Two-Stroke Engine Efficiency and Fuel Systems
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Questions and Answers

What happens to the engine speed when the water temperature falls below 115 °F?

  • The engine speed remains constant.
  • The engine speed is reduced to IDLE.
  • The engine speed is increased to throttle 5.
  • The engine speed is raised to throttle 2. (correct)

    • What is the primary function of the pressure cap on the cooling system?

  • To store excess coolant.
  • To maintain the coolant temperature.
  • To prevent engine overheating.
  • To increase the boiling point of the cooling water. (correct)

    • Which oil system is responsible for cooling the piston?

  • Scavenging oil system
  • Soak Back or turbo lube system
  • Piston cooling oil system (correct)
  • Main lubricating oil system

    • What occurs when the oil filter becomes clogged and the pressure difference reaches 40 PSI?

    <p>The bypass valve delivers lube oil directly to the engine.</p> Signup and view all the answers

    What effect does pressurization have on the cooling system?

    <p>It allows for higher engine operating temperatures.</p> Signup and view all the answers

    Which component indicates the reason for engine speed increase when the water temperature is low?

    <p>EM 2000 computer monitor</p> Signup and view all the answers

    What type of pump is the scavenging oil pump?

    <p>Positive displacement, gear type pump</p> Signup and view all the answers

    What prevents damage to the cooling system components by relieving excessive pressure?

    <p>Pressure cap</p> Signup and view all the answers

    What role does the diffuser play in the turbine section of the turbo?

    <p>It provides a smooth transition path for gas flow.</p> Signup and view all the answers

    Which component receives drive from the engine during low-speed operations?

    <p>Sun-gear shaft</p> Signup and view all the answers

    How does the inertial air inlet filter operate to clean the air?

    <p>It uses centrifugal force to separate dirt from the air.</p> Signup and view all the answers

    What is the purpose of the aspirator tube in the exhaust ducts?

    <p>To maintain vacuum in the engine crankcase.</p> Signup and view all the answers

    What converts heat energy from exhaust gases into mechanical motion in the turbocharger?

    <p>Turbine wheel blades</p> Signup and view all the answers

    What is the primary function of the impeller in the turbocharger assembly?

    <p>To induce a partial vacuum in the air inlet casing.</p> Signup and view all the answers

    What happens to the dirt particles collected by the inertial air inlet filter?

    <p>They are transported to a dustbin by a blower.</p> Signup and view all the answers

    How do exhaust gases reach the turbine in the turbocharger system?

    <p>By passing through a fixed nozzle ring.</p> Signup and view all the answers

    What is the maximum oil pressure controlled by the relief valve in the main lubricating oil system?

    <p>125 PSI</p> Signup and view all the answers

    Which component is primarily responsible for delivering oil to the piston cooling oil manifolds?

    <p>Piston cooling oil pump</p> Signup and view all the answers

    What function does the stream of oil directed to the underside of the piston crown serve?

    <p>Cooling and lubrication</p> Signup and view all the answers

    How does oil from the main oil manifold reach the connecting rod bearings?

    <p>Through drilled passage in the crankshaft</p> Signup and view all the answers

    What is located above the crankshaft to distribute oil throughout the engine?

    <p>Main oil manifold</p> Signup and view all the answers

    What happens to oil after it cools and lubricates the piston cooling system components?

    <p>It drains back into the oil sump</p> Signup and view all the answers

    Which component receives oil to lubricate the hydraulic lash adjusters?

    <p>Rocker arm shaft</p> Signup and view all the answers

    What is the role of the fine mesh strainer elements in the lube oil system?

    <p>To filter impurities from the oil</p> Signup and view all the answers

    What is the primary function of the fuel oil system in locomotives?

    <p>To supply fuel to the engine in the correct quantity and at the right time.</p> Signup and view all the answers

    What role does the suction strainer play in the fuel feed system?

    <p>It separates foreign particles from the fuel oil to protect the fuel pump.</p> Signup and view all the answers

    At what PSI does the primary filter's by-pass valve open?

    <p>30 PSI</p> Signup and view all the answers

    What happens when the secondary fuel filter's pressure difference reaches 60 PSI?

    <p>The filter's by-pass valve opens and diverts fuel back to the fuel tank.</p> Signup and view all the answers

    What is the purpose of the fuel supply manifold in the fuel oil system?

    <p>To distribute fuel oil to all unit injectors.</p> Signup and view all the answers

    How does the governor affect the fuel injection process in the engine?

    <p>It adjusts the quantity of fuel injected into the engine.</p> Signup and view all the answers

    What indicates a problem with the primary fuel filter?

    <p>A flow of by-pass fuel in the sight glass.</p> Signup and view all the answers

    What is the pressure at which the regulating valve for the fuel supply manifolds is set?

    <p>10 PSI</p> Signup and view all the answers

    What is the primary purpose of the dust bin blower in the air filter system?

    <p>To increase the efficiency of the filters by enhancing air velocity.</p> Signup and view all the answers

    What is the efficiency level of the inertial air filters at throttle 8th?

    <p>90%</p> Signup and view all the answers

    What material are the secondary engine air filters made of?

    <p>Fiberglass</p> Signup and view all the answers

    What does the aftercooler do for the compressed air in the engine?

    <p>Increases the density of the air.</p> Signup and view all the answers

    Which model is used for the air compressor in GM locomotives?

    <p>WLNA9BB</p> Signup and view all the answers

    How many cylinders does the WLNA9BB air compressor have?

    <p>Three cylinders, two low-pressure and one high-pressure.</p> Signup and view all the answers

    What is the purpose of the intercooler in the compressed air system?

    <p>To reduce the temperature of the compressed air.</p> Signup and view all the answers

    During normal operation, what should the oil pressure in the compressor typically be?

    <p>18-25 psi</p> Signup and view all the answers

    Study Notes

    Two-Stroke Engine Efficiency

    • Two-stroke engines have twice as many combustion events per revolution as four-stroke engines.
    • Diesel two-stroke engines are more efficient than gasoline two-stroke engines.

    Fuel oil system

    • Draws fuel from fuel tank, filters it, pressurizes it, and injects it into the engine in the correct quantity.
    • Consists of fuel feed system and fuel injection system.
    • Fuel feed system
      • Draws fuel from the fuel oil tank through a suction strainer.
      • The strainer separates foreign particles from the fuel oil.
      • Fuel is then pumped to a primary filter with a 30-PSI bypass valve and sight glass.
      • The bypass valve opens if the primary filter is clogged, allowing fuel directly to the system.
      • Fuel then passes to 02 engine-mounted secondary filters which are of spin-on type.
      • Secondary filters also have a bypass valve set at 60 PSI.
      • When the pressure difference across the secondary filters reaches 60 PSI, the bypass valve opens and diverts fuel back to the fuel tank.
      • A bypass sight glass indicates if the secondary filters are clogged.
      • Fuel oil is supplied to the unit injectors through fuel supply manifolds.
      • The governor controls the amount of fuel injected into the engine.
    • Fuel injection system
      • A regulating valve with a sight glass, set at 10 PSI, is located at the end of the fuel supply manifolds.
      • This valve helps reduce engine speed and load up to the 6th notch until the temperature returns to a safe limit.
      • Engine speed will be raised to throttle 2 automatically if the engine water temperature is below 115°F (46°C).
      • Engine speed will be reduced to IDLE once the engine water temperature reaches above 125°F (52°C).

    Cooling System

    • The cooling system is pressurized to raise the boiling point of the cooling water.
    • A pressure cap, located on the water tank filling pipe, opens at approximately 20 PSI to relieve excessive pressure.
    • This helps prevent damage to the cooling system components.

    Lube Oil System

    • The complete engine lubricating system consists of four separate systems:
      • Scavenging oil system
      • Main lubricating oil system
      • Piston cooling oil system
      • Soak back or turbo lube system
    • Scavenging oil system
      • Uses a positive displacement, helical gear type pump.
      • Draws lube oil from the engine oil sump and the oil strainer.
      • Delivers lube oil to the lube oil filter tank (also called Michiana oil filter).
      • Oil from the filter tank goes to the lube oil cooler where it is cooled by the engine cooling system.
      • Oil then passes to the lube oil strainer where it is filtered again.
      • The oil filter contains five paper-type filter elements.
      • A bypass valve across the filter tank, set at 40 PSI, delivers lube oil directly to the cooler if the filter is clogged.
      • The oil filter and lube oil cooler are located in the equipment rake.
      • The lube oil strainer has two fine-mesh strainer elements.
    • Main lubricating oil system
      • Supplies pressurized oil to most of the engine's moving parts.
      • Takes oil from the strainer housing through a common suction.
      • Oil from the pump goes to the main oil manifold which is located above the crankshaft.
      • Maximum oil pressure is controlled by a relief valve set at 125 PSI.
      • Oil from the manifold enters the gear train at the rear end of the engine.
      • Oil enters the hollow bore camshaft from the camshaft stub shafts.
      • Radial holes in the camshafts distribute oil to each camshaft bearing.
      • An oil line from each camshaft bearing supplies oil to the rocker arm shaft, rocker arm cam follower assemblies, hydraulic lash adjusters, and rocker arm.
    • Piston cooling oil system
      • Receives oil from a common suction pipe.
      • Delivers oil to the piston cooling oil manifolds extending the full length of the engine.
      • A piston cooling oil pipe at each cylinder directs a stream of oil to the piston crown.
      • Some oil enters oil grooves in the piston pin bearing for lubrication.
    • Soak back or turbo lube system
      • Turbo charger components:
        • Sun-gear shaft: Receives drive from the engine through the planet gear system and a clutch at low speeds.
        • Exhaust gas driven turbine: The burnt exhaust gases are directed to a fixed nozzle ring between the exhaust manifold and turbine, then to the turbine wheel blades. Heat energy is converted into mechanical rotary motion.
        • Diffuser: A device located in the turbine section, it provides a smooth transition path for the gas flow, eliminating turbulence.
        • Impeller with diffuser: An impeller (compressor) with a diffuser ring draws air from the clean air room. The impeller compresses the air.
    • Inertial Air Intake Filter: Cyclonic type with many filter tubes mounted in a single assembly. Dirt particles are thrown to the outer wall of the tube by centrifugal force and then collected.
    • Baggie Type Air Intake Filter: Provides a secondary stage of filtration for air contaminants not captured by the inertial filter. Made of oil-coated fiberglass material.
    • Aftercooler: Cools the compressed air before entering the air box using its heat exchange capacity. This increases the air density, providing more optimal conditions for combustion.
    • Compressed Air System
      • Used for the locomotive brake system and auxiliary systems such as sanders, bell, horn, windshield wipers, rail lube systems, and radar head air cleaner.
      • Uses a WLNA9BB model three-cylinder air compressor.
      • The compressor is water-cooled.
      • Air is compressed by two low-pressure cylinders, cooled by an intercooler, and then compressed to main reservoir pressure by a high-pressure cylinder.
      • The compressor has its own internal oil pump, pressure lubricating system, and oil filter.

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    Description

    Explore the unique characteristics of two-stroke engine efficiency compared to four-stroke engines. This quiz covers the fuel oil system, including the fuel feed and injection systems, and their functions in ensuring optimal engine performance.

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