Scroll Casing Design for Centrifugal Compressor Wake Loss Reduction
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Solution Overview
Problem
Centrifugal compressors face efficiency reduction and operating range limitations due to wake loss and diffuser stall issues caused by improper thickness of the diffuser outlet jaw portion, which can lead to increased resistance and blockage of fluid flow.
Innovation Solution
A scroll casing design where the relationship of Tb/Ta ≥ 1.0 is maintained in the angular position range from 180 degrees to 360 degrees, ensuring a gentle inclination of the swirling flow with respect to the outlet flow, thereby reducing interference and blockage, and preventing excessive wake loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness T of the diffuser outlet jaw portion is increased, then the structural strength is improved, but wake loss increases and efficiency is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness T of the diffuser outlet jaw portion within the range 0.02D ≤ T ≤ 0.05D, where D is the diffuser outlet diameter. This quantitative parameter optimization resolves the contradiction by finding the optimal thickness value that provides sufficient structural strength while minimizing wake loss and maintaining high efficiency.
2Loss of energy
If the thickness T of the diffuser outlet jaw portion is decreased, then wake loss is reduced, but the outlet flow is blocked and diffuser stall is induced
Solution Approach 1:
The patent resolves this contradiction by establishing the thickness T within the specific range 0.02D ≤ T ≤ 0.05D (where D is the diffuser outlet diameter). This parameter optimization ensures the thickness is sufficient to prevent flow blockage and diffuser stall while remaining thin enough to minimize wake loss.
Solution Approach 2:
The patent applies partial action by using a relatively thin diffuser outlet jaw portion (compared to conventional designs) within the optimized range, providing just enough thickness to prevent flow blockage while minimizing the adverse effects of excessive thickness on wake loss.
3Loss of energy
If the thickness T of the diffuser outlet jaw portion is too small, then wake loss is minimized, but the diffuser outlet jaw portion may chip undesirably
Solution Approach 1:
The patent resolves this contradiction by defining the thickness T within the optimized range 0.02D ≤ T ≤ 0.05D (where D is the diffuser outlet diameter). The lower bound 0.02D ensures sufficient structural reliability to prevent chipping, while the upper bound 0.05D prevents excessive wake loss, thus optimizing both structural integrity and aerodynamic performance.
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 effectively suppresses the reduction in efficiency and operating range of the centrifugal compressor by minimizing wake loss and diffuser stall, ensuring stable fluid flow and preventing surge.
Implementation Method 1
a diffuser portion (4) forming a diffuser passage (40) of the centrifugal compressor (1)
Implementation Method 2
a centrifugal compressor (1) used in a compressor part or the like of a turbocharger for an automobile or a ship imparts kinetic energy to a fluid through rotation of an impeller and discharges the fluid outward in the radial direction, thereby achieving a pressure increase of the fluid by utilizing the centrifugal force
Implementation Method 3
A fluid flowing from the outlet of the diffuser passage (40) into the scroll passage (50) has a swirl velocity component, which forms a swirling flow (SF) flowing toward the one-direction (UD) side along the inner peripheral surface (51)
Data Source
AI summary
A scroll casing for a centrifugal compressor satisfies a relationship of Tb/Ta≥1.0 in a range of an angular position around a scroll center of the scroll passage from 180 degrees to 360 degrees, where Ta is a passage width of the diffuser passage along an axial direction of the centrifugal compressor, Tb is a shortest distance from a start position which is a connection position with a hub-side passage surface of the diffuser passage on an inner peripheral surface of a scroll portion forming the scroll passage to a virtual arc that touches an end position which is a position opposite to the start position on the inner peripheral surface, and the angular position is defined so that the angle gradually increases from a merging position between a scroll start and a scroll end of the scroll passage of 60 degrees to the downstream side of the scroll passage.