3000 4000 5000 6000 7000 To0q 900c

POWER TURBINE SPEED, rpm

Fig. 10-52 Nominal Rated Performance for Continuous Duty, ISO Matched Gas Fueled, Gas Turbine. Source: Solar Turbines with combustion gas exits as a clean, dry, oxygen-rich stream at temperatures of approximating 1,000°F (490°C). Supplementary firing with duct-burners can increase heat recovery capacity and efficiency by increasing the temperature of the exhaust.

Gas Turbine Exhaust Characteristics Under Part-load Operation

Reducing fuel input to the gas turbine under part-load operation causes a reduction in exhaust gas temperature, particularly with single-shaft turbines, which maintain constant exhaust flow. Some applied turbine designs feature IGVs, which reduce mass flow under part loads, thereby maintaining relatively higher exhaust temperatures.

Figures 10-54, 10-55, and 10-56 provide representative samples of gas turbine exhaust performance characteristics as a function of percent of full-load operation for applied turbine designs featuring single-shaft, two-shaft, and singleshaft with IGV. Figure 10-54 depicts recoverable exhaust energy versus load. Figures 10-55 and 10-56 depict exhaust flow versus load and exhaust temperature versus load, respectively.

Fig. 10-54 Recoverable Gas Turbine Exhaust Energy vs. Load. Source: Cogen Designs, Inc.

Fig. 10-55 Gas Turbine Exhaust Flow vs. Load. Source: Cogen Designs, Inc.

Fig. 10-56 Gas Turbine Exhaust Temperature vs. Load. Source: Cogen Designs, Inc.

Fig. 10-54 Recoverable Gas Turbine Exhaust Energy vs. Load. Source: Cogen Designs, Inc.

Figure 10-54 indicates a fairly linear relationship for all three applied designs, with the percent of full-load recoverable exhaust energy being slightly greater than the corresponding percent of full-load. Notice in Figure 10-55 that exhaust flow remains constant with the single-shaft design. The two-shaft design shows a fairly linear relationship, though exhaust flow is disproportionately high throughout the entire range. The single-shaft design featuring IGVs shows a fairly linear relationship down to 80% of full-load operation and remains constant at lower loads. Notice the relationship between the exhaust temperature in Figure 10-55 and the exhaust flow in Figure 10-56.

Fig. 10-56 Gas Turbine Exhaust Temperature vs. Load. Source: Cogen Designs, Inc.

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