Turbine Blade Tip Rail Cooling Insert Design
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Solution Overview
Problem
Conventional turbine blade tip cooling systems face challenges in effectively reducing leakage and providing efficient cooling to the tip rail, which is subjected to high heat loads, and are difficult to manufacture using additive manufacturing due to issues with coolant flow and dust clogging, especially in areas with different temperature zones.
Innovation Solution
A turbine blade tip cooling system that includes a tip rail with internal cooling cavities and a tip rail cooling insert having insert cooling channels and a coolant collection plenum, allowing for selective cooling and addressing dust clogging, compatible with additive manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tip rail cooling passages are designed to deliver coolant through the top of the rail, then cooling effectiveness is improved, but backflow pressure margin requirements become difficult to satisfy and coolant flow losses increase
Solution Approach 1:
The cooling system is divided into multiple independent cooling channels (first cooling channel, second cooling channel, third cooling channel) that deliver coolant to different locations on the tip rail. This segmentation allows optimized coolant delivery to high-heat-load areas without requiring excessive backpressure, reducing overall coolant flow losses while maintaining cooling effectiveness.
Solution Approach 2:
Coolant is delivered to specific localized areas of the tip rail where heat loads are highest, rather than attempting to cool the entire rail uniformly. The multiple cooling channels target specific regions (leading edge, trailing edge, and intermediate areas) with coolant flow, optimizing cooling effectiveness while minimizing the total coolant flow required and reducing energy losses.
2Temperature
If outlet holes are made larger to provide sufficient cooling and dust tolerance, then cooling effectiveness and dust resistance are improved, but rub tolerance decreases
Solution Approach 1:
The cooling function is distributed across multiple smaller cooling channels rather than relying on a single large outlet hole. Each channel has its own outlet aperture, providing sufficient total cooling area while maintaining smaller individual aperture sizes that can better tolerate contact with the shroud during tip rub events.
Solution Approach 2:
Different regions of the tip rail are cooled through localized channels with outlet holes sized appropriately for their specific cooling requirements and rub exposure. This allows optimization of each channel's outlet hole size based on local conditions, balancing cooling effectiveness with rub tolerance.
3Ease of manufacture
If conventional circular cooling holes are used in tip rail, then manufacturing by additive manufacturing is simplified, but cooling effectiveness is reduced and holes are prone to deformation
Solution Approach 1:
The cooling channels utilize curved and rounded geometries that are well-suited for additive manufacturing processes, avoiding sharp corners and complex intersections that would deform during manufacturing. The channels feature smooth transitions and curved paths that maintain structural integrity while effectively delivering coolant to the tip rail.
Solution Approach 2:
The cooling channel geometry is optimized with specific dimensional parameters (channel diameters, wall thicknesses, curvature radii) that balance cooling effectiveness with manufacturability. These parameters are selected to ensure adequate coolant flow and heat transfer while maintaining geometric features that can be reliably produced using additive manufacturing without deformation.
4Loss of energy
If tip clearance is minimized to prevent leakage, then turbine efficiency is improved, but thermal and mechanical expansion differences cause excessive tip rub
Solution Approach 1:
The tip rail is divided into multiple sections with independent cooling channels, allowing differential thermal management of different rail segments. This enables the tip rail to accommodate thermal expansion more effectively while maintaining minimal clearance with the shroud, preventing excessive tip rub during operation.
Solution Approach 2:
The cooling system dynamically manages the thermal state of the tip rail through controlled coolant flow, adjusting the thermal expansion characteristics of the rail material. By maintaining optimal temperatures in different regions of the tip rail, the system prevents excessive expansion that would lead to tip rub while preserving minimal clearance for leakage prevention.
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 system provides improved cooling efficiency to the tip rail while reducing coolant flow requirements and accommodating varying temperatures, enhancing the durability and performance of turbine blades.
Implementation Method 1
a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the at least one insert cooling channel
Implementation Method 2
the rail of the squealer tip is subjected to a high heat load and is difficult to effectively cool... Tip rail impingement cooling delivers coolant through the top of the rail
Data Source
AI summary
A turbine blade tip cooling system includes a turbine blade having a tip cavity, a tip rail surrounding at least a portion of the tip cavity and at least one internal cooling cavity. The tip rail has an inner rail surface, an outer rail surface, an end surface and at least one tip rail pocket open at the end surface and fluidly connected to the at least one internal cooling cavity that carries a coolant. A tip rail cooling insert attaches to the at least one tip rail pocket, and has insert cooling channel(s) and a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the insert cooling channel(s).