Centrifugal Compressor Scroll With Variable Area Enlargement Rate
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Solution Overview
Problem
Centrifugal compressors face challenges in achieving high pressure and efficiency over a wide operating range due to uneven fluid velocity distribution across the scroll portion, leading to inadequate static pressure recovery and increased flow rate resistance.
Innovation Solution
The centrifugal compressor design features a scroll portion with a variable cross-sectional area enlargement rate, gradually increasing from the tongue portion to an arbitrary angle and then decreasing towards the winding end, creating regions for velocity reduction and increase to optimize fluid flow and pressure recovery, while preventing boundary layer development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cross-sectional area of the scroll portion is increased at a constant rate according to fluid inflow, then the fluid velocity becomes constant, but the static pressure recovery is insufficient and flow rate resistance increases
Solution Approach 1:
The patent applies dynamics by making the cross-sectional area enlargement rate variable rather than constant. The enlargement rate changes according to the fluid inflow amount, creating a dynamic adaptation system that optimizes both flow rate and pressure recovery under different operating conditions. This resolves the contradiction by allowing the scroll geometry to actively respond to varying flow conditions.
Solution Approach 2:
The patent changes the geometric parameter of the scroll portion by varying the cross-sectional area enlargement rate. Specifically, the ratio of the cross-sectional area enlargement rate to the fluid inflow amount is adjusted to be greater than a predetermined value, which fundamentally alters the flow characteristics and enables simultaneous improvement of productivity and pressure recovery.
2Loss of energy
If the cross-sectional area of the scroll portion is linearly increased to decrease fluid velocity, then static pressure recovery improves, but boundary layer development occurs and operating range reduces
Solution Approach 1:
The variable enlargement rate creates a dynamic system that can adapt to different operating conditions. By adjusting the enlargement rate based on fluid inflow amount, the system maintains optimal performance across a wide operating range without the adverse effects of linear increase, such as boundary layer development.
Solution Approach 2:
The patent applies local quality by creating different flow conditions in different regions of the scroll portion. The cross-sectional area enlargement rate is locally adjusted according to the fluid inflow amount, creating velocity decrease regions and velocity increase regions that collectively prevent boundary layer development while maintaining pressure recovery.
3Stress or pressure
If the scroll cross-sectional area is increased to reduce fluid velocity, then pressure ratio improves, but flow rate resistance increases
Solution Approach 1:
The patent changes the critical parameter of cross-sectional area enlargement rate to simultaneously improve pressure ratio and reduce flow rate resistance. By setting the ratio of enlargement rate to fluid inflow amount greater than a predetermined value, the system achieves optimal balance between pressure recovery and flow efficiency.
Solution Approach 2:
The dynamic adjustment of enlargement rate based on fluid inflow allows the system to maintain low flow rate resistance while achieving high pressure ratio. The variable geometry adapts to flow conditions, preventing the trade-off that would occur with fixed geometry designs.
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 pressure ratio and efficiency of the centrifugal compressor by accurately calculating the volumetric flow rate and reducing fluid velocity, thereby stabilizing flow and minimizing losses.
Implementation Method 1
a diffuser portion (13) which forms a roughly donut shape on an outer circumferential side of the compressor impeller (3) and which enables recovery of static pressure by decreasing the velocity of fluid that is discharged from the compressor impeller (3)
Implementation Method 2
A compressor 1 of a centrifugal compressor mainly comprises a compressor impeller 3 constituted by a rotating hub 31 and a large number of centrifugal vanes 32 attached to an outer circumferential surface of the hub 31
Data Source
Figure 1~2
Figure 3A~3C
Figure 4A~4C
AI summary
In a scroll shape of a centrifugal compressor, an enlargement rate of a ratio A/R of a cross-sectional area A of a scroll portion 12 to a radius R from an axis L1 of a compressor impeller 3 to a centroid P0 of a cross section of the scroll portion is reduced from a winding start to a winding end of the scroll portion.