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Chamber pressure

About: Chamber pressure is a research topic. Over the lifetime, 2988 publications have been published within this topic receiving 30725 citations.


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Journal ArticleDOI
TL;DR: In this paper, a collapsible artificial anterior chamber model was used to simulate the postocclusion surge in the real eye during cataract surgery, and peak volume fluctuation (mL), half volume recovery time (s), and volume fluctuations integral value (mL × s) were proposed as realistic indicators to characterize the postoclusion surge performance.
Abstract: Purpose To propose an alternative method to characterize postocclusion surge using a collapsible artificial anterior chamber to replace the currently used rigid anterior chamber model. Setting Fundacion Oftamologica Los Andes, Santiago, Chile. Methods The distal end of a phacoemulsification handpiece was placed inside a compliant artificial anterior chamber. Digital recordings of chamber pressure, chamber volume, inflow, and outflow were performed during occlusion break of the phacoemulsification tip. The occlusion break profile of 2 different consoles was compared. Results Occlusion break while using a rigid anterior chamber model produced a simultaneous increase of chamber inflow and outflow. In the rigid chamber model, pressure decreased sharply, reaching negative pressure values. Alternatively, with the collapsible chamber model, a delay was observed in the inflow that occurs to compensate the outflow surge. Also, the chamber pressure drop was smaller in magnitude, never undershooting below atmospheric pressure into negative values. Using 500 mm Hg as vacuum limit, the Infiniti System (Alcon) performed better that the Legacy (Alcon), showing an 18% reduction in peak volume variation. Conclusions The collapsible anterior chamber model provides a more realistic representation of the postocclusion surge events that occur in the real eye during cataract surgery. Peak volume fluctuation (mL), half volume recovery time(s), and volume fluctuation integral value (mL × s) are proposed as realistic indicators to characterize the postocclusion surge performance. These indicators show that the Infiniti System has a better postocclusion surge behavior than the Legacy System.

20 citations

Patent
24 Jan 1967
TL;DR: In this paper, a valve for controlling the flow of high pressure fluid and adapted to have a fully closed, intermediate, and fully open state, comprises a housing 12 having disposed therein, and between an inlet 16 and outlet 26, a chamber 28, the chamber being defined by a conical wall portion 31, a cylindrical wall portion 30 and a piston 38 which is slidable within the cylinrical portion.
Abstract: 1,153,234. Valves. VAPOR CORP. 17 Oct., 1967 [24 Jan., 1967], No. 47176/67. Heading F2V. A valve for controlling the flow of high pressure fluid and adapted to have a fully closed, intermediate, and fully open state, comprises a housing 12 having disposed therein, and between an inlet 16 and outlet 26, a chamber 28, the chamber being defined by a conical wall portion 31, a cylindrical wall portion 30 and a piston 38 which is slidable within the cylindrical portion. The piston is biased by a spring 54 and fluid pressure within the chamber, which pressure is derived from the inlet via a restriction 32, into a position in which an extension 40 formed integrally therewith engages a seat 24 so closing the valve. Upon actuation of a solenoid operated valve 58, the chamber pressure is partially relieved via passage 56 so permitting the inlet pressure to move the piston into the chamber, the degree of movement being limited by a piston stem 48 which eventually obturates passage 56 and so serves to retain the valve in its intermediate position (Fig. 2, not shown). To bring the valve into its fully open state, a second solenoid valve 64 is actuated so permitting the chamber pressure to be fully relieved and the piston to move further into the chamber until it abuts a stop formed by the stem housing 46 (Fig. 3, not shown). In a modification, the cylinder may be vented to a point downstream of the outlet rather than to atmosphere.

20 citations

Journal ArticleDOI
TL;DR: The effect of aluminum powder in damping high-frequency solid-propellant instability has been investigated in a vortex burner developed previously as discussed by the authors, which was composed of a main chamber having a shallow center-perforated grain and a hot gas generator.
Abstract: The effect of aluminum powder in damping high-frequency solid-propellant instability has been investigated in a vortex burner developed previously. The combustor was composed of a main chamber having a shallow center-perforated grain and a hot gas generator. The generator fed combustion gases tangentially into the main chamber causing transverse mode combustion instability. Aluminum powder was added either to the main propellant or to the gas generator charge. Measurement of the amplitude of the pressure oscillations indicated the effectiveness of the metal acting 1) as an ingredient at the solid surface and in the gas phase and 2) in the gas phase only. In the absence of aluminum the combustor was unstable, exhibiting an oscillation frequency of ^3800 cps with a peak-to-peak amplitude of 55%. The addition of fine aluminum powder to the propellant in the main chamber was sufficient to damp out the high-frequency instability. Addition of aluminum to the gas generator propellant only was also effective in eliminating instability provided that an equivalent concentration of metal particles was added. It was concluded that the addition of aluminum powder to composite solid propellants suppresses instability by acting as an attenuator of sound in the gas phase rather than altering the driving or response of the propellants. Viscous damping is inferred to be the principal damping mechanism. Addition of the aluminum produced a nonacoustic disturbance which appeared to be eliminated at higher operating pressures.

20 citations

Journal ArticleDOI
TL;DR: In this paper, a coupled model of the hydrodynamics and thermodynamics of oscillating water columns (OWCs) wave energy converters is proposed to assess the primary energy conversion of the OWC wave energy converter, in a manner that under the wave excitation, the varying air volume due to the internal water surface motion creates a reciprocating chamber pressure.
Abstract: This is the second part of the assessment of primary energy conversions of oscillating water columns (OWCs) wave energy converters. In the first part of the research work, the hydrodynamic performance of OWC wave energy converter has been extensively examined, targeting on a reliable numerical assessment method. In this part of the research work, the application of the air turbine power take-off (PTO) to the OWC device leads to a coupled model of the hydrodynamics and thermodynamics of the OWC wave energy converters, in a manner that under the wave excitation, the varying air volume due to the internal water surface motion creates a reciprocating chamber pressure (alternative positive and negative chamber pressure), whilst the chamber pressure, in turn, modifies the motions of the device and the internal water surface. To do this, the thermodynamics of the air chamber is first examined and applied by including the air compressibility in the oscillating water columns for different types of the air turbine PTOs. The developed thermodynamics is then coupled with the hydrodynamics of the OWC wave energy converters. This proposed assessment method is then applied to two generic OWC wave energy converters (one bottom fixed and another floating), and the numerical results are compared to the experimental results. From the comparison to the model test data, it can be seen that this numerical method is capable of assessing the primary energy conversion for the oscillating water column wave energy converters.

20 citations

Journal ArticleDOI
TL;DR: In this paper, a test chamber has been constructed with data recordings including chamber pressure and temperature, battery voltage, current, and surface temperature as functions of time throughout the charging and failure processes.
Abstract: Lithium batteries have a tendency to fail violently under adverse conditions leading to the rapid venting of gas. Overcharge, thermal heating, and a combination of the two conditions are applied here to investigate the gas venting process. A test chamber has been constructed with data recordings including chamber pressure and temperature, battery voltage, current, and surface temperature as functions of time throughout the charging and failure processes. High-speed imaging and schlieren flow visualization are used to visualize the gas venting process. A direct comparison between lithium iron phosphate based K2 26650 and lithium nickel manganese cobalt oxide LG 18650 cells is made through a test series of the three failure methods. Failure under thermal, overcharge, and thermal-overcharge conditions are generally similar in terms of the gas venting process, but are observed to have increasingly energetic failures. The thermal-overcharge abuse condition demonstrates an ability to reconnect via internal short circuit even after an initial electrical failure seen as the refusal to accept charge. This reconnection is associated with a secondary, more energetic failure which can produce weak shock pressure waves.

20 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202322
202257
202167
202086
201991
201882