Open Rotor Free Turbine Isolation for Ground Safety Control
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Solution Overview
Problem
Open rotor aircraft propulsion systems pose safety risks due to larger fan/rotor diameters and lack of a fan duct, increasing the distance to airfoils and wings, which can bring rotating blades closer to ground personnel and cargo doors, enhancing safety hazards.
Innovation Solution
An aircraft propulsion system with a power turbine isolation system and flow diverter that selectively directs engine airflow into or bypasses the power turbine, and an optional brake mechanism to stop rotor rotation when necessary, reducing safety risks by decoupling the open propulsor rotor from its drive mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the fan rotor diameter is increased to increase bypass airflow mass and thrust, then propulsion performance is improved, but the distance to airfoils and wings increases which brings the rotating blades closer to ground personnel and cargo doors, enhancing safety hazards
Solution Approach 1:
The patent extracts the power turbine from the direct drive path of the propulsor rotor by introducing a free turbine configuration. The power turbine is aerodynamically isolated from the propulsor rotor through a transition duct with flow diverters, allowing the rotor to be stopped or slowed during ground operations while the power turbine can still operate independently to drive the rotor when needed for flight operations.
Solution Approach 2:
The patent implements dynamic control of the flow path using movable flow diverters in the transition duct. These diverters can selectively direct airflow either to the power turbine or bypass it, enabling the system to dynamically adjust rotor speed based on operational requirements - allowing rotor stopping for ground safety while maintaining flight capability.
2Length of moving object
If the fan rotor is positioned further forward to increase distance from airfoils and wings, then safety regarding blade clearance is improved, but the rotor moves closer to cargo doors and other areas accessed by ground personnel, increasing safety risks
Solution Approach 1:
The patent extracts the power turbine function from the direct mechanical connection to the propulsor rotor. By placing the power turbine in the engine core with aerodynamic isolation through the transition duct system, the rotor positioning is decoupled from the power extraction mechanism, allowing optimal positioning for both safety and performance without direct mechanical coupling constraints.
Solution Approach 2:
The transition duct with flow diverters acts as an intermediary between the engine core and the propulsor rotor. This intermediary system allows independent control of the power turbine and rotor, enabling the rotor to be positioned optimally for safety clearance while the flow diverter mediates the power transmission only when needed.
3Adaptability or versatility
If a flow diverter system is added to aerodynamically isolate the power turbine, then safety control capability is improved, but device complexity increases
Solution Approach 1:
The transition duct serves multiple functions: it connects the engine core to the power turbine, provides aerodynamic isolation, and incorporates flow diverters for safety control. This multi-functional design achieves safety control capability without proportionally increasing complexity, as the same structural element (transition duct) performs multiple roles including housing the flow diverter mechanism.
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 effectively reduces safety risks by stopping or slowing the open propulsor rotor during ground operations, ensuring safety for ground personnel and preventing damage, while maintaining engine functionality.
Implementation Method 1
A flow diverter is selectively configured to, in a first mode cause engine airflow to flow into the power turbine, and in a second mode restrict the engine airflow from flowing into the power turbine
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
An assembly for an aircraft propulsion system (100) includes an open propulsor rotor (30A) driven by a power turbine section disposed in the engine core (40). A power turbine isolation system (200) disposed between an LP turbine section (36B) and the power turbine section includes a transition duct (210) therebetween and a flow diverter (220). The flow diverter (220) is selectively configured to direct engine core flow into the power turbine section to drive the propulsor rotor (30A) in one mode (normal operation/mode), and block the engine core flow into the power turbine section and divert the flow through a bypass path (222) in a second mode (bypass operation/mode). In the bypass mode, the power turbine (38) is undriven which effectively prevents or substantially reduces rotation of the propulsor rotor (30A). This reduces or eliminates safety risks to ground crews resulting from an open propulsor rotor (30A) actively rotating as the aircraft is on the ground.