10 replies to this topic

[manolis]

Hello.

Here is 2-stroke, we call it PatTwo, running on Miller cycle:



With a separator the space between the two ends of the piston is divided into two sections; the separator comprises a passage between the two sections and a valve that controls the passage from fully closed to wide open.



The valve controls the load precisely "all the way", from idling to full load.




Here is an unconventional PatTwo Harmonic engine:









With its single-piece double-acting piston, this two-cylinder engine has two combustions per crank rotation (i.e. as many as a 4-cylinder 4-stroke) and, in total, only three moving parts:
the first is a rotating, at constant angular velocity, power shaft,
the second is a rotating, also at constant angular velocity, intermediate shaft,
and the third is a reciprocating piston.



Among others, the Harmonic PatTwo engine is:
compact,
lightweight,
simple,
fuel efficient (it avoids subpressures at partial loads).

It has "four stroke like" lubrication.

It is as vibration-free as the Wankel Rotary engine.

Below the PatTwo Harmic is shown stereoscopically from various viewpoints:




For more: http://www.pattakon....takonPatTwo.htm


Thoughts?

Objections?

Thanks
Manolis Pattakos

[bigleagueslider]

Manolis-

 

I am impressed by the number of unique recip engine concepts you produce. And I applaud the fact that you post them on this website for criticism and comment. But on the other hand, unless these concepts are commercialized they have no value other than providing you a personal sense of satisfaction at having created some original concept for a mechanical device. Don't get me wrong, I do enjoy discussing the pros/cons of your engine concepts. But have any of them resulted in a viable commercial product?

[gruntguru]

Perhaps one in ten thousand (wild guess) innovative engine concepts results in a viable product. Of the hundreds I have seen attract serious investor dollars, very few have been as technically sound as any of Manolis' offerings on this forum.

 

OTOH if you look back at mankind's greatest inventions, you will find most of them spent a considerable period having "no value" before finally being commercialised.

 

I believe there is real value in subjecting good ideas to public scrutiny.

[mariner]

I cant se any obvious problems but I am not a engine guy at all.

 

Two quetions

 

1) How do you adjust the compression ratio betwen the inner compression cylinder and the outer " power" ones?

 

2) How is it actually assembled?

[manolis]

Hello Mariner.

You write:
“How do you adjust the compression ratio betwen the inner compression cylinder and the outer " power" ones?”

Let’s take the case of the single cylinder PatTwo with the connecting rod and the reed valve.



The separator (7) divides the space under the piston crown in two sections (8) and (9).

In case the passage (10) of the separator (7) is fully open (WOT) by the disk valve (11), the air or mixture from the one section passes to the other and the engine just idles (the moment the transfer ports open, there is no significant compression of the charge, so only a small quantity of it enters into the cylinder).

In case the passage (10) is partially open, during the upwards motion of the piston air or mixture enter into the upper section (8) partially from the lower section (9) and partially from the reed valve. During the downwards motion of the piston (2), the air or mixture in the upper section (8) is compressed, with a part of it escaping to the lower section (9). The moment the transfer ports open, a quantity of air or mixture enters into the cylinder and scavenges it. The engine runs at partial load. The more open the valve, the lighter the load.

In case the passage between the upper and lower sections is fully closed by the valve, during the upwards motion of the piston the upper section fills with air or mixture coming from the reed valve. During the downwards motion of the piston, the air or mixture trapped into the upper section is compressed (it cannot pass to the lower section because the valve is closed, nor it can escape from the reed valve). When the transfer ports open, a big quantity of air of mixture enters and scavenges the cylinder. The engine operates in full load.


You also write:
“How is it actually assembled?”

The separator (with the valve on it) is located inside the piston; the piston is normally assembled into the cylinder. Then the disk-like separator is rotated and is secured to the cylinder (the separator has extensions that extend through the longitudinal openings on the piston skirt). The opening for the reed valve or the opening of the inlet port gives access inside the piston.

Alternatively, you can locate the separator outside the cylinder (in this case you can add one or two chambers to increase the dead volume of the upper and lower sections in order to decrease the primary compression, if this is desirable). In such a case the separator can be a conventional throttle valve.

In the case of the Harmonic PatTwo, with the throttle valve inside the cylinder, the shaft of the throttle valve enters through a hole on the cylinder and is secured to the throttle valve.

Thanks
Manolis Pattakos

[gruntguru]

Not sure why you characterise this as Miller cycle, could you post the cycle on a p-v diagram? What is the advantage of the internal throttling? There are still pumping losses through the throttle valve at part-load (although interestingly not at idle.

[manolis]

Hello Gruntguru.

Why Miller?

Take the case the PatTwo operates at light load and compare it with the case a 4-stoke PatAir (unlimited Miller cycle, at http://www.pattakon....ttakonHydro.htm ) operates at light load, too.

In the 4-stroke Miller the intake valves stay wide open during the intake stroke and during most of the compression stroke (for instance, they close 150 degrees after the BDC, or 30 degrees before the combustion dead center). Air or mixture enters and fills the cylinder and then most of it returns to the intake manifold at a low expense of energy.

In the PatTwo 2-stroke, air or mixture from the lower section fills the upper section as the piston moves upwards, then most of this air or mixture returns to the lower section also at low energy expense.

A main difference is that a part of the 2-stroke cycle is realized outside the cylinder, underside the piston crown.
A main similarity is the avoidance of creating sub-pressures and the substantial reduction of the pumping loss at conditions wherein the engine is not making significant amounts of power.

The reduction of the pumping loss comes with another advantage: the reduction of the contamination of the fresh air or mixture before its entrance into the cylinder.

In the following plot:



the curve A is the variation of the volume underside the piston of the conventional; 2-stroke. At the point D the transfer ports open. As the piston moves downwards, the volume underside the piston decreases. At low revs / light loads some 15 to 20% of the capacity of the cylinder passes inside the cylinder from the space underside the piston. After the point F (BDC) the piston moves upwards decreasing the volume inside the cylinder and increasing the volume underside the piston. Now some 15 to 20% (it depends on the timing of the transfer ports) of the gas (fresh air / mixture mixed with a lot of residual gas) passes back to the space underside the piston. After a few rotations at light load or idling, the air / mixture underside the piston is contaminated with a significant percentage of residual gas.
If the throttle is widely open, the engine needs several rotations before the space underside the piston gets rid of residual gas. Till then, the engine coughs, misfires etc.

Compare the case with the plot of Fig C.
The difference has to do with the quality of the charge above and below the piston crown.

Here is a P-V plot for a two-stroke:



The blue curve is for a PatTwo at light load. The upper side is for the combustion chamber. The lower side of the blue curve is for the upper section of the space underside the piston.

The green curve is for a conventional 2-stroke at light load. The upper side of the curve is for the combustion chamber, the lower is for the crankcase.

The red curve is for full load at both cases.


At medium loads the PatTwo engine generates enough power, which means the pumping loss due to the partially open valve at the passage between the upper and lower sections is a slight part of the provided power.

To avoid completely this loss, the “throttle valve” can be substituted by an electronically controlled valve like those of the MultiAir / PatAir, or by an electromagnetic valve. The valve opens widely at some crank angle and closes completely at another crankshaft angle eliminating the throttling loss. The drawback is the complication added to the 2-stroke.

Thanks
Manolis Pattakos

Edited by manolis, 27 December 2014 - 12:20.

[Kelpiecross]

 You could probably get the same effect by having a connecting pipe and butterfly valve between the crankcases of a twin-cylinder two-stroke engine. 

[manolis]

Hello Kelpecross.

You write:
"You could probably get the same effect by having a connecting pipe and butterfly valve between the crankcases of a twin-cylinder two-stroke engine."

Yes and No.

I think you mean this:



The complete patent is at http://www.pattakon..../CITS_USPTO.gif Please read the paragraph at line 57 of page6.


The Australian company CTIS (at http://www.citsengine.com.au/ ) has manufactured a twin-cylinder prototype and is now looking for some $4.0m to proceed.



No, “you cannot get the same effect by having a connecting pipe and butterfly valve between the crankcases of a twin-cylinder two-stroke engine”.


The following plot shows the variation of the total volume underside the two pistons of a paired CITS engine with the bypass valve wide open:



Quote from http://www.pattakon....takonPatTwo.htm

"Comparison with the "paired cylinders" approach

In the Fig A the curve A is the variation vs. the crankshaft angle of the volume underside the first piston of a paired cylinder 2-stroke (according the US8,683,964 patent), the curve B is the variation vs. the crankshaft angle of the volume underside the second piston of the paired cylinder 2-stroke.
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 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, at low-medium revs with the bypass valve wide (or completely) open, some 30% of the one cylinder capacity enters, per crank rotation, into the two cylinders, and some 30% of the residual gas in the one cylinder 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."

End of quote


By the way, it is interesting to compare the variation of the total volume of the two-cylinder CITS engine with the variation of the volume underside the piston of a conventional single cylinder 2-stroke:



The width of the variation is more-or-less the same.
The timing of the variation is different:
in the one case the increase of the volume under the piston comes first, in the other case the decrease of the volume under the piston comes first.


In the case of the single-cylinder PatTwo, the volume of the combined space underside the piston is constant, as in the Fig C at http://www.pattakon....takonPatTwo.htm

The PatTwo is a substantial and necessary improvement of the CITS “paired-cylinders” system.

”Substantial and necessary improvement” because with less it achieves more:
it needs not a second (or paired) cylinder,
it keeps the volume of the combined space constant,
it needs not an “external”/additional throttle for the control of the engine at light load / idling, etc.

Thanks
Manolis Pattakos

[Kelpiecross]

Yes - something like that - but  just with a butterfly valve between the two cylinders.

 Of interest to me is that I have had (very) distant contact with the inventor of USPTO 8863964 - Basil Van Rooyen.   Basil is/was a South African racing driver who had a couple of drives in F1. He now lives in Sydney. 

 

 Some of his variations in the patent involve a crosshead-like arrangement  - I don't think any high-speed engine can have a layout like this.  

Edited by Kelpiecross, 28 December 2014 - 12:39.

[manolis]

Hello Kelpiecross.

Nice to hearing you have had a contact with this F1 guy.

If he needs a (very) high-speed crosshead, we’ll find one (or two).

Thanks
Manolis Pattakos