Cantilevered Rotor End Face Curvature for Sealing Gap Protection

Solution Overview

Problem

Cantilevered rotors in machines experience deflections due to imbalances and external forces, leading to potential contact with the housing, which can cause damage and failure, especially in sealing gaps where the rotor end face may rub against the fixed side, compromising the seal and machine operation.

Innovation Solution

Designing the rotor end face to be curved or tapered downward toward the bearing, with a gaseous fluid used for flushing the gap, and shaping the rotor and housing sides to maintain a constant or varying gap width, ensuring a free space for deflection without contact, such as using a truncated cone, dome, convex, or concave spherical configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gap width between rotor end face and housing is reduced to improve sealing, then sealing performance is improved, but the risk of contact during rotor deflection increases

Engineering Contradiction:

Improvesealing performanceVSAvoidcontact damage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The rotor end face is designed with a curved surface (spherical, conical, or cylindrical curvature) instead of a flat surface. This curvature creates a radial clearance profile where the gap width varies across the surface, providing a safety margin that prevents contact between the rotor end face and housing even when deflection occurs, while maintaining effective sealing performance.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If the rotor end face is made flat and parallel to maintain simple geometry, then manufacturing is easier, but deflection causes edge contact with housing

Engineering Contradiction:

Improve rotor face fabricationVSAvoiddeflection contact prevention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The rotor end face is designed with a curved surface (spherical, conical, or cylindrical curvature) instead of a flat surface. This curvature creates a radial clearance profile where the gap width varies across the surface, providing a safety margin that prevents contact between the rotor end face and housing even when deflection occurs, while maintaining effective sealing performance.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Object-affected harmful factors

If the gap width is increased to accommodate rotor deflection, then contact prevention is improved, but sealing effectiveness deteriorates

Engineering Contradiction:

Improvecontact preventionVSAvoidsealing effectiveness

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The gap width is made non-uniform across the rotor end face surface, with different radial clearances at different locations. The curved surface design creates larger clearance at the edges and smaller clearance toward the center (or vice versa depending on curvature direction), optimizing both contact prevention and sealing effectiveness at different locations simultaneously.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The rotor end face is designed with a curved surface (spherical, conical, or cylindrical curvature) instead of a flat surface. This curvature creates a radial clearance profile where the gap width varies across the surface, providing a safety margin that prevents contact between the rotor end face and housing even when deflection occurs, while maintaining effective sealing performance.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Reliability

If purge gas flow rate is increased to improve sealing, then sealing performance is improved, but energy consumption increases

Engineering Contradiction:

Improvesealing performanceVSAvoidpurge gas energy consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The gap width parameter is optimized to a specific range (0.05-2.0 mm) based on rotor dimensions and operating conditions. This parameter optimization allows effective sealing with reduced purge gas flow rates, thereby reducing energy consumption while maintaining reliable sealing performance.

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

Prevents contact between the rotor end face and the housing during deflections, maintaining the seal integrity and preventing damage, while allowing for efficient operation and reliable running of the machine.

Implementation Method 1

devices for flushing the gap with a gaseous fluid are included

Methodology Applied

Scientific EffectGas flushing:

Data Source

PatentEP2886211B1Machine with cantilevered rotor

Publication Date: 2021.10.13 NETZSCH TROCKENMAHLTECHNIK GMBH

Figure 1
Figure 2
Figure 3

AI summary

Machine (1) with a rotor (2) cantilevered on a bearing (3), which has an axis of rotation (A) along which a free, hereinafter unsupported rotor end (4) extends from the bearing (3), which has a rotor end face (5) which is spaced apart from a fixed rotor opposite face (6) by a gap (8), and which is deflected relative to the axis of rotation (A) during operation of the machine (1) with the rotor (2) rotating, due to imbalances of the cantilevered rotor (2), in particular of the free unsupported rotor end (4), or due to forces introduced from the outside, wherein the rotor end face (5) is curved or chamfered at least in its edge region (9) towards its edge (R) and in the direction of the bearing (3).