2 stroke thread (with occasional F1 relevance!)

[Big Tea]

See here: https://www.youtube.com/watch?v=YEaE6BHyjzg

2-piece piston designed to reduce mass & improve dimensional-control/sealing - via even thermal expansion.

Brilliant, as long as it does not unscrew

[gruntguru]

. . . . Any backpressure incurred by a PRT would require a corresponding increase in scavenging pressure - a near impossibility with the crankcase as transfer pump. Equally hard to imagine a PRT could be contrived to harness the pulse energy without creating backpressure. . . .

There are many examples of crankcase scavenged 2 strokes adapted for turbocharging.
.

Equally hard to imagine a PRT could be contrived to harness the pulse energy without creating backpressure.

If you read the Wright T.C. info you can see how its done.

[Pinger]

If you read the Wright T.C. info you can see how its done.

Yep, with 2-stage supercharging (and yes, altitude performance was a factor also).

I think we can safely conclude there has never been a NA 2T engine with a PRT - and probably never will be.

[gruntguru]

No - my point was - a PRT can be configured in a way that captures blowdown energy without creating backpressure during parts of the cycle that would be disadvantageous (with or without supercharging).

[tok-tokkie]

That 2 piece piston design. Here is a guy who wants to combine that idea with another that allows a piston ring that is a complete ring. The screwed piece is the complete crown with the wrist pin bit as in the 2 part design. Just the simple cylindrical skirt screws onto the crown. The skirt traps the complete piston ring in its groove. Seems a really good idea to me. What about expansion of a complete piston ring - is that an issue?

https://www.youtube.com/watch?v=JGK-Sa8 ... e=youtu.be

[Pinger]

No - my point was - a PRT can be configured in a way that captures blowdown energy without creating backpressure during parts of the cycle that would be disadvantageous (with or without supercharging).

How can it be so configured - much larger than required/expected relative to the mass gas flow?

[Pinger]

That 2 piece piston design. Here is a guy who wants to combine that idea with another that allows a piston ring that is a complete ring. The screwed piece is the complete crown with the wrist pin bit as in the 2 part design. Just the simple cylindrical skirt screws onto the crown. The skirt traps the complete piston ring in its groove. Seems a really good idea to me. What about expansion of a complete piston ring - is that an issue?

https://www.youtube.com/watch?v=JGK-Sa8 ... e=youtu.be

Struggling to see how an unsplit ring can expand under gas pressure to perform its sealing function.

[63l8qrrfy6]

The same way a C ring does in static sealing applications I suppose.

[gruntguru]

No - my point was - a PRT can be configured in a way that captures blowdown energy without creating backpressure during parts of the cycle that would be disadvantageous (with or without supercharging).

How can it be so configured - much larger than required/expected relative to the mass gas flow?

Basically - yes. Of course the exhaust runners must be grouped to avoid overlapping of exhaust events within each group and plumbed to deliver blowdown pulses all the way to the turbine nozzle (which will be the smallest cross section in the runner).

[Pinger]

Basically - yes. Of course the exhaust runners must be grouped to avoid overlapping of exhaust events within each group and plumbed to deliver blowdown pulses all the way to the turbine nozzle (which will be the smallest cross section in the runner).

With such a configuration, would the pulse be reflected on/after entering the turbine nozzle and if so, would it reflect as a positive or negative pulse?

[gruntguru]

Basically - yes. Of course the exhaust runners must be grouped to avoid overlapping of exhaust events within each group and plumbed to deliver blowdown pulses all the way to the turbine nozzle (which will be the smallest cross section in the runner).

With such a configuration, would the pulse be reflected on/after entering the turbine nozzle and if so, would it reflect as a positive or negative pulse?

https://books.google.com.au/books?id=MD ... ne&f=false

Any reflection is an indication that the turbine is not extracting all the energy from the pulse. The linked article states that reflections increase with pressure ratio and pulse turbocharging becomes less viable at high pressure ratios. The reflections are positive - having a negative effect on the exhaust stroke.

[Pinger]

Thanks GG - much appreciated.

[manolis]

Hello all.

Here are the moving parts of the OPRE TIlting 2-stroke engine:













The above tilting valves have "rectangle" shape for the shake of the easy / accurate manufacturing with a lathe.

And here are two youtube videos of the engine (manual cranking).





Thanks
Manolis Pattakos

[tok-tokkie]

I am really pleased to see your progress into running engine. It sounds very smooth & there is no vibration. Looking wonderful. Congratulations.

[Pinger]

As per the above post Manolis, congrats on getting it built and running. A few questions if you can indulge me please.
Looking at the designated web page, I see some of the claimed benefits (eg, combustion dwell, side thrust on cooler part of piston, etc) but what does the tilting valve bring to the table? Asymmetric timing and if so, in which direction - late? What are the transfer and exhaust timings (if you are prepared to divulge them - fine if you prefer not to)? When do you intend to run it under load and what power output are you expecting?