Chapter 13 Gas Turbine Power Plants

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where the numerator is proportional to the energy received by the cooler air, and the denominator is the ideal heat transfer to the cooler air. Values of s. depend on the effectiveness of the heat exchanger design and the air flow rate, but typical values of effectiveness lie in the range 0.6-0.8. Procedures for heat exchanger design are presented by Incropera and DeWitt (1990). Compressor and turbine work for the Brayton cycle with regeneration are handled as with the basic cycle. Only the energy addition in the combustor, as determined from (13.17), is different, but this increases the thermal efficiency, since the denominator of (13.1) is decreased while the numerator remains fixed. The denominator Q A can be written alternatively as M (13.19) where Mf IM a is the mass of fuel by the corresponding mass of air, i.e., the fuel-air ratio F/A, introduced in Chapter 11. Since the equivalent heat transfer Q A , resulting from the burning of fuel in the combustor, is directly proportional to the mass of fuel burned Mp and since Q A is reduced by the addition of the regenerator, the amount of fuel required to produce a unit of net work is decreased, i.e., the specific fuel consumption is reduced. Paralleling the definition introduced in Chapter 11 for internal combustion engines, specific fuel consumption (sfc) is defined by m f -f (13.20) where mj denotes the mass flow rate of fuel and P represents the net power produced by the gas turbine. Usually the power is the shaft power to the load, as indicated in Figure 13.5, and the sfc is
Air In Regenerator •* — ——— 05 02' I ——— Compressor 03, ——— ^ —— ^ Turbine Turbine Exhaust .. 04' Figure 13.5 Gas turbine plant with regeneration called the brake specific fuel consumption (bsfc), as defined in (11.17). In applications of gas turbines for road vehicles, railroad locomotives and ship propulsion a power turbine may be used. This requires two turbines on separate shafts, each running at a different speed. Figure 13.6 shows a typical arrangement: a highpressure (H.P.) turbine driving the compressor and a low-pressure (L.P.) turbine driving the load. As shown in the figure, the H.P. turbine and compressor are on the same shaft. This unit is called a gas generator, because it supplies gas to the power turbine but drives no load itself. Since the gas generator drives no load, the work of the H.P. turbine equals the work of the compressor. When a power turbine is used to drive a generator, no gear box is required, as with a single-shaft engine. Also for traction purposes the torque-speed characteristics of the power turbine are more favorable than those of the dual-purpose turbine.
Page 1 and 2: Chapter 13 Gas Turbine Power Plants
Page 3 and 4: in the cycle 1-2-3-4-1, the cycle i
Page 5 and 6: - r ^02 ~ -' and (13.8) which are d
Page 7 and 8: Q A =C p (T 03 -T 02 .) (13.14) whe
Page 9: 1200 1000 800 S I 0> c. 600 I 1a Tu
Page 13 and 14: Air In + 06 Figure 13.7 Gas turbine
Page 15 and 16: actual compression in the first sta
Page 17 and 18: heated from T 08 -to T 09 , The fin
Page 19 and 20: 13.8 Combined Brayton and Rankine C
Page 21 and 22: Problems 13.1 Write the expression
Page 23 and 24: 13.12 A Brayton cycle with regenera
Page 25 and 26: fuel-air ratio, the net power devel
Page 27: the combine cycle, and the thermal

Chapter 13 Gas Turbine Power Plants

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