Centrifugal Compressor Recirculation Volute for Part-Load Stability
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Solution Overview
Problem
Refrigerant compressors face challenges in efficiently managing capacity control during part-load operating conditions, particularly in maintaining flow angles and velocities similar to full-load design conditions without the complexity and maintenance issues associated with variable-geometry diffusers and inlet guide vanes.
Innovation Solution
A centrifugal compressor design featuring a recirculation flow path between specific locations along the main refrigerant flow path, utilizing a recirculation volute and nozzles to recirculate refrigerant, which is regulated by a flow regulator controlled by a controller to inject refrigerant back into the main flow path, thereby maintaining stability and efficiency without the need for inlet guide vanes or variable geometry diffusers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable-geometry diffusers are used to improve capacity control during part-load conditions, then flow angles and velocities are maintained similar to full-load design conditions, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent removes the variable-geometry diffuser component from the system and replaces it with a recirculation flow path that extracts excess refrigerant from the discharge side and returns it to the suction side, achieving capacity control without the complex mechanical adjustments of variable-geometry diffusers
Solution Approach 2:
The recirculation flow path acts as an intermediary mechanism, taking refrigerant from the discharge side and injecting it back into the suction side to modulate the effective flow through the compressor, providing capacity control without direct mechanical intervention in the diffuser
2Adaptability or versatility
If inlet guide vanes are used to regulate capacity during various operating conditions, then capacity control is improved, but reliability decreases due to maintenance-prone mechanical parts
Solution Approach 1:
The patent eliminates inlet guide vanes from the system and replaces their capacity regulation function with a recirculation flow path that achieves the same effect by returning refrigerant from discharge to suction, removing mechanical parts that require maintenance
Solution Approach 2:
The patent replaces the mechanical adjustment system of inlet guide vanes with a fluid-based recirculation system that uses flow dynamics and pressure differential to achieve capacity control without moving mechanical parts at the inlet
3Reliability
If recirculation flow path is implemented to improve capacity control, then operational stability is enhanced and efficient operating range is extended to lower part-load conditions, but device complexity increases
Solution Approach 1:
The recirculation flow path serves multiple functions simultaneously: it provides capacity control, maintains operational stability, extends the efficient operating range to part-load conditions, and eliminates the need for variable-geometry diffusers and inlet guide vanes, achieving multiple benefits with a single integrated system
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 design enhances the compressor's operational stability and extends its efficient operating range to lower part-load conditions, reducing the likelihood of surge conditions and eliminating the need for maintenance-prone mechanical parts like inlet guide vanes and variable geometry diffusers, thereby increasing reliability.
Implementation Method 1
the recirculation flow path is provided between a first location and a second location along the main refrigerant flow path. The first location is downstream of the second location, and the second location is downstream of the first impeller
Implementation Method 2
the recirculation flow path includes a recirculation volute
Data Source
AI summary
This disclosure relates to a centrifugal compressor. In a first example, the compressor includes a first impeller provided in a main refrigerant flow path, a second impeller provided in the main refrigerant flow path downstream of the first impeller, and a recirculation flow path. In the first example, the recirculation flow path is provided between a first location and a second location along the main refrigerant flow path. The first location is downstream of the second location, and the second location is downstream of the first impeller. In a second example, the compressor includes an impeller provided in a main refrigerant flow path, and a recirculation flow path provided between a first location and a second location along the main refrigerant flow path. In the second example, the recirculation flow path includes a recirculation volute. Further disclosed is a method for operating a centrifugal compressor.