Steam Turbine Rotor Thrust Control via Dynamic Extraction Balancing
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Solution Overview
Problem
Existing steam turbines face challenges in dynamically balancing rotor thrust during transient operations, leading to potential damage to thrust bearings and reduced efficiency, especially when overload valves are fully open or pre-heaters are in an off state, resulting in significant increases in rotor thrust beyond 200kN.
Innovation Solution
A steam turbine system with a thrust control system that includes an electronic controller communicating with control valves and pre-heaters, dynamically adjusting steam extraction flows to maintain net thrust within a desired range by selectively controlling the positions of control valves and overload valves, thereby preventing thrust bearing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high thrust load bearing or larger bearing area is used to handle transient thrust increases, then the thrust bearing can withstand higher loads, but the cost increases and leakage from the thrust piston increases decreasing efficiency
Solution Approach 1:
The patent applies dynamics by making the thrust bearing load capacity adaptable through real-time control of extraction steam flow. The control system dynamically adjusts the extraction valve position based on measured thrust levels, allowing the thrust bearing to handle transient high loads without requiring a permanently oversized bearing design. This resolves the contradiction by providing high load capacity only when needed rather than continuously.
Solution Approach 2:
The patent changes the operational parameters of the extraction steam flow to control thrust levels. By adjusting the extraction valve opening degree and controlling the amount of steam extracted, the system modulates the thrust force acting on the rotor, thereby protecting the thrust bearing during transient operations without requiring a larger bearing area that would increase leakage.
2Reliability
If a larger bearing area is used to balance transient thrust, then the thrust bearing can handle higher loads, but leakage from the thrust piston increases reducing steam turbine efficiency
Solution Approach 1:
The system dynamically adjusts extraction steam flow in real-time based on thrust measurements, allowing the thrust bearing to be protected during transient operations without requiring a permanently larger bearing area. This dynamic control maintains high efficiency by avoiding the continuous leakage that would result from a larger static bearing design.
Solution Approach 2:
The patent implements a feedback control system where thrust levels are continuously measured and used to adjust the extraction valve position. This closed-loop control ensures the thrust bearing is protected during transient operations while maintaining optimal extraction flow settings that minimize efficiency losses, resolving the contradiction between reliability and productivity.
3Reliability
If extraction steam flow is increased to control thrust during transient operations, then thrust bearing protection is improved, but steam turbine efficiency decreases due to reduced extraction flow
Solution Approach 1:
The system dynamically balances thrust control and extraction flow needs by continuously adjusting the extraction valve position based on real-time thrust measurements. During transient operations, the system temporarily increases extraction flow to protect the thrust bearing, then returns to optimal extraction settings when thrust levels normalize, thus protecting the bearing while minimizing impact on energy utilization.
Solution Approach 2:
The control system applies periodic adjustment of extraction flow in response to transient thrust events. When thrust exceeds thresholds during transient operations, the system temporarily modifies extraction flow to protect the bearing, then restores normal extraction flow once the transient condition passes, minimizing the overall impact on steam turbine efficiency and energy use.
Data Source
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AI summary
The present application provides a steam turbine system. The steam turbine system may include a rotor, a high pressure section positioned about the rotor, one or more high pressure extraction conduits extending from the high pressure section, a high pressure control valve positioned on each of the high pressure extraction conduits, an intermediate pressure section positioned about the rotor, one or more intermediate pressure extraction conduits extending from the intermediate pressure section, an intermediate pressure control valve positioned on each of the intermediate pressure extraction conduits, and a controller in communication with the high pressure control valves and the intermediate pressure control valves and operable to selectively adjust respective positions of the high pressure control valves and the intermediate pressure control valves to balance thrust acting on the rotor.