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What is an Engine

What is an Engine. A device that converts chemical energy it to mechanical energy Also converts linear force into mechanical force. Basic Engine Theory. Requires external fuel source (motor does not) Converts chemical energy to mechanical energy Only about 40% effecient

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What is an Engine

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  1. What is an Engine • A device that converts chemical energy it to mechanical energy • Also converts linear force into mechanical force

  2. Basic Engine Theory • Requires external fuel source (motor does not) • Converts chemical energy to mechanical energy • Only about 40% effecient • Generates a lot of waste heat and sound

  3. Two-Stroke Engine Operation • Simplest design with few moving parts • Highest power/weight ratio • Ineffecient, dirty and noisy

  4. Picture of a basic two stroke cylinder

  5. Four-Stroke Engine Operation • This is the engine design in almost all trucks on the road • Utilizes four stroke of the piston for one complete cycle

  6. The four strokes The four strokes are: • Intake • Compression • Power • exhaust

  7. Rotating vs. Reciprocating Mass • Crankshaft, flywheel, and lower portion of connecting rod are considered rotating mass • Piston and upper portion of connecting rod are considered reciprocating mass • Cams and valves also rotate and reciprocate

  8. Combustion Chamber • the area inside the engine where the fuel/air mixture is compressed and then ignited • formed on one side by the shape cast into the cylinder head, and on the other side by the top of the piston

  9. Combustion Chamber • THINK • When is the chamber’s dimension is at its smallest

  10. Types of Combustion Chambers Hemispherical The "Hemi" Combustion Chamber • Offer the least amount of compromise for the efficiency gained • Hemispherical combustion chamber is one half of a sphere cast into the bottom of the cylinder head

  11. Hemispherical design Hemispherical chambers generally have a central spark plug

  12. Wedge-Shaped Chambers • resembles an inclined basin recessed into the deck of the head • The relatively steep walls in such chamber design force the air/fuel flow path and deflect and force it to move in a downward spiral around the cylinder axis

  13. Wedge-Shaped Chambers

  14. Diesel fuel • crude oil, is naturally found in the earth • After refining, it can be separated into several different kinds of fuels, including gasoline, jet fuel, kerosene and, of course, diesel

  15. Diesel fuel • Diesel fuel is heavier and oilier than gasoline • evaporates much more slowly • boiling point is actually higher than the boiling point of water • It evaporates more slowly because it is heavier

  16. Diesel fuel • Diesel fuel has a higher energy density than gasoline • 3.8 L of diesel fuel contains approximately 155x106 joules (147,000 BTU) • gasoline contains 132x106 joules (125,000 BTU) for 3.8L

  17. Diesel fuel • (C8H18), typical of the molecules found in gasoline • (C16H34), typical of diesel fuel • C is for carbon and H is for hydrogen

  18. Diesel fuel • In a complete burn, the oxygen in the air combines with the hydrogen to form water (H2O) and with the carbon to form carbon dioxide (CO2). • If the burning is not complete, some of the carbon atoms only combine with one oxygen atom rather than two, to form carbon monoxide (CO)

  19. Diesel fuel • unburned hydrocarbon molecules can also come out the tailpipe • hydrocarbons react with nitrogen oxides (another pollutant from combustion) in the presence of sunlight to form ozone

  20. Diesel fuel classification • Diesel  fuel  is  graded  and  designated  by  the American Society for Testing and Materials (ASTM • Its specific gravity and high and low heat values are listed by the American Petroleum Institute (API).

  21. Diesel fuel classification • Each oil refiner and supplier attempts to produce diesel fuels that comply as closely as possible with  ASTM  and  API  specifications • Due to different crude oil supplies, the diesel fuel may either be on the high or low end of the prescribed heat scale in Btu per pound or per gallon

  22. Diesel fuel classification • There are only two recommended grades of fuel that is considered acceptable for use in high-speed heavy-duty vehicles. These are the No. 1D or No. 2D

  23. Diesel fuel Grade:1D • Fuels within this classification are applicable for use in high- speed  engines  in  service  involving  frequent  and relatively wide variations in loads and speeds • In cold weather conditions, No. 1D fuel allows the engine to start  easily.

  24. Diesel fuel Grade:1D • Heavy-duty  high-speed diesel  vehicles  operating  in  continued  cold-weather conditions, No. 1D fuel provides better operation than the heavier No. 2D. • Require a minimum cetane number (CN) above 40

  25. Diesel fuel Grade:2D • Grade No. 2D has a lower volatility • This fuel is used more by truck fleets, due to its greater heat value per /L, particularly in warm to moderate climates • Has higher calorific value • Recommended for use with constant load and speed

  26. Diesel fuel Grade:2D • Like # 1D the 2D CN is required to be above 40 • Even though No. 1D fuel has better properties for cold weather operations, many still use No.  2D  in  the  winter,  using  fuel  heater/water  separators to provide suitable starting, as well as fuel additive

  27. Selecting the correct diesel fuel • Seven factors should be considered when selecting fuel to maximize performance and extends engine life. They are: 1. Starting  characteristics 2. Fuel handling 3. Wear on injection equipment

  28. Selecting the correct diesel fuel 4. Wear on pistons 5. Wear on rings, valves, and cylinder liners 6. Engine  maintenance 7. Fuel cost and availability

  29. Cetane Number(CN) • Cetane  number  is  a  measure  of  the  fuel  volatility; the higher the rating, the easier the engine will start and the combustion process will be smoother • The Ideal CN is 100 and a poor CN is 0 • Increasing the CN decrease fuel mileage

  30. Cetane Number(CN) • The CN rating is set by the ASTM • Current 1D and 2D diesel fuels have a cetane rating between 40 and 45. • The  higher  the  cetane  rating,  the easier the fuel will ignite once injected into the diesel combustion chamber.

  31. Cetane Number(CN) • If the cetane number is too low, you  will  have  difficulty  in  starting, • Engine knock and puffs of white smoke during warm-up in cold weather.

  32. Octane rating • Compression is one of the four strokes on a four stroke engine • The amount of compression is called the compression ratio of the engine.

  33. Octane rating

  34. Octane rating • The octane rating of gasoline tells much the fuel can be compressed before it spontaneously ignites • Spontaneous ignition causes engine knock • Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

  35. Octane rating • The compression ratio of your engine determines the octane rating of the gas you must use in the car • “High-performance engine" has a higher compression ratio and requires higher-octane fuel • 87 Octane gasoline contains 87-percent octane and 13-percent heptane

  36. Volatility • The tendency of a liquid to Vaporize • Volatility rating for diesel is crucial in summer when its higher fraction tends to boil off lowering the CN

  37. Calorific value • This is the potential heat energy of a fuel • It is measured in BTU, Joules, or calories

  38. Viscosity • Viscosity is the measure of a liquid’s resistance to flow • Viscosity decreases as temperature increases • This means that a fluid with a high viscosity is heavier than a fluid with low viscosity.

  39. Viscosity • High  viscosity  fuel  may  cause  extreme pressures  in  the  injection  systems  and  will  cause reduced atomization and vaporization of the fuel spray • The viscosity of diesel fuel must be low enough to flow freely at its lowest operational temperature, yet high enough to provide lubrication to the moving parts of the finely machined injectors

  40. Viscosity measurement • Recommended  fuel  oil  viscosity  for  high-speed diesel engines is generally in the region of 39 SSU (Seconds  Saybolt  Universal)   • This is  derived  from using a Saybolt Viscosimeter to measure the time it takes for a quantity of fuel to flow through a restricted hole in a tube

  41. Cloud point • This is the temperature at which fuel begins to precipitate as wax crystal. When these crystals become large enough, the fuel will appears cloudy. This is the actual cloud point

  42. Fire point • This is the temperature at whicha fuel evaporates enough flammable vapor burn continuously in the presence of air • Images

  43. Flame propagation • This represents the way in which a fuel combusts inside the engine cylinder • This is determine by: the flame front, cylinder gas dynamics, AFR, temperature and fuel density

  44. Pour point • This Generally depicts the lowest temperature at which a fuel can be pumped • Pour point is usually 3deg.C (5deg.F) to 15deg.C ( 25 deg.F) below cloud point

  45. Specific gravity • The specific gravity of a fuel is the the weight of a volume of the fuel compared to the weight of the same volume of water. • The S.G. of petroleum base fuel is a direct measure of its heat value

  46. Sulfur content • This is simply the amount of sulfur present in the fuel • Sulfur is present in most crude petroleum fuel but is more prominent in the heavier fuels such as diesel. • The problem with sulfur is that when combusted, the sulfur in the fuel oxidized and form sulfur dioxide

  47. Sulfur content • The sulfur dioxide reacts with water to form sulfuric acid • Diesel fuel as been legislated to be ultra low sulfur(ULS) fuel

  48. Ultra low sulfur (ULS)fuel

  49. Ultra low sulfur fuel • Ultra low sulphur diesel fuel has been refined so that its sulphur content is 15 parts per million (ppm) or less • This is 97 percent cleaner than the standard highway-use diesel fuel sold in the US, which contains an average of 500 ppm of sulphur

  50. Ultra low sulfur fuel • The move toward ULSD is aimed at lowering diesel engines' harmful exhaust emissions and improving air quality • ULSD fuel will work with a new generation of diesel enginesand exhaust system as well

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