How a Ship Engine Works - 2-Stroke Marine Diesel Engine

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00:00How a ship engine works.

00:03We're looking at a two-stroke marine diesel engine which runs massive cargo ships across oceans.

00:11It's called a two-stroke engine because it completes a full power cycle in just two piston strokes.

00:19First, after combustion occurs, the piston is forced downward, that's the first stroke.

00:26Then, the piston moves back up, compressing air, that's the second stroke.

00:33Combustion happens again.

00:36Each time the piston goes down and back up, the crankshaft completes one full revolution.

00:43Unlike car engines that operate at thousands of RPM, large ship engines are incredibly slow.

00:50They typically run between 60 to 120 RPM and rarely above 200 RPM.

00:57Pretty slow, right?

00:58These engines are not built to be fast and furious.

01:01They are built to be steady and strong.

01:05Bringing the car engine down to its true size, we can compare and see how massive the ship engine is.

01:12The engine you see here stands 42 feet tall.

01:18That's roughly the height of a 4-story building.

01:25Let's break it down.

01:27This is an engine cylinder.

01:29Inside is a piston.

01:31Piston rod.

01:33Connected to the connecting rod or con rod.

01:36This is the cross head, which guides the piston's motion in a linear direction along the rails.

01:43The crankshaft.

01:46This engine model has 6 cylinders, but the largest engine can have 14 cylinders.

01:53To start the engine, combustion doesn't happen right away.

01:57Instead, the engine uses starting air from the starting air valve, a highly compressed air that's blown into the cylinder.

02:06This blast of air pushes the piston downward to begin rotation.

02:15The piston itself travels about 8 feet from top dead center to bottom dead center.

02:21Fresh air is drawn in through these side openings called scavenged ports.

02:27As the air is compressed, its temperature rises sharply, reaching above 900 degrees Fahrenheit, hot enough to ignite fuel.

02:37At the right moment, fuel is injected into the combustion chamber as a fine mist.

02:43Combustion begins.

02:46After combustion, the cylinder is filled with hot, burnt exhaust gas.

02:56Fresh, oxygen-rich air is drawn in and pushes the exhaust gas out through the exhaust valve.

03:04The exhaust gas exits the engine and passes through a scrubber system, which reduces pollution before it is released into the atmosphere.

03:16This is the exhaust gas manifold.

03:22The turbocharger.

03:24The air cooler.

03:26And the charging air manifold.

03:28And the charging air manifold.

03:30A turbocharger has two sides, a turbine and a compressor.

03:35On the turbine side, hot exhaust gas spins the turbine wheel.

03:41That spinning motion powers the compressor side, which draws in fresh air from the inside of the engine room, through the air filter.

03:49Fresh air is continuously drawn from outside of the ship into the engine room.

04:02The air is compressed, which makes it hot, so it passes through an air cooler filled with water-cooled tubes, reducing its temperature to around 140 degrees Fahrenheit.

04:15Next, the air flows through a mist catcher, which removes water droplets to prevent corrosion.

04:22This cool, clean air enters the charging air manifold, ready to flow into the cylinder when the scavenged ports open.

04:30And the cycle of replacing exhaust gas with fresh air repeats.

04:36These are cooling water, constantly flowing to absorb the heat and cool down these cylinders.

04:48On the exhaust valve stem, there is a rotator.

04:51Each time the valve opens and the exhaust gas passes through, it rotates the valve a little.

04:58The purpose is to maintain even wear on the valve disc every time it makes contact.

05:03The exhaust valve stays closed by default.

05:07This is the air piston.

05:10Below, it is a chamber filled with compressed air, known as the air spring.

05:14The air pressure pushes the piston upward to keep the valve closed.

05:19To open the valve, hydraulic oil is pumped in.

05:22Its pressure must be greater than the air springs to push the piston down and open the valve.

05:28When the oil drains, the air spring pushes the piston back up, closing the valve.

05:35There's a whole jungle of pipes and lines running across the ship engine.

05:40But let's just focus on the few of the main ones.

05:43These are the hydraulic oil line.

05:46And the fuel injection lines.

05:49There are also plenty more for cooling water, compressed air and loop.

05:57But we'll keep it simple for now.

05:59On the cylinder head, we have the fuel injectors and the starting air valve.

06:04Some hybrid engines also have LNG injectors.

06:19Each cylinder has a hydraulic cylinder unit.

06:23It includes a fuel booster that raises fuel pressure for injection.

06:27and an exhaust valve actuator to control hydraulic oil flow.

06:36This whole unit is managed by an electronic control system or ECS.

06:42It precisely controls fuel and hydraulic oil's timing to match the piston's motion.

06:48Before ECS, engines used a mechanical camshaft to do the same job.

07:00The camshaft is driven by a chain gear connected to the crankshaft.

07:05Cam lobes are precisely shaped and timed to control the flow of hydraulic oil and fuel injection.

07:12They are positioned to match the exact timing of the piston's movement.

07:17Not all engines have an electronic control system.

07:20Many ships still use camshafts.

07:25To move the ship astern, the engine must be reversed.

07:29That means the crankshaft changes its direction of rotation.

07:33In large cargo ships with low speed engines, there's no gearbox.

07:38The propeller shaft is directly connected to the engine and spins with it.

07:43So before reversing, the engine must come to a complete stop.

07:51Then, starting air is sent to the cylinders.

07:54Beginning with the one that has its crank web on the opposite side.

07:59One cylinder at a time.

08:02The engine starts rotating in the reverse direction.

08:06Once rotation is established, the normal combustion cycle resumes just in the opposite direction.

08:15Now, the propeller turns astern and the ship begins moving backward.

08:21The engine is massive.

08:27So massive, it's built with a walking platform to allow crew members to access and service different parts.

08:35Inside the crankcase, the structure is supported by bed plates and A-frames, which form the backbone of the engine's frame.

08:54This is the stuffing box, a sealing component that prevents oil and gas from leaking between the scavenged space and the crankcase.

09:06Everything down here is slippery since it's all coated in lubricant.

09:11There are crankcase access doors and ladders that lead inside.

09:16Yes, people actually have to go in there for inspections.

09:20Entering the crankcase is a high-risk job and it requires a lot of safety procedures.

09:26On this side, there are explosion relief valves.

09:31This is a super important component.

09:34During operation, heat causes lubricant to vaporize and pressure can build up inside.

09:40If not released, the pressure could lead to a crankcase explosion.

09:45These valves are designed to release internal pressure but not letting outside air in.

09:53If an explosion occurs and pressure is drawn in, it can trigger a secondary, more powerful explosion.

10:04To prevent that, each valve is assembled with a spring and a flame arrester.

10:10When pressure gets too high, the valve opens briefly to release it.

10:19The flame arrester prevents any flame from escaping to the outside.

10:23Once pressure drops, the spring immediately closes the valve, sealing it again.

10:29At the very bottom of the crankcase is the oil sump, a reservoir where all the used lubricating oil is collected.

10:37From the sump, the oil is pumped out, cooled down, filtered and sent back into the engine for another cycle of lubrication.

10:46Lube flows through a network of lubrication lines, reaching every critical mechanical joint, making sure everything runs smoothly.

10:56At the start of this video, you saw this large wheel with gear teeth.

11:05This is the flywheel.

11:07Its job is to reduce vibration and help the crankshaft rotate smoothly by using its momentum and weight.

11:17Next to it is the turning gear.

11:24When the engine is shut down, the turning gear engages with the flywheel and slowly turns it.

11:30This slow rotation is used during maintenance and inspection, letting engineers carefully position the crankshaft.

11:38Of course, the turning gear must be disengaged before the engine starts or serious damage could happen.

11:48And don't confuse the turning gear with the steering gear.

11:51The steering gear controls the ship's rudder's direction, while the turning gear is simply for rotating the engine slowly when the engine is not operating.

12:00This marine diesel engine runs on heavy fuel oil.

12:05Despite the name, it's not the same as the diesel you find at the gas station.

12:09Large cargo ships use heavy fuel oil because it's much cheaper and provides high energy output compared to diesel.

12:17But heavy fuel oil is so thick and dense.

12:20Inside the fuel tank, heating coils warm the oil enough so it can be pumped out.

12:26Then it's heated again, this time to an even higher temperature.

12:31Only when it's hot enough, the fuel can be injected into the combustion chamber as a fine mist.

12:38The engine's cooling system uses water, circulating through the cylinders to absorb heat.

12:45This heated water flows to the heat exchanger where it cools down before returning to the engine.

12:52Sea water is pumped in through the sea chest, flowing through these tubes inside the heat exchanger.

13:04The cooling water flows around these tubes.

13:13The cooling water and sea water are completely separated, they never mix or touch each other.

13:18Heat transfers from the cooling water to the sea water through the walls of the tubes by conduction.

13:25The sea water then carries this heat away and it discharged back into the ocean.

13:31The engine runs at low speed but it can produce the power of 10 of thousands horsepower.

13:38That explains how the engine can run a fully loaded ship with hundreds of thousands tons date weight.

13:44The history of this massive two-stroke marine diesel engine traces back to Rudolf Diesel, a German inventor who invented the diesel engine in the 1890s.

13:56But it was Burmeister and Wayne later becoming Man B&W that turned into the giant engine we see in ships today.

14:05Thank you for watching. If you know anything more about this topic, please leave a comment below.

14:11My name is Lucius, I'll see you in the next video.

14:14I'll see you in the next video.