Turbojet Nacelle Thrust Reverser Drive Mechanism
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Solution Overview
Problem
The deactivation time of thrust reversers in turbofan engines is not optimum due to the substantial power requirements of large-sized actuators needed to counteract aerodynamic pressures, which are not fully met by limited aircraft power sources.
Innovation Solution
A nacelle design with a drive mechanism that includes a flexible member, such as a spring, fixed between the nacelle structure and the movable cowl, which assists the actuator in opposing aerodynamic forces, allowing for the use of smaller-sized actuators with reduced power requirements, thereby shortening deactivation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large-sized actuators are used to counteract substantial aerodynamic pressures during thrust reverser deactivation, then sufficient tractive force is achieved, but the power requirements exceed the limited aircraft power availability
Solution Approach 1:
A flexible member (spring) is introduced as an intermediary element between the actuator and the movable cowl. This spring stores and releases elastic energy to assist the actuator during deactivation, reducing the peak power demand on the aircraft's limited power sources while maintaining sufficient tractive force to counteract aerodynamic pressures.
Solution Approach 2:
The system transitions from a static actuator design to a dynamic system incorporating a flexible spring element. The spring dynamically stores energy during activation and releases it during deactivation, allowing the actuator to operate within available power limits while achieving the required force output when needed.
2Force
If large-sized actuators are used to counteract substantial aerodynamic pressures, then sufficient tractive force is achieved, but the deactivation time is not optimum
Solution Approach 1:
The spring is pre-loaded during the activation phase, storing elastic energy in advance. During deactivation, this pre-stored energy is rapidly released to assist the actuator, enabling faster reversal without requiring larger actuators or excessive power input during the critical deactivation window.
3Power
If the actuator size is reduced to match available aircraft power, then power requirements are met, but the tractive force is insufficient to counteract aerodynamic pressures
Solution Approach 1:
The flexible spring acts as a force-multiplying intermediary that allows a smaller actuator to generate sufficient tractive force during deactivation by releasing stored elastic energy, thereby matching available aircraft power while maintaining the necessary force output.
4Power
If smaller actuators are used to match available aircraft power, then power requirements are met, but the deactivation time increases
Solution Approach 1:
Energy is pre-stored in the spring during activation, enabling the smaller actuator to rapidly deploy this stored energy during deactivation. This preliminary energy storage allows smaller actuators to achieve fast deactivation times without exceeding available power limits.
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 flexible member reduces the force required by the actuator to move the thrust reverser components, enabling faster deactivation times and optimizing actuator performance despite limited aircraft power, with demonstrated reductions in activation and deactivation times from 2.5 to 1.1 seconds and 7 to 2.4 seconds, respectively.
Implementation Method 1
a flexible member subjected to compressive or tensile stress arranged between the movable cowl and the fixed structure of the nacelle
Data Source
AI summary
A nacelle includes a fixed structure supporting a fixed cowl and a movable cowl, the movable cowl being movable translationally between a closing position and an opening position. A blocker door is movably mounted rotationally on the nacelle between a closed position and an open position. The nacelle includes a drive mechanism of the blocker door and of the movable cowl between the closed/closing position and the open/opening position of the blocker door/movable cowl, respectively, and vice versa, the drive mechanism includes at least one actuator fixed, to the fixed structure of the nacelle and, to a fitting fixed to the movable cowl. The drive mechanism includes, for each actuator, a flexible member having a first end fixed to the fixed structure of the nacelle and a second end fixed to the fitting.