CFD Online Logo CFD Online URL
Home > CFD News and Announcements > Message Display

CFD News and Announcements - Message DisplayCFD-Wiki

Post Response | Return to Index | Read Prev Msg | Read Next Msg

Pump Design for Reduced Costs & Improved Efficiency

Posted By: Darshan Patel
Date:Thu, 17 Nov 2016, 11:43 a.m.

A 3-D inverse design method provides better cavitation control and reduces manufacturing costs

Cost reduction is a driving force in pump design. The manufacturing cost of centrifugal and mixed pumps generally varies with the volume of the pump. To reduce manufacturing costs, the pump diameter must be reduced for a given head which results in an increase in head coefficient. Generally, an increase in head coefficient can lead to a reduction in efficiency and suction performance. The effect on suction performance in particular can be significant and is one of the limiting factors in the reduction of pump volume and, therefore, manufacturing costs. As a result, a key factor in the development of compact, mixed-flow and centrifugal pump stages is better control of cavitation.

Traditionally, mixed-flow and centrifugal pumps are designed based on empiricism and a trial and error approach, in which the impeller and diffuser geometry are modified manually by changes to the blade angle distribution. The flow through the pump stage is then computed by using 3-D computational fluid dynamics (CFD) code to evaluate the performance of the pump stage. The designer must rely on trial and error to make changes to the geometry to improve the performance of the stage.

However, a trial and error process restricts designers to a relatively small part of the design space, limiting them to blade angle distributions that have worked in the past. In addition, the process does not allow for the easy exploitation of a wide part of the design space to meet the contrasting requirements on efficiency and suction performance.

3-D Inverse Design

An alternative approach to the design of the pump stage is to use an inverse method. With this approach, the impeller or diffuser geometry is designed for a specified pressure distribution or blade loading. Since the viscous losses and cavitation behaviour in the pump is to a large extent controlled by the 3-D pressure distribution, a designer can obtain more direct control over the design process by using this method.

Cavitation Control

A 3-D inverse design method has been used extensively for the control of pump cavitation. For example, it was used for the design of a high specific speed, mixed-flow pump stage to improve stage efficiency and reduce cavitation. By using the 3-D inverse design method, significant improvement of stage performance was possible, and cavitation was simultaneously suppressed at design operating conditions.

The flow in impellers was predicted by a two-phase CFD analysis. The blue region is non-cavitating, and the green and red represent regions of the high void fraction. Cavitation has been well suppressed in the inverse designed impeller with almost the entire blade surface being cavitation free.

Volume Control

In another application, a 3-D inverse design method was used to reduce the volume of a medium specific speed, mixed-flow pump stage to 39% of a conventionally designed stage (see Figure 2). Test data confirmed that the redesigned stage can provide the same head, efficiency and suction performance at design point as the conventional stage with a 61% reduction in the volume of the stage. The code has also been used by the Japanese space agency, JAXA, to develop a compact design of a rocket pump.

Waterjet Design

In addition, this method has been used for the design of mixed flow and axial pump stages for waterjets used by the U.S. Marine Corps’ EFV Amphibious vehicle by Honeywell, U.S. Navy’s David Taylor Research Center and CDI Marine (see Image1). The main objective was to develop a highly compact design to accommodate space limitation and to reduce entrained water.

Want to learn more about TURBOdesign?


Post Response

Your Name:
Your Email Address:
If you'd like to include a link to another page with your message,
please provide both the URL address and the title of the page:
Optional Link URL:
Optional Link Title:
If you'd like to include an image (picture) with your message,
please provide the URL address of the image file:
Optional Image URL:
If you'd like email notification of responses, please check this box:
Post Response | Return to Index | Read Prev Msg | Read Next Msg
Go to top Go to top