Rotorcraft Powerplant Speed Regulation for In-Flight Noise Reduction
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Solution Overview
Problem
Current rotorcraft speed regulation methods cannot effectively reduce acoustic footprint in flight without compromising safety or giving the impression of engine failure, and they do not account for varying flight conditions and power needs.
Innovation Solution
A method that activates a regulation loop at predetermined height and speed thresholds, gradually reducing the main rotor's rotational speed while maintaining safety margins, using a secondary engine to support the main engine and ensure sufficient lift and power during critical phases, and automatically adjusting the pitch of the rotor blades to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the rotational speed NR0 is reduced to minimize acoustic footprint, then noise pollution is reduced, but the rotor's lift margin becomes insufficient for emergency maneuvers
Solution Approach 1:
The system pre-establishes a secondary engine as a backup power source before any noise reduction operation begins. This secondary engine is kept ready to immediately compensate for lift margin deficiencies if the primary engine reduces rotational speed NR0 below nominal values, thereby allowing noise minimization without compromising emergency maneuver capability
Solution Approach 2:
The system dynamically adjusts the rotational speed NR0 as a variable parameter rather than maintaining a fixed nominal value. By controlling NR0 to vary between 98% and 103% of nominal depending on flight conditions, the system optimizes the balance between acoustic footprint reduction and maintaining sufficient lift margin for safety
2Object-generated harmful factors
If the rotational speed NR is reduced below nominal value to reduce noise, then acoustic comfort is improved, but the rotorcraft cannot perform critical flight phases such as landing or takeoff
Solution Approach 1:
The system implements dynamic control of rotational speed NR0 based on real-time flight conditions. The speed is allowed to deviate from nominal values (between 98%-103%) according to the specific flight phase, ensuring high performance during critical operations like takeoff and landing while enabling noise reduction during less critical phases
Solution Approach 2:
The secondary engine is prepared in advance as a power reserve to provide additional margin during critical flight phases, enabling the primary engine to operate at reduced speeds for noise reduction while maintaining overall flight performance capability when needed
3Object-generated harmful factors
If automatic speed regulation is applied during ground maneuvers to limit noise, then acoustic comfort during boarding is improved, but no regulation is suggested during flight phases
Solution Approach 1:
The control system is designed with universal applicability across all flight phases. The same regulatory mechanism that operates during ground maneuvers is extended to function during flight phases, allowing noise reduction benefits to be realized throughout the entire operational envelope of the rotorcraft
Solution Approach 2:
The secondary engine is pre-configured and ready to support noise reduction operations during flight phases, enabling the system to extend ground-based noise regulation成功经验 to flight operations without requiring additional hardware or complex modifications
Data Source
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AI summary
The present invention relates to a rotorcraft and a method for regulating a drive system (2) of a rotorcraft (1), said drive system (2) comprising two engine groups (3 and 4) and a main power transmission box (5), the two engine groups (3 and 4) being capable of mechanically driving said main power transmission box (5) in order to rotate a main output shaft (6) of said main power transmission box (5), said main output shaft (6) being rotationally fixed to a main rotor (7) of said rotorcraft (1), said two engine groups (3 and 4) comprising a first engine group (3) comprising at least one main engine (13). According to the invention, such a regulation method comprises a regulation step consisting of regulating a rotational speed of said at least one main engine (13) by progressively reducing a current setpoint (NRi, Fig.2) of an increment i as a percentage of the current setpoint (NRi, Fig. 2) per second.