GB805418A - Jet propulsion plant - Google Patents

Abstract

805,418. Jet-propulsion plant. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. Oct. 2, 1956 [Oct. 5, 1955], No. 28439/55. Class 110 (3). [Also in Group XII] A jet-propulsion plant comprises a main duct with an air intake at its forward end and a propulsion nozzle at its rearward end, a dynamic compressor arranged within the duct to compress the air therein, a source of high velocity gas independent of the atmospheric air connected to discharge through a secondary duct into the main duct downstream of the compressor and a turbine located in the secondary duct and forward of and in driving connection with the compressor. In the arrangement shown an annular main duct 1 extends between an intake 4 and a variable area propelling nozzle 5. An axial flow air compressor 6 which compresses air in the main duct 1 is driven by a turbine 17 having two-rows of velocity compounded impulse blading through shafts 28, 30 and reduction gearing 29. The turbine 17 is supplied with working fluid by a combustion chamber 13 fed with a fuel and an oxidant from tanks 18, 19 by pumps 20, 21. The secondary exhaust duct 16 downstream of the turbine divides into a number of pipes 31 which cross the main duct 1 and are connected to a manifold 32. The manifold 32 has a number of apertures 33 which lead into the main duct downstream of the compressor. Branch pipes 34 leading to propulsion nozzles 35, located at the surface of the aircraft or missile in a region of low pressure when in flight under design operating conditions, are connected to pipe 31. Valves 36, 37 are provided for control purposes. On the downstream side of the compressor, the duct 1 is enlarged to form an annular combustion chamber 38 in which the exhaust gases from the turbine mix with air from the compressor 6. The gases may be reheated on occasion by injecting a fuel such as kerosene if the gases are oxygen rich or an oxidant if the gases are fuel rich. Nozzles 39 for injecting the fuel or oxidant may be provided in the main combustion chamber, in the main duct upstream of the combustion chamber or in the secondary duct. Baffles 42 are provided to support the nozzles 39 and provide a flame stabilizing zone. In a modification, Fig. 2 (not shown), the single combustion chamber 13 is replaced by a number of individual combustion chambers discharging into the turbine inlet manifold. In this arrangement, the jet-propulsion unit may be controlled by throttling the fuel supply to one or more chambers, by partially screening the turbine inlet nozzles or by providing adjustable turbine inlet nozzles, the throat area of which may be varied. The turbine 17 in this case, may comprise three pressure compounded stages each consisting of two rows of velocity-compounded axial-flow impulse blading and drives the compressor 6 through a direct connection. In another embodiment, Fig. 3 (not shown), the individual combustion chambers are arranged radially and are enclosed in the struts 12 so that they are readily accessible from outside the outer casing for servicing. In another modification, the combustion chamber or chambers may be housed outside the plant. The gear-box 29 may be arranged, if desired, in front of the turbine 10, or behind the compressor 6 in which case the turbine or compressor will have a hollow shaft through which the other shaft passes. In a further embodiment, Fig. 4 (not shown), the combustion chambers are arranged to discharge into a reverse flow turbine having two-tier blading. A manifold used to reverse the flow of gas may be used as a reheat combustion chamber. In another modification, Fig. 5 (not shown), the turbine is of the radial flow outward-inward type. Provision is made for reheating the working fluid where the flow is reversed. The plant may be controlled by diverting part of the turbine exhaust gas to atmosphere through the branch pipes 34. The plant may also be operated as a ram jet by shutting off the fuel to the combustion equipment 13 and operating the combustion chamber 38 as a ram jet, the compressor rotor being allowed to windmill. In this case, to reduce turbine windage losses, the turbine may be disconnected from the compressor or connected to a region of low pressure by closing valve 37 and opening valve 36. The bombustion chamber 38 may be replaced by a number of combustion chambers. The ducts 31 may be constituted in part by passages in the compressor rotor formed between the rotor surface and the blade platforms. Specification 749,009 is referred to.