2 stroke thread (with occasional F1 relevance!)

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Wed Jan 10, 2018 6:03 am

Hello all.

Back to the PatBam HCCI

The worst drawback of the PPE (Pulling Piston Engine, more at http://www.pattakon.com/pattakonPPE.htm ) was considered the thin (it can be thin because it is heavily loaded only in tension) “piston rod” in the combustion chamber (through this “piston rod” the piston is connected to the wrist pin):

Image

Looking at the big diameter “column / post / pillar” in the combustion chamber of the Cox Design (funded with several millions so far, some from the GB MoD and considered as a promising innovation by the “Ricardo” which took part in the project):

Image

we have to reconsider: a “piston rod” in the center of the combustion chamber is OK.

Bellow are two PatBam HCCI designs using “piston rod” in the combustion chamber.

The PatBam HCCI PPE (spot on the size and location of the reed valve):

Image

Image

and a conventional 2-stroke (say, like the euro4 compliant KTM 250/300EXC/2018) easily modified to PatBam HCCI:

Image

Thanks
Manolis Pattakos

Pinger
8
Joined: Thu Apr 13, 2017 4:28 pm

Re: 2 stroke thread (with occasional F1 relevance!)

Post by Pinger » Wed Jan 10, 2018 10:26 am

manolis wrote:
Wed Jan 10, 2018 6:00 am


I hope it is clear now that a 2-stroke can be turbocharged and supercharged heavily, at a degree similar to that of the 4-strokes.
'A very brief period' - in time.

Comparing an engines running at 80 rpm and 4000 rpm is hardly valid when the issue is charging time. The W has 50 times the time available to the Cox.

manolis wrote:
Wed Jan 10, 2018 6:00 am
You also write:
“Until the pistons melt.....”

A Diesel runs from lean to extremely lean.

The temperature of the piston and of the exhaust gas are substantially lower than in a spark ignition / stoichiometric engines.

With the intake cycle pressure and the exhaust cycle pressure shifted by some 20%-30%, the temperatures are not for melting the pistons.
True, combustion is cooler in CI - but then it is much more prolonged and the turbulence (which promotes heat loss) much more pronounced.
Cooler EGT is more due to the greater expansion that lower combustion temp.

Pinger
8
Joined: Thu Apr 13, 2017 4:28 pm

Re: 2 stroke thread (with occasional F1 relevance!)

Post by Pinger » Wed Jan 10, 2018 10:32 am

manolis wrote:
Wed Jan 10, 2018 6:03 am
Looking at the big diameter “column / post / pillar” in the combustion chamber of the Cox Design (funded with several millions so far, some from the GB MoD and considered as a promising innovation by the “Ricardo” which took part in the project):
That 'post' running through the chamber wouldn't be my first choice either. But in Cox's defence, they are claiming excellent reliability/durability so presumably it doesn't impinge on those aspects. Also, Ricardo was of the view that the swirl necessary for CI combustion when achieved with a uniflow scavenging pattern left a core of residual exhaust products at the centre of the cylinder at high delivery ratios. The 'post' then is merely occupying what would be a dead zone anyway.

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Thu Jan 11, 2018 6:15 am

Hello Pinger.

You write:
“'A very brief period' - in time.
Comparing an engines running at 80 rpm and 4000 rpm is hardly valid when the issue is charging time. The W has 50 times the time available to the Cox.”


Since the Wartsila X92 is a slow revving 2-stroke (yet it is not if you consider its piston speed (similarity); at 76rpm the mean piston speed is: 3.468*2*76/60=8.8m/sec),

here is a high revving turbo 2-stroke:

Image

Quote from https://www.youtube.com/watch?v=Oxj_OAb5bqk



125cc Turbo - Original TZR125 twostroke turbocharged by Boostbusters

Comment from Cooknasty300:

So how do you compensate for the scavenging effect of the 2 stroke? The sound wave pushes the unburned fuel back into the cylinder, but with a turbo, there would be a constant one-way vacuum which would disable this necessary effect in theory am I right?

and reply by Tyson James:

The pipe still works fine as the pressure wave is reflected back up the pipe like it is designed. The difference is with the turbo there is more exhaust backpressure as you are pushing a greater volume of air through the same size pipe then using it to drive the turbine wheel. If you watch the dyno pull when it spools up you see the exhaust pipe start stretching the springs at the manifold from the added pressure. So yes the intake charge blows in the chamber at a greater pressure but the exhaust pressure is also higher. 2 strokes love boost

End of Quote


Spot on where the turbocharger is located.

At 11,000rpm, the high revving small (50mm stroke) TZR125 has a mean piston of:
0.05*2*11,400/60=19m/sec, which is only double than the mean piston speed of the low revving Warsila X92 (by the way, at the 8.8m/sec mean piston speed the Wartsila X92 can work continuously at full load for weeks).



You also write:
“That 'post' running through the chamber wouldn't be my first choice either. But in Cox's defence, they are claiming excellent reliability/durability so presumably it doesn't impinge on those aspects.”


Suppose it is so, i.e. the Scotch Yoke of Cox engine offers excellent reliability.

Isn’t it strange that they don’t use it in a conventional 4-stroke engine (as CMC did a decade ago) replacing the typical “connecting-rod / wrist pin” mechanism?

Why to limit it to an unconventional design?

More reasonable is that they try to justify the increased friction and the reliability issues of their Scotch Yoke by the unquestionable compactness of the design. This is their basic advantage: a compact and lightweight design for outboard Diesels (not a design that offers better fuel efficiency).



You also write:

Ricardo was of the view that the swirl necessary for CI combustion when achieved with a uniflow scavenging pattern left a core of residual exhaust products at the centre of the cylinder at high delivery ratios. The 'post' then is merely occupying what would be a dead zone anyway.”


The question is whether the unavoidable increase of the cylinder wall surface and the added sets of piston rings are justified by the decrease of the core of residual exhaust products "because the post occupies their place". But let me doubt.

In any case, if Ricardo is right, the PPE engine:

Image

Image

can use as thick post as required "to not leave space" for a core of residual gas in the cylinder.



By the way, here is another version of the PatBam HCCI on a 2-stroke:

Image

The “cage” keeps the ring of the auxiliary piston in place all the time, and allows good scavenging everywhere.

Thanks
Manolis Pattakos

peppo
0
Joined: Thu Jan 11, 2018 10:01 pm

Re: 2 stroke thread (with occasional F1 relevance!)

Post by peppo » Thu Jan 11, 2018 10:10 pm

Hello.
this is the solution I studied... bearings in the video are not like those which would be on the real engine (haven't patented the bearing solutions so don't show it)... but the whole thing is made to be compact and symmetric, rods encumbrances in scavenging chambers behind pistons may give the right depression to achieve atkinson cycle.
Please let me have your comments... or contact for anybody who could fundraise [-o<

https://www.youtube.com/watch?v=MPW1FtV64ac

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Fri Jan 12, 2018 10:06 am

Hello Peppo.

You write:
“Please let me have your comments.”


A few thoughts / questions / comments on your design:

Image

In the above drawing, at left, they are shown two pairs of conical rollers per piston. The one pair is rotatably mounted on the piston, the other pair is disposed between the immovable casing and the rotating big gearwheels (those with the circular-wave- tracks) to receive the axial loads.

Is the hatching correct? (as it is now, the rotating gearwheel is like being a part of the casing; shouldn’t its hatching be at a different angle or density, to distinguish it from the casing?).

The two conical track-roller-bearings on each piston are cooperating with a pair of facing each other circular-wave-tracks.
What happens when the force between the piston and the circular-wave-tracks changes direction?
Doesn’t each conical track-roller-bearing have to change –instantly- direction of rotation?
Reasonably, each piston should have two pairs of conical-track-roller-bearings (preloaded between the two trackways), the strong one running on the outer circular-wave-track, the other running on the inner. To keep the height low, the second pair of conical-track-roller-bearings can be disposed at, say, 90 degrees from the other pair.

The piston assembly seems lightweight in the drawing.

But the loads are heavy and the revs the conical-track-bearings operate are high. Are there such high-revving and strong track-rollers in the market?

Judging from the size of the cylindrical-track-roller-bearings of the Revetec engine (which, as the Bourke engine, failed to operate reliably for longer than a few minutes because of the extreme local loading at the line-contact between the track-roller-bearings and the track-ways):

Image

Image

Image

it seems that substantially oversized conical-track-roller-bearings are required in your design, which leads to substantially bigger in diameter circular-wave-tracks.

In the Cox Scotch Yoke design (previous posts) they use “surface” contact, which has the highest loading capacity in expense of frictional loss.

In the Revetec design, there is, permanently, a linear contact between the track-roller-bearing and the track-way, while each track-roller-bearing rotates permanently at the same direction (yet, at variable speed, which is still a big problem), allowing rolling without sliding (at least at the lower revs; at the medium - high revs the cylindrical-track-roller-bearings of the Revetec and of the Bourke cannot help sliding (besides rolling) on the track-way; to cure this problem mce-5 used the following solution:

Quote from http://www.mce-5.com:

Image

The synchronized roller is largely responsible for the low-friction performance of the MCE 5 VCRi

Image

The MCE 5 VCRi synchronized roller cooperates with 3 synchronization racks: two of them are on a plate fixed to the crankcase while one is on the back side of the piston rack

End of Quote

despite their synchronized track rollers, and despite the 100 million euros, or so, funded to mce-5 VCRi, they now appear as closed / bankrupted: in their web site the “latest news” are from 2013).


In your design, is it possible to keep permanently at least “linear contact”? (and not turn it, at some parts of the track-ways, to “point-contact”?). To take the combustion loads with “point contact” is highly questionable (from the reliability viewpoint).

To put it differently: how the conical-circular-track-ways are designed?
If the track-way is conical (zero stroke of the piston), then the conical-track-roller-bearing rolls on the track-way without sliding and keeps - permanently - linear contact.
But if you add a significant axial displacement (piston stroke happening into 90 degrees of totation of the track-way) the complete track roller bearing displaces linearly along the cylinder axis, causing the sliding between the cooperating "conical" and "wave conical" surfaces.


Secondary “issues”:

Doesn’t the piston at the exhaust side need a skirt to cover the exhaust ports when the piston is near the TDC? Even if the bottom of the cylinder is closed / sealed, the exhaust hot gas will return at the space underside the exhaust-piston.

Where the power is provided from? The synchronizing shaft, at left, is not extending out of the casing.


Don’t get me wrong.
I am just trying to help.
As an independent third party, I point on possible issues you may find in practice.

If anything I wrote is confusing please let me know to further explain.

Thanks
Manolis Pattakos

peppo
0
Joined: Thu Jan 11, 2018 10:01 pm

Re: 2 stroke thread (with occasional F1 relevance!)

Post by peppo » Tue Jan 16, 2018 5:29 pm

Dear Manolis,
I am thankful for your attention and your reply which is pretty keen. The fact is, my patent just protects the kinematic configuration of that engine so that those drawings must depict the motion functions of the main pieces the most simply possible.
As you may see in the attached video, I continuously update its design (double conic rollers and side skirts on pistons are well visible in other pictures I already made), and lately I also figured out some special features likely to be included in a perfecting patent, then I cannot draw them yet.
I made the first calculations and the thing seems just feasible. The problem is just my lack of time because I must work, and of money to keep this patent and make others... So I need partners, but have no good contacts so far.
I am working now, when I have a minute at home I'll attach here other drawings.
Thank you again for your interest.