TransForum Vol. 3, No. 3

CERAMIC ENGINE COMPONENTS ENDURE OVER THE LONG HAUL

Today's heavy-duty diesel truck engines are typically designed to have a lifetime of one million miles or more. Lightweight, wear- and corrosion-resistant engine components are needed to keep these engines running reliably over the long haul. Somep parts, such as fuel injectors with ceramic components, can last longer and reduce emissions by better controlling the combustion process. However, any ceramic part designed for use in a diesel engine component must be machined precisely and must not have any machining-induced damage that could cause the component to fail.

"As manufacturers advance machining technology to reduce costs and obtain faster removal rates (the time during which the material is shaped by the machining operation), they need to know what kind of damage they're inducing in these ceramic parts by their manufacturing processes," says Bill Ellingson, Senior Mechanical Engineer.

Argonne is working to improve the reliability of ceramic engine components such as fuel injector components (top) and valves (left) by using low-power lasers to detect subsurface damage.

Argonne is developing a patented, cost-effective method to ensure the quality of ceramic engine parts after machining. Researchers are using a low-power laser similar to those installed at grocery store checkout counters. By focusing the laser light onto the part and then carefully studying the way the laser light scatters, Argonne's researchers are demonstrating that they can characterize the amount and location of any damage. They can locate the damaged regions either on or below the surface of ceramic parts, such as valves, and relate the detected damage to changes in the strength of the ceramic material. The strength of the material plays a significant role in determining whether the part will fail.

Funded by the U.S. Department of Energy, Argonne is also collaborating with several major manufacturers involved in developing ceramic materials for use in engine components. In one initiative, Caterpillar Inc. lent its expertise and experience in developing the Argonne damage detection method for a silicon nitride diesel engine valve. The goal of the program is to investigate methods developed by Argonne to detect damage in ceramic valves caused by aggressive machining conditions.

In another effort, Cummins Engine Company has designed a high-pressure fuel injector and the ceramic parts in it. A fuel injector is the "Achilles heel" of a long-haul diesel engine, because if it doesn't operate properly, the combustion pattern is disturbed. This disturbance results in incomplete combustion in the engine and unacceptable emissions.

Recently, Cummins provided a set of test samples with known damage to allow demonstration of Argonne's method. The results of the demonstration will provide the basis for the company to consider testing the Argonne method in a production environment.