Increasing the combustion temperature in diesel engines is an idea which has been pursued for over 20 years. Increased combusting temperature can increase the power and efficiency of the engine, decrease the specific fuel consumption, CO and (possibly) the NOx emission rate. At the same time, TBCs should protect the metallic substrate against the corrosive attack of fuel contaminants (Na, V, and S). The most common system used is Yittria Partially Stabilized Zirconia (Y-PSZ). However, in diesel engines Y-PSZ TBCs have not met with wide success. To reach the desirable temperature of 850-900°C in the combustion chamber from the current temperature of 350- 400°C, a coating with a thickness of at least 1mm is required. This introduces different considerations than in the case of turbine blade coatings, which are on the order of 100µm thick. The design of a multilayer coating employing relatively low cost materials with complementary thermal properties is described. Numerical models were used to optimize the thickness for the different layers to yield the minimum stress at the operating conditions while achieving the desired temperature gradient. Abstract only; no full-text paper available.

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