Multi-valve Steam Valve Segmentation for Low-speed Control
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Solution Overview
Problem
The multi-valve-type steam valve used in steam turbines experiences difficulty in controllability during low-speed rotation due to a wide flow rate range, particularly during warm-up operations, where the rotor's distortion needs correction.
Innovation Solution
The steam valve is designed with control valves that have a smaller steam inflow amount when opening, featuring a smaller valve body and a pilot valve system to narrow the flow rate range, allowing for precise control and reduced driving force requirements, facilitating operation at low rotation speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the control valve is designed with a wide flow rate range, then the valve can handle larger steam flow, but controllability during low-speed rotation deteriorates
Solution Approach 1:
The steam valve system is segmented into multiple control valves (first control valve and second control valve) that operate in sequence. The first control valve handles lower flow rates during warm-up and fine speed adjustment, while the second control valve handles higher flow rates during full power operation. This segmentation allows each valve to be optimized for its specific operating range, improving overall controllability.
Solution Approach 2:
The valve lift amounts are dynamically adjusted based on operating conditions. During warm-up and low-speed rotation, the first control valve is opened with a smaller lift amount to provide fine control. During full power operation, the second control valve is opened with a larger lift amount to handle high steam flow. This dynamic adjustment of valve lift optimizes controllability across different operating ranges.
2Force
If the valve body size is reduced to decrease steam inflow amount, then driving force requirements are reduced, but the valve may become insufficient for high flow rate applications
Solution Approach 1:
The system uses two control valves with different valve body sizes segmented into different operational roles. The first control valve has a smaller valve body suitable for low flow rate applications during warm-up, requiring less driving force. The second control valve has a larger valve body capable of handling high flow rates during full power operation. This segmentation allows each valve to be appropriately sized for its specific function.
Solution Approach 2:
Different parts of the valve system have different sizes and characteristics tailored to their specific functions. The first control valve is designed with a smaller valve body and smaller valve lift amount for fine control during warm-up, while the second control valve is designed with a larger valve body for high flow capacity. This local differentiation of valve characteristics optimizes both controllability and flow capacity.
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 configuration improves controllability during fine speed adjustments by reducing the steam flow rate range, enabling effective steam guiding and power reduction, thus enhancing the turbine's operational efficiency during warm-up and low-speed operations.
Implementation Method 1
the pilot valve may block the steam guide hole and the steam discharge hole in the closed state, the upstream-side flow path and the downstream side may communicate with each other via the space by driving the valve shaft in the one direction from the closed state to cause the steam guide hole and the steam discharge hole to be released
Data Source
AI summary
A multi-valve-type steam valve provided with a plurality of control valves widening a flow path as valve bodies are gradually separated from valve seats by valve shafts being driven in one direction and allowing steam to flow in by allowing the plurality of control valves to reach an open state in order, the multi-valve-type steam valve being configured such that at least the control valve reaching the open state first among the plurality of control valves have a smaller steam inflow amount during the driving in the one direction from a closed state than the other control valves.