New Water Pump Design Highlights Emerging Trends In Cooling Systems Technology

While today's advanced diesel engines incorporate a range of high technology components and systems, some haven't changed significantly for decades. An example of this is water pumps, most of which still employ the familiar gear driven impeller technology that has been used for more than 50 years.

 

However one water pump manufacturer, looking to dramatically enhance water pump technology for modern, emissions driven diesel engines, has developed a patented, controllable water pump for engine applications including primary, secondary and component-based cooling systems. The new design by Engineered Machined Products (EMP) is engineered to provide the advantage of controllable flow via a self-contained electric motor and the elimination of external mechanical seals. This technology is aimed at diesel, automotive and military engine applications, including future powertrains such as hybrids and fuel cells.

 

EMP is a major domestic supplier of cooling water pumps for the diesel engine industry and prominent in the development and advancement of pumps and pumping technologies. The company currently serves diesel manufacturers with engines from 175 bhp to over 2000 bhp used in both on- and off-highway vehicles, as well as commercial, industrial, agricultural, construction and power generation equipment.

 

Established in 1981 and under present ownership since 1991, EMP is a privately held company with its corporate headquarters, including research & development, machining and manufacturing operations, in Escanaba, Mich. It also operates an assembly/inventory management facility in Greenfield, Ind. In 1999, EMP had sales of $84 million, and estimated sales for 2000 are $122 million.

 

According to EMP, today's coolant pumps are based on technology that is well over 50 years old. The improvements made in the last few years have not solved the basic problems and conventional coolant pumps often continue to be one of the early components to fail on an engine. Also, although engine design and requirements have changed, the coolant pump and coolant systems have generally not kept pace with the changes.

 

Conventional water pumps utilize centrifugal impellers, which are relatively inefficient and not a good choice for typical diesel engine applications. They are designed to produce relatively high pressure, which is typically not required. The drive mechanism for conventional pumps is either a pulley or gear linked directly to the crankshaft.

 

These types of drives can generate a considerable amount of side loading on the pump, which can decrease bearing life. Since the drive mechanism is directly connected to the crankshaft, the rate of flow out of the pump is proportional to engine RPM. But thermal cooling requirements of an engine are not always related simply to engine speed. They can be significantly affected by a range of other factors, including vehicle velocity, ambient temperature, vehicle loading, etc.

 

Excess coolant flow not only wastes energy, but overcooling can also cause combustion to occur at lower than optimal temperatures, which can negatively impact both fuel economy and emissions.

 

Traditional mechanical seals used on today's conventional pumps utilize a dual-face ceramic or carbide-based material. These can be prone to external leakage, which is a common cause for premature pump repair and replacement. Conventional pumps also restrict system design since the location of the drive mechanism and required volute determines placement on the engine.

 

Limited placement options often make it difficult to redesign the pump when design changes to the engine require more coolant flow. Because of the many existing engine applications, there are literally hundreds of conventional water pump designs, creating a need for large parts inventories.

 

Finally, today's conventional coolant system is mechanically controlled via a melting wax-based thermostat. This restricter valve type of control is inefficient and cannot be ideally integrated with the modern day onboard computer controls.

 

This makes it difficult for the cooling system to respond properly to environmental or operator changes and restricts modern predictive maintenance possibilities.

 

The EMP advanced pump concept was conceived to overcome the issues of conventional pumps and allow for improved flexibility in design, performance and support of future engine requirements. The pump is mechanically simple, and thus very robust.

 

The pump incorporates a nontraditional impeller, which is designed to meet the high flow and low pressure requirements of typical engines. This hybrid impeller will utilize a highly efficient flow-through diffuser instead of the currently required volute, resulting in a flexible design which can be easily adapted to existing engines by allowing for various mounting locations.

 

The drive mechanism utilizes an advanced switched reluctance motor. The motor selected, EMP said, is simple, cost effective and reliable since it requires no magnets. The rotor is directly attached to the impeller, eliminating the need for external drive mechanisms such as pulleys or gears. The diffuser efficiently collects fluid from the impeller for a full 360[degrees] as compared to the approximately 90[degrees] of a volute style pump. The benefit of this design, the company said, is that it eliminates side loading and allows the use of either bearings or simple bushings. The result is a low cost product with smooth, efficient rotation and the potential of good durability.

 

Since the drive mechanism rotor is independent of the engine, the pump can generate the appropriate flow rate regardless of engine rpm, allowing the coolant flow to be adjusted as the engine temperature varies. It is, therefore, a smart pump that utilizes sophisticated computer control logic by allowing for precise control of coolant flow and providing coolant system feedback, which warns the operator of any problems developing in the coolant system.

 

The combination of computer control and sensor feedback can also compensate for differences in operator driving tendencies and various environmental changes, which can negatively impact engine operating temperatures.

 

The final technical hurdle involves defining cooling system needs in order to achieve optimal thermal management. To maximize the benefits derived from a controllable pump, a coolant system control system is required to signal the pump to vary output as changes in engine temperature occur. Changes in operating conditions, including vehicle load, ambient temperature, vehicle velocity, and many others, have a significant impact on engine temperature and performance. EMP's advanced pump, coupled with an integrated coolant system, is designed to be capable of sustaining optimal engine temperature regardless of external factors.

 

EMP said it has successfully completed the proof-of-concept phase. Early testing has confirmed the advanced controllable electric pump can improve cooling pump efficiency by more than 30 percent, while decreasing weight by as much as 60 percent and reducing envelope requirements by 50 percent. These findings, the company said, are based on comparative testing and analysis between a truck water pump and the EMP advanced controllable electric pump under identical conditions.

 

The company has also sponsored university research to develop control algorithms for regulating pump output to optimize thermal characteristics. Preliminary analysis also indicates the ability to reduce cooling fan on-time by as much as 50 percent due to greater flow at low engine speed. The next phase is to select an engine family for development and testing of a pilot version, which will be installed on field test engines, to verify the results of the initial lab tests and simulations.

 

The controllable water pump is just one of the development programs underway at EMP. Additional development programs cover such technologies as oil level and quality sensors, oil management systems, advanced oil filtration systems and a family of controllable pumps for several engine applications including air, fuel and oils.

 

Much of the development work is being done at EMP's new dedicated R&D and Advanced Products Technology Center in Escanaba. That site, along with EMP's existing design and manufacturing capabilities -- which include 3D solid modeling, finite element analysis (FEA), computational fluid dynamics (CFD), rapid prototyping, CNC prototyping, an advanced DTM Machine, and MathCAD/ Matlab development tools -- allows the company to accommodate its customers' requirements for accelerated component design and shorter development lead times.

 

"Rapid development has become an everyday approach to meeting the demands of our customers," said David Allen, EMP's vice president for product development engineering. "Our engineers have defined rapid development to be the integration of computer driven tools to deliver a superior product to the customer, priced competitively, in a compressed timeframe."