6. alternative fuels

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6. alternative fuels

  1. 1. ALTERNATIVE FUELS FOR I.C.ENGINES
  2. 2. Table 1 COMPARATIVE PROPERTIES OF S.I. ENGINE FUELS Fuel Gasoline Property Liquid Density 0.70 at 15oC (g/cc) Latent Heat 303 (kJ/kg) Vap.pr@38o C 0.8 bar Heating Value 44,000 (kJ/kg) Volumetric Liquid Energy Density(kJ/Lit) 30,800 at atm.pr.& temp. Stoichiometric 15.0 A/F by mass Flammability Limits (% by vol. 1.2 - 6 of vapour) A/F by mass at 21.5 (lean) the limits 4.5 (rich) Max. possible 44 leaning air (%) (Lean limit Ø) 0.686 Octane Number 85 –100 (Research) B.Pt. at atm. pr. 99.5 (50 to 220) (oC) Toxicity low Total System Efficiency (%) 15 (from Production to Utilization) Propane (LPG) 0.582 Methanol Ethanol 0.79 0.78 425 1168 13.3 bar 46,000 Hydrogen Ammonia Biogas CNG (60%CH4 ) (96%CH4 ) __ __ 0.68 920 0.07 (at 20 K) 456 1306 __ 510 0.32 bar 19,600 0.16 bar 26,750 1,20,000 18,600 14,500 55,200 26,800 15,480 20,870 8400 12,650 --- --- 15.6 6.4 8.95 34.5 6.06 5.9 17.3 7 – 36 4.3 – 18 4 – 75 16 – 29 --- 5.3 – 15 29.9 6.93 91.6 12.9 2.5 101 15.0 3.51 68 360.0 19.3 943 10.6 5.88 75 __ __ __ 34.2 12.08 97.6 0.515 >100 0.493 106 -115 0.609 > 100 0.093 > 100 0.549 --- --> 100 0.502 130 -42.18 65 78 - 253 - 33 --- - 161.4 nil high nil nil high nil nil 9.0 12 13.5 6.3 7 --- -- 2.2 - 9.5
  3. 3. Alternate Fuels Table 2 COMPARATIVE PROPERTIES OF C.I. ENGINE FUELS Fuel Diesel Sunflower oil Groundnut Oil Sp. Gravity 0.83 0.92 0.91 %C by mass 86.6 78.3 76.7 %H by mass 13.4 12.8 11.5 %O by mass 0.0 8.75 11.7 Calorific value(kJ/kg) 42,967 36,981 37,000 Cetane Number 50.8 33.4 36.0 Stoichiometric A/F by mass 14.49 12.99 12.8 Viscosity @ 20◦C(C.S.) 4.1 65.2 60.5 Boiling Pt.@ atm.pr.(◦C) 150 300 350 Cloud Pt (◦C) -17.8 -6.7 -2.5 Properties
  4. 4. Alternate Fuels Table 3. Properties of some Bio-fuels Property Colour HSD Pale Yellow Jatropha Oil Jatropha Ester Ground Nut Oil Honge Oil Coconut Oil Sunflower oil Sunol Ester yellow - Pale Yellow Red Colorless Pale Yellow Pale Yellow Colorless/ Density @ 25C Kg/m3 840 918.6 880 902 921 917 902 872 Net C.V. kJ/kg 42000 39774 38450 37373 39246 36330 39900 39260 Viscosity @ 25C C.St 3.9 49.93 5.65 40.53 44.7 29.4 48 5.45 CN. 45-55 40-45 50 35-40 35-45 35-40 35-40 50 Flash Point C 48 240 170 217 205 226 274 150 Carbon Residue % wt. 0.1 0.6 0.5 0.3 0.42 0.17 0.6 0.5
  5. 5. Alternate Fuels 1. Advantages of Alcohol over gasoline • Renewable in nature • Higher Octane rating • Higher power due to better volumetric efficiency • Higher thermal efficiency due to higher HUCR • Produces less emissions compared to gasoline. 2. Limitations of Alcohol over gasoline • Lesser Calorific Value and Higher cost. • Combustion of alcohols produces aldehydes in the exhaust which are harmful. • Water absorption- hence metal corrosion problem • Chemical attack on plastic components in direct contact • Lower overall system efficiency- production to utilization. • Almost invisible flames considered dangerous when handling fuel. • Strong odor of the fuel. • Storage tank flammability due to air leak into the storage tanks.
  6. 6. Alternate Fuels • Utilization of alcohol blend for automobiles requires proper monitoring, accounting and caution in handling stations. • Utmost care should be taken to store the alcohol and its blends to keep away from moisture. • Adequate steps should be taken to double the alcohol production to meet the requirement. • Alcohol burns at half the speed of the engine. • Latent heat of vaporization is much greater – cold starting problem.
  7. 7. Alternate Fuels Utilization of alcohol in Diesel engines • Blend of moisture free alcohol in Diesel ( Upto 20%) can be used • Dual fuel injection.
  8. 8. Alternate Fuels Merits of Hydrogen • • Hydrogen has the fastest burning velocity which causes rapid combustion and hence high engine speed, thereby improving the specific output. • It has an excellent lean burning ability which improves its thermal efficiency. • It has a high Octane Number, which enables higher CR to be used with the associated higher imep and higher energy conversion efficiency. • It has a high self ignition temperature (581ºC compared to 450ºC for gasoline or 466ºC for propane and 534ºC for methane) which makes it highly knock resistant.
  9. 9. Alternate Fuels • When it burns in air it produces steam and the exhaust is devoid of CO, CO2, SO2, smoke and Carcinogens. The only expected pollutant is NOx which can be easily controlled by lean burning or by EGR technique. • Tasteless, odourless and non-toxic by itself, hydrogen gives out just clean energy producing steam, thereby maintaining the Nature’s balance of water in the hydrosphere. • It is highly combustible, requiring very little energy (1/12 of gasoline) to ignite it. (0.02 mJ compared to 0.25 mJ for gasoline and propane and 0.3 mJ for methane under similar laboratory test conditions). • It has a very high calorific value on mass basis.
  10. 10. Alternate Fuels PRODUCTION OF HYDROGEN • Hydrogen can be produced by several methods. 65% of the total production of hydrogen in the world is by catalytic steam reforming of methane or naptha, 25% by partial oxidation of heavy oils, 7% by water gas reaction from coal/coke and 3% by electrolysis of water. • Direct thermal splitting of H2O (at 3000ºC) using solar focusing collectors, thermo-chemical splitting of H2O (at 850ºC) using FeCl2 or CrCl2, modified photosynthetic reactions in green plants and algae using specific enzymes etc. are some of the techniques under consideration and development to produce hydrogen.
  11. 11. Alternate Fuels DE-MERITS OF HYDROGEN • Its high combustibility can cause fire hazards and inlet back fire. This requires flame traps, flash back arresters and crank case ventilation to prevent explosions due to blow-by accumulation. • Due to its very low density (0.09 kg/m³ for the gas) it has a very low volumetric energy density and hence on-board storage requires a large volume for a given mass. • Due to complexity and cost of cryogenic liquid hydrogen storage, carrying hydrogen on board in a vehicle is a challenging task. One of the acceptable solutions is storage in the form of metal hydrides, which, unfortunately, can hold only about 2 to 8% by mass of hydrogen in it. • Hydrogen is very expensive and its production is highly energy intensive.
  12. 12. Alternate Fuels  Carburetion or valve controlled flow into the intake manifold directly from hydrogen cylinder or hydrid storage.  Manifold hydrogen gas injection.  Direct in-cylinder injection (Gas or Liquid) ON-BOARD STORAGE OF HYDROGEN  Compressed hydrogen gas storage in high  Hydrogen storage in the liquid form pressure cylinders
  13. 13. Alternate Fuels Comparison of typical hydrogen storage systems for equal energy storage Fuel Container volume in liters Mass of fuel in kg Mass of container + fuel Gasoline 75.7 53.1 68 Liquid hydrogen 275 19.5 136 Hydrogen gas at 138bar 1820 19.5 2090 19.5 316 Metal Hydride: Mg-Ni 310
  14. 14. HYDROGEN STORAGE SYSTEM IN A PASSENGER CAR
  15. 15. Alternate Fuels Hydrogen as an alternative fuel -conclusion • Technical feasibility of hydrogen as a renewable alternative to petroleum fuels has been successfully demonstrated by experiments in the laboratory as well as on the road. However, before hydrogen can be considered for wide use in automobiles further research efforts are required in the following areas- • Production of hydrogen at an affordable cost • On-board storage of hydrogen with improved power to weight ratio • Safe methods to prevent fire hazards during operation and due to accidents • Analysis of hydrogen supply system with computerized control of mixture ratio in response to drive commands and exhaust emission levels • Performance studies on all-weather and altitude operation including extreme cold starting

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