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AGM 241 Compact Diesel Engines Introduction to Diesel Engines

Engine Familiarization. Block DesignTunnel BlockAdvantagesMore resistant to internal forcesBlock ribbing is added for strengthreduced engine noiseCrankshaftInstalled from the rearUses a solid front bearing, special middle bearings, and the rear bearing case also holds the thrust bearings and

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AGM 241 Compact Diesel Engines Introduction to Diesel Engines

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    2. Engine Familiarization Block Design Tunnel Block Advantages More resistant to internal forces Block ribbing is added for strength reduced engine noise Crankshaft Installed from the rear Uses a solid front bearing, special middle bearings, and the rear bearing case also holds the thrust bearings and rear seal

    3. Cylinder head The cylinder head is a cross flow type The inlet and exhaust ports are on opposite sides. Prevents intake air being heated by exhaust air. Has a higher power output due to the cool dense air. Reduced chance of head distortion

    4. Typical Fuel System Diesel engines use a high pressure fuel delivery system that pressurizes, delivers, and atomizes the fuel.

    5. Direct Injection vs Indirect Injection Direct Injection Injects fuel directly into the compression area above the piston. Advantages Higher fuel efficiency Easier cold starting Disadvantages Lower RPM applications Higher noise Higher emissions

    6. Direct Injection vs Indirect Injection Indirect Injection Fuel is injected into a pre-combustion chamber that is connected to the main chamber by a narrow passage. Advantages High RPM Lower emissions Lower noise Disadvantages Requires pre-heat for cold start Higher compression ratios lower fuel efficiency

    7. Glow Plug Starting Aid Cold starting is is achieved with the glow plug system. When activated the glow plug tip gets red hot heating the air in the pre-combustion chamber. This helps the engine ignite the fuel during starting.

    8. Kubota Model Designations For specific definitions see the owners/workshop manuals.

    9. Principals of Operation Engines are devices that transform chemical energy into mechanical energy. They do this through a series of necessary steps called cycles. Every internal combustion engine performs the same cycles but varying designs perform these events in different ways. The most common are the two stoke and four stroke cycle engines. The four cycles are always performed in the same order.

    10. Four cycle engine Intake stroke The intake valve is open The exhaust valve is closed The piston travels from TDC to BDC causing a vacuum in the combustion chamber. A charge of air then enters the combustion chamber.

    11. Four cycle engine Compression stroke Both valves are closed. The piston is moving from BDC to TDC The trapped intake air is compressed. This compression causes a tremendous amount of heat. At the end of the compression stroke and slightly before TDC the injector fires a fuel charge that is ignited by this super heated air starting the power stroke.

    12. Four cycle engine Power Stroke The expansion of the burning gasses pushes the piston from TDC to BDC with great force. Both valves remain closed until BDC.

    13. Four cycle engine Exhaust stroke The exhaust valve opens and all cylinder pressure is lost. The intake valve remains closed. The piston moves from BDC to TDC. As the piston does this it pushes the burnt gasses past the exhaust valve and out the exhaust port. When the piston reaches TDC the exhaust valve closes the intake valve opens and the cycle begins again.

    14. Two cycle engine A two stroke engine performs the same four cycles but does it in one revolution of the crankshaft as opposed to the four strokes two revolutions. Two strokes therefore produce a power stroke on each crankshaft revolution.

    15. Two cycle engine Intake and exhaust The intake stroke occurs when the piston uncovers the intake port (no valve). At the same time the exhaust valve is open. This causes a low pressure in the combustion chamber drawing in the fresh air charge.

    16. Two cycle engine Compression stroke As the piston begins to move from BDC to TDC the exhaust valves closes, the piston covers the intake port, and the air charge is compressed.

    17. Two cycle engine Power stroke At TDC the injector fires igniting fuel in the heated intake air forcing the piston towards BDC. The power stroke occurs as the piston travels from TDC to BDC and until the exhaust valve opens Once the exhaust valve opens the cycle begins again.

    18. Horsepower & Torque Horsepower was developed by James Watt to compare the power produced by a steam engine with the power of a horse. The horse power is a measurement of the ability to do work. 1 HP = 33,000lbs - one foot - in one minute.

    19. Horsepower Ratings Gross Horsepower Total engine output with no accessories or restrictions. Normally theoretical and not measured. Brake Horsepower Measurement of actual usable horsepower delivered to crankshaft. Indicated Horsepower Power of the gasses transmitted to the pistons. Mathematically calculated. Mechanical efficiency The difference between indicated horsepower and brake horsepower. Typical Mechanical efficiency is between 80% - 90%.

    20. Torque Torque a rotational force around a fixed point. Calculated by multiplying the applied force by the distance from the centerline of rotation. Measured in Pound Feet Only as much torque as needed will be applied to an object. Any remaining force will only increase the speed of the object.

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