Copyright 2009 Delmar, Cengage Learning Introduction Diesel
engines will burn just about any fuel introduced into the engine
cylinders To maximize engine performance & service life, only
fuels meeting the highest standards are used Diesel fuel is a
petroleum based product What is described as diesel fuel today will
likely change a decade from now Although in North America, diesel
power is primarily confined to the commercial sector, 50% of the
automobiles in Europe use diesel power There is some increase in
the use of biodiesel but this is mainly confined to low percentages
cuts into petroleum based diesel fuel
Slide 4
Copyright 2009 Delmar, Cengage Learning Fuel Terminology AFR
air-to-fuel ratio, actual ratio of air to fuel in a combustion
reaction Ash suspended solids or soluble metallic compounds in
diesel fuels ASTM American Society for Testing & Materials
Organization, classifies fuels to a standard ASTM #1D Fuel
recommended for engines required to operate under variable loads
& speeds ASTM #2D Fuel recommended for engines required to
operate under constant loads & speeds
Slide 5
Copyright 2009 Delmar, Cengage Learning Fuel Terminology Boil
Point temperature at which a liquid vaporizes Calorific Value
potential heat energy measured in British Thermal Units (BTUs)
Catalyst a substance that enables a chemical reaction without
itself undergoing any change Cetane Number (CN) a measure of the
ignition quality of a diesel fuel Cloud Point temperature at which
normal paraffins in fuel become less soluble & begin to
precipitate as wax crystals
Slide 6
Copyright 2009 Delmar, Cengage Learning Fuel Terminology Crude
Oil raw petroleum Diesel Fuel term to describe distillate petroleum
compounds formulated for use in on-highway compression ignition
(CI) engines Distillate alternate name for diesel fuel Fire Point
temperature at which a liquid HC fuel evaporates sufficient
flammable vapor to burn continuously in air Flame Front forward
boundary of the reacting zone in-cylinder combustion
Slide 7
Copyright 2009 Delmar, Cengage Learning Fuel Terminology Flame
Propagation the way in which a fuel combusts inside the engine
cylinder as determined by the manner the flame front spreads Flash
Point temperature at which a liquid HC fuel evaporates sufficient
flammable vapor to momentarily ignite when a flame is brought to
the surface Fractions portion of a mixture separated by
distillation or a cracking procedure
Slide 8
Copyright 2009 Delmar, Cengage Learning Fuel Terminology
Fuel-Air Ratio used to describe ratio of fuel to air in diesel
combustion Gasoline group of liquid petroleum fuels for use in
spark ignited (SI) engines Kerosene widely used as heating oil
& jet fuel Microorganism Growth airborne bacteria & fungi
entering vehicle & storage tanks through venting systems
Slide 9
Copyright 2009 Delmar, Cengage Learning Fuel Terminology
Natural Gas (also liquefied natural gas: LPG & compressed
natural gas: CNG) gaseous product of petroleum either suspended
above liquid crude oil or dissolved in it Octane Rating measure of
the antiknock quality of a fuel (usually gasoline) Oxidation
Stability products of oxidizing stored diesel fuel can result in
deposits, filter plugging & lacquering of fuel injection
equipment
Slide 10
Copyright 2009 Delmar, Cengage Learning Fuel Terminology
Photochemical Smog reaction of HCs & NOxs with sunlight in the
lower atmosphere Pour Point lowest temperature in which fuel can be
pumped Specific Gravity the weight of volume of a liquid compared
to the weight of the same volume of water Stoichiometric Ratio the
exact ratio of reactants required for a chemical reaction to take
place
Slide 11
Copyright 2009 Delmar, Cengage Learning Fuel Terminology Sulfur
Content maximum sulfur amount in fuel as recommended by American
Petroleum Institute (API) & Environmental Protection Agency
(EPA) Viscosity measure of a liquids resistance to shear, a value
that generally decreases as temperature increases Volatility the
tendency of a liquid to vaporize
Slide 12
Copyright 2009 Delmar, Cengage Learning Petroleum HHC fossil
fuels are found in the upper strata of the earths crust 770% of
energy consumed in North America & 40% worldwide is derived
from petroleum products AAn unrenewable energy source with limited
reserves
Slide 13
Copyright 2009 Delmar, Cengage Learning Crude Oil Three types:
Asphalt-based Paraffin-based Mixed-base Crude petroleum must be
refined to separate the fractions used to formulate fuels
identified as diesel fuel, gasoline, kerosene & heavy furnace
oil
Slide 14
Copyright 2009 Delmar, Cengage Learning Refining Petroleum
Crude Oil Fractions separated Fractions graded & extracted by
cut points Gas taken off the top is natural gas In descending order
of boil: Gasoline Naptha Kerosene Light gas oil Heavy gas oil
Liquid remaining at bottom known as residuum
Slide 15
Copyright 2009 Delmar, Cengage Learning Thermal & Catalytic
Cracking Cracking is a process by which heavier fuel oils may be
chemically modified by dividing heavy molecules into smaller light
molecules Thermal cracking subjects crude to high temperatures
& pressures in a cylindrical tower Catalytic cracking is a more
efficient method of accomplishing same objective Crudes from
various regions naturally yield various percentages of products
from refining. Today, this natural extraction may not represent
market demand. Cracking allows the crude to be refined more in
accordance with the products required for the market
Slide 16
Copyright 2009 Delmar, Cengage Learning Thermal & Catalytic
Cracking Hydrocracking is a catalytic cracking process undertaken
in the presence of hydrogen, used to produce higher volatility,
lighter fractions required in fuels
Slide 17
Copyright 2009 Delmar, Cengage Learning Diesel Fuel
Characteristics Cetane Number (CN) measure of the ignition quality
Increasing CN reduces fuel density & therefore fuel mileage As
CN increases, ignition temperature decreases Ignition Accelerators
fuel additives that increase the CN value Cyclohexanol nitrate will
raise CN by 7 points Ignition accelerators do not improve fuel;
they merely lower ignition temperature & thereby reduce
ignition lag. They should only be used after analysis of fuel by
fuel supplier & then only as prescribed. Excessive quantities
of ignition accelerator in fuel have the effect of advancing
ignition timing which can cause engine damage.
Slide 18
Copyright 2009 Delmar, Cengage Learning Diesel Fuel
Characteristics Heating Value (Calorific Value) Heat energy
released during combustion Value used to reckon the thermal
efficiency of engines ability to produce power
Slide 19
Copyright 2009 Delmar, Cengage Learning Diesel Fuel
Characteristics API Gravity is a measure of how the weight of a
petroleum liquid compares with water Measured with a hydrometer
Understanding API gravity helps troubleshoot persistent low-power
& marginal emissions test failures
Slide 20
Copyright 2009 Delmar, Cengage Learning Diesel Fuel
Characteristics Ultra-Low Sulfur Fuels Sulfur dioxide produced from
combustion of diesel fuel is recognized as environmentally
hazardous Sulfur content of diesel fuels progressively legislated
to lower levels Off-Highway Fuels Bunker fuels cut with glycol
& other antigel compounds similar to jet fuel
Slide 21
Copyright 2009 Delmar, Cengage Learning Fuel Storage,
Deterioration & Performance Fuel chemistry is adjusted
seasonally by the refiner/supplier due to temperature variables
Storage tanks may contain water, drain the water periodically,
helping to prevent water buildup Water in fuel presents two main
problems: If it collects in crossover pipe, becomes vulnerable to
freeze-up It promotes microorganism growth. Metabolic waste is
acidic & has a corrosive effect on fuel system components. More
common in systems that run only a couple of times a year Add methyl
hydrate (alcohol) to the tank to prevent freeze-up. Water &
alcohol form a solution that can be absorbed by the fuel &
pumped through the fuel system Its good practice to keep fuel tanks
full. This keeps moisture- laden air out of the tanks ad reduces
water-in-fuel problems A bulk fuel filtration set up
Slide 22
Copyright 2009 Delmar, Cengage Learning Fuel Storage,
Deterioration & Performance Climate Influence When fuel is
stored & exposed to high temperatures, its more volatile
fractions are boiled off, lowering the CN Fuel heaters sometimes
used to help compensate for deficiencies in cloud point, pour point
& viscosity ratings in colder climates
Slide 23
Copyright 2009 Delmar, Cengage Learning Fuel Conditioners Most
OEMs disapprove of their use Vague mixture of cetane improvers,
cleansing additives & pour point depressants in an alcohol base
Generally create more problems than they solve, however there are
occasions when they have to be used Use only when no other option
available Always follow manufacturers recommendations
Slide 24
Copyright 2009 Delmar, Cengage Learning Fuel Conditioners Fuel
conditioners are not normally recommended by OEMs If required to
use them, the technician should understand their functionality
Always follow OEM & manufacturers recommendations when using
aftermarket products!
Slide 25
Copyright 2009 Delmar, Cengage Learning Costs of Operating a
Truck Fuel represents major expense in operating a truck The diesel
fuel of the future?