Fan Inlet Length Optimization for Gas Turbine Weight and Drag Reduction
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Solution Overview
Problem
Longer inlets in gas turbine engines, while providing better noise reduction, increase weight and external drag, and introduce additional load on the engine structure due to airflow during takeoff, necessitating a balance between noise reduction and structural integrity.
Innovation Solution
A gas turbine engine design with a fan having a diameter-based dimensional relationship of L/D between 0.2 and 0.45, where L is the length of the inlet portion and D is the fan diameter, allowing for a shorter inlet length that reduces weight, drag, and structural load while maintaining acceptable noise characteristics through a low pressure ratio fan and geared architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the inlet length is increased to improve noise reduction, then noise attenuation is improved, but weight increases and external drag increases
Solution Approach 1:
The patent applies parameter changes by optimizing the inlet length-to-fan-diameter ratio (L/D) to a specific range (0.25-0.45), representing a departure from conventional longer inlets. This dimensional parameter optimization achieves effective noise attenuation while significantly reducing inlet weight and external drag compared to traditional designs with L/D ratios greater than 0.5
2Object-affected harmful factors
If the inlet length is increased to improve noise reduction, then noise attenuation is improved, but external drag increases
Solution Approach 1:
The patent optimizes the inlet length-to-fan-diameter ratio (L/D) to a specific range (0.25-0.45), representing a departure from conventional longer inlets. This dimensional parameter optimization achieves effective noise attenuation while significantly reducing inlet weight and external drag compared to traditional designs with L/D ratios greater than 0.5
3Object-affected harmful factors
If the inlet length is increased to improve noise reduction, then noise attenuation is improved, but structural load increases
Solution Approach 1:
The patent optimizes the inlet length-to-fan-diameter ratio (L/D) to a specific range (0.25-0.45), representing a departure from conventional longer inlets. This dimensional parameter optimization achieves effective noise attenuation while significantly reducing inlet weight and external drag compared to traditional designs with L/D ratios greater than 0.5
4Object-affected harmful factors
If a low pressure ratio fan is used to reduce fan source noise, then noise characteristics are improved, but inlet length requirement is reduced
Solution Approach 1:
The patent employs a low pressure ratio fan (1.20-1.50) operating at lower tip speeds to reduce fan source noise. This operational parameter change allows for a corresponding reduction in inlet length (L/D ratio of 0.25-0.45) while maintaining acceptable noise characteristics, resolving the contradiction between noise reduction requirements and inlet dimensional constraints
Data Source
AI summary
A gas turbine engine assembly may include, among other things, a fan section including a fan, the fan including a plurality of fan blades, a diameter of the fan having a dimension D, each fan blade having a leading edge, and a forward most portion on the leading edges of the fan blades in a first reference plane, a geared architecture, a turbine section including a high pressure turbine and a low pressure turbine, the low pressure turbine driving the fan through the geared architecture, a nacelle surrounding the fan, the nacelle including an inlet portion forward of the fan, a forward edge on the inlet portion in a second reference plane, and a length of the inlet portion having a dimension L between the first reference plane and the second reference plane. A dimensional relationship of L/D may be between 0.30 and 0.40.