Variable Fan Nozzle Shape Memory Alloy Actuation
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Solution Overview
Problem
Conventional gas turbine engines operate inefficiently and experience mechanical stress during take-off and landing due to pressure pulsations across the fan, leading to increased fuel consumption and reduced life expectancy, as they are designed for specific cruise conditions and not adaptable to a wider range of flight conditions.
Innovation Solution
A variable fan nozzle using thermally active shape memory material with axially or radially movable tabs, controlled by a controller to change the effective area and manage bypass airflow, thereby maintaining optimal fan operation across varying flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan and bypass airflow ratio are designed for cruise conditions, then desired pressure ratio is maintained during cruise, but pressure pulsations occur during take-off and landing
Solution Approach 1:
The nozzle is designed with movable tabs that can dynamically adjust the bypass airflow area based on flight conditions. The tabs are actuated by shape memory alloy actuators that change the nozzle geometry from a fixed configuration to a variable configuration, allowing the system to adapt to different operating regimes (cruise, take-off, landing) and maintain optimal pressure ratios across all conditions
Solution Approach 2:
The invention changes the physical parameter of the nozzle area by moving the tabs axially or radially. This parameter change allows the bypass airflow area to be adjusted, thereby controlling the pressure ratio across the fan for different flight conditions. The shape memory alloy actuators enable reversible transitions between different nozzle area configurations through thermal activation
2Device complexity
If conventional fixed nozzle design is used, then engine structure is simple, but fan experiences mechanical stress and reduced life expectancy during take-off and landing
Solution Approach 1:
The nozzle is segmented into multiple movable tabs rather than being a single fixed structure. Each tab can be independently actuated by shape memory alloy actuators, allowing distributed control of the bypass airflow. This segmentation enables the complex function of variable geometry while distributing mechanical stresses across multiple smaller components
Solution Approach 2:
The invention replaces traditional mechanical actuation systems with shape memory alloy actuators that use thermal activation to produce mechanical motion. This substitution reduces the complexity of mechanical linkages, gears, and motors while achieving the same function of tab movement. The SMA actuators directly convert thermal energy to mechanical displacement, simplifying the overall actuation system
3Productivity
If bypass airflow is not controlled during take-off and landing, then engine operation is simple, but fuel consumption increases due to inefficient fan operation
Solution Approach 1:
The system incorporates sensors that detect flight conditions (such as altitude, speed, and pressure) and feed this information to a controller. The controller then actuates the nozzle tabs through shape memory alloy actuators to optimize the bypass airflow area, maintaining efficient fan operation across different flight regimes. This closed-loop feedback control ensures the engine operates at peak efficiency during take-off and landing, reducing fuel consumption
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 solution enhances engine efficiency and reduces mechanical stress by controlling bypass airflow, maintaining desired pressure ratios and noise levels, and extending the life expectancy of the fan by adapting to different flight conditions.
Implementation Method 1
The nozzle includes a shape memory material having a first solid state phase that corresponds to a first nozzle position and a second solid state phase that corresponds to a second nozzle position. The shape memory material is thermally active.
Implementation Method 2
The controller controls an actuator near the nozzle selectively heats and cools the nozzle to reversibly transition the shape memory material between the phases to move the nozzle between the positions.
Data Source
AI summary
A gas turbine engine includes a fan, a nacelle arranged about the fan, and an engine core at least partially within the nacelle. A fan bypass passage downstream of the fan between the nacelle and the gas turbine engine conveys a bypass airflow from the fan. A nozzle associated with the fan bypass passage is operative to control the bypass airflow. The nozzle includes a shape memory material having a first solid state phase that corresponds to a first nozzle position and a second solid state phase that corresponds to a second nozzle position.