A turbine composed of moving nozzles alternating with fixed nozzles is called a reaction turbine or Parsons turbine. 3. 1 A much later arrangement than Turbinia can be seen on RMS Queen Mary in Long Beach, California, launched in 1934, in which each shaft is powered by four turbines in series connected to the ends of the two input shafts of a single-reduction gearbox. , we get V k 2 The enthalpy drop in the fixed blades, with the assumption that the velocity of steam entering the fixed blades is equal to the velocity of steam leaving the previously moving blades is given by: where V0 is the inlet velocity of steam in the nozzle, V ( ρ 1 ( ii ) Reaction Turbine: Also known as the impulse reaction turbine there is a pressure drop across both nozzle and rotor blades. 1 = 1 During normal operation in synchronization with the electricity network, power plants are governed with a five percent droop speed control. Reaction turbine 2. Assuming there is no heat transfer to the surrounding environment and that the changes in kinetic and potential energy are negligible compared to the change in specific enthalpy we arrive at the following equation. The system was less costly initially than reduction gears and made the ships more maneuverable in port, with the shafts able to reverse rapidly and deliver more reverse power than with most geared systems. cos This is achieved by a re-heater incorporated within the boiler; that increase the steam temperature to maintain them at superheated condition throughout the entire stage. V This design of rotor is also called two-flow, double-axial-flow, or double-exhaust. ρ The turbines used for electric power generation are most often directly coupled to their generators. The sets intermesh with certain minimum clearances, with the size and configuration of sets varying to efficiently exploit the expansion of steam at each stage. cos . V V They reach top values up to about 50% in a 1,200 MW (1,600,000 hp) turbine; smaller ones have a lower efficiency. Other than that they are also used in electrical applications and small industries. 1 − Overall they satisfy a higher demand for large capacity at a much lower cost than multi-cylinder turbines. Electrical power stations use large steam turbines driving electric generators to produce most (about 80%) of the world's electricity. Amphibious and auxiliary ships continued to use 600 psi (4,100 kPa) steam post-World War II, with USS Iwo Jima, launched in 2001, possibly the last non-nuclear steam-powered ship built for the US Navy. W (for a single stage impulse turbine). = eval(ez_write_tag([[250,250],'shipfever_com-leader-1','ezslot_5',108,'0','0']));eval(ez_write_tag([[250,250],'shipfever_com-leader-1','ezslot_6',108,'0','1']));These turbines can be quickly warmed and started; making is quite suitable at times of peak load. η = and the enthalpy of steam at the exit of the nozzle is The development of steam turbine marine propulsion from 1894 to 1935 was dominated by the need to reconcile the high efficient speed of the turbine with the low efficient speed (less than 300 rpm) of the ship's propeller at an overall cost competitive with reciprocating engines. All steam turbines can be classified into different types based on the number of cylinders, general flow, means of heat supply, Operating principle and direction of flow. = It was used in John Brown-engined merchant ships and warships, including liners and Royal Navy warships. Here the blades are subjected to both pressure and kinetic energy. Multiple reaction stages divide the pressure drop between the steam inlet and exhaust into numerous small drops, resulting in a pressure-compounded turbine. The prevalent type in the United States is the massive concrete foundation; A few of the steel foundations have been installed. Reduction gears allowed turbines to operate in their efficient range at a much higher speed than the shaft, but were expensive to manufacture. Steam turbines are used to drive electrical generators in thermal power plants which use coal, fuel oil or nuclear fuel. Therefore, the relative velocity at the exit Similarly, based on exhaust conditions, there are five main types of steam turbines; condensing, non-condensing, automatic extraction, mixed pressure, and regenerative extraction. [39] Some auxiliary ships continue to use steam propulsion. 1 cos The Royal Navy decommissioned its last conventional steam-powered surface warship class, the Fearless-class landing platform dock, in 2002, with the Italian Navy following in 2006 by decommissioning its last conventional steam-powered surface warships, the Audace-class destroyers. eval(ez_write_tag([[300,250],'shipfever_com-medrectangle-3','ezslot_2',116,'0','0']));Based on the number of cylinders steam turbines are of two types; single cylinder and multi-cylinder turbines. w b + is very small and hence can be neglected. ρ Also, liquid water entering the blades may damage the thrust bearings for the turbine shaft. [21], The nickel-based blades are alloyed with aluminum and titanium to improve strength and creep resistance. Nozzles appear similar to blades, but their profiles converge near the exit. In Impulse turbine, since there is no effect of rotors on the acceleration of steam flow. These included small reciprocating engines and geared or ungeared cruising turbines on one or two shafts. In Reaction turbine, there is a gradual drop in pressure across the turbine blades. He taught at the École des mines de Saint-Étienne for a decade until 1897, and later founded a successful company that was incorporated into the Alstom firm after his death. [40][41][42] Diesel power plants also have lower operating costs since fewer operators are required. To measure how well a turbine is performing we can look at its isentropic efficiency. α o cos 2 U r The ratio of the blade speed to the absolute steam velocity at the inlet is termed the blade speed ratio {\displaystyle F_{u}={\dot {m}}\left(V_{w1}-V_{w2}\right)} 2 ) Also, a turning gear is engaged when there is no steam to slowly rotate the turbine to ensure even heating to prevent uneven expansion. U this allows for better flexibility, simple design and lower cost. U Using reheat in a cycle increases the work output from the turbine and also the expansion reaches conclusion before the steam condenses, thereby minimizing the erosion of the blades in last rows. Δ Nuclear propulsion has only been applied to a very few commercial vessels due to the expense of maintenance and the regulatory controls required on nuclear systems and fuel cycles. This is required for the stable operation of the network without hunting and drop-outs of power plants. ρ . cos 1 ( iii ) Tangential Flow Turbine: These are types of turbines where the steam flows tangentially to the rotor shaft axis. [1][2], The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process. U ρ The interior of a turbine comprises several sets of blades or buckets. b Superheated steam (or dry saturated steam, depending on application) leaves the boiler at high temperature and high pressure. To limit creep, thermal coatings and superalloys with solid-solution strengthening and grain boundary strengthening are used in blade designs. V This type of turbine is mainly used in power plants (for example, in high temperature solar thermal power plants), but also in other applications where large capacities are required, such as offshore vessels. The first turbine was called the high pressure (HP) turbine, the last turbine was the low pressure (LP) turbine, and any turbine in between was an intermediate pressure (IP) turbine. British, German, other national and international test codes are used to standardize the procedures and definitions used to test steam turbines. While based on the flow of steam they can be classified as a single flow, double flow and reverse flow turbines. in the expression of r , therefore α ˙ 2 {\displaystyle V_{0}} . {\displaystyle {\eta _{b}}_{\text{max}}=\cos ^{2}\alpha _{1}} is always greater than the relative velocity at the inlet E {\displaystyle {\frac {U}{V_{1}}}={\frac {1}{2}}\cos \alpha _{1}} To prevent this, along with controls and baffles in the boilers to ensure high-quality steam, condensate drains are installed in the steam piping leading to the turbine. It can operate with any pressure of steam, but is considerably less efficient. ( ii ) Non Condensing Turbine: Its a simple turbine configuration that uses a high pressure steam for rotating the blades. 1 Another alternative is turbo-electric transmission, in which an electrical generator run by the high-speed turbine is used to run one or more slow-speed electric motors connected to the propeller shafts; precision gear cutting may be a production bottleneck during wartime. 2 [9] In 1827 the Frenchmen Real and Pichon patented and constructed a compound impulse turbine. Learn how your comment data is processed. w A turbine composed of blades alternating with fixed nozzles is called an impulse turbine, Curtis turbine, Rateau turbine, or Brown-Curtis turbine. Note: I have tried best to answer your queries. The effect of expansion of steam over the moving blades is to increase the relative velocity at the exit. Nuclear-powered ships and submarines use a nuclear reactor to create steam for turbines. Impulse Turbine. {\displaystyle \rho =\cos \alpha _{1}} In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. t Turbine steam engines are the next evolutionary step of piston machines. But before we proceed you must have a clear idea about; what is turbine, how does it work, Its basic parts and applications. V = = ⁡ 1 To reduce this risk, considerable efforts are spent to balance the turbine. The blades thus transform the device potential energy to that of kinetic movement. h − . The steam from the boilers enters from the right at high pressure through a throttle, controlled manually by an operator (in this case a sailor known as the throttleman). These stages are characterized by how the energy is extracted from them and are known as either impulse or reaction turbines. [16] The consulting firm Frost & Sullivan projects that manufacturing of steam turbines will become more consolidated by 2020 as Chinese power manufacturers win increasing business outside of China.[17]. Despite the introduction of many alternative technologiesin the intervening 120 years, over 80 percent of the world's electricity is still generated by steam turbines driving rotary generators. η A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. , and we get Tandem compound are used where two or more casings are directly coupled together to drive a single generator. {\displaystyle c=1} u Turbo-electric drive was most used in large US warships designed during World War I and in some fast liners, and was used in some troop transports and mass-production destroyer escorts in World War II. Turbine blades are of two basic types, blades and nozzles. ρ ρ Its modern manifestation was invented by Charles Parsons in 1884. The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure. Four different types of rotor construction have been used on large turbine-generator units on the CEGB system: The monobloc or integral rotor, in which the wheels and shaft are formed from a single-piece forging (Fig 1.104 (a)). {\displaystyle U=\omega r} Types Of Steam Turbines Types Of Steam Turbines:– The best definition for a turbine one might provide is that the conversion of steam’s heat to mechanical work, that is finished on a rotating output shaft. Single casing units are the most basic style where a single casing and shaft are coupled to a generator. ) max These jets contain significant kinetic energy, which is converted into shaft rotation by the bucket-like shaped rotor blades, as the steam jet changes direction. − ( ( ii ) Reheat Turbines: For large multi-stage turbines there needs to be steam reheating before the steam exit the turbine. is appreciably less than c The lingering fondness for reciprocating machinery was because the US Navy had no plans for capital ships exceeding 21 knots (39 km/h; 24 mph) until after World War I, so top speed was less important than economical cruising. d {\displaystyle W=T\omega } < In terms of velocities, the enthalpy drop over the moving blades is given by: (it contributes to a change in static pressure). As temperatures are increased in an effort to improve turbine efficiency, creep becomes significant. 2 The steam leaves the turbine as a saturated vapor (or liquid-vapor mix depending on application) at a lower temperature and pressure than it entered with and is sent to the condenser to be cooled. with tangential velocity A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage. 1 1. f Some ocean liners were also built with turbo-electric drive, as were some troop transports and mass-production destroyer escorts in World War II. = 2 Blade efficiency ( m But due to formidable design challenges at the larger size, they are largely in smaller size up to 300-350 MW demand. V {\displaystyle \rho ={\frac {U}{V_{1}}}} There are two general types of steam turbine designs. There are several classifications for modern steam turbines. On the left are several additional reaction stages (on two large rotors) that rotate the turbine in reverse for astern operation, with steam admitted by a separate throttle. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. Induction turbines introduce low pressure steam at an intermediate stage to produce additional power. 1 So, basically Steam turbine governing system is a process where turbine maintains a steady output speed irrespective of variation of load. Extracting type turbines are common in all applications. A generator or other such device can be placed on the shaft, and the energy that was in the steam can now be stored and used. α Therefore, the tangential force on the blades is d Steam turbines are made in a variety of sizes ranging from small <0.75 kW (<1 hp) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 1,500 MW (2,000,000 hp) turbines used to generate electricity. The work done per unit time or power developed: An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. Here the pressure drops as it passes through the moving blades adding more kinetic energy to the subsequent blades in front. Most steam turbines use a mixture of the reaction and impulse designs: each stage behaves as either one or the other, but the overall turbine uses both. The power developed is then {\displaystyle E} p V cos Steam Turbine. Further, they need to maintain minimum axial clearances between adjacent rotor and stater blades. Now since these turbines work with high positive gradient. Over the next eight years the US Navy launched five additional turbo-electric-powered battleships and two aircraft carriers (initially ordered as Lexington-class battlecruisers). In the United States, ASME has produced several performance test codes on steam turbines. Our steam turbine portfolio spans across all fuels including gas, nuclear, coal, oil, biomass, solar and municipal waste – from 20 MW to 1,900 MW. [33][34] A standard configuration emerged of an axial-flow high-pressure turbine (sometimes with a cruising turbine attached) and a double-axial-flow low-pressure turbine connected to a double-reduction gearbox. The major types of steam turbines are condensing and non-condensing, extraction, reheat turbines, and several varieties of multiflow turbines. and depicts the loss in the relative velocity due to friction as the steam flows around the blades ( η Turbines are expensive to make, requiring precision manufacture and special quality materials. After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10–15 RPM (0.17–0.25 Hz) to slowly warm the turbine. Within Parsons' lifetime, the generating capacity of a unit was scaled up by about 10,000 times,[13] and the total output from turbo-generators constructed by his firm C. A. Parsons and Company and by their licensees, for land purposes alone, had exceeded thirty million horse-power. [18] A reaction stage is a row of fixed nozzles followed by a row of moving nozzles. η An exception is LNG carriers which often find it more economical to use boil-off gas with a steam turbine than to re-liquify it. 1 Thrust bearings can be used for the shaft bearings, the rotor can use dummy pistons, it can be double flow- the steam enters in the middle of the shaft and exits at both ends, or a combination of any of these. We can have a much larger pressure drop across stages. [28] The first law enables us to find a formula for the rate at which work is developed per unit mass. The steam pressure at the outlet depends on the load, thus can be anywhere in between atmospheric pressure and low pressure steam. 2 Generally this is a basic system requirement for all power plants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication. Turbines may be a combination of these types based on all their requirements. [22], Refractory elements such as rhenium and ruthenium can be added to the alloy to improve creep strength. or, The steam leaving the moving blades has a large portion of the maximum velocity of the steam when leaving the nozzle. In its simplest form, a steam turbine consist of a boiler (steam generator), turbine, condenser, feed pump and a variety of auxiliary devices. [16] Other manufacturers with minor market share include Bharat Heavy Electricals Limited, Siemens, Alstom, General Electric, Doosan Škoda Power, Mitsubishi Heavy Industries, and Toshiba. Δ 1 These coatings are often stabilized zirconium dioxide-based ceramics. Protective coatings are used to reduce the thermal damage and to limit oxidation. The first steam turbine rail locomotive was built in 1908 for the Officine Meccaniche Miani Silvestri Grodona Comi, Milan, Italy. The loss of energy due to this higher exit velocity is commonly called the carry over velocity or leaving loss. The variation in load during the operation of a steam turbine can have a significant impact on its performance. A velocity triangle paves the way for a better understanding of the relationship between the various velocities. Because of the high temperatures and high stresses of operation, steam turbine materials become damaged through these mechanisms. Blades of Impulse & Reaction turbines ) Except for low-power applications, turbine blades are arranged in multiple stages in series, called compounding, which greatly improves efficiency at low speeds. Although there only two types of steam turbine there are numerous mechanical arrangements of these, which include reheat steam turbines, cross compound steam turbines, single casing turbines, tandem steam turbines, condensing and exhaust steam turbines and, axial and radial flow steam turbines. Since ships are rarely operated in reverse, efficiency is not a priority in astern turbines, so only a few stages are used to save cost. 1 The best thing about single cylinder turbines is that they can be run with much lower steam flow than normal. r For this turbine the velocity triangle is similar and we have: Assuming Parson's turbine and obtaining all the expressions we get, From the inlet velocity triangle we have ≈ Also, turbines are run with high-quality steam: either superheated (dry) steam, or saturated steam with a high dryness fraction. V Our steam turbines equip 41% of the world’s combined-cycle plants, 30% of fossil power plants, and 50% of the world’s nuclear power plants. {\displaystyle c={\frac {\cos \beta _{2}}{\cos \beta _{1}}}} ( Steam turbines are made in a variety of sizes ranging from small <0.75 kW (<1 hp) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 1,500 MW (2,000,000 hp) turbines used to generate electricity. = 2 Harbin Electric, Shanghai Electric, and Dongfang Electric, the top three power equipment makers in China, collectively hold a majority stake in the worldwide market share for steam turbines in 2009-10 according to Platts. 1 d . As the steam flows through the nozzle its pressure falls from inlet pressure to the exit pressure (atmospheric pressure or, more usually, the condenser vacuum). . h ) can be defined as the ratio of the work done on the blades to kinetic energy supplied to the fluid, and is given by. 1 = is found by putting the value of W η 1 k ρ [11] The invention of Parsons' steam turbine made cheap and plentiful electricity possible and revolutionized marine transport and naval warfare. = h F Variable from little to massive, the turbines are created in a very big range of power capacities. 0 V . ρ , we get, and this finally gives . But there are two basic types of steam turbines: impulse turbines; reaction turbines. {\displaystyle \Delta h_{f}={\frac {V_{1}^{2}}{2}}}. cos The Indian Navy currently operates INS Vikramaditya, a modified Kiev-class aircraft carrier; it also operates three Brahmaputra-class frigates commissioned in the early 2000s and one Godavari-class frigate scheduled for decommissioning. We will also discuss here what is turbine, main parts of the turbine and the working principle of a turbine. 1 h k 2 max Such turbine types are commonly called as reheated turbines. ( iii ) Dual Pressure Turbine: A mixed or dual pressure turbine use two separate source of steam at different pressure. In general, a steam turbine is a rotary heat engine that converts thermal energy contained in the steam to mechanical energy or to electrical energy. d Nozzle efficiency is given by A major challenge facing turbine design was reducing the creep experienced by the blades. Turbine - Turbine - Steam turbines: A steam turbine consists of a rotor resting on bearings and enclosed in a cylindrical casing. . Reheat turbines are also used almost exclusively in electrical power plants. Under these circumstances, their stages are housed under different casing with separate shafts and bearings. β This would be a speed used on long voyages when fuel economy is desired. Ten more turbo-electric capital ships were planned, but cancelled due to the limits imposed by the Washington Naval Treaty. Because they recognized that a long cruising range would be desirable given their worldwide empire, some warships, notably the Queen Elizabeth-class battleships, were fitted with cruising turbines from 1912 onwards following earlier experimental installations. ; The built-up or shrink-on disc rotor, consisting of a forged steel shaft onto which separate forged steel discs are shrunk and keyed (Fig 1.104 (b)). Tangential flow turbines are generally used in hydropower generation. α 1 {\displaystyle V_{2}} ) {\displaystyle \Delta h_{m}} U These are generally quite robust and efficient machinery used mostly as the auxiliary turbines in power generation. For example, they may be required to start on one pressure and operate under different steam pressure. . The quest for economy was even more important when cruising speeds were considered. A cross compound turbine is typically used for many large applications. ( {\displaystyle {\eta _{b}}_{\text{max}}} Δ eval(ez_write_tag([[250,250],'shipfever_com-medrectangle-4','ezslot_13',117,'0','0']));( i ) Impulse Turbine: Impulse turbines have this assembly of the fixed nozzle and moving blades; where the steam flow through the system with little to no pressure change between the inlet and outlet of moving blades. These turbines are quite cheap and simple in construction. Nozzles move due to both the impact of steam on them and the reaction due to the high-velocity steam at the exit. − ) 0 In 1775 at Soho James Watt designed a reaction turbine that was put to work there. = In this way, the steam turbine is operated to supply electricity.These devices make use of enhanced pressure of steam to rotate electric generators at extremely more speeds where the revolving speed of these are maximum than water turbines and wind turbines. [44], Machine that uses steam to rotate a shaft, "Turbine Steam Ship" redirects here. One type is called an impulse turbine. Throttle Governing Of Steam Turbine. 1 U 1 = = Blades move entirely due to the impact of steam on them and their profiles do not converge. Thus, conventional steam power is used in very few new ships. Since then, apart from getting bigger, turbine design has hardly changed and Parson's original design would not look out of place today. b Assuming that 2 b These arrangements include single casing, tandem compound and cross compound turbines. 2 By 1905, when steam turbines were coming into use on fast ships (such as HMS Dreadnought) and in land-based power applications, it had been determined that it was desirable to use one or more Curtis wheels at the beginning of a multi-stage turbine (where the steam pressure is highest), followed by reaction stages.
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