Design Optimization of a Diffuser Pump Stage

Introduction

Design Targets

Investigate detailed flow structure and loss mechanism in a diffuser pump and redesign the impeller and diffuser blade to reduce losses and improve stage efficiency.

Deliverables

Redesigned geometry of the impeller and diffuser.

Impact

Based on unsteady flow predictions the redesigned stage showed up to 4 points improvement in efficiency.

In this project the client asked ADT to perform a hydrodynamic design optimization of a strongly interacting diffuser pump stage using the inverse design code TURBOdesign1. The focus of the design was to minimize the hydrodynamic loss generation particularly in the diffuser channels. Figure 1 shows the pump diffuser arrangement.

Flow details comparison show an optimised flow field in the diffuser.

The project was divided into several tasks. Initially a detailed flow analysis of the existing pump diffuser was performed. Due to strong interaction between the impeller and the diffuser blade rows, ADT performed a full stage unsteady flow analysis in order to understand the flow structure and loss generation mechanism in the machine. Based on the analysis study, it was found that the majority of loss generation occurred in the diffuser channel. A redesign of the impeller blades was performed using TURBOdesign1 in order to minimize the secondary flow losses in the impeller and reach a more uniform flow condition at the impeller exit and diffuser inlet. Unsteady flow analysis confirmed that the new impeller had a higher efficiency and also resulted in more circumferentially and axially uniform exit flow distribution.

Streamline plots of the conventional diffuser showing a separation bubble

The diffuser redesign was followed by prescribing a modified thickness and loading distribution in the inverse design code TURBOdesign1 so that an optimised flow in the diffuser channel was obtained. Unsteady flow analysis in the pump stage was then performed using the redesigned impeller and diffuser blades.

Streamline plots of stage designed by TURBOdesign1

The results showed up to 4 points improvement in stage efficiency was obtained in the redesign configuration. Flow details comparison show an optimised flow field in the diffuser, see Fig. 2 and 3.

Design Optimization of a Diffuser Pump Stage

Introduction

Flow details comparison show an optimised flow field in the diffuser.

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