Variable Outer Guide Vanes for Turbofan Drag Reduction
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Solution Overview
Problem
High-bypass turbofan engines face challenges in aerodynamic drag and thrust efficiency, particularly during trans-oceanic flights, due to the physical size and aerodynamic drag imposed by an inoperative engine, which limits the range and fuel efficiency of twin-engine aircraft.
Innovation Solution
The design incorporates subsonic turbofan engines with variable outer guide vanes (OGVs) that transition between nominal and reduced-drag configurations, optimizing airflow to minimize drag and enhance thrust efficiency, even when one engine is inoperative.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-bypass turbofan engines are used to improve fuel efficiency and reduce noise, then fuel efficiency and acoustic performance are improved, but aerodynamic drag increases and range is limited
Solution Approach 1:
The OGVs are made dynamically adjustable through a control system that pivots them between a first position (reducing swirl during normal operation) and a second position (reducing drag during engine-out conditions). This dynamic reconfiguration allows the engine to adapt to different operational states, resolving the contradiction between maintaining thrust efficiency and minimizing drag.
Solution Approach 2:
The invention changes the orientation parameter of the OGVs based on engine operational status. During normal operation, OGVs are positioned to optimize thrust by reducing swirl. During engine-out conditions, they are repositioned to minimize drag. This parameter change allows the system to achieve both low drag and high efficiency under different conditions.
2Power
If engine size is increased to provide sufficient thrust for ETOPS requirements, then thrust capability is improved, but aerodynamic drag from inoperative engine increases
Solution Approach 1:
The OGV control system dynamically adjusts vane positions based on engine operational status. When one engine becomes inoperative, the OGVs on that engine are pivoted to a second position that minimizes drag while the operative engine maintains thrust. This dynamic adaptation allows the aircraft to maintain ETOPS capability without suffering excessive drag from the inoperative engine.
Solution Approach 2:
The invention converts the harmful effect of the inoperative engine (which creates drag) into a beneficial situation by using the OGVs to actively manage the airflow. The OGVs transform the potential harm of engine failure into an opportunity to optimize airflow patterns, reducing drag and maintaining range.
3Power
If OGVs are positioned to reduce swirl during normal operation, then thrust efficiency is improved, but drag increases during engine-out conditions
Solution Approach 1:
The OGVs are configured to pivot between two distinct positions based on engine operational status. During normal operation, they are positioned to reduce swirl and maximize thrust efficiency. During engine-out conditions, they pivot to a second position that minimizes drag. This dynamic repositioning resolves the contradiction by allowing the OGVs to serve different functions under different operational conditions.
Solution Approach 2:
The orientation parameter of the OGVs is changed based on engine status. The control system monitors engine operation and adjusts the OGV angle accordingly, changing from a thrust-optimization parameter setting to a drag-reduction parameter setting when engine failure is detected.
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 configuration reduces drag force and enhances fuel efficiency and range by aligning OGVs with the airflow direction during engine-out conditions, ensuring extended maximum range and efficient operation under reduced thrust scenarios.
Implementation Method 1
a fan with a plurality of fan blades configured to revolve about an engine longitudinal axis of the subsonic turbofan engine to accelerate an air flow
Implementation Method 2
the respective OGV is oriented to reduce a swirl in the air flow downstream of the fan
Implementation Method 3
at least a portion of the respective OGV is increasingly aligned with the downstream direction relative to the nominal configuration
Data Source
AI summary
Subsonic turbofan engines with variable outer guide vanes (OGVs) and associated methods. A subsonic turbofan engine includes an engine core configured to generate a torque, a fan configured to accelerate an air flow, an engine nacelle, and a plurality of OGVs positioned downstream of the fan. Each OGV is configured to transition among a plurality of OGV configurations defined between and including a nominal configuration and a reduced-drag configuration. The subsonic turbofan engine is configured to operate only at subsonic speeds. In examples, methods of operating a subsonic turbofan engine include transitioning each of a plurality of OGVs from a nominal configuration to a reduced-drag configuration. Transitioning each OGV from the nominal configuration to the reduced-drag configuration is performed while the subsonic engine operates at subsonic speeds.