Expansion Device Over-rotation Prevention via Differential Pressure Limiting
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Solution Overview
Problem
Existing Rankine cycle systems fail to prevent over-rotation of the expansion device when the bypass valve becomes stuck in a closed state, leading to increased rotation speed and potential damage.
Innovation Solution
Implementing a transmission mechanism with an electromagnetic clutch and a bypass valve, where the expansion device clutch is maintained in the engaged state while performing front-rear differential pressure limiting processing to reduce the expansion device's pressure, thereby preventing over-rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bypass valve is switched from closed state to open state to stop the expansion device, then the expansion device can be stopped normally, but when the bypass valve becomes stuck in closed state, the front-rear differential pressure cannot be reduced and over-rotation occurs
Solution Approach 1:
A differential pressure limiting valve is introduced as an intermediary component to regulate the front-rear differential pressure across the expansion device. This valve acts as a backup mechanism that directly controls pressure when the bypass valve fails, preventing over-rotation by limiting the maximum pressure differential that can act on the expansion device.
Solution Approach 2:
The differential pressure limiting valve is pre-configured with a predetermined opening pressure that limits the front-rear differential pressure to a safe level. This beforehand cushioning ensures that even if the bypass valve fails, the pressure cannot exceed the predetermined limit, thus preventing over-rotation before it occurs.
2Ease of operation
If the electromagnetic clutch is disengaged before the bypass valve opens, then the expansion device is disconnected from the engine shaft, but the rotation speed increases rapidly causing over-rotation
Solution Approach 1:
The bypass valve is opened before disengaging the electromagnetic clutch to preliminarily reduce the front-rear differential pressure. This preliminary action ensures that the pressure differential is minimized before the expansion device is disconnected from the engine shaft, preventing rapid speed increase and over-rotation.
Solution Approach 2:
The differential pressure limiting valve serves as an intermediary safety mechanism that ensures the front-rear differential pressure remains below a predetermined level during the disconnection process, allowing the electromagnetic clutch to be disengaged safely without causing over-rotation.
3Reliability
If the bypass valve is opened first to reduce differential pressure, then over-rotation is prevented, but this sequence cannot be executed when the bypass valve is stuck closed
Solution Approach 1:
The differential pressure limiting valve is introduced as a backup intermediary mechanism that takes over pressure control functions when the bypass valve fails. This valve directly limits the front-rear differential pressure to a predetermined level, providing adaptability to bypass valve failure modes.
Solution Approach 2:
The system changes the control parameter from bypass valve position to differential pressure magnitude by introducing the differential pressure limiting valve. This parameter change allows the system to maintain safe operation by directly controlling the critical parameter (differential pressure) rather than relying solely on the bypass valve position.
4Object-affected harmful factors
If the electromagnetic clutch is kept engaged to maintain pressure control, then over-rotation is prevented, but the expansion device cannot be stopped
Solution Approach 1:
The differential pressure limiting valve acts as an intermediary safety mechanism that allows the electromagnetic clutch to be disengaged while maintaining safe operation. By limiting the front-rear differential pressure to a predetermined level, it enables the clutch to be disengaged without causing over-rotation, thus resolving the conflict between stopping the device and preventing over-rotation.
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 prevents over-rotation of the expansion device even when the bypass valve is stuck, ensuring safe operation and maintaining the system's efficiency by reducing the expansion device's pressure to a manageable level.
Implementation Method 1
an electromagnetic clutch that can be engaged and disengaged
Implementation Method 2
a passage through which refrigerant supplied to the expansion device
Implementation Method 3
Rankine cycle provided with
Data Source
AI summary
Apparatus for utilizing heat wasted from an engine includes: a Rankine cycle (31); a transmission mechanism that couples an output shaft of an expansion device (37) to a rotary shaft of an engine via an electromagnetic clutch (32) that can be engaged and disengaged; a passage (65) through which refrigerant exiting a heat exchanger (36) flows so as to bypass the expansion device (37); and a bypass valve (66) interposed in the passage. To stop the expansion device (37), the electromagnetic clutch (32) is switched from an engaged state to a disengaged state after switching the bypass valve (66) from a closed state to an open state. If the bypass valve (66) becomes stuck in the closed state, expansion device front-rear differential pressure limiting processing in which a front-rear differential pressure of the expansion device is limited while maintaining the electromagnetic clutch (32) in the engaged state is performed.