Variable-Shape Inlet Guide Vane Flap for Gas Turbine Fan
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Solution Overview
Problem
Conventional low bypass ratio gas turbine engines with single-stage articulated inlet guide vanes (IGVs) face challenges in maintaining optimal fan inlet conditions at partial-speed operations, leading to undesirable flow redistribution and increased risk of fan rotor mistuning due to significant spanwise flow redistribution and high positive incidence at the fan rotor tip section.
Innovation Solution
A variable-shape IGV system featuring a flexible flap made of compliant materials like silicon rubber with internal stiffening fibers, which can be actuated to adjust its stagger angle and twist distribution, ensuring a more symmetrical shape change from maximum open to maximum closed positions, thereby maintaining a desired spanwise distribution of axial velocity and angle at the fan rotor inlet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-stage articulated IGVs are used with 20 degrees of twist, then design point performance is improved with flat fan inlet relative Mach number and fan exit (Pt) profile, but at partial-speed conditions the tip region has relatively low axial velocity (Cx) and high positive incidence at the fan rotor tip section
Solution Approach 1:
The IGV flap is designed with a flexible portion made of compliant material that allows the flap to dynamically change its shape and twist distribution based on operating conditions. The flexible portion can be actuated to achieve different stagger angles, transitioning from a symmetric twisted shape at design point to an asymmetric shape at partial-speed conditions, thereby adapting the flow distribution to maintain optimal performance across the speed range
Solution Approach 2:
The IGV flap incorporates different sections with distinct properties: a root section that is actuated for stagger angle adjustment and a flexible portion with varying compliance characteristics. The flexible portion may include internal stiffening fibers or filaments distributed to provide localized structural support while maintaining overall flexibility, enabling different parts of the flap to respond differently to actuation forces and achieve the desired asymmetric flow distribution at partial speeds
2Adaptability or versatility
If IGVs are staggered to ~50 degrees closed at partial-speed conditions, then off-design partial-speed operability is improved, but significant spanwise flow redistribution occurs causing low axial velocity (Cx) at the tip region and high positive incidence at the fan rotor tip section
Solution Approach 1:
The IGV flap is designed to assume an asymmetric shape when closed at partial-speed conditions, with the flexible portion twisted relative to the root section. This asymmetric configuration creates a non-uniform stagger angle distribution across the span, with the tip region having a different effective angle than the root region. This asymmetry compensates for the spanwise flow redistribution by creating higher axial velocity at the tip and reducing positive incidence at the fan rotor tip section
Solution Approach 2:
The system dynamically changes the geometric parameters of the IGV flap, specifically the stagger angle and twist distribution, based on operating conditions. At partial-speed conditions, the flexible portion is actuated to achieve a closed position that creates an asymmetric shape with modified twist distribution, thereby changing the flow parameters (axial velocity and incidence angle) to reduce harmful spanwise flow redistribution effects
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
This solution enhances partial-speed operability and flutter margin, reducing the risk of fan rotor mistuning and improving engine performance across various operational conditions by dynamically adjusting the IGV shape to match engine profiles at different speeds.
Implementation Method 1
The flexible portion of the flap is constructed from compliant material such as silicon rubber which may also incorporate internal stiffening fibers or filaments
Data Source
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AI summary
A variable shape inlet guide vane (IGV) system includes a variable-shape IGV flap (48) with a flexible portion (64) that enables the desired spanwise distribution of Cx, alpha, and beta at a fan rotor inlet. An actuation system (68) rotates a root section of the variable-shape IGV flap (48) to flex the flexible portion (64) such that the twisted shape of the flap (48) can reverse rather symmetrically during actuation from max open to max closed.