Gas Turbine Fan Arrangement Drag Reduction
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Solution Overview
Problem
Scaling up gas turbine engine components does not proportionally increase power or efficiency, leading to issues like increased drag and installation challenges, particularly in aircraft applications, where a larger engine may not fit under the wing due to increased drag and mass distribution.
Innovation Solution
Optimizing engine parameters by maintaining an engine area ratio between 1.7 and 3, with a fan face area to turbine diameter ratio, and a core length to turbine diameter ratio, to reduce drag and facilitate closer wing mounting, while using a gearbox to drive the fan at a lower rotational speed than the core shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the overall size of a gas turbine engine is increased to improve power output, then power output is improved, but drag increases and installation becomes difficult
Solution Approach 1:
The patent applies parameter changes by optimizing the engine area ratio (fan face area to turbine diameter) to a specific range of 1.7 to 3.0, and the core length to turbine diameter ratio to 0.3 to 0.7. These parameter optimizations allow the engine to achieve improved propulsive efficiency and reduced drag while maintaining high power output, resolving the contradiction between power increase and drag reduction.
2Power
If the overall size of a gas turbine engine is increased to improve power output, then power output is improved, but installation difficulty increases
Solution Approach 1:
The patent optimizes geometric parameters including the engine area ratio (1.7 to 3.0) and core length to turbine diameter ratio (0.3 to 0.7), which enables the engine to maintain a compact configuration relative to its power output. This allows the engine to be installed in constrained spaces such as under aircraft wings while still delivering high power performance.
3Power
If engine components are scaled proportionally to increase size, then power output increases, but propulsive efficiency does not improve proportionally
Solution Approach 1:
The patent employs non-proportional scaling by optimizing specific geometric parameters independently. The engine area ratio is maintained between 1.7 to 3.0 and the core length to turbine diameter ratio between 0.3 to 0.7, which differs from simple proportional scaling. This selective parameter optimization improves propulsive efficiency while achieving the desired power output increase.
Data Source
AI summary
A gas turbine engine for an aircraft having an engine core configured with a turbine, a compressor, and a core shaft connecting the turbine to the compressor. A fan located upstream of the engine core, the fan comprising a plurality of fan blades, with a nacelle surrounding the gas turbine engine, and a bypass duct outlet guide vane extending radially across the bypass duct between an outer surface of the engine core and the inner surface of the nacelle. An outer wall axis is defined joining the radially outer tip of the trailing edge of the bypass duct outlet guide vane and the rearmost tip of the inner surface of the nacelle. An outer bypass duct wall angle is defined as the angle between the outer wall axis and the centreline, and the outer bypass duct wall angle is in a range from −15 to −2.5 degrees.