Free Piston Cooling Channel Segmentation

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Solution Overview

Problem

The existing free-piston devices face challenges in effectively cooling the piston receptacle, particularly around the outlet openings where high temperatures can limit material selection and cause undesirable heating of adjacent components, such as the power coupling device.

Innovation Solution

The implementation of a cooling channel with multiple cooling regions, including first and second cooling areas positioned axially next to the outlet opening and radially surrounding the wall, along with a third cooling area that forms a flow connection to effectively cool the radial outer wall and reduce heat transfer to adjacent components, utilizing a cooling medium like water at 80 °C to 95 °C.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If cooling channels are provided around inlet and outlet openings, then cooling effect is improved, but device complexity increases

Engineering Contradiction:
Improvewall temperatureVSAvoidcooling device complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The cooling device is segmented into multiple cooling zones (first cooling zone around inlet opening, second cooling zone around outlet opening, and third cooling zone for radial outer wall). Each zone is independently configured to address specific thermal challenges at different locations, allowing targeted cooling without uniformly complicating the entire device structure.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different cooling strategies are applied to different regions: the first and second cooling zones use axial cooling approaches suitable for inlet and outlet areas, while the third cooling zone employs radial cooling for the outer wall. This localized approach optimizes cooling effectiveness for each specific thermal problem zone.

Inventive Principle:
Principle #3Local quality

2Temperature

If cooling channels are added to cool the piston receptacle, then temperature control is improved, but manufacturing complexity increases

Engineering Contradiction:
Improvepiston receptacle temperatureVSAvoidmanufacturing ease
Core Design Contradiction:
TemperatureVSEase of manufacture

Solution Approach 1:

The cooling channels are nested within the piston receptacle structure itself. The first cooling zone is formed within the piston receptacle wall, the second cooling zone is integrated around the outlet opening, and the third cooling zone is positioned for radial outer wall cooling. This nesting approach allows cooling functionality to be incorporated without adding separate external cooling components, thereby improving manufacturability.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Object-affected harmful factors

If the outlet opening area is cooled more intensively, then heat transfer to adjacent components is reduced, but cooling system complexity increases

Engineering Contradiction:
Improveheat transfer to adjacent componentsVSAvoidcooling system complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The third cooling zone extracts heat specifically from the radial outer wall area adjacent to the outlet opening. By positioning this cooling zone to target the specific region where heat would otherwise transfer to adjacent components, the solution removes the harmful thermal effect without requiring a complete redesign of the entire cooling system.

Inventive Principle:
Principle #2Taking out (Extraction)

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 the cooling efficiency of the piston receptacle, reduces heat transfer to adjacent components, and promotes the functionality of energy coupling devices, allowing for a more reliable and cost-effective operation of the free-piston device.

Implementation Method 1

The cooling channel (76) has several cooling zones. A first (78) and a second cooling zone (80) are arranged axially adjacent to the at least one outlet opening (36) and radially surround the wall (32), at least partially. At least one third cooling zone (82) is provided. This zone forms a flow connection from the first cooling zone (78) to the second cooling zone (80) along the axial extent of the outlet chamber (92).

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP3458681B1Free piston device
Publication Date: 2021.04.28 DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E V
  • EP3458681B1 patent drawingFigure 1
  • EP3458681B1 patent drawingFigure 2
  • EP3458681B1 patent drawingFigure 3

AI summary

The invention relates to a free piston device comprising a piston (42) which is arranged in a movable manner back and forth along an axis (26). The piston receiving area (24) comprises a combustion chamber (50) which is delimited by a wall (32). The free piston device (10) comprises a cooling device (74) which is arranged on the piston receiving area (24) for cooling the wall (32). The cooling device (74) has a cooling channel (76) which is arranged radially on the exterior of the wall (32) for a cooling medium in order to improve the cooling function, said cooling channel having a first cooling region (78) and a second cooling region (80) at axially opposite sides of an outlet opening (36). The cooling channel (76) additionally has at least one third cooling region (82) which fluidically connects the first cooling region (78) and the second cooling region (80) along the axial extension of the outlet chamber (92) and is positioned radially outside of the outlet chamber (92) at least in some sections.