Chapter 27 - Fuels

Question 1

What is the stoichiometric ratio of gasoline?

Answer 1

14.7:1 air to fuel ratio

Question 2

Air/fuel ratio for best fuel economy?

Answer 2

15-16:1

Question 3

Volume of air and fuel required to make the stoichiometric ratio? (in litres)

Answer 3

10,000 litres of air mixed with 1 litre of gasoline

Question 4

What ratios are considered “rich” air/fuel ratios?

Answer 4

Anything below 14.7:1

Question 5

What is crude oil and what does it consist of?

Answer 5

Unprocessed/unrefined oil; 84% carbon, 14% hydrogen, 3% sulfur (in the form of sulfides), <1% nitrogen, oxygen, metals, and salts

Question 6

What are “sweet” and “sour” oils?

Answer 6

Refers to sulfur content - sour oils have high sulfur, sweet have low

Question 7

What are hydrocarbons?

Answer 7

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

Question 8

What does refining crude oil do? How much crude oil has to be processed to make gasoline? Diesel?

Answer 8

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

Question 9

Describe “fractional distillation”

Answer 9

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.

Question 10

What are the boiling points of: propane, gasoline, diesel, jet fuel, lubricating oil, and asphalt?

Answer 10

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)

Question 11

What is “cracking”?

Answer 11

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

Question 12

What percentage of human-caused CO2 emissions does transportation contribute?

Answer 12

About 25%

Question 13

What is the chemical symbol for gasoline?

Answer 13

C8H15 (8 carbon atoms, 15 hydrogen)

Question 14

What is an octane rating?

Answer 14

A fuel’s resistance to detonation - the higher the number, the more resilient it is

Question 15

What are the two reference fuels used in labs when testing octane ratings?

Answer 15

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.

Question 16

How is the Antiknock Index measured?

Answer 16

Average of MON (motor octane number) and RON (research octane number) ratings [(M + R) / 2)]

Question 17

What is volatility?

Answer 17

How readily a liquid evaporates

Question 18

In regards to vapour lock, how do summer and winter gasolines differ?

Answer 18

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

Question 19

How does altitude affect gasoline?

Answer 19

Gas is formulated for the elevation where it will be sold. Higher altitudes = less atmospheric pressure = evaporates easier

Question 20

How does fuel vaporization affect oil performance (within crankcase)?

Answer 20

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

Question 21

What is the most common method for measuring fuel vaporization?

Answer 21

RVP (Reid vapour pressure) test

Question 22

How does sulfur in fuel affect an engine?

Answer 22

Too much sulfur can create H2SO4 (sulfuric acid) within the engine, therefore sulfur is limited to LESS THAN 0.01% of fuel content

Question 23

What is normally added to gasoline to achieve the desired octane rating?

Answer 23

Methylcyclopentadienyl manganese tricarbonyl (MMT)

Question 24

How much lead is allowed to be in modern gasoline?

Answer 24

0.016 grams per litre / 0.06 grams per gallon

Question 25

What is used as a de-icer in in gasoline?

Answer 25

Isopropyl Alcohol

Question 26

Name some additives to fuel to prevent rust, gum, and to clean the fuel

Answer 26

Metal deactivators/rust inhibitors, gum/oxidation inhibitors, detergents

Question 27

What do added oxygenates do to fuel and what is the resulting mixture called?

Answer 27

Contains oxygen and leans the air/fuel mixture -> increase octane, lower CO (carbon MONoxide emissions). Fuel mixed with oxygenates is called Reformulated Gasoline (RFG)

Question 28

What is the most commonly added oxygenate to fuel, and how does it affect performance/emissions?

Answer 28

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

Question 29

What brand name fuel can help prevent gummy buildup from fuel additives in Direct Injection engines?

Answer 29

Top Tier Detergent Gasoline

Question 30

Why must the alcohol content of gasoline be tested?

Answer 30

Too much alcohol (>10%) can cause drivability problems such as fuel filter plugging, fuel system corrosion, deterioration of rubber, too lean air/fuel mixture

Question 31

What is the environmental appeal of biomass fuels (such as ethanol or biodiesel)?

Answer 31

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

Question 32

Give the technical definition of "energy density" in regards to fuels

Answer 32

Amount of energy provided by a standard weight of that fuel. Rated in joules per kilogram. 1 joule = 1 watt per 1 second

Question 33

What is the octane rating of ethanol and how is ethanol normally obtained?

Answer 33

115, made from fermented and distilled corn. Burns cleaner than gasoline

Question 34

What are the main benefits of running E85 (85% ethanol blended fuel)?

Answer 34

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

Question 35

Describe methanol

Answer 35

Oxygenate that is clean burning but corrosive. Formed from natural gas or coal/biomass. M85/15 gasoline blend to aid cold starts

Question 36

Where and why is Propane/LPG (liquified petroleum gas) used?

Answer 36

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

Question 37

How is natural gas used in vehicles and what are its benefits?

Answer 37

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

Question 38

What are P-Series fuels?

Answer 38

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.