GB652173A - Improvements relating to aircraft power plants having a reciprocating engine, a supercharger, and an exhaust-driven turbine - Google Patents

Abstract

652,173. Pumps. ROLLS-ROYCE. Ltd. March 11, 1948, No. 7498. [Classes 7(ii) and 7(vi)] [Also in Group XXVI] A supercharging compressor is driven by an exhaust-actuated turbine, preferably through a free-wheel device allowing the engine and compressor to over-run the turbine, and an auxiliary compressor delivers air to cool the exhaust flowing through the turbine. The plant is shown as applied to a V in-line engine having a compressor 12, Fig. 1, co-axial with the crank-shaft. The compressor has an air inlet 14 with a valve box 15 and delivers through a pipe 16 to the inlet manifolds which are located between the banks of cylinders. The crankshaft drives through a two-speed gear in a gear box 32. The exhaust-actuated turbine 18 has its axis at right angles to the crankshaft axis and is placed on a level with the upper extremities of the cylinders. Two exhaust manifolds are connected to a double scroll forming the inlet to the turbine, and its outlet 22 is surrounded by a cowling 25 having a forwardly-facing air entry 23a. The turbine assembly 18 is mounted on the air inlet 14 of the compressor 12 and a two-part casing 25. The turbine disc 18a is directly coupled to an auxiliary two-stage centrifugal compressor 26a, 26b, Fig. 4A, the inlet to the first stage impeller 26a being housed in an inverted bell-shaped flange 28 formed on the cover of the compressor 12. The twostage compressor 26 delivers air through a pair of ducts 29, Fig. 1, into jacket spaces 30 surrounding the exhaust passages, whence the air enters the exhaust passage through inlets 31 to mix with the exhaust gases to cool them. Manual or automatic valves 33, 65, control the flow of exhaust gas into the turbine, and directly to atmosphere respectivly, the valves 33 being closed and the valve 65 fully opened under maximum power, and vice versa. Automatic control for maintaining a constant inlet pressure to the turbine exceeding a predetermined value of back pressure on the engine may be provided for the valve 65. Additionally, the valve 33 and the supply of cooling air from the auxiliary compressor may be controlled by a thermal device. The turbine shaft 34, Fig. 4A, drives a lay shaft 43 through gears 37, 38, 39, a shaft 40, and bevel gears 41, 42. A gear 44 and the bevel gear 42 are connected through a free-wheel drive 45, the gear 44 meshing with a gear on the supercharger drive-shaft 36, which can thus over-run the turbine 18. The engine crank-shaft drives a layshaft 49, Fig. 4B, of a two-speed gear through a quill shaft 46 and gears 47, 48. The shaft 49 carries driving members 50 of a pair of friction clutches which drive gears 51, 52 meshing with gears 53, 54 secured to the compressor shaft 36. Clutch-operating levers 57 mounted on a spider 56 are operated by a hollow piston member 58 moved by hydraulic fluid, which is fed through passages 61. The hydraulic fluid supply is controlled either manually or automatically by an altitude-sensitive capsule. The additional compressor may be omitted, the' cooling of the exhaust gas then being provided for by radiation or by the introduction of cooling air supplied by the main supercharger. The plant may comprise a pair of engines arranged in tandem, each engine having a turbine and supercharger as described above; alternatively, a separate turbine and exhaust system may be provided for each engine.