Internal Combustion Engines Faculty - Er. Ashis Saxena

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

Unit - 1 Chapter – 1(b) 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.

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

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

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.

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.

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.

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.

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).

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.  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.

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.

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

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.

Natural Gas: Constituents

CNG vs Automotive fuels

Composition of typical crude oil

Refining of crude oil ProductBoiling Range, o C Liquefied Petroleum Gas40 to 0 Motor Gasoline Kerosene, jet fuel (ATF) Diesel Fuel Furnace Oil Lube Oils Residual Fuel Asphalt540+ Petroleum CokeSolid

Refining of crude oil

Qualities of SI engine fuels

Qualities of CI engine fuels

Rating of engine fuels

Rating of SI engine fuels (Gasoline)

Octane Rating

Rating of CI engine fuels (Diesel) – Cetane rating

Alternate Fuels - Propane

Alternate Fuels – Alcohol & Hydrogen

Alternate Fuels - Biodiesel

Alternate Fuels - LPG

Alternate Fuels - CNG

Alternate Fuels - LNG

Dopes & Additives for fuels

Dopes for SI engine fuels contd…