AC TeDP Propulsor Noise Reduction via Varying Motor Pole Counts
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Solution Overview
Problem
Alternating current (AC) type turboelectric distributed propulsion (TeDP) systems cannot vary the speed of propulsor fans to spread noise spectrum across multiple frequencies, making them appear louder compared to direct current (DC) type systems, despite being smaller and lighter, due to the need for synchronized motor speeds with turbo generators.
Innovation Solution
An AC-type TeDP system that selects different rotational frequencies for each propulsor fan and varies the pole pairs of propulsor motors to operate fans at distinct speeds, broadening the noise spectrum and reducing sound pressure levels without requiring individual variable speed drives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If AC-type TeDP systems use synchronized motor speeds with turbo generators, then the system achieves smaller size and weight, but the fan noise cannot be spread across multiple frequencies resulting in higher sound pressure levels
Solution Approach 1:
The patent changes the electrical frequency parameter supplied to each propulsor motor independently. By varying the frequency from the base frequency (synchronized with turbo generator) to different frequencies for different propulsors, the system spreads fan noise across multiple frequencies while maintaining AC-type TeDP architecture, thus reducing sound pressure levels without sacrificing size and weight advantages
Solution Approach 2:
The patent introduces dynamic frequency adjustment capability where each propulsor can operate at different frequencies dynamically. This allows the system to adapt noise characteristics in real-time while maintaining the lightweight AC-type architecture, resolving the contradiction between fixed synchronized operation and noise spectrum spreading
2Object-generated harmful factors
If DC-type TeDP systems use variable speed drives to spread noise spectrum, then fan noise is reduced across multiple frequencies, but the system size and weight increase
Solution Approach 1:
The patent makes the AC-type TeDP system universally capable of both synchronized operation (for efficiency) and independent frequency control (for noise reduction). By integrating frequency variation capability into the AC system architecture, it achieves the noise spectrum spreading function previously only available in DC systems, eliminating the need to choose between noise reduction and weight savings
3Device complexity
If AC-type TeDP systems operate all propulsors at the same synchronized frequency, then the system maintains simplicity and weight efficiency, but additive noise from multiple fans increases overall sound pressure level
Solution Approach 1:
The patent applies local quality by allowing each propulsor to have its own frequency characteristic while maintaining overall system coordination. Each propulsor receives a slightly different frequency from the base frequency, creating local variations in operating parameters that spread noise spectrum locally at each fan while the control system maintains a relatively simple architecture
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
The system achieves size and weight savings similar to AC-type TeDP systems while reducing fan noise by varying pole counts to spread noise frequencies, eliminating or reducing additive noise without large variable speed drives.
Implementation Method 1
an alternating current (AC) generator of an AC type electric distribution system; means for selecting a first rotational frequency for a first fan of a first propulsor that is being driven by an AC generator
Implementation Method 2
means for selecting a second rotational frequency for a second fan of a second propulsor that is also being driven by the AC generator; means for selecting a minimum pole pair offset for differentiating a first quantity of pole pairs of a first motor of the first propulsor from a second quantity of pole pairs of a second motor of the second propulsor
Data Source
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Figure 3A
AI summary
An alternating current type electric propulsion system is described that includes an AC generator and a plurality of propulsors electrically coupled to the AC generator. A first propulsor from the plurality of propulsors includes a first motor that drives a first fan of the first propulsor at a first speed. A second propulsor from the plurality of propulsors comprises a second motor that drives a second fan of the second propulsor at a second speed that is different than the first speed.