Powerful steam turbines for thermal stations: traditions, experience, innovations Speaker: Vitaliy Nedavniy, Design Engineer; Power Machines, the Branch LMZ, Russia Co-authors: Sergey Ivanov, Head of Calculations Department of Steam Turbines Andrey Belik, Chief of Thermal Calculation Steam Turbine Department To this date there are two kinds of companies that have a large park of steam turbines’ capacities – these are companies with rich tradition of turbine designing and manufacturing and companies, filling up their park with new power ranges via purchase of licenses. “Power Machines” (PM) company refers to the first one. Availability of developed history of steam turbines unit capacity growth creates a base of turbines of mean and high power on which base it is possible to design and introduce innovative solutions. Similar developmental history of the company PM-LMZ (branch of OJSC”PM” Leningradsky Metallichesky Zavod) is introduced on Fig.1. К-225-12,8-3Р К-500-240М К-330-240-Р К-300-240 К-800-240 К-1200-240 К-200-130 К-500-240 N tradition, MW P бар Т˚C Innovations Tradition К-660-240 К-660-265 Ultra supercritical steam conditions (p=260 bar, T=600˚C) Supercritical steam conditions (p=235 bar, T=560˚C) Supercritical steam conditions (p=235 bar, T=540˚C) Subcritical initial steam conditions (p=127.5bar,T=535˚C) Fig. 1 Development of powerful steam turbines PM-LMZ. 1
Transcript
Powerful steam turbines for thermal stations: traditions, experience, innovations
Speaker: Vitaliy Nedavniy, Design Engineer; Power Machines, the Branch LMZ, Russia Co-authors: Sergey Ivanov, Head of Calculations Department of Steam Turbines Andrey Belik, Chief of Thermal Calculation Steam Turbine Department To this date there are two kinds of companies that have a large park of steam turbines’ capacities – these are companies with rich tradition of turbine designing and manufacturing and companies, filling up their park with new power ranges via purchase of licenses. “Power Machines” (PM) company refers to the first one. Availability of developed history of steam turbines unit capacity growth creates a base of turbines of mean and high power on which base it is possible to design and introduce innovative solutions. Similar developmental history of the company PM-LMZ (branch of OJSC”PM” Leningradsky Metallichesky Zavod) is introduced on Fig.1.
К-225-12,8-3Р
К-500-240М
К-330-240-Р К-300-240
К-800-240
К-1200-240
К-200-130
К-500-240
N tradition, MW
P бар Т˚C
Innovations
Tradition
К-660-240 К-660-265
Ultra supercritical steam conditions (p=260 bar, T=600˚C)
Supercritical steam conditions (p=235 bar, T=560˚C)
Supercritical steam conditions (p=235 bar, T=540˚C)
Fig. 1 Development of powerful steam turbines PM-LMZ.
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Traditions. Development of high power steam turbines at the factory started in the middle of the XX
century, at the time of designing and manufacturing of steam turbines K-200-130 and turbines K-300-240. The first one is the representative of one of the largest turbine series in the world (data date 2010 it is produced 345 pieces), the second one possesses by one of the most relevant unit capacity to the present day.
Requirement that is imposed on condensing units of thermal stations in the course of whole steam turbine designing history is the growth of initial parameters, increasing turbine plant efficiency in whole. In such a way, historically innovations exist earlier, and last today. The example of last statement may serve the transition from subcritical initial conditions of steam turbine K-200-130, manufactured by PM-LMZ to the turbine initial conditions K-300-240. Initial pressure increased from 127,5 bar to 235 bar with temperature increase at the inlet from 535°C to 540°C (see Fig. 2 a, b)
Fig. 2а Steam turbine PM-LMZ К-200-130
Fig. 2b Steam turbine PM-LMZ К-300-240
Given circumstance required HPC construction changing – from single-casing to two-casing with loop scheme for the pressure difference reduction on the wall of outer cylinder. In its turn, for the purpose of gaining in performance and reduction of LPC axial overall dimensions replacement of Bauman stage 765mm to the stage 960mm was carried out, keeping single swept area and increasing blade material strength up to 700 MPa.
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Further unit capacity increase of the turbine plant was achieved by the way of live steam flow raising through the turbine under the corresponding construction change of the steam paths of HP and IP cylinders, and LP exhausts quantity, which was limited by the maximum length of the last stage moving blade (see Fig. 3)
In particular, changes during capacities transition from 300MW up to 800MW were accompanying by similar engineering changes:
• Flow path change of loop HPC – blades’ lengths’ increase; • IPC construction change - from single-casing to symmetrical two-casing; • LPC number increase (exhausts’ quantity).
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Fig. 3 Construction change of high power steam turbines, manufactured by PM Separate examinations claims transition from steam turbine K-800-240 to the turbine K-1200-
240. K-1200-240 is the world’s largest steam turbine for thermal station with unit capacity 1200MW, having unique construction, that had passed ahead of it’s time and is the illustration of traditions and experience of PM-LMZ in designing of powerful turbines. Turbine is operated at Kostromskaya GRES (Russia). (Fig. 4)
Construction began in 1975. In September 22, 1980 power unit with a capacity of 1200MW was put into operation
Fig. 4 Turbine mounting K-1200-240 at Kostromskaya GRES.
IPC LPC HPC
Turbine represents single-shaft 5-cylinder unit, consisting of HPC, IPC and three LPC. Construction of the turbine contains the following differences form the turbines of range 300-500-800 MW (Fig. 4 a,b):
1. Titanium blade 1200mm (unique blade as from the date of turbine manufacturing, in future it will define the possibility of steam turbine creation for NPP with a capacity of 1200MW);
2. Forged-welded rotors of LPC; 3. Outborne bearings (two supports), which rest directly upon the foundation.
Fig. 5а Steam turbine PM-LMZ К-800-240
Fig. 5b Steam turbine PM-LMZ К-1200-240
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Experience. “Power Machines” company has a wide reference of high power steam turbines for thermal
stations. (table 1) Table № 1 Steam turbine reference with a capacity of 500…1200 MW
Production year
Turbines Power plant name and country Capacity Initial pressure
1994-95 K-800-240-5 2 Suizhong China 800 23,5 540 540
1978 K-1200-240 1 Kostromskaya Russia 1200 23,5 540 540
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Altogether, there are installed 1 turbine with a capacity of 1200MW, 29 turbines of 800MW, 19 turbines of 500MW and in different stages (beginning with manufacturing and ending with mounting) 6 turbines having a capacity of 660MW. Total number of operating hours of the turbine 1200MW is 30 years of turbine operation, of the turbines 800MW - 329 years of turbine operation, of the turbines 500MW – 176 years of turbine operation. Given statistics tells us about high reference of the represented steam turbines.
Let us mention sequence of turbine creation with a capacity of 500MW. First turbine modification - K-500-166, designed for reduced steam parameters in contrast to turbine K-300-240, that is related to boilers, generating steam with inlet parameters p=163 bar, T=535˚C which the Customer has. Following this was designed turbine modification K-500-240 for the raised steam parameters – p=235 bar, T=540˚C.
First turbine modification K-800-240-1 was manufactured in a single copy as a twin-shaft unit with rotation speed of both shafts 50 Hz and successfully operated at Slavyanskaya GRES. Two-shaft unit performance (industry does not have generators with a capacity of 800MW) allowed to apply four double-flow LPC having last stage annular area equal to 7,48m, maximum at that time, and thus to have relatively small outlet losses, and high economical efficiency of whole turbine plant. However two-shaft unit was losing out to single-shaft unit because of enhanced cost of two electric generators in terms of technical-and-economic indicators.
After the first modification PM-LMZ had designed and manufactured single-shaft turbines K-800-240. At the moment there is the 5th turbine modification - К-800-240-5. During development and adjusting of the 5th modification a large attention was payed to raise the economical efficiency: heat rate reduces for more than 0,7%, according to PM-LMZ estimates, and in comparison with turbine K-800-23,5-3. Efficiency increase is provided by the modernized LPC steam path with shrouding of all blades and smoother peripheral meridian blade passage contour, by improved configuration of the outlet nozzle, by applying LP mixing heaters and another construction and schematic decisions. Maneuverability parameters are improved – approximately twice is reduced start-up time after long outage, and reliability, in particular, for more than 10% in comparison with regulated by the standard is raised guarantee mean time to failure. Measures, focused on providing higher reliability, such as control stage blades’ design, applying trough-shaped shrouds (leads to increase unit’s threshold power, on low-frequency vibration), heat expansion organization, increase operating time between overhaul repairs. Based on operating experience of previous modifications, fastening of the control stage nozzle segments is intensified. In comparison with 3-d modification turbine unit specific weight is reduced.
Maximum continuous output of the turbine is 850MW, at a cooling water temperature - 12°C Up to date PM company may offer deeply modified turbine K-800-240 with modernization of
HP, IP and LP flow paths, with changing rotors’ support construction, and with introduction of other modifications, considerably influencing the economical efficiency and reliability of steam turbine. Let us consider new main engineering solution in part of innovations.
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Innovations. Modernization represents the set of innovative engineering solution, which were founded only after getting the experience of turbine plant operation. So, for the turbine family 300-500-800MW it is possible to mark out general values:
• Flow path changing of HPC, IPC, LPC; • Design changing in HP rotor, IP rotor, LP rotor; • Modern sealings’ applications; • New support pads; • Application of heat-proof material for the variant with raised t0 и treheat (for the main
cylinders’ components of HP and IP); • Stop and control valves’ blocks replacement.
Let us consider solutions, applying in HP flow path (realized in project К-660-240 for TPP “Sipat” and “Barh”, India). (Fig.6)
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Fig. 6 Technical solutions in HP part
1 – piston rings with raised density level; 2 – nozzle boxes with low losses degree and even velocities diagram from steam admission to control stage; 3 – control stage with highly efficient overshroud sealing;
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4 – losses reducing in a control stage chamber at the expense of bypass profiling; 5 – optimal profile of the control stage disc; 6 – increased number of reactive type stages. General solutions on HP and IP – new design of the front seal (sleeve type). (Fig.7, 8)
1 High economical efficiency; 2 Geometric forms stability; 3 Clearances stability during operation; 4 Low labor content during mounting and operation.
Fig. 7 HP and IP front seal
Fig. 8 HPС front seal
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IIPPCC HHPPCC
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Application of highly efficient honeycomb overshroud seals (Fig. 9). (K-300-240 Kashirskaya GRES station 4. HPC and IPC)
Fig. 9 Honeycomb overshroud seals LP cylinders modernization with application of (Fig.10):
• LP rotor’s outborne bearings, placed on foundation; • LP rotor’s end bearings , installed on bearing cases; • double-tube steam admission, placed below the horizontal split; • steam release path, profiled on the base of swirl flow; • self-adjusting support pads Ø 475mm; • solid-forged five-stage rotor with T-shaped base (1-2stages) and fir-tree base (3-5
stages); • last stage steel moving blades 1000mm in length of improved reliability; • guide blades with tangential lean; • horizontal split hermetization of outer case; • quantity reduction of outer case contacts areas with foundation frames.
Fig.10 LP cylinders modernization
HHPPCC
IIPPCC
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Let us show at the example of turbine K-500-240-4M influence of given changes on the parameters of turbine families 300-500-800MW:
Table № 2 Turbine parameters К-500-240-4М with last stage blade 1000 mm. Parameter Dimensions Before modernization After modernization Turbine capacity increase at generatorterminals MW - + 37
Main steam pressure bar 235 260
Main steam/reheat temperature ˚С 540 / 540 560 / 565
Last stage moving blade length mm 960 1000
As the project of new turbine, in which given actions are realized, we present steam К-660-
247 (TPP “Sipat” and “Barh”). (Fig.11)
Rated capacity 660 MW Live steam temperature 537°С. Live steam pressure 242 bar
Reheat steam temperature 565°С Reheat steam pressure 47 bar Pressure in condenser 0,103 bar
Fig. 11 Turbine К-660-247 Let us mark modernization of LPC № 2 in turbine K-1200-240 Kostromskaya GRES.
• shrunk-on discs rotor replacement with the solid-forged rotor; • guide blades with tangential lean on the base of steam turbine К-1000-60/3000 for
“Kudankulam” NPP; • new moving blades on the base of К-1000-60/3000 for “Kudankulam” NPP;
Fig. 12 Replacement of LPC №2 steam turbine К-1200-240 Replacement of one of three LPC in steam turbine К-1200-240 gives the expected effect – 6
MW or 0,5% to the turbine capacity at a cooling water temperature of 12°С
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Today, PM-LMZ are developing preliminary design of new steam turbine K-660-26,5 for the operation as a part of coal-fired power unit with ultra supercritical parameters of live steam. The necessity of units building with high cycle efficiency is determined, on one side, by the requirements on reduction of the noxious emissions into the atmosphere, first, nitrogen oxides and greenhouse gases, on the other side, by the expensiveness of “noble” fuel (natural gas and black oil) and tendency of quality loss of the recovered solid fuel.
Live steam parameters at steam turbine inlet – pressure 210bar, temperature 610°C, reheat temperature 610°C. In order to reduce dimensions and metal consumption – overall dimensions are reduced at the expense of assembling application of the integrated HIPC + 1double-flow LPC. For providing high level of LPC economical efficiency there will be applied flow path with new blade for the increased steam flow.
For the purpose of achieving competitive level of steam turbine plant efficiency besides parameters increase of the working body at inlet it is necessary, that the steam turbine inner efficiency was at a very high level. For these purposes every component of the flow path of the new HIPC, including exhaust hoods, steam admissions, extraction ducts, is subjected to optimization. Fig. 13 shows the result of HIPC steam admission optimization.
Fig. 13 HIPC and IPC steam admission optimization of steam turbine К-660-26,5
Conclusion. Let us point out the importance of having large traditions and experience for Customer
providing by the full set of high-efficiency, reliable turbine equipment for TPP with following engineering and maintenance during operation. At the same time important for Customer is the unit cost reduction of 1MW at the expense of steam turbine mounting with large unit capacity (from 500MW). Today, the necessary competitiveness conditions of steam turbine manufacturer at the international market are: possession of referential constructions, introduction of innovative solutions into the mentioned constructions and making optimization in terms of parameters – economical efficiency, effectiveness and reliability.
At this date in operation there are 175 steam turbines manufactured by PM-LMZ at ultra supercritical steam parameters within the capacity range of 300MW-1200MW.
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PM-LMZ have large traditions, experience and innovative solutions, allowing to execute modernization of operating high capacity steam turbines, to have the possibility to create high economical efficient steam turbines for TPP with a capacity of 1200-1400MW, and to turn to serial manufacturing of ultra supercritical turbines an example of which became turbine K-660-26,5.
Operation guarantee of economical and reliable turbine plant of any capacity is the equipment purchase at the manufacturer, getting in the article mentioned requirements, to which PM company conforms.
