modifying the diesel for more economy

[Ernie Rogers]

Hello, guys,

I'm back. I am digging into the Kook paper (Tas link). About ignition delay, the informaiton is fairly convincing that substantial lowering of the oxygen partial pressure causes a delay in ignition, and also slows the burn rate. See figs. 12, 13, and 14 for that. (I note in passing that the dilution gas is not real exhaust gas.)

Of far greater interest is the effect of lowered oxygen concentration on NOx formation and engine efficiency. The evidence is very good that total NOx correlates well with their rate equation 2 (see fig. 10). The critical parameter seems to be the energy density in the flame front.

Two thoughts--

1) If the cylinder pressure is raised while keeping oxygen concentration low (low concentration, high partial pressure) then you have the prospect of rapid ignition and burn (depends on partial pressure) while the flame front temperature and NOx stay low (depends on oxygen concentration).

2) Instead of diluting the air, you could dilute the fuel and also lower the flame front temperature. What do you think?

I am still reading, will have comments on efficiency later.

Thanks, Tas, for the education. Let's proceed.

Ernie Rogers

[AXMonster]

Originally Posted by diesel_john

I read about multi-pulse injection, is there gain in efficiency with this technology or is it aimed at emissions?

Its mainly for NVH and emissions John.

Most, if not all, common rail injection systems now employ at least two injections; a pilot injection to initiate combustion a few degrees before the main injection, and the main injection which will deliver the remaining circa 90% of the fuel quantity. This quietens down the main combustion when it is injected as the flame in the combustion chamber does not ignite the fuel with a harsh knock (as it would do if it were to ignite by compression ignition alone).

Newer systems (typically with DPF technology) are capable of up to 3 pilot injections, 1 main injections and 2 post injections!

[theunchosen]

There is a gain in efficiency for Stratified Fuel Injection(SFI or FSI depending on whose doing it ^_^). It allows you to cool the the air in the chamber. The idea is you have like a water sprinkler system on your lawn that clicks back once its reaches its full travel range? With gassers they are looking at lots of injections(most are talking 7 or more).

The problem with injecting all at once is some of the fuel might ignite before it all gets in, so in that sense diesels also have pre-ignition(it happens before you want it to(but its not engine destroying catastrophic like gassers). stratified injection lets you cool the cylinder with several small squirts so when you go to dump most of the fuel in the last 2-3 injections it all gets in before it ignites(otherwise you spray fuel in 02 empty areas of the cylinder and they don't burn). It also allows for a much, much more homogenous burn mixture because the outset pulses are already completely dissipated around the cylinder when the ignition event happens.

If pulsing is the same as stratified injection there are efficiency gains to be had. I do not believe it influeces emissions. In gas engines it does but thats because to do this requires the use of GDI, which is the prime mover in emissions reductions, not stratification.

[diesel_john]

very interesting AXMonster, i didn't know multipulse was being used already. i need to read up TDci and DPF. i am beginning to see why the old prechamber works so well, but for emissions.

theunchosen, i am confused a bit about the gasser explaination but would like to see a thread on just gasser injection. i realize gassers are becoming more like diesels, eg. direct injection.

[Ernie Rogers]

Okay, guys,

How about an acronym dictionary,

NVH
DPF
GDI
TDci

Ernie Rogers

[Big Dave]

My diesel came from the factory with "Split-Shot" (two pulse) injection.

The idea was quieter operation.

Last summer I converted to "Single-Shot" (all at once) injection.

No change in MPG. No perceptible change in noise.

IMO, a dead end.

[diesel_john]

NVH noise vibration harshness 19 years at that

maybe spit shot helped emission as suggested by axmonster

http://en.wikipedia.org/wiki/Diesel_particulate_filter

http://en.wikipedia.org/wiki/Gasoline_direct_injection

http://en.wikipedia.org/wiki/Ford_Duratorq_engine

i wasn't sure either had to look them up