CHAPTER 7 Diesel and Biodiesel Fuels

1. CHAPTER 7 Diesel and Biodiesel Fuels

2. OBJECTIVES After studying Chapter 7, the reader will be able to: • Explain diesel fuel specifications. • List the advantages and disadvantages of biodiesel. • Discuss API gravity. • Explain E-diesel specifications.

3. API gravity ASTM B20 Biodiesel Cetane number Cloud point Diesohol E-diesel Petrodiesel PPO SVO UCO ULSD WVO KEY TERMS

4. DIESEL FUELFEATURES OF DIESEL FUEL • Diesel fuel must meet an entirely different set of standards than gasoline. • Diesel fuel contains 12% more heat energy than the same amount of gasoline. • The fuel in a diesel engine is not ignited with a spark, but is ignited by the heat generated by high compression. • The pressure of compression (400 to 700 PSI or 2,800 to 4,800 kilopascals) generates temperatures of 1200°F to 1600°F (700°C to 900°C), which speeds the preflame reaction to start the ignition of fuel injected into the cylinder.

5. DIESEL FUELDIESEL FUEL REQUIREMENTS • All diesel fuel must have the following characteristics: • Cleanliness • Low-temperature fluidity • Cloud point

6. DIESEL FUELCETANE NUMBER • The cetane number for diesel fuel is the opposite of the octane number for gasoline. • The cetane number is a measure of the ease with which the fuel can be ignited. • The cetane rating of the fuel determines, to a great extent, its ability to start the engine at low temperatures and to provide smooth warm-up and even combustion. • The cetane rating of diesel fuel should be between 45 and 50. • The higher the cetane rating, the more easily the fuel is ignited.

7. DIESEL FUELSULFUR CONTENT • The sulfur content of diesel fuel is very important to the life of the engine. • Sulfur in the fuel creates sulfuric acid during the combustion process, which can damage engine components and cause piston ring wear. • Federal regulations are getting extremely tight on sulfur content to less than 15 parts per million (PPM). High-sulfur fuel contributes to acid rain.

8. FIGURE 7–1 (a) Regular diesel fuel on the left has a clear or greenish tint, whereas fuel for off-road use is tinted red for identification. (b) A fuel pump in a farming area that clearly states the red diesel fuel is for off-road use only. DIESEL FUELDIESEL FUEL COLOR • Diesel fuel intended for use on the streets and highways is clear or green in color. Diesel fuel to be used on farms and off-road use is dyed red.

9. DIESEL FUELGRADES OF DIESEL FUEL • American Society for Testing Materials (ASTM) also classifies diesel fuel by volatility (boiling range) into the following grades: • GRADE #1 • GRADE #2

10. DIESEL FUELDIESEL FUEL SPECIFIC GRAVITY TESTING • The density of diesel fuel should be tested whenever there is a driveability concern. • The density or specific gravity of diesel fuel is measured in units of API gravity. • API gravity is an arbitrary scale expressing the gravity or density of liquid petroleum products devised jointly by the American Petroleum Institute and the National Bureau of Standards.

11. FIGURE 7–2 Testing the API viscosity of a diesel fuel sample using a hydrometer. DIESEL FUELDIESEL FUEL SPECIFIC GRAVITY TESTING

12. DIESEL FUELDIESEL FUEL HEATERS • Diesel fuel heaters, either coolant or electric, help prevent power loss and stalling in cold weather. • The heater is placed in the fuel line between the tank and the primary filter. • Some coolant heaters are thermostatically controlled, which allows fuel to bypass the heater once it has reached operating temperature.

13. FIGURE 7–3 An electrical resistance heater coil in the air inlet on a General Motors 6.5-liter V-8 diesel engine used to warm the air entering the engine. DIESEL FUELDIESEL FUEL HEATERS

14. How Can You Tell If Gasoline Has Been Added to the Diesel Fuel by Mistake? • If gasoline has been accidentally added to diesel fuel and is burned in a diesel engine, the result can be very damaging to the engine. The gasoline can ignite faster than diesel fuel, which would tend to increase the temperature of combustion. This high temperature can harm injectors and glow plugs, as well as pistons, head gaskets, and other major diesel engine components. If contaminated fuel is suspected, first smell the fuel at the filler neck. If the fuel smells like gasoline, then the tank should be drained and refilled with diesel fuel. If the smell test does not indicate a gasoline smell (or any rancid smell), then test a sample for proper API gravity.

15. DIESEL FUELULTRA-LOW-SULFUR DIESEL FUEL • The emission controls used on 2007 and newer diesel engines require the use of ultra-low-sulfur diesel (ULSD) for reliable operation. • Ultra-low-sulfur diesel (ULSD) will eventually replace the current highway diesel fuel, low-sulfur diesel, which can have as much as 500 PPM of sulfur. • ULSD is required for use in all model year 2007 and newer vehicles equipped with advanced emission control systems. • ULSD looks lighter in color and has less smell than other diesel fuel.

16. BIODIESELDEFINITION OF BIODIESEL • Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant greases. • Biodiesel is safe, biodegradable, and reduces serious air pollutants such as particulate matter (PM), carbon monoxide, and hydrocarbons. • Biodiesel is defined as mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats which conform to ASTM D6751 specifications for use in diesel engines. • Biodiesel refers to the pure fuel before blending with diesel fuel.

17. FIGURE 7–4 A pump decal indicating that the biodiesel fuel is ultra-low-sulfur diesel (ULSD) and must be used in 2007 and newer diesel vehicles. BIODIESELDEFINITION OF BIODIESEL

18. BIODIESELBIODIESEL BLENDS • Biodiesel blends are denoted as “BXX” with “XX” representing the percentage of biodiesel contained in the blend (i.e., B20 is 20% biodiesel, 80% petroleum diesel). • Blends of 20% biodiesel with 80% petroleum diesel (B20) can generally be used in unmodified diesel engines; however, users should consult their OEM and engine warranty statement.

19. BIODIESELFEATURES OF BIODIESEL • Biodiesel has the following characteristics: • Purchasing biodiesel in bulk quantities decreases the cost of fuel. • Biodiesel maintains similar horsepower, torque, and fuel economy. • Biodiesel has a higher cetane number than conventional diesel, which increases the engine’s performance. • It is nontoxic, which makes it safe to handle, transport, and store. Maintenance requirements for B20 vehicles and petrodiesel vehicles are the same. • Biodiesel acts as a lubricant and this can add to the life of the fuel system components.

20. E-DIESEL FUELDEFINITION OF E-DIESEL • E-diesel, also called diesohol outside of the United States, is standard No. 2 diesel fuel that contains up to 15% ethanol. • While E-diesel can have up to 15% ethanol by volume, typical blend levels are from 8% to 10%.

21. E-DIESEL FUELCETANE RATING OF E-DIESEL • The higher the cetane number, the shorter the delay between injection and ignition. • Normal diesel fuel has a cetane number of about 50. • Adding 15% ethanol lowers the cetane number. • To increase the cetane number back to that of conventional diesel fuel, a cetane-enhancing additive is added to E-diesel. • The additive used to increase the cetane rating of E-diesel is ethylhexylnitrate or ditertbutyl peroxide.

22. I Thought Biodiesel Was Vegetable Oil? • Biodiesel is vegetable oil with the glycerin component removed by means of reacting the vegetable oil with a catalyst. The resulting hydrocarbon esters are 16 to 18 carbon atoms in length, almost identical to the petroleum diesel fuel atoms. This allows the use of biodiesel fuel in a diesel engine with no modifications needed. Biodiesel-powered vehicles do not need a second fuel tank, whereas vegetable-oil-powered vehicles do. There are three main types of fuel used in diesel engines.

23. I Thought Biodiesel Was Vegetable Oil? • These are: • Petroleum diesel, a fossil hydrocarbon with a carbon chain length of about 16 carbon atoms. • Biodiesel, a hydrocarbon with a carbon chain length of 16 to 18 carbon atoms. • Vegetable oil is a triglyceride with a glycerin component joining three hydrocarbon chains of 16 to 18 carbon atoms each, called straight vegetable oil (SVO). • Other terms used when describing vegetable oil include: • Pure plant oil (PPO)—a term most often used in Europe to describe SVO • Waste vegetable oil (WVO)—this oil could include animal or fish oils from cooking • Used cooking oil (UCO)—a term used when the oil may or may not be pure vegetable oil

24. I Thought Biodiesel Was Vegetable Oil? • Vegetable oil is not liquid enough at common ambient temperatures for use in a diesel engine fuel delivery system designed for the lower-viscosity petroleum diesel fuel. Vegetable oil needs to be heated to obtain a similar viscosity to biodiesel and petroleum diesel. This means that a heat source needs to be provided before the fuel can be used in a diesel engine. This is achieved by starting on petroleum diesel or biodiesel fuel until the engine heat can be used to sufficiently warm a tank containing the vegetable oil.

25. I Thought Biodiesel Was Vegetable Oil? • It also requires purging the fuel system of vegetable oil with petroleum diesel or biodiesel fuel prior to stopping the engine to avoid the vegetable oil thickening and solidifying in the fuel system away from the heated tank. The use of vegetable oil in its natural state does, however, eliminate the need to remove the glycerin component. Many vehicle and diesel engine fuel system suppliers permit the use of biodiesel fuel that is certified as meeting testing standards. None permit the use of vegetable oil in its natural state.

26. SUMMARY • Diesel fuel produces 12% more heat energy than the same amount of gasoline. • Diesel fuel requirements include cleanliness, low-temperature fluidity, and proper cetane rating. • Emission control devices used on 2007 and newer engines require the use of ultra-low-sulfur diesel (ULSD) that has less than 15 parts per million (PPM) of sulfur. • The density of diesel fuel is measured in a unit called API gravity.

27. SUMMARY • The cetane rating of diesel fuel is a measure of the ease with which the fuel can be ignited. • Biodiesel is the blend of vegetable-based liquid with regular diesel fuel. Most diesel engine manufacturers allow the use of a 5% blend, called B20 without any changes to the fuel system or engine. • E-diesel is a blend of ethanol with diesel fuel up to 15% ethanol by volume.

28. REVIEW QUESTIONS • What is meant by the cloud point? • What is ultra-low-sulfur diesel? • Biodiesel blends are identified by what designation?

29. CHAPTER QUIZ 1. What color is diesel fuel dyed if it is for off-road use only? • Red • Green • Blue • Yellow

30. CHAPTER QUIZ 2. What clogs fuel filters when the temperature is low on a vehicle that uses diesel fuel? • Alcohol • Sulfur • Wax • Cetane

31. CHAPTER QUIZ 3. The specific gravity of diesel fuel is measured in what units? • Hydrometer units • API gravity • Grade number • Cetane number

32. CHAPTER QUIZ 4. What rating of diesel fuel indicates how well a diesel engine will start? • Specific gravity rating • Sulfur content • Cloud point • Cetane rating

33. CHAPTER QUIZ 5. Ultra-low-sulfur diesel fuel has how much sulfur content? • 15 PPM • 50 PPM • 500 PPM • 1,500 PPM

34. CHAPTER QUIZ 6. E-diesel is diesel fuel with what additive? • Methanol • Sulfur • Ethanol • Vegetable oil

35. CHAPTER QUIZ 7. Biodiesel is regular diesel fuel with vegetable oil added. • True • False

36. CHAPTER QUIZ 8. B20 biodiesel has how much regular diesel fuel? • 20% • 40% • 80% • 100%

37. CHAPTER QUIZ 9. Most diesel fuel is what grade? • Grade #1 • Grade #2 • Grade #3 • Grade #4

38. CHAPTER QUIZ 10. Most manufacturers of vehicles equipped with diesel engines allow what type of biodiesel? • B100 • B80 • B20 • B5