Computer simulation helps design more efficient water pumps

US-based Engineered Machined Products specializes in the development and manufacture of cooling pumps for diesel engines. To speed up evaluation and optimization of the performance of new designs and eliminate problems such as cavitation, the company makes extensive use of sophisticated 3D computer simulations.

Computer simulation is helping engineers at Engineered Machined Products, Inc (EMP) of Escanaba, MI, to design more efficient diesel engine water pumps. Using computational fluid dynamics (CFD), they can quickly evaluate the performance of preliminary designs. In particular, potential problems such as cavitation can be avoided early in the design. Cavitation occurs where the local pressure falls below the fluid vapour pressure, causing the formation of vapour bubbles. As the bubbles move through the pump into regions of higher pressure they can collapse, causing noise, vibration and the potential to damage pump components.

EMP engineers use a sophisticated in-house one-dimensional solver to calculate initial 3D design based on the pump’s required performance. Since this 1D solver does not take three-dimensional fluid dynamics into account, it cannot detect cavitation and physical pump testing must validate performance. Before creating a rapid prototype of the pump, engineers use CFD to simulate the design in three dimensions.

The simulation provides a much more thorough performance evaluation as well as crucial diagnostic information that helps the engineer quickly optimize the design. As a result, the company is able to rapidly create innovative designs such as its patented fully controllable water pump. The new design uses a proprietary mixed-flow impeller and diffuser leading to a very efficient design that improves the performance of the pump and can eliminate the mechanical seals that currently account for approximately 95% of  all pump warranty claims. “CFD simulation reduces development time, making it possible to try more alternatives, which helps us improve pump performance and develop unique solutions to existing problems,” said Jeremy Carlson, a product development engineer for EMP.

EMP profile
EMP has transformed itself from a generalist contract manufacturer to North America’s leading producer of engine cooling pumps for diesel engines. The company currently serves diesel engine manufacturers for engines ranging from 175 bhp to over 2000 bhp. These engines are used in both on- and off-highway vehicles as well as commercial, industrial, agricultural, construction and power generation equipment. The company has also expanded its offerings to include lube oil pumps, fuel system components and highly integrated engine front covers including pumps, gears and accessory drives.

Due to accelerated emissions requirements recently imposed on diesel engine OEMs, these companies have dedicated most of their engineering resources to redesigning existing engines in order to meet revised emissions targets. The result of this shift is that engine manufacturers are relying more on suppliers to provide engineering and manufacturing assistance on peripheral components and EMP has accelerated their product development efforts to address these needs. The company’s research and development facility provides a focused and creative environment away from day-to-day manufacturing concerns. The 30 000 ft2 facility includes a water pump development and research lab, lube systems development and testing lab, reliability test facility, electronics development and test lab, and CNC machining and rapid prototyping operations.

Unique engineering process
EMP has developed a unique engineering process that takes advantage of the latest technology to accelerate product development. The company’s design process begins with the use of a sophisticated one-dimensional mathematical solver developed with MATLAB software, which has been created to quickly develop pumps and address specific engineering issues.

Engineers input their customer’s pressure, flow and rotational speed requirements along with secondary inputs that place some constraints on the pump geometry. The model then generates the complete 3D geometry for the pump design based on these parameters in a matter of seconds. While the one-dimensional solver provides dramatic advantages in its ability to quickly generate a preliminary design, it is limited because it cannot predict potential performance problems such as flow re-circulation caused by the separation of the boundary layer from one of the surfaces of the pump. These three-dimensional effects cause losses in total pressure that will reduce efficiency and output.

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