Seminar report on modifications for ethanol engines


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Seminar report on modifications for ethanol engines

  1. 1. SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND MANAGEMENT, KATOL ROAD, NAGPUR, INDIA -440013 Department of Mechanical Engineering 2012-2013 Technical Seminar Report On“MODIFICATIONS IN GASOLINE ENGINES FOR USE OF ETHANOL FUEL” Submitted by Sughosh D. Deshmukh Under the guidance of Prof. M. P. Joshi 1
  2. 2. SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND MANAGEMENT, NAGPUR, INDIA-440013 Department of Mechanical Engineering CERTIFICATE This is to certify that Sughosh D. Deshmukh has completed the technicalseminar work on “Modifications in gasoline engines for use ofethanol fuel” in partial fulfilment of the requirements of fifth semester B.E. inMechanical Engineering as prescribed by Rashtrasant Tukdoji Maharaj NagpurUniversity at S.R.C.E.M., Nagpur.Prof. M. P. Joshi Prof. M. M. GuptaSeminar Guide H.O.D.Mechanical Engineering Department Mechanical Engineering Department 2
  3. 3. Acknowledgement I am thankful to my guide Prof. M. P. Joshi whose personal enrolment inthe technical seminar presentation and report has been a major source ofinspiration for me to be flexible in my approach and thinking for tacklingvarious issues. He assumes the critical role of ensuring that I am always on theright track. I also extend my gratitude to Prof. M. M. Gupta (H.O.D, MechanicalDept.) without whose support, co-operation and guidance this paperpresentation would not have been a success. Last but not the least we would like to say a big thanks to all the staff andassistants of mechanical department.Prof. M. P. Joshi Prof. M. M. GuptaSeminar Guide H.O.D. 3
  4. 4. Abstract The prices of fuels are rising to new heights day after day. Driving forpleasure has been a thing of past. The need for using some alternatives forgasoline or diesel fuel is the need of the hour. Some alternative fuels like CNG, LPG, LNG, Hydrogen gas, Alcohols,biodiesel etc are thought of after petrol and diesel. One such alternative fuel thatcan be used in place of petrol especially is ethanol fuel. Due to differences in the properties of ethanol fuel and gasoline fuel, theengine designed for gasoline fuel cannot be used for ethanol fuel directly. Thereare some modifications that are needed in the engine for use of ethanol fuel. This report tries to explain some such modifications which are necessaryin gasoline engine for the use of ethanol fuel. 4
  5. 5. Index1. Introduction to ethanol and properties----------------------------------72. Comparison between different fuels ------------------------------------83. Modifications --------------------------------------------------------------9 3.1. Mainjet changes-------------------------------------------------------10 3.2. Idle orifice changes---------------------------------------------------11 3.3. Power valve changes-------------------------------------------------12 3.4. Accelerator pump changes-------------------------------------------13 3.5. Compression ratio changes------------------------------------------14 3.6. Cold weather starting-------------------------------------------------16 3.7. Thermostat changes---------------------------------------------------174. Initial use of alcohol fuel-------------------------------------------------185. Fuel injection systems-----------------------------------------------------196. Benefits of using ethanol fuel--------------------------------------------207. Disadvantages of ethanol fuel--------------------------------------------218. Common ethanol fuel mixtures------------------------------------------229. Conclusion-----------------------------------------------------------------2310. References------------------------------------------------------------------24 5
  6. 6. List of figures and tablesFig. 1: Main jet orificeFig. 2: Idle orifice jetFig. 3: Power valveFig. 4: Accelerator pump jetsFig. 5: High compression pistonFig. 6: Milled pistonFig. 7: A turbochargerFig. 8: air pre heater schematicFig. 9: ethanol percentages.Table 1: comparison between calorific value of different fuels.Table 2: modification in parts 6
  7. 7. Introduction to ethanol Ethanol is the systematic name defined by the IUPAC nomenclature oforganic chemistry for a molecule with two carbon atoms (prefix "eth-"), havinga single bond between them (suffix "-ane"), and an attached -OH group (suffix"-ol"). It is a volatile, flammable, and colourless liquid. Best known useof ethanol is found in alcoholic beverages, it is also used in thermometers, asa solvent, and as a fuel. In common usage, it is often referred to simplyas alcohol or spirits. The molar mass of ethanol is 46.07 g/mol. The density ofethanol is 0.785 g/cm3. Heat of vaporization is 840 kJ/kg. Ethanol has a boiling point of 78.37 oC and melting point of -114 oC Thevapour pressure at 20 oC is 5.95 KPa. Viscosity of the compound at 20 oC is0.0012 Pa-s. Ethanol is a versatile solvent, miscible with water and with many organicsolvents,including aceticacid, acetone, benzene, carbontetrachloride, chloroform, ethylene glycol, glycerol, nitro methane, and toluene. It is also miscible withlight aliphatic hydrocarbons, such as pentane and hexane, and with aliphaticchlorides such as trichloroethane and tetrachloroethylene. Ethanols miscibility with water contrasts with the immiscibility oflonger-chain alcohols (five or more carbon atoms), whose water miscibilitydecreases sharply as the number of carbons increases. Ethanol-water mixtures have less volume than the sum of their individualcomponents at the given fractions. Ethanol has a high self ignition temperature of around 326 oC, ascompared to petrol (240-280 oC) or diesel (210 oC). 7
  8. 8. Comparison between different fuels The following table gives the properties of various compounds, whichcan be used as fuels. Research Fuel type MJ/L MJ/kg octane numberDry wood (20% moisture) - ~19.5 -Methanol 17.9 19.9 108.7Ethanol 21.2 26.8 108.6E85 25.2 33.2 105(85% ethanol, 15%gasoline)Liquefied natural gas 25.3 ~55 -Autogas (LPG) 26.8 50 -(60% propane +40% butane)Aviation gasoline 33.5 46.8 100/130 (lean/rich)(high-octane gasoline, notjet fuel)Gasohol 33.7 47.1 93/94(90% gasoline + 10%ethanol)Regular gasoline/petrol 34.8 44.4 min. 91Premium gasoline/petrol max. 104Diesel 38.6 45.4 25Charcoal, extruded 50 23 - Table 1: Comparison between calorific value of different fuels.Octane rating is the measure of performance of motor or aviation fuel. 8
  9. 9. ModificationsRequired for converting gasoline engines for use of ethanol fuel The engine which is designed for the use of gasoline fuel cannot be usedwith ethanol fuel. Ethanol has higher octane rating than petrol. Hencecompression ratio to be achieved while using ethanol is more than that whileusing petrol. Also, the calorific value of ethanol is less than petrol; hence morefuel is needed to be burnt to obtain a certain amount of energy, as compared topetrol. Ethanol is a cleansing agent. When used in engine, it cleans the dirt andfilth is formed in the engine. This may damage some parts of the engine andmake them useless. Taking into account all these properties of ethanol, certain modificationsare required in the engine. The modifications vary depending on the maker ofthe engine, technologies used, percentage of ethanol to be used as fuel, etc. Major areas where modifications are necessary are as follows. 9
  10. 10. Main jet modifications The first thing to be altered is the main metering jet in the carburettor. Inmost carburettors, this is a threaded brass plug with a specific-sized hole drilledthrough the centre of it. This hole is called the main jet orifice, and its diameterdictates how rich or lean the air/fuel mixture will be when the car is travelling atcruising speeds. Naturally, the smaller the hole is, the less fuel will blend withthe air and the leaner the mixture will be. As the orifice is enlarged, the mixturegets richer. Since alcohol requires a richer air/fuel ratio, its necessary to bore out themain jet orifice when using ethanol fuel. In order to operate the enginesuccessfully on alcohol fuel, its necessary to enlarge this opening from 20 to40%. There are some carburettors that do not use fixed-size jets alone, but alsoutilize device known as a "metering rod". This is usually a thin, tapered orstepped rod thats suspended within the jet orifice, which may or may not beremovable. The fuel, in this case is drawn through the space between the rodand its housing. Depending on how far the throttle is opened, the metering rod islifted out of the hole. Since the rod is thick at its "base" (near the top), andprogressively thinner at its tip (toward the bottom) - the farther its drawn out ofthe hole, the more fuel is allowed to flow between the central rod and theopening. The conversion on this type of metering system is basically the same asthe fixed-jet conversion. To enlarge the orifice, either remove the metering rodand very carefully drill the jet or turn the brass rod slightly. The diameter, ifincreased in size, should be increased anywhere from 15 to 35%. Fig. 1: Main jet orifice 10
  11. 11. Idle orifice changes Most carburettors will require additional idle circuit enlargement in orderfor the engine to run at slowest or idle speeds. This is because the circuit whichis fed by the main jet operates fully only when the throttle plate within thethroat of the carburettor is opened past the idle position. When the plate is in theidle position, the air/fuel mixture is allowed to enter the manifold only throughthe idle orifice. If this orifice isnt large enough, it will not provide the neededamount of air/fuel blend to keep the engine running. In some engines, it may only be needed to loosen the idle mixture screwat the base of the carburettor in order to provide the correct amount of fuel. Insome engines, it is possible that the seat itself, into which the tapered screwextends, must be enlarged in order to accomplish the same thing. In most cases, if the seat has to be bored out, it can be enlarged up to50%. This will allow a full range of adjustment with the idle mixture screw,even if one wants to go back to gasoline fuel. As a precaution against the idle screws vibrating loose from its threadedopening, the idle mixture screw spring can be coupled with a couple of smalllock washers. This will prevent the screw from turning even if its drawn outfarther from the seat than it normally would be. Fig. 2: Idle orifice jet 11
  12. 12. Power valve changes Most modern auto carburettors have a valve, known as a power valve thatallows extra fuel to blend with the air/fuel mixture when the accelerator isdepressed, in order to enrich the mixture under load conditions. This is avacuum-controlled valve, is spring loaded, and shuts off when it isnt needed inorder to conserve fuel. The power valve used in some of the carburettors is somewhat difficult toalter and, besides, is sufficient for alcohol use in its normal configuration if itsworking properly. However, there are some carburettors that have easilyreplaceable power valves which are available in various sizes. If a power valvewith a 25% increased dimension or so is used, the air/alcohol mixture will besufficiently enriched to give engine needs more power when needed. Fig. 3: Power valve 12
  13. 13. Accelerator pump changes In addition to a power valve, almost all automotive carburettors utilize anaccelerator pump. This is a mechanically activated plunger or diaphragm thatinjects a stream of raw fuel directly down the throat of the carburettor when theaccelerator is suddenly depressed. The reason the accelerator pump is incorporated into modern carburettorsis that as the accelerator is pressed and more air/fuel mixture is drawn into thecylinders, some of the liquid particles in the blend tend to stick to the walls ofthe intake manifold, effectively leaning out the mixture by the time it reachesthe combustion chambers. The extra squirt of fuel that is added by theaccelerator pump makes up for this initial lean condition. In order to adapt the accelerator pump to use alcohol effectively, the sizeof the injection orifice needs to be increased. (anywhere from 10 to 25% isfine.) As an alternative to enlarging the hole, simple adjustment of the strokelength of the pump arm in order to feed more fuel is sufficient. Mostcarburettors installed on recent engines already have a provision for seasonaladjustment, so its just a matter of putting the pump on its richest setting. Othercarburettors, too, have threaded rods that can be adjusted to accomplish thesame thing. Fig. 4: Accelerator pump jets 13
  14. 14. Compression ratio changesThe ratio is calculated by the following formula:Where, b= cylinder bore (diameter) s= piston stroke length Vc= clearance volume. CR is the ratio cylinder volume when piston is at BDC to the cylindervolume when piston is at TDC. This modification will do a great deal to improve engine performance andeconomy. The compression ratio hike will take advantage of the potential thatethanol has to offer as a fuel. Optimally, the ratio can be increased to 14- or 15-to-1. But even a nominal increase to 12-to-1 will result in a vast improvementover the standard 8- or 8.5-to-1 that most manufacturers incorporate into theirengines today. The most inexpensive way to increase the compression ratio is to install aset of high compression pistons. The forged units are designed to pack theair/fuel charge tightly into the combustion chamber for increased power, andhave special relief notches built into their heads for valve clearance. However,some engines may not tolerate a 15-to-1 compression ratio with standardconnecting rods and bearings. These components, too, may have to be replacedwith high-strength competition grade parts. Another way of increasing compression ratio slightly is by "milling thesurfaces of the cylinder head and/or block. A third - and perhaps the most versatile - way of effectively increasingthe compression ratio is by installing a turbocharger. These units, althoughrange high in price, provide a pressure boost in the combustion chamber 14
  15. 15. proportional to the engines RPM. Hence, compression would not be excessive during engine start-up as it would be with the other methods. No problem is encountered with a severe compression ratio increase, unless switching back to gasoline fuel. To switch back to gasoline, installing a water injection cooling system that would allow operating the car even on regular fuel without fear of detonation would be helpful.Fig. 5: High compression piston Fig. 6: Milled piston Fig. 7: A turbocharger 15
  16. 16. Cold weather starting Since alcohol doesnt vaporize as easily as does gasoline, cold weatherstarting can be a problem, especially if the engine itself is cold. To alleviate thisundesirable situation, a combination cold start/dual-fuel system can be used,which can work with any engine. The various other remedies to overcome this problem are as follows:Fuel preheating In extremely cold climates, it may be necessary to preheat the alcoholfuel before it enters the carburettor. This can be accomplished easily byinstalling a fuel heater. This can be achieved by passing the fuel through a tube, which passesover the engine radiator. The hot engine parts will heat the fuel sufficiently. But,this is not a very effective method, as while starting the cold engine, passing thefuel over the radiator makes no effect. The engine should be started by somealternative ways.Air preheating Most trucks and autos have air filter housings which are designed toallow heated air from around the exhaust manifold to channel through a ductand enter the carburettor when the engine first starts from a cold state. As theengine warms up, a flap within the air cleaner "snorkel" shuts off this supply ofwarm air and allows ambient air from the engine compartment to enter instead. This flap is usually either thermostatically or vacuum controlled. External resistance type air pre heaters may also be used for this purpose. Fig. 8: air pre heater schematic 16
  17. 17. Thermostat changes In order to get maximum efficiency from your engine, the thermostatwithin the engine block may need to be changed. A thermostat is designed tohold the coolant within the cylinder head till it achieves the desired temperature.Depending on the engines operating conditions, the thermostat may cycle openand shut regularly over the span of a few minutes. The thermostat decides the temperature at which the coolant will enter thehead. As the working temperature of an ethanol fuel engine is less than that of apetrol engine, the thermostat may need to be changed. 17
  18. 18. Initial use of alcohol fuel An engine altered as per the above modifications will run well on alcohol.But the alcohol will act as a cleansing agent. And will not only clean out thetank, fuel lines, and filters, but will also purge engines internal parts of built-upcarbon, gum, and varnish deposits. In effect, suddenly a lot of filth will be floating around in fuel. And itmay be enough to clog the fuel filter to the point of not allowing any fuel topass. Loosened internal engine deposits can foul the spark plugs badly. In addition to the fact that alcohol is a cleaning agent, it is also a solvent.And this means that certain types of plastics used in the fuel system of theengine may be attacked by it. In engines that use plastic components, however, there are several areasof potential deterioration: 1. within the fuel tank, both the float and the straineron the fuel intake tube may be plastic. 2. The fuel lines themselves if they arethe clear, flexible type, may also soften. 3. The fuel pump diaphragm may alsobe subject to failure. 4. Plastic in-line fuel filters should be replaced with metalones. 5. Many modern carburettors use plastic float needles, seals, and floats. Of course, not all plastics are subject to corrosion, and neither are alltypes of rubber. Generally, butyl rubber (like the type used in inner tubes)should be avoided. 18
  19. 19. Fuel injection systems Since some vehicles are equipped with fuel injection rather thancarburettors, we will briefly touch on the use of alcohol with that system. Thereare two important factors in a fuel injection setup: injection timing and controljet diameter. Fortunately, since many systems now use an electronicallycontrolled timing sequence, injection timing is not critical in a fuel injectedengine. Neither performance nor economy can be improved substantially byeither advancing or retarding the injection timing process. Control jet diameter, on the other hand, is an important factor. If the sizeof the control jets (which are the equivalent of the metering jets in a carburettor)is increased, the engine will operate well on alcohol fuel. An increase of 15-20% is all thats necessary to accomplish the conversion. An interesting feature of the fuel injection system is that it doesnt requireany gasoline during the cold weather starting process to fire the engine up.Since the fuel is injected at a pressure of about 250 PSI, the alcohol fuel issufficiently vaporized to ignite easily within the combustion chamber. 19
  20. 20. Benefits of using ethanol fuel 1. Ethanol is obtained from a number of sources, both natural and manufactured. 2. It is a high octane fuel with octane number over 100. Engines using high octane fuels can run more efficiently by using higher compression ratios. 3. It produces less overall emissions compared to gasoline. 4. When ethanol is burned, it forms more moles of exhaust gasses, which gives higher pressure and more power in expansion stroke. 5. It has high latent heat of vaporization which results in a cooler intake process. This raises the volumetric efficiency of the engine and reduces the work input in the compression stroke. 6. Alcohols have low sulphur content and hence help in reducing emissions and pollutions. 7. Ethanol can be made naturally from crops like sugarcane or by fermentation of food grains. (It can be made even at home!) 20
  21. 21. Disadvantages of ethanol fuel 1. Ethanol has low energy content. 2. More ethanol fuel needs to be burned to obtain same energy as obtained by petrol. 3. Ethanol has poor ignition characteristics. 4. Ethanol has almost invisible flames, which are dangerous while handling the fuel. 5. Odour of ethanol is very offensive. 21
  22. 22. Common ethanol fuel mixtures Various types of ethanol fuel mixtures can be used. Ethanol mixtures usually range from E5 to E100. The numerical representing the percentage of ethanol in the mix. Commercially available mixtures E85 and E100 need modifications in the engine, while other mixtures can be used without any modifications. Fig. 9: ethanol percentages. 22
  23. 23. Conclusion For use of ethanol in engine, with alcohol percentage above 85%, some modifications are required. The modifications can be summarised as in the following table. Exhaust system Intake manifold Ignition system Fuel pr. Device Cold start syst. Ethanol blend Fuel injection Carburetor Fuel pump Fuel filter Motor oil Fuel tank<=5% NO NO NO NO NO NO NO NO NO NO NOE5-E10 YES NO NO NO NO NO NO NO NO NO NOE10-E25 YES YES YES YES YES YES NO NO NO NO NOE25-E85 YES YES YES YES YES YES YES YES YES YES NOE85-E100 YES YES YES YES YES YES YES YES YES YES YES Table 2: modification in parts 23
  24. 24. References  Internal Combustion engines- V Ganesan, 4th edition TMH publications.  "Sustainable bio-fuels: prospects and challenges” Joseph (2007) in The Royal Society (2008).  Hydrous ethanol vs. gasoline-ethanol blend: Engine performance and emissions- Rodrigo C. Costa, José R. Sodré Pontifical Catholic University of Minas Gerais, Department of Mechanical Engineering, MG, Brazil.    Image source: Google. 24
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