Non-axisymmetric Diffuser Pipe for Centrifugal Compressor Flow Control

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Solution Overview

Problem

Non-uniform flow in diffuser pipes of centrifugal compressors due to boundary layer build-up and vortices reduces aerodynamic performance and operating range, particularly at the impeller exit where incidence creates low momentum flow accumulation.

Innovation Solution

The diffuser pipes are designed with a non-axisymmetric shape featuring surface contours on the inner surface, specifically between the throat and the curved portion, to minimize boundary layer growth and prevent vortex formation by creating a non-uniform outer perimeter shape that limits boundary layer expansion and redirects flow uniformly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If diffuser pipes are designed with conventional axisymmetric shape, then manufacturing is simple, but boundary layer build-up and vortex formation occur reducing aerodynamic performance

Engineering Contradiction:

Improvediffuser pipe manufacturing simplicityVSAvoidaerodynamic performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The diffuser pipe employs a non-axisymmetric end wall design where the wall contour varies circumferentially around the pipe perimeter. This asymmetric geometry creates differential flow paths that prevent boundary layer buildup and vortex formation, thereby improving aerodynamic performance while maintaining acceptable manufacturing complexity through standardized fabrication methods

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The non-axisymmetric end wall introduces localized geometric variations at specific circumferential positions rather than uniform changes throughout. This local quality modification targets specific flow separation zones and boundary layer development regions, optimizing aerodynamic performance in critical areas without requiring complete redesign of the entire diffuser pipe structure

Inventive Principle:

Principle #3Local quality

2Device complexity

If diffuser pipes use standard uniform geometry, then design and fabrication are straightforward, but flow uniformity at exit deteriorates due to boundary layer accumulation

Engineering Contradiction:

Improvediffuser pipe design complexityVSAvoidflow uniformity

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The non-axisymmetric end wall geometry introduces circumferential variations in the diffuser pipe structure that create differential diffusion angles across different radial positions. This asymmetric design promotes more uniform flow distribution at the exit by preventing localized boundary layer dominance, achieving improved flow stability without excessive design complexity

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The end wall contour incorporates curved surfaces with varying radii of curvature around the circumferential direction. These curved geometries guide the flow more effectively through the diffuser passage, reducing flow separation and promoting uniform exit flow conditions while maintaining smooth surfaces that are feasible to manufacture

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If diffuser pipes are extended in length to improve diffusion, then aerodynamic performance improves, but pipe length and system size increase

Engineering Contradiction:

Improveaerodynamic performanceVSAvoiddiffuser pipe length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The non-axisymmetric end wall design creates optimized local flow paths that enhance diffusion efficiency within a compact length. By varying the wall contour circumferentially, the design achieves better aerodynamic performance without requiring extended pipe length, as the asymmetric geometry promotes more effective kinetic energy to pressure energy conversion in the available space

Inventive Principle:

Principle #4Asymmetry

4Use of energy by moving object

If diffuser pipes operate at high diffusion angles to improve pressure recovery, then energy conversion improves, but flow separation and vortex formation increase

Engineering Contradiction:

Improvekinetic to pressure energy conversionVSAvoidvortex formation

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The non-axisymmetric end wall creates local variations in diffusion angle around the circumferential direction. By adjusting the wall contour at specific locations, the design optimizes pressure recovery in regions prone to flow separation while maintaining lower diffusion angles in vulnerable areas, thereby reducing vortex formation and improving overall energy conversion efficiency

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10823195B2Diffuser pipe with non-axisymmetric end wall

Publication Date: 2020.11.03 PRATT & WHITNEY CANADA CORP

AI summary

A compressor diffuser for a gas turbine engine comprises a plurality of diffuser pipes having a tubular body. The pipes have a first portion having a radial component and defining a throat at a location along the first portion, a second portion having an axial component, and a curved portion fluidly linking the first portion and the second portion. The first portion has an inner surface with a local surface contour located between the throat and the curved portion. The local surface contour extends along a portion of and around less than an entire perimeter of the first portion.