Single-flow Turbine Dummy Ring Cooling via Pressure Gradient
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Solution Overview
Problem
Current cooling methods for the dummy ring and rotor in single-flow turbines are inadequate, leading to temperature-related strength issues and reduced thermal efficiency, as they fail to effectively cool these components and result in the wastage of high-temperature steam.
Innovation Solution
A cooling method that supplies cooling steam with lower temperature and higher pressure than the leak steam to the clearance between the dummy ring and the rotor, preventing the leak steam from entering and improving the cooling effect, while also allowing for the recovery of cooling steam for subsequent turbine stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-chrome steel is used for turbine rotor parts to withstand 600°C steam, then the rotor can tolerate the steam temperature, but the strength is insufficient when steam temperature is raised to 700-750°C
Solution Approach 1:
The turbine rotor is divided into multiple parts with different material properties. High-temperature resistant parts (nozzle chamber, first stage blades) are made of Ni base alloy, while other parts are made of CrMoV steel. This segmentation allows each part to be optimized for its specific thermal environment, enabling the use of higher steam temperatures while maintaining overall rotor strength.
Solution Approach 2:
Different material qualities are applied to different locations of the rotor based on local temperature requirements. The high-temperature zone near the nozzle chamber uses Ni base alloy for superior heat resistance, while lower-temperature zones use CrMoV steel. This local quality differentiation resolves the strength limitation when using high-temperature steam.
2Strength
If Ni base alloy is used for the entire turbine rotor to withstand 700-750°C steam, then the rotor strength is sufficient, but the production cost increases and large-scale production becomes difficult
Solution Approach 1:
The rotor is segmented into high-temperature zones requiring Ni base alloy and lower-temperature zones where CrMoV steel suffices. This reduces the total amount of expensive Ni base alloy needed, making large-scale production more feasible while maintaining sufficient strength for 700-750°C steam operation.
Solution Approach 2:
Ni base alloy is applied locally only where high-temperature resistance is critical (nozzle chamber, first stage blades), rather than throughout the entire rotor. This localized application reduces material costs and manufacturing complexity while maintaining the necessary strength for high-temperature steam.
3Temperature
If cooling steam is supplied to the dummy ring and rotor clearance, then the temperature rise is prevented, but the cooling steam may interfere with the main steam flow
Solution Approach 1:
The cooling steam supply and discharge paths are extracted and positioned separately from the main steam flow path. Cooling steam is supplied through paths formed in the dummy ring and discharged through paths closer to the nozzle chamber, ensuring that cooling steam does not interfere with the main steam injection and flow to the blade cascade.
Solution Approach 2:
The dummy ring acts as an intermediary structure that separates the cooling steam flow from the main steam flow. By forming cooling steam supply and discharge paths within the dummy ring, the patent enables independent cooling steam circulation without disrupting the main steam's path to the turbine blades.
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 method effectively prevents temperature rise in the dummy ring and rotor, reduces the need for specialized maintenance, and allows for the use of less expensive materials, enhancing the durability and thermal efficiency of the turbine components.
Implementation Method 1
supplying cooling steam generated in a steam turbine power plant to a cooling steam supply path arranged in a dummy ring, the cooling steam having lower temperature and higher pressure than leak steam which is a portion of main steam supplied to a single-flow turbine and leaks to a dummy ring side
Implementation Method 2
cooling the dummy ring and the rotor by introducing the cooling steam to a clearance formed between the dummy ring and the rotor via the cooling steam supply path and feeding the cooling steam in the clearance
Data Source
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AI summary
It is intended to effectively cool a dummy ring and a rotor disposed on the inner side of the dummy ring of a single-flow turbine and to suppress a decrease in thermal efficiency by preventing main steam from leaking to the dummy ring side. A cooling steam supply pipe 32 is provided in the dummy ring 26 of the single-flow turbine 10A and extraction steam of a boiler at 570°C or below is supplied to a clearance c between the dummy ring 26 and the turbine rotor 12 as cooling steam S4. The cooling steam S4 has lower temperature and higher pressure than leak steam S2 which is a portion of the main steam S1 leaking to the dummy ring 26 side. By supplying the cooling steam S4, the leak steam S2 is prevented from entering the dummy ring 26 side and the dummy ring 26, a welding part w and a second rotor part 12b with low heat resistance that are disposed on the inner side of the dummy ring 26 can be cooled.