Hydraulic Actuator End-Stop Valve for Parasitic Flow Control
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Solution Overview
Problem
Aircraft hydraulic actuator systems face challenges in efficiently managing parasitic flow, particularly during engine start conditions where reduced flow is necessary to optimize system sizing, and existing systems lack effective mechanisms to control fluid flow for secondary functions like cooling without increasing component complexity.
Innovation Solution
The proposed actuator system incorporates a hydraulic actuator with a primary piston and a secondary piston-based actuator valve that transitions between open and closed flow states, controlled by a biasing element and an electrohydraulic servo valve, allowing for adjustable pressure distribution between retract and extend chambers to manage fluid flow and enable secondary functions like piston cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic actuators are used to actuate engine components, then primary actuation function is provided, but parasitic flow increases system complexity and reduces efficiency
Solution Approach 1:
The patent combines the primary actuation function and secondary cooling function into a single hydraulic actuator system. The actuator includes both a primary piston for actuation and a secondary piston for controlling cooling fluid flow, allowing both functions to share the same hydraulic fluid and control mechanism, thereby eliminating the need for separate cooling pumps and reducing parasitic flow.
Solution Approach 2:
The hydraulic actuator is designed to perform multiple functions: primary actuation of engine components and secondary control of cooling fluid flow to pistons. The single actuator system can selectively direct hydraulic fluid to either the retract chamber or extend chamber, and simultaneously control cooling flow through the secondary piston, providing multi-functionality without increasing system complexity.
2Reliability
If separate cooling systems are added to hydraulic actuators, then piston cooling is enabled, but device complexity increases
Solution Approach 1:
The cooling system is merged with the primary hydraulic actuation system by using the same hydraulic fluid and actuator structure. The secondary piston shares the hydraulic connection with the primary piston, and both control functions are integrated within the same actuator housing, eliminating the need for separate cooling pumps and reservoirs.
Solution Approach 2:
The single hydraulic actuator is designed to perform both actuation and cooling control functions. By controlling the position of the secondary piston, the system can selectively enable or disable cooling flow to the pistons, providing a universal system that handles both primary actuation and thermal management without requiring additional dedicated components.
3Productivity
If parasitic flow is reduced during engine start, then system sizing is optimized, but flow control capability is limited
Solution Approach 1:
The hydraulic actuator incorporates adjustable pressure distribution between the retract chamber and extend chamber through the secondary piston mechanism. This allows the system to dynamically adapt flow control based on operational requirements, enabling reduced parasitic flow during engine start while maintaining full flow control capability when needed for piston cooling during high-power operations.
Solution Approach 2:
The system enables parameter changes in hydraulic fluid flow by adjusting the position of the secondary piston, which controls the pressure distribution and flow paths. This allows the system to optimize flow parameters for different operational phases, reducing parasitic flow during low-power conditions while enabling full cooling flow during high-temperature conditions.
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 reduces parasitic flow during low pump capabilities and optimizes system design by providing controlled cooling flows, enhancing system efficiency and reducing component complexity, especially during critical conditions like engine start and maximum takeoff power.
Implementation Method 1
The actuator valve includes a biasing element configured to bias the secondary piston into the open flow state
Implementation Method 2
when the primary piston is in a fully retracted state the piston head urges the secondary piston into a closed flow state
Implementation Method 3
A control element is configured to control a supply of pressure to each of the retract chamber and the extend chamber
Data Source
AI summary
Actuator systems and methods of operation are disclosed. The systems include a hydraulic actuator having a primary piston having a piston head arranged within a housing defining retract and extend chambers on opposite sides of the piston head. A control element is configured to control a supply of pressure to each of the retract and extend chambers. An actuator valve is coupled to the housing and includes a secondary piston that is biased into the retract chamber in an open flow state and when the primary piston is in a fully retracted state the piston head urges the secondary piston into a closed flow state. The actuator valve defines a flow chamber where, in an open flow state, fluid can be passed through the flow chamber and in a closed flow state the fluid is prevented from passing through the flow chamber.