Insulated Engine Experiments

The insulated version of the engine used plasma sprayed zirconia coatings 0.050" thick on the piston top and on the head firedeck, and 0.030" thick on the valves. The heat flux measurements were made using a ceramic probe which had 0.050" thick coating of plasma sprayed zirconia on the top of which thin films of platinum and platinum/rhodium were deposited by NASA Lewis Research Center to form a fast response thermocouple.

The ceramic coatings installed in the engine and on the heat flux probe produced high surface temperatures, increasing sharply with the engine load (Figure 6). At the light loads of the test matrix the temperatures are a little over 600K, but at mid-load points this rises to 940K, which is the highest point at which the probe performed reliably. The highest cyclic surface temperatures are larger than the time mean, and this is illustrated by the bar labeled "swing," denoting the smallest and highest cyclic temperature at one of the data points.

The measured wall temperature "swings" (maximum-minimum cyclic temperatures) are shown in Figure 7.

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