Diesel engine: pros and cons.

[TAKTCOM]

Theoretically, a diesel engine is a good alternative to a turbine. It is cheaper and spends less fuel, which is useful for long-range raiders. That sounds pretty interesting, is not it. But here we come to the game and what do we see? Well... 

Suddenly, using a diesel engine is more expensive than turbines. Also, the weight of the engine plus the weight of the fuel is also not in favor of the diesel engine. As if this were not enough, diesel engines are at the end of the technologies list. This is 1931-1935! Radars, the top FCS, as well as 18-inch guns and Yamato-style hulls open earlier than diesel engines. And the diesel still worse than the basic turbine, available since 1906.

Well, maybe diesel engines have some really value on tactics? Let's get a look.

This reduced chance of critical damage and faster repair looks really good! Well, until you remember that the main reason for the failure of the engine in the game is not damage to the shells.

This is flooding. 

Summing up all that is written above, at the moment, diesel engines look frankly unnecessary. What do you think about diesel engines?

[arkhangelsk]

I never used them. Maybe the campaign will give me a reason to, but basically unless you want to handicap yourself in these scenarios ... nope.

[Masonator]

Some theories I have on them:

 

1. The reduced weight for Operational Range, Fuel, etc. is the way the devs have chosen to model their reduced fuel consumption - in that they actually consume the same amount of fuel, but the diesel fuel simply weighs less and affects your stability to a lesser degree. Not the most accurate way to model it, but it works.

 

2. In the current build of the game, fuel consumption isn't modeled at all - both in the Naval Academy and Custom Battles. I'm positive they'll have a much greater effect in the campaign, where the reduced fuel consumption relative to turbines will offset their added weight.

 

3. Diesels definitely aren't lighter than turbines. Cheaper, less complex, and easier on fuel - absolutely. But lighter? Definitely not. I'm a naval Marine Engineer IRL and one of our gas turbines only weighs about 2/3rds as much as our propulsion diesel - which we can see is modeled accurately in the game. Diesels also produce significantly less power than a turbine (the price you pay for the fuel economy and simplicity), meaning you need a lot more engine to pull the same amount of power out of them that you'd get with a much smaller turbine.

 

I wish UA:D would let us build ships with hybrid propulsion, such as CODOG/COSOD setups where the ship has diesel engines for cruising and turbines for action. Regardless, hope this clarifies something. They still need some work, but they're not completely useless - I'm sure they'll be monsters in the campaign, which is why they're your last unlock.

[TAKTCOM]

This is a good point, mr.Masonator. But in the game everything works differently. For example

On 4/5/2020 at 11:53 PM, Masonator said:

 I'm positive they'll have a much greater effect in the campaign, where the reduced fuel consumption relative to turbines will offset their added weight.

This is not happening. Because the latest diesel engine weighs (with fuel) more than the earliest turbine (with fuel).See the picture below.

On 4/5/2020 at 11:53 PM, Masonator said:

3. Diesels definitely aren't lighter than turbines. Cheaper, less complex, and easier on fuel - absolutely. But lighter? Definitely not.

The question is that the turbine mk.1 is 1906, and the diesel mk.2 is 1935. 29 years of difference and an earlier engine is still better.

On 4/5/2020 at 11:53 PM, Masonator said:

I wish UA:D would let us build ships with hybrid propulsion, such as CODOG/COSOD setups where the ship has diesel engines for cruising and turbines for action. 

t would not be nice, but I doubt it. Because the game is even relatively ordinary turboelectric drive be in auxiliary modules, not in engines.

Edited April 7, 2020 by TAKTCOM

[Masonator]

On 4/7/2020 at 3:35 AM, TAKTCOM said:

This is not happening. Because the latest diesel engine weighs (with fuel) more than the earliest turbine (with fuel).See the picture below.

It weighs more because your speed is set to the same as it would be with turbines installed, meaning you're effectively installing a MUCH heavier engine for the same amount of power. This is why your total displacement is increasing when choosing Diesel II.

As I stated earlier, this is because diesels have a significantly worse power-to-weight (P:W) ratio than turbines. For example, a diesel producing 8,800shp is only sufficient to drive a 5,100t warship at 18 kts at maximum load, while a turbine that weighs significantly less than the diesel produces ~23,500shp and can propel the same ship at 26 kts at full power, and even faster with safety restrictions lifted. If you lower your selected max speed setting from 27 kts to ~15 kts, you'll find the diesel is much more efficient at that speed. Maximum speed is the price you pay for the simplicity and massively reduced fuel consumption.

 

On 4/7/2020 at 3:35 AM, TAKTCOM said:

t would not be nice, but I doubt it. Because the game is even relatively ordinary turboelectric drive be in auxiliary modules, not in engines.

They're listed under auxiliaries because a TED is a small, auxiliary engine (driven either by exhaust gases from the propulsion turbines, or less-commonly with its own steam supply), coupled to an AC generator in order to supply electrical power. On older ships, such as those during the period represented in UA:D, they were driven by smaller, auxiliary steam turbines. On modern ships, these are almost universally driven by diesel engines. It's not a propulsion engine, it's a generator set - hence why it's listed under Auxiliaries.

Adding hybrid propulsion as I've suggested would require a rework of the current Engine selections, splitting them into two separate categories - Cruise Engines and Sprint Engines. Aboard most modern warships, diesels are your cruise engines - you trade slower speeds for the massive increases in operational range offered by the diesel's reduced fuel consumption. Modern warships only use their turbines as sprint engines, which are used where operational concerns (such as combat, tight maneuvering, higher speed requirement, etc) offset their huge fuel draw.

tl;dr diesels let you go farther but slower, whereas turbines limit your range but let you get there faster.

[disc]

It would be good to see direct comparisons between commercial Diesel and turbine ships of the era.

On Yamato, the propulsion plant was to be a split Diesel / turbine setup, with each driving two of the four shafts. The turbines would make 75000 hp and the eight Diesels 60000 hp. However, it was decided during design that the Diesels would be too unreliable and an all turbine setup was therefore better. This caused a rapid redesign. The boilers and uptakes were doubled, and the funnel arrangement and superstructure changed. Waterline length was increased from 253m to 256m, and the trial displacement rose from about 65200 tonnes to 68200 tonnes. The engine power was increased from 135000 hp to 150000 hp. The speed was unchanged because of the increase in weight and only slight increase in length. Machinery weight decreased from 5430 tonnes to 5043, but fuel weight shot up from 2961 to 4330 tonnes in order to keep the same range. There was a decrease in lubricating oil required, but also an increase in feedwater needed. So in sum the all-turbine setup was not especially preferable, except to increase reliability. An addendum is that the boilers and turbines were effectively derated from destroyer equivalents in an attempt to ensure reliability.

[Hardlec]

The technical superiority of the diesel, as I understand it, is that Steam engines are vastly more efficient, easier to build and easier to operate.  The problem is their fuel.  Hot Steam is the fuel of a steam engine, the hotter the better.  To use a steam engine, you must carry with you a way to make fuel.  This is usually done by burning something, like coal, and using that heat to vaporize water.  Steam gets hotter if it's under more pressure.  The extra reinforcement needed to handle this pressure means more weight in the "fuel refinement plant" aka the boiler.  While the energy losses of the hot steam in the engine, i.e. potential energy of the steam versus actual output in power anr small, the energy losses of the fuel burned to heat water are enormous.  
When you have a nuclear kettle providing vast amounts of heat very efficiently, that heat can be used to generate steam, and the steam engine becomes the most wonderful engine there is.
A diesel engine can use diesel fuel, already refined.  It's the more efficient fuel, not the more efficient engine, that rules the day here.

[Norbert Sattler]

It would be nice if the mouse-over stats showed the weigh per knot rather than the weight per horse power.

Right now the text reads as if Diesel are lighter than Turbine for the same speed, when the opposite is the case.

[traeng]

On 5/19/2020 at 9:32 PM, Hardlec said:

The technical superiority of the diesel, as I understand it, is that Steam engines are vastly more efficient, easier to build and easier to operate.  The problem is their fuel.  Hot Steam is the fuel of a steam engine, the hotter the better.  To use a steam engine, you must carry with you a way to make fuel.  This is usually done by burning something, like coal, and using that heat to vaporize water.  Steam gets hotter if it's under more pressure.  The extra reinforcement needed to handle this pressure means more weight in the "fuel refinement plant" aka the boiler.  While the energy losses of the hot steam in the engine, i.e. potential energy of the steam versus actual output in power anr small, the energy losses of the fuel burned to heat water are enormous.  
When you have a nuclear kettle providing vast amounts of heat very efficiently, that heat can be used to generate steam, and the steam engine becomes the most wonderful engine there is.
A diesel engine can use diesel fuel, already refined.  It's the more efficient fuel, not the more efficient engine, that rules the day here.

However, steam engines can run on any type of fuel they see.

Especially, coal. I love coal.

Coal can be used as a really nice armor.

[Rancor]

On 4/11/2020 at 7:40 PM, Masonator said:

They're listed under auxiliaries because a TED is a small, auxiliary engine (driven either by exhaust gases from the propulsion turbines, or less-commonly with its own steam supply), coupled to an AC generator in order to supply electrical power. On older ships, such as those during the period represented in UA:D, they were driven by smaller, auxiliary steam turbines. On modern ships, these are almost universally driven by diesel engines. It's not a propulsion engine, it's a generator set - hence why it's listed under Auxiliaries.

I would have to disagree with you on that one Masonator.

In this time period I would argue that 'Turbo Electric Drive' should refer to such a setup for the main engines, such as was used in the Colorado class of battleships. As such it should be listed under main engines.

My interpretation of the way the game handles 'auxiliary engines' is they are what we would today call emergency generators. In game the primary electical plant is included with the 'main engines' and fails if the main engines are knocked out. The auxiliary engine(s) is located in a different part of the ship and can continue to provide electrical power for critical systems while the main plant is offline.

I would love to see an extra layer of complexity regarding machinery modeled in game but I might make a seperate thread for that.

 

 

 

[TAKTCOM]

The topic is probably out of date. Since it was created before

Alpha-6

• Diesel engines rebalanced to reflect better their bonuses. Diesel engines will be more important in campaign, but now can be useful in missions too, offering more reliable and cost-effective power plants.

[RUSS663]

On 6/7/2020 at 11:41 PM, Rancor said:

My interpretation of the way the game handles 'auxiliary engines' is they are what we would today call emergency generators. In game the primary electical plant is included with the 'main engines' and fails if the main engines are knocked out. The auxiliary engine(s) is located in a different part of the ship and can continue to provide electrical power for critical systems while the main plant is offline.

Yes, I agree.  The AUX enable pumping, steering and turret operation.

Russ663

[Evil4Zerggin]

Came back to this game briefly in Alpha 9 after not playing since Alpha 4. Here's my review of the current state of engines:

• Basic Steam Engine has widened its cost-effectiveness advantage, offering ~3x the HP / cost of turbines. Ironically, this disproportionately favors its use on destroyers, which a) tend to have most of their cost in the engines and b) have a high shapeExpSpeed of 4, which means that their speed is less affected by hp / ton. Losing access to cheap reciprocating engines is a serious loss economically.
  • You do lose the cost advantage if use oil or you take any of the auxiliary / shaft components, since Basic Steam Engine is proportionately more affected by other cost increases. But those components are pretty marginal to begin with even in the best case.
• Triple/Multiple Expansion engines are still bad. They don't produce nearly enough more hp / ton to offset their much higher cost.
• Geared Turbines is now clearly better than standard Turbines, offering much better hp / ton at nearly the same cost. Geared Turbines II vs I is debatable.
• Diesel is like a consolation prize for losing Basic Steam Engine, but still a viable cost-saving measure.

[Commander Reed]

It seems the Geared Turbines are better if you want more manoeuvrability and overall engine efficiency, the diesel engines seem to be better at aiding repairs and are overall sturdier. I like both. 

Edited March 1, 2021 by Commander-Alexander-Reed