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Small Gasoline Engines

Small Gasoline Engines. Engine. “A machine for converting energy into mechanical force and motion.”. Heat Engine. An engine which uses heat to convert the chemical energy of a fuel into mechanical force and motion. Two general categories based on design. External combustion engine.

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Small Gasoline Engines

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  1. Small Gasoline Engines

  2. Engine • “A machine for converting energy into mechanical force and motion.”

  3. Heat Engine An engine which uses heat to convert the chemical energy of a fuel into mechanical force and motion

  4. Two general categories based on design. External combustion engine Internal combustion engine

  5. Internal Combustion Engines

  6. Internal Combustion--Intro • Many different designs are used for internal combustion engines. • Engines can be classified by: • Size • Ignition system • Strokes per cycle • Crankshaft orientation • Control system

  7. Engine Size Engines are available in a wide range of sizes. Industry definition: “A small engine is an internal combustion engine generally rated up to 25 horsepower.”

  8. Largest • The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today. The cylinder bore is just under 38" and the stroke is just over 98". Each cylinder displaces 111,143 cubic inches (1,820 liters) and produces 7,780 horsepower. Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the fourteen cylinder version.

  9. Smallest • Not much bigger than a stack of pennies, the "mini engine" is the first engine of its size to deliver power on a continuous basis. • Currently will produce 2.5 watts of electricity (0.00335 hp). • Uses 1/2 fluid ounce of fuel per hour

  10. Engines are further classified by ignition, number of strokes, cylinder design, shaft orientation and cooling system. (pg. 2 & 3)

  11. Ignition • Spark ignition Compression ignition

  12. Number of Strokes • Four stroke Two stroke

  13. Cylinder Design Three Common Cylinder Orientations For Single Cylinder Engines • Small engines usually have one or two cylinders, but may have as many as four. Vertical Horizontal Slanted

  14. Cylinder Design-cont. Three common cylinder configuration in multiple cylinder engines: V Horizontally opposed In-line

  15. Cylinder Design-cont. Small gas engines use three crankshaft orientations: Multi-position Horizontal Vertical

  16. When fuel is oxidized (burned) heat is produced. • Only approximately 30% of the energy released is converted into useful work. • The remaining (70%) must be removed from the engine to prevent the parts from melting.

  17. Excess heat is removed by: • Cooling system • Exhaust system • Lubrication system • Radiation

  18. Additional heat is also generated by friction between the moving parts. • This heat must also be removed.

  19. Controls • Traditionally engines are controlled by mechanical means. • Governor • Throttle • Choke • Etc. • Honda has an engine with an electronic control unit (ECU). • ECU - Electronic Control Unit • Monitors and controls engine functions including Throttle, Choke, Ignition Timing, Oil Alert • Offers programmable governor and throttle modes for unprecedented flexibility and diagnostic LED for trouble shooting • Stepper motors precisely control throttle and choke position

  20. Small Engine Development(pg 5) • Year Engine Designer/developer • 1680 Gunpowder Christian Huygens • 1698 Savery Pump Thomas Saverly • 1712 Newcomen Steam Thomas Newcomen • 1763 Watt Double-acting steam James Watt • 1801 Coal gas/electric ignition Eugene Lebon • 1802 High pressure steam Richard Trevithick • 1859 Pre-mixed fuel and air Etienne Lenoir • 1862 Gasoline Nikolaus Otto • 1876 Four cycle gasoline Nikolaus Otto • 1892 Diesel Rudolf Diesel • 1953 Die-cast aluminum B&S

  21. Physical Principles of Engines

  22. Energy Conversion • “All internal combustion engines exhibit and convert different forms of energy.” • “Energy is the resource that provides the capacity to do work”. • The two forms of energy used in engines are potential and kinetic.

  23. Potential Energy • “Stored energy a body has due to its position, chemical state, or condition.”

  24. Examples of Potential Energy A compressed spring has potential energy due to its mechanical condition. • Fuels have potential energy based on their chemical state. Water behind a dam has potential energy due to difference in elevation.

  25. Kinetic Energy

  26. A speeding automobile • Flywheel Water falling over a dam.

  27. Heat Chemistry Temperature Force Power Pressure Lever Torque Horsepower Internal combustion engines operate utilizing the principles of nine (9) physical phenomena.

  28. Heat • “Kinetic energy caused by atoms and molecules in motion within a substance.”

  29. Engines use heat in two ways In a small engine, as the air-fuel charge is compressed, internal energy increases, producing heat. • When the charge is ignited and the burning gases expand, internal energy decreases and heat is given up.

  30. Heat Transfer • Heat is always transferred from an object of higher heat to one with lower heat. • Transfer is by conduction, convection, and radiation

  31. Temperature • Temperature (oF) is the intensity of heat”. • The amount of heat is measured in BTU’s.

  32. British Thermal Unit (BTU) • The amount of heat required to raise the temperature of 1 pound of water 1 oF.

  33. Force • “Anything that changes or tends to change the state of rest or motion of a body.” • A force can result in pressure, torque or work, depending on how it is applied.

  34. PRESSURE • The cylinder pressure is not constant. It is highest right after combustion, as much as 2,000 psi, and decreases as the piston moves away from the cylinder head. “A force acting on a unit of area.”

  35. Force • In engines the amount of force exerted on the top of a piston is determined by the cylinder pressure during the combustion process.

  36. Torque • “A force acting on the perpendicular radial distance from a point of rotation.” To (lb-ft) = Force x Radius

  37. Lever with both resistance and effort applied. which pivots on a fulcrum • “A lever is a simple machine that consists of a rigid bar”, Applied force Resultant force

  38. Power is the rate of doing work

  39. 1 Hp = 33,000 ft-lb/min A unit of power developed by James Watt to provide a basis for comparing the amount of power produced by horses and other engines. Horsepower

  40. Chemistry All internal combustion engines utilize some form of fossil fuel. • When the hydrocarbon is ignited in the presence of air, the oxygen causes an exchange of elements which release heat energy. A fossil fuel is composed of carbon and hydrogen.

  41. PERFECT COMBUSTION EQUATION Unfortunately, combustion is not perfect---the result is many unwanted gasses and compounds.

  42. The End

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