Finite Time Thermodynamic Analysis of Brayton Cycle

Abstract

The Brayton cycle was first proposed by George Brayton in 1870 for the reciprocating oil-burning engine and has been extensively used in power plants and aeroplanes since then. Today, it is used for gas turbines only where both the compression/expansion processes may operate on either in an open or a closed cycle. The Brayton cycle may be either an open or a closed cycle depending on the working fluid; e.g., for gas other than air, a closed cycle is desirable. In the open cycle, the atmospheric air is continuously drawn into the compressor, where it is compressed to a high pressure. The air then enters the combustion chamber where it is mixed with the fuel and combustion occurs, resulting in combustion products at an elevated temperature and pressure. The combustion product at high temperature and pressure then expands through the turbine and subsequently discharged to the atmosphere. Also, the turbine work developed is partly used to drive the compressor, while the remainder is available to generate electricity, to propel vehicle, and/or for other useful purposes (Fig. 3.1a).The open gas turbine cycle described here can be modelled as a closed cycle by utilizing the air standard assumption, as shown in Fig. 3.1b.