Internal Pipe Riblet Coating via Reverse Mold Inversion

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Solution Overview

Problem

Existing methods for applying riblet structures to interior surfaces of pipes are complex and costly, limiting their application to high-value goods, and there is a need for a simplified method to achieve drag reduction on large, difficult-to-reach surfaces.

Innovation Solution

A method involving a reverse printing process where a resin layer is applied to the pipe's internal surface, followed by a cavity mold with a reverse riblet pattern, and an air bag is used to hold the mold against the surface until the coating cures, allowing for the removal of the mold and air bag to yield a pipe with an internal riblet structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional manufacturing techniques (grooving, molding, grinding, laser-beam-removing) are used to create riblet structures, then the riblet structure can be formed on the surface, but the process becomes complex and costly, limiting application to high-value goods

Engineering Contradiction:

Improveriblet structure formationVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Instead of removing material to create riblets (grinding, laser-beam-removing) or using complex molding processes, the invention applies a coating material and uses a cavity mold with reverse riblet pattern that is pressed against the coated surface. The riblets are formed by the negative impression of the mold cavity, simplifying the manufacturing process while achieving the desired riblet structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention introduces a cavity mold as an intermediary tool that transfers the riblet pattern to the coated surface. The mold acts as a mediator between the coating material and the final riblet structure, enabling complex riblet geometries to be formed through a simple pressing operation rather than complex direct manufacturing processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If riblet structures are applied to interior surfaces of pipes using existing methods, then drag reduction can be achieved, but the methods require specialized equipment and are costly

Engineering Contradiction:

Improvehydraulic dragVSAvoidapplication cost and equipment requirement

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The cavity mold used in this invention is made as a flexible or thin-walled structure that can be easily inserted into and removed from pipe interiors. This flexibility allows the mold to conform to the pipe's internal geometry and be handled with simple equipment, eliminating the need for complex specialized application equipment while still achieving effective riblet formation for drag reduction.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The invention employs a simple, inexpensive cavity mold that can be used for coating application and then removed. The mold itself does not need to be a durable, expensive component but serves its purpose during the coating process, reducing overall manufacturing costs compared to permanent specialized equipment required by traditional methods.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Loss of energy

If riblet structures are created on large, difficult-to-reach surfaces, then drag reduction is achieved, but the existing methods are too complex and costly for such applications

Engineering Contradiction:

Improvefluid flow resistanceVSAvoidequipment complexity for hard-to-reach surfaces

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The cavity mold is designed to be flexible and adaptable, allowing it to be inserted into and conform to various pipe geometries and sizes. This dynamic capability enables the same basic mold design to be used on different surfaces including large, difficult-to-reach pipe interiors, eliminating the need for custom complex equipment for each application scenario.

Inventive Principle:

Principle #15Dynamics

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 is cost-effective, requires no specialized equipment, and provides a strong adhesion between the riblet structure and the substrate, enhancing fluid flow by reducing hydraulic resistance without the need to rebuild pipelines.

Implementation Method 1

A flexible air bag is inserted into the interior of the pipe and charged with air to hold the mold against the coated internal surface of the pipe

Methodology Applied

Scientific EffectPressure: Pressure Increase

Implementation Method 2

The air bag may be charged with air for a sufficient amount of time to allow the coating to cure in the riblet shape of the mold

Methodology Applied

Scientific EffectCuring: Phase Change

Data Source

PatentUS10322436B2Method of coating interior surfaces with riblets

Publication Date: 2019.06.18 HONG KONG APPLIED SCI & TECH RES INST

AI summary

A method of applying a riblet structure coating on the internal surface of a pipe includes coating the internal surface of a pipe with a resin layer and applying a cavity mold having a reverse riblet pattern structure to the coated internal surface of the pipe. A flexible air bag is inserted into the interior of the pipe and charged with air to hold the mold against the coated internal surface of the pipe. The air bag may be charged with air for a sufficient amount of time to allow the coating to cure in the riblet shape of the mold. Afterwards, the air bag and the mold are removed from the pipe to yield a pipe coated with an internal riblet structure.