ABSTRACT
Brayton cycle 13. Show that for the same compression ratio, the Brayton and Otto cycles have the
same thermal efciency 14. Understand why the dual cycle was proposed as the prototype for actual internal-
combustion engines 15. Show that the efciency of the ideal dual-cycle engine lies between the efciency
of the Otto and Diesel cycles 16. Understand that regeneration can be applied to internal-combustion cycles with
the possibility of approaching the Carnot cycle efciency, but that the practical realization of this goal is difcult because of the requirements and the complexity of the equipment needed
The power-plant cycles studied in Chapter 8 are known as external-combustion cycles because heat is supplied from a source that is external to the engine and is rejected to a sink that is also external to the engine. The power plants that we use for propelling cars, boats, and so on are commonly known as internal-combustion engines because the release of energy is by combustion within the engine. Mobile power plants have been developed to a high state of reliability and are commonplace in everyday life. Reliability is essentially a term that describes the level of development of the mechanical system. Thus, as the usual occurrence, we expect that a car will start easily and that a trip will be completed without mechanical failure. However, the size, weight, and cost of fuel for a given engine are all functions of the thermal efciency of the unit. It should be noted that external-combustion engines have been studied more extensively in recent times with the aim of reducing air pollution, a problem in modern industrial societies.
