Scuderi Split Cycle Fast Acting Valvetrain: Architecture and Development 2011-01-0404
The Scuderi internal combustion engine is characterized by a split cycle that divides the four strokes of a conventional combustion cycle over two paired cylinders, one intake/compression cylinder and one power/exhaust cylinder, connected by a crossover port. This split cycle also has an additional high pressure “crossover” gas transfer phase versus the conventional 4-stroke cycle, during which the charge air is moved from the first to the second cylinder. The intake/compression, power/exhaust and crossover events are repeated every revolution, i.e. over two cycles, with a small phase angle between the two cylinders. The separate cylinders enable opportunities for improved combustion and the possibility for pneumatic hybridization of the engine. This paper describes the technical challenges posed by the actuation of the crossover valves in the Scuderi Split Cycle research engine. Fast actuation of these valves is a key requirement for successful combustion and for hybrid operation in the Scuderi and perhaps other pneumatic hybrid engines where the mass of air entering the cylinder is controlled by the operation of poppet valves. To successfully meet these demands design modeling, dynamic simulations of the valve opening event, and structural analysis on the components were performed concurrently. Experimental rig work was undertaken to verify the valvetrain performance and durability. The result is a valvetrain with an unusual architecture that meets the speed of actuation requirements for successful engine operation. The structural limitations in terms of mass, strength and stiffness of the major components are fully understood, as well as the dynamic behavior of the whole system. A set of verified analytical models was developed which will be used to tailor valvetrain design and performance as various Scuderi engine configurations are developed in the future.