GB1067129A - Improvements relating to the silencing of gas turbine engines - Google Patents

Abstract

1,067,129. Gas turbine engines. ROLLSROYCE Ltd. March 15, 1966, No.11393/66. Addition to 920, 889. Heading F1G. A gas turbine engine has an air intake which comprises an outer casing, an inner casing mounted within the outer casing to define therewith an annular air intake passage, and means for effecting movement of a part only of at least one of the casings towards and away from the other casing and into and out of a position in which the air intake passage is choked when the engine is running at approach idling speed, whereby when the air intake passage is so choked the engine noise escaping therefrom is reduced. The air intake shown in Fig. 1 comprises an outer casing 13 and an inner fairing member 15 which define an annular air intake passage 16. An annular chamber 20 is provided in the outer casing, the chamber having an inner wall 17 which is constituted by an inflatable member formed of elastomeric material such as neoprene. Air under pressure may be supplied to the chamber 20 through line 21, the inflatable member 17 then expanding to the position indicated by broken lines. The radial width of the annular intake passage is thus reduced and with the reduced air mass flow at the approach idling speed, the passage is choked. In a second embodiment a further inflatable member is disposed on the fairing cone, the reduced air intake passage being formed between the two inflated members.