Adaptive Phase Control for Distributed Propulsion Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Distributed Propulsion aircraft face challenges in controlling community noise, particularly due to complex acoustic directivity patterns from multiple propellers operating at the same rotational speed, which are difficult to predict and manage, especially when flying near noise-sensitive areas.
Innovation Solution
A method involving a phase generator module that adjusts the relative phase of individual propulsors to direct noise away from sensitive areas, using acoustic models to estimate and minimize sound pressure levels on the ground, allowing for real-time noise control during flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple propellers operate at the same rotational speed to provide distributed propulsion, then thrust generation capability is improved, but complex acoustic directivity patterns are generated that are difficult to predict and control
Solution Approach 1:
The patent segments the propulsion system into individually controllable propellers, each capable of independent phase control. This allows the acoustic fields from each propeller to be managed separately, enabling prediction and control of the overall acoustic directivity pattern while maintaining the thrust benefits of multiple propellers operating in parallel
Solution Approach 2:
The patent introduces dynamic phase control capability where each propeller's rotational phase can be independently adjusted in real-time. This dynamic control allows the system to adapt acoustic directivity patterns to different flight conditions and mission requirements, transforming the static acoustic behavior into a controllable dynamic system
2Object-generated harmful factors
If propulsors are strategically placed to reduce propulsor/propulsor interactions, then noise from coherent sources is reduced, but performance may be negatively affected
Solution Approach 1:
The patent changes the operational parameters of the propulsors by introducing independent phase control for each propeller. This allows the system to maintain optimal propulsor spacing for performance while using phase angle adjustments to control acoustic interference patterns, thereby reducing coherent noise without compromising the beneficial spacing arrangement
3Object-generated harmful factors
If low-noise propeller designs and reduced tip speed are implemented, then broadband noise is reduced, but effect on noise source directivity is limited
Solution Approach 1:
The patent introduces phase control as an intermediary mechanism between the propeller design and the resulting noise radiation pattern. While low-noise designs reduce the overall noise level, the phase control system acts as an intermediary that can independently shape and direct the remaining noise radiation, providing adaptability without requiring fundamental changes to propeller geometry
4Object-generated harmful factors
If phase control is applied to direct noise away from sensitive areas, then community noise is reduced, but real-time computation and control complexity increase
Solution Approach 1:
The patent implements a feedback control system where acoustic measurements or predictions from ground-based sensors are fed back to the aircraft's phase control system. This closed-loop approach allows real-time adjustment of propeller phases to actively direct noise away from sensitive areas, with the feedback mechanism managing the computational complexity by providing direct guidance on required phase adjustments
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
Effectively reduces spatially-averaged sound pressure levels over designated noise-sensitive areas by optimizing propeller phase angles, minimizing noise impact while maintaining flight performance.
Implementation Method 1
modifying operation of the DP system by selectively controlling the relative phase (azimuthal blade positions) of each of the aircraft's individual propulsors... purposefully varying the respective phases of the various propulsors to meet an acoustic target
Data Source
AI summary
A method for adaptive phase control of a distributed propulsion (DP) aircraft includes deriving an estimated source noise level of the aircraft's propulsors with respect to a designated low-noise area on the ground. Responsive to the estimated source noise level, a phase generator module estimates a ground noise level using the source noise level. The method includes determining an optimized set of relative azimuthal propulsor blade positions/phase angles, via the phase generator module, with such optimized phase angles being sufficient for reducing the estimated ground noise level. Phase control signals from a flight controller to the respective propulsors establishes the optimized set of relative phase angles, and thereby reduces community noise in the designated low-noise area. The DP aircraft includes an aircraft body, the flight controller, and the above-noted phase generator module.