Variable Pitch Fan Blade Assembly for Gas Turbine
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Solution Overview
Problem
Existing aero gas turbine engines with variable inlet and exit guide vanes require extra length and complexity to achieve variable geometry, which affects fan bypass performance, especially at highly closed IGV positions, and are not optimized for low power conditions.
Innovation Solution
A variable pitch fan blade assembly with a sync ring and hydraulic actuation system, where hydraulic fluid lines pass through the shaft and fixed pitch blades to adjust the pitch of bypass stream flow blades, eliminating the need for variable inlet and exit guide vanes, and using lightweight composite materials for the fan blades to reduce centrifugal load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable inlet guide vanes and variable exit guide vanes are used to adjust fan bypass stream flow and pressure ratio, then the ability to control bypass performance is improved, but the device complexity and length increase
Solution Approach 1:
The patent extracts the variable geometry functionality from the inlet and exit guide vanes and concentrates it solely in the fan blades. By removing the need for variable inlet guide vanes and variable exit guide vanes, the design simplifies the overall structure while maintaining bypass flow control capability through fan blade pitch adjustment alone.
Solution Approach 2:
The fan blades are given a dual function: they serve as both the primary propulsion element and the bypass flow control mechanism. By making the fan blades variable pitch, they can simultaneously control the core stream and bypass stream characteristics, eliminating the need for separate variable guide vane systems.
2Adaptability or versatility
If variable inlet guide vanes are used to control bypass stream flow, then bypass performance adjustment is improved, but the inlet guide vane length and complexity increase
Solution Approach 1:
The patent removes the variable inlet guide vane component entirely from the design. The functionality previously requiring a long, complex variable IGV structure is transferred to the fan blades, which can achieve the same bypass flow control objective without extending the inlet guide vane length.
3Reliability
If full chord shrouds are used to separate core stream flow from bypass stream flow, then flow separation is improved, but the device complexity and weight increase
Solution Approach 1:
Instead of using full chord shrouds along the entire blade span, the patent applies shrouds only in specific regions where flow separation is most critical. This localized approach maintains effective core and bypass stream separation while reducing the overall amount of shroud material and structural complexity.
Solution Approach 2:
The shrouds are constructed using composite materials that provide the necessary structural integrity and flow separation functionality with reduced weight and complexity compared to traditional solid shroud structures.
4Adaptability or versatility
If variable inlet guide vanes and variable exit guide vanes are used to achieve variable geometry, then bypass performance control is improved, but manufacturing complexity increases
Solution Approach 1:
The patent eliminates two separate variable geometry mechanisms (variable IGV and variable EGV) and consolidates the variable geometry functionality into a single fan blade pitch system. This reduction in the number of moving parts and mechanisms significantly simplifies manufacturing requirements.
Solution Approach 2:
The patent merges the variable geometry functionality previously distributed across multiple components (inlet guide vanes, exit guide vanes, and fan blades) into a unified fan blade pitch system. This consolidation reduces the total number of parts that need to be manufactured and assembled.
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 design improves low power performance, reduces the number of moveable parts, and enables adaptive operation for VTOL aircraft by maintaining efficient fan bypass performance without the need for additional guide vanes, enhancing the engine's versatility and efficiency.
Implementation Method 1
a sync ring is contained in a slow splitter and uses a hydraulic pressure to move the sync ring and vary the pitch of the bypass fan blades
Implementation Method 2
The bypass flow fan blades can be constructed of light weight composites to reduce the centrifugal load on the shroud and inner blade span
Data Source
AI summary
A variable pitch fan assembly for an aero gas turbine engine that includes a row of fixed pitch blades in a core stream flow and a row of variable pitch blades in a bypass stream flow, and where a sync ring with a number of hydraulic actuators within a flow splitter of the fan stage is used to vary a pitch of each of the bypass stream flow blades. Hydraulic fluid lines pass through the shaft and through the fixed pitch fan blades into the hydraulic actuators to move the sync ring and vary a pitch of the variable pitch bypass flow fan blades.