SOME ALTERNATIVE FUELS FOR I.C. ENGINES Conventional and Non-conventional

Conditions for long-term acceptability of alternate fuels There must be an adequate supply of the fuel at an acceptable price of the basic material resource from which the fuel can be made. There must be an economic and environmentally acceptable means of converting the base material to the practical fuel. There must be an economic, reliable and safe means of handling the fuel in practice, including delivery to the point of sale. There must be a supply on a mass production scale of vehicles capable of using the fuel while conforming to imposed requirements for emission control and fuel economy.

An Example An example of the above conditions is the oil shale deposits of Mahogany Ledge in the USA which is said to contain as much oil as the total world proven oil reserves. However, conditions 1 and 2 above are not met with. No more than 2% of the oil content of the shale can be won, based on present day technology.

Types of Fuels Fuels for engines are typically Gaseous Liquid Originally solid also but now very rarely used. May be Naturally available or Artificially derived

Gaseous Fuels Main fuels for engines are Natural gas – from nature Liquefied Petroleum Gas - from refineries Producer gas - from coal or biomass Biogas - from biomass Hydrogen – from many sources

Atomic hydrogen/carbon ratio

Natural Gas Found compressed in porous rock and shale formations sealed in rock strata underground. Frequently exists near or above oil deposits. Is a mixture of hydrocarbons and nonhydrocarbons in gaseous phase or in solution with crude oil. Raw gas contains mainly methane plus lesser amounts of ethane, propane, butane and pentane, negligible sulfur and organic nitrogen. Some carbon dioxide and nitrogen are present.

Natural Gas The only gas occurring in nature. Origin is believed to be organic (Majority view) Due to methanation of carbon dioxide with hydrogen, both mineral in origin (more recent theory) May be found with (associated) or without (unassociated) crude oil. Contains 60 to 90% methane, rest are propane, butane, heavier and more complex hydrocarbons, carbon dioxide and nitrogen plus some helium.

Natural Gas (Continued) Certain processes have to be carried out. Separation of liquid and gas. Liquid may be a hydrocarbon present in the gas well along with the gas. Dehydration. Water is corrosive and hydrates may form which will plug the flow. Water will also reduce the calorific value of the gas. Desulfurization. Presence of hydrogen sulfide is undesirable. The gas is called sour. When the sulfur is removed the gas is sweetened.

Natural Gas (Continued) Natural gas may be used as Liquefied Natural Gas (LNG). Compressed Natural Gas (CNG). “Natural” gas when made artificially it is called substitute, or synthetic or supple-mental natural gas (SNG).

Natural Gas (Continued) Natural gas has 90-95% methane plus 0-4% nitrogen, 4% ethane and 1-2% propane. Methane is a greenhouse gas with a global warming potential approximately 4 times that of carbon dioxide. Its C/H ratio is lower than that of gasoline so its CO2 emissions are 22-25% lower (54.9 compared to 71.9 g CO2/MJ fuel).

Comparing Fuels A report published by Thring (SAE Paper no. 831685) indicated that an engine, which started as a diesel engine, produced 10% more power when run on gasoline, 5% less power on natural gas, and 35% less power when run on biogas.

Comparing Fuels Contd When natural gas is compressed to 17.3 MPa, at 21oC, its energy density is only 7 kJ/cm3. For methanol it is 17 kJ/cm3 and for gasoline it is 30 kJ/cm3. Natural gas has a lower calorific value per unit mass at equivalence ratio of 1.0. The volumetric efficiency is reduced by 12% (9% due to fuel volume and 3% due to lack of latent heat of evaporation). It has a higher octane number so it is harder to knock and hence a higher compression ratio can be used (11.0 against 9.5 for gasoline).

ULEV Standards Natural gas vehicles were the first to meet the California ultra-low emission vehicle (ULEV) emission standards. Combustion of methane is different from that of liquid HC combustion since only C-H bonds are involved. There are no C-C bonds involved so the combustion process is more likely to be complete thereby producing less non-methane HC emissions.

Advantages There are some advantages also: Particulate emissions are very low relative to diesel fuel. Lower adiabatic flame temperature (~2240K) compared to gasoline (~2310K) due to its higher product water content, giving lower NOx. Operating under lean conditions will also lower peak combustion temperatures giving lower NOx.

Natural Gas in SI & CI Engines When an engine was switched over to CNG from gasoline, the non-methane organic gases, CO and NOx, all reduced by 30-60%. Toxic emissions like benzene, butadiene and aldehydes were much less than with gasoline. Natural gas can replace diesel fuel in heavy-duty engines with the addition of a spark ignition system. Engines operate at  = 0.7 giving low in-cylinder temperatures and hence low NOx. Heavy-duty natural gas engines are designed to meet low emission vehicle (LEV) emission standards without a catalytic converter and will meet ULEV emission standards with a catalytic converter

Energy density of stoichiometric fuel-air mixture: Typical Composition of Producer gas Component Percentage Hydrogen 20 Carbon Monoxide 19.5 Carbon Dioxide 12.5 Methane 2 Nitrogen 46 Octane Number 100-105 Lower Heating Value 6.7 MJ/m3 Energy density of stoichiometric fuel-air mixture: Producer gas: 2.5 MJ/m3 Gasoline-air: 3.5 MJ/m3 Diesel-air: 3.3 MJ/m3

Biogas… Extremely low energy density on the volume basis, Low flame velocity and not so wide flammability limits on account of its high CO2 content. The flame speed is just 25 cm/s as against 275 cm/s for hydrogen. The self-ignition temperature of biogas is high and hence it resists auto-ignition. This is a desirable feature in Spark Ignition (SI) engines, The ignition centers formed by the pilot spray lead to flame propagation through the homogeneous gas air mixture that is inducted.

Hydrogen properties

Emission variations: With H2

Hydrogen – natural gas…

Hydrogen – natural gas…

Hydrogen – natural gas…

Hydrogen – natural gas…

Hydrogen – biogas…

Hydrogen – biogas…

Hydrogen – biogas…

Conclusions Researchers have found that 20 percent addition of hydrogen in natural gas is the highest for the desired performance of engines running on hydrogen mixed fuels. For other gaseous fuels the limit is much less. In case of methane, this amount is about 10 percent of the mixture. In case of landfill gas, adding hydrogen even in very little quantities improved the combustion process and reduced the cyclic variations of landfill gas, particularly at lean and rich mixtures.

Composition of landfill gas No. Gas % in volume 1 Methane 45–50 2 Carbon dioxide 40–60 3 Nitrogen 2–5 4 Oxygen and other <1

LANDFILL GAS AS A FUEL Landfill gas can be used as a fuel because of the presence of methane. The heating value of the landfill gas is 16,785–20,495 kJ/m3 (450–550 Btu/ft3) as compared to 35,406 kJ/m3 (950 Btu/ft3) of commonly used natural gas. Both stoichiometric and lean burn internal combustion engines can be used with landfill gas.

Hydrogen Addition to Land fill gas It was found that addition of hydrogen to the landfill gas had a very significant effect in reducing the ignition lag and the combustion duration. Usually the ignition lag and combustion duration are higher in the lean and rich side of the operations which is undesirable for combustion stability, some time causing the combustion process to continue even after the exhaust valve opens. The combustion duration also increases as the concentration of diluents in the fuel increases. These adverse effects are counteracted by the addition of hydrogen which reduces the ignition lag, combustion duration and the cyclic variations by combustion enhancement and faster burning rates in all the equivalence ratios.

Sources of Bio-Diesel Sources Blends B10 B20 (conventional limit) Karanja Jatropha Rapeseed Flax Canola Soyabean Blends B10 B20 (conventional limit) (requires engine modification.) B30 B50 B75 B100 (pure BD)

BIODIESEL SPECIFICATIONS PROPERTIES UNIT DIN 51606 (1997) ASTM (2001)6751 Density g/cm3 0.875-0.90 -- Carbon Residue (100%) % mass Max 0.05 Max 0.050 Ash Content Max 0.02 Max 0.020 Total Sulfur Max 0.01 Cetane No. Min 49 Min 40 Flash Point 0C Min 110 Min 100 Copper Corrosion degree 1 No. 3b max Viscosity, 40 0C mm2/s (cSt) 3.5-5.0 1.9-6.0 Neutralization Value mg Max 0.5 Max 0.8  Free Glycerin Total Glycerin Max 0.25 Max 0.24 CFPP Summer (0C) Max 0.0 Winter (0C) Max -15

Claims Chiefly lower emissions (higher NOx). Rural economy (India). University of Dakota (Studies) NAVFAC Report

Brake Thermal Efficiency Vs Brake Power

BMEP Vs Brake Power

Emissions – CO%

Emissions – CO2 %

Emissions - UBHC

Emissions- NOx

NREL- Analysis

Results – PM Particulate matters data Song Kong and Anne Kimber, University of Iowa

Results – CO CO data Song Kong and Anne Kimber, University of Iowa

Results – NOx NOx data Song Kong and Anne Kimber, University of Iowa

Results – BSFC BSFC data HHV [BTU/gal] B0 139,340 B10 139,540 B20 138,920 B100 126,657 Song Kong and Anne Kimber, University of Iowa

Venkateswara Rao et al (2007)

Venkateswara Rao et al (2007)

Venkateswara Rao et al (2007)

NAVFAC Technical Report

NAVFAC Technical Report

Other researchers… Najafi Ghobdian et al 2007 did not find much difference in power (waste cooking oil).

Conclusions The increase in fuel economy will be notable for large fleet trucks [NAVFAC Technical Report] Cost of Biodiesel – Jatropha Rs.33 / litre (Diesel - Rs.34/litre) No cost incentive to switch over especially at the loss of fuel economy

RESULTS AND DISCUSSION USING SHALE/DIESEL

Hydrocarbon and carbon monoxide (CO) emission

Nitric oxide (NO) emission NO in the cylinder depends on the combustion rate.

Smoke and particulate emission

Carbon dioxide (CO2) emission CO2 level is observed to be lower for LPG operation (1.7–5.3%) compared to diesel operation (2.4–6.9%) due to lower carbon to hydrogen ratio of LPG.