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Mixed-flow impeller pumps up efficiency 1415

DN Staff

February 26, 2001

5 Min Read
Mixed-flow impeller pumps up efficiency

Escanaba, MI -Thermal efficiency influences the overall output, fuel economy, and life of an engine. However, cooling system technology hasn't kept pace with engine developments and advances in electronic controls. After all, compared to the latest emissions-driven diesel, automotive, hybrid, and fuel cell engine development, melting-wax based thermostats and pulley-driven water pumps have hardly changed. So before water pump supplier Engineered Machined Products Inc. set about its latest pump design, the engineering team reconsidered every aspect of conventionally driven water pumps. Overlooking 50 years worth of industry preconceptions, they focused instead on improving pump efficiency, flow control, and warrantee issues. The result is an entirely new class of water pump called the E.M.P. Advanced Electric Pump.

The pump and controls thermally optimize the engine for a 3-7% increase in fuel economy. It also reduces emissions, and cools the enginer components after shutdown to decrease thermal fatigue.

The patented, fully controllable water pump uses a proprietary mixed-flow impeller and diffuser design that improves fluid pumping efficiency. An integral, liquid-cooled electric drive motor provides flow control independent of engine speed. Moreover, the design has no external mechanical seals that currently account for approximately 95% of pump warranty claims.

Volute vs. diffuser. To decrease turbulence in fluid exiting the pump, most water pumps use a volute, or spiral-scroll-shaped form machined at the edge of the impeller. However, fluid coming off the impeller bombards fluid in the volute and actually decreases fluid pumping efficiency, according to E.M.P. VP of Product Development David Allen.

Instead, the Advanced Electric Pump uses a diffuser that immediately redirects fluid as it comes off the impeller into a stationary set of vanes, isolating it from impeller interference. "This boosts efficiency because the diffuser collects fluid from the impeller for a full 360 degrees as compared to approximately 90 degrees of a volute style pump," Allen explains.

The drive mechanism in the new pump is designed to use either an integral switched reluctance or brushless permanent magnet motor. Because the rotor attaches directly to the impeller, there are no external drive mechanisms such as pulleys or gears, and the pump can generate the appropriate coolant flow rate, depending on engine temperature rather than engine speed.

Conventional pumps restrict system design and repair since the location of the drive mechanism and required volute determines placement on the engine, according to E.M.P. President Brian Larche. "This makes it difficult to redesign the pump, and it means more labor to replace the pump," Larche says. And with many existing engine applications, it means large parts inventories with literally hundreds of conventional water pump designs.

In contrast, the E.M.P. pump doesn't need a whole lot of plumbing. The design mounts anywhere in the engine compartment. Its in-line design eliminates the need for custom-built pumps, and means decreased pump inventory for both military and commercial applications. Simple connections make field replacement fast and easy. In fact, E.M.P. is working to develop electric pumps with two quick hose disconnects, an electrical connector, and a coolant shut-off valve for the military.

The pump's hybrid design blends characteristics of both centrifugal and axial flow pumps.

No external leakage.

Water pumps are generally in the top 10 warrantee items, explains Larche. And typically they're in the top three because of seal failures. "In fact, conventional pumps are designed to leak. That's why they include a weep collection pocket and external leak paths," says Larche. In contrast, the Advanced Electric Pump requires no external mechanical seals and is designed to eliminate external leak paths. Moreover, elimination of side loads induced by belts or gears extends bearing life and creates a favorable environment for seals; they are no longer subject to shaft deflections associated with drive mechanism loading. So the motor-driven pump uses smaller, less expensive bearings than traditional pumps.

"With the impeller matched to a highly efficient flow-through diffuser, it reduces parasitic power consumption, increases engine life, and saves the operator money," says Larche. In fact, analytical models indicate application control strategies can reduce the energy draw on the engine by several horsepower and decrease fan run time by greater than 50%. Based on this analysis, the pump has the potential, according to Allen, to achieve fuel savings of over $5 billion per year in the U.S. alone in over-the-road vehicle service.

Additional details

Contact: Paul Harvey, Engineered Machined Products Inc., 2701 N. 30thSt., Escanaba, MI 49829; Tel: (906) 789-7497; Fax: (906) 789-7825; E-mail: [email protected].

Typical Applications

Over-the-road and off-highway engine coolant pumps

Oil pumping systems

Process pumping applications

David Allen

Vice President of Product Development David Allen has been with Engineered Machined Products, Inc. since 1994. He currently oversees all research & development activities for both conventional and advanced programs. He has designed more than twenty engine pumps, many of which are currently being used on OEM diesel engines. He helped design other engine components currently in production in the areas of high-pressure manifolds, oil pumps, and oil management systems, and holds three patents on various pumping devices for coolant, oil, and air pumping systems, with several additional patents pending. Under David's watch, EMP has grown from 5% of the U.S. conventional diesel pump market to a 60% market share, while placing a focus on developing innovative advanced products in fluids and oil management that have worldwide application.

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