Switchbacked Turbomachine Airfoil Cooling Passage

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Solution Overview

Problem

Existing cooling strategies for turbomachine airfoils are inefficient in heat dissipation and require high cooling fluid mass flow, often relying on film cooling which can lead to mixing of fresh and spent fluid, reducing effectiveness.

Innovation Solution

The airfoil design features a switchbacked passage with an inner cooling wall and flow-distributing forward wall, directing cooling fluid for impingement at the leading edge and conducting heat from the outer walls to the inner cooling wall, allowing efficient heat dissipation through outlets without significant fluid mixing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If film cooling is used to cool airfoil surfaces, then cooling coverage is improved, but cooling fluid mass flow requirement increases and mixing of fresh and spent fluid occurs reducing effectiveness

Engineering Contradiction:

Improveairfoil surface temperatureVSAvoidcooling fluid mass flow

Core Design Contradiction:

TemperatureVSQuantity of substance

Solution Approach 1:

The cooling passage is segmented into distinct functional zones: an incoming segment for introducing cooling fluid, a impingement zone with openings at the leading edge for direct cooling, and an outgoing segment for fluid discharge. This segmentation allows optimized cooling at each zone without requiring excessive overall fluid flow.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Cooling fluid is directed to impinge on the back side of the leading edge before the hot fluid reaches the critical airfoil surfaces. This preliminary cooling action prevents heat buildup at the most vulnerable location, reducing the total cooling fluid needed for effective thermal protection.

Inventive Principle:

Principle #10Preliminary action

2Temperature

If film cooling is used to cool airfoil surfaces, then cooling coverage is improved, but mixing of fresh and spent fluid reduces cooling effectiveness

Engineering Contradiction:

Improveairfoil surface temperatureVSAvoidcooling effectiveness

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The passage is divided into incoming and outgoing segments that are spatially separated and functionally distinct. The incoming segment delivers fresh cooling fluid to the impingement zone, while the outgoing segment collects and removes spent fluid, preventing mixing and maintaining cooling effectiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of allowing cooling fluid to flow along the surface and mix with hot gases (conventional film cooling), the invention inverts the approach by directing fluid to impinge perpendicular to the surface at the leading edge, then collecting it through a separate path, avoiding contamination with hot fluids.

Inventive Principle:

Principle #13The other way round (Inversion)

3Temperature

If conventional cooling passages are used, then manufacturing is simpler, but heat dissipation efficiency is insufficient

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidpassage structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The cooling passage transitions from a simple linear path to a three-dimensional switchbacked configuration with incoming and outgoing segments at different spatial locations. This dimensional complexity enables efficient heat dissipation through optimized fluid distribution while maintaining manufacturability through standard casting or machining processes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 design enhances heat dissipation efficiency with reduced cooling fluid mass flow requirements and improved cooling efficacy, achieving higher thermal performance without the need for film cooling, while being simpler and more cost-effective to manufacture.

Implementation Method 1

conducting heat to the inner cooling wall

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 2

dissipating heat from the inner cooling wall to cooling fluid flowing through at least one of the first passage and the second passage

Methodology Applied

Scientific EffectHeat absorption: Heat Exchanger

Implementation Method 3

direct cooling fluid from the incoming segment toward a back side of the leading edge for impingement thereon

Methodology Applied

Scientific EffectImpingement cooling: Convection

Data Source

PatentUS10196905B2Airfoil for turbomachine and method of cooling same

Publication Date: 2019.02.05 SOLAR TURBINES INC

AI summary

An airfoil for a turbomachine such as a gas turbine engine includes a switchbacked passage for conveying cooling fluid, and flow-distribution passages in a forward wall so as to direct cooling fluid from the internal passage for back side impingement upon a leading edge of the airfoil. An inner cooling wall forms a passage for discharging the spent cooling air from a trailing edge of the airfoil after impingement, and cools one of a pressure side and a suction side of the airfoil by way of conduction. The switchbacked passage may have a serpentine form.