GB856975A - Gas turbine power units for helicopters - Google Patents

Abstract

856,975. Helicopter propulsion systems. NAPIER & SON Ltd., D. July 16, 1958 [Aug. 7, 1957], No. 24930/57. Class 4. [Also in Group XXVI] A helicopter power unit has at least one engine comprising a turbine-driven air compressor which supplies compressed air to a combusition chamber or chambers, and a power turbine mechanically coupled to the helicopter rotor and supplied with combustion products from the said chamber or chambers, said power unit including means for delivering an additional supply of compressed air from the said air compressor or from a turbine-driven auxiliary compressor, to and through the rotor blades for discharge as propulsive jets at or near the blade tips, this additional compressed air by-passing the said combustion chamber or chambers. In Fig. 1 a gas turbine power unit is mounted vertically in a helicopter to drive rotor 18, 19, the unit comprising a multi-stage compressor 10, combustion chambers 12 and turbine 13. Combustion gases drive a free turbine 15 coupled through reduction gearing 17 to the rotor head 18. A tapping 20 from compressor 10 is controlled by valves 21 to supply air to conduits 22 which connect through rotary seals 24 with ducts 26 leading to tip propulsion nozzles in the rotor blades. When increased power is to be delivered to the rotor, valves 21 are opened and to compensate for the consequent reduction in air flow to the combustion chambers more fuel is supplied to the chambers to raise the heat-drop across turbine 13 thereby increasing its speed and the mass of air passing through compressor 10. In a number of alternative embodiments the air for the tip jets is obtained from a compressor separate from the main power unit. In Fig. 2 two power units 31, 32 similar to the power unit of Fig. 1 but without turbine 15, respectively connect through shafts 34, 35 ; fluid couplings 36, 37 ; freewheels 38, 39 and pinion and spur gearing 40, 41, 33 to drive a tail rotor shaft 43 and, through gearing 44, 45 a main rotor shaft 46. Gear 40 drives through a fluid coupling 49 on auxiliary compressor 47 which supplies air to the rotor tip jets. A schematic control system for a power unit such as shown in Fig. 2 is illustrated in Fig. 6. Air for the rotor tip jets is supplied by an auxiliary compressor 85 driven through fluid coupling 84 and fuel for the tip jets is supplied by a fuel pump 87 through metering valve 92 and line 93 to burners 94. In operation torque meters 80 detect a fall in torque of either of two engines and operate a valve 83 to supply liquid to coupling 84 and thereby bring compressor 85 into operation. The torque meters also generate a signal to bring fuel pump 87 into operation and to operate a spark generating device 88 connected to spark plug 96. A venturi 89 in air line 90 controls a flow meter 95 which adjusts metering device 92 to suit the flow of air to the combustion chamber. Specification 761,442 is referred to.