the clean two-stroke thread

[Vannik]

The Text states that only blower longitudinal scavenging will allow charge control good enough for three way catalyst.

Niels, is longitudinal scavenging just a "bad" translation of Uniflow scavenging?

[Niels Abildgaard]

Niels, is longitudinal scavenging just a "bad" translation of Uniflow scavenging?

Yes off course.
Old age and all that.
Should it be named skewed uniflow sidevalved scavenging or skewscavalved ?

https://drive.google.com/drive/folders/1UqF2OBh8ta5A-
z0euWpIC_t4wKCekzZP

For normal Uniflow see session 2.1

[Niels Abildgaard]

Neils, this is me Ken Seeber, more commonly known as Kensational.




Had a look at the details of the range extender engine. Not too sure on your level of interest in this. For me however, it looks complex, heavy, expensive and undeveloped. If I was looking at a range extender system, it’d be hard to go beyond something like a Chinese copy of something like a 6 hp Honda GX200. In Awestralia, one can buy one of these (commonly referred to a Chonda) retail for <$200 retail. Hard for me to say, given my passion for 2 strokes, in my case, ported and crankcase, or DCI inducted.

Hello Ken and thank You for answering.
My interest is the claim that it can be equipped with a three way catalyst.
I have not much knowledge but I think that the ZrO sensor tries to maintain Lambda =1 no unused Oxygen in engine exhaust.
A normal two stroke with direct charge loss will mess it up.
Orbitals system with blowair,stratificatio and what not also.
The austrians put ca half the possible charge in cylinder,skew the exhaust timing and do not loose anything.
But I do not see that either crancase- or blower scavenge make a difference.
And crankcase scawenging makes engine lower mass and engine heigth


https://cdn2.imagearchive.com/homebu...0dfdbd84a2c003


If you load a two stroke cylinder half and a fourstroke full You have same power but maximum pressure in the two stroke is only half.
Half mass I would say

[Pursang]

Yes off course.
Old age and all that.
Should it be named skewed uniflow sidevalved scavenging or skewscavalved ?

Perhaps it should be called Detroit Diesel 2.1

[Niels Abildgaard]

Perhaps it should be called Detroit Diesel 2.1

Will a sidevalved diesel be possible and usefull?
Compression ratio?
Blow down time area?
Some of my students still devellop usefull uniflow diesels at Burmeister &Wain in Copenhagen.
They made uniflowed one valve per cylinder ships engines before Detroit I think.

[Pursang]

Perhaps I should have called it Detroit Petrol 1.0
The engine shown is spark ignited.


Sidevalve is a very simple and compact layout.
Valve lift can be earlier or later plus faster and higher than OHV, without any piston interference.
Looks like they are using 2 valves per cylinder for sufficient blow-down TA

Compression can be quite high with a flat head and flat top piston.
Limitation is transfer area from top of cylinder to the valves. (Much bigger issue for sidevalve inlets than for exhausts)
They are using 50% of (the possible) input charge for lower peak pressure and I assume a more 'scrubbable' exhaust.

Interesting idea, wonder if it will go anywhere!

[Pursang]

Here is an old idea, re-presented in a new(ish) way with some modern materials and engineering.

The review and commentary is pretty honest & thorough.

[Niels Abildgaard]

[QUOTE=Pursang;1131217482]Here is an old idea, re-presented in a new(ish) way with some modern materials and engineering.

The review and commentary is pretty honest & thorough.




The usual bugbear is the high friction due to very high speed between piston roller and camc.
I do not see how they manage to avoid piston and roller to skew and make a mess?

[Pursang]

[QUOTE=Niels Abildgaard;1131217499]

The usual bugbear is the high friction due to very high speed between piston roller and camc.
I do not see how they manage to avoid piston and roller to skew and make a mess?

They are using 2 widely spaced rollers per piston, reducing skew, but adding friction.
They will argue that elimination of the gudgeon and big end bearings will balance the friction equation.
However, the long extended skirts pump it up again.

My question #1 is: What stops the pistons from sitting 'stuck' up in the bores (ie. not contacting the swish plates or just bouncing against the high point) when the fuel and ignition are switched off and the engine shuts down?

Q.#2 is how do you start it again, if this is occurring?

[Pursang]

Interesting investigation and experiment: Maximising Torque output using linear actuation rather than a rotary crank mechanism.

Problem of "stall" solved with bearings on both sides of the swish plate.

[Vannik]

DeltaHawk Engines has received FAA Type Certification for its highly innovative, jet-fueled aircraft piston engine.

https://www.deltahawk.com/2023/05/18/faa-certification/

[Pursang]

DeltaHawk Engines has received FAA Type Certification for its highly innovative, jet-fueled aircraft piston engine.

This is certainly a big advance in aero engines compared to the Continentals & Lycomings and their 1940's tech.
Piston ported 2S, liquid cooled, compression ignition, mechanical injection, jet fuel (not avgas).

Well done to have gotten FAA approval, looks like this actually has a future.

[ceci]

https://drive.google.com/drive/folders/1UqF2OBh8ta5A-
z0euWpIC_t4wKCekzZP

Thank you for providing the link to the DI2S files,

[Pursang]

Thank you for providing the link to the DI2S files,

Can't view the files directly on-line... but can download. Thanks!

[ceci]

Can't view the files directly on-line... but can download. Thanks!

I was looking at the page of the Polytechnic University of Valencia "UPV" (also on the page of the CMT "center of thermal engines) on the page of the French petrol institute "IPF" I did not find anything

It is stimulating to have knowledge of those who are investigating