Internal Combustion Engines

1. Internal Combustion Engines Faculty - Er. Ashis Saxena

2. Index Unit 1 • Introduction to I.C Engines • Fuels Unit 2 • SI Engines Unit 3 • CI Engines Unit 4 • Engine Cooling • Lubrication • Supercharging • Testing and Performance Unit 5 • Compressors

3. Unit - 1 Fuels Chapter – 1(b)

4. Fuels Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. Fuel releases its energy either through chemical means, such as burning, or nuclear means, such as nuclear fission or nuclear fusion. An important property of a useful fuel is that its energy can be stored to be released only when needed, and that the release is controlled in such a way that the energy can be harnessed to produce work.

5. Types of Fuels Fuels for engines are typically • Gaseous • Liquid • Originally solid also but now very rarely used. They may also be classified as: • Naturally available or • Artificially derived

6. 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

7. 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 non-hydrocarbons 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.

8. Natural Gas: Facts • Existence of natural gas was known to people of ancient Greece, India, and Persia, in the form of burning springs. These springs were created when fountains of natural gas, seeping out from cracks in the ground, were ignited due to lightning. • As per the data for 2006, Russia had the largest deposits of natural gas (27%). Middle Eastern countries have a total of about 40% of the world's share of natural gas reserves, with Iran having almost a 14% share. • There are over a million miles of gas pipelines laid, needed to meet the energy needs of the US alone. • It was used for the first time in the US in 1816, to light street lights in Baltimore.

9. Natural Gas: Facts • Over 90% of the gas requirements of the US are fulfilled from deposits found in the country itself. • It is the third most widely used fuel in the US, after petroleum and coal. • According to the Energy Information Administration, natural gas provides for 24% of the total energy needs of US. • More than 62% homes in the country rely on natural gas to run stoves, water heaters, furnaces and other home appliances. • Industries are the largest consumers of natural gas. Besides being used to produce energy by industries, natural gas is also used as an ingredient in the manufacture of fertilizers, paints, ink and glue. • It can be used in fuel cells to produce electricity, in place of batteries. This may increase the efficiency of electricity generation.

10. Natural Gas: Facts • Although natural gas pipelines and storage facilities have high standards of safety, companies add a smelly substance to it, so that the leakage of this colorless, odorless gas can be identified. • The energy content of natural gas is measured in terms of British Thermal Unit (BTU). One BTU is said to be the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. In the US, however, retail sales are done in units of Therms. 1 Therm = 1028 BTU. • Despite its various uses one of the major disadvantages of natural gas is that it is highly combustible, due to which explosions are very likely. • The gas requires sophisticated treatment plants and underground pipelines to be delivered to the site where it will be used. These installations are expensive and require high maintenance.

11. Use of Natural Gas as a fuel 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).

12. Natural Gas in Engines • When an engine was switched over to CNG from gasoline, the non-methane organic gases like 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. • For heavy-duty applications, dual fuel operation is attractive, for buses, locomotives, ships, compressors and generators.

13. Natural Gas: Advantages • Is more environment friendly than oil or coal. It is largely because of the fact that it has only one carbon and hence, produces less emissions. It is a known fact that for the same amount of heat it emits 30% less carbon dioxide than burning oil, and 45% less carbon dioxide than burning coal, thereby improving the quality of air. • Is cheap (less expensive than gasoline) and therefore cost-effective. • Can be safely stored and burned. • The process of easily transporting natural gas over land through pipelines or over water bodies in the form of LNG (Liquid Natural Gas) is an added pro - it doesn't require high costs.

14. Natural Gas: Advantages • Most of its natural reserves are still underutilized. • Emits 60-90% less smog-producing pollutants. • Natural gas becomes a primary source of electricity during situations when demand runs high. • Due to the clean burning process, it doesn't produce ash after energy is released. • Has a high heating value of 24,000 Btu per pound. • It can provide as long as 24 hours of electricity throughout the week, where other sources of its kind do not match up to its endurance. • It is widely used as a primary source of heating whilst cooking

15. Natural Gas: Disadvantages • Because it is a non renewable source of energy, its availability is finite. Critics also point out that its extraction leaves large craters within the earth. • Is highly volatile (highly flammable), and can be dangerous if handled carelessly. • In gas pipelines, a substance (contains carbon monoxide) that has a strong odor is added to help detect a leak. But such substances may be harmful and cause deaths if not carefully handled. In fact, natural gas is the most common cause of carbon monoxide deaths. • Constructing and managing transportation pipelines costs a lot if not the transporting of the substance itself. • While it may give off lesser carbon dioxide than other sources of energy, it is nonetheless damaging the ecosystem. • It isn't used in vehicles as a primary source of fuel since it is a highly combustible substance.

16. Natural Gas: Constituents

17. CNG vs Automotive fuels

18. CNG vs Automotive fuels

19. Composition of typical crude oil • Carbon: 80-89% • Hydrogen: 12-14% • Nitrogen: 0.3-1.0% • Sulfur: 0.3-3.0% • Oxygen: 2.0-3.0% • Plus oxygenated compounds like phenols, fatty acids, ketones and metallic elements like vanadium and nickel.

20. Refining of crude oil

21. Refining of crude oil

22. Qualities of SI engine fuels • Petrol or gasoline is usually used as fuel for spark ignition (SI) engines There are certain properties that a particular gasoline should have to qualify as SI engine fuel which are: • Volatility: The gasoline should be volatile; a certain part of it should vaporize at room temperature to allow easy starting of the engine. Better vaporization of the fuel facilitates its even distribution inside the cylinders, which in turn leads to better acceleration of the vehicle. • Dilution of the lubricating oil in crankcase: As the fuel is splashed in the cylinder, some lubricating oil from the crankcase is also washed away with it. This leads to overall decrease in the quantity of the lubricating oil and poor lubrication of the engine's moving parts. To prevent such possibilities, it is important that the type of gasoline used for the engine should vaporize before it gets combusted.

23. Qualities of SI engine fuels • Antiknock qualities of the fuel: Abnormal burning or detonation of the fuel inside the engine leads to the effect known as engine knock. During detonation large amounts of heat is released inside the engine which excessively increases the temperature and pressure inside the engine, drastically reducing its thermal efficiency. The fuel should have the tendency to avoid creating the situation of detonation; this quality of the fuel is the antiknock property of the fuel. • The antiknock property of the fuel depends greatly on the self-ignition properties of the fuel, the fuel's chemical composition, and its chemical structure. The fuel most suitable for the SI engines is the one that has highest antiknock property, enabling the engine to work with high compression ratios of fuel, which in turn leads to higher fuel efficiency and higher power production.

24. Qualities of SI engine fuels • Gum deposits formed from the fuel: When gasoline is stored for longer periods of time, it has the tendency to oxidize and form gummy, solid substances. When used with an engine, such gasoline will cause sticky valves and piston rings, carbon deposits in the engine, gum deposits in the manifold, clogging of carburetor jets, and enlarging of cylinders and pistons. The gasoline used in the engine should have a tendency to form lower gum content and have a lower tendency to form gum during storage. • Low sulfur content: Hydrocarbon fuels may contain sulfur in various forms like hydrogen sulfide and other compounds. Sulfur is corrosive in nature and it can cause fuel line corrosion, carburetor parts, injection pumps, etc. Sulfur also promotes knocking of engine; hence its content in the gasoline fuel should be kept to a minimum.

25. Qualities of CI engine fuels • The fuel used in a compression ignition (CI) engine is diesel. Some of the desired characteristics of CI fuels are: • Knocking characteristics: In case of the CI engine the burning of fuel occurs due to compression of air. It is desired that as soon as the fuel is injected into the cylinder, it starts burning, but in practical situations this never happens as there is always a time lag between the injection of the fuel and burning of the fuel. As the duration of ignition lag increases, more and more amounts of fuel get accumulated in the cylinder head. When the fuel is finally burnt, excessively large amounts of energy is released, which produces extremely high pressure inside the engine. This causes the knocking sound inside the engine, which can be clearly heard. Thus the engines should have a short ignition lag so that the energy is produced uniformly inside the engine and there is no abnormal sound. The ignition of the fuel also affects starting, warming, and production of exhaust gases in the engine.

26. Qualities of CI engine fuels • The knocking capacity of the fuel is measured in terms of cetane rating of the fuel. The fuel you are using for your CI engine should have a cetane number high enough to avoid knocking of engine. • Volatility of the fuel: Thorough mixing of the fuel and air when fuel is injected in the cylinder head ensures uniform burning of the fuel. The fuel should be volatile in nature within the operating temperature range of the cylinder head so that it gets converted into a gaseous state and mixes thoroughly with compressed air. • Starting characteristics of the fuel: The smooth starting of the vehicle depends greatly on the fuel used for the vehicle. For easy starting of the vehicle it is important that the fuel has good volatility so that it mixes with the air uniformly and it readily forms into the combustible mixture. The high cetane number of the fuel ensures that the ignition of the fuel will be fast, which in turn will lead to faster starting of the vehicle.

27. Qualities of CI engine fuels • Smoke produced by the fuel and its odor: The exhaust gases produced from the fuel should not have too much smoke and odor. • Viscosity of the fuel: The fuel should have a viscosity low enough so that it can easily flow through the fuel system and the strainer at the lowest working temperatures. • Corrosion and wear: The fuel used for the CI engine should not cause corrosion of any components of the engine before or after combustion. • Easy to handle: Large quantities of fuel for a CI engine have to be transported from one place to the other, hence it should be easy to handle and transport. The fuel should have a high flash point and high fire point to avoid it catching fire during transport.

28. Rating of engine fuels • Normally fuels are rated for their antiknock qualities. • The rating of fuels is done by defining two parameters called Octane number (for Gasoline) and Cetane number (for Diesel).

29. Rating of SI engine fuels (Gasoline) • Resistance to knocking is an extremely important characteristics of fuel for SI engines. These fuels differ widely in their ability to resist knock depending on their chemical composition. • In addition to the chemical characteristics of hydrocarbons in the fuel, other operating parameters such as fuel air ratio, ignition timing, dilution, engine speed, shape of combustion chamber, ambient conditions, compression ratio etc. affect the tendency to knock in engine cylinder (hence these parameters to be fixed at standard in order to determine knock resistance characteristics of fuel). • Octane rating reflects the quality, purity, refinement, efficiency and heat bearing capacity of petrol.

30. Octane Rating • According to a standard practice, the antiknock value of an SI engine fuel is determined by comparing its antiknock property with a mixture of two reference fuels, iso-octane (C8H18) & normal heptane (C7H16). • Iso-octane being a very good antiknock fuel, is arbitrarily assigned a rating of 100 octane number & normal heptane has very poor antiknock qualities and is given a rating of 0 octane number. • The octane number fuel is defined as the percentage , by volume of iso-octane in a mixture of iso-octane and normal heptane, which exactly matches the knocking intensity of the fuel in a standard engine under s set of standard operating conditions. • In the year 2000 we were using leaded fuel which had 0.15 gms of lead per litre. Lead (added as tetraethyl lead) gives petrol greater antiknock quality (above 100 octane number), but the presence of lead in petrol meant more emission of CO (carbon monoxide) which is the reason why the government introduced compulsory use of unleaded petrol in 2000.

32. Rating of CI engine fuels (Diesel) – Cetane rating • In CI engines, the knock resistance depends on the chemical characteristics as well as on the operating and design conditions of the engine. • Therefore, the knock rating of a diesel fuel is found by comparing the fuel under prescribed conditions of operation in a special engine with primary reference fuels. • The reference fuels are normal cetane, C16H34 which is arbitrarily assigned a cetane number of 100 and aplha methyl naphthalene, C11H10, with an assigned cetane number of 0. • Cetane number of a fuel is defined as the percentage by volume of normal cetane in a mixture of normal cetane and alpha-methyl naphthalene which has the same ignition characteristics (ignition delay) as the test fuel when combustion is carried out in a standard engine under specified operating conditions. • Knock resistance property of diesel oil can be improved by adding small quantities of compounds like amyl nitrate, ethyl nitrate or ether.

33. Alternate Fuels - Propane • The entire surface transport of India is based on petroleum fuel, but it’s availability is of growing concern. The production of domestic crude has been declining and the transport system has been increasingly dependent on imported crude oil to meet its needs. There is a growing concern that the world may run out of petroleum based fuel resources. All these make it imperative that the search for alternative fuels is taken in right earnest. • The alternative fuels aspiring to take the place of petroleum are: • Propane • Liquified petroleum gas (LPG) consists mainly of propane, propylene, butane, and butylene in various mixtures. It is produced as a by-product of natural gas processing and petroleum refining. With propane’s simple molecular composition, propane - fueled vehicles emit significantly lower levels of carbon monoxide, hydrocarbons and nitrogen oxides than gasoline - fueled vehicles. The level of air - toxic emissions from propane -fueled vehicles is also low. According to the National Propane Gas Association, U.S.A., spark plugs from a propane vehicle last from 80,000 to 100,000 miles and propane engines can last two to three times longer than gasoline or diesel engines.

34. Alternate Fuels – Alcohol & Hydrogen • Alcohol fuels • Methanol and Ethanol fuel are typically a primary sources of energy; they are convenient fuels for storing and transporting energy. • These alcohols can be used in "internal combustion engines as alternative fuels", with butanol also having known advantages, such as being the only alcohol-based motor fuel that can be transported readily by existing petroleum-product pipeline networks, instead of only by tanker trucks and railroad cars. • Hydrogen • Hydrogen fuel is an eco-friendly fuel which uses electrochemical cells, or combustion in internal engines, to power vehicles and electric devices. It is also used in the propulsion of spacecraft and can potentially be mass produced and commercialized for passenger vehicles and aircraft. • Hydrogen fuel can provide motive power for cars, boats and airplanes, portable fuel cell applications or stationary fuel cell applications, which can power an electric motor. Hydrogen fuel in automotive vehicles is at least as safe as gasoline

35. Alternate Fuels - Biodiesel • Biodiesel • Biodiesel is made from animal fats or vegetable oils, renewable resources that come from plants such as, soybean, sunflowers, corn, olive, peanut, palm, coconut, safflower, canola, sesame, cottonseed, etc. • Once these fats or oils are filtered from their hydrocarbons and then combined with alcohol like methanol, biodiesel is brought to life from this chemical reaction. • These raw materials can either be mixed with pure diesel to make various proportions, or used alone. • Despite one’s mixture preference, biodiesel will release a smaller number of its pollutants (carbon monoxide particulates and hydrocarbons) than conventional diesel, because biodiesel burns both cleaner and more efficiently. Even with regular diesel’s reduced quantity of sulfur from the ULSD (ultra-low sulfur diesel) invention, biodiesel exceeds those levels because it is sulfur-free.

36. Alternate Fuels - LPG • LPG • Liquefied petroleum gas comes from petroleum refining, and the rest from natural gas processing. • It consists of hydrocarbons that are vapors, rather than liquids, at normal temperatures and pressures, but which turn liquid at moderate pressures; In order to liquefy the fuel, it is stored in sturdy tanks at about 20 times atmospheric pressure. • Its main constituent is propane, and it is sometimes referred to by that name. • Advantages • It's widely available & is cheaper than gasoline (when compared with the price of a gallon of gasoline with the price of the volume of LPG needed to drive the same distance). • Because LPG enters the engine as a vapor, it doesn't wash oil off cylinder walls or dilute the oil when the engine is cold, and it also doesn't put carbon particles and sulfuric acid into the oil. Thus an engine that runs on it can expect a longer service life and reduced maintenance costs. • Its high octane rating (around 105) means that power output and/or fuel efficiency can be increased, without causing detonation ("knocking").

37. Alternate Fuels - LPG • LPG Disadvantages • Because its source is partly petroleum, it does less to help relieve the petroleum dependency problem than some other alternative fuels. • Its somewhat lower energy content compared to gasoline means you need a slightly bigger tank to get the same driving range; • The tank will also be heavier because it has to be strong enough to withstand the LPG storage pressure. • Mostly because of the special fuel tank, a vehicle that runs on LPG will typically be somewhat more expensive than an equivalent gasoline-powered vehicle. • The refueling procedure on an older-style tank involves the release of some raw fuel vapors (unburned hydrocarbons) into the air.

38. Alternate Fuels - CNG • CNG • Liquefied natural gas for vehicles comes from the same sources as compressed natural gas (CNG). • Advantages • Compressed natural gas is like liquefied petroleum gas (LPG) in many ways. • CNG is the least expensive alternative fuel (except electricity) when you compare equal amounts of fuel energy. • The high octane rating of natural gas allows the CNG-powered vehicles to use a very high compression ratio and produce more power than stock gasoline versions. • Since the fuel tanks have to withstand such enormous internal pressures, they are incredibly tough, with good results for safety. • Natural gas is lighter than air and has very narrow flammability limits, if a leak develops the fuel will dissipate harmlessly into the air without causing a danger of ignition or explosion. • It is a clean fuel.

39. Alternate Fuels - CNG • CNG Disadvantages • The tanks are quite bulky and heavy, about three times more so than LPG tanks. • Because of the heavy-duty tanks, there is currently a large price premium for a CNG vehicle compared to a gasoline version.

40. Alternate Fuels - LNG • LNG • Liquefied natural gas for vehicles comes from the same sources as compressed natural gas (CNG). • Unlike liquefied petroleum gas (LPG), which is changed from a vapor to a liquid at room temperature by application of pressure, LNG has to be cooled to very low temperatures in order to cause it to liquefy; this makes it hard (though not impossible) to transport via tanker, and it is usually liquefied at the dispensing station. • Advantages • LNG has all the emissions advantages as CNG. • The liquefaction process amounts to a distillation, so the fuel is essentially pure methane which prevents variations in fuel quality. • LNG is a somewhat less bulky and heavy way to store natural gas than as CNG in high-pressure tanks.

41. Alternate Fuels - LNG • LNG Disadvantages • Though LNG tanks are less bulky and heavy than CNG tanks, they are still bigger than tanks for liquid fuels like gasoline, diesel, or alcohols. • They are also more complex and expensive because they have to insulate the fuel very well in order to prevent it from warming up and boiling off too fast. • Even with modern, rocket-science insulation materials and techniques, a LNG tank will begin venting fuel if left to sit for several days, so the fuel is best used in high-duty-cycle applications like delivery trucks.

42. Dopes & Additives for fuels • Dopes for SI engine fuels • Gasoline additives or dopes increase gasoline's octane rating or act as corrosion inhibitors or lubricants, thus allowing the use of higher compression ratios for greater efficiency and power. • Types of additives include oxygenates, antioxidants, corrosion inhibitors, metal deactivators, antiknock agents, lead scavengers & fuel dyes. • Oxygenates • Oxygenates are usually employed as gasoline additives to reduce carbon monoxide that is created during the burning of the fuel. • The oxygenates commonly used are either alcohols or ethers: • Alcohols: • Methanol (MeOH) Ethanol (EtOH) n-butanol (BuOH) • Isopropyl alcohol (IPA) Gasoline grade t-butanol (GTBA) • Ethers: • Methyl tert-butyl ether (MTBE) Tertiary amyl methyl ether (TAME) • Tertiary hexyl methyl ether (THEME) Ethyl tertiary butyl ether (ETBE) • Tertiary amyl ethyl ether (TAEE) Diisopropyl ether (DIPE)

43. Dopes for SI engine fuels contd… • Antioxidants • An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. It prevents the formation of gums that interfere with the operation of internal combustion engines. • The antioxidants commonly used are: • Butylatedhydroxytoluene (BHT) 2,4-Dimethyl-6-tert-butylphenol Ethylene diamine • 2,6-Di-tert-butylphenol (2,6-DTBP) p-Phenylenediamine • Corrosion inhibitor • A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy. • For fuels, various corrosion inhibitors can be used. Some components include zinc dithiophosphates. • DCI-4A, widely used in commercial and military jet fuels, acts also as a lubricity additive. Can be also used for gasolines and other distillate fuels. • DCI-6A, for motor gasoline and distillate fuels. • DCI-11, for alcohols and gasolines containing oxygenates. • DCI-28, for very low-pH alcohols and gasolines containing oxygenates. • DCI-30, for gasoline and distillate fuels, excellent for pipeline transfers and storage, caustic-resistant. • DMA-4 (solution of alkylaminophosphate in kerosene), for petroleum distillates.

44. Dopes for SI engine fuels contd… • Metal deactivators • Metal deactivators, or metal deactivating agents (MDA) are fuel additives and oil additives used to stabilize fluids by deactivating metal ions. • An example of a metal deactivator used for gasoline and jet fuels is N,N'-disalicylidene-1,2-propanediamine. • Antiknock Agents • Tetra-ethyl lead Methylcyclopentadienyl manganese tricarbonyl (MMT) • Ferrocene Iron pentacarbonyl Toluene Isooctane Triptane • Lead scavengers (for leaded gasoline) • A scavenger is a chemical substance added to a mixture in order to remove or inactivate impurities or unwanted reaction products. • Tricresyl phosphate (TCP) • 1,2-Dibromoethane • 1,2-Dichloroethane • Fuel dyes • Fuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear" or "white". • Solvent Red 24 Solvent Red 26 Solvent Yellow 124 Solvent Blue 35