Engine Hydrolocking, Airspace

[BrendaEM]

If the diesel engines were running and mist went into the air intake, mist could likely cause the engine to misfire and perhaps stall.

Anything more, might fill an engine cylinder, bending or breaking a connecting rod or wrist pin, damaging the main bearings, perhaps throwing the rod through the side of the engine. It is possible that a hydrlocked diesel might endure more than a gasoline fueled engine because diesel engines are built to have a higher compression ratio, which means that the parts that water would break--would be stronger in a diesel than a gas engine.

If the engine were off or idling, the water might only hydrolock the engine. Because water is almost uncompressible, it would need to be drained from the cylinder before the engine could even crank. I couldn't find the video, but one Vespa had lost a head-gasket, and was hydrolocked. When they pulled the plug, water sprayed from the cylinder on each stroke. Perhaps that was an additional reason why they put the cylinder valve on the u-boat diesels, to drain water from the engine.

It's conceivable that, if you lost a connecting rod, and it didn't go through the block, and you repaired it, the water would have to be drained from the remaining cylinders. I think that in Das Boot, I saw a main bearing, they were working on.

Also, if water got into the engine the oil would be foamy yellow sludge.

https://www.youtube.com/shorts/SqLpcffZHOU



https://www.youtube.com/watch?v=ElgLDRoMpmI



Not now, but at some point, it would be cool that if the sub is damaged, it will fill with water, sort of like this, until the sailors float, under the remaining airspace, to get the full late-war U-Boat submariner experience.



In game, I don't know what could be done to save a flooding sub. In the movies, there's always a valve that can be tightened. : )
I suppose that it's possible that bolts on flanges that had yielded to tension, could be replaced.

An interesting game dynamic: deciding to abandon the U-boat, which has happened.

[BrendaEM]

I was trying to find a chart of the percentage of diesel engine hydrolock survivability. I should think that some military somewhere has one.
Though, I did find an actual submarine diesel repair manual, showing the repair components well enough to model: https://maritime.org/doc/fleetsub/diesel/chap3.php
Oddly, it appears that some diesels had an extra inspection port that a main-bearing cap and connecting rod could be swapped.

As a thought experiment, it would seem that flooded engines offer some interesting game scenarios. None of this has to be modeled, but perhaps there could game-wise be...

Levels of water intrusion:

1. Mist (Near the water surface, mist enters the intake)
2. Sip (Single wave enters intake)
3. Gulp (Intake is submerged for more than an instant

Levels of engine RPM:

1. Idle
2. Running Slow
3. Running Fast

Yielding 5 levels of engine trouble:

1. Sputter in warning, giving visible smoke to alert enemy
2. Engine stall without damage, giving visible smoke. Water needs to be cleared (See below)
3. Engine has minor damage. It runs with rapping sound and decreased performance
4. Engine is damaged but can be repaired. Main bearing cap would be removed, if available, a new piston-connecting rod installed, taking an hour or so (each)
5. Engine is irreparably damaged. Connecting rod penetrates engine block. Remaining engine, or battery power only

If the engine is not running, the engine cylinders would fill with water, same as a minor stall.

Stall Repair:

1. Flame valves are opened
2. Engine is cranked spraying water out, which would be humorous, if not for the destroyers
3. Flame valves are closed
4. Engine starts

Minor Engine Damage Repair:

1. Engine runs with rapping sound and decreased performance.

Major Engine Damage Repair:

1. Main bearing cap is removed.
2. Piston, connecting-rod combo is taken from inventory or corner of the engine compartment
3. Old piston and connecting-rod is removed
4. New piston is installed, by wrenching at crankcase
5. Main bearing cap is reinstalled
6. (Same as above) Flame valves are opened
7. (Same as above) Engine is cranked spraying water out
8. (Same as above) Flame valves are closed
9. Engine starts

Unrepairable Engine Damage:

1. Engine cannot be repaired, connecting rod is shown penetrating the engine block
2. Remaining engine can be used, if available, giving half the speed and charging

The Resources, if shown:

1. Good piston-connecting rod model and texture. (I can make one if you need it.) This can just be an inventory thing that sits somewhere in the engine compartment
2. Bad piston-connecting rod model and texture, same but bent connecting rod, which would be easier than a two-piece thing. This resource would also be toggled for engine failure, showing it penetrating crankcase.
3. Main bearing cap with bolts still sticking out of it model and texture. (I can make it if you need it.)
4. Water-spray particle-effect animation for the engine port. Perhaps I can make it, maybe.
5. (Extra) a wrench or socket-wrench model, for a submariner repair animation. A submariner would sit at the engine wrenching at the bottom of the crankcase
6. (Extra) damaged engine rapping sound. I could mix this in.

Going really far: In the long term, the crankcase oil needs to be changed, or engine degrades over time, for a campaign of something.
Perhaps it might be possible to damage an engine and it still run, with a rapping sound.

[Onkel Neal]

and that's why the air intake on a U-boat has an air gap between the intake manifold and the air induction.

Now, let's see a video of what happens when the exhaust line is flooded with 20meters pressure water!

.

[Onkel Neal]

Also, great analysis of the whole water/diesel thing.

[BrendaEM]

(Thank you @Onkel Neal)

I did a little looking, and I found a video showing an original U-Boat U-505 piston, with text stating that, yes they did carry spares, and they could be swapped at sea.

I haven't got a good look at a U-Boat engine, on it's own, but I've noticed that some diesels have a squarish access panel just above oil sump, which would be my guess as to how they got the piston and connecting rod out, as pulling a oil pan on any engine quite a feat.

You can stop the video here and there to read the text. I am not sure of the size, but if I knew the piston diameter, the rest would be easy. Well, it could be resized later, as long as it's in scale. In the video the some rings appear missing.

[BrendaEM]

Wow, that's big! And a mere 1,100 lbs!
"From top of the piston to the bottom of the connection rod that is one and one half [1 1/2] meters. "
It looks like the piston on the photo above is about 10" in diameter.

https://www.pinterest.com/pin/a-big-...9628502868161/

And there it is, though missing the (piston) rings:




Notice that the big-end bolts are on the top. That is how they could take it apart without dropping the pan.