Precise diagnosis of performance problems inside diesel engines has often been a difficult trial-and-error process. Diesel engine manufacturers have developed with new ways to measure diesel performance indirectly. RH Lyon has a system called Diesel Engine Unit Condition Evaluator which uses signal-processing techniques to measure vibration signals from within the engine. Caterpillar and Cummins Engine also have developed new diagnostic methods.
Problems with diesel engines that have reciprocating parts have long defied a systematic approach to analysis. Engine phenomena such as combustion pressures, valve seating impacts, and piston vibrations reflect directly on how an engine is performing and would be useful to measure. However, these occur inside an engine block and for the most part are not possible to measure directly with sensors.
As a result, diesel engine manufacturers and diagnostic system vendors are quantifying these phenomena using more indirect techniques. For example, RH Lyon Corporation has developed a system called the Diesel Engine Unit Condition Evaluator (DEUCE), which uses sophisticated signal-processing methods to refine vibration signals that does to refine vibration signals that come from within an engine but are measured from outside the engine block. The result is a signal that is close to that emitted by the source being measured. The DEUCE techniques are being incorporated into an expert diagnostic system currently under development at General Electric's Transportation Systems division, which manufactures diesel engines for its own locomotives. (Bucciarelli, 1988)
Caterpillar Inc. is relying on high-speed acquisition of information on vibration, noise, temperature, and pressure to better understand engine phenomena. And at Cummins Engine Co. (Columbus, Ind.), engineers rely mostly on the use of cylinder cut-out tests and use dynamometers as well as torsional speed-detection units to monitor engine condition.
For signals analysis, these manufacturers use fast Fourier transform techniques. For example, the DEUCE system analyzes vibration.....
