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
107
Joined: 18 Mar 2014, 10:00

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

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Thank you Gruntguru.

Hello all.


The following plot and animation has been added in the http://www.pattakon.com/pattakonPatATE.htm web page.

They show a possible timing for the PatATE with the rotary valve.

Image

Image

The same animation at slow motion is at http://www.pattakon.com/PatATE/PatATE_R ... g_slow.gif

Thanks
Manolis Pattakos

manolis
107
Joined: 18 Mar 2014, 10:00

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

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Hello all.

I hope it is clear that the rotary valve is not dealing with the sealing of the combustion chamber.

The piston with the piston rings that slide on the (stationary) cylinder liner do the sealing as in the conventional two-strokes.

The rotary valve is arranged outside the cylinder liner, around the hybrid ports, and needs not tight sealing.
It just controls the flow of the exiting gas and of the entering gas.

In the following animation the rotary valve and the casing are sliced to show how the exhaust and transfer passageways formed in the rotary valve cooperate with the hybrid ports to give asymmetrical exhaust and transfer:

Image

And here looking from the cylinder head (the exhaust passageways are shown by purple color):

Image

If it is not yet clear how it works, please let me know to further explain.

Thanks
Manolis Pattakos

Tommy Cookers
617
Joined: 17 Feb 2012, 16:55

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

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given that this thread is also the home of sleeve-valve enthusiasts - these are imo fascinating reads
http://www.newcomen.com/wp-content/uplo ... assell.pdf
http://forum.keypublishing.com/showthre ... -Centaurus
http://www.pprune.org/archive/index.php/t-356877.html
eg how the sleeves were made round and how they are not really round ? - and handily, Hercules pistons in a Centaurus
eg the (high-detergency) oil controversy

btw Hermes Hercules 773 a 115/145 engine, used 100/130 763 (airforce Hercs 100/130 till the end ?) when BOAC replaced Hermes with Merlin Canadair
c.8000 Hercs made postwar - (most of ?) these and all Cents had (very heavy) bronze heads - were Cents all 115/145 fuel as Brabazon's ?
Cent, Herc and Sabre were certified/used on hotly 1944-fashionable 100/150 fuel but not up-boosted ie no power gain(Merlins & R2800s were of course)
100/150 had over 7 cc of TEL and lots of MMA, and tried high ethylene dibromide (lead scavenger) producing enough hydrobromic acid to eat valve seats
my inside info - TEL scavenger in car fuel was cheapened to ethylene dichloride (producing hydrochloric acid eating exhaust systems)

J.A.W.
109
Joined: 01 Sep 2014, 05:10
Location: Altair IV.

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

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T-C, see here: http://www.wwiiaircraftperformance.org/ ... or-150.jpg

As for wartime service use of150 grade in sleeve valve engines, the British did not employ the Bristol mills in fast aircraft,
- but the Napier Sabre did use the 150 grade, even if it didn't really need it*..
( esp' since the power available, at still quite modest boost levels - was overstressing the big 14' diameter DH propellers)..

* Wilkinson lists the highest rated production Sabre 7 output as 3,500 hp for take-off (@+20lb 'wet' boost) - on 130 grade..
"Well, we knocked the bastard off!"

Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).

Pinger
9
Joined: 13 Apr 2017, 17:28

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

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Tommy Cookers wrote:
03 Jul 2017, 12:05
given that this thread is also the home of sleeve-valve enthusiasts - these are imo fascinating reads
http://www.newcomen.com/wp-content/uplo ... assell.pdf
Fascinating indeed TC. Thanks. Much appreciated.

J.A.W.
109
Joined: 01 Sep 2014, 05:10
Location: Altair IV.

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

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Some good stuff there*, but it is surely veering the thread a wee bit too far.. off-topic..
& of course.. we do already have.. more suitable threads.. see a couple linked below:

viewtopic.php?f=4&t=20254&start=120

viewtopic.php?f=3&t=24176&start=15


* Some of the ignoramus level opinions proffered by certain forum members on those other links..
..certainly make this forum in general - seem quite learned - by contrast.. & IMO, that's a +ve sign..
"Well, we knocked the bastard off!"

Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).

tok-tokkie
36
Joined: 08 Jun 2009, 16:21
Location: Cape Town

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

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This is all way off topic but picks up on a reference above.

Picking up on the off topic point about the Bristol sleeve valve engines . The linked paper explains the terrible initial problems with the Taurus engine as fitted to the Bristol Beaufort torpedo bomber. My father was in the South African Air Force during WW2. His squadron took part in a little known campaign in Madagascar against the Vichy French. He flew in a Martin Maryland (not used by USA) which served them admirably. However also in the squadron were Bristol Beauforts equipped with those early Taurus engines which kept failing. Since these were naval patrol aircraft my father lost quite a few friends as a consequence.

He kept a diary throughout the war (he died in a training crash in a B-24; he was navigator/bomb aimer). I posted two big extracts from his diary on a local site. One included his anguished references to those engines & 'planes but the site had problems and part of the thread got lost. I later posted the relevant part again in this thread as reply #52 http://www.wilddog.za.net/forum/index.p ... =154071.40

As an interesting side note. The Martin Maryland was ordered by the French & 75 were delivered before France fell to the Germans. The remainder of the order was taken up by the British. Both the British and South Africa ordered additional Marylands. While in Madagascar the Allies only had a small foothold in the north with the Vichy French in control of the rest. A Maryland was sent from France to Madagascar while my father was there, they were alerted to the coming of the aircraft (type unknown) so two Marylands were sent down to the capital Tananariev to shoot the aerodrome up. So it was Marylands sent to get a Maryland. They missed it but my father's plane was downed by a fluke shot - an anti-aircraft bullet on its way back down hit their engine when they were miles away. Plane flew on for a long while but eventually belly landed safely on a beach & the crew had a long (many days) walk back before a MTB was sent to collect them.

manolis
107
Joined: 18 Mar 2014, 10:00

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

Post

Hello all.

Here is the port-map of the famous Vespa 125-150 (57mm stroke)

Image

and here is the port-map of the famous TZR, KR1 and RGV two stroke engines:

Image


The height of the exhaust port is more than double than the height of the transfer ports in all cases.

The timing is symmetrical, say as in the plot in the middle:

Image




Quote from the bottom of the http://www.pattakon.com/pattakonPatATE.htm web page:

In the following version of the PatATE the rotary valve spins at half crankshaft speed:

Image

The width (along the periphery of the cylinder) of each hybrid port (there are two) is 90 degrees.

The duration of the hybrid ports is 180 crank degrees (the piston starts opening the hybrid ports at 90 degrees before the BDC and closes them at 90 degrees after the BDC).

There are two intake ports.

In the following graph it is shown the Exhaust Ports area and the Transfer Ports area versus the crank angle:

Image

End of Quote.


Compare the heavily asymmetrical port timing plot of the PatATE with the previously presented symmetrical port timing of the typical 2-stroke.

Thanks
Manolis Pattakos

J.A.W.
109
Joined: 01 Sep 2014, 05:10
Location: Altair IV.

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

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Hi Manolis, your asymmetric design is of interest.. & best wishes on successful realization of it 'in metal'.

..but do note, the 'sporty' road going designs you showed as 'port maps' - do indeed feature 'variable' timing/valves..
..on both inlet & exhaust processes..
"Well, we knocked the bastard off!"

Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).

manolis
107
Joined: 18 Mar 2014, 10:00

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

Post

Hello all.

The patent US9,695,739 was granted by the USPTO for the PAtATi a couple of days ago.

It is available at http://patft.uspto.gov/netacgi/nph-Pars ... /9,695,739

Thanks
Manolis Pattakos

manolis
107
Joined: 18 Mar 2014, 10:00

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

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Hello J.A.W.

You write:

“your asymmetric design is of interest.. & best wishes on successful realization of it 'in metal'.”


Thank you.

The following version seems the fittest for realization in metal.

It has the typical arrangement, with one only hybrid port “looking” forwards and one intake port at the back of the engine.

Image

The width of the hybrid port along the periphery of the cylinder liner is nearly 180 degrees.
The duration of the hybrid port is 180 crankshaft degrees:

Image

The port at the lower side of the (red) rotary valve, in cooperation with the (blue) piston, controls the intake port of the engine:

Image


The rotary valve (red) rotates at crankshaft speed (1:1).

The exhaust port side:

Image

The intake side:

Image


The Exhaust Ports area and the Transfer Ports area versus the crank angle:

Image

Is as in the version with the half-speed rotary valve and the “double” ports.


According this plot, the variable exhaust and intake of the conventional two-strokes seem as not necessary for the PatATE because it separates the cycle in a “4-stroke-like” way:

after the expansion it follows a rapid opening of the exhaust port and the pressure drops quickly,

then the transfer opens progressively with the exhaust still opening,

then the exhaust starts progressively to close with the transfer opening more and more,

then the exhaust closes with the transfer being still widely open,

finally the transfer closes and the compression starts.

Its operation is closer to a 4-stroke with extreme valve overlap (say, as the Cosworth DFV with the 116 crank degrees valve overlap) than to a conventional 2-stroke.

Thanks
Manolis Pattakos

Pinger
9
Joined: 13 Apr 2017, 17:28

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

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manolis wrote:
07 Jul 2017, 19:07


finally the transfer closes and the compression starts.
Starts with the cylinder only half full as the other half of the charge blew back down to the crankcase.

How do you avoid the above happening?

manolis
107
Joined: 18 Mar 2014, 10:00

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

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Hello Pinger.

You write:
“Starts with the cylinder only half full as the other half of the charge blew back down to the crankcase.

How do you avoid the above happening?”


And why to avoid this?

It is a kind of Atkinson – Miller cycle that happens automatically at lower rpm, say as happens in the 4-stroke engine of the Toyota PRIUS.


Compare the PatATE with a conventional 2-stroke when both operate at low revs offering to the charge plenty of time to:

“blew back down to the crankcase” in the case of the PatATE,

or to:

“blew towards the exhaust (which remains widely open for several crankshaft degrees after the closing of the transfer) in the case of the conventional 2-stroke.


This explains how the PatATE can be substantially greener and more fuel efficient.

Thanks
Manolis Pattakos

Pinger
9
Joined: 13 Apr 2017, 17:28

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

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Fair enough Manolis if that is your chosen strategy, I guess we have slightly different perspectives on this.
I've never been sold on the Miller/Atkinson theory (seeing double handling of air as being a waste of fuel given the extra pumping required) but achieving an expansion ratio greater than compression ratio has validity, at least for a 4T with exhaust valve opening relatively late in the expansion stroke.

With 2T exhausting much earlier, the lateness of transfer closing to achieve the M/A cycle is leaving the cylinder so short of charge as to seriously hamper torque production. If, as you state, this is only at low rpm then a more flexible transmission becomes essential and the compression ratio if adequate at low rpm may be perilously high at higher rpm (unless the reduced tendency toward detonation at higher rpm counters this).

Agreed, losing charge back to the crankcase is infinitely preferable to losing it to the exhaust port but if the torque is so reduced (and will it not be so at higher rpm - inertial effect has its limits against pressure differentials) then merely reducing the charge delivered yields a much simpler engine for the same torque/power output, as flowing less gas permits a smaller exhaust port with more conservative timing - that in itself a step toward reduced charge loss. That the engine is larger with greater friction and heat loss is a compromise to be accepted if incomplete cylinder filling is the chosen strategy.

Just my thoughts. Feel free to argue against them!

gruntguru
563
Joined: 21 Feb 2009, 07:43

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

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Pinger wrote:
07 Jul 2017, 19:57
manolis wrote:
07 Jul 2017, 19:07
finally the transfer closes and the compression starts.
Starts with the cylinder only half full as the other half of the charge blew back down to the crankcase.

How do you avoid the above happening?
I would assume the degree of "overlap" would be chosen to match the rest of the engine ie power band requirement, "wave tuning" design of exhaust, transfer and inlet systems etc.

The numbers suggested by Manolis suggest a "peaky" (racing?) or small displacement engine.
je suis charlie

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