Real Hybrid

[A L F]

Thanks Phil, very very interesting.

I don’t know whether to continue here or open a new thread, but the topic interests me a lot.
As written above, in the economy of a major refit or a new build, 0.5 l/h changes little, but the subject is very interesting.

I have always been convinced that a naturally aspirated engine at low rpm allows for lower consumption (not efficiency), since it can be run at few rpm with relatively large propellers and low slip. Coupled with a CPP you can have low prop rpm and low engine rpm, with the possibility (by reducing pitch) of facing sea and wind at full engine rpm (attention to propeller diameter, cavitation lurking…).
And this concept of low rpm → low consumption I believe is not contradicted by your writing.

Of course, the naturally aspirated engine at low rpm (or relatively low) will “suffer” a bit, it will be under its optimal regime for 80% of the time, but what does this realistically imply? A smaller pulley for the alternator? Gearboxes, does a PRM125 really absorb 5% less than a ZF25?

This is to say that a boat that absorbs 20 hp at 6.2/6.5 knots may need all of the (let’s suppose) 60 hp for sea and wind (and the propeller that would be optimized for 6.2 knots at 1400 rpm certainly won’t be at full throttle, I know…and here we are talking about CPP).

I don’t know, speaking only of consumption I am still convinced that 1400 rpm, maybe “rough” as a mechanical pump can deliver, are more convenient than 2400 even with common rail and VGT.

Thanks for the great discussion.

I hope my English is clear

 

[BlueBell]

A L F ,

I see your location is "None". Is that None, USA?

I also see in your opening sentence you are looking for

above all economy

So the answer to this question

I was wondering whether it is (above all economically) feasible to design and install a true diesel‑electric hybrid in the power range of 50–70 hp on a displacement vessel (medium‑heavy, D/L 320–400), with a 25" propeller and cruise rpm around 500.

...sadly is 'no', as described by all the contributors above.

You are here to learn. What have you learned 'in a nutshell' ( briefly )?
In other words; what are you going to do?

 

[A L F]

Sorry, I did not fill out the profile correctly, I am writing from Italy.

I do not understand the tone of the message. If I asked a wrong question or broke the forum rules (I don’t think so), I apologize.

If all threads closed after the first reply, it would be a forum with little participation. Just as if everyone who asked something could make their wishes come true, it would be a much better world.

For now I have learned from Phil, with whom I believe I have an interesting discussion open, if it is annoying I apologize.

My goal is to get information (which is useful in forums) to decide where to direct my budget for the future.

 

[fallguy]

As for economical, I hardly see how for most use cases, which Bluebell is trying to say above using a rhetorical style.

And there is a difference between economical and cheap. Economical means does it have a payoff? So, say your use case is a vessel to go around the world and not worry about fuel at all. You would evaluate the cost of this system versus an all fuel system and if the all fuel system has a problem of needing fuel where not available; the economics of the diesel hybrid cannot be beat.

But for most use cases, the diesel-electric option is layers of unneeded complexity and cost.

I cannot offer the detailed responses about how to achieve the goals, but I am an accountant and can easily talk about economics.

And the first thing to do when designing a boat is to understand the use case (SOR); not to design the propulsion system. Of course, this can take away lots of fun which is not my intent.

Anyhow, I will return to my rightful place as a quiet observer on the details of which I cannot offer squat.

 

[philSweet]

A quick note on Variable Guide Vane turbos. These are rather poorly understood. On a car - not a boat - a car - the single biggest challenge with turbos is retaining instant throttle response. Truckers get used to the lag. People buying cars don't want it. So turbos are made very small, and vgvt is used to enhance spool-up. It isn't an efficiency thing. Efficiency went out the window when they stuck that tiny turbo on it. Vgvt is an interim technology kludge. All turbo mfgs are working to get rid of it. Much better is an electric motor/generator on the turbo shaft to aid spool-up and allow a bigger diameter turbo.

On boats and pretty much everything else that isn't a car, turbos are big, heavy, fixed geometry, and slow to respond to throttle changes. These are the ones that significantly boost engine efficiency. On commercial trucks, Vgvt has been integrated into emissions control systems now, so it will be harder to get rid of than previously thought. But it is still a kludge. On a boat that operates at a constant rpm, you can happily avoid vgvts, improve reliability, reduce cost, and better efficiency.

 

[montero]

A quick note on Variable Guide Vane turbos. These are rather poorly understood. On a car - not a boat - a car - the single biggest challenge with turbos is retaining instant throttle response. Truckers get used to the lag. People buying cars don't want it. So turbos are made very small, and vgvt is used to enhance spool-up. It isn't an efficiency thing. Efficiency went out the window when they stuck that tiny turbo on it. Vgvt is an interim technology kludge. All turbo mfgs are working to get rid of it. Much better is an electric motor/generator on the turbo shaft to aid spool-up and allow a bigger diameter turbo.

On boats and pretty much everything else that isn't a car, turbos are big, heavy, fixed geometry, and slow to respond to throttle changes. These are the ones that significantly boost engine efficiency. On commercial trucks, Vgvt has been integrated into emissions control systems now, so it will be harder to get rid of than previously thought. But it is still a kludge. On a boat that operates at a constant rpm, you can happily avoid vgvts, improve reliability, reduce cost, and better efficiency.

We have a lot of different bouquets of flowers here in the EU: VGT, Biturbo, Triturbo, etc.
It's funny how emission standards force engineers to come up with solutions. Less funny is the reliability and when you have to pay for their repairs. It's a bit like wartime solutions. Wars with stupid regulations.
As Phil wrote, overengineering on a boat can be avoided unless the law forces you to do so.
However, the issue of maritime safety arises here. That's why legislators should sometimes go to sea.
I remember a BUKH engine from a rescue boat:

it had three starting methods. That got me thinking.

 

[gonzo]

the single biggest challenge with turbos is retaining instant throttle response. Truckers get used to the lag.

I don't know if you have driven a modern truck, but the throttle response is better with turbos than the normally aspirated engines of the 70s.

 

[HelmutSheina]

I don't know if you have driven a modern truck, but the throttle response is better with turbos than the normally aspirated engines of the 70s.

I haven't driven a truck since the late 1980s, but have a Kia Sportage with a 4cyl 2 litre diesel engine. During general driving throttle response is good and any lag is so minor as to be unnoticeable.

It is different though in situations requiring heavy acceleration, the lag is severe enough to cause an accident with an inexperienced driver, say crossing an intersection; then when the turbo starts working it goes into race mode which could also be dangerous for the uninitiated. The car has been great apart from this issue, and uses 6.7l/100km at highway speed (110 kmh).

Sorry, forgot you don't like metric. 35 mpg (US) at 70mph

 

[montero]

I don't know where you live, but the 2-liter curse goes far.
I don't know who came up with it or why.
Attempts to power heavy vehicles with a 2-liter twin-turbo diesel engine usually end up in the garage.
Nobody wants them, and rental companies avoid them like the plague due to their reliability.
Tell me why they specified 2.0 liters and not, say, 2.5 liters or 3.0 liters, which seems more logical for heavier vehicles.
I'll buy the 8.1 Vortec and change the oil frequently.

 

[HelmutSheina]

It's a small vehicle and the engine is quite adequate 95% of the time. This car has been super reliable, tows up to a tonne easily and the fuel economy is welcome with the distance I cover. The bloke that inspects it for registration says the diesels are great, but run from petrol models. Maybe you are talking European made cars?

This is Australia and there are opportunities to live in quiet places with interesting waterways, but the distance away from capital cities to achieve this becomes a major factor. The nearest city, Brisbane, with boat building gear, or anything beyond basic handyman hardware, is 400km away from me, so about a 1000km run to collect plywood, epoxy, isopropyl, etc etc. Sure I can freight it if I add $500 to the bill, or I can drive this little car that will do that on 70l of diesel and the trip is achievable in a long day.

 

[montero]

I think you misunderstood me.
There are four Kia Sportages parked around the block.
I've been driving small diesels my whole life. The smallest I can remember was a 1.6L Opel diesel with a 4-speed manual gearbox.
Mpg was great. Similar to modern diesels.

The real problems are the emission requirements.

They create pointless complications in the name of Creta.

I drove over 4000km modern 2.0 l diesel 140hp . Heavy car VW Crafter FWD.
MPG incredible like sedan car. Relatively fresh 50000 km. Handling like Audi.

I wish to have 3.0 d engine under the hood .Not 2.0l..

 

[HelmutSheina]

There are far more ~3l diesels around here than 2l ones, everyone needs a huge dual cab utility to make them feel better about their deficiencies. The underpowering must be an EU thing as most vehicles here have appropriately sized engines. Toyota was selling Landcruiser 4WD vehicles with V8 diesels until recent times.

 

[montero]

I've seen them occasionally. The Russians have them, but they're not in the EU.
I've seen a few on Polish plates.

I think I saw this engine as a Yanmar.

Remember, you can't buy a new 2-stroke Tohatsu anymore, even in Australia.
Unfortunately, it's not good thing. The ban on carbed 2-strokes in the EU has been in effect since 2020.
It's changed things a bit with the illegal import of Chinese 2-strokes, but these are minimal quantities.

I feel sorry for carbed 2-stroke engines because they were refined and simple, with minimal electronics. They're the Kalashnikovs of engines.

I repeat again that this simplicity is crucial for maritime safety.

 

[montero]

I think small let's say 30hp two strokes should be allowed everywhere .
Allright 40-50hp ...