Composite Fan and OGV Acoustic Spacing for Turbine Noise Reduction
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Solution Overview
Problem
Conventional methods of reducing gas turbine engine noise are insufficient to meet 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, combined with the use of composite fan blades, which allows for larger blade sizes and reduced fan pressure ratios, and incorporating a reduction gearbox to optimize noise reduction and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional noise reduction methods are used, then noise levels decrease, but performance parameters (weight, drag, fuel consumption) deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing the acoustic spacing between fan blades and OGVs to a specific multiple of the fan blade spacing. This parameter optimization reduces noise generation at the source by controlling the interaction between fan blade wakes and OGVs, achieving noise reduction without requiring additional noise control components that would adversely affect weight, drag, and fuel consumption.
Solution Approach 2:
The patent introduces a new dimensional parameter - the acoustic spacing ratio (multiple of fan blade spacing) - as a design criterion for OGV positioning. By establishing this specific spatial relationship dimension, the patent achieves noise reduction through geometric configuration rather than through conventional noise control methods that add weight and complexity.
2Object-generated harmful factors
If acoustic spacing is optimized, then noise generation reduces, but device complexity increases
Solution Approach 1:
The patent simplifies the design approach by defining acoustic spacing as a straightforward multiple of the fan blade spacing parameter. This parameter-based definition allows designers to calculate the optimal OGV position using simple multiplication rather than complex acoustic simulations, reducing design complexity while achieving noise reduction.
3Object-generated harmful factors
If fan blade and OGV spacing is adjusted, then acoustic performance improves, but aerodynamic efficiency may deteriorate
Solution Approach 1:
The patent optimizes the acoustic spacing parameter to a specific multiple of fan blade spacing that simultaneously satisfies both noise reduction and aerodynamic efficiency requirements. By carefully selecting this parameter, the patent positions OGVs to minimize noise-generating interactions while maintaining favorable flow conditions for propulsive efficiency.
Solution Approach 2:
The patent replaces complex active noise control systems with a passive geometric configuration approach. By substituting mechanical/acoustic active control with a carefully designed spatial relationship between components, the patent achieves noise reduction without the energy penalties and complexity of active systems, preserving propulsive efficiency.
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 acoustic spacing parameter, in combination with composite fan blades that include one or both of a fan leading edge to trailing edge compression factor (FLTCF) and a fan leading edge to trailing edge opening ratio (FLTOR), provide improved performance and reduced acoustic noise.