Ducted diesel injection

Interesting development, especially the potential for retrofitting to older engines.

https://share-ng.sandia.gov/news/resources/news_releases/ducted_injection/

Neat idea! Will follow!

It's not something you'll see soon in small marine engines. And never in older style engines.

I don't think this concept could be easily retrofitted to existing engines. One point of modern design is for injector to have smallest practical diameter to make room for valves and coolant flow. The tip of this injector will be a good bit larger in diameter.

The whole combustion chamber will need to be designed around this. But existing blocks probably used as is. Piston bowl shape and head geometry will be different.

I bet there are a lot of engine mfr's and labs messing around with this!!

If it really reduces soot and NOx formation, it really can be a game changer.

No real relevance to us with smaller older mechanical engines. Soot and NOx? What are those? For modern large commercial engines, and modern CR engines of any flavor, this could be real.

I think the article alluded that retrofit would only be on much larger engines that cost millions. In that case a new head or other major rework might make sense.

This is why we leave government out of (nearly) everything, if left alone, the market finds solutions; these injectors and that new prop spring to mind. Soon we will be able to boat guilt-free (I just threw that in as I’ve never met a guilty boater).

Xsbank said:

This is why we leave government out of (nearly) everything, if left alone, the market finds solutions; these injectors and that new prop spring to mind.

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You DO realize this came out of a government funded lab, right?

ducted injection? does anyone comprehend how it works?

The bunsen burner is burning free flowing gas, that I understand.
But our diesel internal combustion engines inject fuel and air which does not ignite until compressed.
How is this ducted injection injecting the optimal air/fuel, which of course will cut down on soot, differently than current systems (in newest engines).
sounds similar to gas engines running leaner and cleaner

"Mueller says that injectors in a traditional diesel engine create local igniting mixtures that contain two to 10 times more fuel than is needed for complete combustion."


The hassle is the fuel is sprayed in as droplets and has to vaporize to be burned.


Anything that will better vaporize the fuel is good.

I think the basic injection is the same, liquid under high pressure shot into the combustion chamber. What is added is a small "duct" where the fuel en-trains air from the inlet side and the ensuing turbulence in the duct encourages mixing. This is much like the Ricardo pre-combustion chamber developed in the 1920's-1930's and still used in our little Kubota's et. al., but without the flow and heat transfer losses (bad) there that penalize efficiency. The duct structure will be right in the cylinder combustion chamber (piston bowl, however shaped) and won't create flow losses on the compression and firing stroke like the Kubota. The only flow losses will be from the injection flow which is lost energy anyway.

I wish I came up with the idea!! I hope it works as well as discussed.

Soo-Valley said:

ducted injection? does anyone comprehend how it works?

The bunsen burner is burning free flowing gas, that I understand.
But our diesel internal combustion engines inject fuel and air which does not ignite until compressed.
How is this ducted injection injecting the optimal air/fuel, which of course will cut down on soot, differently than current systems (in newest engines).
sounds similar to gas engines running leaner and cleaner

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The link does explain all of it.

But the basic gist is they analyzed how emitting the fuel into the chamber actually combusts. And figured out that arranging ducts to shape the flow in a different manner can cut down significantly on the amount of pollutants created. That and it would be within the realm of something that could be retrofitted to existing engine technologies. Whether that extends all the way down to the engines used in boats remains to be seen.

Ski in NC said:

I wish I came up with the idea!! I hope it works as well as discussed.

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Me too. Lots of bogus “inventions” come around, but this one actually seems to have merit.

Just to dispel one
Possible misconception, a diesel does’t inject an
Air/fuel mixture, only fuel. Air is drawn in and compressed causing it to heat up. The fuel is then sprayed into the hot air where it burns. And diesels aren’t sensitive to air fuel mixture the way gas engines are. There just needs to be enough air for complete combustion. More air is fine. It’s only a problem when there is too little and then you incomplete combustion and black smoke. This is why turbos are so effective with diesels because they allow you to jamb pack a ton of air into each stroke, allowing you to burn more fuel and generate more power.

There is always a surplus of air/oxygen in diesel engine operation vs gasoline engine. A diesel engine will always run lean. The trick is to get the air and the fuel to mix appropriately. That is why injectors use high pressure to "atomize" the fuel, have multiple ports to distribute the fuel, the piston surface, combustion chamber and air inlets are shaped to encourage turbulence and why electronic engines may have multiple injection events. There is a trade-off between extreme turbulence (small, high-speed air inlets) vs volumetric efficiency (friction losses). It will be interesting to see how the new approach makes that trade-off.

assembly of four to six small tubes — or ducts — directing fuel mixture from the injector to the points of ignition.
This sounds like premixing air/fuel before injecting

traditional diesel engine create local igniting mixtures that contain two to 10 times more fuel than is needed for complete combustion
“Installing the ducts enables us to achieve diesel combustion that forms little to no soot, because the local igniting mixtures contain less excess fuel.”
This sounds like using less fuel, an option I thought was already available with a tuned engine.

Overall, to me it sounds like eliminating a separate air and fuel intake, premixing air/fuel and then injecting the correct balanced amount. So leaner/cleaner burn.

Soo-Valley said:

assembly of four to six small tubes — or ducts — directing fuel mixture from the injector to the points of ignition.
This sounds like premixing air/fuel before injecting

traditional diesel engine create local igniting mixtures that contain two to 10 times more fuel than is needed for complete combustion
“Installing the ducts enables us to achieve diesel combustion that forms little to no soot, because the local igniting mixtures contain less excess fuel.”
This sounds like using less fuel, an option I thought was already available with a tuned engine.

Overall, to me it sounds like eliminating a separate air and fuel intake, premixing air/fuel and then injecting the correct balanced amount. So leaner/cleaner burn.

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My understanding is that it's more like the nozzle on a propane torch. Rather than have the injector squirt fuel directly into the combustion chamber, this injects fuel into a tube which, due to venturi effect, draws air (the air that is in the combustion chamber already) into the tube behind the fuel. The air mixes with the fuel and comes out the business end of the nozzle burning cleanly and very hot. It's incredibly simple and clever. If it works as well as they say, and the technology is licensed for a reasonable fee, this should become the norm in future diesel engines. It might even even be applicable to gasoline engines.

Mischief Managed said:

My understanding is that it's more like the nozzle on a propane torch. Rather than have the injector squirt fuel directly into the combustion chamber, this injects fuel into a tube which, due to venturi effect, draws air (the air that is in the combustion chamber already) into the tube behind the fuel. The air mixes with the fuel and comes out the business end of the nozzle burning cleanly and very hot. It's incredibly simple and clever. If it works as well as they say, and the technology is licensed for a reasonable fee, this should become the norm in future diesel engines. It might even even be applicable to gasoline engines.

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That is now my understanding too. This will eliminate intake valves as currently used drawing in air on the downstroke. Premixed air/fuel injected.

A government funded lab is a far cry from mandating emission levels or making us all buy compact fluorescent bulbs. I think you missed the point.

Soo-Valley said:

That is now my understanding too. This will eliminate intake valves as currently used drawing in air on the downstroke. Premixed air/fuel injected.

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No, the intake stroke and related valves are the same as a traditional engine. No injection of premixed air/fuel. The only thing changed is nozzles entraining air local to the injector tip.

How well it works in the field is yet to be seen. These injection events are very brief so getting the air moving in the nozzle might be limited by simple inertia, especially in high rpm engines. Less an issue in big slow engines, which might be the focus of this technology.

On small engines, packaging and installing the nozzle may require a fair amount of redesign of the injector mounting in the cylinder head. It would require a physically larger injector tip.

wkearney99 said:

You DO realize this came out of a government funded lab, right?

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You mean tax payer funded lab.

Ski in NC said:

No, the intake stroke and related valves are the same as a traditional engine. No injection of premixed air/fuel. The only thing changed is nozzles entraining air local to the injector tip.

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Then I give up understanding this.
A bunsen burner pre mixes air/fuel, as does a propane torch, as does a home fireplace to get that blue flame which has less soot.

Soo-Valley said:

Then I give up understanding this.
A bunsen burner pre mixes air/fuel, as does a propane torch, as does a home fireplace to get that blue flame which has less soot.

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I think the idea is that some air gets pre-mixed with the fuel to help distribute and atomize the fuel better, but the rest of the air is drawn in conventionally. It's still compression ignition from my understanding, so the fuel wouldn't be injected already-burning.

It is a tube or duct mounted right at the injector tip. The injector squirts dead center into the duct, which is short and the air/fuel exits presumably a bit better mixed. Only motive force is provided by the injection stream itself. Small device, maybe a few diameters bigger than the injector tip. Rest of the engine more or less standard design.

stoichiometric air-fuel ratio for diesel is 14.5:1
Unless you maintain that ratio you are not burning at optimal.
Therefore the air/fuel ratio must be premeasured for optimal burn.
colder air is more dense and has more oxygen than warm/hotter air. The amount of fuel for complete burn must be adjusted. Unless it is measured as in pre mixed, it is just an assumption. all cylinders of the exact same volume may not draw in the same volume of air. Yet our current system feeds the same measured fuel to each (as long as each injector is working the same).
IMHO

Diesels almost always run lean of stoich. If they didn't, you'd have to throttle them like a gas engine to reduce power instead of just reducing fuel. And then they'd be just as bad as gas engines for light load efficiency.

Capitaine R said:

You mean tax payer funded lab.

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Isn't that like saying your employer bought your car?

Soo- What your are describing is more like the gas engine (Otto) cycle. In a diesel the fuel is injected into hot compressed air near piston top dead center. The heat from the compression of the air is easily hot enough to start igniting the fuel. Except on cold days with slow starter cranking.

The amount of fuel injected depends on what the operator is asking the engine to do (through the helm lever and governor). Air/fuel ratio varies from in the hundreds for idle to a max of about 20 at full power. The actual burn occurs on the interface of the fuel plume and the hot air in regions where it is near 14.5. The mix is very turbulent so eventually whatever is injected gets burned (mostly) with a little soot left over.

As noted above, diesels always run on excess air, sometimes a lot- even 100 times at idle as Ski notes above.

But I have a hard time seeing how a tiny duct will allow enough air to mix with the injected stream of diesel to do any good. Maybe it just gets the initial squirt of diesel off to a good burn which lets the rest of the diesel burn more cleanly.

I wish I could find a video I had seen of the actual diesel burning process in a diesel engine while running. Very revealing. Love to see the same type of video for this ducted injection technology .


David

Yea, I am skeptical too. The injection event is so brief that I just don't see that much mixing will occur. But if it does (and it might), this really holds some promise. Easy enough to experiment.

Did not find diesel video.
Here is a cool one on propane and gas.
Gas run starts at 5 min.

Maybe Rick B knows where a diesel video is??