Hybrid Propulsion Engine for Compound Helicopters
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Solution Overview
Problem
Conventional single rotor helicopters are limited by retreating blade stall, which restricts their top speed, and compound helicopter designs attempting to overcome this issue face challenges with performance, stability, control, safety, and reliability.
Innovation Solution
A hybrid propulsion engine with a core turboshaft engine and a fan module that switches between closed and open configurations to provide propulsive thrust, combined with wings for lift compounding, allowing the rotorcraft to offload lift and thrust requirements from the main rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional single rotor helicopters are used, then the design is simple, but the top speed is limited due to retreating blade stall
Solution Approach 1:
The patent merges a conventional turboshaft engine with a fan module to create a hybrid propulsion system. The fan module integrates with the engine exhaust path, combining the core engine functionality with auxiliary thrust generation capability, thereby increasing top speed without proportionally increasing overall system complexity
Solution Approach 2:
The fan module is designed with movable inlet doors that can dynamically open or close based on flight conditions. During high-speed forward flight, the inlet doors open to activate the fan for additional thrust; during hover or low-speed flight, the inlet doors close to deactivate the fan, allowing the system to adapt its complexity to operational needs
2Speed
If advancing blade concept rotorcraft are used, then forward airspeed is increased, but high amounts of vibration occur causing crew fatigue and structural instability
Solution Approach 1:
The patent extracts the thrust generation function from the rotor blades themselves and relocates it to a separate fan module in the tail section. By using a pusher propeller configuration instead of advancing blades, the design achieves high forward airspeed without the vibration problems associated with blade stall and asymmetric loading
Solution Approach 2:
The fan module acts as an intermediary propulsion system that supplements the main rotor's thrust capability. Rather than modifying the main rotor blades to achieve high speed, the fan module provides additional thrust in a separate location, mediating between the main rotor system and the airframe to reduce vibration transmission
3Force
If compound helicopter designs with lift compounding are used, then lift requirement from main rotor is reduced, but performance, stability, control, safety and reliability remain elusive
Solution Approach 1:
The patent combines lift compounding through wings with propulsion compounding through the fan module in an integrated hybrid system. The wings provide lift relief during forward flight while the fan module provides thrust supplementation, and both systems work together to improve overall performance stability rather than operating independently
Solution Approach 2:
The hybrid propulsion system serves multiple functions: it provides thrust during high-speed forward flight, can be deactivated during hover operations, and works in conjunction with the wing lift system. This multi-functionality allows a single integrated system to address both lift and thrust requirements while maintaining reliability across different flight regimes
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
Enables high-speed forward flight while reducing vibration, crew fatigue, and structural instability, achieving higher speeds with improved stability and reduced acoustic signature.
Implementation Method 1
A thrust nozzle is configured to mix the exhaust gases from the exhaust stage with the bypass air from the bypass air exhaust stage and to discharge the exhaust gases and bypass air mixture to provide propulsive thrust
Implementation Method 2
a combustor section configured to mix the compressed air from the compressor section with fuel and ignite the compressed air and fuel mixture to form hot combustion gases
Implementation Method 3
a turbine section including a turbine operated responsive to the flow of the hot combustion gases from the combustor section, the turbine driving the compressor and the output shaft
Data Source
AI summary
A hybrid propulsion engine for a rotorcraft includes a core turboshaft engine having a gas path and an output shaft that provides torque to a main rotor. A fan module is disposed relative to the core turboshaft engine and is coupled to the output shaft. The fan module has a bypass air path that is independent of the gas path. A thrust nozzle is configured to mix exhaust gases from the core turboshaft engine with bypass air from the fan module and to discharge the mixture to provide propulsive thrust. In a turboshaft configuration, the fan module is closed to prevent the flow of bypass air therethrough such that the thrust nozzle does not provide propulsive thrust. In a turboshaft and turbofan configuration, the fan module is open allowing the flow of bypass air therethrough such that the thrust nozzle provides propulsive thrust, thereby supplying propulsion compounding for the rotorcraft.