Chapter 27 - Fuels Flashcards
What is the stoichiometric ratio of gasoline?
14.7:1 air to fuel ratio
Air/fuel ratio for best fuel economy?
15-16:1
Volume of air and fuel required to make the stoichiometric ratio? (in litres)
10,000 litres of air mixed with 1 litre of gasoline
What ratios are considered “rich” air/fuel ratios?
Anything below 14.7:1
What is crude oil and what does it consist of?
Unprocessed/unrefined oil; 84% carbon, 14% hydrogen, 3% sulfur (in the form of sulfides), <1% nitrogen, oxygen, metals, and salts
What are “sweet” and “sour” oils?
Refers to sulfur content - sour oils have high sulfur, sweet have low
What are hydrocarbons?
HCs are chains of carbon and hydrogen. The number of carbon atoms determines the length of the chain. HCs are sources of energy so we use them as fuels
What does refining crude oil do? How much crude oil has to be processed to make gasoline? Diesel?
Separates hydrocarbons from crude oil so we can use it as fuel. 159L / 42 gal of crude oil is needed for 75.7L / 20 gal of gasoline or 26.5L / 7gal of diesel
Describe “fractional distillation”
Occurs at a refinery, method of separating different hydrocarbons based on their different boiling points. Boiled crude oil will vaporize and travel up a column, and the different HCs will cool and condense at different points. These “fractions” are then collected and treated of impurities.
What are the boiling points of: propane, gasoline, diesel, jet fuel, lubricating oil, and asphalt?
Propane - 40C / 104F
Gasoline - 40C - 205C (104-401F)
Diesel - 250C - 350C (482-662F)
Jet fuel - 175C - 325C (350-617F)
Lubricating oil - 300C - 370C (572-700F)
Asphalt - >600C (>1112F)
What is “cracking”?
The process of using high temps/pressures to break down an HC with a higher boiling point into an HC with a lower boiling point
What percentage of human-caused CO2 emissions does transportation contribute?
About 25%
What is the chemical symbol for gasoline?
C8H15 (8 carbon atoms, 15 hydrogen)
What is an octane rating?
A fuel’s resistance to detonation - the higher the number, the more resilient it is
What are the two reference fuels used in labs when testing octane ratings?
Isooctane and heptane - isooctane is extremely resilient to detonation and has a rating of 100. Heptane knocks easily and has a rating of zero. If a consumer-grade fuel knocks as much as a fuel with 85% isooctane and 15% heptane, that fuel will have an octane rating of 85.
How is the Antiknock Index measured?
Average of MON (motor octane number) and RON (research octane number) ratings [(M + R) / 2)]
What is volatility?
How readily a liquid evaporates
In regards to vapour lock, how do summer and winter gasolines differ?
Vapour lock is caused by gasoline vaporizing in the fuel delivery system. Instead of flowing thru the line, the vapour gets compressed by the pressured fuel and causes a blockage. Therefore summer gas is designed to vaporize less readily than winter gas. Summer gas usually has a RVP rating of 7.0 psi, and winter gas is 9.0 psi
How does altitude affect gasoline?
Gas is formulated for the elevation where it will be sold. Higher altitudes = less atmospheric pressure = evaporates easier
How does fuel vaporization affect oil performance (within crankcase)?
Fuel needs to vaporize within the crankcase because it might otherwise mix with and dilute the oil, leading to performance problems like sludge and poor lubrication
What is the most common method for measuring fuel vaporization?
RVP (Reid vapour pressure) test
How does sulfur in fuel affect an engine?
Too much sulfur can create H2SO4 (sulfuric acid) within the engine, therefore sulfur is limited to LESS THAN 0.01% of fuel content
What is normally added to gasoline to achieve the desired octane rating?
Methylcyclopentadienyl manganese tricarbonyl (MMT)
How much lead is allowed to be in modern gasoline?
0.016 grams per litre / 0.06 grams per gallon
What is used as a de-icer in in gasoline?
Isopropyl Alcohol
Name some additives to fuel to prevent rust, gum, and to clean the fuel
Metal deactivators/rust inhibitors, gum/oxidation inhibitors, detergents
What do added oxygenates do to fuel and what is the resulting mixture called?
Contains oxygen and leans the air/fuel mixture -> increase octane, lower CO (carbon MONoxide emissions). Fuel mixed with oxygenates is called Reformulated Gasoline (RFG)
What is the most commonly added oxygenate to fuel, and how does it affect performance/emissions?
Ethanol (grain-based alcohol). 10% added to gas adds 2.5 - 3 octane points to gas. Reduces air toxics by 50%, reduces CO emissions due to higher oxygen content, loosens contaminants, absorbs water in fuel system which reduces freezing in cold
What brand name fuel can help prevent gummy buildup from fuel additives in Direct Injection engines?
Top Tier Detergent Gasoline
Why must the alcohol content of gasoline be tested?
Too much alcohol (>10%) can cause drivability problems such as fuel filter plugging, fuel system corrosion, deterioration of rubber, too lean air/fuel mixture
What is the environmental appeal of biomass fuels (such as ethanol or biodiesel)?
When they burn, they remain carbon neutral. Meaning the amount of carbon absorbed from the atmosphere by the plants from which they derive, is the same as the carbon released when used for combustion
Give the technical definition of “energy density” in regards to fuels
Amount of energy provided by a standard weight of that fuel. Rated in joules per kilogram. 1 joule = 1 watt per 1 second
What is the octane rating of ethanol and how is ethanol normally obtained?
115, made from fermented and distilled corn. Burns cleaner than gasoline
What are the main benefits of running E85 (85% ethanol blended fuel)?
Reduces reliance on foreign oil, vehicles don’t need much modification to use it, fewer emissions than gas, CO2 emissions much lower, ethanol-blend fuel keeps fuel system clean of varnish/gummy deposits
Describe methanol
Oxygenate that is clean burning but corrosive. Formed from natural gas or coal/biomass. M85/15 gasoline blend to aid cold starts
Where and why is Propane/LPG (liquified petroleum gas) used?
In trucks, taxis, police cars, school buses. Emits less HC, CO2, and CO, and provides a similar driving range to gasoline than other alternative fuels, allows for easy cold starts, higher octane rating than gas
How is natural gas used in vehicles and what are its benefits?
CNG (compressed natural gas) or LNG (liquified natural gas). CNG - light/medium duty trucks, LNG - transit buses, locomotives, long-haul semi-trucks.
Results in 25 percent fewer CO2 emissions and is nontoxic. However, must be stored under pressure therefore it takes up space. LNG is liquid so takes up less space than CNG, gives longer range than CNG
What are P-Series fuels?
New alternative fuel type. A gallon of P-series fuel emits 50% less CO2, 35% fewer HCs, and 15% less CO than gasoline. Also has 40% less ozone-forming potential.
