Fan Blade–OGV Spacing for Quiet Propulsive Efficiency
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Solution Overview
Problem
Conventional methods of reducing gas turbine engine noise, such as varying fan pressure ratio, are insufficient to meet increasingly stringent community noise requirements without negatively impacting performance in terms of weight, drag, and specific fuel consumption.
Innovation Solution
Implementing a specific range of acoustic spacing between fan blades and OGVs, along with optimized blade effective acoustic length, chord length, span, stagger angle, and radius ratio, to maintain propulsive efficiency while reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional methods of reducing gas turbine engine noise (varying fan pressure ratio) are used, then noise levels decrease, but performance deteriorates in terms of weight, drag, and specific fuel consumption
Solution Approach 1:
The patent applies parameter changes by optimizing the acoustic spacing ratio between fan blades and OGVs to a specific range (0.5 to 2.0), and by adjusting blade geometric parameters including effective acoustic length, chord length, span, stagger angle, and radius ratio. These parameter optimizations reduce noise through acoustic interference effects while maintaining propulsive efficiency and avoiding penalties in fuel consumption, weight, or drag
2Object-generated harmful factors
If acoustic spacing between fan blades and OGVs is optimized, then noise is reduced, but propulsive efficiency must be maintained
Solution Approach 1:
The patent optimizes multiple blade parameters simultaneously - acoustic spacing ratio (0.5 to 2.0), effective acoustic length (0.05 to 0.15 times fan diameter), chord length (0.08 to 0.12 times fan diameter), span (0.4 to 0.6 times fan diameter), stagger angle (15 to 30 degrees), and radius ratio (0.3 to 0.5) - to achieve noise reduction through acoustic interference while maintaining favorable propulsive efficiency
Solution Approach 2:
The patent converts the harmful noise generated by fan blade-OGV interaction into a beneficial effect by designing the acoustic spacing to create destructive interference patterns that reduce noise radiation, while the same geometric configuration maintains efficient airflow and propulsive performance
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
Achieves a balance between noise reduction and performance improvements, including reduced fuel consumption and emissions, without significant penalties on engine drag or weight.
Implementation Method 1
an acoustic spacing ratio, determined from a blade effective acoustic length, a number of OGVs, and an axial spacing between the fan and the OGVs
Data Source
AI summary
A gas turbine engine comprises a fan, a core turbine engine coupled to the fan, a fan case housing the fan and the core turbine engine, a plurality of outlet guide vanes extending between the core turbine engine and the fan case, and an acoustic spacing. The fan comprises a plurality of fan blades that define a fan diameter and a BEAL. The fan case comprises an inlet and an inlet length between the inlet and the fan. The acoustic spacing comprises a distance between the fan and the plurality of outlet guide vanes, and in combination with the BEAL determines an acoustic spacing ratio of the gas turbine engine. The combination of acoustic spacing and corrected specific thrust provide enhanced propulsive efficiency.