2 stroke thread (with occasional F1 relevance!)

[Pinger]

Ah, no.. P, those machines all had the scavenging process already sorted out, the turbocharger was additional, either to
maintain ambient pressure over an altitude gradient, or for lower levels, such as at sea-level.. purely for ++ power..
..& efficiency, in utilizing the energy of copious exhaust pulses..

Apologies J.A.W., I missed the reference to turbo sleds.
Fair points. Increasing the overall charge density but the corresponding increase in exhaust back pressure is pretty much essential to prevent the incoming becoming the outgoing before the exhaust port has closed (other than the sled example where returning +ve pulses from an exp' chamber are present) if the exhaust closes after transfer closure. In essence, it is the creation of its own micro (higher than prevailing ambient pressure) environment - in a way that the 4T does not require. That is, the back pressure of a 4T can be as low as the environment permits and no charge loss occurs no matter the degree of supercharge.
Different where greater control of exhaust timing is present eg, poppet valves but that control for opp piston engines is still limited. In all cases, the heat loads on the piston(s) are significantly increased - but then that's always the case when the power output is upped!

[manolis]

Hello Pinger.

You write:
“Perfect balance is laudable but not absolutely the last word.”


Think of a lightweight 800cc single cylinder engine “secured” on your shoulders:






You also write:
“Torsional issues with opp piston: Fair enough, if you want to dismiss Ricardo's findings. I don't.”


My post is not about dismissing “Ricardo’s findings”; it is about finding what causes “Ricardo’s findings”.
It explains the “torsional issues” observed by Ricardo in Opposed Piston engines having extensive phase difference between the two crankshafts.
So, take another read. It is a simple explanation.




You also write:
“Supercharging (charging the cylinder to a pressure higher than prevailing ambient pressure) is not possible without adequate filling time after exhaust port closure.”


No.

QUOTE from http://lingualeo.com/pt/jungle/how-does ... 40#/page/1

“Specific to EMD two-stroke engines (567, 645, and 710):

The power stroke begins at TDC [0 degrees];
injection of fuel leads TDC by 4degrees [356 degrees], such that injection of fuel will be completed by TDC, or very shortly thereafter;
the fuel ignites instantaneously), after which power stroke the exhaust valves are opened thereby greatly reducing combustion gas pressure and temperature, and preparing the cylinder for scavenging, for a power stroke duration of 103 degrees

Scavenging begins 32 degrees later, at BDC–45 degrees [135 degrees], and ends at BDC+45 degrees [225 degrees], for a scavenging duration of 90degrees;
the 32 degree delay in opening the scavenging ports (thereby terminating the power stroke), and the 16 degree delay after the scavenging ports are closed (thereby initiating the compression stroke), maximizes scavenging effectiveness, thereby maximizing engine power output, while minimizing engine fuel consumption.

Towards the end of scavenging, all products of combustion have been forced out of the cylinder, and only "charge air" remains (scavenging may be accomplished by Roots blowers, for charge air induction at slightly above ambient, or EMD's proprietary turbo-compressor which acts as a blower during start up, and as a turbocharger under normal operational conditions, and for charge air induction at significantly above ambient,[2] and which turbocharging provides a 50 percent maximum rated power increase over Roots-blown engines of the same displacement).

The compression stroke begins 16 degrees later, at BDC+61 degrees [241degrees], for a compression stroke duration of 119 degrees”

END OF QUOTE

Here is an EMD 2-stroke:



and here it is shown an EMD burning natural gas:





So, we have a turbocharged 2-stroke Diesel that closes the exhaust valves 16 degrees after the closing of the transfer, and yet it provides a 50% maximum rated power increase over Roots-blown engines of the same displacement.

So, take another read of the posts and let me know if something is confusing.




You also write:
“That small end on the Honda V3 is horrible. Are you still happy to add weight to the upper end of a con rod Manolis?’

? !

Thanks
Manolis Pattakos

[manolis]

Hello Pinger.

You write:
“Supercharging (charging the cylinder to a pressure higher than prevailing ambient pressure) is not possible without adequate filling time after exhaust port closure. The more conventional architecture of single piston (as per your design and Primavis) when arranged to have the transfer port open long after exhaust closure exposes the transfer port to high pressure and temperature before and during blowdown. Hence Primavis making provision for extensive cooling in the valve area of its design. That complication and the additional complication of a more highly pressurised air supply (and with the extra air work) make any gains dubious against the additional complexities.”


Under the light of the last posts, the basis (the first sentence) in the above paragraph is wrong.

So, the asymmetric transfer ports:
of the Primavis of Piero Baldini,
and
of the PatATi of pattakon,
need not to remain open long after the exhaust port is closed.

Actually, in the turbocharged EMD engines the optimum is to close the transfer ports 16 degrees before the exhaust.

Which means that the asymmetric transfer ports of the PatATi in a, say, Cross-Radial turbocharged di Diesel for small airplanes (like that of the animation in previous post) can close a few degrees (say 16? 12? 6? 3? 2? 1?) before the closing of the exhaust port to give the optimum power and fuel efficiency.

So, I guess, the “overheating” argument, which was based on the wrong assumption, is not an argument any longer.



What I try to understand is what you mean by the “additional complexities”.

Are you sure you got the way the PatATi operates?

Please do take another read of the http://www.pattakon.com/pattakonPatAT.htm web page,



and let me know about the “additional complexities” you see in the above PatATi design (because all I can see is three moving parts in total, as asymmetrical intake as desirable, and as asymmetrical transfer as desirable).


Thanks
Manolis Pattakos


.

[Muniix]

New 2 Stroke engine release;

The CITS


http://citsengine.com.au/home/

The baffle under the piston isolates the intake from the sump and the piston skirt still controls the intake and transfer. The swept charge/tranfer volume to total under piston volume is much higher than in a normal 2 stroke since the crankcase volume around the lower end of the con rod is eliminated boosting the compression pressure. The engine is otherwise a normal narrow V twin.


CITS ENGINE TECHNOLOGY
It is a patented two-stroke petrol engine, like no other before, patented in 20 countries.
It does not consume its lubricating oil like normal two-strokes, but recirculates it.
It allows the lowest inherent imbalance forces (vibration) of any V-twin four or two-stroke.
It eliminates the costly roller bearings and their complex fitment to multi-cylinder crankshafts, found at the bottom of two-stroke engines.
The technology has an independent appraisal from an internationally recognised expert, and for it the inventor has been awarded an SAE nomination for “excellence in automotive Engineering”.
It retains the high power-to-weight and low cost-to-power ratios of the two-stroke.
It eliminates the expense, weight, friction and maintenance of the valves, springs, camshaft and drive, found in the top of four-stroke engines.
With just two cylinders, as a smooth V-twin, from 250 to 1250 ccs, it can deliver from 30 to 140 kW – as much as a typical 4-cylinder four-stroke – at under half the cost.
Constant rpm applications, such as in plug-in hybrid electric autos and portable generators, allows super-tuning for its lowest emissions, maximum torque and best economy.
It uses established factory methods and machinery to manufacture.

[Muniix]

2T engine advantages are typically in small light weight engines that aren't regulated, with electric tools offering 6+ kW slow start for low impact to operator that market is gone for good. Energy storage worn on the operators waist or backpack with quick change.

Seems you still can't grasp the fundamental basics Marc..

Fact is - the 2T advantage of every piston downstroke being a powerstroke is why they are utilized in the
largest recip' settings, by powering huge cargo vessels efficiently - enabling direct drive - & thus allowing
the propeller & crankshaft to both turn at the most efficacious rates for traversing long oceanic routes..

For shipping they are built for purpose. Optimisation to the highest. Well done, it's using the combustion process effectively

However, more and more are now using many Modula large 4T engine generators running at peak efficiency. They start as many as demand requires to supply electric power to electric driven propshafts.

Nor it seems did you read the cited Kevin Cameron article wherein he duly notes the power density/mass packaging
advantages of the 2T so apparent in current snowmobiles, viz: 4Ts are still too bloody heavy, esp' to drag out when stuck.

& yeah, do post an advert for a professional, hard-use anywhere - chainsaw, which isn't a 2T, as proof of your claims..

My father had a Batam, not all four Stroke engine are heavy 77kg for a V10 with over 1,000 HP is not heavy.

Because some one engineers one that heavy is evidence of the Engineer only.

A 26 kg single with 78hp four strokes have been engineered. 146 HP at 42 kg will be available by 2020, 180 HP with mild hybrid and multiphase combustion.

Cherry picking information can prove anything.

[Pinger]

So, we have a turbocharged 2-stroke Diesel that closes the exhaust valves 16 degrees after the closing of the transfer, and yet it provides a 50% maximum rated power increase over Roots-blown engines of the same displacement.

Manolis Pattakos

And how much of that additional 50% accrues from not having to drive the Roots blower?

You will not pressurise a vessel with a hole in it. See my earlier post re back pressure.

[Pinger]

What I try to understand is what you mean by the “additional complexities”.

The 'valving' within your piston and the piston is going to be exposed to very high pressure and temperature as soon as the port window is uncovered. That, IMO, is going to cause you all sorts of headaches.
Primavis does not expose the pistons underside to distortion promoting heat and has a simpler valve almost external to the engine - which still requires water cooling.

[gruntguru]

Supercharging (charging the cylinder to a pressure higher than prevailing ambient pressure) is not possible without adequate filling time after exhaust port closure.

Not so. Any two stroke that runs effectively at atmospheric pressure can be supercharged to any desired pressure using a turbocharger. When exhaust back pressure is similar to boost pressure, the engine simply breathes as it would NA except the air has higher pressure and density.

[J.A.W.]

My father had a Batam, not all four Stroke engine are heavy 77kg for a V10 with over 1,000 HP is not heavy.

Because some one engineers one that heavy is evidence of the Engineer only.

A 26 kg single with 78hp four strokes have been engineered. 146 HP at 42 kg will be available by 2020, 180 HP with mild hybrid and multiphase combustion.

Cherry picking information can prove anything.

Marc, that light "Batam" 4T V10 of "over 1,000 HP" which your father had, do support your claim, post a citation link..

Also a post showing a 'kosher' dyno chart of the "26 kg single with 78 hp" 4T on test.. lets see that 'cherry'..
Since 'the proof of the pudding', even one cherry based, is in the results per taste, ah, test.. & not in 'magic' claims..

[J.A.W.]

New 2 Stroke engine release;
The CITS

Actually Marc, not quite so "new", I cited this machine here some 30 months ago, its back on P. 23..

Notwithstanding that S.O.P. - hyperbolic-type investment pitch - is it in fact - supported by proof?
If so, do kindly post the video of a running example, say, on a dyno, & preferably - in an actual moving vehicle..
& with an independent appraisal from the tester.

[manolis]

Hello Pinger.


You write:
“And how much of that additional 50% accrues from not having to drive the Roots blower?”

Does it matter? (if it does, GM may answer).

What does matter is the fact that with the turbocharger (and without the “Roots-blower” which is activated only in specific conditions) the engine provides 50% more power and a better fuel efficiency.




You also write:
”You will not pressurise a vessel with a hole in it. See my earlier post re back pressure.”

?




You also write:
“The 'valving' within your piston and the piston is going to be exposed to very high pressure and temperature as soon as the port window is uncovered. That, IMO, is going to cause you all sorts of headaches."

Suppose the asymmetric port of the PatATi engine opens and closes simultaneously with the exhaust port, which is still an aggressive timing (as explained in previous posts, even the turbocharged EMD engine of GM closes the transfer port 16 crank degrees before the exhaust) and let me know: what does your:
“the piston is going to be exposed to very high pressure and temperature as soon as the port window is uncovered”
mean?

Then think of the situation wherein the power valve at the exhaust port, in the following drawing of the Primavis engine, is at its “close” position (dashed line):



and the piston has uncovered (partially or completely) the exhaust port (typical situation for all conventional 2-strokes with power valve at the exhaust).

There is where the piston skirt suffers, not only because it is exposed to the “red hot” and violently moving gas that exits from the cylinder and moves towards the exhaust, but also because it thrusts on the hottest side of the cylinder liner around the exhaust port.

In comparison to the piston skirt areas that face the “asymmetrical transfer ports” at the sides of the cylinder, the area of the piston skirt facing the exhaust port is like being “in the hell”.




You also write:
“Primavis does not expose the pistons underside to distortion promoting heat and has a simpler valve almost external to the engine - which still requires water cooling.”


The “simpler valve” of the Primavis engine requires:

the addition of an “external” shaft with its bearings (the rotary valve),
also the addition of a synchronizing gearing between the shaft and the crankshaft,
also the addition of a second cylinder / piston / connecting rod / reed valves (the compressor) and the piping for the transfer of the compressed air / mixture to the combustion cylinder.

Do I miss something?




Thanks
Manolis Pattakos

[manolis]

Hello all

QUOTE from the US14/948405 patent application for the PatTwo engine of pattakon (for which the GB2,533,619 patent has already been granted by the UK-IPO; more about the PatTwo engine at http://www.pattakon.com/pattakonPatTwo.htm ) :


“That is, the engine control can completely be based on the position of the valve that opens and closes the passage between the two sections. The constant total volume of the two sections is crucial for the control of the engine at light loads and idling as explained in the following.

In the U.S. Pat. No. 8,683,964 (Basil Van Rooyen) it is proposed a two-cylinder two-stroke engine wherein a bypass valve is disposed between two inlet ports short-circuiting the sections underside the two piston crowns and creating a combined volume. According the abovementioned patent, the partial load operation is improved, the pumping loss is substantially reduced, and the load control is simplified. In the FIG. 7A the curve A is the variation vs. the crankshaft angle of the volume underside the first piston of the above U.S. Pat. No. 8,683,964 patent, the curve B is the variation vs. the crankshaft angle of the volume underside the second piston. Each of the two pistons is connected to a conventional crankshaft by a conventional connecting rod. The curve C is the sum of the variations of the volumes underside the two pistons vs. the crankshaft angle (i.e. it is the sum of the A and B curves). With the "connecting rod to stroke ratio" being 1.6, the total volume (curve C) varies more than 16%. For smaller "connecting rod to stroke" ratios, the variation of the C curve is wider. The point D on the A curve is where the first piston opens its respective transfer ports. The point D' on the C curve shows the volume of the combined space underside the two piston crowns the moment the first piston opens its transfer ports. As the first piston approaches its BDC, the combined space increases, causing some 15% of the burnt gas from inside the first cylinder to return to the combined space (case with wide open bypass passage), contaminating and heating the fresh air or mixture (an open transfer port provides substantially smaller resistance in the motion of a gas than a closed reed valve). After the point F at the TDC of the first piston, the volume of the combined space underside the two piston crowns decreases, forcing some 15% of the trapped air or mixture to pass the transfer ports and get into the first cylinder. After 180 crankshaft degrees the same happen in the second cylinder. That is, with the bypass valve wide (or completely) open and low-medium revs, per crank rotation at least 30% of the one cylinder capacity enters into the two cylinders, and at least some 30% of residual gas contaminates the air of mixture in the combined space underside the two piston crowns. This is an undesired limitation for the idle and the light load operation of the engine because it defines the quality and the revs of the idling; worse even, it makes necessary additional load control means (other than the bypass valve) for the idle and the light load operation, canceling advantages like the reduced pumping loss, the simplicity, the compactness, the low cost. As noted in U.S. Pat. No. 8,683,964:

"(In practice a butterfly valve maybe provided in the inlet conduit, not for throttle control but for the purpose of idle setting. Above these very slow idle speeds, this butterfly valve would open fully, and the engine speed and power would be controlled solely by the by-pass valve, and not by the butterfly valve or any other throttle arrangement upstream of the bifurcation point.)".

So, while the U.S. Pat. No. 8,683,964 invention is limited in engines having pairs of cooperating cylinders (the space underside the piston of the first cylinder cooperates with the space underside the piston of the second cylinder), the control of the engine has inherent limitations and the pumping loss at idling and light loads is significant. This is because in a conventional "crankshaft/connecting rod/piston" engine, the motion of the piston is substantially faster near the TDC than near the BDC, so even with the pistons phased 180 crankshaft degrees from each other, the volume of the combined space underside the pistons in the two paired cylinders varies substantially. With infinite "connecting rod to stroke" ratio (which results in pure sinusoidal, or harmonic, motion of the pistons) this deficiency is eliminated. Instead of using infinitely long connecting rods, there are other ways to achieve the harmonic motion of the piston, as described in WO92/17694.”


END OF QUOTE

Here are the patent drawings the above quote refers to:





Basil Van Rooyen is the founder of the CITS and the inventor of the CITS engine (US8,683,964 patent):



he is also an ex Formula-1 driver:




Thanks
Manolis Pattakos

[J.A.W.]

Another interesting & novel 'in the metal' 2T engine from Australia, the builder is an ex-Orbital Corp engineer.

Here the 'sliding cylinder engine' is explained in concept: https://www.youtube.com/watch?v=Hodd8oyiawk
&,
Here, it is - running by its own power, & freely revving: https://www.youtube.com/watch?v=PaYYIfLnHkA

[manolis]

Hello J.A.W.

At top left it is shown the cylinder head of the 2-stroke with the “sliding cylinder” in the video of your link:



Unless I am wrong, by shifting the cylinder (and so by shifting upwards or downwards the exhaust and transfer ports relative to the lowest (BDC) position of the piston) the timing of the exhaust and transfer varies continuously and in a wide range.


It is a pity that the complication already introduced is not completely exploited to get more than just varying the timing of the engine.


Here is the PatHead VCR (Variable Compression Ratio) of pattakon:



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


By shifting (say by a lever as in the animation) slightly (say for +/- 2mm) “on-the-fly” the “central part of the cylinder head (that having the hole for the spark plug at its center) relative to the rest casing, not only the compression ratio of the engine will vary continuously in a wide range, but it will vary independently from the variation of the timing already offered by the sliding cylinder.


By the way,
the “ex-engineer” of Orbital (now involved in the “sliding cylinder project”) may know why the big and promising project of Orbital (i.e. to install their direct injected 2-strokes in cars) ended the way it ended.
If anybody communicates with him, . . .

Thanks
Manolis Pattakos

[J.A.W.]

Hello J.A.W....
By the way,
the “ex-engineer” of Orbital (now involved in the “sliding cylinder project”) may know why the big and promising project of Orbital (i.e. to install their direct injected 2-strokes in cars) ended the way it ended.
If anybody communicates with him, . . .

Thanks
Manolis Pattakos

Hi Manolis, you already know why, since it has been discussed here previously.. there is no secret to it..
1stly, Orbital Corp is not a car maker, & 2ndly, the objections cited in earlier posts by Pinger & myself - tell the story..
..it was a 'marketing' call, both Chrysler with their 'Neon' & Ford with the 'Ka' - had engineered the chassis to use
the 2T engine, but baulked, & expensively reverted to 4T mills, at a late stage, & not due to mechanical reasons..

As for communicating, I suppose you could leave a comment on his youtube account,
or perhaps via personal message on the Kiwi Biker forum, where he is a regular contributor.. in 'engine foundry' - topic?