Gas Turbine Cooling Holes With Cast Diffusers and Drilled Passages

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Solution Overview

Problem

Existing methods for fabricating film cooling holes in gas turbine parts often fail to efficiently create complex geometries that promote laminar flow and film attachment, as they are either costly and time-consuming or lack the necessary diffusion characteristics.

Innovation Solution

A multi-step method involving lost-material casting to form a model with complex aperture indentations and subsequent drilling to create simple geometry passages, allowing for a combination of complex and simple geometries in cooling holes that enhance airflow and film attachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If complex hole geometries are fabricated by electric discharge machining (EDM), then superior diffusion characteristics and laminar flow are achieved, but manufacturing cost and time increase

Engineering Contradiction:

Improvecomplex geometry precisionVSAvoidmanufacturing speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The cooling hole geometry is divided into two distinct sections: a complex geometry section (aperture indentation) formed by EDM for superior diffusion characteristics, and a simple geometry section (cylindrical passage) formed by laser drilling for efficiency. This segmentation allows each section to be optimized by the most appropriate manufacturing method.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different geometric characteristics are applied to different sections of the cooling hole. The aperture indentation section has a complex, non-cylindrical geometry designed for optimal flow diffusion, while the passage section has a simple cylindrical geometry suitable for high-speed drilling. Each section's geometry is locally optimized for its specific function.

Inventive Principle:

Principle #3Local quality

2Productivity

If simple cylindrical bores are formed via laser drilling, then manufacturing speed and cost are reduced, but diffusion characteristics and film flow attachment deteriorate

Engineering Contradiction:

Improvemanufacturing speedVSAvoidgeometry complexity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The cooling hole is segmented into two parts: the aperture indentation formed by laser drilling provides the entry point with simple geometry for efficiency, while the passage section extends from this indentation and is also formed by laser drilling, maintaining manufacturing speed while allowing the complex geometry to be achieved in the aperture section.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The aperture indentation with complex geometry is formed first through laser drilling to establish the entry point and initial flow characteristics. Then the passage is drilled from this pre-formed indentation, allowing the complex geometry section to be prepared in advance with the appropriate diffusion characteristics.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If abrupt transitions between planar walls and cylindrical holes are used, then manufacturing is simplified, but film flow attachment and laminar flow characteristics deteriorate

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidflow characteristics

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The aperture indentation features curved, non-abrupt transitions between the planar wall surface and the cylindrical passage. The complex geometry of the aperture indentation creates smooth, rounded transitions that promote laminar flow and help keep the film flow attached to the surface, eliminating the harmful abrupt transitions of simple cylindrical holes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The transition zone at the aperture indentation is given special geometric characteristics with curved surfaces and non-cylindrical shapes that specifically address flow attachment requirements. This local geometric optimization at the critical transition zone improves film flow attachment without complicating the entire hole structure.

Inventive Principle:

Principle #3Local quality

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 method effectively promotes laminar flow and keeps film flow attached to the surface, improving the efficiency of film cooling in gas turbine parts by combining complex and simple geometries in cooling holes, thereby enhancing temperature tolerance and operational efficiency.

Implementation Method 1

forming a model of a wall of a gas turbine part by lost-material casting

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

a passage possessing a simple geometry is formed using a drilling technique

Methodology Applied

Scientific EffectDrilling:

Data Source

PatentUS10927705B2Method for forming cooling holes having separate complex and simple geometry sections

Publication Date: 2021.02.23 RTX CORP

AI summary

A gas turbine part with a cooling hole, is fabricated by first forming a model of a wall of a gas turbine part. The wall is defined by first and second surfaces, the first surface having an aperture indentation possessing a complex geometry and extending into but not all the way through the wall of the gas turbine part. A mold of the wall of the gas turbine part is formed using the model and is used to cast the wall of the gas turbine part by lost-material casting. A passage is drilled through the resulting casting. This passage extends from the aperture indentation in the first surface through to the second surface.