ABSTRACT

Steam turbines are similar in operation to gas turbines but operate at lower speeds and have steam as the working fluid. The Rankine cycle on which steam power plants are based is briefly discussed in the beginning of the chapter. This is followed by a detailed discussion about multi-staging in steam turbines. The necessity of impulse stages during the initial expansion is explained. The expansion through the impulse stages can take place through velocity compounding (Curtis stages) or pressure compounding (Rateau stages). It is shown that in velocity compounding, the total energy produced increases substantially, as opposed to a single impulse stage. The performance parameters for steam turbines are discussed next. In addition to the usual degree of reaction and utilization factor, two other factors, namely, reheat factor and quality factor, are introduced. The dependence of efficiency of steam turbines on quality factor is discussed. Finally, the design aspects of steam turbines are briefly mentioned.