Fan Blade Pitch Change Mechanism for Oblique Airflow Load Balancing
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Solution Overview
Problem
The removal of the outer nacelle in turbofan engines leads to issues with misaligned airflow causing uneven loading on fan blades, resulting in undesirable forces and potential premature wear due to high cycle fatigue.
Innovation Solution
A pitch change mechanism that varies the pitch of individual fan blades based on their circumferential position using a non-uniform blade actuator system, which includes linkages and a master control to adjust the pitch of each blade independently, minimizing uneven loads by accommodating oblique airflow angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the outer nacelle is removed to reduce weight and size, then the weight and size of the engine are reduced, but the fan blades experience uneven loading and high cycle fatigue due to misaligned airflow
Solution Approach 1:
The patent implements a dynamic pitch change mechanism that allows fan blades to adjust their pitch angle in real-time based on airflow conditions. The mechanism includes a pitch control system with actuators that modify blade pitch dynamically, enabling the fan to adapt to oblique airflow angles without the outer nacelle, thereby preventing uneven loading and high cycle fatigue while maintaining weight reductions.
Solution Approach 2:
The patent changes the operational parameter of blade pitch angle to optimize performance under different airflow conditions. By varying the pitch angle of individual fan blades based on their position and local airflow characteristics, the system compensates for the absence of the outer nacelle's flow alignment benefits, reducing uneven loading and improving reliability without adding significant weight.
2Reliability
If individual blade pitch control is implemented to reduce uneven loading, then fan blade durability is improved, but the device complexity increases
Solution Approach 1:
The pitch control mechanism is segmented into modular units, with each fan blade having its own pitch control actuator and linkage system. This segmentation allows independent control of each blade while using standardized, interchangeable components. The modular design reduces overall system complexity by breaking down the complex function of individual blade control into manageable, repeatable units that can be manufactured and maintained more easily.
Data Source
AI summary
A gas turbine engine including: a turbomachine having a compressor section, a combustion section, and a turbine section arranged in serial flow order; a fan defining a fan axis and comprising a plurality of fan blades rotatable about the fan axis; and a pitch change mechanism operable with the plurality of fan blades, the pitch change mechanism including a plurality of linkages, the plurality of linkages including a first linkage coupled to a first fan blade of the plurality of fan blades and a second linkage coupled to a second fan blade of the plurality of fan blades; and a non-uniform blade actuator system operable with one or more of the plurality of linkages to control a pitch of the first fan blade relative to a pitch of the second fan blade.