Centrifugal compressor with recirculation passage
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Solution Overview
Problem
Centrifugal compressors face instability and reduced efficiency due to recirculation passages, particularly at varying load conditions, which can lead to undesirable backflow and pressurized gas reversal.
Innovation Solution
A centrifugal compressor design featuring a movable ring that obstructs openings defining a recirculation passage, controlled by a controller linked to inlet guide vanes, allowing for variable recirculation passage configuration based on load levels to prevent surge and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a recirculation passage is provided in a centrifugal compressor, then stability is improved and surge line is moved, but efficiency is reduced at loads away from surge
Solution Approach 1:
The recirculation passage is made variable rather than fixed. A movable ring with adjustable position allows the recirculation opening area to be dynamically changed based on operating conditions. This enables the system to adapt between stability requirements at partial loads and efficiency requirements at higher loads, resolving the contradiction by making the recirculation passage dynamic instead of static
Solution Approach 2:
The opening area of the recirculation passage is changed as a variable parameter. By adjusting the position of the movable ring, the effective opening area of the recirculation passage can be modified to match different operating conditions, allowing optimization of both stability and efficiency across the operating range
2Stability of the object's composition
If recirculation passage is opened to prevent surge at partial loads, then stability is improved, but pressurized gas backflow occurs
Solution Approach 1:
The recirculation passage opening is made dynamically adjustable through the movable ring mechanism. This allows the system to provide just enough recirculation to prevent surge without excessive opening that would cause harmful backflow, adapting the recirculation level to actual operating conditions
Solution Approach 2:
The system uses feedback from operating conditions (load level, pressure differential) to control the position of the movable ring. This feedback mechanism ensures the recirculation passage opening is optimized to prevent surge while minimizing harmful backflow effects
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 enhances stability and minimizes surge conditions at partial loads without efficiency penalties typically associated with ported shrouds, by adjusting recirculation levels according to load, thereby maintaining operational stability and efficiency across different operating conditions.
Implementation Method 1
An impeller is disposed within the housing and is rotatable about a longitudinal axis to draw fluid into the inlet chamber. The fluid is directed radially outward from the axis through a diffuser passage that increases a pressure of the fluid
Implementation Method 2
A ring is provided and a controller moves the ring along the longitudinal axis between a first position and a second position when rotating the inlet guide vanes. The ring obstructs at least one of the first and second openings more in the second position than in the first position
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An example centrifugal compressor 322 includes a housing 140 that defines an inlet chamber 44 and includes first and second openings 148, 50 that define a recirculation passage 52 in fluid communication with the inlet chamber 44. An impeller 56 is disposed within the housing 140 and is rotatable about a longitudinal axis A to draw fluid into the inlet chamber 44. The first and second openings 148, 50 are at different axial locations along the longitudinal axis.