2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello all.

Quote from https://markwalkermotorcycles.com/ :



Mark Walker:

“In the early 90’s I was travelling back from a Canberra Drag race and pulled into Bundanoon, I met a bloke in the bar, and he asked me what I had in the trailer, I said “My drag bike, a home built 2lt V-Twin” and he was very interested in my work and he happened to mention he was into Hot Rods and he said he had an unusual head at home, he said it had a cylinder in it, rotating and no valves, and I nearly dropped my coffee on the floor because at the time, I was building my own wooden models to build my own rotary valves,

so as you can imagine I was so keen to look at what this piece was,

so I followed him back to this old falling down weather board cottage, the house was chock with car parts and all around the yard and he directed me down to this old shed and he got up on an oil drum and lifted down this head wrapped in a blanket and he unfolded the blanket.

I wasn’t imagining much, but I went wobbly as it was a genuine Dunstan Rotary Valve, made in Melbourne by Dunstan himself, stamped no 29.

This changed my whole concept of cylinder heads, it was a cast aluminium head, water-cooled with a beautifully cast iron rotor cylinder down through the centre of it with slots both sides for the ports and floating bronze seals.



Since that awakening I have learn’t alot about David Dunstan and his heads.

The type of head I am using on Big Ned is a Roland Cross design valve, he started his work in the early 20’s in England.



2 Great Pioneers : Roland Cross and Aspen which you can research yourself.


I have spent my life working on, modifying and building Poppet Valve engines and then converted over to a new religion… “Rotary Valves”. When you realise the advantages of a Rotary Valve over a Poppet Valve are staggering…. They are an addiction.”

End of quote.


Thanks
Manolis Pattakos

[manolis]

Hello wizz33


Qute from http://nautilusengineering.com/nautilus-cycle :







A normal piston with "short" piston skirt (like that shown above) has a lot of tilting and "play".

Any idea on how the extension at the center of the piston crown aligns (as required toprovide sealing) with the hole in the cylinder head?


Here are shown the moving parts of the "cross-head" OPRE prototype engine:



The above parts are inside the engine of the following youtube video:



The engine runs on Diesel fuel (compression ignition) at a 17:1 compression ratio, and stands free on the floor (vibration free).
Only the piston rings, the con-rod big end plain bearings and the fuel injection are from the market.


Even with the cross-head design of the above OPRE engine (which means extra long "piston skirt" and minimum piston play), the alignment of an extension on the piston crown with a hole in the cylinder head is difficult because the required clearance is too small otherwise the pressure difference between the two chambers - the main cylinder and the small cylinder in the head - cannot be significant.

Do I miss something?

Thanks
Manolis Pattakos

[J.A.W.]

Yes Manolis.. the Nautilus & Walker* units appear to be 4T's & your's (quite rightly, thread topic-wise) is - a 2T!

*How has Walker improved upon the fundamentally flawed Aspen/Cross design - to make it viable?
Or are his 'back-yard' builds just 'novelty/folly' - types with no prospect of running long enough - for any practicable TBO?

[wizz33]

in the autoline interviews they mention that there is not much precision needed

[manolis]

Hello J.A.W.

Mark Walker is a different story.

Fortunately, he doesn’t care about the TBO and the number of strokes.

He made 4-stroke poppet valve racing engines:



He made 2-stroke engines:



He made 4-stroke rotary valve engines:




In his Big Ned engine (Cross rotary valve):



Mark Walkers applied the floating cylinder principle of Cross:



according which the high pressure into the cylinder during compression – combustion – expansion pushes the cylinder – cylinder head onto the rotary valve.

With its 3lit capacity, the V-2 Big Ned is in another class of magnitude.


Does it matter the TBO or whether the engine is really functional?


Mark Walker had a dream and worked on it.

We should wish to have more guys like Mark Walker.

Thanks
Manolis Pattakos

[manolis]

Hello Wizz33

You write:
“in the autoline interviews they mention that there is not much precision needed”


Even if “there is not much precision needed” (let me doubt),
I can’t see the advantages,
while some drawbacks are obvious:

like the smaller valves (volumetric efficiency at high revs?),

like the compression-expansion of the mixture inside the cylinder before its ignition (the mixture in the cylinder is initially compressed at a, say, 12:1 compression ratio, then it expands at a, say, 8:1 compression ratio without making any work (actually, this process consumes mechanical work into friction), and only then the combusted mixture in the small chamber enter into the big chamber and ignites the rest mixture),

like the thermal loss when the combusted gas in the small chamber (which is from 1/6 to 1/3 of the total mixture) passes through the slim peripheral opening formed between the extension of the piston and the hole in the cylinder head (it reminds the pre-combustion chamber in the old Diesels), etc.


With a controllable VCR:



(more at http://www.pattakon.com/pattakonVCR.htm )

the compression ratio can be as high as required for the auto ignition of the mixture and the HCCI combustion.


In the one case (Nautilus) we limit the high compression that causes the auto ignition in ~30% of the mixture, in the second case we compress all the mixture to the point of auto ignition.


What makes the divided chamber of Nautilus better and the BTE higher?

Thanks
Manolis Pattakos

[J.A.W.]

Hi Manolis, IMO, while Mark Walker does quite a creditable job of the 'tinkerer's art' - it stands no useful comparison..
..to Uniflow's proven practicable applications, or your own advanced 2T designs, conceptually..

[manolis]

Hello J.A.W.

It seems that besides being a tinker, Mark Walker is a thinker as well.

A long existing problem / drawback of the “Cross floating cylinder design” is how to support the cylinder head on the crankcase and how to receive the thrust loads the piston skirt applies onto the floating cylinder.

With the cylinder head supported on some long stands, things get difficult.

Mark Walker thought a solution: to bridge the two cylinder heads of his Big Ned engine (a V-2 at 90 degrees with Cross rotary valves and floating cylinders) to form a stiff triangle structure.

With the added bridge (the gray pipes from the one cylinder head to the other):



each cylinder head is not left alone to vibrate, and the stands can be thinner.



It takes more than a tinker to make from scratch, with limited resources, a competitive drag racing engine / motorcycle:



Photo above:
Pistons and Rods under Development.



Photo above:
First Crankshaft.
The first Crankshaft was made from Assab Steel. It was 4" Stroke. It had Press in Main Shafts to Flywheel and a Screw up Crankpin with 2 different numbers on threads on each end of the Pin and a 2" Big end Sleeve. The first Barrels were machined from a Caterpiller Liner



Photo above:
Heads Assembled
Cylinder Heads, Conrod, Slipper Piston- machined from 5083 running on teflon buttons, Aluminium Bronze Seats, Stainless Steel Valves, Heads Machined out of 5083, Conrods - 1 in construction due to a backfire cracked the rod - machined from 7075 plate.




And as he says:

“I have spent my life working on, modifying and building Poppet Valve engines and then converted over to a new religion… “Rotary Valves”.

When you realise the advantages of a Rotary Valve over a Poppet Valve are staggering…. They are an addiction.”

Thanks
Manolis Pattakos

[manolis]

Hello all.

Here is the Issue Notice for the patent granted for the PatBox CVT:



by the USA patent Office.

More at http://patft.uspto.gov/ and http://www.pattakon.com/pattakonPatBox.htm



Thanks
ManolisPattakos

[manolis]

Hello all.

HCCI controllable combustion

For 2-stroke and 4-stroke engines.

Prior Art:





Prior art (Nautilus Engineering):






A look at the above plot / example is indicative for the problems of the prior art and for the solutions of the PatBam.

Starting the compression stroke with 1 bar pressure, at 33 degrees before the TDC / 12 bar in the united combustion chamber, the auxiliary combustion chamber is sealed and its pressure rises at 33 bar (wherein the threshold for auto-ignition is) some 14 degrees before the TDC (corresponding to about 2% of the piston stroke).

Then the air-fuel mixture inside the auxiliary combustion chamber auto-ignites and its pressure at the TDC is way higher than the 48 bar of the case without ignition.

The pressure of the air-fuel mixture in the main combustion chamber never exceeds the 29 bar, i.e. it is below the threshold for auto-ignition.

So, after the TDC the air-fuel mixture in the main combustion chamber expands not-yet-burnt until 33 degrees after the TDC, when the two combustion chambers unite into one, with the burnt gas from the auxiliary combustion chamber igniting the not-yet burnt mixture.


With the PatBam things are similar until the auto-ignition of the air-fuel mixture inside the auxiliary combustion chamber.

Then, a little after the auto-ignition in the auxiliary combustion chamber, the auxiliary piston passes over the passageways formed on the inner side of the auxiliary cylinder, allowing the hot (and at high pressure and full of active radicals) burnt gas to enter into the main combustion chamber and ignite it, exploiting all the 11:1 expansion ratio and achieving a high thermal efficiency.























More at from http://www.pattakon.com/pattakonPatBam.htm

Thoughts?

Objections?

Thanks
Manolis Pattakos

[manolis]

Hello all.

PatBam (HCCI) 2-stroke.





In the above two animations the PatBam is applied on a Pulling Piston Engine (PPE, for more: http://www.pattakon.com/pattakonPPE.htm );

the lubrication in the crankcase is 4-stroke;

the design is cross-head;

the piston is not touching the bore (only the piston rings touch the bore and need lubrication; the piston itself does not need any lubrication);

the dead volume of the "scavenging pump" can be variable and can be as small as desirable;

the reed valve (without its petals) is shown inside the bellmouth (at top).

The "piston rod" aligns precisely the auxiliary chamber (formed inside the piston) with the auxiliary piston (secured to the casing).


In a few words, the faster combustion because of the HCCI combines with some 35% slower piston motion around the combustion dead center to achieve a constant volume combustion.


Thanks
Manolis Pattakos

[J.A.W.]

Well done Manolis, with the patents & the (literally) head-turning designs - you present here.

The BRP patent explains its dual injection 2T set-up, I note that they regard it as suited to both
motorcycle usage, & in road-going applications - as well as snow/marine craft.

http://www.google.com/patents/US20170159598A1

[manolis]

Hello J.A.W.

The patent application publication of (Rotax?) – BRP is not yet searched / examine (it is not yet a patent; it may be).


First claim:
“1. A method for controlling a two-stroke internal combustion engine, the engine having at least one combustion chamber, at least one direct fuel injector for injecting fuel directly in the at least one combustion chamber, and at least one port fuel injector for injecting fuel upstream of the at least one combustion chamber, the method comprising: determining a first fuel quantity to be supplied to the at least one combustion chamber; determining a ratio of the first fuel quantity to be injected by the at least one direct fuel injector; determining a ratio of the first fuel quantity to be injected by the at least one port fuel injector; injecting a second fuel quantity in the at least one combustion chamber using the at least one direct fuel injector; injecting a third fuel quantity upstream of the at least one combustion chamber using the at least one port fuel injector, a sum of the second and third fuel quantities being initially greater than the first fuel quantity; and decreasing at least one of the second and third fuel quantities over time such that the sum of the second and third fuel quantities equals at least the first fuel quantity.”



I seems to me that the Examiner can easily reject it for lack of inventive step, because for the “skilled in the art” this method is obvious / reasonable.

Besides, if someone wants to bypass this “method”, he can use injection maps by means of which,
depending on the instant operational conditions (air temp, ambient pressure, lambda sensor, water temperature, etc) and on the “mode” selected (sport, drive, economy, etc),
the ECU decides how much fuel to inject “directly” into the cylinder, and how much fuel to inject “indirectly” in the port.


In any case, the most interesting part of this patent application seems the section wherein the BRP presents the weaknesses / limitations of their own direct injection E-TEC system:

“In recent years, the port fuel injectors have been replaced in some two-stroke engines by direct fuel injectors such as the E-TEC.TM. fuel injector from BRPTM. The direct fuel injectors inject fuel directly into the combustion chambers of the engine. As a result of the use of the direct fuel injectors, the engine performance has improved, even more precise control of the fuel quantity being injected is possible, less oil is used, and the amount of polluting emissions, such as carbon monoxide, has been reduced even more.

Although direct fuel injection has helped improved two-stroke engines, as the demand for even higher performance engines continues, the use direct fuel injectors has some drawbacks. For example, at very high engine speed (RPM), there is a very short period of time during which fuel can be injected and then mix with the air in the combustion chamber. As such, the fuel may not have the time to properly atomized, resulting in larger droplets of fuel being combusted, which emits more soot than when the fuel has properly atomized.

Although some of the above drawbacks could be resolved by switching to a four-stroke engine, (!!!) doing so would result in losing the advantages typically associated with two-stroke engine, namely a simplified construction, more power (two-stroke engines have an explosion in each combustion chamber at every revolution, four-stoke engines at every two revolutions), and a lighter weight. These advantages of two-stroke engines are important features for vehicles such as motorcycles, snowmobiles and other recreational vehicles.”



Regarding the PatBam control over the HCCI combustion in the 2-strokes (animation in the last post),
it is like the Honda EXP HCCI wherein the trapped exhaust gas provides the required “active” radicals for the ignition of the new charge





The radicals in the combustion chamber are like burning coal pieces:



thrown into a forest to put fire.

The active radicals, used in the Honda EXP for the ignition of the trapped fresh mixture, were created a crankshaft rotation earlier, during the last combustion.
After the combustion they were cooled and “exhausted” (during the expansion, exhaust, scavenging and compression).
Even “semi dead”, they do fire the fresh charge


In the PatBam the radicals are created a few (say 10) degrees before the TDC in the auxiliary chamber and immediately after (still before, or at, the TDC) they bust into the compressed – hot air-fuel in the main chamber.


A characteristic of the PatBam is that the auxiliary chamber starts communicating with the main chamber just before the TDC, i.e. before any expansion in the pre-chamber (expansion means temperature drop).
Even if the HCCI combustion in the auxiliary chamber ends some 5 - 10 degrees before the opening of the “transfer ports”, after its combustion the burnt gas is further compressed; the compression tends to further rise the gas temperature, while the pre-chamber walls have not too much time to cool it down.
At the same time the mixture in the main chamber is further and further compressed, warmed and prepared to receive the active radicals from the auxiliary chamber just before the TDC.
The high pressure in the auxiliary chamber causes the penetration of the highly active radicals deep into the hot / compressed air-fuel mixture in the main chamber, triggering its HCCI combustion.



By comparison,
in the prior art (Chatterton, Roberts, Nautilus, etc) after its combustion in the pre-chamber, the burnt mixture undergoes a significant expansion: the volume in the pre-chamber over-doubles;
supposing adiabatic expansion in the pre-chamber, the absolute temperature of the burnt gas drops by more than 25% ((1/2)^0.4=0.75), say from 1700 degrees Celsius to only 1200 Celsius;
taking also into account the cooling affect of the surrounding pre-chamber walls (worth to mention here the longer time the gas stays in the pre-chamber after its combustion), when the two chambers eventually start communicating, the radicals are “semi-dead” (a big damage for the rest cycle) and the pressure is low reducing the penetration capability of the gas stream with the “semi-dead” radicals into the unburned mixture of the main chamber.
At the same time another “damage” is taking place in the main chamber wherein the compressed / warmed air-fuel mixture undergoes a significant expansion / cooling before the entry of the “radicals” from the pre-chamber: the temperature drop is more than significant; the absolute temperature of the air-fuel mixture in the main chamber drops by some 25% at the 33, or so, crankshaft degrees at which the two chambers unite (wherein the volume doubles with reference to the dead volume); a (main chamber) temperature drop from 630 deg Celsius at the TDC to only 400 deg Celsius when the two chambers start communicating makes the controllable HCCI difficult, if possible.

According the previous theory, with the PatBam things improve “square” relative to the prior art: way more active radicals penetrating way deeper into the main chamber wherein the conditions are way better for HCCI combustion.



Here is the TJI of Mahle:










and here are some characteristics that distinguish the two systems from each-other, the Mahle TJI and the PatBam.

1.
The Mahle TJI requires a high pressure / high tech injector to directly inject a small quantity of fuel into the pre-camber.

The PatBam needs not direct injection. Not even an injection system. Even with a carburettor it would work, because it’s ignition is tolerant to the air-fuel ratio in a wide range.
Think of it as an add-on, that replaces the spark plugs of old carburetted engines and how much the emission would drop.

This makes the PatBam cheaper and simpler.

2.
The Mahle TJI requires a high voltage ignition system to put fire onto the “rich” air-fuel mixture in the pre-chamber.

The PatBam needs not a high voltage system, nor spark plugs. The high compression inside the pre-chamber causes the auto-ignition of the lean mixture therein (HCCI).

This makes the PatBam not only cheaper and simpler but also more reliable (think of an airplane engine wherein they use now two independent ignition systems and two spark plugs per cylinder, for safety).

3.
In the Mahle TJI pre-chamber, the combustion takes place at low pressure with the pre-chamber communicating permanently with the main chamber.
The spark plug ignites the rich mixture in the pre-chamber, and as the flame expands, it pushes a good part of the still un-burnt mixture from the pre-chamber, through the permanently open ports (orifices), into the compressed lean air-fuel mixture in the main chamber.

In the PatBam a little after the auto-ignition of the lean mixture inside the pre-chamber, the ports / orifices open.
The high pressure difference between the pre-chamber and the main chamber causes an explosive discharge / penetration of the burnt gas from the pre-chamber into the compressed air-fuel mixture in the main chamber (in a way similar to the direct injection Diesels wherein the penetration of the fuel is achieved with some 2,000 bar injection pressure for liquid injection).
The active radicals penetrate “instantly” (in comparison to Mahle’s TJI) in the compressed air-fuel mixture, which also undergoes a pressure sock.
All these trigger the HCCI combustion of the rest mixture.

I.e. in the one case (Mahle TJI) burnt gas is blown into the compressed air-fuel mixture in the main combustion chamber providing a faster and more stable combustion of the lean mixture, while in the other case (PatBam) the conditions favour true HCCI combustion not only in the pre-chamber, but into the main chamber as well.


Thanks
Manolis Pattakos

[manolis]

Hello all.

Here is the first page of the US patent granted today for the PatBox CVT.



For the complete patent document: http://patft.uspto.gov/

Thanks
Manolis Pattakos

[Tommy Cookers]

the PatBox seems to be useful for cycle manufacturers - and for enthusiast motoring types who like to play at shifting

does the auxiliary belt concept help in some way to mix transmission with motorgenerator functions ?