2 stroke thread (with occasional F1 relevance!)

[autogyro]

How about a bit of twostroke discussion.

I agree but let us not forget it was Manolis who opened the debate on impractical light helicopters.


Manolis said :- Gyroplanes have their own limitations.
I don't think there is a conspiracy to keep gyroplanes out of the game.
Their characteristics limit their use.

Again I am forced to answer.
What characteristics?
This is untrue, it is lack of investment for development that has restricted autogyro use.
Vested interest in American inferior concepts to create cash cows has been the main block to autogyro and other innovative aircraft ideas.
Throwing money at things is not the way forward as F1 is now fully aware.

I love all the engine ideas from Manolis.
I have always been very interested in the opposed piston two stroke ever since I rode the footplate of the Deltic prototype locomotive as a child with my father.
A company I was a director of even had the name Deltic Engineering.
I am still looking for a Commer knocker engine to 'play' with.
I might fit one in one of the Maserati chassis we have.
I built a diesel De Thomaso some years ago with an automatic transaxle.

I believe the future is electric traction for road vehicles.
However at present and for the forseeable future range extenders will be a must.
The opposed piston through scavenged two stroke is an obvious choice for this purpose.
With no need to directly drive the road wheels there is no further need for rotational output, so no need for the loses associated with crankshafts and con rods.

[J.A.W.]

Got something tangible - to put up & back those bold claims of the demise of recip' drive..
..in favour of electrickery/sophistry, eh then A-G?

After all, even Wankel's well supported rotary piston design attempt - has largely faded out now..

[manolis]

Hello Autogyro.

It is supposed the leaning of the connecting rod and the created thrust loads cause a significant loss of energy in the conventional reciprocating engines, making the linear generators a preferable solution.

However, the most efficient stand-alone engines today are the giant two strokes:



Their Brake Thermal Efficiency exceeds 50%.

These engines are of the crosshead type.
And they use – against the theory – extra small connecting rod to stroke ratios.

For instance:
The Wartsila X92 ( http://wm.am.gdynia.pl/wp-content/uploa ... /W-X92.pdf ) has 920mm bore and 3,468mm stroke (stroke to bore ratio: 3.77) and provides some 8,000bhp (5,850kW) per cylinder at 76rpm.
At page 14, the above PDF gives the center-to-center length of the connecting rod, which is 3,468mm, i.e. equal to the stroke.

Think: the most efficient (or one of the most efficient) modern internal combustion engine uses an extremely short connecting rod that increases substantially the resulting thrust loads.
More important than the optimization of the friction is the optimization of the combustion / expansion (of the thermodynamics). A 2% reduction of the thermal loss to the surrounding walls (cylinder head, cylinder liner) is more important than a 10% reduction of the – already small - mechanical friction.
The mechanical efficiency is high, even with short connecting rods.

By the way, the friction of the piston rings is a big part of the total friction.
The linear generators have piston rings, too. They also have their own disadvantages and limitations.
Half a century ago the Free-Piston engines were the most promising. In practice, they proved inferior to the conventional Diesels.

So, you have to compare “the loses associated with crankshafts and con rods” to the complications / side effects / losses introduced by the linear generators.
Unless I am wrong, Toyota still uses a conventional reciprocating engine (with crankshaft and pistons, Atkinson-Miller cycle) to drive the electric generator of the PRIUS.

Take this direct injection Diesel OPRE crosshead two-stroke:



and replace the two counter-rotating flywheels by two counter-rotating electric generators.
What you get is a REM (Range Extender Module) for electric cars. Much better than the existing Wankel REM’s of AVL and FEV (fuel efficiency, emissions, NVH properties).
More simple, cheap and lightweight than any linear generator.

Thanks
Manolis Pattakos

[manolis]

Hello J.A.W.

The first test will be with the PatATi engine “naked”, to see if the asymmetric transfer and intake can make the entire job without the need of exhaust, or tuned exhaust.

Two injectors, one per crankcase, are to be used for the (indirect) injection of premixed fuel-oil.
Clean air will get into the crankcases through the four intake ports at the sides of the cylinder; the air will be mixed with the fuel inside the crankcases before entering into the cylinder for the scavenging.
A pair of rotatable “collars” around the cylinder – above the intake ports – control the intake port openings.
An alternative way to be tested is to throttle the exhaust ports instead of the intake ports.

The exhaust is at the backside of the cylinder. The air stream coming from the propellers blows away the exhaust fumes.

If necessary, a lightweight silencer will be used.

Thanks
Manolis Pattakos

[uniflow]

Manolis, have you had much experiance designing EFI twostrokes before?

[J.A.W.]

Thanks for that Manolis, & all the best with getting it flying..

[autogyro]

Thanks for that Manolis, & all the best with getting it flying..

Good luck Manolis, I mean this.
Where do I send the flowers?

[J.A.W.]

Good luck Manolis, I mean this.
Where do I send the flowers?

Why not be honest A-G? - best send some of your surplus sour grapes..
& perhaps.. get some crow in.. to tide you over?

[autogyro]

Sorry J.A.W but I was being completely serious based on many years experience.
Manolis is a brilliant engineer on engines I respect that.

[manolis]

Hello uniflow.

You write:
“Manolis, have you had much experiance designing EFI twostrokes before?”

Not in two strokes.

However, you can open and read the Power Point:

http://www.pattakon.com/DVA_files/pattakonVVAs.pps

(it was pattakon’s presentation at Engine Expo International - Stuttgart Germany 2008).

A lot of work has been done on the EFI of the Honda VVA-roller prototype (1600cc, 4-cylinder, B16A2):



No throttle valve.
Zero cost ITB:



Continuously Variable Valve Lift from 0mm to 12mm.

Idling at 330rpm, rev limit at 9,000rpm.

Thanks
Manolis Pattakos

[uniflow]

Is that a twostroke? What relevance

[J.A.W.]

Fair point U, could that Honda mounted system feed a 2-stroke turning 9,000rpm?

[manolis]

Hello Uniflow and J.A.W.

The EFI, or PGMFI, used in the Honda VVA-roller prototype can be used in an 800cc two stroke till 9,000rpm.
The reasoning is simple.
The size of the cylinders is the same, so with an injection per crank rotation per crankcase, the 800cc two stroke is feeded with the required quantity of fuel even at full load.
Using the two pairs of injectors of the Honda b16A2 alternatively, the 9,000rpm is nothing special.
For as long as the 800cc two stroke runs in open loop, the electronic control unit provides, according the reprogrammed injection and ignition maps, the proper quantity of fuel and the proper spark advance.

Unless I am wrong, the EFI unit doesn't know (and doesn't care) whether the fuel is objected into the intake manifold of a four stroke or into the crankcase of a two-stroke.


However, the PatATi Opposed Piston engine of the prototype Portable Flyer needs something simpler, cheaper and more lightweight than the PGMFI of Honda.

Thanks
Manolis Pattakos

[uniflow]

Manolis, you may be in for a surprise. EFI in a twostroke is not as straight forward as you might think. I would allow quite a bit of development time on this part of the project.

[langwadt]

Manolis, you may be in for a surprise. EFI in a twostroke is not as straight forward as you might think. I would allow quite a bit of development time on this part of the project.

if it is injected in the cranks case should be more or less equivalent to an "electronic carburetor"

direct injection is whole nother kettle of fish ..