Multistage Centrifugal Compressor With Mixed-Flow Stage Matching
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Solution Overview
Problem
Centrifugal chillers in refrigeration systems face inefficiencies due to suboptimal design of compressor stages, leading to energy consumption and maintenance challenges, particularly in high-capacity applications where prior systems neglect cumulative benefits of fluid control across stages.
Innovation Solution
A multistage centrifugal compressor assembly with mixed flow impellers and a variable speed drive, featuring a final stage compressor and a non-final stage compressor, where each stage has a mixed flow impeller with constant relative diffusion, optimized for specific speed ranges to achieve efficient operation across a wide capacity range, and a vaneless diffuser with a wall profile matching the impeller hub and shroud, allowing for efficient fluid compression and reduced physical size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If prior multistage compressor systems are designed with each stage optimized independently, then each stage can perform optimally for its specific conditions, but the cumulative benefits of fluid control across stages are neglected leading to overall system inefficiency
Solution Approach 1:
The patent merges the fluid control functions across multiple compressor stages into an integrated system. The diffuser of a upstream stage is designed to work in conjunction with the impeller of the downstream stage, creating a unified fluid control pathway that optimizes overall system efficiency rather than individual stage performance.
Solution Approach 2:
The compressor stages are designed with universal fluid control characteristics where the diffuser structure serves multiple functions: it completes the fluid acceleration from the upstream impeller and prepares the fluid for the downstream impeller. This multi-functional design enables cumulative efficiency benefits across all stages.
2Productivity
If the first stage of a multistage compressor is sized to perform optimally, then the first stage achieves maximum efficiency, but the second (or later) stage is allowed to perform less than optimally
Solution Approach 1:
Each compressor stage is designed with localized quality optimizations tailored to its specific position in the multistage system. The first stage impeller and diffuser are optimized for initial compression conditions, while subsequent stages are optimized for the specific fluid conditions resulting from previous stages, ensuring each stage operates at peak efficiency for its local conditions.
Solution Approach 2:
The patent employs parameter changes across stages, where the diffuser outlet parameters (velocity, pressure distribution) of one stage are specifically designed to match the impeller inlet parameters of the next stage. This parameter matching ensures optimal performance at each stage while maintaining cumulative system efficiency.
3Productivity
If centrifugal chillers operate at high capacity, then they meet high cooling demand, but they consume significant energy resources
Solution Approach 1:
The patent replaces traditional mechanical optimization approaches with a fluid dynamics-based design system. By using computational fluid dynamics and optimized impeller-diffuser geometries, the system achieves higher efficiency at high capacity without relying on mechanical adjustments or additional components that would increase energy consumption.
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 solution results in high-performance, efficient operation with constant efficiency across varying capacities, reduced energy consumption, smaller size, lower noise levels, and cost savings by enabling fewer compressors to meet the same capacity requirements, while maintaining reliability and scalability.
Implementation Method 1
Centrifugal compression involves the purely rotational motion of only a few mechanical parts
Implementation Method 2
The impeller accelerates the fluid and in turn, increases the kinetic energy of the fluid
Implementation Method 3
a vaneless diffuser with a wall profile matching the impeller hub and shroud
Implementation Method 4
The diffuser is designed to follow the impeller hub and shroud meridional profile
Implementation Method 5
a variable speed drive, featuring a final stage compressor and a non-final stage compressor
Implementation Method 6
a permanent magnet motor controlled by a variable speed drive
Data Source
AI summary
A centrifugal compressor assembly for compressing refrigerant in a 250-ton capacity or larger chiller system comprising a motor, preferably a compact, high energy density motor or permanent magnet motor, for driving a shaft at a range of sustained operating speeds under the control of a variable speed drive. Another embodiment of the centrifugal compressor assembly comprises a mixed flow impeller and a vaneless diffuser sized such that a final stage compressor operates with an optimal specific speed range for targeted combinations of head and capacity, while a non-final stage compressor operates above the optimum specific speed of the final stage compressor. Another embodiment of the centrifugal compressor assembly comprises an integrated inlet flow conditioning assembly comprising a flow conditioning nose, a plurality of inlet guide vanes and a flow conditioning body that positions inlet guide vanes to condition flow of refrigerant into an impeller to achieve a target approximately constant angle swirl distribution with minimal guide vane turning.