Centrifugal Compressor Dual-Casing Intermediate Suction Flow Path
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Solution Overview
Problem
In centrifugal compressors with intermediate suction flow paths, reducing the outer diameter of the casing increases gas flow velocity and friction loss, leading to decreased efficiency and increased cost due to smaller diffuser static pressure recovery and larger dynamic pressure at the diffuser outlet.
Innovation Solution
A centrifugal compressor design featuring a first casing with a smaller outer diameter and a second coaxial casing with a larger outer diameter, including an intermediate suction flow path and a second return flow path, which increases the flow path cross-sectional area and reduces friction loss, while allowing for a smaller first casing diameter to minimize cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the outer diameter of the casing is decreased to reduce cost, then the manufacturing cost is reduced, but the flow path cross-sectional area is reduced causing increased flow velocity and friction loss which decreases efficiency
Solution Approach 1:
The casing is divided into two separate casings: a first casing with a smaller outer diameter and a second casing with a larger outer diameter. The first casing contains the first impeller and associated flow paths, while the second casing contains the second impeller and the intermediate suction flow path. This segmentation allows each casing to be optimized independently, enabling the first casing to be smaller for cost reduction while the second casing provides the larger diameter needed for low-velocity flow paths.
Solution Approach 2:
The patent transitions from a single-casing design to a dual-casing design, adding a dimensional aspect to the structure. By stacking casings in the axial direction rather than relying solely on radial expansion, the design achieves the benefits of a large-diameter casing for the intermediate suction path without proportionally increasing the overall size and cost of the entire compressor.
2Ease of manufacture
If the outer diameter of the first casing is reduced to minimize cost, then the manufacturing cost is reduced, but the diffuser static pressure recovery becomes small and dynamic pressure at the diffuser outlet becomes large increasing downstream friction loss
Solution Approach 1:
The diffuser system is segmented into a first diffuser in the first casing and a second diffuser in the second casing. The first diffuser handles the flow from the first impeller, while the second diffuser handles the intermediate suction flow. This segmentation allows the second diffuser to be designed with optimal dimensions for handling the intermediate suction flow, ensuring adequate static pressure recovery and minimizing dynamic pressure at the outlet, thereby reducing downstream friction loss in the return vane and discharge scroll.
3Device complexity
If a single casing design is used, then the structure is simpler, but the intermediate suction flow path cannot have sufficient cross-sectional area leading to high flow velocity and efficiency loss
Solution Approach 1:
The compressor is divided into two functional sections with separate casings: the first casing for the first compression stage and the second casing for the second compression stage with intermediate suction. This segmentation creates dedicated space for the intermediate suction flow path with adequate cross-sectional area, allowing it to operate at appropriate flow velocities and maintain high compressor efficiency.
Solution Approach 2:
The first casing is positioned inside or concentric with the second casing, creating a nested configuration. The first casing contains components for the first compression stage, while the second casing contains components for the second compression stage including the intermediate suction flow path. This nested arrangement efficiently utilizes space while providing the larger volume needed for the intermediate suction path in the outer casing.
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 efficiency of the centrifugal compressor by reducing flow velocity and friction loss in the intermediate suction flow path, while also reducing the overall cost by allowing a smaller first casing diameter, and minimizes gas separation in the discharge scroll through increased curvature.
Implementation Method 1
a centrifugal rotary machine having a plurality of impellers provided on a rotating shaft
Implementation Method 2
static pressure recovery at the diffuser becomes small and dynamic pressure at an outlet of the diffuser becomes large
Data Source
AI summary
The present invention provides a centrifugal compressor (1) including: a first casing (19); a second casing (20) which is disposed on a downstream side of the first casing (19) and has an outer diameter larger than an outer diameter of the first casing; a first impeller (3a) which is disposed on a radially inner side of the first casing; a first return flow path (29a) which is disposed on a radially inner side of the first casing; a second impeller (3b) which is disposed on a radially inner side of the second casing and connected to a downstream side of the first return flow path (29a); an intermediate suction flow path (10) which is disposed on the radially inner side of the second casing and additionally supplies the fluid to a flow path between the first return flow path (29a) and the second impeller (3b); and a second return flow path (29b) which is disposed on the radially inner side of the second casing (20), wherein an outer diameter of the intermediate suction flow path (10) and an outer diameter of the second return flow path (29b) are larger than the outer diameter of the first casing (19).