Film Cooling Structure With Diffuser Part For Turbine Blades

Solution Overview

Problem

Current film cooling structures for gas turbine blades are inadequate in improving cooling efficiency as combustion temperatures increase, leading to thermal damage from combustion gases.

Innovation Solution

A film cooling structure featuring inclined cooling holes with a straight-tube part and a diffuser part, where the diffuser part has a semicircular or semi-elliptical channel cross section that expands as it approaches the outlet, reducing aerodynamic loss and enhancing cooling efficiency by creating a secondary flow that spreads the cooling medium.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the combustion temperature is increased to improve gas turbine engine efficiency, then the cooling efficiency of the turbine blade must be improved to prevent thermal damage

Engineering Contradiction:

Improvecombustion temperatureVSAvoidthermal damage from combustion gas

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The cooling hole is divided into two functional segments: a straight-tube part for direct cooling and a diffuser part for flow distribution. This segmentation allows each part to perform its specific function optimally, with the straight-tube part delivering cooling medium efficiently and the diffuser part spreading it to cover larger surface areas, thereby improving overall cooling effectiveness against high-temperature combustion gases.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The diffuser part features a curved channel cross-section that transitions from circular/elliptical to a larger curved shape, creating a smooth flow path. This curvature design reduces flow separation and aerodynamic loss while enhancing the spreading effect of the cooling medium, allowing the cooling film to cover more extensive areas of the turbine blade surface.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If conventional cooling holes are used, then the structure is simple, but the cooling efficiency is insufficient for high combustion temperatures

Engineering Contradiction:

Improvecooling efficiencyVSAvoidcooling hole structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The cooling hole is divided into two functional segments: a straight-tube part for direct cooling and a diffuser part for flow distribution. This segmentation allows each part to perform its specific function optimally, with the straight-tube part delivering cooling medium efficiently and the diffuser part spreading it to cover larger surface areas, thereby improving overall cooling effectiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The diffuser part features a curved channel cross-section that transitions from circular/elliptical to a larger curved shape, creating a smooth flow path. This curvature design reduces flow separation and aerodynamic loss while enhancing the spreading effect of the cooling medium.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Area of stationary object

If the cooling medium is concentrated in a small area, then the cooling hole structure is simple, but the cooling coverage is limited

Engineering Contradiction:

Improvecooling coverage areaVSAvoiddiffuser part geometry

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The diffuser part employs a curved channel cross-section that expands from the straight-tube part, creating a gradual transition zone. This curved geometry promotes smooth flow attachment and enhances the lateral spreading of the cooling medium, significantly increasing the cooling coverage area on the turbine blade surface while maintaining flow efficiency.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The diffuser part transitions the cooling medium from a one-dimensional axial flow in the straight-tube part to a two-dimensional expanded flow in the diffuser section. This dimensional transition allows the cooling medium to spread laterally across a broader area, enhancing cooling coverage without requiring multiple separate cooling holes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Reliability

If the diffuser part has a large channel cross section, then the cooling medium spreads better, but the aerodynamic loss increases

Engineering Contradiction:

Improvecooling efficiencyVSAvoidaerodynamic loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The curved channel cross-section in the diffuser part creates a smooth, continuous flow path that minimizes flow separation and turbulence. This curvature design allows the cooling medium to expand and spread effectively while maintaining attached flow, thereby reducing aerodynamic loss compared to sharp-angled or abrupt expansion designs.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The diffuser part gradually changes the channel cross-sectional parameters (area, shape, orientation) along its length, creating an optimized expansion profile. This gradual parameter change reduces flow separation and minimizes aerodynamic loss while still achieving effective spreading of the cooling medium across the turbine blade surface.

Inventive Principle:

Principle #35Parameter changes

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 proposed film cooling structure improves cooling efficiency by reducing aerodynamic loss and spreading the cooling medium, effectively protecting the turbine blades from high-temperature combustion gases while minimizing pressure loss.

Implementation Method 1

a diffuser part connecting with the straight-tube part and having the outlet, the straight-tube part is positioned inside the diffuser part on a projection plane of the cooling hole orthogonal to an extending direction of the cooling hole

Methodology Applied

Scientific EffectAerodynamic loss reduction through diffuser geometry: Diffusion

Implementation Method 2

a number of film cooling holes are formed on an airfoil surface of each turbine blade... the cooling medium spreads the cooling medium

Methodology Applied

Scientific EffectFilm cooling: Convection

Data Source

PatentEP3981954B1Film cooling structure and turbine blade for gas turbine engine

Publication Date: 2024.05.01 IHI CORP

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AI summary

The film cooling structure includes a wall part 20 and a cooling hole 30 inclined such that an outlet 32 is positioned rearward of an inlet 31. The cooling hole 30 includes a straight-tube part 33 and a diffuser part 34. The diffuser part 34 includes a flat surface 37, a curved surface 38 curved rearward and forming, together with the flat surface 37, a semicircular or semi-elliptical channel cross section larger than that of the straight-tube part 33, a first section 40 in which an area of the channel cross section increases as it approaches the outlet 32 of the cooling hole 30, and a second section 41 in which the area of the channel cross section increases as it approaches the outlet 32 of the cooling hole 30 at an increase rate smaller than that of the first section 40 or is constant, extending from the first section 40 toward the outlet 32 of the cooling hole 30. The diffuser part 34 has a width equal to or twice greater than the depth of the diffuser part 34.