Page 267 - The Mechatronics Handbook

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FIGURE 12.8 Thermal efficiency of the cold air-standard Otto and Diesel cycles, k = 1.4.

As all processes are internally reversible, areas on the p-v and T-s diagrams of Table 12.7 can be
interpreted, respectively, as work and heat transfer. Invoking Eq. (12.23) and referring to the p-v diagrams,
the areas under process 3-4 of the Otto cycle, process 2-3-4 of the Diesel cycle, and process x-3-4 of the
Dual cycle represent the work done by the gas during the power stroke, per unit of mass. For each cycle,
the area under the isentropic process 1-2 represents the work done on the gas during the compression
stroke, per unit of mass. The enclosed area of each cycle represents the net work done per unit mass.
With Eq. (12.25) and referring to the T-s diagrams, the areas under process 2-3 of the Otto and Diesel
cycles and under process 2-x-3 of the Dual cycle represent the heat added per unit of mass. For each
cycle, the area under the process 4-1 represents the heat rejected per unit of mass. The enclosed area of
each cycle represents the net heat added, which equals the net work done, each per unit of mass.

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