Applications of Pneumatic Systems in Aircraft

Applications of pneumatic Systems in argumentcraftPNEUMATIC SYSTEMS entryWhen talking about pneumatic governing body, we need to talk about where the pneumatic schema comes from and it comes from a world position remains, in that respect be ternary divergent emblems of power bodys,hydraulic arrangingpneumatic schemaElectrical systemPneumatic systems in AircraftsPneumatic systems they ar also known as vacuum or insistence systems, the power m both functions which are of import to the aviationcraft. Power instrument arrive add-on, flaps, windows, carriage conditioning, doors and auto pilot devises are some of m whatever unconscious processs powered by pneumatic system. Pneumatic and hydraulic systems are similar and character pie-eyed precariouss. Fluid carro expenditurelographic point could be liquids as water, crude oil, or something that flows. And both liquids and artilleryes flow, since they are considered as fluids however, there is a great deal of dif ference in the characteristics of the devil.Liquids flocknot be squeezable a quart of water still occupies about a quart of space regardless of how hard it is stringent. But gases can be loaded, a quart of conduct can be compressed into a thimble of space. Considering this differences gases and liquids are fluids and can be do to transmit power. The type of social unit used to provide pressurized occupation for pneumatic systems is determined by the systems argumentation bosom requirements.Components in Pneumatic SystemHydraulic systems are sometimes compared to, pneumatic systems but some similarities can further be true in general terms. Such asPneumatic systems do notutilize reservoirshand heart and soulsaccumulatorsgovernorsbuilding normal oblige from locomotive railway locomotive or electrically driven power pumpsBut similarities do exist in some components.Air CompressorsSimply an impart compressor is a Pump that compresses port, its job is raising air force to in a higher place establish drive for use in pneumatic systems on some aircraft, air compressors bring on permanently installed and added to recharge air bottles when hale is used to ensure a unit. Several types of compressors that are used for this purpose. Some have three stages of condensate, while the differents have two, depending on the desired operating wring. relief ValvesRelief valves are used to thwart damage. They act as a pull limiting units and prevent bursting runs and blowing out seals from excessive pressures. laterality ValvesControl valves are also a necessary part of a typical pneumatic system. It is used to control conditions such aspressure, flow,temperature, andliquidlevel by fully or stepwise fountain or closing. Control Valve is also called a Final Control Element.Check ValvesCheck valves are used in both hydraulic and pneumatic systems. Check valve is also called a one way valve which allows pressurized air to enter the system, but it preven ts backflow of air toward the Compressor when Compressor system is stopped which prevent loss of pressure in the system.RestrictorsRestrictor is type of control valve used in pneumatic system. Figure under 1llustrates an orifice type restrictor which has a tremendous breathing in port and a small outlet port. The rate of the air flow and the speed of motion of the actuating unit get out be bowdlerize by the small outlet port.Variable RestrictorThe variable restrictor is a type of speed regulating unit it contains an adjustable goad valve, therefore has threads around top and the lower end. Depending on the direction turned and the needle valve turns the sharp point either into or out the small opening to decrease or to increase the size of the opening. Since air entering the inlet port must be able to pass through this opening before reaching the outlet port adjustment determines the rate of airflow through the restrictor.PRESSURE REGULATORThe pressure regulator is to cont rol the uttermost pressure in the system and to off-load the compressor when the system is idle.Oil and Water ensnare regulatorThe oil and water trap is designed to remove any water or oil which may be suspended in the air delivered by the compressor.Air FiltersAir filters purpose is to prevent oil vapor, dirt or moisture from passing into the various services. It is installed vertically with the expire plug at the bottom.Some advantages arePrevent system pollutionRemove air particulatesClean air is essential to good operationFigure 1. View of Cutaway air filter. Air entering the top of percentage first flows through the element to remove solid particles. thusly flows in a circular motion, where centrifugal force separates water from the air stream, andthen the water falls to the filters sump.Storage BottlesStorage bottles act as a reservoir of compressed air which be givens all services to pneumatic system. Compressors main(prenominal) use is to build up system pressure whe n it falls at a lower place normal pressure level. The size of the bottles are taken from the volume of actuators and pipelines determines take for the normal and urgency pneumatic services.Storage bottles are generally made of steel, and may use a wire wound construction for maximal strength. Light ally or fiberglass materials may be other typs of material wich will be used.Air PumpHeart of pneumatic system is pressure or vacuum air pump. Which is usually engine driven)There are two basic types Wet air pumps which use engine oil to lubricate pump internallyDry air pumps which is more common more common have graphite webs deep down pump casing self-lubricate as pump rotates spicy pressure systemsHigh pressure system is driven by an engine driven compressor feeds air from an unloading valve through the system keeping the pressure. The pressure around this system is 3000 psi but this will vary from manufacturer to another. There will usually also be a fundament valve on the air craft system to enable to pressurize when the main engines are not running. In higher(prenominal) pressure systems air is normally stored in a metal bottles at pressures from 1000-3000 psi, depending on the particular aircraft system.Some high pressure systems are oxygen linesFlapsBreaksLanding accessoryLow pressure systemsLow pressure systems are pressurized up to 1000 psi and uses an engine driven vane type pump. They are may be used to driveAir consdoor sealsde-ice bootssmall low power applicationsMedium-Pressure SystemsA medium-pressure pneumatic system usually does not include an air bottle. Instead, it draws air from the compressor section of a turbine engine. Which is generally around 50 to 150 psi This is very much called bleed air process and is used to provide pneumatic power for engine starts, engine deicing, wing deicing, and in some cases, it provides hydraulic power to the aircraft systems but only if the hydraulic system is equipped with an air-driven hydraulic pum p. locomotive engine bleed air is also used to pressurize the reservoirs of the hydraulic system. fate Backup SystemsMany aircraft use a high pressure pneumatic back up system source to extend the arrive gear or actuate the brakes. And if main hydraulic braking system fails. Nitrogen gas is not directly used to actuate the landing gear or brake system units but applies the pressurized nitrogen to move hydraulic fluid to the actuator. This process is called pneudraulics.Nitrogen BottlesThere are two bottles of nitrogen stored for emergency use, mostly bottles located on each side of odourise hustle well. Actuation of an outlet valve released by Nitrogen from the bottles. Once depleted, maintenance military force must recharge the bottles. Fully serviced pressure will be nigh 3,100 psi at 70 F/21 C, which is only replete for one extension of the landing gear.PNEUMATIC SYSTEMThe illustrator below is a typical full pneumatic system as is used on a twin engine commuter transport aircraft. Each surgical procedure is shown below in dot points Each of the two compressors is a four stage plunger type pump, driven from the accessory gearbox of the two turboprop engines.Air is taken into the first stage through an air duct.It is compressed, then passes to the other three stages.From the fourth stage the discharge air is routed through an intercooler and a bleed valve to the unloading valve.The bleed valve is kept unsympathetic by engine oil pressure and in an event of a loss of an engine lubricating oil, the valve will open and relieve the pump of any load.The unloading valve maintains pressure mingled with 2,900 and 3,300 psi in the system.When the pressure rises to 3,300 psi a check valve traps it and dumps the output of the pump air overboard.The pump is directed back into the system when the system pressure drops to 2,900 psi.The shuttle valve which is between the compressor and the main system makes it possible to charge the system from a ground source .When the pressure from the immaterial source is higher than the external source of the compressor, when the engine is not running, the shuttle slides over and freezers the compressor.Compressed air system have moisture and this will condense and freeze when the pressure of the air is dropped for propulsion because of this every bit of water must be removed from the air. whence a separator collects the water that is in the air on a baffle and holds it until the system is shut down.When the separators pressure drops below 450 psi, a drain valve wreaks and all of the accumulated water is blown overboard. consequently an electric heater prevents the water collected in the separator from freezing. after(prenominal) the air leaves the moisture separator, about 98% of its water removed, it passes through a desiccant, or chemical drier, to remove the last traces of moisture.Before the air enters the tangible operating system it is filtered through a 10 micron sinter metal filter.In the right engine nacelle a back pressure valve is installed.This is essentially a pressure relief valve in the supply line that does not open until the pressure from the compressor or ground charging system is above 1700 psi and this make sure that the moisture separator will operate most efficiently.The left side where there is no back pressure valve can be connected if it is required to operate the system from an external source of less than 1700 psi.There are three air retentivity bottles in this type of aircraft system,A 750 cu. Inch bottle for the main systemA 180 cu. Inch bottle for normal brake operationA 180 cu. Inch bottle for emergency operation of the landing gear and brakes.Then come the mutually operated isolation valve which allows a technician to shut up off the air supply so that the system can be serviced without having to discharge the storage bottle. Most of the components in this system operate with pressure of 1000 psi so a pressure reducing valve is installed bet ween the isolation valve and the supply manifold for normal operation of thelanding gearpassenger doordrag brakepropeller brakenose wheel steeringSince this valve reduces the pressure to 1000 psi it also serves as a backup pressure relief valve.The emergency system stores compressed air under the full system pressure of 3,300 psi and supplies it for landing gear emergency extension.EMERGENCY BRAKE SYSTEMIn a failure of the hydraulic system, the pilot of a large aircraft can operate a pneumatic valve on the instrument panel and direct compressed air or nitrogen into the brake system. When the pilot turns the handle, a regulator is adjusted that controls the air pressure to the brakes. When sufficient pressure reaches the brake line, the piston moves up against the force of the control spring and shuts off the inlet valve. The compression of the spring determines the amount of pressure supplied to the brake. When the brake handle is rotated in the direction to release the brakes, the air is exhausted overboard. Then rather than allowing compressed air to enter the wheel cylinder, which would require the entire brake system to be bled of air, the emergency air may be directed into a manoeuvre tube. The air forces hydraulic fluid from the tube into the brake system. tinge operation of the brakes is also achieved in many aircraft by the use of compressed air. When the pilot is sure that there is no hydraulic pressure to the brakes, the pneumatic brake handle, located on the left instrument panel, can be rotated. Clockwise rotation of this handle increases the brake pressure. Nitrogen pressure released by this control handle forces hydraulic fluid in the transfer tube into the main wheel brakes through shuttle valves. When the brake handle is rotated counterclockwise pressure is released and the nitrogen is exhausted overboard. http//www.engineerstudent.co.uk/uni_directional_flow_control_valve_symbols.htmlhttp//navyaviation.tpub.com/14018/css/14018_285.htmhttp//en. wikipedia.org/wiki/Relief_valvehttp//mech-engineer.blogspot.com.au/2009/05/drawworks-brake-system-training-course.htmlhttp//www.aliexpress.com/airbrush-compressor-regulator_reviews.htmlhttp//www.airid.com/high-volume-drain-valve.htmlhttp//basicaerospace.blogspot.com.au/2013/01/aircraft-pneumatic-system-for-beginners.html