The Bucket Foundry

[WilDun]

Can't wait to hear the difference.

Are you flying the gyro now?

I was CoC at a Ruapuna meeting back in the 90's when a guy turned up with a homemade CDI ignition....we lost all the radio links when he fired it up.
If it hadn't failed in short order, I suspect we'd have heard from Civil Aviation as the approach path to Harewood that day was right over the top of us....

Grumph, you forgot to tell us who the guy with the rouge CDI was - but I guess we'll never know!

[speedpro]

You got it Will. Pulled the engine apart today to clean the debris out of the crankcase and reeds etc. Reassembled with new pistons, already to run up tomorrow with the my CDI fitted. Just spent some time securing the capacitors to the CDI board so vibration doesn't cause problems. Can't wait to hear the difference. Probably need to line the inside of the box it lives in with lead sheet so all the radios at Matamata airfield don't stop working when my engine is running.

Early on running my bucket at Whenuapai with the CDI I had "enquiries" from the control tower. The usual suppression stuff sorted it. I think it was the super quick rise time of the ignition which resulted in a lot of RFI over a broad spectrum

[Grumph]

Grumph, you forgot to tell us who the guy with the rouge CDI was - but I guess we'll never know!

No idea who it was - faces came and went. Memory says it might have been a Ducati - so the failure we welcomed might not have been the ignition....

It was an early CAMS day I think - but they've always welcomed everything else to their meetings as it's more $$ to offset costs.
In the past I've run meetings for CAMS and Canterbury before they became MCI.

[Flettner]

Un bloody believable, two lots of similar wires emmiting from my CDI, hooked the wrong set to the 12V supply, now the trigger circuit dosent work! How hard can it be to just make a twostroke twin ignition work?
Clearly out of my ability. Time for professional help I think.
That HCCI engine is looking better all the time.

[WilDun]

That HCCI engine is looking better all the time.

Yeah, then all you'll need is an old B&S ignition or similar, just to get it all going and then forget ignition! but maybe that's over simplifying it?.
Problem then will be the necessity for variable compression (to keep timing right)? also an electronically operated system for that (another even bigger hurdle!) - no free lunch! ...... never ending!

[Flettner]

no, my HCCI has no spark plug or electric ignition system at all, not even for start.
just a timed compression rise, perhaps a little pre heat.

[WilDun]

So in HCCI, how can you get it to ignite at the optimum time (ie not too early or too late, isn't that controlled by compression? or is it controlled by direct injection timing? (as in diesels) - will this completely rule out carburettors then?
Not trying to be a smartass you understand, .... but what is a timed compression rise? - I haven't been following it closely so not quite up with understanding it all, I'm genuinely interested though!

[Flettner]

https://youtu.be/TOHKls3Cxjs

See this Will, small piston is at twice engine speed and timed. Rapid compression rise just as the big piston rocks over tdc.

[speedpro]

A HCCI engine doesn't need a spark prior to TDC to allow for turbulence to propogate the flame front burning all the fuel and raising pressure at the more or less appropriate time, or some small period.
With HCCI there is no flame front, no progression. The lot catches fire at the same time, give of take.

I think.

[WilDun]

A HCCI engine doesn't need a spark prior to TDC to allow for turbulence to propogate the flame front burning all the fuel and raising pressure at the more or less appropriate time, or some small period.
With HCCI there is no flame front, no progression. The lot catches fire at the same time, give of take.

I think.

Yes I just came in to shut down my computer and found these replies and haven't yet read all Neil's stuff.

SPEEDPRO (forgot your name)
I already understood the instantaneous combustion part but I hadn't (haven't) yet got the part where it decides to combust or what makes it combust - I mean it can't just be allowed to do that at any old time it decides is suitable! like the little model aircraft diesels, eg maybe long before TDC. (that would make it very inefficient and destructive!) and I'm sure that something has to change to suit each different condition it encounters - that's what I'm trying to find out.
NEIL,
No doubt when I've read and absorbed your post I'll be a little bit wiser! - I need to think about the double speed of the little O/H piston - I don't think it would last too long at "Ryger" main crank speeds (30,000 X 2)! - but you've got an experimental one working at least, so I can't argue with that!- it's still just an embryo with me and I really hope it doesn't remain just that!

[Frits Overmars]

Problem then will be the necessity for variable compression (to keep timing right)? also an electronically operated system for that (another even bigger hurdle!) - no free lunch! ...... never ending!

Will, you don't need a variable compression ratio to control the onset of HCCI combustion. Varying the amount of residual exhaust gases in the cylinder is another possibility that the auto factories are experimenting with. They call it Intelligent Exhaust Gas Recycling, although for a two-stroke I'd rather call it Exhaust Gas Retention (intelligent goes without saying for a two-stroke) .

So in HCCI, how can you get it to ignite at the optimum time (ie not too early or too late, isn't that controlled by compression? or is it controlled by direct injection timing? (as in diesels)

The fundamental difference between HCCI and diesels is the Homogeneous Charge Compression Ignition. Diesels have everything except the homogeneous charge.
The optimum timing is controlled by pressure x temperature.

I need to think about the double speed of the little O/H piston - I don't think it would last too long at "Ryger" main crank speeds (30,000 X 2)!

Don't think revs - think piston speed. With the short stroke of Flettos agitator piston the revs need not be a problem. Come to think of it: don't think Ryger either .

A HCCI engine doesn't need a spark prior to TDC to allow for turbulence to propogate the flame front burning all the fuel and raising pressure at the more or less appropriate time, or some small period. With HCCI there is no flame front, no progression. The lot catches fire at the same time, give of take.
I think.

You think right. But a little turbulence can't hurt; not for the purpose of flame spreading but to improve the homogenity (does that word exist?) of the charge.

[Niels Abildgaard]

Will, you don't need a variable compression ratio to control the onset of HCCI combustion. Varying the amount of residual exhaust gases in the cylinder is another possibility that the auto factories are experimenting with. They call it Intelligent Exhaust Gas Recycling, although for a two-stroke I'd rather call it Exhaust Gas Retention (intelligent goes without saying for a two-stroke) .

The fundamental difference between HCCI and diesels is the Homogeneous Charge Compression Ignition. Diesels have everything except the homogeneous charge.
The optimum timing is controlled by pressure x temperature.

Don't think revs - think piston speed. With the short stroke of Flettos agitator piston the revs need not be a problem. Come to think of it: don't think Ryger either .

You think right. But a little turbulence can't hurt; not for the purpose of flame spreading but to improve the homogenity (does that word exist?) of the charge.

Turbulence gives higher heat tranfer to and from engine and this is unwanted.

[Frits Overmars]

Turbulence gives higher heat tranfer to and from engine and this is unwanted.

That's right Niels. Turbulence prevents areas in the combustion chamber from remaining so rich that they won't encounter sufficient oxygen in time (lean areas are no problem for HCCI). We do want to burn every molecule of fuel, but as you point out, we do not want to loose that combustion energy to the surrounding metal.
It would be good if we could stirr up the mixture before it enters the cylinder. A crankshaft in a two-stroke crankcase does a wonderful job at it. But then we'll have oil in the mixture. No free lunch...

[speedpro]

A turbocharger would do it.

[WilDun]

.......It would be good if we could stirr up the mixture before it enters the cylinder.......

Must say I am learning fast! - taking in information like a grounded boat takes in water - can't stop it!

So where the hell do I start ?

Frits - what you said in that line has got me delving through my (documented) thoughts again! - I came up with an idea on that, possibly way out, but I believe in it. I think that I may have briefly mentioned it to you in an earlier post somewher.
It's all done in my usual haphazard, non scientific way and is really an ongoing thing - definitely unfinished.........

I had hoped to try it out but as only Neil knows I am severely cramped at home, I'm running out of time, not all that fit anymore and being gently coerced into geting rid of my workshop to become a normal person living inside the square!
So just in case that terrible day might come sooner than expected, I decided to gather up and document some of my thoughts, based on my limited knowledge of this HCCI engine stuff, (more hunches really) - some sensible, some downright cuckoo, but all done to the best of my knowledge and ability, hoping like hell that someone else could be interested enough to make use of it by actually trying it, or who might at least be able glean some inspiration from it.

I didn't really have the courage to talk anyone about it. - I didn't want it to become a non event nor did I want to be exposed to ridicule (all a bit sad, but this has happened to some previously successful people recently, when they appear to have got things wrong!) - but I don't know all the details of why that happened or what has been going on behind the scenes there of course.

Don't really know what to do - need to think about it .