HCCI

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
gruntguru
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HCCI

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As suggested by @johnny comelately, this probably deserves a thread of its own. Over to you johnny.

je suis charlie

johnny comelately
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Re: HCCI

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From a relatively uninformed base what I imagine is that with the fuel charateristics known and the application of pressure and somewhat governed temperature that spontaneous combustion occurs.
The H part is probably incorrect for the F1 situation because of stratification, as Pat S. says its not that easy to classify this engine.
up until recently no engine manufacturer had made a success of it because of its unpredictability, to the best of my knowledge your honour.
But introducing spark initiation via multiple flame fronts must produce adequate predictability.
you can see that if spon com occurred where there was originally a problem in the fartherest reaches for example it would solve a big problem.
But the thin red line and the transition with detonation is something I dont understand (see other combustion videos posted)

gruntguru
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Re: HCCI

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The more I look at that video the more it appears the spontaneous combustion at the perimeter of the chamber is NOT initiated by events in the pre-chamber. Conclusion - for al least the one cycle shown, combustion would have proceeded without the spark.

The combustion at the perimeter progresses inwards as a flame front - ie not HCCI!

The jet ignition is still responsible for rapidly accelerating the combustion of the remaining charge.

Hypothesis. The spontaneous combustion is a kind of "pre-ignition" event that is accelerated by its proximity to the squish zone and the high turbulence there prevents conversion to a detonation event.
je suis charlie

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vorticism
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Re: HCCI

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HCSSSACI (homogeneous charge stratified squish spark assist compression ignition) 8) Pat did say it was hard to define.

What was the claim for the video? It just says 'new engine'

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Zynerji
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Re: HCCI

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gruntguru wrote:
Tue Apr 26, 2022 11:40 pm
The more I look at that video the more it appears the spontaneous combustion at the perimeter of the chamber is NOT initiated by events in the pre-chamber. Conclusion - for al least the one cycle shown, combustion would have proceeded without the spark.

The combustion at the perimeter progresses inwards as a flame front - ie not HCCI!

The jet ignition is still responsible for rapidly accelerating the combustion of the remaining charge.

Hypothesis. The spontaneous combustion is a kind of "pre-ignition" event that is accelerated by its proximity to the squish zone and the high turbulence there prevents conversion to a detonation event.
It still looks like a vortex ring is ejected by the pre chamber nozzle, and is ignited by self-shear to me.

I'm not an engineer, so it's probably not that.

johnny comelately
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Re: HCCI

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gruntguru wrote:
Tue Apr 26, 2022 11:40 pm
The more I look at that video the more it appears the spontaneous combustion at the perimeter of the chamber is NOT initiated by events in the pre-chamber. Conclusion - for al least the one cycle shown, combustion would have proceeded without the spark.

The combustion at the perimeter progresses inwards as a flame front - ie not HCCI!

The jet ignition is still responsible for rapidly accelerating the combustion of the remaining charge.

Hypothesis. The spontaneous combustion is a kind of "pre-ignition" event that is accelerated by its proximity to the squish zone and the high turbulence there prevents conversion to a detonation event.
This particular discussion now becomes a matter of timing: which occurs first.
If spon com happened too early it would increase pumping losses unacceptably.
But if, by the appropriate controls, the spark happens just before the critical pressure rise they would complement each other nicely, as the pressure rise after the jet flame aids in the spon com and provides that complete combustion (from all 4 corners of the globe, so to speak).
This would be feasible with knock sensors and cylinder pressure sensors if you can get ahead of the curve (from research) rather than reaction when its all too late to prevent grenading.

gruntguru
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Re: HCCI

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Well they have pressure sensors in the car so they can adjust the timing (and MAP, MAT and inj' timing) on the fly, according to an algorithm based on cylinder pressure from the previous cycle for that cylinder.
je suis charlie

johnny comelately
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Re: HCCI

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gruntguru wrote:
Wed Apr 27, 2022 2:56 am
Well they have pressure sensors in the car so they can adjust the timing (and MAP, MAT and inj' timing) on the fly, according to an algorithm based on cylinder pressure from the previous cycle for that cylinder.
Yes, the "previous" giving rise to the predictive.
Knowledge of the fuels behaviour is so paramount and they seem to have high resources on this.
One area of using the controls is the turbo MGUH area:
What would be the safety margin for keeping manifold pressure adequate for reliable spon com (with the spark) and diversion (to the GH or waste) to avoid damage, +- 2 psi??
Ignition timing control may be set more for compatibility with the spon com rather than MBT

gruntguru
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Re: HCCI

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Your last line is a good point. I had forgotten that (apparently) the spon com occurs independently of the spark.

No idea what the sensitivity to MAP might be apart from saying "high". Similarly to MAT but adjusting either of these is much slower than one engine cycle and will affect all cylinders.

Perhaps the best option for a rapid, individual-cylinder adjustment to spon com would injection timing. Haven't thought through how that would work.
je suis charlie

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vorticism
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Re: HCCI

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Localized HCCI maybe. As a control/safety feature. Partial HCCI with TJI igniting the remainder.

I'll edit my acrimonious acronym from eariler to read HCTJASCI (homogeneous charge turbulent jet assisted stratified compression ignition). Thus you get some of the charge lit via HCCI while retaining spark initiated combustion with the TJI/prechamber.

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Zynerji
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Re: HCCI

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Stupid question, but could one use a piezo disc in the chamber to "snap" a pressure rise through volume change and cause spon com?

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vorticism
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Re: HCCI

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Piezo actuators often have their motions amplified by a mechanical device. In fuel injectors they have their motions amplified via hydraulic pressure, they are opening a comparatively small valve, not moving the injector needle directly , f.e. So, as a control mechanism for a larger device, some sort of ram as you're suggesting, maybe. Probably not directly.

J.A.W.
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Re: HCCI

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Could some form of 'activated radical combustion' such as Honda pioneered a 1/4 century ago
play any role here? See: https://dirtbikemagazine.com/when-honda ... -2-stroke/

Either via exhaust gas injected into the combustion, or selected 'radicals' seeded in via the fuel itself?
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saviour stivala
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Re: HCCI

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‘spocom – spontaneous combustion’ is a type of ‘uncontrollable’ combustion that is avoided at all cost by engine designers. Modern formula 1 engine design trends aims to achieve a ‘rapid’ or as fast a combustion as can be short of it being ‘spontaneous’.

johnny comelately
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Re: HCCI

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Plasma (edit- not laser) ignition seems very interesting and somewhat applicable..
https://interestingengineering.com/can- ... ion-engine
Excepting for the fact that the Putin-type useless inhibitory regulation set ban it. Feel better now :wink: