Open Rotor Engine Excitation Load Control With Guide Vane Pitch
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Solution Overview
Problem
Open rotor aeronautical engines face challenges in accommodating off-axis airflow, leading to airfoil excitation phenomena that affect operational performance and structural requirements, including asymmetric loads and vibrations that impact propulsive efficiency and component longevity.
Innovation Solution
Implementing a control system with sensors and electronic controllers to determine airfoil excitation phenomena and adjust the pitch angles of fan blades and guide vanes, along with fuel flow and power output, to compensate for excitation loads and improve operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the outer nacelle is removed to facilitate a larger fan, then fan size and propulsive efficiency are improved, but off-axis airflow causes airfoil excitation and asymmetric loads that worsen structural reliability
Solution Approach 1:
The patent applies dynamics by making the airfoil geometry adaptive through real-time pitch angle adjustments. The controllable pitch mechanism allows the airfoil to dynamically change its angle of attack in response to detected excitation conditions, transforming a static structural problem into a dynamically controllable one. This enables the system to maintain optimal performance while actively mitigating harmful vibrations.
Solution Approach 2:
The patent changes physical parameters by adjusting the pitch angle of the airfoil based on detected excitation conditions. The control system modifies geometric parameters (pitch angle) in real-time to counteract asymmetric loads and vibrations, thereby resolving the contradiction between maintaining propulsive efficiency and ensuring structural reliability under off-axis airflow conditions.
2Reliability
If pitch angle adjustments are made to compensate for asymmetric loads, then structural reliability is improved, but device complexity increases due to additional control systems
Solution Approach 1:
The patent implements feedback control by using sensors to detect airfoil excitation and asymmetric loads, then feeding this information to a control system that adjusts the pitch angle in real-time. This closed-loop feedback mechanism automatically compensates for structural issues without requiring complex manual intervention, balancing reliability improvement with manageable system complexity.
Solution Approach 2:
The system applies self-service by enabling the airfoil to automatically detect and compensate for its own excitation problems. The integrated sensors and control mechanisms allow the structure to self-regulate its pitch angle in response to detected vibrations and asymmetric loads, reducing the need for external monitoring and complex control infrastructure.
Data Source
AI summary
An open rotor engine includes a core engine, a plurality of guide vanes positioned within or extending from the core engine; and a pitch change assembly operably coupled to the plurality of guide vanes. The pitch change assembly includes one or more actuators configured to change a pitch angle of respective ones of the plurality of guide vanes, and a plurality of linkage arms that are respectively movable by actuation of at least one of the one or more actuators. The plurality of linkage arms are directly or indirectly coupled to a corresponding one of the plurality of guide vanes. The plurality of linkage arms may have a length that differs from one another, and such length may orient a displacement or a range of motion of the respective linkage arm to an envelope of rotation about a guide vane axis that differs as between the plurality of guide vanes.