GB808514A - Improvements in or relating to apparatus for testing engines - Google Patents

Abstract

808,514. Jet propulsion plant. ROLLSROYCE Ltd. May 29, 1957 [March 23, 1956], No. 9229/56. Class 110 (3). Apparatus for testing jet propulsion engines under simulated forward speed and altitude conditions comprises a diffuser into which the engine exhausts through a jet nozzle so as to produce a sub-atmospheric pressure at the outlet plane of the nozzle and a recirculating circuit comprising a duct connected to the diffuser to receive hot gases therefrom which leads to mixing means where the hot gases and atmospheric air are mixed and then delivered into the engine intake. The jet propulsion nozzle 15 of the jet engine 10 is enclosed by a sheet metal casing 16 connected to the inlet end of a diffuser 17 discharging to atmosphere. A duct 20 is connected to a diffuser 17 at approximately its mid-length. The duct 20 discharges through a number of smaller ducts 23 into a mixing duct 24 connected to the engine intake, which duct mixes the hot gases with atmospheric air. An outlet duct 21 controlled by a slide valve 22 controls the amount of hot gas supplied to the mixing duct. The engine 10 is surrounded by wall 27 to form a chamber which is connected by passages 28 to the mixing duct 24 and by passages 29 to the casing 16 surrounding the propulsion nozzle 15. This allows a flow of ventilating air over the engine. Vent pipes, breathers and the like 30, 31, 32 may be connected by a duct 33 to the interior of the casing 16. Injectors 34, 35, operated by compressed air from the engine, may also be provided if required. A cowling 38 round the engine is vented by a pipe 39. The ratio between the intake and exhaust pressures may be varied by varying the position of the nozzle 15 in the casing 16 or by introducing losses in the mixing duct 24 or by both these means.