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A spherical joint piston and connecting rod have been developed through design proof-of-concept. The spherical joint allows piston rotation. The benefits of a rotating, symmetrical piston are: mechanical and thermal load symmetry, improved ring sealing and lubrication, and reduced bearing loads, scuffing, clearances and oil consumption. The assembly includes a squeeze cast, fiber reinforced aluminum spherical joint piston. Reinforcement is located in the piston bowl and skirt. The connecting rod consists of a spherical small end positioned on an elliptical cross-sectioned shank blended into a conventional big end. The assembly has operated at cylinder pressures exceeding of 24 MPa.

Three different piston designs were fitted to a turbo-charged, intercooled diesel engine with cylinder diameter of 130 mm as follows: standard aluminum piston with casting gallery articulated piston with steel crown and aluminum skirt nodular cast iron piston with shrink fit ceramic section. The temperature distribution and thermal balance of the piston designs were calculated as a function of mean effective pressure, based on extensive temperature measurements and with the help of the Finite Element Method. The heat flowing into the piston affects the engine oil, the cylinder, the rings and the piston pin. The significantly varying heat flows are quoted as a function of mean pressure for each piston design. The heat balance of articulated pistons with and without sprayed on ceramic coatings and their thermal deformations are compared.