Unit I

1. Unit I

2. Fuel • Combustion Stoichiometry • Air/Fuel Ratio • Equivalence Ratio • Air Pollutants from Combustion Combustion Basics

3. Gaseous Fuels • Natural gas • Refinery gas • Liquid Fuels • Kerosene • Gasoline, diesel • Alcohol (Ethanol) • Oil • Solid Fuels • Coal (Anthracite, bituminous, subbituminous, lignite) • Wood Fuel

4. Properties of Selected Fuels CH4 C2H6 C3H8 Other HCs H2S Heating Value (wt%) (106 J/m3) Natural gas (No.1) 87.7 5.6 2.4 1.8 2.7 43.2 Natural gas (No.2) 88.8 6.4 2.7 2.0 0.0004 41.9 (Ultimate analysis) C H N O S Heating value (wt%) (106 J kg-1) Gasoline (No.2) 86.4 12.7 0.1 0.1 0.4-0.7 (Approximate analysis) Carbon Volatile matter Moisture Ash Heating value (%) (%) (%) (%) (106 J kg-1) Anthracite (PA) 77.1 3.8 5.4 13.7 27.8 Bituminous (PA) 70.0 20.5 3.3 6.2 33.3 Subbituminous (CO) 45.9 30.5 19.6 4.0 23.6 Lignite (ND) 30.8 28.2 34.8 6.2 16.8 Fuel Which one has a higher energy density per mass? Do they burn in the same way? Data from Flagan and Seinfeld, Fundamentals of Air Pollution Engineering, 1988, Prentice-Hall.

5. Combustion in Oxygen • Can you balance the above equation? • Write the reactions for combustion of methane and benzene in oxygen, respectively. Answer Combustion Stoichiometry

6. Combustion in Air (O2 = 21%, N2 = 79%) • Can you balance the above equation? • Write the reactions for combustion of methane and benzene in air, respectively. Answer Combustion Stoichiometry 1. What if the fuel contains O, S, Cl or other elements? 2 Is it better to use O2 or air?

7. Air-Fuel (AF) ratio • AF = m Air / m Fuel • Where: m air = mass of air in the feed mixture • m fuel = mass of fuel in the feed mixture • Fuel-Air ratio: FA = m Fuel /m Air = 1/AF • Air-Fuel molal ratio • AFmole = nAir / nFuel • Where: nair = moles of air in the feed mixture • nfuel = moles of fuel in the feed mixture Air-Fuel Ratio What is the Air-Fuel ratio for stoichiometric combustion of methane and benzene, respectively? Aerosol & Particulate Research Laboratory

8. Rich mixture - more fuel than necessary • (AF) mixture < (AF)stoich • Lean mixture • - more air than necessary • (AF) mixture > (AF)stoich Air-Fuel Ratio Most combustion systems operate under lean conditions. Why is this advantageous? Consider the combustion of methanol in an engine. If the Air-Fuel ratio of the actual mixture is 20, is the engine operating under rich or lean conditions? Aerosol & Particulate Research Laboratory

9. Equivalence ratio: shows the deviation of an actual mixture from stoichiometric conditions. The combustion of methane has an equivalence ratio Φ=0.8 in a certain condition. What is the percent of excess air (EA) used in the combustion? How does temperature change as Φ increases? Equivalence Ratio Aerosol & Particulate Research Laboratory

10. Thermal NOx • Oxidation of atmospheric N2 at high temperatures • Formation of thermal NOx is favorable at higher temperature • Fuel NOx • Oxidation of nitrogen compounds contained in the fuel • Formation of CO • Incomplete Combustion • Dissociation of CO2 at high temperature Formation of NOx and CO in Combustion Aerosol & Particulate Research Laboratory

11. Air Pollutants from Combustion Source: Seinfeld, J. Atmospheric Chemistry and Physics of Air Pollution. How do you explain the trends of the exhaust HCs, CO, and NOx as a function of air-fuel ratio? How do you minimize NOx and CO emission?

12. Fuel • Combustion Stoichiometry • Air/Fuel Ratio • Equivalence Ratio • Air Pollutants from Combustion Quick Reflections

13. Engine Fuel System (SI Petrol) • Fuel Tank – normally positioned in the rear boot area, either under the floor pan for estate cars or over the rear axle for saloons, the latter being a safer position. Should the engine be mounted in the rear, the fuel tank is normally positioned in the front boot area, either over the bulkhead or flat across the boot floor pan , the latter providing more boot space, but is more exposed to danger in a head on crash. The fuel tank made be made from pressed steel and coated inside to prevent corrosion, or a synthetic rubber compound or flame resistant plastic. Inside the fuel tank is normally located the fuel gauge sender unit and electrically driven fuel pump with a primary filter in a combined module. Internal fuel tank baffles are used to prevent fuel surge. The fuel tank is pressurised to about 2 psi to prevent fuel vaporization and pollution. The fuel tank is vented through its own venting system and the engine managements emission control systems again to control pollution. • Fuel pipes – These can be made from steel or plastic and are secured by clips at several points along the underside of the vehicle. To allow for engine movement and vibration, rubber hoses connect the pipes to the engine. Later fuel pipes use special connectors which require special tools to disconnect the pipes.

14. Engine Fuel System (SI Petrol) • Fuel Filters – to prevent dirt and fluff entering the fuel pump a filter is fitted on the suction side of the pump. On the pressure side of the pump a secondary filter is used, this is a much finer filter in that it prevents very small particles of dirt reaching the carburettor or fuel injection equipment. It should be renewed at the correct service interval as recommended by the manufacturer. When the filter is replaced, it must be fitted in the direction of fuel flow. • Air Filters – air cleaners and silencers are fitted to all modern vehicles. Its most important function is to prevent dust and abrasive particles from entering the engine and causing rapid wear. Air filters are designed to give sufficient filtered air, to obtain maximum engine power. The air filter must be changed at the manufactures recommended service interval. The air filter/cleaner also acts as a flame trap and silencer for the air intake system. • Fuel Pump – this supplies fuel under high pressure to the fuel injection system, or under low pressure to a carburettor. • Carburettor – this is a device which atomizes the fuel and mixes it which the correct amount of air, this device has now been superseded by modern electronic fuel injection.

15. Petrol Petrol

16. Float chamber (function) – to set and maintain the fuel level within the carburettor, and to control the supply fuel to the carburettor venturi. • Operation – when air passes through the venturi due to the engines induction strokes, it creates a depression (suction), around the fuel spray outlet. Atmospheric pressure is acting on the fuel in the float chamber, the difference in theses pressures causes the fuel to flow from the float chamber, through the jet and into the stream. This causes the petrol to mix with the air rushing in to form a combustible mixture. The required air fuel ratio can be obtained by using a jet size which allows the correct amount of fuel to flow for the amount of air passing through the • Defects of the simple carburettor. • As engine speed increases, air pressure and density decreases i.e. the air gets thinner, however the quantity of fuel increases i.e. greater pressure exerted on the fuel, this causes the air/fuel mixture to get progressively richer (to much fuel). • As the engine speed decreases, the air/fuel mixture becomes progressively weaker. Some form of compensation is therefore required so that the correct amount of air and fuel is supplied to the engine under all operating conditions.

17. The Simple Carburettor The Float Chamber Petrol Operation of the Venturi Choke Valve closed The Throttle Valve controls the amount of air fuel mixture entering the engine and therefore engine power The Choke Valve is used to provide a rich air/fuel ratio for cold starting

22. Air Fuel Ratio • Fuel mixture strengths – petrol will not burn unless it is mixed with air, to obtain the best possible combustion of the fuel, which should result in good engine power and fuel consumption and low emissions (pollution), the air fuel ratio must be chemically correct i.e. the right amount of air and fuel must be mixed together to give an air fuel ratio of 14.7 to 1 by mass. This is referred to as the shoitcmetreic air fuel ratio, this ratio can also be describe by the term Lambda. Lamba is the Greek word meaning ‘air’. When their is more air present than fuel in the air fuel mixture, it is said to be ‘weak’ or ‘lean’ i.e. not enough fuel e.g. a ratio of 25 to 1, this results in a Lambda reading of more than 1.When their is not enough air present, the mixture is referred to as ‘rich’ e.g. a air fuel ratio of 8 to 1, in this case Lambda equals less than 1. • Weak/lean air/fuel mixtures – can result in low fuel consumption, low emissions (pollution), however, weak air fuel mixtures can also result in poor engine performance (lack of power) and high engine temperatures ( because the fuel burns more slowly) • Rich air/ fuel mixtures – can result in greater engine power, however this also results in poorer fuel consumption and greatly increased emissions (pollution)

23. Engine S I Fuel System • ECU – Electronic control unit. This contains a computer which takes information from sensors and controls the amount of fuel injected by operating the injectors for just the right amount of time. • Air flow/mass meter – A sensor used to tell the ECU how much air is being drawn into the engine. • MAP sensor – Manifold absolute pressure sensor. This senses the pressure in the engines inlet manifold, this gives an indication of the load the engine is working under. • Speed/crankshaft sensor – This tells the ECU has fast the engine is rotating and sometimes the position of the crankshaft. • Temperature sensor – Coolant temperature is used determine if more fuel is needed when the engine is cold or warming up. • Lambda sensor – A sensor located in the exhaust system which tells the ECU the amount of oxygen in the exhaust gases, form this the ECU can determine if the air/fuel ratio is correct. • Fuel pump – A pump, normally located in the fuel tank, which supplies fuel under pressure to the fuel injectors.

24. Engine S I Fuel System • Fuel filter – keeps the fuel very clean to prevent the injectors becoming damaged or blocked. • Fuel rail – A common connection to multi point injectors, acts a reservoir of fuel (small tank of fuel). • Injector – A electrical device which contains a winding or solenoid. When turned on by the ECU, the injector opens and fuel is sprayed into the inlet manifold, or into the combustion chamber itself. • Idle actuator – A valve controlled by the ECU which controls the idle speed of the engine. • ECU – Electronic Unit. This contains a computer which takes information from sensors and controls the amount of fuel injected by operating the injectors for just the right amount of time. The ECU also controls the operation of the ignition and the other engine rated systems.

25. Typical Fuel System 1. Fuel Supply System Components that supply clean fuel to the fuel metering system (fuel pump, fuel pipes, fuel filters). 2. Air Supply System Components that supply controlled clean air to the engine (air filter, ducting, valves). 3. Fuel Metering System Components that meter the correct amount of fuel (and air) entering the engine (injectors, pressure regulator, throttle valve). The exact components used will vary with fuel system type and design. 25 of 14

26. Introduction to Electronic Petrol Throttle/Single Point Fuel Injection Systems The Carburettor has now been replaced with petrol injection systems. These systems supply the engine with a highly atomized mixture of air and fuel in the correct air/fuel ratio. This has the following advantages over the carburettor systems Lower exhaust emissions (pollution) Better fuel consumption Smoother engine operation and greater power Automatic adjustment of the air/fuel ratio to keep the vehicles emissions (pollution) to a minimum. 26 of 14

27. Air drawn in by the engine Throttle Body/Single Point S.I. Fuel Injection Throttle Body Fuel Supply Fuel Injector (one off) Throttle Valve Inlet Manifold The Engine

28. ECU Air in Fuel in TB injector Inlet manifold Single Point Electronic Fuel Injection (EFI) Systems EFI systems are classified by using the point of injection. Single Point (Throttle Body) Fuel Injection A fuel injector (may be 2) is located in a throttle body assembly that sits on top of the inlet manifold. Fuel is sprayed into the inlet manifold from above the throttle valve, mixing with incoming air. Fuel quantity, how much feul is injected is controlled by an ECU. 28 of 14

29. Electronic Fuel Injector Operation An injector sprays fuel into the inlet manifold by use of a solenoid coil. When the coil is switch on by the ECU, it pulls the armature/needle valve away from the nozzle, allowing pressurized fuel into the engine. When the coil is not switched on, the spring pushes the armature/needle against the nozzle, no fuel is injected into the inlet manifold Injectors are more precise and efficient than carburettors. Electrical connector Solenoid coil Needle valve Fuel in Spring Fuel filter Armature Nozzle/jet

30. Outputs Inputs Single Point Injection Sensor The ECU (Brain) receives Information from varies sensors. From this information it works out how much fuel the engine needs

31. Multi – Point S.I. Fuel Injection Air drawn in by the engine Fuel Injectors Throttle Valve Inlet Manifold Fuel Supply Injectors Engine

32. Typical S.I. Fuel System Layout (Simplified) Fuel Not used is returned to the fuel tank Engine Combustion Chamber Fuel Tank Fuel Pressure Regulator EFI Only Inlet Manifold Fuel Pump Carburettor Or Single Point Throttle Body Housing Fuel Filters Fuel Injector or Carburettor Venturi

33. Liquid fuel UNIT II

36. What is ethanol? • GM Commercial • CH3CH2OH • Ethanol is a clean-burning, high-octane fuel that is produced from renewable sources. • At its most basic, ethanol is grain alcohol, produced from crops such as corn. • Since pure 100% ethanol is not generally used as a motor fuel, a percentage of ethanol is combined with unleaded gasoline, to form E10 and E85 • E10: 10% ethanol and 90% unleaded gasoline, is approved for use in any US vehicle • E85: 85% ethanol and 15% unleaded gasoline, is an alternative fuel for use in flexible fuel vehicles (FFVs).

37. How is it made? • Ethanol can be made by fermenting almost any material that contains starch. • Most of the ethanol in the U.S. is made using a dry mill process. • In the dry mill process, the starch portion of the corn is fermented into sugar then distilled into alcohol • Prior to fermentation, high-value chemicals are removed from the biomass. These include fragrances, flavoring agents, food-related products, and high value nutraceuticals with health and medical benefits. • There are two main valuable co-products created in the production of ethanol: distillers grain and carbon dioxide. Distillers grain is used as a highly nutritious livestock feed while carbon dioxide is collected, compressed, and sold for use in other industries.

38. Energy Balance of Ethanol

39. Although CO2 is released during ethanol production and combustion, it is recaptured as a nutrient to the crops that are used in its production. Unlike fossil fuel combustion, which unlocks carbon that has been stored for millions of years, use of ethanol results in comparatively lower increases to the carbon cycle. Ethanol also degrades quickly in water and, therefore, poses a smaller risk to the environment than an oil or gasoline spill. Research studies from a variety of sources have found ethanol to have a positive net energy balance. The most recent, by the U.S. Department of Agriculture, shows that ethanol provides an average net energy gain of at least 77%. It takes less than 35,000 BTUs of energy to turn corn into ethanol, while the ethanol offers at least 77,000 BTUs of energy. Thus ethanol has a positive energy balance—meaning the ethanol yields more energy than it takes to produce it. Energy Balance

40. Impact on air quality • Using ethanol-blended fuel has a positive impact on air quality. By adding oxygen to the combustion process which reduces exhaust emissions—resulting in a cleaner fuel for cleaner air. • Ethanol reduces the emissions of carbon monoxide, VOX, and toxic air emissions: • Since ethanol is an alcohol based product, it does not produce hydrocarbons when being burned or during evaporation thus decreasing the rate of ground level ozone formation. • Ethanol reduces pollution through the volumetric displacement of gasoline. The use of ethanol results in reductions in every pollutant regulated by the EPA, including ozone, air toxins, carbon monoxide, particulate matter, and NOX.

41. Impact on energy independence • Since it is domestically produced, ethanol helps reduce America's dependence upon foreign sources of energy. U.S. ethanol production provides more than 4 billion gallons of renewable fuel for our country. • Current U.S. ethanol production capacity can reduce gasoline imports by more than one-third and effectively extend gasoline supplies at a time when refining capacity is at its maximum. • According to the Energy Information Administration, the 7.5 billion gallon ethanol production level in the recently enacted Renewable Fuels Standardcould reduce oil consumption by 80,000 barrels per day.

42. Impact on economy • In a 1997 study The Economic Impact of the Demand for Ethanol, Northwestern University’s Kellogg School of Management found that: • During ethanol plant construction, approximately 370 local jobs are created. • During ethanol plant operation, up to 4,000 local jobs are created. • Ethanol plant construction creates $60 million to $130 million in additional income. • Ethanol plant operation creates $47 million to $100 million in additional income. • American-made, renewable ethanol directly displaces crude oil we would need to import, offering our country critically needed independence and security from foreign sources of energy. • The U.S. Department of Agriculture has concluded that a 100 million gallon ethanol facility could create 2,250 local jobs for a single community. Ethanol production creates domestic markets for corn and adds 4-6 cents a bushel for each 100 million bushels used. Better prices mean less reliance on government subsidy programs not to mention higher income and greater independence for farmers.

43. Impact on auto industry • Ethanol could be the alternative fuel source that catapults sales of American auto manufacturers. • GM and Ford are looking for environmental fixes that are quicker and cheaper than the more costly hybrids and futuristic fuel cells. Both companies started promoting flexible-fuel vehicles (FFVs) aggressively this year. • General Motors tied their new campaign "Live Green, Go Yellow.'' to not only Super Bowl Sunday but the opening of the Winter Olympics as well. • Since only about 600 of the nation's 170,000 filling stations sell E85, both companies have begun programs to install E85 pumps at more stations.

44. Impact on politics • President Bush gave ethanol a big plug in his State of the Union address, by stating that: • The United States must move beyond a petroleum-based economy and develop new ways to power automobiles. The Administration will accelerate research in cutting-edge methods of producing "cellulosic ethanol" with the goal of making the use of such ethanol practical and competitive within 6 years. • The Biorefinery Initiative. To achieve greater use of "homegrown" renewable fuels in the United States, advanced technologies need to be perfected to make fuel ethanol from cellulosic (plant fiber) biomass, which is now discarded as waste. The President's 2007 Budget will include $150 million – a $59 million increase over FY06 – to help develop bio-based transportation fuels from agricultural waste products, such as wood chips, stalks, or switch grass. Research scientists say that accelerating research into "cellulosic ethanol" can make it cost-competitive by 2012, offering the potential to displace up to 30% of the Nation's current fuel use. • Associated Press, March 2, 2006: To increase the production of alternative fuel sources, the Bush administration has proposed allowing ethanol plants to emit more air pollutants. The EPA announced that it would propose a rule to raise the emissions threshold for corn milling plants that produce ethanol fuel, allowing them to emit up to 250 tons a year of air pollutants before setting off tougher restrictions on production. Corn milling plants can now emit 100 tons a year.

45. Problems with Ethanol • Odors as a public nuisance, ex: New Energy Ethanol Plant here in South Bend • Green house gas emissions have sometimes shown to be equivalent to those of gasoline (data is often inconclusive) • Environmental performance of ethanol varies greatly depending on the production process • Costs involved with building new facilities for ethanol production • New ways to maximize crop production are necessary • Research is needed to refine the chemical processes to separate, purify and transform biomass into usable fuel

46. Gaseous Fuels UNIT III

47. 1. Introduction • There are numerous factors which need to be taken into account when selecting a fuel for any give application. • Economics is the overriding consideration-the capital cost of the combustion equipment together with the running costs, which are fuel purchasing and maintenance.

48. 2. Natural Gas • Natural gas is obtained from deposits in sedimentary rock formations which are also sources of oil. • It is extracted from production fields and piped (at approximately 90 bar) to a processing plant where condensable hydrocarbons are extracted from the raw product.

49. It is then distributed in a high-pressure mains system. • Pressure losses are made up by intermediate booster stations and the pressure is dropped to around 2500 Pa in governor installations where gas is taken from the mains and enters local distribution networks.

50. The initial processing, compression and heating at governor installations uses the gas as an energy source. • The energy overhead of the winning and distribution of a natural gas is about 6% of the extracted calorific value.