Variable Camber Stator Vanes for Gas Turbine Intake Flow Balancing
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to non-axisymmetric airflow caused by factors like droop and crosswinds, leading to aerodynamic losses, buffet flutter, and increased fan forcing, which are exacerbated by obstructions such as pylons and radial drive struts that distort the laminar flow and create back pressure.
Innovation Solution
The design involves a gas turbine engine with stator vanes that are strategically positioned and configured to balance circumferentially varying back pressure from obstructions with forward flow pressure, using a combination of stagger and camber variations to achieve momentum balance across the flow path, thereby reducing fan forcing and stress on the fan blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stator vanes are configured with uniform stagger and camber, then manufacturing is simple, but fan forcing and aerodynamic losses increase due to non-axisymmetric flow and back pressure from obstructions
Solution Approach 1:
The patent applies local quality by varying the stagger and camber angles of stator vanes at different circumferential positions. Specifically, stator vanes upstream of obstructions have different stagger/camber configurations compared to those downstream, creating localized geometric variations that compensate for back pressure distortions and reduce fan forcing while maintaining manufacturing feasibility through systematic angle variations.
Solution Approach 2:
The patent implements asymmetry by introducing non-uniform stagger and camber variations in the stator vane configuration. The asymmetric geometry is designed to counteract the non-axisymmetric flow patterns caused by engine droop, crosswinds, and obstruction back pressure, thereby reducing aerodynamic losses and fan forcing through balanced momentum distribution.
2Strength
If stator vanes are positioned to minimize fan forcing, then fan blade stress is reduced, but other efficiency-reducing problems like aerodynamic losses and buffet flutter are exacerbated
Solution Approach 1:
The patent applies parameter changes by systematically varying the stagger and camber angles of stator vanes at different circumferential positions. These geometric parameter variations are designed to balance the momentum of airflows affected by obstruction back pressure, thereby reducing fan forcing and blade stress while simultaneously improving overall flow uniformity to reduce aerodynamic losses and buffet flutter.
Solution Approach 2:
The patent implements a counterbalancing approach where stator vanes upstream of obstructions are configured with specific stagger and camber angles that create opposing momentum effects to counteract the back pressure from obstructions. This anti-weight principle balances the non-axisymmetric flow patterns, reducing fan forcing on blades while maintaining flow uniformity to minimize other efficiency losses.
3Loss of energy
If detailed analytical modeling is performed to optimize stator vane positions, then fan forcing can be minimized, but the complexity and computational requirements increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-configuring stator vanes with specific stagger and camber angles during the design phase based on anticipated back pressure patterns from known obstruction locations. This preliminary geometric configuration eliminates the need for complex real-time analytical modeling and optimization, as the vanes are pre-positioned to balance momentum and reduce fan forcing under expected operating conditions.
Solution Approach 2:
The patent segments the stator vane configuration into distinct zones based on their positional relationship to obstructions. Stator vanes are categorized as being upstream or downstream of obstructions, with each zone having optimized stagger and camber angles. This segmentation simplifies the design process by breaking down the complex optimization problem into manageable segments with specific geometric parameters.
Data Source
AI summary
Within an intake for a gas turbine engine provision is provided through stator vanes 25, 45 in the stator whereby back pressure from a necessary obstruction 34, 46 can be utilised to balance forward pressure variations caused by intake droop or crosswinds in order to reduce those forward pressure detriments for more efficient engine operation according to a desired objective regime. Typically the flow through the intake 20 is analysed and then an appropriate positioning of the stator vanes 25, 45 determined in order to provide approximate balance between the forward pressures and back pressures. Normally, a combination of camber variation of stator vanes 45a and stagger variation of stator vanes 45b are utilised in order to achieve a desired momentum balance around the circumference of the intake 20. It will be understood that both the forward pressures and the back pressures are differentially variable about the circumference such that one opposes the other.