GB647578A - Improvements in air conditioning and cabin pressurising plant for aircraft - Google Patents

Abstract

647,578. Ventilating aircraft. MINISTER OF SUPPLY. Feb. 4, 1947, No. 11825/49. Divided out of 621,123. [Class 137] An aircraft pressurising and air conditioning plant comprises firstly an air compressor arranged to deliver air at pressures ranging from cabin pressure to pressures of such magnitude that subsequent expansion will give the required cabin pressure, secondly, air conditioning apparatus having units for selectively treating the air, including a cooler operable on air supplied direct from the compressor, an expander operating on a proportion of the air supply as determined in accordance with the cabin humidity, a water separator, a heater and humidifier, thirdly, governing means operable to vary delivery pressures within the range and .control means operable independently of the delivery pressure, to select the conditioning units for treating the air, so that .a predetermined atmosphere is maintained in the cabin. In one form, the apparatus consists in a compressor 1 driven by one of the aircraft engines 2 through a variable ,speed drive 3. The drive ratio is selected by a governor unit 4 through a gear selector 5 according to engine speed, compressor speed and altitude. Air is drawn into the compressor and delivered to a cooler 7, the degree of cooling which occurs therein being controlled by the position of gills or vanes 9. From the cooler the air passes to a turbine expander 11 or through a by-pass 13 to a duct 12 and then successively-through a water separator 16, a heater 17, a humidifier 18 and a silencer 19 to a pressure cabin 20, wherein it is distributed by a duct 26. Contaminated air leaves the cabin by duct 28 and valve 30 which regulates the pressure in the cabin. A humidostat 33 in the cabin controls a valve 14 in by-pass 13, the humidifier 18 and the gills 9, whilst a thermostat 32 controls heater 17 and assists in the control of gills 9. With normal humidity conditions, gills 9 are closed and heater 17 controlled to give correct cabin temperature, valve 14 being open and the compressor being driven at the necessary speed to give sufficient air at cabin pressure. If the humidity rises to a certain point, the humidostat causes valve 14 to begin to close and gills 9 to open, some of the air passing through the expander.. Simultaneously the governor 4 selects a drive ratio to give the necessary rise in compressor delivery pressure. The air streams mix in conduit 12 and pass through the water separator 16 which extracts water vapour condensed as droplets in the air from the expander, the air passing out of the separator being at a humidity which will be correct at cabin temperature, to which temperature the air is raised in heater..17. If the cabin humidity falls, the quantity of air passing through the expander is diminished and less water is extracted, the humidifier 18 being brought into action if necessary. Part of the cabin air may be recirculated by a fan 36 through a duct 37 and if necessary the air conditioning plant can be controlled manually.