Regenerator is a heat exchanger which is used to exchange the waste heat of gases exhausted from turbine to air after compression but before combustion as shown in Figure 5.25. Due to this fuel economy, the efficiency of plant increases.
Figure 5.25 Gas Turbine with Regenerator
It is theoretically possible to raise the temperature of the compressed air from T2 to T6 =T4 and reduce the temperature of gas leaving the turbine from T4 to T5=T2 by arranging a counter flow heat exchanger. The T–s diagram of Brayton cycle for a gas turbine with regenerator is shown in Figure 5.26.
Figure 5.26 T–s Diagram for Brayton Cycle Using Regenerator
Addition of heat exchanger in a gas turbine cycle increases the value of both overall efficiency and specific output for a given pressure ratio but increase in output is very nominal because regenerator lowers the pressure ratio at which peak efficiency occurs.
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