Impeller Side Cavity Pressure Imbalance Reduction

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Solution Overview

Problem

Centrifugal rotary machines face challenges in maintaining rotational balance and efficiency due to circumferential pressure variations and flow distortions, especially when operating away from the best-efficiency point, leading to increased radial forces and vibrations.

Innovation Solution

The introduction of an annular subdividing disc and peripheral annular space in the impeller side cavity, which separates outward flow from inward flow, allowing for free circumferential flow and absorption of transit leakage, thereby normalizing pressure and flow variations before redirection by stationary vanes, improving rotational dynamic stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If stationary vanes are installed in the diffuser to redirect flow, then efficiency is improved and volute size is reduced, but the operating range is narrowed and pressure variations increase

Engineering Contradiction:

ImproveefficiencyVSAvoidoperating range

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The diffuser is segmented into multiple channels by stationary vanes, with each channel containing curved guide vanes that redirect flow. This segmentation allows efficient flow conversion at design point while the curved guide vanes in each segment help equalize pressure distribution, reducing harmful pressure variations and allowing broader operating range

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Curved guide vanes are installed in each diffuser channel to locally redirect flow and equalize pressure distribution. The curved geometry of these guide vanes is specifically designed to redirect flow at appropriate angles while smoothing pressure variations in each local channel, thereby reducing global pressure imbalances and expanding operational flexibility

Inventive Principle:

Principle #3Local quality

2Productivity

If the impeller and diffuser are geometrically matched for BEP, then efficiency is maximized, but pressure variations and flow instabilities increase when operating away from BEP

Engineering Contradiction:

ImproveefficiencyVSAvoidflow stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

Curved guide vanes are installed in the diffuser channels to preliminarily redirect and condition the flow before it reaches the volute. This preliminary flow conditioning action equalizes pressure distribution and reduces flow instabilities in advance, allowing the impeller-diffuser geometric matching to maintain efficiency at BEP while the guide vanes prevent flow instabilities when operating away from BEP

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If circumferential pressure variations are reduced, then rotational balance is improved, but additional components are required in the impeller cavity

Engineering Contradiction:

Improverotational balanceVSAvoidcavity structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

An annular baffle is installed in the impeller cavity to act as an intermediary element that redirects secondary flows and equalizes pressure distribution circumferentially. This single baffle component serves as a mediator between the impeller and diffuser, reducing pressure variations and improving rotational balance without requiring multiple complex components

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration reduces axial and radial vibrations, allowing safe operation beyond the best-efficiency point while maintaining high efficiency and broadening the operating range by smoothing out pressure and flow irregularities.

Implementation Method 1

providing a peripheral annular space... to encourage free circumferential flow... thereby reducing circumferential pressure variations

Methodology Applied

Scientific EffectPressure equalization: Diffusion

Implementation Method 2

redirecting stationary vanes may be located within the annular space between the annular subdividing disc and the housing wall

Methodology Applied

Scientific EffectFlow redirection:

Data Source

PatentUS10746196B2Methods and devices for reducing circumferential pressure imbalances in an impeller side cavity of rotary machines

Publication Date: 2020.08.18 TECHNOLOGY COMMERCIALIZATION CORP

AI summary

An improved rotary machine of the invention may include a rotor with an impeller mounted thereon. A side cavity may be formed between an impeller and the housing. The rotary machine may be further equipped with an annular subdividing disc for segmenting a fluid flow in the cavity into a first fluid flow between the disc and the impeller, and a second fluid flow on the other side of the disc between the disc and the housing. The rotary machine of the invention also features a peripheral annular space formed in the periphery of the housing in the cavity at a location adjacent to a peripheral region of the annular subdividing disc. Importantly, this peripheral annular space is void of restrictions to circumferential fluid flow therein so as to alter the second fluid flow in the cavity in order to reduce pressure variations and flow disturbances along the circumference of the rotary machine. This in turn improves rotational balance of the rotary machine.