Bypass valve control

Claim 2

In an apparatus of the type having a casing structure supporting first and second independently rotatable compressor rotors arranged in serial flow relationship in a common passage for pressurizing fluid flow therethrough, with the inertia to available torque associated with one rotor being greater than that associated with the other rotor, in combination, at least one bypass passageway formed through said casing and communicating with said common passage intermediate said compressor rotors for bypassing fluid therefrom, means for varying the flow area of said bypass passageway, and means for controlling said flow area varying means as a predetermined scheduled function of selected parameters of operation of said second compressor rotor, said control means having means responsive to at least one signal indicative of rate of change of speed of said second compressor rotor for resetting said predetermined schedule, whereby fluid in excess of that which the second compressor rotor can handle is bypassed to prevent back pressuring and stall of said first rotor.

Claim 3

The structure of claim 1 further characterized in that said selected parameters of operation of said second compressor rotor include the temperature of fluid at the inlet to and the speed of said second compressor rotor.

Claim 4

The structure of claim 1 further characterized in that said reset means is responsive to signals representing the temperature of fluid at the inlet to and the speed of said second compressor rotor.

Claim 5

The structure of claim 1 further characterized by and including a throttle lever for manual control of said apparatus, said reset means being responsive to a signal representing the positional rate of change of said throttle lever.

Claim 6

The structure of claim 1 further characterized in that said reset means is adapted to generate a reset signal in response to a predetermined rate of second compressor rotor deceleration and said means for controlling said flow area varying means further includes means for sensing the speed of said second compressor rotor and generating a signal in response thereto, means for sensing the temperature of air at the inlet to said second compressor rotor and generating a signal in response thereto, means responsive to said temperature and speed signals for generating a control signal corresponding to said predetermined scheduled function, means for generating a feedback signal in response to the position of said flow area varying means, and means responsive to said control, feedback and reset signals for controlling said bypass area varying means.

Claim 7

The structure of claim 5 further characterized in that said flow area varying means includes a fluid actuator, and said control, feedback and reset signal responsive means comprises a pilot valve operative to generate a fluid pressure signal in response to said control signal and a combination of said feedback and reset signals.

Claim 8

A turbofan engine including, in combination, a core engine having a compressor, a combustor and a first turbine disposed in serial flow relationship along an annular core engine flow passage, a core engine casing, an annular fan casing defining a fan duct therein, said core engine casing projecting into said fan casing and defining a generally annular duct portion therebetween, a second turbine disposed downstream of and rotatable independently of said first turbine and drivingly connected to a fan rotor located upstream of said core compressor, said fan including at least one stage of blades extending generally radially across said fan duct for pressurizing airflow therethrough and at least one booster stage of blades disposed within said core engine flow passage, upstream of said core compressor, for further pressurizing a portion of said airflow to deliver to said core compressor, at least one bypass passageway formed through said core engine casing and communicating said core engine passage with said annular duct portion at a location intermediate said booster stage and said core compressor, means for varying the flow area of said bypass passageways, and means for generating a signal for controlling said flow area varying means in response to a predetermined scheduled function of the corrected speed of said core engine and for resetting said signal in response to a predetermined rate of change of said core corrected speed to thereby prevent the overpressuring of said booster stages by bypassing air in excess of requirements to said core compressor.

Claim 9

A turbofan engine including, in combination, a core engine having a compressor, a combustor and a first turbine disposed in serial flow relationship along an annular core engine flow passage, a core engine casing, an annular fan casing defining a fan duct therein, said core engine casing projecting into said fan casing and defining a generally annular duct portion therebetween, a second turbine disposed downstream of and rotatable independently of said first turbine and drivingly connected to a fan rotor located upstream of said core compressor, said fan including at least one stage of blades extending generally radially across said fan duct for pressurizing airflow therethrough and at least one booster stage of blades disposed within said core engine flow passage, upstream of said core compressor, for further pressurizing a portion of said airflow to deliver to said core compressor, at least one bypass passageway formed through said core engine casing and communicating said core engine passage with said annular duct portion at a location intermediate said booster stage and said core compressor, means for varying the flow area of said bypass passageways, and means for generating a signal for controlling said flow area varying means in response to a predetermined scheduled function of the corrected speed of said core engine and for resetting said signal in response to a predetermined rate of change of said core corrected speed to thereby prevent the overpressuring of said booster stages by bypassing air in excess of requirements to said core compressor.

Claim 10

The structure of claim 7 further characterized in that said predetermined schedule is adapted to provide a maximum bypass flow area at core corrected speeds corresponding to start-up and idle of said turbofan engine.

Claim 11

The structure of claim 8 further characterized in that said maximum bypass passage flow area is sized to direct sufficient airflow for start-up of said core engine during conditions of reverse windmilling of said fan rotor.

Claim 12

The structure of claim 7 further characterized in that said control and reset means comprise means for sensing the speed of said core compressor and generating a signal in response thereto, means for sensing the temperature of air at the inlet to said core compressor and generating a signal in response thereto, means responsive to said speed and temperature signals for generating a signal corresponding to said predetermined scheduled function, means for generating a feedback signal in response to the position of said bypass flow area varying means, reset means for generating a signal in response to a predetermined rate of change of said core corrected speed, and means responsive to said scheduled feedback and reset signals for generating and resetting said control signal.