equilibrium has been developed to simulate gas injection tests for both laboratory- and field-scale experiments. The model takes into consideration the inherent anisotropy of sedimentary rocks due to bedding by including an anisotropic elastoplastic model for the mechanical process and using an anisotropic permeability tensor for the flow processes for both water and gas. The gas and water flow rates are assumed to follow Darcy’s law. The relative permeability of each phase and their respective degrees of saturation are represented by the Van Genuchten’s functions. We simulated laboratory and field gas injection experiments in Opalinus clay, a candidate geological formation for the geological disposal of radioactive wastes. The numerical results show good agreement with the experimental data measured in these tests in terms of two-phase flow regimes and hydromechanical response at various monitoring locations. Damage zones, either pre-existing due to excavation or induced by high gas injection pressure, are shown to clearly influence the gas flow rates and directions and would need special consideration in the design and safety assessment of the repository system.

Modes of Tracheal Gas Insufflation: Comparison of Continuous and Phase-specific Gas Injection in Normal Dogs

1993 ◽  
Vol 148 (3) ◽  
pp. 562-568 ◽  
Author(s):  
William C. Burke ◽  
Avi Nahum ◽  
Sue A. Ravenscraft ◽  
George Nakos ◽  
Alexander B. Adams ◽  
...  
Keyword(s):  
Gas Injection ◽  
Tracheal Gas Insufflation

scholarly journals Gas Turbine Driven Reciprocating Compressors for a Natural Gas Storage Plant

1988 ◽  
Author(s):  
Martin Urban ◽  
Hubert Andrée
Keyword(s):  
Natural Gas ◽  
Gas Injection ◽  
Gas Storage ◽  
West Germany ◽  
Storage Facility ◽  
Working Capacity ◽  
Natural Gas Storage ◽  
Flow Rates ◽  
Expansion Phase ◽  
Wide Range

A major expansion phase is underway at the Ruhrgas natural gas storage plant at Epe on the border between West Germany and the Netherlands. The plant already has 8 caverns with a total working capacity of approx. 350 × 106 m3 (n). 28 caverns are to be added, to bring the total to approx. 1.0 × 109 m3 (n). In view of the increase in capacity, it was necessary to raise the power installed for driving gas compressors from the existing figure of approx. 3,000 kW to a total of 12,000 kW in phase II. A minimum of 2 units were required for this figure of 9,000 kW. Epe is already the second largest natural gas storage facility in West Germany and is designed to store both low BTU and high BTU natural gas. The facilities are operated at a wide range of pressures and flow rates. The new compressor units will be used only for gas injection at well head pressures of up to 200 bar.

Study of Permissible Flow Rate and Mixing Efficiency of the Micromixer Devices

2018 ◽  
Vol 17 (1) ◽  
Author(s):  
K Karthikeyan ◽  
L Sujatha
Keyword(s):  
Flow Rate ◽  
Low Cost ◽  
Microfluidic Channel ◽  
Low Flow ◽  
Mixing Efficiency ◽  
Flow Rates ◽  
Lab On Chip ◽  
Serpentine Channel ◽  
Mixing Behavior ◽  
On Chip

AbstractThis paper deals with design, simulation, fabrication, analysis of mixing efficiency and thin film bonding stability of the micromixer devices with different flow rates used for lab on chip applications. The objective of the present study is to achieve complete mixing with low flow rate and less pressure drop in low cost polymer microfluidic devices. This paper emphasis the design, simulation and fabrication of straight channel micromixer, serpentine channel micromixer with and without quadrant shaped grooves to study the mixing behavior by the effect of structural dimensions of the microfluidic channel at different flow rates. The designed micromixers were tested with varying rates of flow such as 1, 10, 25, 50, 75 and 100 µL/min.

Airway thermal volume in humans and its relation to body size

1997 ◽  
Vol 83 (2) ◽  
pp. 668-668 ◽  
Author(s):  
Vladimir B. Serikov ◽  
E. Heidi Jerome ◽  
Neal W. Fleming ◽  
Peter G. Moore ◽  
Frederick A. Stawitcke ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Body Size ◽  
Endotracheal Tube ◽  
Time Constant ◽  
Body Height ◽  
The Body ◽  
Mechanically Ventilated ◽  
Volume Ventilation ◽  
Expired Gas ◽  
The Relationship

Serikov, Vladimir B., E. Heidi Jerome, Neal W. Fleming, Peter G. Moore, Frederick A. Stawitcke, and Norman C. Staub.Airway thermal volume in humans and its relation to body size. J. Appl. Physiol. 83(2): 668–676, 1997.—The objective of this study was to investigate the influence of volume ventilation (V˙e) and cardiac output (Q˙) on the temperature of the expired gas at the distal end of the endotracheal tube in anesthetized humans. In 63 mechanically ventilated adults, we used a step decrease in the humidity of inspired gas to cool the lungs. After change from humid to dry gas ventilation, the temperature of the expired gas decreased. We evaluated the relationship between the inverse monoexponential time constant of the temperature fall (1/τ) and eitherV˙e orQ˙. WhenV˙e was increased from 5.67 ± 1.28 to 7.14 ± 1.60 (SD) l/min ( P = 0.02), 1/τ did not change significantly [from 1.25 ± 0.38 to 1.21 ± 0.51 min−1, P = 0.81]. In the 11 patients in whom Q˙ changed during the study period (from 5.07 ± 1.81 to 7.38 ± 2.45 l/min, P = 0.02), 1/τ increased correspondingly from 0.89 ± 0.22 to 1.52 ± 0.44 min−1( P = 0.003). We calculated the airway thermal volume (ATV) as the ratio of the measured valuesQ˙ to 1/τ and related it to the body height (BH): ATV (liters) = 0.086 BH (cm) − 9.55 ( r = 0.90).

Mixing behavior in the RH degasser with bottom gas injection

Vacuum ◽  
2016 ◽  
Vol 130 ◽  
pp. 48-55 ◽  
Author(s):  
Gujun Chen ◽  
Shengping He
Keyword(s):  
Gas Injection ◽  
Mixing Behavior
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