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US 5,794,432 AGranted
Variable pressure and variable air flow turbofan engines
AssigneeDiversitech Corporation
InventorsDonald K. Dunbar, Marlen L. Miller, George L. Converse
Life of this patent
Estimating the term…
Abstract
A variable cycle gas turbine engine has, in axial flow serial relationship, a fan assembly, a core engine, and an exhaust assembly. The core engine includes a compressor, a combustor, a high pressure turbine and a first shaft interconnecting the compressor and the high pressure turbine. The fan assembly is connected to a low pressure turbine by a second shaft which is coaxial with the first shaft. The fan assembly includes a plurality of variable pitch inlet guide vanes, variable pitch stator vanes, and variable pitch outlet guide vanes, the pitch of which are adjusted to regulate the airflow through the gas turbine engine and the pressure ratio across the fan assembly as controlled by the exhaust assembly.
Claims28
A variable cycle gas turbine engine, comprising:
- a fan assembly having a flow path comprising:
- (a) an inlet;
- (b) an exit;
- (c) a plurality of variable pitch inlet guide vanes disposed adjacent said inlet;
- (d) a plurality of variable pitch outlet guide vanes disposed adjacent said outlet;
- (e) a plurality of fan blades for imparting kinetic energy to the air passing through said fan assembly during use, said plurality of fan blades being arranged in at least a first row and a second row, said first row being disposed adjacent to and downstream of said variable pitch inlet guide vanes and said second row being disposed adjacent to and upstream of said variable pitch outlet guide vanes;
- (f) a plurality of variable pitch stator vanes disposed between said first and second rows of fan blades;
- and
- (g) said flow path sized to accommodate a maximum air flow there through and a maximum pressure ratio there across during operation at a fan speed and a stall margin;
- a single fan bypass duct in air flow communication with said fan assembly and disposed downstream thereof;
- a core engine in air flow communication with said fan assembly and disposed downstream thereof, said core engine having a compressor, a first turbine assembly downstream of said compressor, a first shaft connecting said first turbine assembly to said compressor whereby said compressor is driven by said first turbine assembly, and a combustor disposed between said compressor and said first turbine assembly;
- a second turbine assembly in air flow communication with said core engine and disposed downstream thereof, said second turbine rotatably connected to said fan assembly by a second shaft, said fan blades being rotatably driven by said second turbine assembly;
- said flow path sized to accommodate a first operating point at said fan speed, said first operating point having about said maximum air flow through said fan assembly at a pressure ratio across said fan assembly substantially less than said maximum pressure ratio;
- said flow path sized to accommodate a second operating point at said fan speed and about said predetermined stall margin, said second operating point having about said maximum pressure ratio across said fan assembly at an air flow through said fan assembly substantially less than said maximum air flow;
- a variable area exhaust nozzle disposed downstream of said second turbine assembly and in air flow communication with said fan bypass duct and said second turbine assembly, said variable area exhaust nozzle adapted to expand said air flows to the atmosphere during operation;
- and
- wherein said variable pitch vanes are adapted to regulate transition of the engine operation between said first operating point and said second operating point.
14 more elements
A method of operating a variable cycle gas turbine engine, comprising the steps of:
- providing a fan assembly having a flow path comprising:
- (a) an inlet;
- (b) an exit;
- (c) a plurality of variable pitch inlet guide vanes disposed adjacent said inlet;
- (d) a plurality of variable pitch outlet guide vanes disposed adjacent said outlet;
- (e) a plurality of fan blades for imparting kinetic energy to the air passing through said fan assembly during use, said plurality of fan blades being arranged in at least a first row and a second row, said first row being disposed adjacent to and downstream of said variable pitch inlet guide vanes and said second row being disposed adjacent to and upstream of said variable pitch outlet guide vanes;
- (f) a plurality of variable pitch stator vanes disposed between said first and second rows of fan blades;
- and
- (g) said flow path being sized to accommodate a maximum air flow there through and a maximum pressure ratio there across, said maximum air flow and said maximum pressure ratio being at a fan speed, said variable pitch inlet guide vanes, variable pitch stator vanes and variable pitch outlet guide vanes having a reference pitch position at said maximum air flow and said maximum pressure ratio;
- providing a core engine in air flow communication with said fan assembly and disposed downstream thereof, said core engine having a compressor, a first turbine assembly downstream of said compressor, a first shaft connecting said first turbine assembly to said compressor whereby said compressor is driven by said first turbine assembly, and a combustor disposed between said compressor and said first turbine assembly;
- providing a second turbine assembly in air flow communication with said core engine and disposed downstream thereof, said second turbine rotatably connected to said fan assembly by a second shaft, said fan blades being rotatably driven by said second turbine assembly;
- operating the variable cycle gas turbine engine at a first operating point to provide a first air flow through said fan assembly about equal to said maximum air flow and a first pressure ratio across said fan assembly which is less than said maximum pressure ratio by:
- (a) rotating said variable pitch inlet guide vanes and said variable pitch stator vanes to said reference pitch position;
- (b) rotating said variable pitch outlet guide vanes to an open position with respect to said reference pitch position of said outlet guide vanes;
- and
- operating the variable cycle gas turbine engine at a second operating point to provide a second air flow through said fan assembly less than said maximum air flow and a second pressure ratio across said fan assembly about equal to said maximum pressure ratio by closing said variable pitch inlet guide vanes, said variable pitch stator vanes, and said variable pitch outlet guide vanes with respect said positions of said vanes at said first operating point.
13 more elements
Dependencies are inferred from the claim text.