The effect of friction on the performance of an air standard dual cycle

An irreversible air standard Dual cycle model is proposed in this paper. The finite-time evolution of the cycle's compression and power stroke is taken into account and its global losses lumped in a friction-like term is also considered. The analytical formulas of power output versus compression ratio and efficiency versus compression ratio of the cycle are derived. They are generalized formulas for internal combustion engines because they include the performance characteristic of special cases of Diesel and Otto engines. The effects of various design parameters on the performance of the cycle are demonstrated by one numerical example. The model leads to loop-shaped power-versus-efficiency curve as is common to almost all real heat engines.