Variable Guide Vane With Transfer Slot for Gas Turbine
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Solution Overview
Problem
Conventional variable inlet guide vanes in gas turbine engines experience airflow separation and increased pressure loss at off-design conditions due to rigid rotation and geometrical discontinuities in tandem aerofoil designs, leading to inefficiencies and higher specific fuel consumption.
Innovation Solution
A variable guide vane design featuring a fixed portion, a movable flap with a rotatable U-shaped profile, and a transfer slot that re-energizes the boundary layer by directing airflow tangentially over the suction surface, supplemented by pressurized air from an internal cavity, which reduces pressure loss and enhances efficiency across a range of operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable inlet guide vanes are rotated at off-design conditions to achieve acceptable rotor blade incidence, then the airflow orientation is improved, but airflow separation occurs and pressure loss increases
Solution Approach 1:
The guide vane is divided into a fixed portion and a movable flap portion that can rotate independently. This segmentation allows the trailing edge to be adjusted for optimal airflow orientation while the leading edge maintains a constant angle, preventing flow separation and reducing pressure loss at off-design conditions.
Solution Approach 2:
Different parts of the guide vane have different functional characteristics: the leading edge maintains a constant angle to prevent flow separation, while the trailing edge (movable flap) varies the angle to control outlet flow direction. This local differentiation optimizes both pressure loss prevention and airflow orientation control.
2Loss of energy
If tandem aerofoil design with hinged configuration is used to reduce pressure losses, then pressure loss is reduced, but flow separation occurs on the moving part at high turning angles
Solution Approach 1:
The constant leading edge angle portion prevents flow separation by maintaining smooth airflow attachment, while the variable trailing edge portion handles flow direction control. This local functional differentiation eliminates the geometrical discontinuity problem in conventional hinged designs.
Solution Approach 2:
By separating the leading edge (fixed angle) from the trailing edge (variable angle), the design eliminates the discontinuity that causes flow separation in conventional hinged aerofoils, while still achieving the benefit of variable geometry for pressure loss reduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces pressure loss, increases compressor pressure ratio and efficiency, and lowers specific fuel consumption by re-energizing the boundary layer, providing improved performance across a wider range of engine operating conditions.
Implementation Method 1
directing a first air flow passing through the transfer slot tangentially over the suction surface of the movable flap... acts to re-energise the boundary layer on the suction surface of the movable flap
Implementation Method 2
reduces the pressure loss due to flow separation over the flap surface
Data Source
AI summary
A gas turbine engine variable guide vane has a fixed portion on an upstream side, a movable flap on a downstream side and a transfer slot between a fixed portion trailing surface and a movable flap leading surface. The movable flap has opposite pressure and suction sides along a chord line between leading and trailing edges, and is rotatable about an axis along a movable flap span over a range of angular positions between open and closed. The trailing surface has a substantially U-shaped profile with first and second branches respectively partially around the pressure and suction sides. The transfer slot has inlet and exhaust ports respectively on the pressure and suction sides. In the closed position the suction side contacts the second branch closing the exhaust port, and in the open position the second branch directs a first air flow through the transfer slot tangentially over the suction surface.