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Measuring performance

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Transcript

  • 1. Chapter 6 Measuring Engine Performance page 91
  • 2. Basic Terminology
    • Bore & Stroke
    • Engine Displacement
    • Compression Ratio
    • Force
    • Work
    • Power
    • Energy
    • Horsepower
  • 3. Bore
    • Diameter of cylinder
    • 2 X Radius
  • 4. Stroke
    • Distance
      • TDC-BDC
    • Distance piston travels
      • up or down
  • 5. Cylinder Displacement
    • 0.7854 x D2 x stroke
    • or
    • Π x r2 x Stroke
  • 6. Engine Displacement
    • 0.7854 x D 2 x stroke X # of cylinders
    • or
    • Π x r 2 x Stroke x # of cylinders
    • in 3 / 62 = Liters
  • 7. Compression Ratio
    • Volume of cylinder at BDC
    • compared to
    • Area of cylinder at TDC
  • 8. Force
    • pushing or pulling
    • stationary force
    • moving force
    • Centrifugal force
      • spinning
      • FORCE does NOT = Pressure
  • 9. Pressure
    • Pressure is force per given area
    • or
    • Force/Area
    • PSI
    • Force = psi X area
    • Area = force / psi
    • Area = Π R 2
  • 10. Work
    • force applied resulting in movement
    • Work = Force x Distance
    • W = F x D
    • Mechanical advantage (lever, ramp, etc)
    • Effort distance / resistance distance = Mechanical advantage
  • 11. Mechanical Advantage
    • 2’
    10’ 10’ / 2’ = 5 = MA E(effort) = R(resistance)/ MA or E = 500# / 5 = 100 # 500#
  • 12. Power
    • Power is time taken to do the work
    • P = work/time
    • P=W/T
    • Power = feet x Pounds / time
    • or Foot pounds per second?
  • 13. Energy
    • Energy can not be created or destroyed
    • Potential—has the potential to . . .
    • Kinetic
    • Mechanical
    • Chemical
    • Thermal (heat)
    • Light
  • 14. Horsepower
    • Power = work / time P= w/t
    • Hp = 33,00 ft-lb (work) / 1 minute (time)
    • or
    • Hp = 550 ft-lb / 1 second
  • 15. Horsepower Formula
    • 100 ft x 330 lb / 6 seconds = 5500 ft lb / sec
    • dividing this by 550 ft lb / sec (1hp)
    • =
    • (5500 ft-lb /sec) / (550 ft lb / sec) = 10 hp
    • thus
    • 1 hp = rate of work in ft-lb/sec / 50 ft-lb / sec
  • 16. Kinds of Horsepower
    • Brake Horsepower
    • Indicated Horsepower
    • Frictional Horsepower
    • Rated Horsepower
    • Corrected Horsepower
  • 17. Brake Horsepower
    • bhp
    • actual hp delivered
    • what we can use
  • 18. Indicated Horsepower
    • ihp (perfect world)
    • power developed by the burning fuel
    • average of power on 4 strokes (mean)
    • PLANK / 33,000
    • P = mep in lb/in 2
    • L = length of stroke
    • A = Cylinder Area
    • N = power strokes per minute or RPM / 4
    • K = # of cylinders
  • 19. Frictional Horsepower
    • fhp
    • HP lost because of drag
    • fhp = ihp-bhp
  • 20. Rated Horsepower
    • rhp
    • 80% of bhp
  • 21. Corrected Horsepower
    • corrected for elevation (sea level)
    • corrected for temperature
    • barometric pressure
    • quality of fuel
    • humidity
  • 22. Torque
    • Twisting force
    • force x distance
    • ft - lb
    • in – lb
    • Newton - Meters
  • 23. Torque is not Constant
    • Torque will change w/ engine speed
    • More pressure on piston = more torque
  • 24. Torque and Horsepower
    • Unlike torque. . .
    • Horsepower increases with engine speed
    • Torque measure of engine’s twisting force
    • Hp measures engine’s ability to do work
  • 25. Torque and power curves: Skyline
  • 26. Volumetric Efficiency
    • How well an engine breathes
      • draws air/fuel into cylinder
    • Can decrease as engine speed increases
    • Many factors
  • 27. Practical Efficiency
    • How efficiently an engine uses the fuel
  • 28. Mechanical Efficiency
    • % of power developed in cylinder (ihp)
    • compared to
    • power delivered to crankshaft (bhp)
    • friction,
    • Mechanical efficiency = bhp/ihp
  • 29. Thermal Efficiency
    • Heat efficiency
    • How much power produced is used to push the piston down
    • Power is lost to :
      • cooling
      • exhaust
      • 20-25% efficient
      • Exhaust 35% . . .
      • Cooling & Lubrication 35%
  • 30. Brake thermal efficiency
    • =
    • Brake horsepower (bhp x 33,000)
    • 778 Fuel heat value x weight of burned fuel per minute
    • 778 is Joule’s equivalent
    • it is a constant