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standard condition and the three coatings. Tests using the 28.8 cetane fuel were completed for all but the 0.100 coating which did not survive long enough to obtain all of the desired low cetane engine test data.

The thermal efficiency tests produced an unexpected result insofar as it was expected that the thermal efficiency of the engine would increase with an increase in coating thickness. The opposite occurred, thermal efficiency decreased as coating thickness increased. The decrease in thermal efficiency was as large as 10 percent for the 0.100 inch coating in comparison to the uncoated components. No explanation for this phenomena is available at this time.

The tests indicate that coated components have a beneficial effect when consuming lower cetane fuels. However, one of the problems associated with consuming low cetane fuels is ignition delay. The lower the cetane rating of a fuel, the longer the ignition delay. Table XIII shows that the coated components reduce ignition delays by 1 to 1.2 crank angle degrees making them comparable to Number 2 fuel in an uncoated engine.

The engine was also instrumented to measure the temperature of the cooling water, exhaust, and lubricating oil. The purpose of these measurements was to evaluate the heat flow patterns resulting from the use of different thicknesses of ceramic coatings.

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