Rotary Machine Inlet Guide Vane Axial Overlap
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Solution Overview
Problem
Centrifugal compressors with inlet guide vanes are prone to self-excited vibration due to the cantilever shape of the vanes, which can lead to increased flow rates and jet generation between the vane and impeller.
Innovation Solution
A rotary machine design where the inlet guide vane blades extend radially inward from the housing, with their tip portions positioned on the outer side of the impeller cap, overlapping it in the axial direction, thereby shortening the blade height and reducing self-excited vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the inlet guide vane extends further in the radial direction to increase flow control capability, then the flow rate adjustment performance is improved, but self-excited vibration occurs more easily
Solution Approach 1:
The patent positions the blade tip in the axial direction rather than extending it further radially. By utilizing the axial dimension (overlapping with the impeller cap in the axial direction) instead of increasing radial length, the design achieves flow control capability while avoiding the vibration issues associated with long radial extensions.
Solution Approach 2:
The patent changes the spatial arrangement parameter by positioning the blade tip at a specific axial location overlapping with the impeller cap. This parameter change transforms the blade configuration from a long radial cantilever to a shorter blade with axial overlap, fundamentally altering the vibration characteristics while maintaining flow control function.
2Adaptability or versatility
If the blade height is increased to improve flow control, then the flow rate regulation is enhanced, but the natural frequency decreases making vibration more likely
Solution Approach 1:
Instead of increasing blade height in the radial direction (which would lower natural frequency), the patent utilizes the axial dimension by positioning the blade tip to overlap with the impeller cap axially. This dimensional shift allows for effective flow control without increasing the critical radial blade height that would reduce natural frequency.
3Adaptability or versatility
If the inlet guide vane is made longer radially to increase flow control range, then the flow adjustment capability is improved, but jet generation between the vane and impeller increases
Solution Approach 1:
The patent achieves flow control range by positioning the blade tip axially overlapping with the impeller cap rather than extending the blade radially. This axial positioning approach provides sufficient flow control capability while preventing the formation of harmful jets that occur with long radial blade extensions.
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 effectively suppresses self-excited vibration and jet generation between the inlet guide vane and impeller, enhancing the stability and efficiency of the compressor by increasing the natural frequency of the blades and minimizing the blade height.
Implementation Method 1
an inlet guide vane that is disposed inside the housing on a first side in the axial direction with respect to the impeller, and has a plurality of movable blades that extend from the housing toward an inner side in a radial direction around the axis
Implementation Method 2
a centrifugal compressor flows a working fluid inside a rotating impeller and compresses the working fluid, which is in a gaseous state, by using the centrifugal force generated when the impeller rotates
Data Source
AI summary
A rotary machine includes a rotor that includes an impeller cap that regulates the movement of an impeller fixed to a rotary shaft that extends in an axial direction about the axis; a housing that covers a rotor; and an inlet guide vane that has a plurality of movable blades that extend from the housing toward an inner side in a radial direction and disposed at intervals in a circumferential direction, in which a blade tip portion, which is a tip end of the movable blade in the radial direction, is disposed on the outer side in the radial direction with respect to an outer peripheral surface of the impeller cap, and the position of at least a part of the blade tip portion in the axial direction overlaps the position of the impeller cap in the axial direction.