2 Literature review on gas turbine performance

2.4 Components efficiency

Individual components inside the turbo machine play a major role for power output and the efficiency. Compressor, turbine, combustion chamber, casing and blades can be considered as individual components inside the turbo machine and among them compressor and turbine are the most critical components. By reducing the internal component losses of individual component, the overall performance of the gas turbine can be uplifted (Petek, et al., 2005).
Both the compressor and the turbine individual isentropic efficiencies are proportional to the overall gas turbine thermal efficiency (Rahman, et al., 2011)and figure 11 and figure 12 show the relationship between individual isentropic efficiencies and the overall thermal efficiency of the gas turbine. In both cases the thermal efficiency of the gas turbine increases with the individual component efficiencies.

Figure 11: Effect of isentropic compressor efficiency air to fuel ratio on thermal efficiency. (Rahman, et al., 2011)
The difference between the turbine work and compressor work can be defined as net work output of the gas turbine. Thus the net work output has direct influence from the compressor and turbine work and their efficiency. Therefore the individual components efficiencies directly influence the gas turbine efficiency.

Figure 12: Effect of isentropic turbine efficiency air to fuel ratio on thermal efficiency. (Rahman, et al., 2011)
According to literature there are different types of efficiencies for the individual components such as isentropic efficiency total to total, isentropic efficiency total to static, and the polytropic efficiency. By means of the fundamental gas turbine equations, the different types of individual component efficiencies and their influence on the gas turbine performances can be measured. Before going to discuss about types of efficiencies it is beneficial to get familiarized with some fundamental thermodynamic principles related to compressible fluids.