Gear Root Geometry for Cavitation Mitigation

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Solution Overview

Problem

Gear pumps experience damage due to cavitation at the gear roots caused by vapor bubble formation and collapse, resulting from local pressure falling below the fluid's vapor pressure.

Innovation Solution

A gear pump design featuring a gear root with a stretched root blended into an involute tooth profile curve within a True Involute Form diameter, providing an enlarged carry-over volume that reduces the rate of pressure increase and suppresses bubble formation, thereby mitigating cavitation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a standard full fillet root profile is used, then the gear structure is simple and easy to manufacture, but the carry-over volume is insufficient leading to cavitation damage

Engineering Contradiction:

Improvecavitation resistanceVSAvoidgear root geometry complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by modifying only the gear root geometry while maintaining the standard involute tooth profile. The stretched root profile with increased carry-over volume is implemented locally at the root region to prevent cavitation, while the rest of the gear structure remains conventional and easy to manufacture.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameters of the gear root by stretching the root profile and increasing the carry-over volume. This parameter modification transforms the root geometry from a standard fillet shape to an optimized shape that reduces pressure rise rates and suppresses vapor bubble formation, thereby preventing cavitation damage.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the carry-over volume is increased, then cavitation is suppressed, but the gear root geometry becomes more complex

Engineering Contradiction:

Improvecavitation erosionVSAvoidgear root profile shape

Core Design Contradiction:

Object-affected harmful factorsVSShape

Solution Approach 1:

The modified root profile is applied locally only to the gear root region, leaving the tooth profile and other gear features unchanged. This localized modification increases carry-over volume where needed to suppress cavitation while maintaining overall gear simplicity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses curved transitions and blended profiles in the stretched root design. The smooth curvature of the blended root profile helps distribute stress and maintain fluid flow patterns that suppress vapor bubble formation, while the curved geometry remains manufacturable using conventional gear cutting methods.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 modified gear root geometry reduces cavitation erosion and damage by increasing energy storage capability, maintaining effective fluid pressure and preventing bubble formation, leading to decreased dynamic pressure loss and reduced severity of cavitation.

Implementation Method 1

Gear pumps have historically experienced damage at the gear roots due to cavitation which occurs when local pressure falls below the fluid's vapor pressure. Formation of vapor bubbles and the subsequent collapse thereof may result in the damage.

Methodology Applied

Scientific EffectCavitation: Cavitation