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Michigan State UniversityCollege of Engineering
Fall 2007 – ME 444
Andrew BuczynskyFuels and Lubricants Department
General Motors Powertrain
Fuels for Road VehiclesBasics of Gasoline, Diesel Fuel, E85,
and Biodiesel
A. Buczynsky, GM
Petroleum
Source of fuels– Petroleum-based fuels come from crude oil– Crude oil varies depending where in the world it
comes from
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Map: API, Understanding Today’s Energy Needs. Crude oil import data: EIA
Three-quarters of U.S. crude oil imports come from 5 locations: Persian Gulf (21%), Canada (17%), Mexico (16%), Venezuela (11%), Nigeria (10%).
Flow of Crude Oil
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Crude Oil Refining
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Regional Consumption by Fuel Type
46.5
22.328.4
30.2
47.5 36.2
3.311.4
14.8
20.0 18.8 20.5
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
US EU 25 Asia Pacific
Co
nsu
mp
tio
n d
em
an
d
Other
Hvy dist
Mid dist
Lt dist
Source: BP Statistical Review of World Energy June 2007Lt dist = Aviation and motor gasoline. Mid dist = jet fuel, kerosene, and diesel fuel.Hvy dist = Marine bunker fuel and crude oil used as fuel. Other = refinery gas, LPG, coke,lubricants, solvents, bitumen, wax.
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Flow From Refinery to Pump
Pipeline, bargerailcar, truck
Supply terminal Retail station
Truck
EthanolBiodiesel
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Fuel Lingo
Gasoline– Conventional gasoline– Reformulated gasoline (RFG)– California gasoline (CARB Phase 3 RFG)– Boutique fuels
Low vapor pressure gasoline (low RVP) Clean burning gasoline (CBG)
Diesel fuel– Ultra low sulfur diesel fuel (ULSD)– Low sulfur diesel fuel (LSD)– High sulfur diesel fuel (HSD)
On-road
Off- road
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States Have Developed “Boutique” Fuel Recipes to Avoid RFG
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U.S. Pipeline Distribution SystemGasoline, diesel fuel and jet fuel move in the same pipelines
Fuels are fungible (interchangeable) products
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Pipeline Primer
Different product batches are “pushed” through the system abutting each other. The mixing zones between batches are called interfaces.
RFG reg. ULSD Jet fuel HSD Conv. ULR
RFG prem.
RFG reg.
Product flow
Interfaces
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Gasoline
Defined by ASTM D 4814
– “a volatile mixture of liquid hydrocarbons, generally containing small amounts of additives, suitable for use as a fuel in spark-ignition, internal combustion engines.”
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Volatility
The tendency of a fuel to vaporize– Measured by
Vapor pressure Distillation Vapor-liquid ratio
Gasoline volatility is adjusted seasonally– Winter: cold start– Summer: hot restart, evaporative emissions
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Driveability
Volatility affects driveability– Driveability: the ability of a vehicle to operate
satisfactorily under normal driving conditions:Ease of startingSmooth idleSmooth acceleration and cruise
– Driveability is quantified by trained raters using a set driving protocol
Lower demerits mean better driveability
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Antiknock Quality
Ability of a gasoline to resist knocking– Knock – engine noise produced by rapid pressure
rise as a result of abnormal combustion Expressed as octane number
– Two laboratory test methods measure octane number
Both use single cylinder, variable compression engines
Each uses different operation conditions
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Octane Number
RON (R): Research Octane Number
MON (M): Motor Octane Number
Antiknock Index: (R+M)/2 87MINIMUM OCTANE RATING
(R+M)/2 METHOD
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Octane Grades
Current offerings– Regular 87 (R+M)/2: sufficient for >90+% of vehicles– Midgrade 89 (R+M)/2: for vehicles with a higher
octane requirement– Premium 91 (R+M)/2: for performance vehicles
Regular versus premium– Octane higher than required to prevent audible
knock or knock sensor activity is a waste of money
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Oxygenates
Oxygenates are fuel molecules that contain oxygen– Ethanol (EtOH) is the only oxygenate now used in
gasoline Limited to 10 volume % in gasoline About 50% of U.S. gasoline contains 10% ethanol
– Ethers were formerly used but have been banned by many states
– Biodiesel is used in diesel fuel Renewable Fuels Standard (RFS)
– Requires a certain volume of renewable fuel be used– By about 2010-2015, all U.S. gasoline will contain
10% ethanol
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Effect of Ethanol on Distillation of Gasoline
100
150
200
250
300
350
400
0 10 20 30 40 50 60 70 80 90 100
Percent evaporated
Deg
rees
, F
E0 E10
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Oxygenate Use in Vehicles
10% ethanol blends– Compatible with all vehicles
Flex-fuel vehicles– Can run on up to 85% ethanol– Check your owners’ manual to know if you have a FFV– Do not use more than 10% ethanol in a standard vehicle
Never put methanol into your vehicle– That includes de-icers in the winter – That includes FFVs
Solvent chemicals touted to improve fuel economy– Can be aggressive toward elastomers plastics
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Engine Deposits
Negatively affect vehicle performance– Fuel injector fouling– Intake valve deposits– Combustion chamber deposits
All gasoline must contain deposit control additive
EPA requirement Provides minimum performance
TOP TIER Detergent Gasoline
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Comparison of TOP TIER and EPA Additive Concentrations
Base Fuel + EPA detergent concentration
Base fuel + TOP TIER detergent concentration
After 100-hrs in Ford 2.3 L engine
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Diesel Fuel
A liquid hydrocarbon mixture, for use in compression-ignition engines– ASTM D 975– Types of compression-ignition fuels
Diesel fuel – grade 2-D Kerosene – grade 1-D
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Distillation Comparison of Gasoline and Diesel Fuel
100150200250300350400450500550600650
0 10 20 30 40 50 60 70 80 90 100
Percent evaporated
Deg
rees
F
E0 Diesel
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Cold Flow Properties
Diesel fuel can gel at low temperatures– Diesel fuel contains wax molecules– Wax causes the fuel to become more viscous as
temperature drops– Wax also will precipitate from the fuel at low
temperatures and plug fuel filters– Remedy is to blend kerosene to improve cold
handling properties or use additives Kerosene results in a fuel economy debit Additives are expensive and their performance
depends on the base fuel
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Cetane Number
A measure of how readily a fuel auto-ignites– A high cetane number is desirable
Indicates short ignition delay after injection Makes starting easier, reduces white smoke and
engine noise– Cetane number of diesel fuel in the U.S. is poor
compared to the rest of the world ASTM 975 specifies a minimum of 40 Europe specifies a minimum of 51
– Cetane index is a calculated value used to approximate cetane number
Based on density and distillation temperatures
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Alternative Fuels
Any non-petroleum based fuel by legislative definition.
– Alternative fuels currently of primary interest Ethanol (E85) Biodiesel
– Others alternative fuels M85 M100 E100 LPG CNG
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E85 70-83 volume % denatured ethanol blended
with hydrocarbons– Controlling specification is ASTM D 5798
Based on early 1990s vintage vehicles Currently undergoing extensive review
– Ethanol content controlled by desired volatility Ethanol has a low vapor pressure Less ethanol in winter to ensure good start-up
– Stoichiometric air/fuel ratio is 10 compared to 14.7 for gasoline
– E85 has (R+M)/2 octane value of about 96-98– Lower heating value than gasoline (12,500 BTU/lb
vs. 18,500 BTU/lb)
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Benefits of E85
Reduces dependence on foreign oil Renewable fuel Reduces CO2 (greenhouse gas) emissions
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Carbon Dioxide in Perspective
600 gallons gasoline per year
Creates ~12,000 lbs CO2
Requires 240 trees to extract the CO2
Source: Automotive News
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Energy to Produce Ethanol vs. GasolineSource: Argonne National Laboratory
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-2%
-23%
-64%
-6%
-80%
-60%
-40%
-20%
0%
E10 E10 cell. E85 E85 cell.
Ethanol Blends Significantly Reduce GHG Emissions
Source: Argonne National Laboratory
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Disadvantage of E85
Only 1,252 E85 stations exist nationwide as of August 1, 2007 (some stations are for private fleet vehicles only)
– Compared to more than 150,000 for gasoline* 317 in Minnesota 151 in Illinois 49 in Michigan 5 in California
Price is still not competitive in many areas
Lower fuel economy Food versus fuel controversy
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Biodiesel
Oil or Fat SoybeanCornCanolaCottonseedSunflowerBeef tallowPork lardRecycled cooking oils
CatalystSodium hydroxidePotassium hydroxide
Fatty acid methyl ester
(FAME or biodiesel)
+
Glycerin(removed)
Made by a chemical process using vegetable or used cooking oils, animal fat, or grease as starting material. Oils or fats that have not undergone the chemical process are not biodiesel.
+ Alcohol Methanol
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Biodiesel
Biodiesel blends are designated B___– 5% biodiesel is B5– 20% biodiesel is B20– 100% biodiesel is B100
B100 in U.S. comes primarily from soy beans – Yellow grease is a secondary source
B100 in Europe comes primarily from rape seed– B5 is considered standard diesel fuel
Biodiesel blends are made at a supply terminal, not at a refinery
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Advantages of Biodiesel
Renewable energy source Reduces CO2 life-cycle emissions by 78%
compared to diesel fuel Improves cetane and lubricity of diesel fuel Improves most regulated emissions
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Disadvantages of Biodiesel
Can oxidize (become rancid)– Results in gums, deposits, and acids
Has poor cold temperature properties Entrains more water than diesel fuel May increase NOx emissions Heating value about ~10% lower compared to 2-D
– B20 users experience a 1-2% loss in fuel economy Requires tax incentives to be competitive
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Hydrogenated Biodiesel
Also called ‘renewable diesel’ or ‘green diesel’
Hydrogen is used to convert fats and oils to hydrocarbons
Advantage is a product more like standard diesel fuel
Disadvantages are high capital requirement and poor lubricity
CH3(CH2)16COO CH2
CH3(CH2)16COO CH
CH3(CH2)16COO CH2
3 n-C18 + 1 C3H8 + 6 H20
+ H2
Source: OMV Refining and Marketing