Rotary Machine Lid Member Sealing Gap Control
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Solution Overview
Problem
In rotary machines like centrifugal compressors, the gap between the impeller and casing leads to fluid leakage, causing flow separation and vortex formation, which reduces compression efficiency due to the lack of effective sealing.
Innovation Solution
A rotary machine design incorporating a lid member with high machinability, positioned in the gap between the impeller cover and casing, which is cut during operation to form a minimum gap, ensuring reduced fluid leakage and enhanced sealing by overlapping with the impeller cover's curved surface, thereby minimizing wear and contact damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gap is provided between the impeller and casing to prevent interference, then the reliability of the rotary machine is improved, but the fluid leakage increases causing flow separation and vortex formation which reduces the compression efficiency
Solution Approach 1:
A lid member is introduced as an intermediary component between the impeller cover and the casing. This lid member extends from the casing toward the impeller cover, forming a seal portion that blocks the gap. The lid member mediates between the need for a gap (to prevent interference) and the need to prevent fluid leakage, allowing both requirements to be satisfied simultaneously.
2Strength
If the lid member is made of the same material as the impeller cover, then the structural integrity is improved, but the wear and damage occur on the impeller cover during operation
Solution Approach 1:
The lid member is made of a material with different properties than the impeller cover - specifically, a material with higher machinability and softer characteristics. This local quality change allows the lid member to wear preferentially during operation, protecting the harder impeller cover from wear and damage while maintaining the sealing function.
Solution Approach 2:
The lid member is designed as a sacrificial component made of a softer, more easily replaceable material. During operation, the lid member undergoes wear and is periodically replaced, while the more expensive impeller cover remains protected. This approach treats the lid member as a disposable element that protects the main component.
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 design significantly reduces fluid leakage and pressure loss, improving compression efficiency and maintaining the machine's performance by ensuring a consistent and minimal gap between the lid member and the impeller cover.
Implementation Method 1
the lid member is cut when the end face of the cover comes in contact with the lid member during an operation of the rotary machine
Data Source
AI summary
A rotary machine includes an impeller. The impeller includes a discoid disk that rotates about an axis line, blades disposed circumferentially at intervals on a surface of the disk facing one side in a direction of the axial line and that form a flow path therebetween that extends radially outward from one side in the direction of the axial line, and a cover that covers the blades from a radially outer side. The rotary machine further includes a casing that covers the impeller from the radially outer side and forms a gap between the casing and an outer surface of the cover; a seal portion provided in the gap; and a lid member.