Technology & Engineering
Steam Turbine
A steam turbine is a device that converts the energy from high-pressure steam into mechanical energy, which can then be used to generate electricity or propel machinery. It typically consists of a series of rotating blades mounted on a shaft, and as the steam passes over the blades, it causes the shaft to rotate, thus producing power.
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12 Key excerpts on "Steam Turbine"
eBook - PDFEnergy and Society
An Introduction, Second Edition
- Harold H. Schobert(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
TURBINES AS HEAT ENGINES To obtain high pressures of steam to operate a turbine, we heat it to high tem-peratures. As the high-pressure steam goes through the turbine, it expands, that is, increases in volume. And if the volume increases, the pressure must drop. The essence of a Steam Turbine is illustrated conceptually in Figure 16.7. We have already seen that when a system changes temperature, we can—by inserting the right device—extract work, as in the energy diagram of Figure 16.8. The generic device for extracting work from this spontaneous change in temperature (i.e., ther-mal potential energy) is a heat engine . The Steam Turbine represents one example of a heat engine. The efficiency of operation of a heat engine is given by the equations = -T T T Efficiency HIGH LOW HIGH or = 100 × -T T T % Efficiency HIGH LOW HIGH where the temperatures are always expressed in kelvins. Ideally, of course, we would like the efficiency of any device to be as close to 1 (or 100%) as possible. But from the discussion in Chapter 11, it is impossible to attain a temperature of 0 K (absolute zero), so that It is impossible to attain an efficiency of 100% from any heat engine. 256 Energy and Society (a) Low-pressure, low-temperature steam out High-pressure, high-temperature steam in (b) (c) FIGURE 16.7 As steam passes through a turbine, its pressure and temperature drop, creat-ing an expanded volume. (a) is a cartoon diagram of a simple Steam Turbine; (b) is a cutaway drawing of a turbine; and (c) shows the rotating blades and shafts of an actual turbine. Low temperature Work ou t High temperature FIGURE 16.8 The energy diagram for a thermal system also applies to the Steam Turbine. 257 Electricity from Steam In addition, it is generally much simpler and less costly to heat something than to cool it below ordinary temperatures.
eBook - PDFSustainable Utility Systems
Modelling and Optimisation
- Petar Sabev Varbanov, Jiří Škorpík, Jiří Pospíšil, Jiří Jaromír Klemeš(Authors)
- 2020(Publication Date)
- De Gruyter(Publisher)
6 Steam Turbines 6.1 Overview of Steam Turbines Steam Turbines are the most important class of machines in the energy industry, used to convert heat into work. Steam Turbines need many auxiliary equipment units and use steam as a working fluid. Steam is generated separately and sup-plied to the turbines. This allows the design and operation of the Steam Turbine-based systems using diverse primary resources to generate the steam – starting from fuels as well as solar energy (see Chapter 4). When using fuels, steam can be generated in steam boilers or heat recovery steam generators (Chapter 5). Additionally, when using solar energy, steam is generated in specialised boilers, within concentrating solar power plants (Lovegrove and Stein, 2012). Other potential heat sources for generating steam are geothermal heat (Akrami et al., 2017) and nu-clear reactions (Riznic, 2017). The investment cost of the Steam Turbine units is very high, and the size of this unit is larger than other types of energy conversion equipment especially compared to internal combustion engines. According to the US Environmental Protection Agency (EPA) technology characterisation guide (US EPA, 2015), the equipment cost ranges from nearly 700 US$/kW for the smaller units of 500 kW capacity down to a level lower than 400 US$/kW for large units of 15,000 kW (15 MW) capacity. For this reason, the most common use of Steam Turbines is as a drive of an electric generator for stationary power generation, a direct drive for large process equipment, for in-stance a compressor, or for driving large ships. The most common working fluid of Rankine cycle turbines is water steam, but other fluids are also used – such as organic mixtures in organic rankine cycles (Yu et al., 2018). The temperature range for admission of steam to Steam Turbines is wide, especially for industrial utility systems.
eBook - ePubThermal Power Plant
Design and Operation
- Dipak Sarkar(Author)
- 2015(Publication Date)
- Elsevier(Publisher)
Chapter 6Steam Turbines
The Steam Turbine handles the maximum power demand among all stationary prime movers that are used for electric power generation. A Steam Turbine is a constant volume machine. The relation between nozzle-box pressure and stage pressures vs. load is linear in nature. There are two basic types of Steam Turbines. The impulse stage is best suited for high-pressure region and for small steam quantities. The reaction stage is advantageous at the lower pressure region, where a large volume of steam must be handled. There are three basic methods of steam admission to the turbine: throttle governing, nozzle governing, and bypass governing. Lubrication of the Steam Turbine is required to minimize the rotating friction in the bearings as well as to cool the bearing surfaces. The operation of Steam Turbines suffers from various losses. The Steam Turbine is designed with three distinct operating regimes: constant pressure, true sliding pressure, and modified sliding pressure.Keywords
impulse; reaction; nozzles; moving blades; rotor; turning gear; governing; lubrication; losses; constant pressure; sliding pressure6.1 Introduction
The objective of all heat engines is to convert heat energy into mechanical work. In all heat engines some working fluid is used to which heat is applied, causing it to expand and to perform work overcoming external resistances. After completion of the expansion process heat of the working fluid is rejected to a sink. Thereafter, the fluid receives fresh supply of heat from the source.The working fluid of a steam power plant is “water.” The plant is comprised of a steam generator , in which water receives heat from the heat of combustion of fossil fuels and gets converted to high-energy steam, which then expands through a Steam Turbine and undergoes changes in pressure, temperature, and heat content. During this process of expansion the high-energy steam also performs mechanical work. The plant also consists of a condenser , where steam rejects heat in cooling water and returns to the original state (Figure 6.1
eBook - ePubEnergy and Society
An Introduction, Second Edition
- Harold H. Schobert(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
This lets turbines achieve much higher efficiencies than were ever possible with the reciprocating steam engines. If we disregarded all of the other advantages of the Steam Turbine relative to the reciprocating engine (its speed of operation, freedom from vibration, quietness, etc.), the Steam Turbine would still have to be regarded as an invention of absolutely first-class importance, solely on the basis of the extraordinary improvement in efficiency—which translates directly into much less fuel that must be extracted from the earth, shipped, processed, and burned. THE TURBINE/GENERATOR SET The Steam Turbine has become the standard technology for operating the generator in all the world’s electricity-generating plants (except hydroelectric plants), and to use the turbine most effectively, we need to supply it with a head of steam, as sketched in Figure 16.9. Generating electricity from steam involves a turbine/generator set in which high-pressure, high-temperature steam is used as the working fluid in the turbine, and electrical energy is provided from the generator. Previously, the central problem in electricity generation was said to be that of finding a cheap and reliable way to turn the generator
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
Turbine engines A rotor of a modern Steam Turbine, used in a power plant A Steam Turbine consists of an alternating series of one or more rotating discs mounted on a drive shaft, rotors , and static discs fixed to the turbine casing, stators . The rotors have a propeller-like arrangement of blades at the outer edge. Steam acts upon these blades, producing rotary motion. The stator consists of a similar, but fixed, series of blades that serve to redirect the steam flow onto the next rotor stage. A Steam Turbine often exhausts into a surface condenser that provides a vacuum. The stages of a Steam Turbine are ____________________ WORLD TECHNOLOGIES ____________________ typically arranged to extract the maximum potential work from a specific velocity and pressure of steam, giving rise to a series of variably sized high and low pressure stages. Turbines are only effective if they rotate at very high speed, therefore they are usually connected to reduction gearing to drive another mechanism, such as a ship's propeller, at a lower speed. This gearbox can be mechanical but today it is more common to use an alternator/generator set to produce electricity that later is used to drive an electric motor. A turbine rotor is also only capable of providing power when rotating in one direction. Therefore a reversing stage or gearbox is usually required where power is required in the opposite direction. Steam Turbines provide direct rotational force and therefore do not require a linkage mechanism to convert reciprocating to rotary motion. Thus, they produce smoother rotational forces on the output shaft. This contributes to a lower maintenance requirement and less wear on the machinery they power than a comparable reciprocating engine. The Turbinia - the first Steam Turbine-powered ship The main use for Steam Turbines is in electricity generation (about 80% of the world's electric production is by use of Steam Turbines) and to a lesser extent as marine prime movers.
- Alexander V. Dimitrov(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
2Conversion of Thermal Energy into Mechanical Work (Thermal Engines)Energy-related (power) technologies may be treated as a combination of engineering-technical methods of energy and work conversion employed to facilitate human life. They are divided into two main groups. The first group comprises technologies of heat conversion into another type of energy (mechanical, electrical, electromagnetic, etc.) while the second one comprises technologies of heat transfer, accumulation, and regeneration. Each thermal technology discussed herein will be illustrated by specific physical schemes and devices. We shall consider them in the following order:•Technologies of mechanical work performance (so called thermomechanical technologies) •Technologies of generation of electrical energy (thermoelectric technologies) •Technologies of heat transformation (regeneration and recuperation) •Technologies of heat transfer and collection (transfer and accumulation) •Technologies creating comfortable environment (air conditioning and ventilation)Thus, we will treat a certain technology as an object of study of respective scientific-applied research fields, on one hand, and we will follow the teaching programs on “Power engineering,” “Transport management” and “General mechanical engineering,” on the other hand.2.1 Evolution of Engine TechnologiesAs is known from physics, energy conversion follows a natural course, that is, energy of motion of macro- and microbodies (popular as mechanical energy) is converted into heat by mechanisms that are studied by tribology (including dry, semi-dry, viscous, or turbulent friction). No opposite transformation is observed in nature. Heat conversion into energy needed for the operation of machines and mechanisms was an impossible task for primitive people as well as for those living in slave-holding* and feudal†
No longer available |Learn moreAdvanced Thermodynamics
Fundamentals, Mathematics, Applications
- Mehrzad Tabatabaian, R. K. Rajput(Authors)
- 2017(Publication Date)
- Mercury Learning and Information(Publisher)
C H A P T E R 10 Steam TurbineS In This Chapter l Overview l Classification of Steam Turbines l Advantages of the Steam Turbine over Steam Engines l Description of Common Types of Turbines l Methods of Reducing Wheel or Rotor Speed l Difference between Impulse and Reaction Turbines l Impulse Turbine l Reaction Turbines l Types of Power in Steam Turbine Practice l State Point Locus and Reheat Factor l Steam Turbine Governing and Control l Special Forms of Steam Turbines l Exercises 10.1. Overview The Steam Turbine is a prime mover in which the energy of the steam (including thermal or enthalpy and kinetic) is transformed into kinetic energy of the rotor blade, and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft. The turbine shaft, directly or with the help of a reduction gearing, is connected with the driven mechanism. 382 • ADVANCED THERMODYNAMICS Depending on the type of the driven mechanism, a Steam Turbine may be utilized in most diverse fields of industry, for power generation and for transport. Transformation of the input energy of steam into the mechanical energy of rotation of the shaft is brought about by different means. 10.2. Classification of Steam Turbines There are several ways in which the Steam Turbines may be classified. The most important and common division is with respect to the action of the steam and the way that it interacts with the turbine blades, as: 1. Impulse: when steam impinges on the turbine blades and is redirected to the stationary nozzles to be furthered to the next stage of rotor blades. In this type of turbine kinetic energy of the steam changes but the enthalpy remains constant. 2. Reaction: when steam flows through airfoil-shaped blades and moves the rotor due to the pressure difference created. Steam flows through the turbine similar to a meandering jet stream, and hence moves the rotors at several stages.
eBook - PDF- Heinz P. Bloch, Claire Soares(Authors)
- 1998(Publication Date)
- Butterworth-Heinemann(Publisher)
Chapter 5 Steam Turbines Steam Turbines occur mainly in mechanical drive applications in the process engineer's world. When the plant also has small power generation requirements, the power plant selected is generally a gas turbine. Such is the case at Esso's Sriracha refinery in Thailand which owns two ABB GT35s. Larger facilities often find it economical to make most of their own power. The Syncrude Tar Sands facility in northern Alberta, Canada which refines 170,000 barrels of oil a day is such a facility. Syncrude uses a combination of gas and Steam Turbines. There is also a current emerging global trend that may grow: for oil and gas and petrochemical facilities to make their own power and sell the excess to the local national power grid. However, due to the relative proportion of mechanical drive versus power generation applications that a process engineer is likely to see, this chapter is essentially devoted to mechanical drive turbines. In Steam Turbines, apart from the load factor (close to, or at base or steady load in most power generation applications), the subdivision between mechanical and power generation applications is size. The approximate cut-off for mechanical drive applications is about 100 MW. Sizes above 100 MW are not normally used in compressor drive services. Although less versatile than the gas turbine (a steam plant has to provide design inlet pressure steam, before the Steam Turbine can run), Steam Turbines are reliable and easy to operate. The global distribution of natural gas still favors the utilization of Steam Turbines. At recent tally, the world has about 70 years of natural gas supply left. This figure increases as gas exploration becomes more ambitious. However, as the world has 200 to 300 years worth of coal, a great deal of that in the newly developing global regions, it's easy to see which fuel comes out ahead.
eBook - PDFTotal Energy
International Series in Heating, Ventilation and Refrigeration
- R. M. E. Diamant, N. S. Billington, E. Ower(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
The heat drop through the stage fixes the steam speed, but the blade speed depends on both the blading diameter and the rotor speed. A small rotor diameter and high rotational speed, in relation to volume flow, improves the turbine internal efficiency, by reducing internal steam leakages and, by the use of longer blades, increasing the blading efficiency. Such a turbine design utilises more of the heat in the supply steam and generates more power. Although it is difficult to generalise due to the large permutations of steam pressures, temperatures and flows possible through a given tur-bine, a high-speed geared machine is usually more efficient than a direct-coupled machine for the smaller powers and exhaust volume flows. The gain in power more than offsets the gearing losses. At larger powers with larger exhaust volume flows, the direct-coupled sets be-come more efficient overall. The following basic rules emerge for the generation of power from process steam: Steam TurbineS AND TOTAL ENERGY 59 (1) Use the highest practicable initial pressure and temperature. (2) Use the lowest practicable exhaust or process pressure. (3) Use the smallest size of turbine to give optimum internal efficiency. (4) Never permit a large volume of steam to expand from one pressure to a lower pressure without getting some useful work from the expansion. THE STEAM POWER RATIO Industries fall roughly into three groups. Firstly, large steam users whose steam demand enables them to generate more than sufficient power for their needs. Secondly, factories whose process steam and power loads are approximately in balance. Thirdly, those industries whose power requirements are greater than can be met by using back-pressure turbo-alternators. Factories are constantly improving the efficiency of their steam-using processes and making labour-saving improvements which increase power demand. These factories move from the first and second groups to the second and third groups.
eBook - ePub- Don M. Pirro, Martin Webster, Ekkehard Daschner(Authors)
- 2017(Publication Date)
- CRC Press(Publisher)
One of the more economical ways of generating this steam is with a combined cycle plant, where high-pressure steam is used to power equipment such as generators, and the exhaust steam from this equipment is used for heating or other services. The steam is generated at high pressure and, after expansion through the turbine to the pressure desired for process use, it is delivered to the process application. This permits power to be generated by the turbine without appreciably affecting the value of the steam for process use. It may be done with a back pressure turbine designed to exhaust all the steam against the pressure required for process use, or it may be done with an automatic extraction turbine in which part of the steam is withdrawn for process use at an intermediate stage (or stages) of the turbine and the remainder of the steam exhausted to a condenser. Such a turbine requires special governors and valves to maintain constant pressure of the exhausted steam and constant turbine speed under varying turbine load and extraction demands. Steam can be also extracted without control from various stages of a turbine to heat boiler feed-water (regenerative heating). Such turbines are called uncontrolled extraction turbines, because the pressure at the extraction points varies with the load on the turbine. To obtain higher efficiency, large turbines (called reheat turbines) are arranged so that after expanding part way, the steam is withdrawn, returned to the boiler, and reheated to approximately its initial temperature. It is then returned to the turbine for expansion through the final turbine stages to exhaust pressure. High-pressure noncondensing turbines have been added to many moderate-pressure installations to increase capacity and improve efficiency
eBook - PDFIntroduction to Applied Thermodynamics
The Commonwealth and International Library: Mechanical Engineering Division
- R. M. Helsdon, N. Hiller, G. E. Walker(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
A Steam Turbine is basically a steam nozzle in which the kinetic energy of the steam produced during expansion, is transferred via fixed and moving blades to a rotor mounted along the axis of the nozzle. There are two principal types of turbines: (i) Impulse (Fig. 152). (ii) Reaction (Fig. 154). The basic difference between these two types is that in the impulse turbine the pressure and enthalpy drops occur in the nozzles only, whilst in the reaction turbine they occur in both fixed and moving blades. Impulse turbine Figure 152 shows in diagrammatic form a simple impulse turbine. Steam from the boiler after passing through one or more nozzles distributed round the periphery of the rotor, enters the rotor or 152 STEAM AND STEAM ENGINES wheel chamber at reduced pressure and high velocity, where it impinges on the rotor blades. By undergoing a change of momentum in passing through the moving blades, the steam exerts a force upon the rotor which drives the turbine. In an ideal turbine, the nozzle and blade angles and the steam and blade speeds would be such that the steam (a) enters the moving blades without shock (thus avoiding a Combined velocity diagram FIG. 152. Single-stage impulse turbine. conversion of K.E. back into heat), and (b) leaves the moving blades with zero K.E. Since the steam must have an axial velocity through-out the turbine, it is impossible to convert all the K.E. of the steam at nozzle outlet into work on the rotor. The force exerted on the blades can be found by drawing the velocity diagrams at inlet and outlet to the moving blades. Velocity diagram for impulse turbine (Fig. 152) (a) Single stage Let Vb = blade velocity. Vi = absolute velocity of steam at nozzle exit and blade inlet. V ri — velocity of steam relative to blade at blade inlet. V 0 == absolute steam velocity at blade outlet. 153 APPLIED THERMODYNAMICS Vro = velocity of steam relative to blade at blade outlet =kV r t.
eBook - PDF- G R Jones(Author)
- 2013(Publication Date)
- Newnes(Publisher)
17/2 Turbines 17.17 Power station 17/24 17.18 Turbines 17/25 17.18.1 General principles 17/25 17.18.2 Fundamental similarity 17/26 17.18.3 Specific speed 17/28 17.18.4 Impulse turbines—Pelton wheels 17/29 17.18.5 Reaction turbines—general 17/31 17.18.6 Francis turbines 17/31 17.18.7 Propeller turbines 17/33 17.19 Hydrogenerators 17/34 17.20 Economics 17/34 17.21 Pumped storage 17/35 17.21.1 Historical development 17/35 17.21.2 Mode of operation 17/36 17.21.3 Economics of pumped storage 17/36 17.22 Tidal power 17/36 Steam Turbine PLANT The Steam Turbine is a prime-mover well suited to the direct drive of two- or four-pole high-speed a.c. generators for power-supply networks. The associated steam-raising plant can be fired by a wide variety of fuels—fossil, nuclear and such unusual fuels as city refuse, sawdust and sugar waste. The turbine can accept a low exhaust temperature (making possible a reasonable thermal efficiency) and a moderate inlet temperature (permitting a long life, e.g. 200 000 h). The turbine is best suited to high power ratings, as parasitic losses tend to be independent of size; further, output ratings can be raised without a pro-rata increase in materials, so giving a higher power cost ratio. Steam Turbines are constructed in the range 5-1300 MW. At the highest ratings the only comparable prime-mover is the hydraulic turbine, while at the lower end of the range the Steam Turbine competes with the diesel engine and the gas turbine. Besides generator drive, the Steam Turbine is applied to ship propulsion and to rotary compressors. This chapter deals exclusively with electric power generator drive applications. 17.1 Cycles and types 17.1.1 Reheat cycle Most fossil-fuel-fired generating stations use the reheat cycle. Currently, outputs span the range 200-1300 MW. Common steam conditions are 16 MPa, 540°C (2350 lbf/in. 2 , 1000°F).
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