What is a Dual Fuel Engine.docx

**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...

**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.