The Bucket Foundry

[Flettner]

Lot of talk in F1 Technical about HCCI being used this year (and last year by some). Is it real? How is it achieved? I've read it's a composite system with spark ignition still used at part of the rev range. If you are to belive what is written, Renault has just come on board with it's system recently, suddenly they seem to have some power. I couldn't care less about F1 but it is interesting talk never the less. Anyone else heard anything?

[Muciek]

I have read it at Mat Oxley blog this morning and I was about to post it. They talk about sound change when hcci kicks in.

[Flettner]

I have read it at Mat Oxley blog this morning and I was about to post it. They talk about sound change when hcci kicks in.

Yes, please post it, thank you.

[Muciek]

Here it is but not very much to read http://www.motorsportmagazine.com/f1/f1s-power-secret/

[husaberg]

Lot of talk in F1 Technical about HCCI being used this year (and last year by some). Is it real? How is it achieved? I've read it's a composite system with spark ignition still used at part of the rev range. If you are to belive what is written, Renault has just come on board with it's system recently, suddenly they seem to have some power. I couldn't care less about F1 but it is interesting talk never the less. Anyone else heard anything?

I wonder if that ties in with fuel octane rating becoming utterly irrelevant at very high revs. (like 15:1 and higher comp on 80 octane petrol)
Honda did a lot of work on that in the 60's, I can't be bothered finding it, but Kevin Cameron wrote a fair bit about in in various books.

All bets are off when you try to run it at low revs under load though, pretty sure Nascars and Indycars can't do that either though.

[Frits Overmars]

Here it is but not very much to read http://www.motorsportmagazine.com/f1/f1s-power-secret/

It is believed the dome of each piston has an extension in its centre, fitting into a recess within the combustion chamber. Within this ‘chamber within a chamber’ the mixture is compressed to the point of spontaneous ignition

How do you guide an extension of a forward-rearward-rocking main piston into that recess? And what's more, since this extension has to generate some proper pressure, it will need to have a piston ring as well, either moving with the extension or stationary in the recess. That would aggravate the guidance problem tenfold.

When in conventional spark plug mode either the upper chamber is not fed with fuel or the extension in the piston is a ‘plunger’ type that can be extended or withdrawn.

A movable plunger upon a fast-moving piston? Unlikely.

HCCI engines promise not only a better fuel economy/performance trade off but also much lower NOx emissions, because the higher temperatures created by the compression ignition produces less soot.

HCCI generates less NOx because the temperatures are lower, not higher. And HCCI generates less soot because it can work with an oxygen surplus that would make the mixture too lean for a flame to spread. HCCI doesn't need flame spreading; there is no flame front, as the burning starts simultaneously all over the combustion chamber.

This is also the second reason for low NOx: the mixture is completely consumed in about one tenth of the time it would take with spark ignition, so the N2 and O2 molecules that would merge into NOx, given sufficient temperature during sufficient time, are exposed to combustion heat during a much shorter period of time.

They talk about sound change when hcci kicks in.

Now that sounds familiar . It was one of the most striking impressions during my first acquaintance with HCCI.

[Grumph]

A lot of that doesn't add up as Frits has said. If they're cutting fuel to that part of the combustion chamber I'd see this as inferring direct injection to the chamber...Which I thought was still banned.
When Gordon Blair was out here to give a lecture some years back, he described F1 combustion chambers then as a sheet of paper with four deep pockets for the valves which he thought was where the combustion took place. IE to get the compression they needed the chamber was mostly squish area.
I can certainly see an area around the central plug being shaped as described, whether the clearances needed to avoid metal to metal contact would be small enough to make it work like Flettner's jockey piston I don't know...

[Drew]

If the insert thingie was a taper, could they calculate the exact amount of conrod stretch and where the magic flash point starts to occur?

[Frits Overmars]

If the insert thingie was a taper, could they calculate the exact amount of conrod stretch and where the magic flash point starts to occur?

Maybe it would work if the insert thingie was a flintstone

[Drew]

So the consensus among everyone is that this isn't something that is practiced?

[ken seeber]

Drew,
My thoughts are that there is no chance of any type of protrusion of the piston entering a recess in the head to provide some form of a separate higher pressure chamber. The incredibly short current performance 4 stroke pistons have an L/D ratio is such that the piston could be easily tilt either way, kicking the protrusion over way more than the small clearance needed. Plus, the protrusion would inevitably run much hotter than the head (and its secondary chamber bore) so its size and fit into the head would be very hard to control or even predict.
And also, even if it did work, what about the operation when HCCI wasn’t active? I don’t think any combustion chamber in an SI engine would like to have a big hot dick in the middle, interrupting the combustion process and also if the plug was in the centre of the head, it’d be in the middle of the supposed HCCI chamber, sealing off the rest of the remaining annular charge.
Gotta be something else in my opinion.

[Drew]

Mibbee they just rely on revs and red hot exhaust valves the same as drag cars?

[Ocean1]

Drew,
My thoughts are that there is no chance of any type of protrusion of the piston entering a recess in the head to provide some form of a separate higher pressure chamber. The incredibly short current performance 4 stroke pistons have an L/D ratio is such that the piston could be easily tilt either way, kicking the protrusion over way more than the small clearance needed. Plus, the protrusion would inevitably run much hotter than the head (and its secondary chamber bore) so its size and fit into the head would be very hard to control or even predict.
And also, even if it did work, what about the operation when HCCI wasn’t active? I don’t think any combustion chamber in an SI engine would like to have a big hot dick in the middle, interrupting the combustion process and also if the plug was in the centre of the head, it’d be in the middle of the supposed HCCI chamber, sealing off the rest of the remaining annular charge.
Gotta be something else in my opinion.

So add some depth to the piston skirts, make the protrusion a cavity, (cylindrical bore) and put the protrusion, (a small piston) in the head.

Control protrusion depth with a cam running at engine revs, possibly variably timed to manage combustion timing.

Or use a solenoid so you can also turn it off at "normal" combustion speeds.

[Flettner]

Mibbee they just rely on revs and red hot exhaust valves the same as drag cars?

Maybe there is more to that than just an idea. If combustion chamber was under the exhaust valves, squish averywhere else, then as the valves get hot with load, so auto combustion will occur.

[Ocean1]

Maybe there is more to that than just an idea. If combustion chamber was under the exhaust valves, squish averywhere else, then as the valves get hot with load, so auto combustion will occur.

Wouldn't be HCCI then, would it?

Be a sort of glow plug.