Irreversibility and power cycles

In teaching thermodynamics for engineers, on a basis of a curricular design methodology, we analyze the how and why internal combustion engines perfor m. We introduce the concept irreversibility to analyse the themodynamic cyc les of power, then we consider some irreversibilities by mean of the compre sion and expansion processes efficiency. In particular, we analyze the Otto engine and we establish that both. the temperatures as well as the final p ressures, reached by the irreversible adiabatics, are higher than those rea ched by the reversible adiabatics. With these results, we determine a infer ior bound for the product of the compresion and expansion efficiencies in t he Otto cycle. We also obtain expressions for irreversible work and irrever sible efficiency.