FUELS AND FUEL INJECTION

FUELS AND FUEL INJECTION

IN IC ENGINES, THE CHEMICAL ENERGY CONTAINED IN THE FUEL IS CONVERTED INTO MECHANICAL POWER BY BURNING (OXIDIZING) THE FUEL INSIDE THE COMBUSTION CHAMBER OF THE ENGINE.

FUELS SUITABLE FOR FAST CHEMICAL REACTION MUST BE USED IN IC ENGINES, THEY ARE FOLLOWING TYPES.

• HYDROCARBONS FUELS DERIVED FROM THE CRUDE PETROLEUM BY PROPER REFINING PROCESS SUCH AS THERMAL AND CATALYTIC CRACKING METHOD, POLYMERISATION, ALKYLATION, ISOMERISATION, REFORMING AND BLENDING.
• ALTERNATIVE FUELS SUCH AS-ALCOHOLS, (METHANOL, ETHANOL), NATURAL GAS (METHANE), LPG (PROPANE, BUTANE), HYDROGEN.

CLASSIFICATION OF PETROLEUM FUELS USED FOR IC ENGINE:

• LIQUID HYDROCARBONS- ENGINE FUELS ARE MAINLY MIXTURES OF HYDROCARBONS, WITH BONDS BETWEEN HYDROGEN AND CARBON ATOMS. DURING COMBUSTION THESE BONDS ARE BROKEN AND NEW BONDS ARE FORMED WITH OXYGEN ATOMS, ACCOMPANIED BY THE RELEASE OF CHEMICAL ENERGY. PRINCIPAL PRODUCTS ARE CARBON DIOXIDE AND WATER VAPOUR. FUELS ALSO CONTAIN SMALL AMOUNTS OF S, O₂, N₂, H₂O. THE DIFFERENT CONSTITUENTS OF CRUDE PETROLEUM WHICH ARE AVAILABLE IN LIQUID HYDROCARBONS ARE- PARAFFINS, NAPHTHENES, NAPHTHENES, OLEFINS, AROMATICS.

PARAFFIN:

• PARAFFINS OR ALKANES CAN IN GENERAL BE REPRESENTED BY-C_nH2_n+2
•  ALL THE CARBON BONDS ARE SINGLE BONDS.
• THEY ARE “SATURATED” HIGH NUMBER OF H ATOMS, HIGH HEAT CONTENT AND LOW DENSITY (620 – 770 KG/M3)
• THE CARBON ATOMS CAN BE ARRANGED AS A STRAIGHT CHAIN OR AS BRANCHED CHAIN COMPOUNDS.
• STRAIGHT CHAIN GROUP (NORMAL PARAFFINS)
•  SHORTER THE CHAIN, STRONGER THE BOND
• NOT SUITABLE FOR SI ENGINES – HIGH TENDANCY FOR AUTOIGNITION ACCORDING TO THE VALUE OF “N”, THEY ARE IN GASEOUS (1 TO 4), LIQUID (5 TO 15) OR SOLID (>16) STATE.
• BRANCHED CHAIN COMPOUNDS (ISOPARAFFINS) - WHEN FOUR OR MORE C ATOMS ARE IN A CHAIN MOLECULE IT IS POSSIBLE TO FORM ISOMERS, THEY HAVE THE SAME CHEMICAL FORMULA BUT DIFFERENT STRUCTURES, WHICH OFTEN LEADS TO VERY DIFFERENT CHEMICAL PROPERTIES.

           EXAMPLE: ISO-OCTANE- C8H18

NAPHTHENES:

• IT IS ALSO CALLED AS CYCLOPARAFFINS AND REPRESENTED AS C_nH_2n.
• SATURATED HYDROCARBONS WHICH ARE ARRANGED IN A CIRCLE HAVE STABLE STRUCTURE AND LOW TENDANCY TO AUTOIGNITE COMPARED TO ALKANES (NORMAL PARAFFINS).
• CAN BE USED BOTH IN SI-ENGINES AND CI-ENGINES.
• LOW HEAT CONTENT AND HIGH DENSITY (740 – 790 KG / M3).

OLEFINS:

• OLEFINS OR ALKENES ARE REPRESENTED AS MONO OLEFINS-CNH2N OR DIO-OLEFINS CNH2N-2 -OLEFINS HAVE THE SAME C-TO-H RATIO AND THE SAME GENERAL FORMULA AS NAPHTHENES, THEIR BEHAVIOR AND CHARACTERISTICS ARE ENTIRELY DIFFERENT.
• THEY ARE STRAIGHT OR BRANCH CHAIN COMPOUNDS WITH ONE OR MORE DOUBLE BOND. THE POSITION OF THE DOUBLE BOND IS INDICATED BY THE NUMBER OF FIRST C ATOM TO WHICH IT IS ATTACHED.
• OLEFINIC COMPOUNDS ARE EASILY OXIDIZED, HAVE POOR OXIDATION STABILITY.
• CAN BE USED IN SI-ENGINES, OBTAINED BY CRACKING OF LARGE MOLECULES LOW HEAT CONTENT AND DENSITY IN THE RANGE 620 – 820 KG / M3.

AROMATICS

• THESE ARE SO CALLED DUE TO AROMATICS ODOUR AND REPRESENTED AS C_nH2_n-6.
• THEY ARE BASED ON A SIX-MEMBERED RING HAVING THREE CONJUGATED DOUBLE BONDS.
• AROMATIC RINGS CAN BE FUSED TOGETHER TO GIVE POLYNUCLEAR AROMATICS, PAN, ALSO CALLED POLYCYCLIC AROMATIC HYDROCARBONS, PAH SIMPLEST MEMBER IS BENZENE (C₆H₆).
• CAN BE USED IN SI-ENGINES, TO INCREASE THE RESISTANCE TO KNOCK NOT SUITABLE FOR CI-ENGINES DUE TO LOW CETENE NUMBER.
• LOW HEAT CONTENT AND HIGH DENSITY IN THE RANGE 800 – 850 KG / M3.

REFINERY PROCESSES:

• CRUDE OIL IS THE LIQUID PART OF THE NATURALLY OCCURRING ORGANIC MATERIAL COMPOSED MOSTLY OF HCS THAT IS TRAPPED GEOLOGICALLY IN UNDERGROUND RESERVOIRS. IT IS NOT UNIFORM AND VARIES IN DENSITY, CHEMICAL COMPOSITION, BOILING RANGE ETC. FOR DIFFERENT FIELDS. THE REFINERY PROCESSES INVOLVED IN PRODUCTION OF DIFFERENT RANGE OF FUEL.

DISTILLATION PROCESS:

• THIS IS THE INITIAL PROCESS USED IN ALL REFINERIES – AIMS TO SEPARATE THE CRUDE OIL INTO DIFFERENT BOILING RANGE FRACTIONS, EACH OF WHICH MAY BE A PRODUCT A BLEND COMPONENT OR FEED FOR FURTHER PROCESSING STEP  CRUDE OIL CONTAINS MANY THOUSANDS OF DIFFERENT HCS, EACH HAS ITS OWN BOILING POINT – LIGHTEST ARE GASES AT AMBIENT TEMPERATURE BUT CAN REMAIN DISSOLVED IN HEAVIER LIQUID HCS UNLESS TEMPERATURE IS RAISED, HEAVIEST ARE SOLIDS AT AMBIENT TEMPERATURE BUT STAY IN SOLUTION UNLESS TEMPERATURE IS LOWERED.
• GASOLINE DISTILLATION TEMPERATURE IS 35 – 200^OC.

1. JET FUEL 35 - 150
2. DIESEL FUEL 175 – 370
3. HEAVY FUELS
4. OIL 370 – 550

• GENERALLY, DISTILLATION OF CRUDE OIL PRODUCES 30% GASOLINE, 20-40 % DIESEL FUEL, 20 % HEAVY FUELS, 10-20 % HEAVY OILS.

CRACKING PROCESS:

• THERE ARE TWO TYPES OF CRACKING PROCESS FOR ENGINE FUEL PRODUCTION: THERMAL CRACKING AND CATALYTIC CRACKING.

• THERMAL CRACKING: IT TAKES PLACE THROUGH THE CREATION OF HC FREE RADICALS BY C TO- C BOND SCISSION. THE FEED IS HEATED TO AROUND 500 - 600 ^OC  AND 70 - 100 BARS AND PASSED INTO A SOAKING CHAMBER WHERE CRACKING TAKES PLACE. THE CRACKED PRODUCTS ARE FRACTIONATED. THE PRODUCT IS RELATIVELY UNSTABLE AND REQUIRES THE USE OF ANTIOXIDANTS AND OTHER TREATMENTS TO PREVENT GUM FORMATION IN USE. IT HAS RELATIVELY POOR MON (MOTOR OCTANE NUMBER).

• CATALYTIC CRACKING: IT IS THE MOST IMPORTANT AND WIDELY USED PROCESS FOR CONVERTING HEAVY REFINERY STREAMS TO LIGHTER PRODUCTS – TO INCREASE THE RATIO OF LIGHT TO HEAVY PRODUCTS FROM CRUDE OIL. COMPARED TO THERMAL CRACKING, IT HAS HIGHER YIELD, IMPROVED QUALITY PRODUCT FOR GASOLINE (NOT FOR DIESEL FUEL) AND SUPERIOR ECONOMICS.  A FLUIDIZED BED OF CATALYST IS USED FEED IS INTRODUCED INTO IT. CATALYST FLOWS FROM ONE VESSEL TO ANOTHER THROUGH A PIPE (BETWEEN REACTOR AND REGENERATOR). CRACKED OIL VAPOUR PASS TO FRACTIONATING TOWERS WHERE SMALLER MOLECULES ARE SEPARATED FROM HEAVIER PRODUCTS (GAS, CATALYTIC NAPHTHA, CYCLE OILS AND RESIDUE). ALUMINIUM SILICATE KNOWN AS ZEOLITE IS USED AS A CATALYST – HAS HIGH ACTIVITY AND SUPPRESS THE FORMATION OF LIGHT OLEFINS.

• ALKYLATION: IT IS A PROCESS FOR PRODUCING A HIGH-OCTANE GASOLINE COMPONENT (ALKYLATE) BY COMBINING LIGHT OLEFINS WITH ISOBUTANE IN THE PRESENCE OF A STRONGLY ACIDIC CATALYST (SULFURIC OR HYDROFLUORIC ACID).

• ISOMERIZATION: IT IS A PROCESS FOR CONVERTING STRAIGHT CHAIN PARAFFINS TO BRANCH CHAIN – USED TO PROVIDE ISOBUTANE FEED FOR THE ALKYLATION PROCESS OR TO CONVERT RELATIVELY LOW-OCTANE QUALITY OF STRAIGHT PARAFFINS TO MORE VALUABLE BRANCH CHAIN MOLECULES.  EG. N-PENTANE WITH RON (RESEARCH OCTANE NUMBER) 62 CAN BE CONVERTED TO ISOPENTANE WITH RON 92. PROCESS INVOLVES CONTACTING HCS WITH A CATALYST (PLATINUM ON A ZEOLITE BASE) AND SEPARATING ANY UNCHANGED STRAIGHT PARAFFINS FOR RECYCLE THROUGH THE UNIT. THE PRODUCT IS CLEAN BURNING AND HAS BETTER RON QUALITY.

• POLYMERIZATION: IT IS A PROCESS WHERE LIGHT OLEFINS SUCH AS PROPENE AND BUTENES ARE REACTED TOGETHER TO GIVE HEAVIER OLEFINS WHICH HAVE GOOD OCTANE QUALITY AND LOW VAPOUR PRESSURE IN GASOLINE. MOST COMMONLY USED CATALYST IS PHOSPHORIC ACID. THE PRODUCT IS ALMOST 100 % OLEFINIC AND HAS RELATIVELY POOR MON COMPARED WITH RON.

ALTERNATIVE FUELS:

• ALCOHOLS: THESE INCLUDE METHANOL (METHYL ALCOHOL), ETHANOL (ETHYL ALCOHOL), PROPANOL (PROPYL ALCOHOL), BUTANOL (BUTYL ALCOHOL) AS COMPOUNDS. THE OH GROUP WHICH REPLACES ONE OF THE H ATOMS IN AN ALKANE, GIVES THESE COMPOUNDS THEIR CHARACTERISTIC PROPERTIES SPECIFIC HEATING VALUE IS LOWER THAN GASOLINE (42 – 43 MJ/KG) METHANOL (19.7 MJ/KG) AND ETHANOL (26.8 MJ/KG). FOR AIR-FUEL MIXTURE SHV IS COMPERABLE WITH GASOLINE (MJ/KG-MIXTURE AT STOICHIOMETRIC MIXTURES). OTHER ALCOHOL GROUPS SUCH AS DIHYDRIC AND TRIHYDRIC ALCOHOLS ARE NOT USED AS A FUEL IN IC ENGINES.

• METHANOL:

1. CAN BE OBTAINED FROM NATURAL GAS.
2. HAS NEAR AND LONG-TERM POTENTIAL,
3. HAS HIGH OCTANE QUALITY (130 RON, 95 MON)
4. CAN BE USED IN LOW-CONCENTRATION (5-15 %) IN GASOLINE TO INCREASE OCTANE NUMBER OF THE MIXTURE.

• ETHANOL:

1. PRODUCED FROM BIOMASS. IT IS MADE FROM THE SUGARS FOUND IN GRAINS, SUCH AS: CORN, SORGHUM, AND BARLEY OTHER SOURCES OF SUGARS TO PRODUCE ETHANOL INCLUDE: POTATO SKINS, RICE, SUGAR CANE, SUGAR BEETS, YARD CLIPPINGS, BARK, SWITCH GRASS ETC.
2. HAS HIGH OCTANE NUMBER.
3. CAN BE USED IN LOW–CONCENTRATIONS IN GASOLINE.
4. MOST OF THE ETHANOL USED IN THE UNITED STATES TODAY IS DISTILLED FROM CORN.
5. SCIENTISTS ARE WORKING ON CHEAPER WAYS TO MAKE ETHANOL BY USING ALL PARTS OF PLANTS AND TREES RATHER THAN JUST THE GRAIN.
6. ABOUT 99% OF THE ETHANOL PRODUCED IN THE UNITED STATES IS USED TO MAKE "E10" OR "GASOHOL," A MIXTURE OF 10% ETHANOL AND 90% GASOLINE.
7. ANY GASOLINE POWERED ENGINE CAN USE E10, BUT ONLY SPECIALLY MADE VEHICLES CAN RUN ON E85, A FUEL THAT IS 85% ETHANOL AND 15% GASOLINE.

BIODIESEL:

• IT IS METHYL OR ETHYL ESTER OF A FATTY ACID PRODUCED FROM VEGETABLE OIL OF EDIBLE OR NON-EDIBLE TYPES OR ANIMAL FAT OR ALGAE, BY TRANSESTERIFICATION PROCESS USING CATALYSTS.
• HAS BETTER LUBRICATING PROPERTIES AND MUCH HIGHER CETANE RATINGS THAN TODAY'S LOW SULFUR DIESEL FUELS.
• ITS ADDITION REDUCES THE FUEL SYSTEM WEAR.
• CAN BE USED IN THE PURE FORM (B100), OR MAY BE BLENDED WITH PETROLEUM DIESEL IN ANY CONCENTRATION IN MOST DIESEL ENGINES FOR TRANSPORTATION PURPOSE.
• BUT, THE ENGINE MAY FACE PROBLEMS, SUCH AS LOW TEMPERATURE OPERATION, LESS DURABILITY AND DROP IN POWER. NEW DIESEL FUEL INJECTION SYSTEMS, SUCH AS COMMON RAIL SYSTEMS ARE EQUIPPED WITH MATERIALS THAT ARE COMPATIBLE WITH BIO DIESEL (B100).
• BIO DIESEL OFFERS A SUBSTANTIAL REDUCTION IN PARTICULATE MATTER (25%-50%) AND A MARGINAL INCREASE OF NOX (1%-6% WHEN IT IS USED AS AN ALTERNATIVE FUEL IN A CI ENGINE.
• THE MAJOR PROBLEMS ASSOCIATED WITH BIO DIESEL ARE (I) POOR OXIDATION STABILITY, (II) HIGHER VISCOSITY AND DENSITY, (III) LOWER CALORIFIC VALUE, AND (IV) COLD FLOW PROPERTY.  -BLENDS OF 20% AND LOWER BIO DIESEL CAN BE USED IN DIESEL ENGINES WITH NO, OR ONLY MINOR MODIFICATIONS.

BIOGAS:

• PRODUCED BY THE ANAEROBIC DECOMPOSITION OF ORGANIC MATERIALS SUCH AS COW DUNG AND OTHER WASTE SUCH AS CORN HUSKS, LEAVES, STRAW, GARBAGE, FLESH OF CAR CUSSES, POULTRY DROPPINGS, PIG DUNG, HUMAN EXCRETA, SEWAGE AND THE PLANTS SPECIALLY GROWN FOR THIS PURPOSE LIKE WATER HYACINTH, ALGAE, CERTAIN TYPES OF GRASSES. ALSO ANY CELLULOSIC ORGANIC MATERIAL OF ANIMAL OR PLANT ORIGIN WHICH IS EASILY BIO-DEGRADABLE IS A POTENTIAL RAW MATERIAL FOR BIO-GAS PRODUCTION. ALSO PRODUCED BY PYROLYSIS AND HYDRO GASIFICATION METHODS.
• CONTAINS A MIXTURE OF METHANE (50-60% VOL), CO2 (30-45%), HYDROGEN (5-10%), NITROGEN (0.5-7%) AND SMALL TRACES OF OTHER GASES SUCH AS HYDROGEN SULPHIDE AND OXYGEN.
• IT IS A CLEAN, BUT SLOW BURNING GAS AND HAVING VALUE BETWEEN 5000 TO 5500 KCAL/KG OR 38131 KJ/M3 -THE OCTANE RATING OF BIOGAS IS 130 AND IGNITION TEMPERATURE IS 650 °C.
• CAN BE USED TO OPERATE BOTH COMPRESSION IGNITION (DIESEL) AND SPARK IGNITION (PETROL) ENGINES. CI ENGINES CAN OPERATE ON DUAL-FUEL (BIOGAS+DIESEL) OPERATION AND PILOT INJECTION OPERATION IN WHICH SMALL QUANTITY OF DIESEL IS REQUIRED FOR IGNITING THE MIXTURE OF AIR AND BIOGAS
• 80% SAVING OF DIESEL OIL CAN BE ACHIEVED.

HYDROGEN:

• CLEAN BURNING FUEL AND HAS THE HIGHEST ENERGY CONTENT PER UNIT MASS OF ANY CHEMICAL FUELS WHICH CAN REDUCE THE DEPENDENCY ON HYDROCARBON BASED FUELS.

PRODUCTION:

• MOST COMMON METHOD OF PRODUCING HYDROGEN INVOLVES SPLITTING WATER (H₂O) INTO ITS COMPONENT PARTS OF HYDROGEN (H₂) AND OXYGEN (O). THERE ARE DIFFERENT METHODS TO PRODUCE HYDROGEN.
• STEAM REFORMATION OR PARTIAL OXIDATION OF HYDROCARBONS SUCH AS NATURAL GAS, NAPHTHA OR CRUDE OIL. IT CONVERTS METHANE INTO HYDROGEN AND CARBON MONOXIDE BY REACTION WITH STEAM OVER A NICKEL CATALYST.
• COAL GASIFICATION- HYDROGEN MADE FROM COAL CAN PROBABLY BE JUSTIFIED AS A FUEL FOR SPECIAL APPLICATIONS WHERE THE UNIQUE CHARACTERISTICS OF HYDROGEN CAN BE PUT TO ADVANTAGE SUCH AS ITS WEIGHT OR ITS NON-POLLUTING CHARACTERISTICS.
• ELECTROLYSIS- IT USES ELECTRICAL CURRENT TO SPLIT WATER INTO HYDROGEN AT THE CATHODE (+) AND OXYGEN AT ANODE (-).
• THERMO CHEMICAL METHOD- IT UTILIZES HEAT TO ACHIEVE THE CHEMICAL SPLITTING OF WATER TO ITS ELEMENTS WITHOUT THE NEED FOR INTERMEDIATE ELECTRICITY GENERATION AND WITHOUT THE NEED TO USE THE EXTREMITY HIGH TEMPERATURE OF 2500 °C OR MORE.
• PHOTO-ELECTROLYSIS- IT USES SUNLIGHT AND CATALYSTS TO SPLIT WATER. IN THIS METHOD, A CURRENT IS GENERATED BY EXPOSING ON OR BOTH.
• ELECTRODES TO SUNLIGHT. HYDROGEN AND OXYGEN GASES ARE LIBERATED AT THE 2 ELECTRODES BY THE DECOMPOSITION OF WATER. A CATALYST MAY BE INCLUDED TO FACILITATE THE ELECTRODE PROCESS.
• BIOLOGICAL AND PHOTO-BIOLOGICAL WATER SPLITTING USE SUNLIGHT AND BIOLOGICAL ORGANISMS TO SPLIT WATER.
• THERMAL WATER SPLITTING USES A VERY HIGH TEMPERATURE (APPROXIMATELY 1000 °C) TO SPLIT WATER.
• BIOMASS GASIFICATION USES SELECTED MICROBES TO BREAK DOWN A VARIETY OF BIOMASS FEED STOCKS INTO HYDROGEN.

UTILIZATION OF HYDROGEN GAS:

HYDROGEN CAN BE UTILIZED FOR THE FOLLOWING PURPOSE:

• RESIDENTIAL USE- HYDROGEN CAN BE USED IN DOMESTIC COOKING (STOVES), RADIANT SPACE HEATERS, ELECTRICITY FOR LIGHTING AND FOR OPERATING DOMESTIC APPLIANCES (E.G. REFRIGERATOR) WHICH COULD BE GENERATED BY MEANS OF FUEL CELLS, WITH HYDROGEN GAS AT ONE ELECTRODE AND AIR AT OTHER.

• INDUSTRIAL USE- HYDROGEN CAN BE USED AS A FUEL OR A CHEMICAL REDUCING (I.E. OXYGEN REMOVAL) AGENT. IT CAN ALSO BE USED INSTEAD OF COAL OR COAL DERIVED GASES, TO REDUCE OXIDE ORES (IRON ORE) TO THE MATERIAL (IRON).

• AIR CRAFT APPLICATION- THE EARLIEST APPLICATION OF LIQUID HYDROGEN FUEL IS EXPECTED TO BE IN A JET AIR CRAFT. COLD LIQUID HYDROGEN CAN BE USED DIRECTLY OR INDIRECTLY TO COOL THE ENGINE AND THE AIR FRAME SURFACES OF A HIGH SPEED AIR CRAFT.

• ELECTRIC POWER GENERATION- IT COMPRISES THE PRODUCTION OF ELECTRICITY BY USING HYDROGEN IN FUEL CELL SYSTEM. HYDROGEN COULD ALSO BE USED AS A MEANS FOR STORING AND DISTRIBUTING ELECTRICAL ENERGY. THE OBJECTIVE OF DEVELOPING FUEL CELL POWER STATIONS IS TO CENTRALIZED AND LOCAL GENERATION OF ELECTRICITY.

• AS AN ALTERNATIVE TRANSPORT FUEL- HYDROGEN IS TRIED AS AN ALTERNATIVE FUEL IN INTERNAL COMBUSTION ENGINE. THE STOICHIOMETRIC HYDROGEN AIR MIXTURE BURNS SEVEN TIMES AS FAST AS THE CORRESPONDING GASOLINE AIR MIXTURE WHICH IS A GREAT ADVANTAGE IN INTERNAL.

• COMBUSTION ENGINES, LEADING TO HIGHER ENGINE SPEEDS AND GREATER THERMAL EFFICIENCY. HYDROGEN FUEL USED IN IC ENGINES IS IN AUTOMOBILES, BUSES, TRUCKS AND FARM MACHINERY.

METHODS OF USING HYDROGEN AS A FUEL IN CI ENGINES

• A MIXTURE OF FUEL GAS AND AIR, WITH AN APPROXIMATELY CONSTANT FUEL TO AIR RATIO IS INTRODUCED INTO THE CYLINDER INTAKE MANIFOLD. THE ENGINE POWER IS CONTROLLED BY VARYING THE QUANTITY OF MIXTURE ENTERING THE CYLINDER BY MEANS OF THROTTLE VALVE. IT IS NOT SAFE BECAUSE THE MIXTURE IS FORMED IN THE MANIFOLD.
• THE HYDROGEN IS INJECTED DIRECTLY INTO THE ENGINE CYLINDER THROUGH A VALVE UNDER PRESSURE AND AIR IS INDUCTED THROUGH ANOTHER INTAKE VALVE. THIS METHOD IS SAFER ONE, SINCE HYDROGEN AND AIR ARE SUPPLIED SEPARATELY; AN EXPLOSIVE MIXTURE IS OCCURRED INSIDE THE CYLINDER ONLY. THE ENGINE POWER OUTPUT IS CONTROLLED BY VARYING THE PRESSURE OF HYDROGEN GAS FROM ABOUT 14 ATM AT LOW POWER TO 70 ATM AT HIGH POWER.
• DURING THE INTAKE STROKE, THE HYDROGEN GAS AT NORMAL OR MODERATE PRESSURE IS DRAWN THROUGH THE THROTTLE VALVE INTO THE ENGINE CYLINDER WHEREAS UNTHROTTLED AIR IS DRAWN IN THROUGH THE INTAKE PORT. THE VARIATION OF ENGINE POWER CAN BE ACHIEVED WITH ADJUSTMENT OF HYDROGEN INLET THROTTLE. THE CHANGES IN FUEL PROPORTION AS WELL AS POWER IS DEVELOPED DUE TO SUPPLY OF UN THROTTLE AIR AND POWER VARIATION IS POSSIBLE BECAUSE OF THE WIDE COMPOSITION RANGE OVER WHICH HYDROGEN-AIR MIXTURE CAN BE IGNITED.

ADVANTAGES OF USING HYDROGEN FUELED ENGINE:

• IT PROVIDES HIGH EFFICIENCY BECAUSE IT UTILIZES A HIGHER PROPORTION OF THE ENERGY IN THE FUEL.
• THE AMOUNT OF CARBON MONOXIDE AND HYDROCARBONS IN THE EXHAUST IS VERY SMALL SINCE THEY ARE ORIGINATING ONLY FROM THE CYLINDER LUBRICATING OIL.
• IT CAN BE EASILY AVAILABLE BECAUSE IT IS PRODUCED BY ELECTROLYSIS OF WATER.
• FUEL LEAKAGE TO ENVIRONMENT IS NOT POLLUTANT.

DISADVANTAGES OF USING HYDROGEN FUELLED ENGINE

• DUE TO HIGH HEAT RELEASE THE COMBUSTION TEMPERATURE MAY BE HIGH AND A LEVEL OF NITROGEN OXIDE IS HIGH. IT CAN BE REDUCED BY REDUCING THE COMBUSTION TEMPERATURE BY INJECTING WATER VAPOR INTO THE CYLINDER FROM THE EXHAUST.
• IT REQUIRES HEAVY, BULKY FUEL STORAGE BOTH IN VEHICLE AND AT THE SERVICE STATION.
• DIFFICULTY IN REFUELING AND POSSIBILITY OF DETONATION.
• POOR ENGINE VOLUMETRIC EFFICIENCY- GASEOUS FUEL WILL DISPLACE SOME OF INLET AIR AND POOR VOLUMETRIC EFFICIENCY WILL RESULT.
• FUEL COST WOULD BE HIGH AT PRESENT DAY TECHNOLOGY.

NATURAL GAS:

• NATURAL GAS IS PRESENT IN THE EARTH AND IS OFTEN PRODUCED IN ASSOCIATION WITH THE PRODUCTION OF CRUDE OIL. PROCESSING IS REQUIRED TO SEPARATE THE GAS FROM PETROLEUM LIQUIDS AND TO REMOVE CONTAMINANTS. FIRST, THE GAS IS SEPARATED FROM FREE LIQUIDS SUCH AS CRUDE OIL, HYDROCARBON CONDENSATE, WATER AND ENTRAINED SOLIDS. THE SEPARATED GAS IS FURTHER PROCESSED TO MEET CERTAIN PIPELINES QUALITY SPECIFICATIONS WITH RESPECT TO WATER CONTENT, HYDROCARBON DEW POINT, HEATING VALUE AND HYDROGEN SULPHIDE CONTENT. GENERALLY, A GAS SWEETENING PLANT REMOVES HYDROGEN SULPHIDE AND OTHER SULFUR COMPOUNDS.
• OVER 70% OF THE NATURAL GAS IS FORMED BY METHANE.
• IT IS COLORLESS, ODORLESS AND MOSTLY CONSTITUTES METHANE WHICH IS A RELATIVELY UNREACTIVE HYDROCARBON.

UTILIZATION:

• NATURAL GAS IS WIDELY USED FOR DIFFERENT PURPOSES SUCH AS SPACE HEATING, ELECTRICITY GENERATION, INDUSTRIAL PROCESSES, AGRICULTURAL, RAW MATERIAL FOR PETROCHEMICAL INDUSTRY, RESIDENTIAL, COMMERCIAL AND UTILITY MARKETS.
• ON A GALLON EQUIVALENT BASIS, NATURAL GAS COSTS LESS THAN GASOLINE, DIESEL FUEL OR ANY OTHER ALTERNATIVE FUEL. NATURAL GAS CURRENTLY SUPPLIES OVER 25% OF THE ENERGY DEMAND BECAUSE OF ITS QUALITY.
• CAN EITHER BE STORED ON BOARD A VEHICLE IN TANKS AS COMPRESSED NATURAL GAS (CNG) AT PRESSURE OF 16 TO 25 BAR OR CRYOGENICALLY COOLED TO A LIQUID STATE (-127 °C) AS LIQUEFIED NATURAL GAS (LNG) AT PRESSURE OF 70 TO 120 BAR. AS A FUEL AND WITH A SINGLE THROTTLE BODY INJECTOR IT WORKS BEST IN AN ENGINE SYSTEM. LNG IS USED IN HEAVY DUTY VEHICLES WHERE USE OF CNG WOULD STILL ENTAIL SPACE AND LOAD CARRYING CAPACITY PENALTIES. THE FUEL STORAGE SYSTEM OF NATURAL GAS AS LNG INSTEAD OF CNG IS LESS THAN HALF THE WEIGHT AND VOLUME OF CNG SYSTEM. SO, IT CAN BE EASILY TRANSPORTABLE THAN CNG.

CNG (COMPRESSED NATURAL GAS):

• NATURAL GAS CONSISTS OF ELEMENTS OF COMPRESSOR, SOME SORT OF COMPRESSED GAS STORAGE AND DISPENSING UNIT OF CNG INTO VEHICLES.
• TWO TYPES OF CNG REFUELING SYSTEM- SLOW FILL AND FAST FILL. IN SLOW FILL SYSTEM, SEVERAL VEHICLES ARE CONNECTED TO THE OUTPUT OF THE COMPRESSOR AT ONE TIME. THESE VEHICLES ARE THEN REFILLED OVER SEVERAL HOURS OF COMPRESSOR OPERATION. IN FAST FILL SYSTEMS, ENOUGH CNG IS STORED SO THAT SEVERAL VEHICLES CAN BE REFUELED ONE AFTER THE OTHER, JUST LIKE REFUELING FROM A SINGLE GASOLINE DISPENSER.
• THE STORAGE SYSTEM OF CNG IS ARRANGED AS SEVERAL TANKS IN CASCADE FORM. THE CNG PRESSURE IN CASCADE IS HIGHER THAN THE MAXIMUM STORAGE PRESSURE OF THE CYLINDER ON THE VEHICLE. THE CASCADE ATTEMPTS TO DELIVER AS MUCH OF ITS CNG TO VEHICLES AS POSSIBLE BEFORE THE PRESSURE DIFFERENCE DECREASES TO WHERE THE FLOW RATE SLOWS DRAMATICALLY. A DRYER SHOULD INCLUDE IN MOST CNG REFUELING SYSTEMS TO REMOVE WATER VAPOR, IMPURITIES AND HYDROGEN SULPHIDE FROM NATURAL GAS BEFORE IT IS COMPRESSED. IF WATER VAPOR IS PRESENT THEN IT CAN CONDENSE IN THE VEHICLE FUEL SYSTEM, CAUSING CORROSION ESPECIALLY IF HYDROGEN SULPHIDE IS PRESENT. CNG DRIVEN VEHICLES WITH CATALYTIC CONVERTER HAVE LESS CO AND HC EMISSION BUT NOX EMISSION IS HIGH.

LPG (LIQUEFIED PETROLEUM GAS):

• LPG IS AVAILABLE IN THE MARKET IN TWO FORMS- ONE IS PROPANE AND THE OTHER IS BUTANE. PROPANE IS POPULAR ALTERNATIVE FUEL BECAUSE OF ITS INFRASTRUCTURE OF PIPE LINES, PROCESSING FACILITIES AND STORAGE FOR ITS EFFICIENT DISTRIBUTION AND IT PRODUCES FEWER EMISSIONS. PROPANE IS PRODUCED AS A BYPRODUCT OF NATURAL GAS PROCESSING AND CRUDE OIL REFINING.
• NATURAL GAS CONTAINS LPG, WATER VAPOR AND OTHER IMPURITIES AND ABOUT 55% OF THE LPG IS COMPRESSED FROM NATURAL GAS PURIFICATION. LPG IS A SIMPLE MIXTURE OF HYDROCARBON MAINLY PROPANE/PROPYLENE (C3S) AND BUTANE/ BUTYLENES (C₄S).
• PROPANE IS AN ODORLESS, NONPOISONOUS GAS WHICH HAS LOWEST FLAMMABILITY RANGE.

UTILIZATION OF LPG:

• LPG IS USED AS A FUEL IN HEATING APPLIANCES AND VEHICLES. IT IS INCREASINGLY USED AS AN AEROSOL PROPELLANT AND A REFRIGERANT, REPLACING CHLOROFLUOROCARBONS TO REDUCE DAMAGE TO THE OZONE LAYER.
• IN EUROPE, LPG IS USED AS AN ALTERNATIVE TO ELECTRICITY AND HEATING OIL (KEROSENE).IT CAN ALSO BE USED AS POWER SOURCE FOR COMBINED HEAT AND POWER TECHNOLOGIES (CHP). CHP IS THE PROCESS OF GENERATING BOTH ELECTRICAL POWER AND USEFUL HEAT FROM A SINGLE FUEL SOURCE. THIS TECHNOLOGY HAS ALLOWED LPG TO BE USED NOT JUST AS FUEL FOR HEATING AND COOKING, BUT ALSO FOR DE-CENTRALIZED GENERATION OF ELECTRICITY.
• LPG HAS HIGHER POTENTIAL AS AN ALTERNATE FUEL FOR IC ENGINE.

ADVANTAGES OF LPG:

• EMISSION IS MUCH REDUCED USING LPG.
• LPG MIXES WITH AIR AT ALL TEMPERATURES.
• UNIFORM MIXTURE CAN BE SUPPLIED TO ALL CYLINDERS OF MULTI-CYLINDER ENGINE.
• ENGINE WITH HIGH COMPRESSION RATIO (10:1) CAN USE PROPANE.
• THERE IS COST SAVING OF ABOUT 50% AND LONGER LIFE WITH LPG RUNNING ENGINE.

DISADVANTAGES OF LPG:

• A GOOD COOLING SYSTEM IS NECESSARY BECAUSE LPG VAPORIZER USES ENGINE COOLANT TO PROVIDE THE HEAT TO CONVERT THE LIQUID LPG TO GAS.
• THE WEIGHT OF VEHICLE IS INCREASED DUE TO THE USE OF HEAVY PRESSURE CYLINDER FOR STORING LPG.
• A SPECIAL FUEL FEED SYSTEM IS REQUIRED FOR LPG.
• REQUIREMENT OF SAFETY DEVICE TO PREVENT ACCIDENT DUE TO EXPLOSION OF GAS CYLINDERS OR LEAKAGE IN THE GAS PIPES.

PRODUCER GAS:

• PRODUCER GAS IS A PRODUCT OF OXIDATION-REDUCTION REACTIONS OF AIR WITH BIOMASS. BIOMASS IS CHEMICALLY COMPOSED OF ELEMENTS C, H, O AND SOME N AND HENCE THE OXIDATION RESULTS IN PRODUCTS OF COMBUSTION LIKE CO2 AND H2O. THE MOLECULES OF O2 IN THE AIR OXIDISES C AND H TO PRODUCE THESE PRODUCTS. THE GASES WHICH ARE AT HIGH TEMPERATURE DUE TO PARTIAL OXIDATION PASS THROUGH A BED OF CHARCOAL (WHICH IS PRODUCED BECAUSE OF OXIDATION REACTION ITSELF) AND THE REDUCTION REACTION OF THESE GASES WITH CARBON LEADS TO CARBON MONOXIDE AND HYDROGEN.
• VOLUMETRIC COMPOSITION OF PRODUCER GAS IS CO (16-20%), H2 (16-18%), CO2 (8-10%) AND SOME TRACES OF HIGHER HYDROCARBONS. PRODUCER GAS HAS A HIGH PERCENTAGE OF N2, SINCE AIR IS USED. SO IT HAS A LOW HEAT VALUE. DENSITY OF PRODUCER GAS IS 0.9 TO 1.2 KG/M3.
• PRODUCER GAS IS USED IN RECIPROCATING ENGINES AND FURNACE. IT NEEDS LITTLE AIR TO BURN STOICHIOMETRICALLY AND RAISE THE TEMPERATURE TO A VALUE OF 1500 K AT NORMAL TEMPERATURE AND PRESSURE. IT IS ALSO USED TO POWER GAS TURBINES (WHICH ARE WELL-SUITED TO FUELS OF LOW CALORIFIC VALUE), SPARK IGNITED ENGINES (WHERE 100% PETROL FUEL REPLACEMENT IS POSSIBLE) OR DIESEL INTERNAL COMBUSTION ENGINES (WHERE 40% - 15% OF THE ORIGINAL DIESEL FUEL) IS STILL USED TO IGNITE THE GAS.

BLAST FURNACE GAS:

• IT IS A BYPRODUCT OF MELTING IRON ORE IN STEEL PLANTS. IT PRINCIPALLY CONSISTS OF CO AND CONTAINS LOW HEAT VALUE LIKE PRODUCER GAS. IT CONSISTS OF ABOUT 60% NITROGEN, 18-20% CO2 AND SOME AMOUNT OF OXYGEN WHICH ARE NOT FLAMMABLE. IT MAY BE COMBINED WITH NATURAL GAS OR COKE OVEN GAS BEFORE COMBUSTION OR A FLAME SUPPORT WITH RICHER GAS OR OIL IS PROVIDED TO SUSTAIN COMBUSTION. THE AUTO IGNITION TEMPERATURE OF BLAST FURNACE GAS IS APPROXIMATE 630 °C AND IT HAS LOWER EXPLOSIVE LIMIT (LEL) OF 27% &UPPER EXPLOSIVE LIMIT (UEL) OF 75% IN AN AIR-GAS MIXTURE AT NORMAL TEMPERATURE AND PRESSURE. THE GAS IS HAZARDOUS DUE TO HIGHER CONCENTRATION OF CARBON MONOXIDE [50].IT SHOULD BE CLEANED PROPERLY BECAUSE IT CONTAINS LOT OF DUST PARTICLES. BLAST FURNACE GAS DEPENDS UPON TYPES OF FUEL USED AND METHOD OF OPERATING THE BLAST FURNACE.

COKE OVEN GAS:

• IT IS PRODUCED DURING THE MAKING OF COKE. IT IS ALSO RESULTING FROM OXIDATION-REDUCTION REACTIONS OF COAL OR COKE WITH AIR AND SOMETIMES STEAMS. IT DEPENDS UPON THE TYPE OF COAL USED AND OPERATION METHOD OF OVEN. THE COMPOSITION OF COKE OVEN GAS IS H2 (54% VOL), CH4 (24%), CO (8%), CO2 (6%) AND SOME TRACES OF HIGHER HYDROCARBON AND NITROGEN. WITH THE APPLICATION OF HEAT, THE HEAVIER HYDROCARBONS ARE CRACKED AND VOLATILE PORTION OF COAL IS DRIVEN OFF AND RESULTS IN HIGH COMPOSITION OF H2AND CH4. ITS HEAT VALUE PER CUBIC METER IS ONLY ABOUT ONE HALF THAT OF NATURAL GAS AND DENSITY IS 0.40 KG/M3.