Variable Pitch Rotor Blades for Gas Turbine Bypass Ratio Control
Solution Overview
Problem
Gas turbine engine efficiency decreases due to variations in compressor section pressure ratio, which are not effectively managed by conventional methods that alter upstream stator swirl angles and fixed rotor pitch, leading to reduced overall cycle pressure ratio and thermodynamic efficiency.
Innovation Solution
A gas turbine engine with a variable pitch rotor assembly that adjusts blade stagger angles to maintain optimal leading edge incidence and constant absolute tangential velocity across varying bypass ratios, eliminating the need for upstream swirl angle variability and reducing pressure ratio fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods alter upstream stator swirl angles and use fixed rotor pitch, then the engine can operate with simple fixed geometry components, but the compressor section pressure ratio varies and thermodynamic efficiency decreases
Solution Approach 1:
The patent applies variable pitch rotor blades that can dynamically adjust their angle of attack in response to changing flow conditions. This dynamic adjustment maintains optimal blade incidence angles across varying bypass ratios, preserving compressor pressure ratio and thermodynamic efficiency without requiring complex variable geometry stators upstream.
Solution Approach 2:
The invention changes the rotor blade pitch parameter to adapt to different operating conditions. By varying the blade pitch angle, the system maintains optimal performance across a range of bypass ratios, avoiding the efficiency losses associated with fixed geometry components.
2Loss of energy
If variable pitch rotor blades are implemented to maintain optimal leading edge incidence, then thermodynamic efficiency is maintained across varying bypass ratios, but device complexity increases
Solution Approach 1:
The variable pitch rotor blades provide dynamic adaptation to changing flow conditions, maintaining optimal blade incidence angles across varying bypass ratios. This dynamic capability preserves compressor pressure ratio and thermodynamic efficiency while avoiding the need for complex variable geometry stators upstream.
Solution Approach 2:
The invention applies variable pitch specifically to the rotor blades where it is most effective, rather than making the entire compressor geometry variable. This localized application of complexity achieves the desired performance benefits with minimal additional system complexity.
3Device complexity
If fixed rotor pitch is used, then device complexity is reduced, but the compressor section pressure ratio varies and efficiency decreases
Solution Approach 1:
The variable pitch rotor blades dynamically adjust to maintain stable compressor section pressure ratio across varying bypass ratios. This dynamic adjustment compensates for changing flow conditions, preserving the stability of the pressure ratio without requiring complex upstream variable geometry components.
Solution Approach 2:
By changing the rotor blade pitch parameter in response to varying bypass ratios, the system maintains stable compressor pressure ratio and avoids the performance degradation associated with fixed pitch configurations.
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 approach maintains consistent overall cycle pressure ratio and thermodynamic efficiency across different bypass ratios, reducing losses and facilitating operation over a wider range of conditions compared to conventional configurations.
Implementation Method 1
adjusts blade stagger angles to maintain optimal leading edge incidence and constant absolute tangential velocity
Data Source
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AI summary
A gas turbine engine includes a fan section (12). A splitter (52) is downstream of the fan section (12) and at least partially defines a secondary flow path (34) on a radially outer side and an inner flow path (36) on a radially inner side. A variable pitch rotor assembly (56) is located at an inlet to the inner flow path (36) and includes a plurality of variable pitch rotor blades (58).