Small Turbine Stator Vane Impingement Cooling Insert
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Solution Overview
Problem
Small gas turbine engines face challenges in cooling due to the manufacturing of small features like cooling holes and thin wall thicknesses, which affect heat transfer efficiency and film coverage, making it difficult to cast stator vanes with cooling passages without compromising airfoil integrity.
Innovation Solution
A hollow airfoil stator vane with a metal additive manufacturing insert forming an impingement cooling circuit, using EDM to create thin walls and Direct Metal Laser Sintering for the insert, allowing for efficient cooling with radial tube-like channels and impingement cooling holes, and a design that secures the insert with a leading edge projection and aft end piece for thermal expansion and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling passages are added to small stator vanes, then cooling efficiency is improved, but manufacturing complexity increases and wall thickness becomes too thin to cast
Solution Approach 1:
The cooling system is segmented into multiple functional components: an insert with impingement cooling holes, radial tube-like channels for cooling air distribution, and film cooling holes. This segmentation allows each component to be optimized independently and assembled into the final cooling system, resolving the manufacturing complexity issue.
Solution Approach 2:
The insert containing the cooling circuit is nested within the hollow airfoil structure. The radial tube-like channels and impingement cooling holes are nested within the insert, which is then inserted into the hollow airfoil cavity. This nested arrangement enables complex cooling passages to be achieved without increasing overall wall thickness.
2Temperature
If cooling hole size is decreased, then film coverage is improved, but discharge coefficient decreases nonlinearly requiring increased pressure drop
Solution Approach 1:
The patent merges impingement cooling and film cooling into a single integrated system. The impingement cooling holes first cool the inner surface, and the same cooling air then provides film cooling at the outer surface. This merging allows small cooling holes to achieve adequate film coverage without requiring excessive pressure drop, as the impingement cooling pre-cools the air and surface.
3Shape
If trailing edge thickness is reduced, then aerodynamic performance is improved, but structural integrity and cooling hole formation become difficult
Solution Approach 1:
The cooling system transitions from traditional through-wall cooling holes to an impingement cooling approach where cooling air is directed at the inner surface of the trailing edge. This dimensional change allows cooling to be effective without requiring thick walls, as the cooling action occurs primarily on the inner surface where the insert is positioned.
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
Enables efficient cooling with a thinner trailing edge and reduced cooling air usage, achieving higher heat flux and improved engine efficiency with 40% to 50% less cooling air compared to traditional designs, while maintaining structural integrity and scalability for smaller engines.
Implementation Method 1
The insert includes radial tube-like channels to distribute the cooling air and impingement cooling holes as a single piece
Implementation Method 2
machined to form hollow airfoils using an EDM (Electric Discharge Machining) process to form thin airfoil walls that cannot be cast
Implementation Method 3
The insert in conjunction with the airfoil pocket form the impingement cooling circuit. The insert includes radial tube-like channels to distribute the cooling air and impingement cooling holes as a single piece
Data Source
AI summary
An air cooled turbine stator vane form a small gas turbine engine in which the vane has an airfoil of less than one inch in spanwise height, where the airfoil is a hollow airfoil having an insert that forms a sequential impingement cooling circuit for the pressure side wall and then the suction side wall. The insert includes a plurality of cooling air supply channels connected together by ribs where pressure side impingement holes are formed in the cooling air supply channels and suction side wall impingement cooling holes are formed in the ribs.