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Note for Basics of Mechanical Engineering - BME By vtu rangers

  • Basics of Mechanical Engineering - BME
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  • Visvesvaraya Technological University Regional Center - VTU
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5uh NoU atE /;1 Module -L - 1 Energy S u ttAg. u Resources I:uarg-y llasourc(s: Non-rcn<'-walt/c: ontl re.newttbla cncrgy resoltrca.\, Petroleum based soiicl, liqLtitl atul :lrl'!(?orl's fitcl"s, Cllolorifc voluc.s o/'f.rcls, Contbu.ttictn ttntl combu.stion Ttrotlu<:ts of ftrts, Solar powcr: Solur Rotliotiort, Solor constont (rlefinition only), Solor Thermttl en(]rg)) harvc.sting, er: liquirl Jlot plate colleclors, soltrr pontls (principlg of opetoticttt onl1t.), 5n1n, phcttot,oltoic principle. ll/ind Power: principlegf operation o.f s 11'pic:ol ,,indntill. H),dro Potvet': Prhciple.s of clectric pohler generaliott h1,tl.1-6powar plartls, Nuclear ft-ont Pox'er: Prinr:iplas o.f' Nuclear pov,er plant.s, Bio Fuels: introduction tct bio Jircls, examptes of various biofucl's u's'etl itt enginte ring ttpplicariotts, Comparison of bioftrcls witlt pef?oleum .ftrcls in teent-s of calorific vttlua anrl cmissiotl. Stecm Fornration antl Prolterties: Classification of boilers, La"ncashfre boiler, Babcoclc ond ll/ilcox boi.lar, boiler mountins.s and acce-ssories (No slcett:hes .for mottntings anrl accessories), wet stearn, soturotci antl superhcat.ed steont, tpecific tolume, enthalpl, onrl internol energ)). IINERGY: Energy is definecl as the capacity to clo rvork. It is one of the primary ancl rnost universal llleasttres of all kinds ol wor-k- Hence, energy has been recognizecl as a key input parameter irr t5e der,elopment of a nation. - Most of the energy - tl.rat we use is nrainly clerivecl frorn conventional energy sources. L)ue to vast tleDland of energy, rate of depletion ol these resoulres has reachecl alamingly low levels. - 'l'his sitr-ration has clirected us to seek ahernate energy sources such as soiar, u,ind, oaean, biomass, hyilel etc. Sources of Euergy: '.. The energS, existing in the earlh is klorvn as CApITAL energy. '? cAPrrAL energy so*rces planets, moon are fossil filels, nuclear fuels ancl l.reat traps. enelgy from stars, etc. 1 E*ergy sources which are continuously produced in nature and inexhaustible are called renewable energy sources. l. Direct solar energy 4. Hydel 5. 6- Bio energy energy 9. Fuel rvood I l. Solid wastes 7. Geo thenlal essentially 2. Wind energy 3. Tidalenergy Ocean thermal energy arr energy B. peat 10. Fuel cells 12. Hydrogen Suhas U, Assistant Professor, Dept. Of Mechanical Ungg., CiT".h3engaluru page 1

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Nonrenewable Energy Sources: Energy sources which havc been accumulated over the ages ancl not quickly replenish able when they are exhausted. 1. Fossil fuels. 2. Nuclear fuels. 3. Heat traps. Advantages of Renelyable Energy Sources: 1. Non exhaustible. 2. can be matched in scale to the need and can deliver quarity energy, 3. Can be built near the load point. 4. Flexibility in the design of conversion systems. 5. Local self-sufficiency by harnessing locaily avairable renewable energy. 6. Except biomass, all other sources are pollution free. Disadvantages of Reneryable Energy Sources: 1- Intermittent nature of availability of energy such as solar, wind, tidal etc. is a major setback in thc continuous supply of energy. 2- Solar energy received at the earth is dependent on local armosphere conditions, time of the clay, part ofthe year etc. 3, Sources such as wind, tidal etc. are concentrated only in certain regions. 4. Technoiogy is not fully developed to meet the present energy requirements. 5. Systems such as soiar cells recluire advanced technologies and hence costlier" 6. Application to rranspoft sector has been found to be not viable as on today. Advantages of Non-Renewable Energy Sources: 1. Initial cost are lower. Hence widely used" 2. Unit power costs are much lower and so are economical 3. Sources are highly reliable. 4. Power generation technologies are rvell established. Disadvantages of Notr-Renervable Energy Sources: 1" . The Soqyc* are getting depleted and soon will be exhausted. 2. They pollute the atmosphere. 3. They are not freely available. Suhas u, Assistant Professor, Dept. of Mechanical Engg., cirech, Bengaluru Page 1

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PETROI,EUM BASED FUELS: Fottned niainly fiom ancient microscopic plants and bacteria that lived in the ocean and salt water seas. These micro-orgrnisrns died ancl settled to the sea flooq they mixed with sand silt to form organic rich mud which was gradually heated and compressqd chemically transforming into petroleum. The liquid petroleum which are less dense than water move upwards through earth's crust. It passes through an impetmeablc layer of rock which traps the petroleum creating a reservoir of petroleum and natural gas. Types of Fuels: The irnporlant fuels are as follorvs I) Soiid fuels 2) Liquid luels 3) Caseous fuels Solid fuels / / / coal is the major fuel used for thermal power plants to generate steam. CoaI occurs in nature, which was formed by the decay the earth millions of years ago under pressure and heat. of vegetable matters buried under ooo o This phenomenon of transformation of vegetable matter into coal under earth's erust is known as Metarnorphism. / The type of coal availatrle under the earth's surthce depends uporl the period of rnetamorphism and the type of vegetable matter buried, also the pressure and temperature conditions. / "' / The major constituents in coal moistr.rre {5-4OYo),r,olatile matter (combustible & or incombustible snbstances about 50%) and ash (20-50%). The chemical substances in the coal are carbon, hydrogen, nitrogen, oxygen and sulphur. In the metamorphism prrenomenon, the vegetabre matters undergo the transformation from peat to anthracite coal, with intermediate forms of lignite and bituminous coal. Liquid Fuels / / All / The cnrde oil is refined by fractional distillation process to obtain fuel oils, for industrial types of liquid fuels used are clerived from crude petroleum and its by-products. The petroleum or crude oil consists of 80-85% C,!}-l5%ohydrogen, and varying percantages sulpliuq nitrcgen, oxygen and compounds of vanadium. of as well as for domestic purposes. / / The fractions from light oil to heavy oil are naphtha, gasoline, kerosene, <liesel and finally heavy ftrel oil. The heavy fuel oil is used for generation of steam. The use of liquid fuels in thermal power plants has many advantages over the use of solid fuels. Suhas U, Assistant professor, Dept. Of Mechanical Engg., aiT Page 2

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/ For the generation of steam in gas fired thermal plants, either natural gas or manufactured gaseous fuels are used. However, manufactured gases are costlier than the natural gas. / { Generally, natural gas is used for power plants as it is available in abtmdance. The natural gas is generally obtained from gas wells and petroleum wells. The major constihrent in natural gas is methane, about 60-65 Yo, and also contains small amounts of other hydrocarbons such as ethane, naphthenic and aromatics, carbon clioxide and nitrogen. / The natural gas is transported from the source to the place ofuse through pipes, for distances to several hundred kilometres. / / Thenatural gas is colowless, odourless and non-toxic. Its calorific value ranges from 25,000 to 50,000 kJlm3, in accordance with the percentage of methane in the gas. { / { / Theartificial gases are producer gas, water gas coke-oven gas; and the Blast furnace gas. Generally, power plants fired with artificial gases are not found. The gaseous fuels have advantages similar problerns. The major disadvantage to those of liquid fuels, excel,t for the storage of power plant using natural gas is that it shoull be setup near the source; otherwise the transportation losses are too high. CALORIFIC VALUES OF FUELS: The calorific value or heat of combustion or heating value of a sample of fuel ir clefined as the amount of [eat evoolved when a unit weight ( or volume in the case of a sample of gaseo:rs fuels of the ) fuel is'comple&ly bumt.dt is expressed in kJlkg. Higher or Gross Calorific Value (HCV): It is the amount of heat energy liberated whert a unit quantity of fuel is burnt completely in air and the combustion products are cooled to the room temperature. Lower or Net Calorific Value (LCV): It is the amount of heat energy liberated when a unit quantity of fuel is burnt completely in air and the combustion products are released to the atmosphere. Combustion and Combustion Products: Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can produce light in the form of either glowing or a flame. Complete combustion of fuel is possible only in the presence ofan adequate supply ofoxygen. Oxygen (Oz) is one of the most common elements on earth making up 20.9Vo of our air. Rapicl fuel oxidation results in large amount of heat. Solid or liquid fuels must tre changed to a gas before they will burn in their normal state if enough air is present. Suhas u, Assistant Professor, Dept. of Mechanical Engg., cirech, Bengaluru Page 3

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