GB1454748A - Gas turbine ducted fan engines - Google Patents

Abstract

1454748 Gas turbine ducted fan engines HAWKER SIDDELEY DYNAMICS Ltd 16 Nov 1973 [16 Nov 1972] 52902/72 Heading F1J The invention relates to a gas turbine ducted fan engine, the fan rotor of which has reversible pitch fan blades for use in aircraft braking, there being means for improving flow of air to the compressor of the core engine when the fan blades are operating in reverse pitch mode. The engine shown in Fig. 1b which is not in accordance with the invention comprises a fan rotor 11 disposed with a fan casing 16, there being stator guide vanes 14 disposed within the fan duct downstream of the fan rotor blades. The inlet 12 to the compressor of the core engine is shown and comprises inlet guide vanes 17. The engine is shown operating in reverse thrust mode in which air is flowing forwardly through the fan to discharge through the normal inlet, some of the air reversing as indicated at 20 to flow through the inlet guide vane assembly 17 to the compressor of the core engine. The swirl imparted to the inflowing air by the guide vanes 14 results in incorrect entry to the guide vanes 17 with consequent inefficient swirling as indicated at 21. In accordance with the invention flow correcting guide vanes 22 are disposed around the intake lip of the core engine and are so inclined as to remove the swirl imparted to the inflowing air by the stator guide vanes 14. The guide vanes 22 prevent a substantially zero incidence angle to the air-flow through the fan duct when the fan rotor blades are in normal forward pitch. As shown the guide vanes 22 are extensions of the inlet guide vanes 17, extending around the intake lip and rearwardly along the outer wall of the intake.