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Old 12-08-2019, 09:39 AM   #21
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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.

.....................
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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Old 12-08-2019, 09:52 AM   #22
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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.

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.
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Old 12-08-2019, 10:10 AM   #23
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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.
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Old 12-08-2019, 10:33 AM   #24
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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
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Old 12-08-2019, 10:36 AM   #25
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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.
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Old 12-08-2019, 08:54 PM   #26
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You mean tax payer funded lab.

Isn't that like saying your employer bought your car?
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Old 12-09-2019, 06:14 AM   #27
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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.
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Old 12-09-2019, 07:52 AM   #28
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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 .


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Old 12-09-2019, 08:01 AM   #29
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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.
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Old 12-09-2019, 08:19 AM   #30
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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??
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Old 12-09-2019, 08:23 AM   #31
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Here is a diesel version:
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Old 12-19-2019, 02:27 PM   #32
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Found another writeup, gives a bit more clarity.

https://www.scientificamerican.com/a...ly-come-clean/
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Old 12-19-2019, 04:38 PM   #33
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Found another writeup, gives a bit more clarity.

https://www.scientificamerican.com/a...ly-come-clean/
Thanks, pre mixed air/fuel before ignition.
How that is achieved mechanically will be interesting. I still think the intake valve will be eliminated in new engines and all air pushed through with fuel premixed.
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Old 12-19-2019, 05:05 PM   #34
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Thanks, pre mixed air/fuel before ignition.
How that is achieved mechanically will be interesting. I still think the intake valve will be eliminated in new engines and all air pushed through with fuel premixed.

Based on how diesels ignite their fuel, that's not a viable option. In a compression ignition engine you can't inject the fuel until right when you're ready to light it, so at least most of the air already needs to be in there and compressed.
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Old 12-19-2019, 05:49 PM   #35
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Based on how diesels ignite their fuel, that's not a viable option. In a compression ignition engine you can't inject the fuel until right when you're ready to light it, so at least most of the air already needs to be in there and compressed.
That is based on how it works today. This is a new way. We can agree to disagree, but if the intent is to mix fuel and air which this is, then it needs to be premixed on input, unlike it is done today. If air is already in there, then it has not gone through the Bunsen burner inspiration. Time will tell.
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Old 12-20-2019, 11:48 AM   #36
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Soo, you can not have the fuel in a diesel pre-mixed before compression. The heat from compressing the mixture will ignite it before the right time (well before top dead center) and either kick engine backward or break things.

For a diesel to work, fuel has to be admitted near top dead center, and the fuel has to admitted over time. If all was injected (or ignited) at once, the pressure spike would make it less efficient or break things. The injection is designed to raise the pressure on ignition, and then continue injecting at a rate to keep pressure somewhat constant as piston descends, until inj stop.

This nozzle arrangement just enhances mixing right at the injection site, otherwise no big change to the thermodynamic cycle.
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Old 12-20-2019, 12:03 PM   #37
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Ski, I get how it works now.
I do not get how the fuel is prevented from igniting at the intake end of the tube before the fuel/air is mixed out the other end.
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Old 12-20-2019, 01:12 PM   #38
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No fuel is in the tube until injector starts injecting. Imagine squirting WD40 from the can in one hand, and aiming it into a toilet paper tube held with the other hand. Don't try that with it lit!!!
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Old 12-20-2019, 02:09 PM   #39
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I think the second link leading picture shows it clearly in operation - mounted radially around the spray tip, in line with the spray holes and works as an aerator to further atomize the fuel, allowing for a quicker ignition and progression of the injection event to conflagration.

The BOI/EOI event is really where it would help as at those points the injection pressure is lower than ideal, causing dropout of the liquid fuel.

As someone whose job entails selling and servicing "large, million dollar" locomotive diesel engines in marine and power generation applications I look forward to a manufacturer trying this out.

This week I had to replace some SCR bricks in a USEPA Tier 4 diesel, and the dry PM that accumulates in the SCR housing creates quite a mess...gives a good visual on what is really emitted from the tailpipe.
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Old 12-20-2019, 06:12 PM   #40
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The BOI/EOI event is really where it would help as at those points the injection pressure is lower than ideal, causing dropout of the liquid fuel.

As someone whose job entails selling and servicing "large, million dollar" locomotive diesel engines in marine and power generation applications I look forward to a manufacturer trying this out.

This week I had to replace some SCR bricks in a USEPA Tier 4 diesel, and the dry PM that accumulates in the SCR housing creates quite a mess...gives a good visual on what is really emitted from the tailpipe.
Heh, got a glossary for that alphabet soup? SCR, BOI, PM, USEPA?
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