Designing Analysis into the Product

By Bob Cramblitt

Mention “energy conservation” to makers of industrial pumps and the words will either strike fear or spell opportunity.

Finish Thompson is an Erie, PA-based designer and manufacturer of chemical process, drum, and barrel pumps firmly in the opportunity camp. The company recently used CFdesign upfront CFD software to double the efficiency of its new line of DB series magnetic drive pumps, possibly saving customers thousands of kilowatt-hours per year on electric bills. Within Finish Thompson, using upfront CFD reduced product development time for the DB series by an estimated 33 percent, and cut testing time from months to weeks.

New Path to Efficiency

Efficiency has always been the key market differentiator for Finish Thompson. In the past, arriving at the most efficient design meant waves of physical testing in an effort to maximize flow rate and differential pressure while minimizing input power. In the end, there was always the feeling that if only designers could see what was going on inside the pump, there could have been greater efficiency gains.

   

CFdesign

> > Engineers used CFdesign to study design alterations of a pump housing,  adjusting vane angles, widths, and thicknesses; changing the impeller diameter; and more, accomplishing in six weeks what would have taken six months on a flow bench. 

Plans to redesign the DB series led Finish Thompson Engineering Manager Dan Roll and Design Engineer Chad Best on a search to find a way to incorporate CFD into their product development process.

Neither Roll nor Best had CFD experience, or the desire to become specialists in the area. Their roles were clear: to design and engineer great products. Hiring a CFD specialist and buying specialized software that worked outside of their proven CAD processes was also not an option.

Finish Thompson needed “a tool to make a product,” according to Roll. He didn’t want to take on a whole new discipline that would add more layers of complexity to the design process.

After intense evaluation of three or four product providers, Roll and Best decided on CFdesign software from Blue Ridge Numerics.

CFdesign differs from traditional CFD systems in that it works directly with the native geometry of the CAD software used to create the product model. This eliminates the time-consuming process of translating CAD geometry to fit the parameters of the CFD software. In this case, engineers gained insight into pump performance early in the product design process, cutting development time and substantially reducing the amount of physical prototyping and testing required.

Getting the Model Right

The first step for Finish Thompson was arriving at a model that would meet its needs and maximize the benefits of CFdesign. Best, who started by running simulations of existing products created in SolidWorks, found that he could reduce computing time by eliminating parts of the model that he felt were not critical for efficiency testing.

   

CFdesign

< < CFdesign provides an “interactive window” into the DB series pump housing to see details of flow separation at the cutwater and volute, enabling immediate optimization of the pump beyond what would have been possible in the lab.

“We found that the simplified models gave us similar results to the full models, but were much faster to run and much easier to set up,” says Best. Most importantly, the CFdesign results for existing products matched those from physical lab tests.

Armed with this information, Roll and Best compiled a list of design parameters for the new DB series pump. An impeller and housing were designed in SolidWorks. Small clearances and non-essential geometry were removed to provide a model that was still accurate for the results the design team wanted to achieve, but would run much faster than a fully detailed model.

The initial design was brought into CFdesign, tested, and evaluated based on the team’s desired results. Using pressure and both relative and absolute velocity results, Roll and Best evaluated vane angles of the impeller, both at the entrance and exit, as well as the diffusion in the discharge of the pump. They also evaluated different numbers of vanes and the meridian profile – flow measurements taken parallel to a line of longitude – of the impeller. They checked for separation of the fluid from the vane and any turbulent flow areas that would reduce the pump’s performance.

   

Finish Thompson

> > Finish Thompson used CFdesign upfront CFD software to double the efficiency of its new DB series magnetic drive pumps.

“One of the most significant benefits of this simulation,” says Best, “was being able to change vane angles and see how they interacted with the fluid in both the eye of the impeller and the impeller exit at various flows. This is difficult to see during physical testing.”

From 6 Months to 6 Weeks

Based on results from simulations, Roll and Best made alterations such as adjusting vane angles, width and thickness; changing the impeller diameter; and manipulating the housing diffusion angle. After changing one item, they reevaluated results and compared them with previous runs. A new simulation could be generated in about 24 hours, as opposed to the three or four days it took previously to make an adjustment to a physical prototype and run new tests.

Best estimates that Finish Thompson ran approximately 20 simulations between the DB11 and DB15 series before he and Roll felt confident with the design for each model. It would have taken at least twice as many physical tests to come close to these results, according to Roll, and even then the results would not be as reliable, since design engineers would be unable to visualize exactly what was happening inside the pump.

   

Finish Thompson

< < In the process of improving the pump’s efficiency using Upfront CFD, engineers reduced total development time on the project by 33 percent.

“We were able to do in six weeks using CFdesign what would have taken about six months to do in the lab for the equivalent amount of testing,” says Roll. “We were also able to do a much better job of optimizing our design than we would have been able to do with physical testing. Being able to view the flow within the impeller let us change the vane angles and make other alterations that would have been very difficult to decide upon based on lab results.”

After arriving at the final designs within CFdesign, Finish Thompson developed part drawings and made manufacturing molds for the new DB series. The first sample parts from the molds were tested and showed performance gains of six to 10 percent higher than the CFdesign results had predicted.

“We were very pleased with these results,” says Roll, “and confident to move ahead with production.”

Doing More, Better & Faster

While customers are already benefiting from double the efficiency – 35 to 70 percent – in the DB series, Finish Thompson is reaping the rewards of being able to test many more design elements about three times as fast as within a lab environment.
“We estimate that we cut about six months off our total product development cycle,” says Roll, “from a year-and-a-half to a year.”

After implementing upfront CFD for the first time, Finish Thompson sees a wealth of future possibilities. The company is rapidly expanding its DB series and also plans to introduce a self-priming pump that customers are already willing to buy.

“We see great potential in using upfront CFD to help us open up new markets and rapidly expand and continuously improve our product lines,” says Roll.

While other companies anticipate customers’ demands for greater energy efficiency with a dread commonly reserved for taxes, Finish Thompson is exhorting the marketplace to “bring it on.”

Bob Cramblitt owns Cramblitt & Company in Cary, NC, and writes about design, engineering, and IT technologies. Send your comments about this article through e-mail by clicking here. Please reference “Finish thompson” in your message.

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CFdesign
Blue Ridge Numerics
Charlottesville, VA

Finish Thompson, Inc.
Erie PA