Passive Storage and Release of Waste Heat to Improve Cold Starting Performance of Diesels (310)

The viscosity of oil increases dramatically with decreases in temperature, which results in increased frictional resistance during starting of automotive engines in cold weather.  The increased frictional drag is especially important when starting diesel engines because of the high minimum cranking speed required for starting.  The increased resistance can prevent engine starting. The problem is severe enough that a common practice is to continuously idle diesel engines in cold weather, resulting in wasted fuel, increased maintenance problems, and increased pollution.

The University of Dayton Research Institute has developed a means to use the waste heat produced by the engine to improve the starting characteristics of diesel engines exposed to cold weather overnight. The approach is a passive thermal management system that maintains the oil temperature at a level high enough to insure engine starting after sitting out in the cold overnight. A proof of concept thermal management system composed of passive energy storage devices (ESD) was designed and tested on a large diesel truck.

Tests of the vehicle over the last winter demonstrated that the thermal management system maintained the oil temperature above 50°F for longer than 12 hrs when exposed to average ambient temperatures as low as 13°F (the lowest overnight average air temperature during the tests). The higher oil temperature resulted in faster starting and less cranking energy required from the batteries. The successful concept demonstration shows that a diesel engine equipped with passive energy storage devices can be shut off for longer periods in cold weather and still reliably start.  The application of ESD systems to diesel engines could reduce or eliminate fuel use and engine wear due to overnight idling in cold weather.

While the primary interest is improved starting, a secondary benefit is the improved oil flow for lubrication of engine parts at startup, which can reduce engine wear.

For more information, please contact the Office for Technology Partnerships at 937-229-3515.

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