Thrust Reverser Actuator Flow Limiter
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Solution Overview
Problem
Conventional thrust reverser actuation systems place a high hydraulic flow demand on aircraft, exceeding the capacity of onboard hydraulic pumps, particularly in new aircraft designs, which can lead to reduced force authority and deploy time performance.
Innovation Solution
A fluid control system that includes a directional control valve, bypass fluid lines, and a flow limiter to regulate and limit the pressure draw of the hydraulic actuator, supplementing fluid flow from a pressurized source with return reservoir pressure when an aiding load is present, thereby reducing the overall flow demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional thrust reverser actuation systems are used, then the thrust reverser can be deployed, but the hydraulic flow demand exceeds the capacity of onboard hydraulic pumps
Solution Approach 1:
The system changes the pressure parameter by allowing the actuator pressure to exceed normal system limits (up to 3000 psi) during deployment. The flow limiter device controls the rate of pressure increase, allowing high pressure to be achieved without requiring proportionally high flow rates, thus resolving the contradiction between flow demand and pump capacity
Solution Approach 2:
The flow limiter device acts as an intermediary between the hydraulic pump and the actuator. It mediates the pressure and flow relationship by limiting the maximum flow rate while allowing pressure to build up to the level needed for deployment, enabling the system to overcome the pump's flow capacity limitation
2Quantity of substance
If pump size is increased to meet flow demand, then hydraulic flow capacity is sufficient, but weight, cost, and complexity increase
Solution Approach 1:
Instead of increasing pump size (which would increase weight), the system changes the pressure parameter by allowing transient over-pressure conditions. The flow limiter enables the actuator to reach high pressures (3000 psi) with a smaller pump by controlling the pressure build-up rate rather than requiring high continuous flow capacity
3Quantity of substance
If regenerative-type directional control valves are used, then flow demand is reduced, but flow demand still exceeds pump capacity in certain aircraft designs
Solution Approach 1:
The flow limiter device serves as an intermediary that works in conjunction with regenerative valves. It mediates the pressure-flow relationship by allowing pressure to exceed normal limits while controlling the rate of pressure increase, enabling deployment capability even when regenerative valves alone are insufficient to reduce flow demand below pump capacity
Solution Approach 2:
The system changes the pressure parameter to allow transient over-pressure conditions during deployment. This works complementarily with regenerative valves by allowing the pressure to build up to levels sufficient for deployment even when the regenerative valve alone cannot reduce flow demand enough
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
This solution effectively limits the hydraulic flow demand, meeting deploy timing requirements without exceeding system pressure limits, thus maintaining performance while reducing the need for pump size increases, which would add weight, cost, and complexity.
Implementation Method 1
a flow limiter residing between the pressurized fluid source and the directional control valve, the flow limiter configured to inhibit a pressure draw by the actuator from surpassing a predetermined threshold
Implementation Method 2
a directional control valve operable to selectively route fluid between a pressurized fluid source, the actuator, and a fluid return reservoir
Implementation Method 3
one or more bypass fluid lines providing fluid communication between the actuator and the fluid return reservoir independent of the directional control valve
Data Source
AI summary
An engine assembly includes a nacelle configured to at least partially surround an engine and a thrust reverser coupled to the nacelle. The thrust reverser includes: a thrust-reversing element movable relative to the nacelle between a stowed position and a deployed position; a hydraulic actuator operably coupled to move the thrust-reversing element; and a fluid control system configured to operate the hydraulic actuator. The fluid control system includes: a directional control unit including a directional control valve operable to selectively route fluid between a pressurized fluid source, the actuator, and a fluid return reservoir; one or more bypass fluid lines providing fluid communication between the actuator and the fluid return reservoir independent of the directional control valve; and a flow limiter residing between the pressurized fluid source and the directional control valve, the flow limiter configured to inhibit a pressure draw by the actuator from surpassing a predetermined threshold.