Steam turbines section

Understanding the design characteristics of the dual or triple pressure HRSG and its corresponding steam turbine sections (HP, IP, and LP turbines) is important. Increasing pressure of any section will increase the work output of the section for the same mass flow. However, at higher... 

NOTE The electrical generation process is somewhat more efficient than the steam turbine section (up to perhaps 97% efficient). 

The superheated steam generated in the superheater section is coHected in a header pipe that leads to the plant s high pressure steam turbine. The steam turbine s rotor consists of consecutive sets of large, curved, steel aHoy disks, each of which anchors a row of precision-cast turbine blades, also caHed buckets, which protmde tangentiaHy from the shaft and impart rotation to the shaft when impacted by jets of high pressure steam. Rows of stationary blades are anchored to the steam turbine s outer sheH and are located between the rows of moving rotor blades. 

The steam turbines in most of the large power plants are at a minimum divided into two major sections the High Pressure Section (HP) and the Low Pressure Section (LP). In some plants, the HP section is further divided into a High Pressure Section and an Intermediate Pressure Section (IP). The HRSG is also divided into sections corresponding with the steam turbine. The LP steam turbine s performance is further dictated by the condenser backpressure, which is a function of the cooling and the fouling. 

The efficiency of the steam section in many of these plants varies from 30-40%. To ensure that the steam turbine is operating in an efficient mode, the gas turbine exhaust temperature is maintained over a wide range of operating conditions. This enables the HRSG to maintain a high degree of effectiveness over this wide range of operation. 

The theoretical steam rate must then be divided by the efficiency to obtain the actual steam rate. See the section on Steam Turbines Efficiency. 

Figure 14-16E. Section view multistage, multivalve steam turbine, same as Figure 14-16D. (Used by permission Bui. VIP 901. Murray Turbomachinery Div., Tuthill Corporation.)...

Engineering Section, Small Steam Turbine Dept., General Electric Co., How M-d Turbines Are Governed, Power, p. 68, May (1959). 

Diesels, gas turbines and steam turbines are the more commonly used prime movers for the generation of electrical power. Additionally, the steam turbine can be employed in combination with either the diesel or gas turbine for combined cycle operation. The following describes the basic operation of each of these prime movers in relation to its associated power-generating scheme and reviews the more significant factors affecting performance and efficiency. Further information on the actual plant and installation is given later in Section 15.6. 

As discussed earlier (Section 15.3), steam turbines providing low-pressure steam are more established for CHP. However, for lower heat loads the diesel and gas turbine with waste heat recovery offer an attractive alternative. 

All machines require some form of motive power, which is referred to as a driver. This section includes the monitoring parameters for the two most common drivers electric motors and steam turbines. 

As discussed under boiler feedwater treatment, boiler blowdown is required to prevent the build up of solids in the boiler that would otherwise cause fouling and corrosion in the boiler. Carry over of solids from the boiler to the steam system via tiny water droplets should also be avoided. Total dissolved solids (TDS) and silica (SiC>2), as measured by the conductivity of water, are both important to be controlled in the boiler3. Dissolved solids carried over from the boiler will be a problem to all components of the steam system. Silica is a particular problem because of its damaging effect on steam turbines, particularly the low-pressure section of steam turbines where some condensation can occur. Blowdown... 

Any given machine will have minimum and maximum allowable steam flows. In the case of extraction and induction machines, there will be minimum and maximum flows allowable in each turbine section. These minimum and maximum flows are determined by the physical characteristics of individual turbines and specified by the turbine manufacturer. 

Extraction steam turbines will have minimum and maximum flows in each section of the turbine. This leads to minimum and maximum flows at each extraction level. 

Figure 7.18. Heavy-duty centrifugal, axial, and reciprocating compressors, (a) Section of a three-stage compressor provided with steam-sealed packing boxes (DeLaval Steam Turbine Co.), (b) An axial compressor (Clark Brothers Co.), (c) Double-acting, two-stage reciprocating compressor with water-cooled jacket and intercooler (Ingersoll-Rand Co.).

As the jet from a nozzle is frequently employed for power purposes in a steam turbine or a Pelton wheel, we are interested in its energy efficiency. The efficiency of a nozzle is defined as the ratio of the power in the jet to the power passing a section in the pipe at the base of the nozzle. As the discharge is the same for the two points, the efficiency is merely the ratio of the heads at these two sections. Thus, referring again to the conical nozzle, e = HJH. But H2 = V2/2g, and Hr = pjw + V t2g, and so from Eq. (10.59) it follows that H2 = C2,H1. Hence the nozzle efficiency is... 

The control of steam turbines will be discussed separately in Section 2.19. Therefore, here the focus will be on the optimization of gas turbine (GT) operation. The GT system consists of three main parts the air compressor (axial type), the burners, and the turbine itself. The mechanical power gener-... 

Section II of the turbine and the second feedwater heater are shown in Fig. In doing the same calculations as for section I, we assume that each kilogram steam leaving section II expands from its state at the turbine entrance to the exit... 

Consider the first section of the turbine and the first feedwater heater, as shown by Fig. 8.6. The enthalpy and entropy of the steam entering the turbine are found from the tables for superheated steam. The assumption of isentropic expansion of steam in section I of the turbine to 2,900 kPa leads to the result ... 

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