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IC Engine Part II

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Published in: Mechanical
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Presentation on IC Engine

Trinity A / Chandigarh

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Teaches: Indian National Mathematical Olympiad (INMO), Mental Maths, Olympiad Exam Preparation, Regional Mathematical Olympiad (RMO), Advanced Excel, Basic Computer, MS Office, School Level Computer, Mathematics, Statistics, Science, Social Studies, B.Tech Tuition, Drawing, Mechanical, AutoCAD Training, French, German, Study in Germany

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  1. Course Objective The course will prepare engineers to understand the concept & working of Internal combustion Engines to solve proble s related to engines. It will enhance ability to address ne problems in the rapidly changing technological scenario.
  2. IC Engines UNIT-2
  3. 2.1 IC Engine Fuels Fuels include a number of fuels besides gasoline for use in pas e vehicles. Ethanol E85 Methanol M85 Propane Compressed Natural Gas (CNG) er
  4. 2.1 BIODIESEL ' Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant greases. ' Biodiesel is safe, biodegradable, and reduces serious air pollutants such as particulate matter (PM), carbon monoxide, and hydrocarbons. MINING LOW SU (500 ppm sun WARN ) Federal law pt in model year 2 later highway ve and engines. ) Its use may daman vehicles and engin 'WAY PUSHTO PRE START STA USE IN ANY DIESEL VEHICLE Bio Diesel ooo•eset PETRCXEUM DIESEL
  5. Continued E-diesel, also called diesohol outside of the United Stat s, •s standard No. 2 diesel fuel that contains up to 15% ethanol. While E-diesel can have up to 15% ethanol by volume, typ cal blend levels are from 8% to 10%. Cetane Rating The higher the cetane number, the shorter the delay between injection and ignition. Normal diesel fuel has a cetane number of about 50.
  6. SYNTHETIC FUELS Synthetic fuels were first developed using the Fischer- Tropsch method and have been in use since the 1920s to convert coal, natural gas, and other fossil fuel products into a fuel that is high in quality and clean-burning. Coal to Liquid (CTL) Methanol to Gasoline Future of Synthetic Fuels COAL FISCHER. TROPSCH SYNTHESIS GASIFIER REFINING DIESEL LPG NAPTHA
  7. Petroleum refining process CRUDE DESALTING REFINING REFORMIN BLENDING Petroleum delivered from well field Water washing to remove impurities Distillation to separate by boiling point ranges Conversion reactions to alter molecular structures Mixing to obtain maximum commercial characteristics
  8. 2.3 Rating of Sl Engine Fuels: Resistance to knocking is an extremely important characteris •c of fuel for spark-ignition (SI) engines. These fuels differ widely in theor ability to resist knock depending on their chemical composition. A sati factory rating method for comparing the antiknock qualities of the variou fuels has been established. In addition to the chemical characteristl s of hydrocarbons in the fuel, other operating parameters such as engine speed, fuel-air ratio, ignition timing, dilution, shape of the combuslion chamber, compression ratio, ambient conditions, etc. affect the tendency to knock in the engine cylinder. Therefore, in order to determine the knock resistance characteristic of the fuels, the SI engine and its operating variables must be fixed at standard values.
  9. Theoretical calculation of calorific valu 1. Elements always combine in definite proportions to give. the products. For xa ple 12 gm of carbon combines with 32 gm of oxygen to give 44 gm of C02 C + C02 12 32 44 Similarly, 4gm of hydrogen combines with 32gm of oxygen to give 36gm of H20. 2 H2(g) + O(g) 2H20(g) 4 32 36 2. At STP (273 K, I atm) one mole of all gases occupy a volume of 22.41itres. Hence at S.T.P. 22.4 liters of C02 will have a weight of 44gm, its molecular weight. 3. Air contains 21 % of oxygen by volume and 23 % of oxygen by weight, Hence 1 m of oxygen will be supplied by I x 100 = 4.76m3 of air 21
  10. Abnormal Combustion in SI Engine Knock is the term used to describe a pinging noise emitted from a SI engine undergoing abnormal combustion. The noise is generated by shock waves produced in the cylinder w en unburned gas ahead of the flame auto-ignites. —20 TC 20 40 OCA (a) Normal combustion. spark 280BTC —20 TC 20 40 (b) Slight knock. spark 280BTC OCA —20 TC 20 40 spark 320BTC
  11. 2.6 FUEL SUPPLY SYSTEMS The fuel passes through a number of stages before reaching e combustion chamber. It includes the filtration and atomization of fuel into fine particles. It is necessary to atomize the fuel before entering into the combustion chamber so that complete combustion of fuel can take place. There are different fuel supply systems for spark ignition ( trol) and compression ignition (diesel) engine.
  12. Fuel Supply System Of SI Engine air filter •Carburetor Fuel tank Fuel filter with fuel pump To engine
  13. 2.8 CARBURETTOR Carburettor is the device that mixes petrol and air in correct propotions and supplies to the combustion chamber in right quantity. A Carburettor atomises, vaporises and mixes the petrol in correct propotions with air as required by the engine and supplies the right quantity of the mixture to the engine. air enters horn from fuel tank -............-+ needle I'dve float air and fuel mix at throat throttle Wve
  14. Construction and Working of Simp Carburettor Simple carburettor consist of a venturi and a fuel jet. For maintaining the level of fuel in the jet, a float chambe is usually required. A throttle valve in the form of a flat circular metal disc mounte on spindle is provided for controlling the flow of air-fuel mixture to the induction manifold. A rotary type valve also can be used instead of disc type.
  15. 2,10 Diesel Engine Fuel Injection Systems Functions of a Fuel injection system: Filter the fuel Measure the correct quantity of fuel to be injected Time the fuel injection Control the rate of fuel injection Atomize the fuel Distribute the fuel in the combustion chamber
  16. 2,11 Classification of injection systems Fuel Injection System Air Injection Airless Injection
  17. 2.12 Air Injection: In this method of fuel injection air is compressed in a compressor to high r ssure and injected into the fuel Nozzle. The rate of fuel admission can be controlled by varying the pressure f i •ection air. Advantages: It provides better atomization and distribution of the fuel As the combustion is more complete the BMEP is higher Inferior fuels can be used Disadvantages: It requires high pressure multi stage compression A separate mechanical linkage is required to time the operation of fuel val e Due to compression and linkage the size of the engine increases
  18. 2.13 Pump injection system In this system an individual pump or pump cylinder connects directly to each fuel nozzle. Pump meters charge and control injection timing. Nozzles contain a delivery valve actuated by the fuel oil pressure. Disadvantages . 'This system has to be designed accurately to pump small quantity of fuel High-pressure fuel lines Control rack Injection nozzles Pump with an individual cylinder for each nozzle Pump camshaft
  19. 2,14 Fuel Pump L is the plunger driven by a cam and tappet mechanism at the bottom . B is the barrel in which plunger reciprocates. There is a rectangular vertical groove in the plunger which extends from top to another helical groove. V is the delivery valve which lifts off its seat under the liquid fuel pressure and spring force. The fuel pump is connected to the fuel atomiser through passage P. SP and Y are the spill and the supply port respectively. When the plunger is at he bottom both ports SP and Y are uncovered by the plunger and fuel enters from the port SP into the barrel. Supply port (Y) Passage (P) Spring (S) Delivery valve (V) Barrel (B) Spill port (SP) Plunger (L) Rack (R)
  20. 2.15 Fuel Injector It consist of a nozzle valve(NV) fitted in the nozzle body (NB). The nozzle valve is held on its seat by a spring 'S' which exerts pressure through spindle E. 'AS' is the adjusting screw by which nozzle valve lift can be adjusted. Usually the nozzle valve is set to lift at 135 to 175 bars pressure. FP is the feeling pin which indicates whether valve is working properly or not Fuel Inlet • 20 macron fiber basket Return Spring üecrical connecton Hnte Valve Needle Ante Head & Seat
  21. 2.16 Fuel Filters A fuel filter is a filter in the fuel line that screens dirt and rust particles from the out fuel, normally made into cartridges containing a filter paper They are found in most internal combustion engines FUEL OUT RELIEF VALVE FUEL FUEL METAL OtSKS ORA' N PLUG
  22. 2.17 Flame Propagation As the flame propagates away from the spark plug the pressure and te erature of the unburned gas increases. Under certain conditions the end-gas can autoignite and burn vey pidly producing a shock wave flame shock end-gas time time 'The end-gas auto ignites after a certain induction time which is dictated by the chemical kinetics of the fuel-air mixture. 'If the flame burns all the fresh gas before auto ignition in the end-gas can occur then knock is avoided. 'Therefore knock is a potential problem when the burn time is Ion
  23. 2,18 Factors affecting the lag i) Compression ratio — at high compression ratios, even before spark igniti n, the fuel-air mixture is compressed to a high pressure and temperature which ro otes auto ignition ii) Engine speed — At low engine speeds the flame velocity is slow and thus t e burn time is long, this results in more time for auto ignition. However at ngine speeds there is less heat loss so the unburned gas temperature is higher hich promotes auto ignition. These are competing effects, some engines show an increase in propensity to knock at high speeds while others don't. iii) Spark timing — maximum compression from the piston advance occurs at TC, increasing the spark advance makes the end of combustion crank angle approach TC and thus get higher pressure and temperature in the unburned gas just before burnout.
  24. 2.19 Control & measurement of Knock To provide a standard measure of a fuel's ability to resist knock, a scale as been devised in which fuels are assigned an octane number ON. 'The octane number determines whether or not a fuel will knock in a given eng•ne under given operating conditions. 'By definition, normal heptane (n-C7H16) has an octane value of zero and isooctan (C8H18) has a value of 100. 'The higher the octane number, the higher the resistance to knock. 'Blends of these two hydrocarbons define the knock resistance of intermediate octane numbers: e.g., a blend of 10% n-heptane and 90% isooctane has an octane number f 90. 'A fuel's octane number is determined by measuring what blend of these two hydrocarbons matches the test fuel's knock resistance.
  25. 2,20 Anti knock agents An antiknock agent is a gasoline additive used to reduce and DCking increase the fuel's octane rating by raising the temperature and pres ur at which auto-ignition occurs. Typical agents The typical antiknock agents in use are: Tetraethyllead (Still in use as a high octane additive) Alcohol tricarbonyl (MMT) Ferrocene Iron pentacarbonyl Toluene Isooctane
  26. 2,21 Combustion Chamber in CI Engine In a CI engine the fuel is sprayed directly into the cylinder and the fuel-air mixture ignites spontaneously. 0.4 ms after ignition These photos are taken in a RCM under Cl engine conditions with swirl air flow 3.2 ms after ignition 3.2 ms after ignition Late in combustion process

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