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A typical nominal regulated gauge pressure from a medical oxygen regulator is 3.4 bars (50 psi), for an absolute pressure of approximately 4.4 bar and a pressure ratio of about 4.4 without back pressure, so they will have choked flow in the metering orifices for a downstream (outlet) pressure of up to about 2.3 bar absolute.
The locomotive's air compressor typically charges the main reservoir with air at 125–140 psi (8.6–9.7 bar; 860–970 kPa). The train brakes are released by admitting reduced and regulated main reservoir air pressure to the brake pipe through the engineer's automatic brake valve.
An early major application of compressed air was in the drilling of the Mont Cenis Tunnel in Italy and France in 1861, where a 600 kPa (87 psi) compressed air plant provided power to pneumatic drills, increasing productivity greatly over previous manual drilling methods. Compressed-air drills were applied at mines in the United States in the 1870s.
Compressed air has been used to start gas turbine engines using air impingement starting (in which air is directed at the engine turbine blades through nozzles in the turbine casing, used on US Navy General Electric J79 engines). It is much more efficient to use an air turbine starter (ATS) which is usually mounted on an accessory gearbox. [5]
Z88.2–2015 notes that "open-circuit SCBA are equipped with a full facepiece or tight-fitting hood", and, like closed-circuit SCBAs, can be configured in pressure-demand or demand mode. Air is not recirculated in an open-circuit SCBA. [12] Z88.2 notes that these SCBAs normally use compressed air, but can also use cryogenic air or compressed ...
Traditionally, compressed air work was limited to maximum ambient pressures of between 3 and 4 bars (3.0 and 3.9 atm), but experience with offshore saturation diving shows that higher pressures can be managed at acceptable risk using the techniques developed in that industry, including saturation exposures and the use of breathing gases other than air.
The sound produced by compressor surge is called turbo flutter and the repeated, high speed cycling will cause a cyclic torque on the compressor and may lead to increased stresses on the bearings and compressor impeller. [2] A blowoff valve is designed to release pressure in the intake system when the throttle is closed.
For air with a heat capacity ratio =, then =; other gases have in the range 1.09 (e.g. butane) to 1.67 (monatomic gases), so the critical pressure ratio varies in the range < / <, which means that, depending on the gas, choked flow usually occurs when the downstream static pressure drops to below 0.487 to 0.587 times the absolute pressure in ...