Gas Turbine Blade Labyrinth Cooling Channel Geometry
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Solution Overview
Problem
In gas turbine engines, the thermal shielding of the bucket groove area and internal cooling flows within turbine blades face challenges where increased cooling flow in some channels reduces cooling flow to other channels, affecting the overall efficiency and mechanical strength of the blades and rotor disc.
Innovation Solution
A turbine blade design featuring a labyrinth of internal channels with a unique geometry, including an inlet duct with varying cross sections, a leading edge passage, a multi-pass main blade passage, and a restrictor passage, optimized for coolant distribution to ensure predominant flow to the leading edge and efficient cooling throughout the blade body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling passages are provided in the turbine blade to cool the blade body, then the blade can withstand higher operating temperatures, but the mechanical strength of the blade is reduced due to material behavior changes at elevated temperatures
Solution Approach 1:
The cooling system is segmented into multiple independent passages: leading edge passage for cooling the leading edge, multi-pass passage for cooling the blade body, and platform passage for cooling the platform area. This segmentation allows each region to be cooled independently, maintaining blade strength while withstanding high operating temperatures.
Solution Approach 2:
The cooling passages are nested within the blade structure, with the leading edge passage positioned radially outwardly of the multi-pass passage, and the platform passage positioned axially downstream. This nested arrangement allows multiple cooling functions to be integrated within the limited blade volume, providing comprehensive cooling while preserving structural integrity.
2Temperature
If cooling air is delivered to the turbine blade through a port adjacent the rim of the turbine disc, then the blade surfaces are protected from excessive heat, but increasing cooling flow in some internal channels reduces cooling flow to other channels
Solution Approach 1:
The cooling system provides locally optimized cooling flow distribution: the leading edge passage receives cooling air directed radially outwardly to cool the leading edge region, the multi-pass passage receives cooling air for the blade body, and the platform passage receives cooling air for the platform area. This local quality approach ensures each region receives appropriate cooling flow without compromising other areas.
Solution Approach 2:
The cooling passages incorporate dynamic flow control features: the leading edge passage has its proximal end angled towards the direction of incoming air flow to optimize flow distribution, and the passages are designed to adaptively distribute cooling flow based on operational conditions, ensuring balanced cooling across all blade regions.
3Temperature
If a duct is provided integral to the blade with an inlet at the upstream face of the terminal portion, then thermal shielding of the bucket groove area is improved, but coolant stagnation occurs in downstream ducts
Solution Approach 1:
The upstream duct portion is positioned to receive cooling air at the upstream face of the terminal portion before the coolant enters downstream regions. This preliminary action ensures thermal shielding of the bucket groove area is established early in the flow path, preventing heat accumulation before coolant can stagnate in downstream ducts.
Solution Approach 2:
The duct system incorporates dynamic flow management through the mid-blade duct portion positioned in axial alignment and the restrictor passage that actively controls coolant flow distribution. This dynamic design prevents stagnation by maintaining continuous flow movement through all duct sections while providing effective thermal shielding.
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 design enhances thermal shielding and cooling efficiency by directing coolant flow effectively to critical areas, reducing stress concentrations and improving turbine efficiency while minimizing coolant stagnation in downstream ducts.
Implementation Method 1
a turbine blade having a body enclosing a labyrinth of internal channels for the circulation of coolant
Implementation Method 2
enhances thermal shielding and cooling efficiency by directing coolant flow effectively to critical areas
Data Source
AI summary
A turbine blade having a labyrinth of internal channels for circulation of coolant received through an inlet formed in a terminal portion of a blade root. A labyrinth geometry includes: (i) the inlet arranged on an axially upstream face of the terminal portion leading to an upstream duct portion having a first section adjacent the inlet and a second section having a reduced cross-section compared to the first section, (ii) a leading edge passage intersecting with the first section and extending through a blade body towards a tip of the blade, where a proximal end of the leading edge passage is angled towards a direction of incoming air flow, (iii) a main blade passage intersecting with a downstream duct portion arranged in axial alignment with, and separate from, the upstream duct portion, and (iv) a restrictor passage intersecting with a mid-blade passage and extending towards a mid-blade duct portion.