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Thermal barrier coatings (TBC) are perceived as enabling technology to increase low heat rejection (LHR) diesel engine performance and improve its longevity. The state of the art of thermal barrier coating is the plasma spray zirconia. In addition, other material systems have been investigated for the next generation of thermal barrier coatings. The purpose of this TBC program is to focus on developing binder systems with low thermal conductivity materials to improve the coating durability under high load and temperature cyclical conditions encountered in the real engine. Research and development (R&D) and analysis were conducted on aluminum alloy piston for high output turbocharged diesel engine coated with TBC.

The purpose of this paper is to investigate combustion and performance characteristics for an advanced class of diesel engines which support future Army ground propulsion requirements of improved thermal efficiency, reduced system size and weight, and enhanced mobility. Advanced ground vehicle engine research represents a critical building block for future Army vehicles. Unique technology driven engines are essential to the development of compact, high-power density ground propulsion systems. Through an in-house analysis of technical opportunities in the vehicle ground propulsion area, a number of dramatic payoffs have been identified as being achievable. These payoffs require significant advances in various areas such as: optimized combustion, heat release phasing, and fluid flow/fuel spray interaction. These areas have been analyzed in a fundamental manner relative to conventional and low heat rejection “adiabatic” engines.

Significant headway has recently been achieved in advanced high-temperature component design. Progress has been made in selecting a highly effective thermal insulating design composed of a titanium alloy piston with 1.0 mm thermal barrier coating which provides the same level of insulating effectiveness as a ductile iron piston with 2.5 mm coating. The low thermal conductivity of Titanium Alloy 6242 inherently provides a significant level of thermal resistance which effectively reduces the required coating thickness, reduces thermal stresses, and nearly eliminates coating thermal expansion mismatch. Other benefits of the titanium alloy piston include low weight and increased high temperature strength. Thermal rig testing has been completed on several plasma-sprayed zirconia coatings and a critical durability threshold thickness of 1.25 mm has been identified. In addition, zirconia coatings and chrome-oxide-densified Eirconia coatings have been screened in a small bore diesel engine.

The development of a practical, reliable, and durable adiabatic engine which will meet all advanced military requirements is still hindered because of available insulating materials and design limitations. The high temperatures and thermal gradients which are associated with a highly insulated low heat rejection engine create monumental challenges to engine designers. Over the past 12 years a wealth of information and experience has been generated. Numerous approaches to insulate the combustion chamber have been explored but none are known to simultaneously meet heat rejection, durability, and performance requirements. This paper will present the first year's results and the future plans of an adiabatic engine component technology development program for high output military engines, sponsored by the U.S. Army Tank-Automotive Command Center.