Marine Internal Combustion Engines Overview

Marine Internal Combustion Engines

• Rudolf Diesel collaborated with Sulzer to create the first Sulzer diesel engine in 1898.
• Low-speed diesel engines range from 1500 to 100,000 kW of shaft power.
• These engines use heavy fuel oil (H.F.O.) and are two-stroke with a crosshead mechanism.
• Tankers, bulk carriers, and large container ships predominantly use these types of engines for propulsion.
• Engines are enormously large and remarkably high due to their crosshead construction.
• Engines can reach heights of 14 meters, lengths of 30 meters, and weigh 2300 tons.

Lubricating Oil Pipe (Sheathed Pipe)

• The lubricating oil pipe is a two-layered pipe.
• Curved lines represent the lubricating oil supply lines for the exhaust valves.
• Exhaust valves and valve casings exceed two meters in dimensions.
• Braided sheathing surrounds the pipes (similar to some home gas heaters).
• Sheathed pipe is a pipe covered by another layer of metal.

Sheathing (Safety Measure)

• Sheathing is implemented to safeguard the high-pressure pipe from leakage.
• Leakage from the high-pressure pipe connecting the valve lube oil pump and cylinder could lead to a fire hazard from hydraulic oil spraying onto the hot exhaust manifold.
• The high-pressure pipe is surrounded by a braided steel pipe, separating the two by a narrow gap.
• Sheathing acts as a crucial safety measure.

Failure Detection in High-Pressure (Sheathed) Pipe

• Defective Exhaust Valve Operation: Poor cylinder performance—measured by exhaust temperatures—can indicate an issue with the exhaust valve.
• Leaking Oil: Oil leaking between the high-pressure and braided pipes, often through small holes in the actuator pump body, can enter the cam box.

Exhaust Valve

• Exhaust valves have a cage structure resembling a birdcage.
• They have four studs that are hydraulically tightened using nuts.
• The cage is made of cast iron to withstand mechanical and thermal loads, although a detachable seat is sometimes employed.

Valve Cage

• Valve cages are uniquely designed for single exhaust valves located centrally within the cylinder cover.

Detachable Seat

• Detachable seats are typically made from molybdenum steel to resist thermal and corrosive environments.
• Detachable seats are easily machined once removed from the cage.

Exhaust Valve Cooling

• Valve cages are water-cooled as part of the engine's cooling system.
• Valve cooling water generally flows from the cylinder cover to the exhaust valve body via cooling bends.
• In certain instances, there's a direct connection between the cylinder cover's water space and the valve cage's seat region.

Exhaust Valve Seal/Bush

• A bronze bush (shown hatched) guides the valve spindle within the valve body.
• The seal prevents spindle wear and air leakage from the cylinder.

Exhaust Valve Spindle

• Nimonic is a high-strength, corrosion-resistant nickel-based alloy primarily used for valve spindles due to its resistance at elevated temperatures.
• Engine designs often utilize Nimonic for the entire valve, given the high loading.
• Material selection, such as choosing between Nimonic alloys, is important to maximize engine life when burning fuel with high levels of Sulphur, vanadium, or other damaging chemicals.

Exhaust Valve Rotator/Spinner/Rotating Mechanism

• Spinners prevent valve tilting, uneven forces, overheating, and accumulation of solidified exhaust slags on the valve's sealing surfaces.
• Spinners induce gentle grinding on sealing surfaces to effectively remove corrosive vanadium pentoxide slag.
• The even sealing action minimizes tilting and prevents uneven thermal stress.
• Valve rotation distributes uneven combustion forces more uniformly on the valve seat, preventing localized wear/tear.
• Spinning the valve also reduces the wear and tear on valve guides.

Exhaust Valve Hydraulic Cylinder

• A piston located atop the valve stem and spindle operates within a hydraulic cylinder connected to an oil pump via a sheathed high-pressure pipe.

Exhaust Valve Actuator/Oil Pump

• The camshaft-driven actuator pump delivers hydraulic oil to the valve cylinder during the piston's upward stroke.
• Oil returns to the pump cylinder during the piston's downward movement.
• A relief valve in the actuator pump body manages pressure to prevent over-pressurization of the system.
• Separate fuel and hydraulic-oil pumps are involved.

Exhaust Valve Air Spring Cylinder

• An air spring cylinder introduces positive force to ensure valve closure after the hydraulic opening force is removed; it is a supplementary valve closing mechanism.
• A piston fitted to the valve stem reciprocates within the cylinder, compressing air within during valve opening.
• Compressing air provides force to close the valve once the hydraulic force on the valve is deactivated.
• The air leakage and system pressure (5 bar) are regulated via a non-return valve to prevent backward air flow.
• The cylinder wall is lubricated by a controlled oil bleed from the hydraulic cylinder to limit wear on the seals.
• Oil mist, containing compressed air and small oil particles (less than 10 µm), is used to aid this process.

Exhaust Valve Air Spring Cylinder, Tell-tale

• A device called a Tell-tale provides a visual display of the air pressure within the exhaust valve cylinder to manage cylinder pressure; it is a visual indicator for cylinder pressure.
• Glass tubes filled with liquid visually indicate air pressure.
• Electronic indicators/digital readout can also track the air pressure, offering more precise measurements than liquid-based Tell-tales.

Exhaust Valve Air Spring Cylinder, Check Rod

• The check rod assists in confirming proper valve lifting and cyclical rotation.
• Located at the top of the casing, the spring-loaded check rod passes through a bush and contacts a groove in the main air piston.
• As the piston rises, it causes the check rod to lift, and this motion indicates that the valve is closing.
• Movement of the check rod also indicates the rotating motion of the valve. This motion further suggests the valve is correctly positioned for smooth operation closure.

Exhaust Valve Detailed Components

• A diagram displays various components, including hydraulic oil, actuator piston, air supply, and valve parts, depicting an exhaust valve's intricate layout.

Low Speed, 2-Stroke, Crosshead Turbocharged Engine

• This section outlines the components (crankcase bedplate, crankcase, A-frame, fuel/oil pumps, cylinder block, cylinder liners, cylinder covers, exhaust-gas manifold, scavenging-air manifold) of a low-speed, two-stroke, turbocharged marine engine.
• The presentation discusses the relative positioning of exhaust and scavenging manifolds.