Most efficient piston type engine? 3

[enginesrus]

The first engine that comes to mind is the Wartsila (formerly Sulzer) 2 stroke ship engine, Mercedes is suppose to have a 50% efficient F1 racing engine.
Nissan is suppose to have a 50% engine, even Fairbanks Morse, as well as Achates.
So what is the latest news on high efficiency?

 

[TugboatEng]

Do diesel engines not detonate? Is there no shockwave produced? I'm talking single injection event engines, multi-injection changes everything.

 

[SwinnyGG]

When they are operating correctly, no. When their are problems, yes - a diesel engine can experience detonation and the associated mechanical damage just like a gas engine can.

 

[BrianPetersen]

Diesel engine situation is a little different. There is a normal ignition delay between the start-of-injection and the start-of-combustion which results in some portion of the fuel burning in premixed fashion which is responsible for the audible chatter of a diesel engine, but (A) it isn't the end-gas near the piston rings, it's in the vicinity of the injector - depending on how long the ignition delay is, (B) it isn't the entire fuel-air charge igniting like this, just a piece of it, (C) the charge is not homogeneously mixed at the time that this happens - so it doesn't all ignite at once. The normal ignition in a diesel engine starts with a rapid rate of pressure rise, but it should not be a detonation.

Diesel engines knock louder upon cold start because the ignition delay is longer.

Injection timing set too far advanced results in louder knock because (1) the temperature in cylinder is lower at the time of start-of-injection because the compression stroke isn't finished yet, (2) the longer ignition delay results in more fuel being in-cylinder and partially premixed by the time ignition happens. And yes, excessive ignition timing advance certainly can break stuff.

Newer modern-tech diesel engines are a lot quieter because the rate of injection is much more tightly controlled. It's not uncommon to split up the injection cycle into two parts - a small initial pulse that premixes and ignites followed by the main injection event that burns progressively.

 

[TugboatEng]

I was steering towards the shockwave not being the only cause of damage. In the diesel engine there is a shockwave at the start of ignition but as BP said, it's a small portion of the charge burning and the cylinder pressures are still low. The rapid combustion during detonation causes a spike in cylinder pressure and the associated temperature. The shockwave things the boundary layers. One can have a shockwave, a knock, without damage. Maybe we should use detonation to imply a combination of shockwave and heat.

 

[SwinnyGG]

In a properly functioning diesel engine there is no shock front.

The shock front is what separates normal combustion from detonation.

 

[Factoter]

Tug? (And anyone else) what is your opinion on Ether, starting fluid use in Diesel engines? Starting fluid happens. —-to make a colloquialism of it. Buy can it be used safely, should it be?

 

[Factoter]

SwinnyGG. You make some strong points, particularly the knock-down on knock. To defend the use of knock above isn’t really necessary since it was used in that particular article to talk-the-talk so to speak. Literature on the subject uses acronyms that are listed above, never knock, and the distinction being drawn dividing detonation into 2 categories is academic, it doesn’t apply to us here, rather the moon and stars are witnesses I believe.

 

[BrianPetersen]

Starting fluid + glowing glow plug = bad news.

 

[Factoter]

Dimethyl Ether, DME, definitely should be used as a fuel, or additive because:
“<it> has one of the highest well-to-wheel efficiencies with light and heavy-duty DME-fuelled vehicle efficiencies as 19% and 22.5%, respectively”

DME is made from methane and syngas from biomass, and in terms of CO2, is possibly one of the cleanest fuels, by virtue of carbon neutrality. Here is a wheel-to-wheel comparison that shows how it can blast electric vehicles from contention:

https://gmobility.eu/what-is-well-to-wheel/

 

[BrianPetersen]

... the main difficulty being its boiling point at atmospheric pressure of -24 C means that you are starting over in terms of distribution and end-use.

Any sort of combustion engine that burns "a fuel" (no matter what it is) with air, and farts out its products of combustion, is going to have to deal with NOx.

Meanwhile ... I'm 22 km from home with my EV parked outside. The low-charge-warning was on when I got here (having not bothered plugging in the last three days), but the GOM says I have plenty of charge left to get home, where I can plug it in.

 

[TugboatEng]

Diesel engines used to come with attached ether tanks just for starting. Modern direct inject diesel engines have rendered ether obsolete. If your engine can't start without ether it's already broken. Ether isn't going to break it more.

 

[Factoter]

Welcome to the, “Ether isn’t going to break it more?” NoobTube Challenge!

I’ve seen mechanics do cold-starts, spraying abundant ether, total abandon, and also the reverse where mechanics act like it’s live grenade . Thanks for the word on this.

 

[TugboatEng]

Warning, not on topic!

For example, I had to start this engine that has been ingesting salt water. There was still residual water in the intake manifold so I had to use ether to get it going.

The owner warned me about breaking piston rings. They leased me a boat that didn't run. I was damn well going to make that engine start so I could start earning revenue again.

I really despise this series of engines.