Rankine Cycle Expander Liquid Suction Prevention Control
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Solution Overview
Problem
Rankine cycle systems face reliability issues due to the suction of liquid working fluids into expanders, leading to lubrication oil discharge and potential wear or erosion, especially when using turbo-type expanders without lubrication oil.
Innovation Solution
A power generation control system that includes a converter and controller, which prevents the expander from expanding the working fluid if it contains a liquid component at the outlet of the evaporator during startup or shutdown operations, by restricting the operation of the generator or using it as a compressor to bypass expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump operates during startup or shutdown, then the working fluid is circulated through the evaporator, but liquid components may be present in the working fluid which can be sucked into the expander
Solution Approach 1:
The controller executes preliminary control actions during startup and shutdown to prevent liquid components from entering the expander. Specifically, the controller restricts expander operation or operates it in a bypass mode before the working fluid is fully vaporized, thereby preventing liquid suction in advance and protecting the expander from damage
Solution Approach 2:
The controller acts as an intermediary between the pump and the expander, managing the transition of working fluid state. It coordinates the operation timing to ensure that the expander only processes vapor-phase working fluid, using control signals to synchronize pump operation with evaporator output quality
2Power
If the expander operates with liquid working fluid, then power generation can occur, but lubrication oil is discharged and wear or erosion occurs
Solution Approach 1:
The controller monitors the operational state of the Rankine cycle system and adjusts expander operation accordingly. During startup and shutdown phases, the controller detects conditions that may lead to liquid presence and provides feedback control to restrict or bypass expander operation, preventing liquid-induced wear while maintaining power generation during safe operating conditions
Solution Approach 2:
The system dynamically adjusts expander operation mode based on real-time conditions. The controller switches between normal expansion mode and bypass/restriction mode depending on the operational phase and working fluid state, optimizing both power generation and component protection through dynamic control
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 approach reduces the likelihood of liquid working fluids being sucked into the expander, thereby enhancing the reliability of the Rankine cycle system by minimizing wear and loss, and allowing smoother rotational speed adjustments and power generation.
Implementation Method 1
The evaporator heats the working fluid. With this operation, the working fluid is transformed into a superheated vapor.
Implementation Method 2
The working fluid then expands adiabatically in the expander. Then, a driving force is generated in the expander so as to operate the expander.
Implementation Method 3
The expander and the generator convert thermal energy into electrical energy.
Implementation Method 4
The condenser cools an expanded working fluid by using, for example, cooling air, thereby condensing the working fluid.
Data Source
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AI summary
A power generation control system (100) includes a converter (120) and a controller (128). The converter (120) controls a generator (108) of a Rankine cycle system (101), the Rankine cycle system (101) including an expander (105), the generator (108), which is interconnected to the expander (105), a pump (107) which feeds a working fluid, and an evaporator (104) which evaporates a working fluid. The controller (128) causes the converter (120) to execute, in at least one of a startup operation and a shutdown operation of the Rankine cycle system (101), first control in at least one of a startup operation and a shutdown operation of the Rankine cycle system (101) such that the expander (105) is prevented from expanding a working fluid if the working fluid at an outlet of the evaporator (104) contains a liquid component while the pump (107) is operating.