The following parts of the diesel engine hot-section provide insulation advantages with thermal barrier coatings of the stabilized zirconia type:

o piston o exhaust valves o cylinder head (firedeck) o exhaust port* o inlet air passage* o exhaust gas passage inlet to turbocharger o cylinder liner from tcp ring reversal point to head

* Major effort with cast-in-place inserts-principally aluminum titanate Related to discussions with J. Fairbanks, the following conclusions can be drawn 6):

These coatings should be engineered to the components. Thickness should be determined analytically for specific engines. Injection parameters should be adjusted for the higher temperatures. Turbochargers should be rematched for the higher energy levels resulting from insulation. Variable geometry turbochargers appear better suited to the wider range of energy levels. Turbocompounding should be considered. Other waste heat utilization schemes are in development, but have high capital costs, are complex, and increase maintenance reguirements. Hcwever, higher fuel costs could make seme of these systems cost-effective.

Tests should be made in a multi-cylinder engine because transient conditions in the cylinder will be affected by the coatings. The coatings should be partially stabilized zirconia with surface treatment. The engine should be adjusted to the changed working conditions. Compression, injection parameters, and turbocharger should be adjusted to maintain the specified maximum cylinder pressure, and optimize the fuel consumption.

•The possibilities for better combustion of low grade heavy fuel are particularly important in such a research effort. The fact that ceramic coatings have been able to reduce the specific fuel consumption and increase the energy content of the combustion gases gives indications of the possibility of reducing operational costs to more than compensate for coating costs. As an additional advantage there are the already documented reductions of thermal

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