Motors Exam Prep PDF

Motors Exam Prep 1. What is a dual fuel engine? 2. What are typical engine speeds for low, medium, and high-speed engines? 3. What are the typical strokes and bores for low, medium, and high-speed engines? 4. How is an engine numbered? 5. Describe a heat engine and provide an example. 6....

Motors Exam Prep 1. What is a dual fuel engine? 2. What are typical engine speeds for low, medium, and high-speed engines? 3. What are the typical strokes and bores for low, medium, and high-speed engines? 4. How is an engine numbered? 5. Describe a heat engine and provide an example. 6. What is the air standard cycle used in modern diesel engines? 7. Draw and define each stage in this cycle. 8. Describe the difference between indicated-power and brake-power. 9. What is a parasitic load? Provide examples. 10. What is a stoichiometric mixture? What are the ratios for various fuel grades? 11. In which two ways can a combustion engine be described? 12. Why can’t petrol be used in a “CI” engine? 13. Describe a 4-stroke engine cycle. 14. In a 4-stroke cycle, which stroke produces power? 15. How many revolutions of the crankshaft are there for every power stroke of a 4-stroke engine and how fast does the camshaft rotate? 16. How many revolutions of a crankshaft are there for every power stroke in a 2-stroke engine and how fast does the camshaft rotate? 17. Describe a 2-stroke engine cycle. 18. What is scavenging? 19. Describe each method of scavenging with their advantages and disadvantages. 20. What are the 4 most significant pollutants in engine emissions? 21. Describe the potential hazards of each. 22. Draw a cross-section diagram for a medium-speed engine. 23. Draw a cross-section diagram for a low-speed engine. 24. What is valve overlap and why do we have it? 25. Draw a timing diagram for a 4-stroke engine. 26. Draw a timing diagram for a 2-stroke engine. 27. List some of the key differences between 2 and 4-stroke engines. 28. Show by sketch how an engine is secured to the ship. 29. What is the purpose of a bedplate and how is one normally constructed? 30. What materials can chocks be made from? Provide advantages / disadvantages for each. 31. Why do we earth the bedplate to the hull? 32. What is a dry sump vs. a wet sump? Provide pros and cons for each. 33. What types of bearings are used in engines and why? 34. Describe the materials used for plain bearings and how they are typically constructed. 35. Why are plain bearings typically split in half? 36. On some conrods, a plain bearing will be larger on the bottom half than it is on the top. Why? 37. Draw a “marine palm”. 38. What are the advantages of a marine palm in some engine designs? 39. Draw an oblique conrod. 40. Why are oblique conrods used? 41. How is a conrod attached to a piston on a medium-speed engine? 42. What is the purpose of a piston skirt and what might be a consequence of not having one? 43. What is the function of a garter spring and where is it typically located on a piston? 44. List the different types of piston rings and state their functions. 45. What are the two types of cylinder liners and what are the advantages and characteristics of each? 46. What is the purpose of honing a liner and how is this normally achieved? 47. Looking at the medium-speed engine cylinder head on pg. 71, why are there 4 ports? 48. Why do we need timing marks on a camshaft drive? 49. Why do we have a valve bridge / yoke arrangement? 50. Identify the different arrangements in which valves may be opened and closed. 51. Why do inlet/exhaust valves use two springs? 52. How does a valve rotator work, why is it used and what type of fuel are they normally used with? 53. How does a modern low-speed engine differ from a medium-speed engine in construction? 54. What does a crosshead do? 55. How is a piston rod connected to a piston on a low-speed engine? 56. What is a stuffing box and what does it do? 57. What are the three construction methods for crankshafts? Describe each method. 58. Draw and label a fully-built and semi-built crankshaft. 59. What do witness marks indicate on a crankshaft? 60. Does a low-speed 2-stroke engine have oil control rings? Why? 61. Sketch the various ways piston ring ends can look. 62. Why are piston rings shaped in these ways? 63. Draw and label a low-speed engine exhaust valve. (pg. 125) 64. Describe the function of this valve. 65. Where are fuel injectors located on a low-speed engine? 66. What is the golden rule of vibration? 67. How does a leaf spring damper work? What type of vibration does it help limit? 68. How does a viscous damper work? 69. What is a moment compensator and how does it work? 70. What are first and second-order moments? 71. How fast do first moment counterweights rotate and where are they connected? 72. How fast do second-order moment counterweights rotate and where are they connected? 73. What is bracing and what are the two types? 74. What is critical vibration? 75. Describe BSR and how it is managed. 76. List the possible causes and consequences of excessive engine vibration. 77. What are the advantages of pressure charging an engine?  78. What are the two methods of pressure charging and how do they differ from each other? 79. What are the advantages and disadvantages of turbocharging? 80. How does the valve overlap differ between naturally aspirated and pressure charged engines? Why is this? 81. Which engines use pulse converters? Which engines use constant pressure? What is a Dual Fuel Engine? An engine that can operate on two different types of fuel, often diesel and gas. Typical Engine Speeds: Low-Speed: 100-300 RPM Medium-Speed: 300-1200 RPM High-Speed: 1200-3000 RPM+ Typical Strokes and Bores: Low-Speed: Long stroke, large bore Medium-Speed: Moderate stroke and bore High-Speed: Short stroke, small bore How is an Engine Numbered? Typically based on design, type, and size. E.g., manufacturer model codes. Describe a Heat Engine and Provide an Example: Converts heat into mechanical energy. Example: Internal combustion engine. Air Standard Cycle in Modern Diesel Engines: Often uses the Diesel cycle (constant pressure combustion). Draw and Define Each Stage in the Diesel Cycle: Intake, Compression, Power, Exhaust.  Indicated Power vs. Brake Power: Indicated Power: Power developed inside the engine cylinder. Brake Power: Actual power available at the engine shaft. Parasitic Load: Power consumed by engine components. Examples: Alternator, water pump. Stoichiometric Mixture: Ideal fuel-air ratio for complete combustion. E.g., Gasoline: 14.7:1, Diesel: 14.5:1. Two Ways to Describe a Combustion Engine: By its cycle (2-stroke or 4-stroke) or by its fuel type (gasoline or diesel). Why Petrol Can't Be Used in a CI Engine: CI (Compression Ignition) engines require diesel fuel for its high ignition temperature. Describe a 4-Stroke Engine Cycle: Intake, Compression, Power, Exhaust. Which Stroke Produces Power in a 4-Stroke Engine? The Power Stroke. Revolutions of Crankshaft per Power Stroke in a 4-Stroke Engine: 2 revolutions; Camshaft rotates at half the crankshaft speed. Revolutions of Crankshaft per Power Stroke in a 2-Stroke Engine: 1 revolution; Camshaft is not used. Describe a 2-Stroke Engine Cycle: Combines intake and compression into one stroke; power and exhaust into another. What is Scavenging? The process of removing exhaust gases and bringing in fresh air. Methods of Scavenging: Uniflow: Efficient, but complex.  Crossflow: Simpler, but less efficient. Loop Scavenging: Good performance, but complex. 4 Most Significant Pollutants in Engine Emissions: NOx, CO, HC, PM. Potential Hazards of Each Pollutant: NOx: Respiratory issues, smog. CO: Poisonous gas. HC: Contributes to smog. PM: Respiratory and health issues. Cross-Section Diagram for a Medium-Speed Engine: (Draw Diagram) Cross-Section Diagram for a Low-Speed Engine: (Draw Diagram) Valve Overlap: The period when both intake and exhaust valves are open. Enhances performance. Timing Diagram for a 4-Stroke Engine: (Draw Diagram) Timing Diagram for a 2-Stroke Engine: (Draw Diagram) Key Differences Between 2 and 4-Stroke Engines: 2-Stroke: Simpler, higher power-to-weight ratio. 4-Stroke: More efficient, complex. How is an Engine Secured to the Ship? (Show Sketch) Purpose of a Bedplate: Provides a stable foundation. Constructed from steel or cast iron. Materials for Chocks:  Rubber: Good damping, but wear over time. Metal: Durable, but noisy. Why Earth the Bedplate to the Hull: Reduces electrical noise and prevents corrosion. Dry Sump vs. Wet Sump: Dry Sump: Better oil control, more complex. Wet Sump: Simpler, can cause oil slosh. Types of Bearings Used in Engines: Plain Bearings: Simpler, good for high loads. Rolling-Element Bearings: Better for high-speed applications. Materials for Plain Bearings: Typically bronze or aluminum alloys. Constructed with a smooth surface. Why Plain Bearings are Split in Half: Easier to install and replace. Plain Bearing Larger on Bottom Half: Accommodates larger forces and better alignment. Marine Palm: (Draw Marine Palm) Advantages of a Marine Palm: Reduces vibration and ensures better alignment. Oblique Conrod: (Draw Oblique Conrod) Why Oblique Conrods are Used: Provides better load distribution and efficiency. Conrod Attachment to Piston in Medium-Speed Engine: (Describe Method)  Purpose of a Piston Skirt: Helps in maintaining piston alignment and reduces wear. Function of a Garter Spring: Keeps piston rings in place. Types of Piston Rings and Their Functions: Compression Rings: Seal combustion chamber. Oil Control Rings: Manage oil consumption. Types of Cylinder Liners: Wet Liners: Easier to replace. Dry Liners: Better cooling. Purpose of Honing a Liner: Creates a smooth surface for better ring sealing. Why 4 Ports on a Medium-Speed Engine Cylinder Head: Enhances airflow and efficiency. Purpose of Timing Marks on a Camshaft Drive: Ensures proper timing of valve operation. Purpose of Valve Bridge / Yoke Arrangement: Ensures even valve movement. Valve Opening and Closing Arrangements: Overhead Valve: Common in modern engines. Side Valve: Simpler design. Why Inlet/Exhaust Valves Use Two Springs: Ensures reliable valve seating and reduces valve bounce. How a Valve Rotator Works: Rotates the valve to ensure even wear; used with high-speed engines. Modern Low-Speed vs. Medium-Speed Engine Construction:  Low-Speed: Heavier, more robust. Medium-Speed: Lighter, more complex. Purpose of a Crosshead: Reduces piston loads and ensures smooth operation. Piston Rod Connection to Piston on Low-Speed Engine: (Describe Method) What is a Stuffing Box and Its Purpose: Seals around rotating shafts to prevent leakage. Three Construction Methods for Crankshafts: Forged: Strong, durable. Cast: Less expensive, less strong. Billet: High performance, expensive. Fully-Built and Semi-Built Crankshaft: (Draw and Label) Witness Marks on a Crankshaft: Indicate alignment and balance issues. Oil Control Rings in Low-Speed 2-Stroke Engines: Usually not needed due to different lubrication methods. Piston Ring End Shapes: (Sketch Various Shapes) Why Piston Rings Are Shaped This Way: To ensure proper sealing and reduce wear. Low-Speed Engine Exhaust Valve: (Draw and Label) Function of Exhaust Valve: Allows exhaust gases to exit the cylinder.  Location of Fuel Injectors on a Low-Speed Engine: Typically positioned for optimal fuel atomization. Golden Rule of Vibration: Balance is key to minimize vibration. Leaf Spring Damper: Reduces high-frequency vibrations. Viscous Damper: Uses fluid resistance to absorb vibrations. Moment Compensator: Balances forces to reduce engine vibrations. First and Second-Order Moments: First-Order: Forces from reciprocating masses. Second-Order: Forces from rotating masses. First Moment Counterweights: Rotate at crankshaft speed, connected to the crankshaft. Second-Order Moment Counterweights: Rotate at twice the crankshaft speed. Bracing Types: Diagonal: Provides lateral support. Cross-Bracing: Enhances rigidity. Critical Vibration: Vibration at the engine’s natural frequency causing damage. BSR (Buzz, Squeak, Rattle): Manage through design adjustments and isolators. Causes and Consequences of Excessive Vibration: Causes: Imbalance, misalignment. Consequences: Wear, failure.  Advantages of Pressure Charging: Increases power and efficiency. Methods of Pressure Charging: Turbocharging: Uses exhaust gases. Supercharging: Uses mechanical power. Advantages and Disadvantages of Turbocharging: Advantages: Increased power, efficiency. Disadvantages: Complexity, heat. Valve Overlap in Naturally Aspirated vs. Pressure Charged Engines: Pressure Charged: Less overlap due to higher intake pressure. Engines Using Pulse Converters vs. Constant Pressure: Pulse Converters: Used in turbocharged engines. Constant Pressure: Used in naturally aspirated engines.