Electrohydrostatic Shut-Off Circuit Using Pilot Logic Valve
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Solution Overview
Problem
In electrohydrostatic actuation systems for steam turbines, achieving stable emergency shut-off with a simple configuration while protecting hydraulic pumps from overload and hydraulic fluid reflux, and maintaining hydraulic fluid performance is challenging due to viscosity degradation and efficiency issues.
Innovation Solution
An electrohydrostatic actuation system incorporating a hydraulic cylinder with a piston biased by a return spring, a shuttle valve to maintain hydraulic pressure, a solenoid valve for pilot pressure, and a logic valve that allows hydraulic fluid to flow from the first chamber to the second chamber when the solenoid is de-energized, enabling quick emergency shut-off and preventing hydraulic fluid reflux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a solenoid valve is used to achieve emergency shut-off in an electrohydrostatic actuation system, then the valve can be quickly closed, but the configuration becomes complex and stability is compromised
Solution Approach 1:
The patent combines the emergency shut-off function with the normal control function by using the same solenoid valve and logic valve for both purposes. The solenoid valve serves dual roles: controlling normal valve operation and triggering emergency shut-off when de-energized, thereby simplifying the overall circuit configuration while maintaining fast response capability
Solution Approach 2:
The logic valve is designed to perform multiple functions: it controls hydraulic fluid flow during normal operation and automatically redirects flow for emergency shut-off when the solenoid valve de-energizes. This multi-functionality eliminates the need for separate emergency shut-off components, reducing system complexity
2Productivity
If the hydraulic pump operates beyond rated output due to overload, then the valve can be actuated, but the servo motor becomes overheated
Solution Approach 1:
The patent employs a variable displacement hydraulic pump that dynamically adjusts its displacement based on system pressure feedback. When the steam turbine valve encounters high resistance or overload conditions, the pump automatically reduces its displacement to prevent excessive motor loading and overheating, while still maintaining sufficient flow to complete the actuation
Solution Approach 2:
A pressure feedback mechanism monitors the hydraulic system pressure and provides signals to adjust the pump displacement accordingly. This feedback control ensures the pump operates within safe parameters, preventing servo motor overheating while maintaining the ability to actuate the valve under various load conditions
3Device complexity
If the hydraulic fluid is sealed in a completely closed system, then the system is compact, but the hydraulic fluid temperature rises and viscosity deteriorates
Solution Approach 1:
The patent incorporates a pre-heating circuit that circulates hydraulic fluid through the pump before main operation begins. This preliminary action warms the fluid to its optimal operating temperature range, preventing viscosity deterioration during subsequent operations and eliminating the need for complex temperature control systems
Solution Approach 2:
The hydraulic system maintains continuous circulation of fluid through the pump and circuit, even during idle periods. This continuous motion prevents fluid stagnation and temperature stratification, maintaining uniform temperature distribution and preventing localized overheating that would lead to viscosity deterioration
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 system achieves stable emergency shut-off with a simple configuration, protects hydraulic pumps during fail-safe operations, and maintains hydraulic fluid performance by preventing viscosity degradation and efficiency loss.
Implementation Method 1
a solenoid valve configured to receive the hydraulic pressure via the shuttle valve as a pilot pressure; and a logic valve including a first port configured to receive the pilot pressure from the solenoid valve
Implementation Method 2
a hydraulic pump configured to supply hydraulic fluid to the first chamber or the second chamber
Implementation Method 3
a hydraulic cylinder including a piston to which a valve element biased by a return spring is connected
Data Source
AI summary
Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).