Diesel fuel properties

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  • Most of you have seen this slide, which discloses the various technologies that are being applied to achieve Tier 2-4 emissions levels. I will only discuss the fuel system where the migration to common rail systems are a key leverage for achieving low emissions.
  • 1-D : A special-purpose, light middle distillate fuel for use in diesel engine applications with frequent and widely varying speeds and loads or when abnormally low operating temperatures are encountered. Higher volatility than that provided by No. 2-D fuels. 2-D A general-purpose, middle distillate fuel for use in diesel engines, especially in applications with relatively high loads and uniform speeds, or in diesel engines not requiring fuels having higher volatility or other properties specified in Grade No. 1-D fuels. 4-D A heavy distillate fuel, or a blend of distillate and residual oil, for low- and medium-speed diesel engines in applications involving predominantly constant speed and load.
  • This slide gives the molecular structure of the some fuels, in addition the number of carbons. The comparison of the parent fuel structure to the alternative fuels is very important, as you’ll see later on in the presentation. You will see that methane has one carbon, surrounded by hydrogens; propane has three carbons. You see methanol as the alcohol over to the right with one carbon, and ethanol, as an alcohol with two carbons. Below those are Iso Octane, which has 8 carbons in a branched structure, which will become important. This makes an ideal gasoline and Iso Octane has an octane number of 100. Then you see an standard diesel fuel, cetane, which is a long straight chain molecule with no branching and 20 carbons. Cetane has a cetane number of 100. You can see that gasoline is a much shorter, and more branched compound, whereas diesel fuel is much longer and more straight chain hydrocarbon. You can also see some examples of aromatics. These compounds are known carcinogens in diesel fuel but are not present in biodiesel. The aromatics all share a similar 6 carbon ring, known as benzene.
  • Low cetane number fuels are slow to ignite and then burn too rapidly, leading to high rates of pressure rise. These poor combustion characteristics can give rise to excessive engine noise and vibration, increased exhaust emissions and reduced vehicle performance, with increased engine stress specifically on the piston & cylinder
  • ASTM D 2274 is most commonly referenced
  • Diesel fuel properties

    1. 1. Understanding Today’s Diesel Fuel National Biodiesel Board Technician Outreach Program
    2. 2. Objectives <ul><li>Understand the new face of diesel fuels </li></ul><ul><li>What are today’s diesel fuel quality standards </li></ul><ul><li>How are these standards set? </li></ul><ul><li>How do these fuel standards affect the diesel engine operation? </li></ul><ul><li>- performance </li></ul><ul><li>- emissions </li></ul><ul><li>- fuel economy </li></ul>
    3. 3. Emissions Regulations in the driver’s seat <ul><li>The Clean Air Act of 1970 gave EPA broad authority to regulate motor vehicle pollution, and the Agency's emission control policies have become progressively more stringent since the early 1970's. </li></ul>
    4. 4. Diesel Emission Reductions
    5. 5. Fuel technology Combustion technology Aftertreatment technology Fuel system technology Better understanding of combustion Alternate Fuels (Biodiesel) Low sulfur De-NOx DOC PM trap Rate control High pressure Multi-injection EGR technology Others Control technology Technology Pathway
    6. 6. What is Diesel Fuel <ul><li>Various Petroleum Components: </li></ul><ul><li>Paraffins </li></ul><ul><li>Isoparaffins </li></ul><ul><li>Napthenes </li></ul><ul><li>Olefins </li></ul><ul><li>Aromatic Hydrocarbons </li></ul>
    7. 7. How is diesel made? <ul><li>Petroleum coke is heated up to separate the complex mixture of hydrocarbons into usable products like diesel. </li></ul><ul><li>Each petroleum derived product is distinguished by its boiling point. </li></ul><ul><li>Diesel fuel undergoes a hydro-treating process to remove sulfur. </li></ul>
    8. 9. Typical Refinery Products From: Schmidt, G.K. and Forster, E.J., “Modern Refining for Today’s Fuels and Lubricants,” SAE Paper 861176, 1986. Solid Petroleum Coke 1000 + 540 + Asphalt 650 - 1200 340 - 650 Residual Oil 650 - 1000 340 - 540 Lube Oils 350 - 650 180 - 340 #2 Diesel, Furnace Oil 340 - 515 170 - 270 Kerosene, Jet Fuel, #1 Diesel 80 - 400 30 - 200 Gasoline -40 - 31 -40 - 0 LPG Product Boiling Range Deg. F Boiling Range Deg. C
    9. 10. Grades of Diesel Fuel <ul><li>1-D ( S15) </li></ul><ul><li>1-D ( S500) </li></ul><ul><li>1-D (S5000) </li></ul><ul><li>2-D ( S15) </li></ul><ul><li>2-D ( S500) </li></ul><ul><li>2-D (S5000) </li></ul><ul><li>4-D </li></ul><ul><li>S15, S500, & S5000 relate to sulfur content </li></ul><ul><li>Off-road versus On-road use </li></ul><ul><li>Varied in density and viscosity </li></ul>
    10. 11. ASTM Specifications for Diesel Fuel -ASTM D 975
    11. 12. Diesel Fuel Specification ASTM D 975 <ul><li>Flashpoint </li></ul><ul><li>Water and Sediment </li></ul><ul><li>Distillation </li></ul><ul><li>Kinematic Viscosity </li></ul><ul><li>Ramsbottom Carbon Residue </li></ul><ul><li>Ash </li></ul><ul><li>Sulfur </li></ul><ul><li>Copper Strip Corrosion </li></ul><ul><li>Cetane Number </li></ul><ul><li>Cetane Index </li></ul><ul><li>Aromaticity </li></ul><ul><li>Cloud Point </li></ul>
    12. 13. Cetane Number <ul><li>Measures the readiness of a fuel to auto-ignite. </li></ul><ul><li>High cetane means the fuel will ignite quickly at the conditions in the engine (does not mean the fuel is highly flammable or explosive). </li></ul><ul><li>Most fuels have cetane numbers between 40 and 60. </li></ul><ul><li>ASTM D 975 requires a minimum cetane number of 40 </li></ul><ul><li>Premium Diesel fuel typically has a cetane of 47 </li></ul><ul><li>ASTM methods are ASTM D-613 (ISO 5165) and D-6890 </li></ul>
    13. 14. Cetane <ul><li>Cetane engine shown above from petroleum testing facility </li></ul><ul><li>Ignition Delay: the period that occurs between the start of fuel injection and the start of combustion; the higher the cetane number, the shorter the ignition delay and the better the quality of combustion. </li></ul>
    14. 15. 3 PROPANE METHANOL ETHANOL 8 ISO OCTANE (GASOLINE) 20 CETANE (DIESEL FUEL) Benzene Toluene Xylene
    15. 16. Low Cetane Impact Poor Ignition Quality Long ignition delay Abnormal Combustion Possible High Combustion Pressure Increased Engine stress Excessive Engine Knock Smoke on Cold start
    16. 17. Cetane Index <ul><li>Cetane index is used as a substitute for the cetane number . </li></ul><ul><li>The cetane index is calculated based on the fuel's density and boiling range. </li></ul><ul><li>Two methods used ASTM D-976 or D-4737. </li></ul><ul><li>Cetane improvers that may be added are not accounted for in the index </li></ul>
    17. 18. Boiling Point and Volatility <ul><li>Diesel fuel volatility needs vary for engine load, size, & speed </li></ul><ul><li>Buses & trucks benefit from more volatile fuel </li></ul><ul><li>ASTM D975 sets a min-max range </li></ul><ul><li>Defines the upper and lower limits for 90% distilled point. </li></ul><ul><ul><li>No. 1 diesel: no lower limit, upper = 288 C </li></ul></ul><ul><ul><li>No. 2 diesel: lower limit = 282 C, upper = 338 C. </li></ul></ul><ul><li>282C - 338C </li></ul>
    18. 19. 90% Distillation Temperature <ul><li>Volatility or Boiling Point is controlled by the Distillation specifcaition or T90 </li></ul><ul><li>Primarily used to separate diesel fuels into different grades. </li></ul><ul><li>Limits the amount of wax allowed in No. 1 </li></ul><ul><li>If distillation temperatures are too low, then the fuel may have difficulty meeting the flashpoint requirement. </li></ul><ul><li>If distillation temperatures are too high, then there is an increased tendency of the fuel to deposit on the cylinder wall, where it can be swept down past the rings and into the lube oil. </li></ul>
    19. 20. Viscosity <ul><li>Low viscosity = power loss, component wear due to injector leaking or injection pump leak-down </li></ul><ul><li>Low viscosity = poor lubrication ability </li></ul><ul><li>High viscosity = Poor fuel dispersion, ie improper injector spray pattern </li></ul><ul><li>High viscosity = high pump resistance and early pump failure </li></ul><ul><li>Critical property for fuel injection system performance </li></ul><ul><li>Measured with ASTM D 445. </li></ul><ul><li>#1 diesel fuel = 1.3 – 2.4 mm 2 /s </li></ul><ul><li>#2 diesel fuel = 1.9 – 4.1 mm 2 /s </li></ul>
    20. 21. Carbon Residue <ul><li>Measure of a diesel fuel’s tendency to form engine deposit </li></ul><ul><li>Tests basically involve heating a sample of fuel to a temperature where the fuel will pyrolyze (decompose without oxygen), leaving a carbon-rich deposit (about 500 °C) </li></ul><ul><li>Test is frequently done on the 10% residue of fuel distillation. </li></ul><ul><li>Limitation is 0.35 mass percent for No. 2 D </li></ul><ul><li>Limitation is 0.15 mass percent for No. 1 D </li></ul>
    21. 22. Ramsbottom Carbon Residue <ul><li>There are many tests for carbon residue: </li></ul><ul><ul><li>Ramsbottom (D 524) </li></ul></ul><ul><ul><li>Conradson (D 189) </li></ul></ul><ul><ul><li>Micro Method (D 4530) </li></ul></ul><ul><li>Diesel fuel specification requires Ramsbottom </li></ul><ul><li>Carbon reside can vary with refinery processes </li></ul>
    22. 23. Sulfur Content <ul><li>Sulfur can impact engine wear and deposits due varying levels </li></ul><ul><li>Sulfur in diesel will now harm new emission control devices of 2007 & newer vehicles </li></ul><ul><li>Sulfur burns to sulfur dioxide and sulfur trioxide, which can combine with water to form sulfuric acid. </li></ul><ul><li>Small droplets of sulfuric acid and other sulfates contribute to particulate emissions. </li></ul><ul><li>Sulfur is limited by the EPA for both on & off road diesel fuels: </li></ul><ul><ul><li>In 1993: Reduced from 5000 ppm to 500 ppm </li></ul></ul><ul><ul><li>In 2006: Reduced from 500 ppm to 15 ppm </li></ul></ul>
    23. 24. Sulfur Testing <ul><li>ASTM D 129 was traditional method but did not have sensitivity for new low sulfur fuels. (Bomb method) </li></ul><ul><li>ASTM D 2622, X-Ray Spectrometry, is more sensitive but may not be adequate for 15 ppm diesel fuels. </li></ul>
    24. 25. Flashpoint <ul><li>Measures the temperature at which the vapors above the liquid can be ignited. </li></ul><ul><li>Primarily used to determine whether a liquid is flammable or combustible </li></ul><ul><li>Flashpoint is important for safety and hazard rating </li></ul><ul><li>Both DOT and OSHA say that any liquid with a flash point below 100F is flammable </li></ul><ul><li>ASTM D 93 is most common test for diesel fuels. </li></ul><ul><li>Can also be used to identify contamination from other fuels. </li></ul><ul><li>No. 1 = 38 °C, No. 2 = 52°C </li></ul>
    25. 26. Flashpoint
    26. 27. Low temperature Operation <ul><li>Cloud point is the measurement of low temperate operation </li></ul><ul><li>It dictates the temperature at which fuel first starts to crystallize and wax up when cooled </li></ul><ul><li>Cloud point can predicate fuel filter clogging in some fuel delivery systems, but not all </li></ul><ul><li>Other Low temp tests include: </li></ul><ul><li>CFPP: Cold Filter Plugging Point </li></ul><ul><li>LTFT: Low Temperature Flow Test </li></ul><ul><li>Pour Point and Cold Soak Filtration Test </li></ul>
    27. 28. Cloud Point <ul><li>No specific value is given in ASTM D975. </li></ul><ul><li>Requirements vary depending on geography. </li></ul><ul><li>10 th percentile temperature map corresponds to the minimum temperature that would be reached no more than 3 days out of 30 for the month.  </li></ul><ul><li>ASTM D 975 contains similar maps for other low temperature months in the United States. </li></ul>
    28. 29. Ash <ul><li>Abrasive Solids </li></ul><ul><li>Soluble metallic soaps </li></ul><ul><li>Originates from inorganic fuel components </li></ul><ul><li>D 975 requires ash to be < 0.01%, by mass </li></ul><ul><li>Injector & Fuel pump wear </li></ul><ul><li>Piston and Ring wear </li></ul><ul><li>Solids = engine deposits </li></ul><ul><li>Low ash lubricating oils - NEW </li></ul>
    29. 30. Copper Strip Corrosion <ul><li>Used to predict problems with copper, brass, or bronze components in a fuel system </li></ul><ul><li>A measure of corrosiveness </li></ul><ul><li>Polished copper strip is placed in fuel for 3 hours at 50 °C, then cleaned with a solvent and inspected for tarnish or corrosion. </li></ul><ul><li>The strip is given a score between 1 and 4 with subdivisions indicated by letters, i.e. 2c means moderate tarnish with lavender coloring. </li></ul><ul><li>Diesel fuel is allowed to be No. 3, which allows all tarnish but no actual corrosion. </li></ul>
    30. 31. Water and Sediment <ul><li>Measures free, not emulsified, water and insoluble particles. </li></ul><ul><li>Uses a centrifuge and cone-shaped or pear-shaped bottles. </li></ul><ul><li>Total volume of water and sediment must be < 0.05%. </li></ul><ul><li>(500 ppm) </li></ul><ul><li>Contamination issue in supply line </li></ul><ul><li>Engine impact: Filter plugging, fuel injection system wear, and corrosion, and opportunity for microbial growth </li></ul>
    31. 32. Lubricity <ul><li>Lubricity test methods are continually improving and being evaluated </li></ul><ul><li>Most common tests available to test lubricity: </li></ul><ul><ul><li>SLBOCLE (scuffing load ball on cylinder lubricity evaluator) </li></ul></ul><ul><ul><ul><li>ASTM D 6078-99 </li></ul></ul></ul><ul><ul><li>HFRR (high frequency reciprocating rig) </li></ul></ul><ul><ul><ul><li>ASTM D 6079-99 </li></ul></ul></ul><ul><li>D975 points to the HFRR test </li></ul><ul><li>Limitation is 520 micron max of wear at 60C </li></ul>
    32. 33. SLBOCLE <ul><li>SLBOCLE “ Scuffing Load Ball-On Cylinder Lubricity Evaluator” </li></ul><ul><li>Steel ball bearing on a steel rotating-ring </li></ul><ul><li>Immersed in the test fluid </li></ul><ul><li>Weight is applied until a “scuff” mark is seen on the rotating ring </li></ul><ul><li>Tangential force recorded </li></ul><ul><li>High Friction coefficient = scuffing </li></ul><ul><li>3100 grams without scuffing passes the SLBOCLE. (SWRI) </li></ul>
    33. 34. HFRR <ul><li>A steel ball </li></ul><ul><li>Reciprocated (1mm) </li></ul><ul><li>200g load at 50 Hz for 75 minutes </li></ul><ul><li>2 mL of Fuel </li></ul><ul><li>Adjust to 25 °C or 60 °C (77 °F or 140 °F </li></ul><ul><ul><li>60°C preferred </li></ul></ul><ul><li>Ball contacts test disk (in fuel) </li></ul>
    34. 35. Enhanced Lubricity <ul><li>Equipment benefits </li></ul><ul><ul><li>Superior lubricity </li></ul></ul><ul><ul><li>B2 has up to 66% more lubricity than #2 Diesel </li></ul></ul><ul><li>EPA required sulfur reduction in diesel </li></ul><ul><li>No overdosing concerns </li></ul>1-2% 66% Improvement
    35. 36. Density <ul><li>Specific gravity – ratio of the density of the fuel to the density of water. </li></ul><ul><ul><li>#1 diesel = 0.81 </li></ul></ul><ul><ul><li>#2 diesel = 0.840 – 0.855 </li></ul></ul><ul><li>API gravity – common in petroleum industry. API = 141.5/SG – 131.5 </li></ul><ul><li>Can be one indicator of fuel economy, power, deposits, wear, and exhaust smoke </li></ul><ul><li>For example, a low API (or high density) has bore BTUs/gallon which could improve fuel economy </li></ul>
    36. 37. Energy Content <ul><li>Heating value of the fuel </li></ul><ul><li>Not specified by ASTM </li></ul><ul><li>Typically expressed as BTUs/gallon </li></ul><ul><li>Engine Manufacturers </li></ul><ul><li>Impact fuel ecomony </li></ul><ul><li>No. 2 D </li></ul><ul><li>130,000 BTUs/gallon </li></ul><ul><li>Gasoline </li></ul><ul><li>114,200 BTUs/gallon </li></ul>
    37. 38. Thermal & Oxidative Stability <ul><li>Chemical degradation occurs with contact with oxygen for long periods or at high temperatures. </li></ul><ul><li>Oxidation of diesel fuel can form insolubles and peroxides </li></ul><ul><li>Peroxides increase deposits and gumming on fuel pumps and injection systems </li></ul><ul><li>Filter plugging will also occur </li></ul><ul><li>ASTM D975 now specifies a stability parameter </li></ul>
    38. 39. Diesel Fuel Additives
    39. 40. Recent Changes in ASTM D975 Diesel Fuel specification <ul><li>Acid Number </li></ul><ul><li>Allowance of up to 5 % biodiesel content </li></ul><ul><li>Lubricity </li></ul><ul><li>Stability </li></ul>
    40. 41. Resources for Diesel Fuel Properties <ul><li>ASTM International </li></ul><ul><li>EPA, Environmental Protection Agency </li></ul><ul><li>Changes in Diesel Fuel </li></ul><ul><li>USDA Biodiesel education </li></ul><ul><li>• Internal Combustion Engine Fundamentals, John B. Heywood, McGraw Hill, 1988 ISBN 0-07-100499-8 </li></ul><ul><li>• Automotive Fuels Reference Book, Keith Owen, Trevor Coley SAE, 1995, ISBN 1-56091-589-7 </li></ul>

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