SUMMER TRAINING REPORT

TRAINING TAKEN AT - BHARAT HEAVY ELECTRICALS LIMITED (BHEL, BHOPAL)

SESSION – 2011-12 REPORT ON WATER TURBINE MANUFACTURING & STEAM TURBINE MANUFACTURING

UNDER GUIDANCE

MR. D. PRABHAKAR (DGM WTM BLOCK-1)

MR. D. D. PATHAK (AGM STM BLOCK-6)

SUBMITTED TO SUBMITTED BY

H. R. D. BHEL SHAILENDRA KUMAR SAHU

BHOPAL B.TECH (ME)

SIET GR.NOIDA

CERTIFICATE

This is to certify that SHAILENDRA KUMAR SAHU a student of SKYLINE INSTITUTE OF ENGINEERING & TECHNOLO-GY GR. NOIDA has successfully completed his summer training program with BHEL, Bhopal.

MR. D. PRABHAKAR

(DGM WTM BLOCK- 1) &

MR. D.D. PATHAK (AGM STM BLOCK-6)

ACKNOWLEDGEMENT

I am highly thankful to B.H.E.L for providing me the vital and much needed practical experience in the field of machine manufacturing.

I express my gratitude to Human Resource and Development department for giving me a chance to feel the industrial environment and its working in B.H.E.L and I am thankful to the B.H.E.L engineers and the technical staff for giving their precious time and helping us in understanding various aspects of machine manufacturing and their assembly. I am also thankful to my training co-coordinator Mr. D Prabhakar (DGM WTM block-1) & Mr. D. D. pathak (AGM STM Block-6) and his team for their kind support.

SHAILENDRA KUMAR SAHU B.TECH (ME) S.I.E.T. GR. NOIDA

INTRODUCTION –

BHEL was established more than 50 years ago when its first plant was setup inBhopal ushering in the indigenous Heavy Electrical Equipment Industry in India. Adream which has been more than realized with a well recognized track record ofperformance it has been earning profits continuously since 1971-72 and achieved aturnover of Rs 2,658 crore for the year 2007-08, showing a growth of 17 per cent over the previous year.

Bharat Heavy Electricals Limited is country’s ‘Navratna’ company andhas earned its place among very prestigious national and international companies. It findsplace among the top class companies of the world for manufacture of electricalequipments.

BHEL caters to core sectors of the Indian Economy viz., Power Generation's &Transmission, Industry, Transportation, Telecommunication, Renewable Energy,Defense, etc. BHEL has already attained ISO 9000 certification for quality management,and ISO 14001 certification for environment management and OHSAS – 18001certification for Occupational Health and Safety Management Systems. The Companytoday enjoys national and international presence featuring in the “Fortune

International-500” and is ranked among the top 10 companies in the world, manufacturing powergeneration equipment. BHEL is the only PSU among the 12 Indian companies to figurein “Forbes Asia Fabulous 50” list.

Probably the most significant aspect ofBHEL’s growth has been itsdiversification .The constant reorientation of the organization to meet the varied needs intime with a philosophy that has led to total development of a total capability fromconcepts to commissioning not only in the field of energy but also in industry andtransportation.

In the world power scene BHEL ranks among the top ten manufacturers of powerplant equipments not only in spectrum of products and services offered, it is right on top.BHEL‘s technological excellence and turnkey capabilities have won it worldwiderecognition. Over 40 countries in world over have placed orders with BHEL coveringindividual equipment to complete power stations on turnkey basis.

BHEL – A Brief Profile

BHEL is the largest engineering and manufacturing enterprise in India in theenergy related infrastructure sector today. The wide network of BHEL's 14manufacturing division, four power Sector regional centers, over 150 project sites, eightservice centers and 18 regional offices, enables the Company to promptly serve itscustomers and provide them with suitable products, systems and services – efficientlyand at competitive prices. The company contributes more than 75% of the nationalgrid.

BHEL has:- Installed equipment for over 1,00,000MW of power generation--- for

utilities captive and industrial users.

Supplied over 2, 25,000 MVA transformer capacity and otherequipment operating in transmission and distribution network up to400 kV (AC & DC).

Supplied over 25,000 motors with drive control systems to powerprojects, petrochemicals, refineries, steel, aluminum, fertilizers,cement plants etc.

Supplied Traction electrics and AC/DC locos to power over 12,000

kms railway network. Supplied over one million valves to power plants and other Industries

QUALITY POLICIES

Towards meeting its Quality Policy, BHEL is using the vehicle of Quality Management Systems, which are certified to ISO 9001:2000 series of Standards by Internationally acclaimed certifying agency, BVQI.

Corporate Quality and Unit level Quality structure enables requisite planning, control and implementation of Company-wide Quality Policy and Objectives which are linked to the Company's Vision statement. Corporate Quality derives strength from direct reporting to Chairman and Managing Director of the Company.

Other than traditional Quality functions, today the focus is on:

Propagating Quality Management Systems and Total Quality Management

Formulating, implementing and monitoring, "Improvement Plans" with focus on internal and external Customer Satisfaction

Investigations and preventive actions on Critical Quality Issues

Calibration and testing laboratories of BHEL are accredited under the National Accreditation Board for Calibration and Testing Laboratories (NABL) scheme of Laboratory Accreditation, which has got mutual recognition with Asia Pacific Laboratory Accreditation Conference and International Laboratory Accreditation Conference.

As a result of its thrust on quality and technology, BHEL enjoys national and international recognition in the form of Product Certification by International Bodies like ASME, API etc. and Plant Approvals by agencies like Lloyds Register of Shipping, U.K., Chief Controller of Explosives India, TUV Germany etc.

In its movement towards Business Excellence and with the objective of achieving International level of Quality, BHEL has adopted European Foundation for Quality Management (EFQM) model for Business Excellence. Through this model and annual self-assessment exercise, BHEL is institutionalizing continuous improvement in all its operations.

RESEARCH AND DEVELOPMENT

To remain competitive and meet customers' expectations, BHEL lays great emphasis on the continuous upgradation of products and related technologies, and development of new products. BHEL's commitment to advancement of technology is reflected in its involvement in the development of futuristic technologies like fuel cells and superconducting generators. BHEL's investment in R&D is amongst the largest in the corporate sector in India. During the year 2010-11, BHEL invested Rs.10, 050 Million on R&D efforts- 21% higher than the previous year.

R&D and technology development are of strategic importance to BHEL as it operates in a competitive environment where technology is a key driver. Technology development efforts undertaken by BHEL have led to the filing of patents and copyrights at the rate of nearly one a day, significantly enhancing the company's intellectual capital. In 2010-11, BHEL filed 303 patents and copyrights, enhancing the company's intellectual capital to 1,438 patents and copyrights filed, which are in productive use in the company's business. The year saw a massive growth in grant of patents and copyrights. A total of 91 patents and copyrights were granted during the year. Currently, 532 patents & copyrights are in force. Notably, BHEL has been ranked as the Number One company in India in terms of filing of patents by the Economic Times Intelligence Group.

Significantly, BHEL is one of the only four Indian companies and the only Indian Public Sector Enterprise figuring in 'The Global Innovation 1000' of Booz & Co., a list of 1,000 publicly-traded companies which are the biggest spenders on R&D in the world. BHEL has also won the coveted CII-Thompson Reuters Innovation Award 2010 in the 'Hi-tech Corporate' category. The award recognizes BHEL's innovation and entrepreneurship in India based on number of patents and efficiency and impact of innovation as measured by patent citations.

The company's Corporate R&D division at Hyderabad leads BHEL's research efforts in a number of areas of importance to BHEL's product range. Research and Product Development (RPD) centres at all its manufacturing divisions play a complementary role. BHEL has introduced, in the recent past, several state of the art products. Commercialization of products and systems developed by way of in-house Research and Development contributed Rs.77, 580 Million corresponding to around 18% to the company's total turnover in 2010-11.

In keeping with the National commitment to a clean environment, BHEL has developed the technology for Integrated Gasification Combined Cycle (IGCC) power plants and is pursuing the development of Advance Ultra Supercritical Thermal Power Plants in the country. BHEL is also actively working on a number of projects in futuristic areas like Clean Coal Technology, Nano Technology, Fuel Cells, Superconductivity and thin film solar cells, etc. to advance the development of technologies for power and industry sector. The engineering and technology character of the organization will be further enhanced with increased focus on innovation and R&D.

WTM BLOCK

Water turbine manufacturing block (block-1) is one of the biggest block in the BHEL complex. Hydro turbine and its associated components are machined and manufactured here. The entire block is divided into different bays.

BAY-1

It houses the following machines:

Deep drilling machine - Used to drill holes in the shaft. CNC lathe Planing machine Horizontal floor boring machine Vertical boring machine CNC vertical boring machine Radial drilling machine Slotting machine

Components machined:

Guiding piece Bush housing Guide bent stock Shaft Log for lever Sleeve Hexagonal screw head

BAY-2

It houses the following machines:

Vertical boring machine Table planing machine Lathe machine CNC end milling machine CNC horizontal table borer

Make-Craven Boring spindle diameter-130mm Maximum load capacity-12 tons

Horizontal boring machine Spindle diameter-88.9mm Swiveling table size-1067*1067mm Sliding table size-1676*1067mm Maximum facing head mill face-1219mm

CNC lathe machine

Components machined:

Rubber seal clamping ring Bottom cover plate Bush Guide vane Extension tube Deflector

GOVERNOR ASSEMBLY-Bay 2 also houses the governor assembly area .

BAY-3

It houses the following machines:

Vertical boring machine Table diameter-6705mm Maximum job diameter-7696mm Maximum capacity-90 tons

CNC vertical boring machine Runner blade turning machine

Maximum length of work-8000mm Maximum diameter that can be turned-4000mm Length of job that can be done-7200mm

Column boring machine

Table diameter-5523mm Maximum external diameter that can be machined-9000mm Stroke of RAM-3353mm Maximum capacity-100 tons

Components machined:

Top cover Inner turbine housing Spacer flange Pivoted ring cover Sealing flange Stay ring Runner blade

BAY-4

It houses the following machines:

Lathe machine CNC lathe machine Table planing machine End milling machine

Distance between columns-4242mm Maximum underbridge movement-3276mm Maximum length of machines-9144mm Maximum height upto vertical head-3200mm Maximum capacity-100 tons

Horizontal boring and milling machine Spindle diameter-203mm Traverse x-8992mm , y-4500mm , z-1981mm Minimum height of spindle centre to bed-760mm

Break lathe machine Sliding bed and centre height-1422mm Base plate and centre height-2108mm

Saddles rotation over sliding bed-2286mm Distance between centre-7621mm Length of sliding bed-9905mm Diameter of face plate-2438mm Weight capacity-50 tons

Vertical milling machine Height between spindle nose and table-660mm Spindle to face column-559mm

Slotting machine Maximum stroke -530mm Minimum stroke -190mm

Radial drilling machine Vertical boring machine CNC horizontal floor borer

Boring spindle diameter-200mm Column guide way-1050mm Headstock vertical movement-5000mm Spindle / rack movement-2000/1600mm Rotary table size-3150*3150mm

Components machined:

Trunion Sleeve screw Bottom sleeve Top cover

FABRICATION SHOP

BAY-5

It is the place where degreasing and fabrication work takes place. It houses the following machines:

Electro slag welding machine Job completed in one pass

For job of thickness 40-110mm single nose is used For job of thickness greater than 110mm double nose is

used Less defects as compared to manual arc welding

Oven Heating fuel-LPG Max. heating temperature-150 degree Celsius Max. size-W-5250mm Transformer tank assembly-H-5000mm

Components fabricated:

Distributor Pivot ring Transformer tank

BAY-6

It houses the following machines and equipment:

Manual arc welding Manual grinding Submerged arc welding

BAY-7

It houses the following machines:

Submerged arc welding Robotic arm welding Shot blast plant-Used for treating corroded parts Paint shop-Used to paint shot blasted components

Components fabricated:

Transformer tank

Spacer flange

Bay-8

It houses the heat exchanger and cooler assembly. Following machines are situated in this bay:

Lahar deep gun drilling machine Radial drilling machine Arboga CNC drilling machine Multispindle drilling machine

Traverse x-7000mm

y-8500mm

z-350mm

No. of spindles-8 Min. pitch-100mm Max.pitch-200mm Per spindle drilling capacity-40mm Spindle speed-71-1400 RPM Spindle feed-10-1000 mm/min No. of drilling motors-2

Lathe machine

Components machined:

Buffel Tube plate Sleeve

PRODUCT INFORMATION

HYDRO TURBINES:

FRANCIS TURBINE-

These are inward flow reaction turbine. Used when operating head is in the range of 30-500m. These are medium pressure turbine. Total machines -190 Megawatt capacity-5-165 MW Runner radius-1050-5250mm

PELTON TURBINE- These are impulse turbines which extract energy from the

impulse (momentum) of moving water. These are high pressure turbines Total machines-46 Head limit-245-1025m Megawatt limit-1.5-200 MW

KAPLAN TURBINE- The Kaplan turbine is a propeller-type water turbine which

has adjustable blades. These are reaction turbines The head ranges from 10-70 meters Output from 5 to 120 MW Runner diameters are between 2 and 8 meters Used in high-flow, low-head power production

HYDRO TURBINE GOVERNOR

Used to govern the speed of rotation of the runner such that the frequency of power generated is 50 Hz.

This is done by controlling the opening of guide vanes.

Water turbine

Kaplan turbine and electrical generator cut-away view.

The runner of the small water turbine

A water turbine is a rotary engine that takes energy from moving water.

Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy source.

History

Water wheels have been used for thousands of years for industrial power. Their main shortcoming is size, which limits the flow rate and head that can be harnessed. The migration from water wheels to modern turbines took about one hundred years. Development occurred during the Industrial revolution, using scientific principles and methods. They also made extensive use of new materials and manufacturing methods developed at the time.

Swirl

The word turbine was introduced by the French engineer Claude Bourdin in the early 19th century and is derived from the Latin word for "whirling" or a "vortex". The main difference between early water turbines and water wheels is a swirl component of the water which passes energy to a spinning rotor. This additional component of motion allowed the turbine to be smaller than a water wheel of the same power. They could process more water by spinning faster and could harness much greater heads. (Later, impulse turbines were developed which didn't use swirl).

Time line

Roman turbine mill at Chemtou, Tunisia. The tangential water inflow of the millrace made the submerged horizontal wheel in the shaft turn like a true turbine.

A Francis turbine runner, rated at nearly one million hp (750 MW), being installed at the Grand Coulee Dam, United States.

A propeller-type runner rated 28,000 hp (21 MW)

The earliest known water turbines date to the Roman Empire. Two helix-turbine mill sites of almost identical design were found at Chemtou and Testour, modern-day Tunisia, dating to the late 3rd or early 4th century AD. The horizontal water wheel with angled blades was installed at the bottom of a water-filled, circular shaft. The water from the mill-race entered tangentially the pit, creating a swirling water column which made the fully submerged wheel act like a true turbin.

Ján Andrej Segner developed a reactive water turbine in the mid-18th century. It had a horizontal axis and was a precursor to modern water turbines. It is a very simple machine that is still produced today for use in small hydro sites. Segner worked with Euler on some of the early mathematical theories of turbine design.

In 1820, Jean-Victor Poncelet developed an inward-flow turbine.

In 1826, Benoit Fourneyron developed an outward-flow turbine. This was an efficient machine (~80%) that sent water through a runner with blades curved in one dimension. The stationary outlet also had curved guides.

In 1844, Uriah A. Boyden developed an outward flow turbine that improved on the performance of the Fourneyron turbine. Its runner shape was similar to that of a Francis turbine.

In 1849, James B. Francis improved the inward flow reaction turbine to over 90% efficiency. He also conducted sophisticated tests and developed engineering methods for water turbine design. The Francis turbine, named for him, is the first modern water turbine. It is still the most widely used water turbine in the world today. The Francis turbine is also called a radial flow turbine, since water flows from the outer circumference towards the centre of runner.

Inward flow water turbines have a better mechanical arrangement and all modern reaction water turbines are of this design. As the water swirls inward, it accelerates, and transfers energy to the runner. Water pressure decreases to atmospheric, or in some cases subatmospheric, as the water passes through the turbine blades and loses energy.

Around 1890, the modern fluid bearing was invented, now universally used to support heavy water turbine spindles. As of 2002, fluid bearings appear to have a mean time between failures of more than 1300 years.

Around 1913, Viktor Kaplan created the Kaplan turbine, a propeller-type machine. It was an evolution of the Francis turbine but revolutionized the ability to develop low-head hydro sites.

A new concept

Figure from Pelton's original patent (October 1880)Main article: Pelton wheel

All common water machines until the late 19th century (including water wheels) were basically reaction machines; water pressure head acted on the machine and produced work. A reaction turbine needs to fully contain the water during energy transfer.

In 1866, California millwright Samuel Knight invented a machine that took the impulse system to a new level. Inspired by the high pressure jet systems used in hydraulic mining in the gold fields, Knight developed a bucketed wheel which captured the energy of a free jet, which had converted a high head (hundreds of vertical feet in a pipe or penstock) of water to kinetic energy. This is called an impulse or tangential turbine. The water's velocity, roughly twice the velocity of the bucket periphery, does a u-turn in the bucket and drops out of the runner at low velocity.

In 1879, Lester Pelton (1829-1908), experimenting with a Knight Wheel, developed a double bucket design, which exhausted the water to the side, eliminating some energy loss of the Knight wheel which exhausted some water back against the center of the wheel. In about 1895, William Doble improved on Pelton's half-cylindrical bucket form with an elliptical bucket that included a cut in it to allow the jet a cleaner bucket entry. This is the modern form of the Pelton turbine which today achieves up to 92% efficiency. Pelton had been quite an effective promoter of his design and although Doble took over the Pelton company he did not change the name to Doble because it had brand name recognition.

Turgo and Crossflow turbines were later impulse designs.

Theory of operation

Flowing water is directed on to the blades of a turbine runner, creating a force on the blades. Since the runner is spinning, the force acts through a distance (force acting through a distance is the definition of work). In this way, energy is transferred from the water flow to the turbine

Water turbines are divided into two groups; reaction turbines and impulse turbines.

The precise shape of water turbine blades is a function of the supply pressure of water, and the type of impeller selected.

Reaction turbines

Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow.

Newton's third law describes the transfer of energy for reaction turbines.

Most water turbines in use are reaction turbines and are used in low (<30m/98 ft) and medium (30-300m/98–984 ft) head applications. In reaction turbine pressure drop occurs in both fixed and moving blades.

Impulse turbines

Impulse turbines change the velocity of a water jet. The jet pushes on the turbine's curved blades which changes the direction of the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.

Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a housing for operation.

Newton's second law describes the transfer of energy for impulse turbines.

Impulse turbines are most often used in very high (>300m/984 ft) head applications .

Power

The power available in a stream of water is;

where:

P = power (J/s or watts) η = turbine efficiency

ρ = density of water (kg/m³)

g = acceleration of gravity (9.81 m/s²)

h = head (m). For still water, this is the difference in height between the inlet and outlet surfaces. Moving water has an additional component added to account for the kinetic energy of the flow. The total head equals the pressure head plus velocity head.

= flow rate (m³/s)

Pumped storage

Some water turbines are designed for pumped storage hydroelectricity. They can reverse flow and operate as a pump to fill a high reservoir during off-peak electrical hours, and then revert to a turbine for power generation during peak electrical demand. This type of turbine is usually a Deriaz or Francis in design.

Efficiency

Large modern water turbines operate at mechanical efficiencies greater than 90% (not to be confused with thermodynamic efficiency).

Types of water turbines

Various types of water turbine runners. From left to right: Pelton Wheel, two types of Francis Turbine and Kaplan Turbine

Reaction turbines:

Francis Kaplan, Propeller, Bulb, Tube, Straflo

Tyson

Gorlov

Impulse turbine

Waterwheel Pelton

Turgo

Michell-Banki (also known as the Crossflow or Ossberger turbine)

Jonval turbine

Reverse overshot water-wheel

Archimedes' screw turbine

Design and application

Turbine selection is based mostly on the available water head, and less so on the available flow rate. In general, impulse turbines are used for high head sites, and reaction turbines are used for low head sites. Kaplan turbines with adjustable blade pitch are well-adapted to wide ranges of flow or head conditions, since their peak efficiency can be achieved over a wide range of flow conditions.

Small turbines (mostly under 10 MW) may have horizontal shafts, and even fairly large bulb-type turbines up to 100 MW or so may be horizontal. Very large Francis and Kaplan machines usually have vertical shafts because this makes best use of the available head, and makes installation of a generator more economical. Pelton wheels may be either vertical or horizontal shaft machines because the size of the machine is so much less than the available

head. Some impulse turbines use multiple water jets per runner to increase specific speed and balance shaft thrust.

Typical range of heads

• Hydraulic wheel turbine• Archimedes' screw turbine• Kaplan• Francis• Pelton• Turgo

0.2 < H < 4 (H = head in m)1 < H < 102 < H < 4010 < H < 35050 < H < 130050 < H < 250

Specific speed

The specific speed ns of a turbine characterizes the turbine's shape in a way that is not related to its size. This allows a new turbine design to be scaled from an existing design of known performance. The specific speed is also the main criteria for matching a specific hydro site with the correct turbine type. The specific speed is the speed with which the turbine turns for a particular discharge Q, with unit head and thereby is able to produce unit power.

Affinity laws

Affinity Laws allow the output of a turbine to be predicted based on model tests. A miniature replica of a proposed design, about one foot (0.3 m) in diameter, can be tested and the laboratory measurements applied to the final application with high confidence. Affinity laws are derived by requiring similitude between the test model and the application.

Flow through the turbine is controlled either by a large valve or by wicket gates arranged around the outside of the turbine runner. Differential head and flow can be plotted for a number of different values of gate opening, producing a hill diagram used to show the efficiency of the turbine at varying conditions.

Runaway speed

The runaway speed of a water turbine is its speed at full flow, and no shaft load. The turbine will be designed to survive the mechanical forces of this speed. The manufacturer will supply the runaway speed rating.

Maintenance

A Francis turbine at the end of its life showing cavitation pitting, fatigue cracking and a catastrophic failure. Earlier repair jobs that used stainless steel weld rods are visible.

Turbines are designed to run for decades with very little maintenance of the main elements; overhaul intervals are on the order of several years. Maintenance of the runners and parts exposed to water include removal, inspection, and repair of worn parts.

Normal wear and tear includes pitting from cavitation, fatigue cracking, and abrasion from suspended solids in the water. Steel elements are repaired by welding, usually with stainless steel rods. Damaged areas are cut or ground out, then welded back up to their original or an improved profile. Old turbine runners may have a significant amount of stainless steel added this way by the end of their lifetime. Elaborate welding procedures may be used to achieve the highest quality repairs.

Other elements requiring inspection and repair during overhauls include bearings, packing box and shaft sleeves, servomotors, cooling systems for the bearings and generator coils, seal rings, wicket gate linkage elements and all

surfaces

Steam turbineA steam turbine is a mecanical dhevice that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884.

It has almost completely replaced the reciprocating piston steam engine primarily because of its greater thermal efficiency and higherpower-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 80% of all electricity generation in the world is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process.

History

The first device that may be classified as a reaction steam turbine was little more than a toy, the classic Aeolipile, described in the 1st century by Greekmathematician Hero of Alexandria in Roman Egypt. More than a thousand years later, in 1543, Spanish naval officer Blasco de Garay used a primitive steam machine to move a ship in the port of Barcelona. In 1551, Taqi al-Din in Ottoman Egypt described a steam turbine with the practical application of rotating a spit. Steam turbines were also described by the Italian Giovanni Branca (1629) and John Wilkins in England (1648). The devices described by al-Din and Wilkins are today known as steam jacks.

A sort of steam turbine was also used by the Flemish Jesuit Ferdinand Verbiest to propell his steam car in 1672. as a gift to the Chinese emperor.

The modern steam turbine was invented in 1884 by the Englishman Sir Charles Parsons, whose first model was connected to a dynamo that generated 7.5 kW (10 hp) of electricity. The invention of Parson's steam turbine made cheap and plentiful electricity possible and revolutionised marine transport and naval warfare. His patent was licensed and the turbine scaled-up shortly after by an American, George Westinghouse. The Parson's turbine also turned out to be easy to scale up. Parsons had the satisfaction of seeing his invention adopted for all major world power stations, and the size of generators had increased from his first 7.5 kW set up to units of 50,000 kW capacity. Within Parson's lifetime the generating capacity of a unit was scaled up by about 10,000 times, 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.

A number of other variations of turbines have been developed that work effectively with steam. The de Laval turbine (invented by Gustaf de Laval) accelerated the steam to full speed before running it against a turbine blade. Hence the (impulse) turbine is simpler, less expensive and does not need to be pressure-proof. It can operate with any pressure of steam, but is considerably less efficient.

Cut away of an AEG marine steam turbine circa 1905

One of the founders of the modern theory of steam and gas turbines was also Aurel Stodola, a Slovak physicist and engineer and professor at Swiss Polytechnical Institute (now ETH) in Zurich. His mature work was Die Dampfturbinen und ihre Aussichten als Wärmekraftmaschinen (English The Steam Turbine and its perspective as a Heat Energy Machine) which was published in Berlin in 1903. In 1922, in Berlin, was published another important bookDampf und Gas-Turbinen (English Steam and Gas Turbines).

The Brown-Curtis turbine which had been originally developed and patented by the U.S. company International Curtis Marine Turbine Company was developed in the 1900s in conjunction with John Brown & Company. It was used in John Brown's merchant ships and warships, including liners and Royal Navy warships.

Types

Steam turbines are made in a variety of sizes ranging from small <1 hp (<0.75 kW) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 2,000,000 hp (1,500,000 kW) turbines used to generate electricity. There are several classifications for modern steam turbines.

Steam supply and exhaust conditions

These types include condensing, non condensing, reheat, extraction and induction.

Non condensing or back pressure turbines are most widely used for process steam applications. The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure. These are commonly found at refineries, district heating units, pulp and paper plants, and desalination facilities where large amounts of low pressure process steam are available.

Condensing turbines are most commonly found in electrical power plants. These turbines exhaust steam in a partially condensed state, typically of a quality near 90%, at a pressure well below atmospheric to a condenser.

Reheat turbines are also used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.

Extracting type turbines are common in all applications. In an extracting type turbine, steam is released from various stages of the turbine, and used for industrial process needs or sent to boiler feed water heaters to improve overall

cycle efficiency. Extraction flows may be controlled with a valve, or left uncontrolled.

Induction turbines introduce low pressure steam at an intermediate stage to produce additional power.

Casing or shaft arrangements

These arrangements include single casing, tandem compound and cross compound turbines. Single casing units are the most basic style where a single casing and shaft are coupled to a generator. Tandem compound are used where two or more casings are directly coupled together to drive a single generator. A cross compound turbine arrangement features two or more shafts not in line driving two or more generators that often operate at different speeds. A cross compound turbine is typically used for many large applications.

Principle of operation and design

An ideal steam turbine is considered to be an isentropic process, or constant entropy process, in which the entropy of the steam entering the turbine is equal to the entropy of the steam leaving the turbine. No steam turbine is truly “isentropic”, however, with typical isentropic efficiencies ranging from 20%-90% based on the application of the turbine. The interior of a turbine comprises several sets of blades, or “buckets” as they are more commonly referred to. One set of stationary blades is connected to the casing and one set of rotating blades is connected to the shaft. 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.

An ideal steam turbine is considered to be an isentropic process, or constant entropy process, in which the entropy of the steam entering the turbine is equal to the entropy of the steam leaving the turbine. No steam turbine is truly “isentropic”, however, with typical isentropic efficiencies ranging from 20%-90% based on the application of the turbine. The interior of a turbine comprises several sets of blades, or “buckets” as they are more commonly referred to. One set of stationary blades is connected to the casing and one set of rotating blades is connected to the shaft. 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.

Turbine efficiencyTo maximize turbine efficiency the steam is expanded, doing work, in a number of stages. These stages are characterized by how the energy is extracted from them and are known as either impulse or reaction turbines. 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. Typically, higher pressure sections are impulse type and lower pressure stages are reaction type.

Impulse turbines

An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage.

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). Due to this higher ratio of expansion of steam in the nozzle the steam leaves the nozzle with a very high velocity. The steam leaving the moving blades has a large portion of the maximum velocity of the steam when leaving the nozzle. The loss of energy due to this higher exit velocity is commonly called the "carry over velocity" or "leaving loss".

Reaction turbines

In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.

Operation and maintenance

When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion. 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 to 15 RPM to slowly warm the turbine.

Operation and maintenance

When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion. 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 to 15 RPM to slowly warm the turbine.

Speed regulation

The control of a turbine with a governor is essential, as turbines need to be run up slowly, to prevent damage while some applications (such as the generation of alternating current electricity) require precise speed control. Uncontrolled acceleration of the turbine rotor can lead to an overspeed trip, which causes the nozzle valves that control the flow of steam to the turbine to close. If this fails then the turbine may continue accelerating until it breaks apart, often spectacularly. Turbines are expensive to make, requiring precision manufacture and special quality materials. During normal operation in synchronization with the electricity network, power plants are governed with a five percent droop speed control. This means the full load speed is 100% and the no-load speed is 105%. This is required for the stable operation of the network without hunting and drop-outs of power plants. Normally the changes in speed are minor. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. 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.

Thermodynamics of steam turbines

The steam turbine operates on basic principles of thermodynamics using the part of the Rankine cycle. Superheated vapor (or dry saturated vapor, depending on application) enters the turbine, after it having exited the boiler, at high temperature and high pressure. The high heat/pressure steam is converted into kinetic energy using a nozzle (a fixed nozzle in an impulse type turbine or the fixed blades in a reaction type turbine). Once the steam has exited the nozzle it is moving at high velocity and is sent to the blades of the turbine. A force is created on the blades due to the pressure of the vapor on the blades causing them to move. A generator or other such device can be placed on the shaft, and the energy that was in the vapor can now be stored and used. The gas exits 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.[13] If we look at the first law we can find an equation comparing the rate at which work is developed per unit mass. Assuming there is no heat transfer to the surrounding environment and that the change in kinetic and potential energy is negligible when compared to the change in specific entropy we come up with the following equation

Ẇt is the rate at which work is developed per unit time ṁ is the rate of mass flow through the turbine

Isentropic turbine efficiency

Rankine cycle with superheatProcess 1-2: The working fluid is pumped from low to high pressure.Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapor.Process 3-3': The vapour is superheated.Process 3-4 and 3'-4': The dry saturated vapor expands through a turbine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur.Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant pressure to become a saturated liquid.

To measure how well a turbine is performing we can look at the isentropic efficiency. Isentropic efficiencies involve a comparison between the actual performance of a device and the performance that would be achieved under idealized circumstances. When calculating the isentropic efficiency, heat to the surroundings is assumed to be zero. The starting pressure and temperature is the same for both the isentropic and actual efficiency. Since state 1 is the same for both efficiencies, the specific enthalpy h1 is known. The specific entropy for the isentropic process is greater than the specific entropy for the actual process due to irreversibility in the

process. The specific entropy is evaluated at the same pressure for the actual and isentropic processes in order to give a good comparison between the two.

The isentropic efficiency is given to us as the actual work divided by the maximum work that could be achieved if there were no irreversibly in the process.

.

h1 is the specific enthalpy at state one h2 is the specific enthalpy at state two for an actual process

h2s is the specific enthalpy at state two for an isentropic process

Calculating turbine efficiency

The efficiency of the steam turbine can be calculated by using the Kelvin statement of the Second law of Thermodynamics.

.

Wcycle is the Work done during one cycle QH is the Heat transfer received from the heat source

If we look at the Carnot cycle the maximum efficiency of a steam turbine can be calculated. This efficiency can never be achieved in the real world due to irreversibility during the process, but it does give a good measure as to how a particular turbine is performing.

.

TL is the absolute temperature of the vapor moving out of the turbine

TH is the absolute temperature of the vapor coming from the boiler

Direct drive

A small industrial steam turbine (right) directly linked to a generator (left). This turbine generator set of 1910 produced 250 kW of electrical power.

Electrical power stations use large steam turbines driving electric generators to produce most (about 80%) of the world's electricity. The advent of large steam turbines made central-station electricity generation practical, since reciprocating steam engines of large rating became very bulky, and operated at slow speeds. Most central stations are fossil fuel power plants and nuclear power plants; some installations usegeothermal steam, or use concentrated solar power (CSP) to create the steam. Steam turbines can also be used directly to drive largecentrifugal pumps, such as feedwater pumps at a thermal power plant.

The turbines used for electric power generation are most often directly coupled to their generators. As the generators must rotate at constant synchronous speeds according to the frequency of the electric power system, the most common speeds are 3000 RPM for 50 Hz systems, and 3600 RPM for 60 Hz systems. Since nuclear reactors have lower temperature limits than fossil-fired plants, with lower steam quality, the turbine generator sets may be arranged to operate at half these speeds, but with four-pole generators, to reduce erosion of turbine blades.

Marine propulsion

The Turbinia, 1894, the first steam turbine-powered ship

In ships, compelling advantages of steam turbines over reciprocating engines are smaller size, lower maintenance, lighter weight, and lower vibration. A steam turbine is only efficient when operating in the thousands of RPM, while the most effective propeller designs are for speeds less than 100 RPM; consequently, precise (thus expensive) reduction gears are usually required, although several ships, such as Turbinia, had direct drive from the steam turbine to the propeller shafts. Another alternative is turbo-electric drive, where 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. The purchase cost is offset by much lower fuel and maintenance requirements and the small size of a turbine when compared to a reciprocating engine having an equivalent power. However, diesel engines are capable of higher efficiencies: propulsion steam turbine cycle efficiencies have yet to break 50%, yet diesel engines routinely exceed 50%, especially in marine applications.[16][17][18]

Nuclear-powered ships and submarines use a nuclear reactor to create steam. Nuclear power is often chosen where diesel power would be impractical (as in submarine applications) or the logistics of refuelling pose significant problems (for example, icebreakers). It has been estimated that the reactor fuel for the Royal Navy's Vanguard class submarine is sufficient to last 40 circumnavigations of the globe – potentially sufficient for the vessel's entire service life. 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 fuel cycles.

Locomotives

A steam turbine locomotive engine is a steam locomotive driven by a steam turbine.

The main advantages of a steam turbine locomotive are better rotational balance and reduced hammer blow on the track. However, a disadvantage is less flexible power output power so that turbine locomotives were best suited for long-haul operations at a constant output power.

The first steam turbine rail locomotive was built in 1908 for the Officine Meccaniche Miani Silvestri Grodona Comi, Milan, Italy. In 1924 Krupp built the steam turbine locomotive T18 001, operational in 1929, for Deutsche Reichsbahn.

CONLUSIONThe Vocational training at BHEL Bhopal helped me in improving my practical knowledge and awareness regarding Hydro turbine and heat exchanger to a large extent.

Here I came to know about the technology and material used in manufacturing of hydro turbine and heat exchanger. Besides this, I also visualized the parts involved or equipments used in the power generation. In all it was a truly learning experience.