Rotor Blade Tip Cooling via Segmented Pockets
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Solution Overview
Problem
The interaction between stationary shroud segments and rotor blade tip caps in turbines leads to elevated local temperatures, reducing low cycle fatigue limits and increasing creep, while excessive cooling media can disrupt fluid flow and reduce turbine efficiency.
Innovation Solution
A rotor blade design featuring a tip plate with a concave and convex portion, divided by dividers to create pockets, with cooling passages for efficient fluid communication, reducing temperature and oxidation, and minimizing cooling media loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling media is supplied to flow over the suction side of the rotor blade to cool the tip cap, then the temperature of the tip cap is reduced, but the flow of the compressed working fluid is disrupted and turbine efficiency is reduced
Solution Approach 1:
The suction side surface is segmented into multiple cooling zones with separate cooling passages, allowing independent control of cooling media flow in different regions. This enables cooling to be applied only where thermally critical while preserving working fluid flow in aerodynamically critical areas, thus resolving the contradiction between cooling effectiveness and turbine efficiency.
Solution Approach 2:
Different regions of the rotor blade receive different cooling treatments based on their specific thermal and aerodynamic requirements. The tip cap and adjacent regions receive cooling media flow, while regions critical for working fluid flow receive minimal or no cooling media injection. This localized differentiation allows simultaneous optimization of temperature control and turbine efficiency.
2Temperature
If excessive cooling media is supplied to the squealer tip cavity to cool the tip cap, then the temperature reduction is enhanced, but the cooling media loss increases and may disrupt working fluid flow
Solution Approach 1:
The cooling media flow rate is dynamically adjusted based on real-time temperature measurements and operational conditions. Variable geometry features such as adjustable flow restrictors or controllable passage openings allow the system to optimize cooling media consumption, providing sufficient cooling only when and where needed, thereby reducing cooling media loss while maintaining effective temperature control.
Solution Approach 2:
The cooling system incorporates feedback mechanisms that allow it to self-regulate cooling media flow based on thermal conditions. Temperature sensors monitor the tip cap temperature and automatically adjust cooling media supply through control valves or variable passage geometries, ensuring minimal cooling media consumption while maintaining adequate cooling performance.
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
The design effectively cools the rotor blade, reducing temperature and oxidation, improving aerodynamic performance and reducing repair costs while maintaining turbine efficiency by optimizing cooling media distribution and flow.
Implementation Method 1
a cooling media may be supplied to flow inside each rotor blade before flowing through cooling passages in the tip cap to provide film cooling over the tip cap of the rotor blade
Implementation Method 2
The rim and the tip plate may at least partially define a tip cavity, also known as a squealer tip cavity, between the rim, the tip plate, and the surrounding shroud segments. In this manner, the cooling media supplied to the squealer tip cavity may remove heat from the tip cap
Data Source
AI summary
A rotor blade includes an airfoil having a tip plate that extends across an outer radial end. A rim extends radially outward from the tip plate and surrounds at least a portion of the airfoil and includes a concave portion opposed to a convex portion. A plurality of dividers extend between the concave and convex portions to define a plurality of pockets between the concave and convex portions at the outer radial end. A plurality of cooling passages through the tip plate provide fluid communication through the tip plate to the plurality of pockets. A first fluid passage in at least one divider provides fluid communication between adjacent pockets across the at least one divider.