Asymmetric Hybrid VTOL Propulsion for Cruise-Efficient Power Sharing
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Solution Overview
Problem
Current hybrid propulsion systems for multi-rotor aircraft, particularly for vertical take-off and landing (VTOL) aircraft, face inefficiencies in power consumption during cruise phases and limited emergency landing capabilities due to dependence on turbogenerators and battery mass, restricting operational versatility and accessibility.
Innovation Solution
A hybrid propulsion architecture featuring multiple turbogenerators and additional electrical energy storage assemblies allows for optimized energy distribution and reduced mass, enabling 'economic' operation modes and emergency reactivation of standby turbogenerators, with power distribution units converting and managing energy flow based on flight phases and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single turbogenerator is used to provide all necessary power, then the aircraft can achieve maximum power during take-off, but the turbogenerator operates far from its optimum specific consumption during cruising phase
Solution Approach 1:
The single turbogenerator is segmented into multiple turbogenerators (at least two), allowing the system to distribute power delivery across multiple units. During cruising, only one or a subset of turbogenerators operates at optimal load, while others can be idle or operate at reduced capacity, resolving the contradiction between maximum power availability and optimal fuel consumption.
Solution Approach 2:
The system dynamically adjusts the number of active turbogenerators based on flight phase and power requirements. The control system activates or deactivates specific turbogenerators to match demand, enabling the aircraft to operate with optimal efficiency during cruising while maintaining the capability to scale up to maximum power when needed.
2Reliability
If significant mass of batteries is carried to provide emergency power, then the aircraft can achieve extended emergency landing capability, but the overall aircraft mass increases
Solution Approach 1:
The electrical energy storage assemblies are merged with the turbogenerator system rather than being separate backup batteries. Each turbogenerator has an associated electrical energy storage assembly, creating an integrated hybrid system where the storage units serve dual purposes: smoothing power delivery during normal operation and providing emergency power when a turbogenerator fails, thereby reducing the total battery mass required.
Solution Approach 2:
The electrical energy storage assemblies associated with each turbogenerator can autonomously take over power delivery functions when their paired turbogenerator fails. This self-service capability eliminates the need for a separate, large centralized backup battery system, as the distributed storage units automatically provide emergency power without external intervention.
3Use of energy by moving object
If multiple turbogenerators are used to optimize cruising efficiency, then the system can operate in economical mode, but the device complexity increases
Solution Approach 1:
Each turbogenerator and its associated electrical energy storage assembly form a universal power module that can perform multiple functions: primary power delivery during normal operation, emergency backup power when other units fail, and power smoothing. This multi-functionality reduces the need for separate specialized components, offsetting the complexity of having multiple turbogenerators with a single versatile design.
Solution Approach 2:
The electrical energy storage assemblies are pre-charged and positioned in standby mode before emergencies occur. During normal operation, they continuously smooth power delivery and remain ready to immediately take over if a turbogenerator fails. This preliminary preparation eliminates the need for complex real-time decision-making during emergencies, simplifying the control architecture.
4Reliability
If each electrical energy storage assembly provides power corresponding to its associated generator, then the system can smooth power supply during normal operation, but additional storage capacity is needed for emergency reactivation
Solution Approach 1:
The electrical energy storage assemblies are merged into a unified system architecture where they simultaneously perform power smoothing during normal operation and provide emergency backup capacity. By pooling the storage resources across multiple turbogenerators, the system achieves both functions with reduced total storage capacity compared to having separate dedicated smoothing and emergency storage systems.
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
This solution enhances energy efficiency, reduces overall mass, and improves emergency landing capabilities by allowing seamless power transitions between generators and storage, increasing aircraft reliability and fuel savings while expanding operational envelopes.
Implementation Method 1
a first heat engine driving a first electricity generator and a second heat engine driving a second electricity generator
Implementation Method 2
each of these at least two energy branches selectively supplying a plurality of electric motors ensuring the propulsion and/or lift of the aircraft
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a hybrid propulsion system (10) for a vertical take-off and landing (VTOL) aircraft comprising at least one combustion engine (120, 140) driving an electricity generator (122, 142), at least one electrical energy storage assembly (16; 18A, 18N) associated with each electricity generator and defining with each electricity generator an energy branch, a plurality of electric motors (200, 220, 240, 260) actuating a same plurality of rotors (202, 222, 242, 262) providing together the propulsion and/or the lift of the aircraft, and an electrical power and distribution unit (28) supplying power to the plurality of electric motors from the electricity generator and/or the electrical energy storage assembly according to a pre-established flight phase, the system comprising at least two energy branches having an asymmetrical configuration and each selectively supplying, via the power and electrical distribution unit (28), all or part of the plurality of electric motors and in which the electricity generators of the internal combustion engines have between them a power ratio of between 1.2 and 1.4 so as to allow the most powerful to alone supply the electrical power required by the aircraft in all flight conditions.