3 replies to this topic

[manolis]

Hello all.

In the following design, a buffer of clean air at the top of the transfer “pipe” through which the crankcase communicates with the transfer ports, reduces the unburned fuel in the exhaust of indirectly injected two-strokes.



Undoubtedly it is an improvement (reduced emissions, improved fuel efficiency).

But, is it a solution?

From the closing of the transfer ports to the closing of the exhaust port there is plenty of time for the entered into the combustion chamber air-fuel mixture to escape unburned to the exhaust.
Things are worse.
The available time for the fresh mixture to be lost to the exhaust is longer.
With the reasonable assumption that the air-fuel mixture starts entering into the combustion chamber when the piston is at its BDC (till then only air is entering into, and is scavenging the, cylinder), the time available for the mixture to escape unburned to the exhaust is anything but short (typically, it corresponds to some 60 degrees of crank rotation).


Take now a look at the PatATeco 2-stroke engine design at http://www.pattakon....konPatATeco.htm


Here is a PatATeco design for, say, chainsaws (carburetor).





The scavenging is realized with air from the crankcase.

The transfer of the mixture happens after the closing of the exhaust, which means that the fuel cannot escape to the exhaust before participating in one, at least, combustion.



Here is an indirectly injected PatATeco (stereoscopic animation):





The injection resembles with the "oil jet cooling system" used in several four-stroke engines wherein: "a jet of pressurized engine oil is directed to the underside of the piston to help dissipate the extreme heat generated during sustained high rpm operation".



Here is an indirectly injected PatATeco having 4-stroke lubrication and external scavenging pump:






Thoughts?

Questions?

Objections?

Thanks
Manolis Pattakos

Edited by manolis, 14 October 2016 - 03:42.

[Wuzak]

Your design you say is for small engines, like for chainsaws. 

 

Is the other design for that sort of motor, or for automotive/marine use?

 

If it is for automotive/marine use why would they not use direct injection?

[manolis]

Hello Wuzak.

You write:
“Your design you say is for small engines, like for chainsaws.
Is the other design for that sort of motor, or for automotive/marine use?”

The PatATeco is for all sizes of cylinders.

The carburetor chainsaw engine was used to show the characteristic of the PatATeco architecture to eliminate the unburned fuel lost to the exhaust before participating in a combustion.



You also write:
“If it is for automotive/marine use why would they not use direct injection?”

Because the Direct Injection has its own limitations.

At high revs / heavy load the exhaust particle emissions are a few dozens of times higher (total mass) in a GDI / DFI (Direct Fuel Injection) gasoline engine than in a similar size/performance PFI (Port Fuel Injection) gasoline engine.

The particles emitted by the DFI engines are too small.
The smaller the size of the emission particles in the air, the higher the risk for the health.

The article of Reuters (link at the top of the thread “Engine downsizing to be reverted with new emissions testing” at http://forums.autosp...ssions-testing/ posted by Saudoso yesterday) is worth to read.

It is all about how to pass the rules at the required tests, no matter how much the car pollutes at real conditions.

A small capacity gasoline turbo engine with DFI was the perfect recipe for the automakers: at the test environment the turbocharger is “idle” and the engine appears green.
In real life the small engine has to operate at heavy load wherein it pollutes more (and consumes more fuel) than a bigger displacement non-turbo PFI engine.

For more than a decade the “downsizing” was the only way to go (read how many presentations at Engine-Expo-Stuttgart-Germany deal with the “downsizing” and see how many times it was voted, as the engine of the year, a heavily downsized engine).

Now the rules / standards change to more realistic ones (in real driving the emissions and the fuel consumption will be closer to those in the new tests).



With the PatATeco the 2-stroke keeps the advantage of the DFI (no unburned fuel to the exhaust before the ignition) without suffering from DFI’s disadvantages (like: exhaust particles, fuel-air mixture not well prepared before the ignition, cost, accumulation of deposits etc).

Imagine an indirectly injected (injection onto the downside of the piston crown) 1000cc 2-stroke PatATeco. It can easily make the power of the heavily turbocharged 1000cc 4-stroke engines without overheating and without overstressing.


If you look it from another view point, the transfer of the rich mixture into the combustion chamber through the asymmetric transfer port of the PatATeco is a kind of improved “direct injection” of the fuel.



Thanks
Manolis Pattakos

[manolis]

Hello.

Here is another PatATeco version having four-stroke lubrication and crankcase scavenging:



The upward motion of the piston causes subpressure which suctions air into the intake manifold and into the crankcase through the reed valve and through the throttle valve at right.

After the TDC, the downward motion of the piston compresses the air trapped into the crankcase and into the intake manifold. With the ports open by the piston, compressed air from the intake manifold either scavenges the cylinder or enters inside the piston waiting the asymmetric transfer ports to open.

With the proper form of the air ducts, the oil droplets in the air exiting from the crankcase are collected and then return back into the oil pan, so that the air in the intake manifold near the cylinder ports remains rid of lubricant.

It reminds the "stratified charge" with the difference that here the "oiled air" in the crankcase remains away from the cylinder.

More at http://www.pattakon....konPatATeco.htm

Thanks
Manolis Pattakos