《航空飞机气动通用系统英文培训课件》由会员分享，可在线阅读，更多相关《航空飞机气动通用系统英文培训课件（48页珍藏版）》请在金锄头文库上搜索。
1、PNEUMATICSPNEUMATICS GeneralGeneralw Pneumatics, from the Greek (means - coming from the wind)Pneumatics was first documented in 60 A.DPascals principlePascals principle, states that , states that pressure is constant throughout pressure is constant throughout a static fluid.a static fluid.w Pneumat
2、ics are generally used for applications involving less force than hydraulic applications.w Pneumatics may be contrasted with hydraulics, which uses incompressible liquid media such as oil or water instead of air. w Air is compressible, is considered to be a fluid, and most industrial applications us
3、e approximately 80 to 100 pounds per square inch (psi) gauge pressure, as compared to hydraulics which are commonly used from 1,000 to 5,000 psi, and in some cases 10,000 psi and higher. w Both pneumatics and hydraulics are applications of fluid power. Physical pneumatic principles conclude that the
4、 pressure that forms in compressible liquids can be harnessed to a high potential of power. w Pneumatic systems can provides compressed air at a constant flow rate to air conditioning units, where its temperature is controlled and it is ducted into the cabin. w Pressurization systems, restricts the
5、escape of air from the cabin to maintain proper pressurization in the cabin. w The pneumatic system also provides compressed air for engine starting.w The engine compressors, auxiliary power unit, or a ground unit can be used to supply the pneumatic system. The pneumatic manifold is normally supplie
6、d from the engines. The APU or an external air source may also be used. Instructional purposes onlyPNEUMATICS - APPLICATIONSAPPLICATIONSSome examples - -PressurizationPressurization- -Anti-iceAnti-ice- -De-iceDe-ice- -Rain removalRain removal- -Lift enhancementLift enhancement- -Air conditioningAir
7、conditioning- -Engine startingEngine starting- -Pneumatic brakingPneumatic braking- -OtherOtherPressurizationPressurized air for the cabin comes from the compressor stages in the aircrafts jet engines. Moving through the compressor, the outside air gets very hot as it becomes pressurized. The portio
8、n drawn off for the passenger cabin is first cooled by heat exchangers in the engine struts and then, after flowing through ducting in the wing, is further cooled by the main air conditioning units under the floor of the cabin. w The cooled air then flows to a chamber where it is mixed with an appro
9、ximately equal amount of highly filtered air from the passenger cabin. The combined outside and filtered air is ducted to the cabin and distributed through overhead outlets.w Compared to other modes of transport, office buildings and other enclosed spaces occupied by large numbers of people, todays
10、jetliners provide an environment that is superior in many respects. For example, in the heating and cooling seasons, most office buildings provide a far lower percentage of outside air - often as low as 20 percent or even less. In addition, buildings typically have a much lower air-change rate, and
11、theyre seldom equipped with high-efficiency filters like those found in airplanes. w A further advantage for airplane passengers: the outside air that enters jetliner cabins at cruising altitudes is generally much cleaner than what is available for ventilating buildings and surface modes of transpor
12、tation.w Studies have confirmed the overall safety and effectiveness of cabin air systems. One of the studies, conducted for the U.S. Government, was the most comprehensive of all. It involved an independent testing service taking air samples on 92 randomly selected airline flights. The levels of po
13、llutants such as fungi and bacteria were found to be similar to or lower than those encountered in normal indoor environments. Also, levels of carbon dioxide were found to average less than one-third the limit recommended by the American Conference of Governmental Industrial Hygienists. Studies cond
14、ucted by Boeing and by airlines have shown similar results. Anti-icew Air acquired from engine bleed air is used to prevent ice formation by using the heat energy of the air to heat the surrounding surfaces above freezing. However this system draws power from the engine thereby reducing thrust poten
15、tial. Some aircraft direct this bleed air over the front windshield for ice prevention as well as the leading edges of the wing and tail surfaces.Instructional purposes onlyDe-icew Air acquired from engine bleed air, vacuum pumps, or air compressors to remove ice formation by using pressure of the a
16、ir to inflate “boots” on the flight critical areas of the aircraft. The “boots” inflate and break the surface cohesion of the ice so the forward motion of the aircraft can blow it off. Rain removalAir is acquired from engine bleed air, vacuum pumps, or air compressors to remove rain from the windshield. This high velocity air “blows” away any water that may come in contact with that surface.Instructional purposes onlyLift enhancementw Air acquired from en
