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Internal combustion engines are complex machines that constitute an object of design, and in which diverse processes and variables encounter. In the industrial field, the design of a new engine begins with the conception of a wellestablished solution with consideration on the experience of the designers. To perform the structural design of an engine, it is needed to determine the forces and moments acting on its components, derived from the processes along the cycles of work, with observation of the variations of the pressures and the temperatures in the cylinder and of the forces and moments of inertia in the components of the mechanisms and the structure. It is the purpose of the present paper to introduce the development of a series of procedures to obtain the preliminary dimensions of the main components of an engine (power mechanism, engine block and cylinder head dimensions), applying the machine design fundamentals and the thermodynamic and dynamic characterization of a generic engine of combustion, using the minimum information (power, torque, engine speed, and conditions of exploitation). To systematize the engine preliminary design, a spreadsheet based on Microsoft Excel was developed. To use this spreadsheet, the user must specify composition of the fuel, the type of ignition, and the wished characteristics of the engine. The outputs of the spreadsheet are the global stoichiometric balance of fuel-air chemical reactions, the heat release rate, the indicator diagram, the forces and moments acting on the main components of the crank-train mechanism, such a valuable information required to conduct the dimensioning of the engine components making use of the fundamentals of strength of materials. [ABSTRACT FROM AUTHOR]

Expanded cycles, like the one developed by Atkinson for internal combustion engines (ICM), are used to make better use of fuel and increase thermal efficiency. In this paper, the Watt's and Stephenson's kinematic structures is presented from the point of view of the mechanics of machinery and graphs theory, which by means of multi-link arrangements, allow recreating the mechanism presented by James Atkinson. By applying a kinematical analysis to these kinematic structures, the problems related to the piston speeds and accelerations that prevent the massive introduction of the "classical Atkinson cycle" in automotive engines are revealed. Despite this fact, the Atkinson cycle is highlighted in this work as a real promising constructive technology, given the advances in electronic hardware and control technologies. [ABSTRACT FROM AUTHOR]