Type of Gas turbines

Type of Gas turbines

Gas turbines can be divided into three main types:

Heavy-duty industrial gas turbines (GTs), - Conventional

which are considered ‘conventional in design’: The firing temperatures and cycle efficiency of these units are conservative by modern standards and this is reflected in the design and choice of materials throughout the GT. These units range in output from 15 to 170 MW and yield an open cycle efficiency of approximately 29 to 34 per cent. These conventional design units are noted for being very reliable machines and they have accumulated considerable operating hours.

Heavy-duty industrial GTs, - Modern

which are considered ‘state of the art’: The firing temperatures, compression ratios, combustion systems, cooling and sealing systems, material selection, manufacturing processes and blading designs in these machines are considered in many cases to be ’state of the art’. In general, these units fall into two main output bands in simple cycle 50 Hz configuration: 60 to 70 MW and 250 to 270 MW. The open cycle efficiency figures range from about 34 to 38 per cent.

Aero-derivative GTs: 

These GTs, as the term suggests, are land-based derivatives of successful aero-engine designs. Aero-derivative units are characterised by high open cycle efficiency figures and short start-up times, compared with heavy-duty industrial GTs. The largest aero-derivative GTs are in the region of 45 to 50 MW, going down to 2 to 3 MW at the low end of the range. Typically, open cycle efficiencies in the 25 to 50 MW output band are in the range 38 to 42 per cent.

All three types of gas turbines can be used in open-cycle (OCGT) or combined-cycle (CCGT) configuration, which are described below in more detail.