Turbine Airfoil Cooling Structure with Impingement Insert
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Solution Overview
Problem
Conventional cooling structures for turbine airfoils in gas turbines face inefficiencies due to small cooling side areas at the leading edge, leading to inadequate cooling effectiveness and increased cooling air flow rates, which can deteriorate engine performance.
Innovation Solution
A cooling structure featuring film-cooling holes and impingement holes with heat-transfer promoting projections integrated into the internal surface of the turbine airfoil, where a hollow cylindrical insert supplies cooling air for impingement-cooling, reducing the number of film holes needed and optimizing airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening area of impingement holes is increased to cool the turbine airfoil, then cooling effectiveness is improved, but cooling air flow rate increases which deteriorates engine performance
Solution Approach 1:
The cooling function is segmented into two distinct mechanisms: impingement cooling through holes in the insert and film cooling through holes in the airfoil surface. This segmentation allows each mechanism to operate optimally with smaller individual opening areas, achieving sufficient cooling effectiveness without requiring large total cooling air flow rates
Solution Approach 2:
A hollow cylindrical insert is nested inside the turbine airfoil, creating a layered structure where the insert provides impingement cooling and the airfoil provides film cooling. This nested configuration maximizes heat transfer area and cooling efficiency within the limited space, reducing the need for high cooling air flow rates
2Device complexity
If the turbine airfoil leading edge is cooled only by convection cooling at the cooling sidewall, then device complexity is reduced, but cooling effectiveness is insufficient due to small cooling side area
Solution Approach 1:
The cooling approach is segmented into convection cooling at the sidewall and impingement cooling through the insert, with film cooling through the airfoil surface. This multi-segmented approach compensates for the limited cooling side area at the curved leading edge, providing sufficient cooling effectiveness without excessive complexity
Solution Approach 2:
The hollow cylindrical insert acts as an intermediary component between the cooling air supply and the airfoil internal surface. It distributes cooling air uniformly across the leading edge area, enabling effective impingement cooling without requiring complex cooling structures
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 configuration enhances heat transfer and cooling effectiveness while reducing the cooling air flow rate, maintaining engine performance by increasing the heat-transfer area without significant pressure loss.
Implementation Method 1
the insert has a plurality of impingement holes for impingement-cooling the internal surface
Implementation Method 2
enhances heat transfer and cooling effectiveness
Implementation Method 3
a plurality of film-cooling holes extending between the internal surface and the external surface and blowing the cooling air from the internal surface toward the external surface to film-cool the external surface
Implementation Method 4
cooling the turbine airfoil by heat absorption at the holes
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
A cooling structure of a turbine airfoil cools a turbine airfoil (10) exposed to hot gas (1), using cooling air (2) of a temperature lower than that of the hot gas. The turbine airfoil (10) includes an external surface (11), an internal surface (12) opposite to the external surface, a plurality of film-cooling holes (13) blowing the cooling air from the internal surface toward the external surface to film-cool the external surface, and a plurality of heat-transfer promoting projections (14) integrally formed with the internal surface and protruding inwardly from the internal surface. The turbine airfoil further includes a hollow cylindrical insert (20) which is positioned inside the internal surface of the turbine airfoil and to which the cooling air is supplied. The insert has a plurality of impingement holes (21) for impingement-cooling the internal surface (12).