Ducted diesel injection

[bluebyu]

Here is a diesel version:

 

[Ski in NC]

Found another writeup, gives a bit more clarity.

https://www.scientificamerican.com/article/can-diesel-finally-come-clean/

 

[SteveK]

Found another writeup, gives a bit more clarity.

https://www.scientificamerican.com/article/can-diesel-finally-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.

 

[rslifkin]

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.

 

[SteveK]

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.

 

[Ski in NC]

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.

 

[SteveK]

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.

 

[Ski in NC]

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!!!

 

[pacopico]

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.

 

[wkearney99]

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?

 

[Mischief Managed]

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.

My guess is that as the fuel evaporates, it dramatically cools the small amount of air inside the tube and there's just enough of a temperature drop that it won't ignite. Once it hits the outlet end of the tube, it's nicely mixed with the air and ignites instantly.

 

[pacopico]

Heh, got a glossary for that alphabet soup? SCR, BOI, PM, USEPA?

SCR: selective catalytic reduction - one of the most popular methods to reduce NOx from Diesel engine exhaust, where urea is injected into the exhaust stream to react to the exhaust gasses and then react to a catalyst element to convert the NOx to nitrogen and water.

BOI: Beginning of Injection

EOI: End of Injection

PM: particulate matter, mostly unburned hydrocarbons, commonly referred to as soot.

USEPA: United States Environmental Protection Agency ?

I’ve got more, sadly.

 

[Ski in NC]

boi- beginning of injection
eoi- end of injection

Both beginning and end are where atomization is worst, more droplets, less spray, more soot and stink and smoke

scr- selective catalytic reduction. Exhaust after treatment to reduce NOx (oxides of nitrogen, considered a diesel pollutant.

usepa- united states environmental protection agency. Source of our pollution regs for diesels. Can be argued that they are good or bad, depending on your perspective.