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Old 07-15-2017, 04:58 PM   #11
lohring
 
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This principle has been tried many times and in many ways. One of the most recent is the Lotus Omnivore engine. In my opinion all these systems defeat the most important virtue of the small crankcase scavenged two stroke; simplicity and low cost. A simple 26 cc weadeater engine can develop close to 4 hp with a can muffler. Add a tuned pipe with suitable port timing and you can get close to 7 hp. With a better transfer shape between 8 and 10 hp is still possible using a simple piston port intake. An all out racing 125 cc engine has developed 54 hp. These engines use tuned pipes to get better scavenging and a supercharge effect with high and low pressure pulses. Commercial and racing engines have used variable length tuned exhausts and variable exhaust timing (power valves) for a broader power band. In simple engines mechanical sophistication is replaced with dynamic flow sophistication. It's tougher to design, but simpler to build. Modern computer simulations are a great help in the design of simple two strokes.

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Old 07-16-2017, 03:40 AM   #12
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Hello Iohring.

Thank you for your response.



Currently in the market there are no 2-stroke engines propelling cars or motorcycles and complying with the current emissions standards (euro4).

The only exemption is the KTM250-300EXC, model 2018.


Qute from http://www.motorcyclenews.com/news/2...-really-means/



Euro 4 affects all new models introduced in 2016, and all new bikes from 2017.

End of quote.


Quote from http://thedirtbikerider.com/ktm-endu...2018-2-stroke/

“Also KTM had problems with euro 4 and some KTM dealers can’t anymore sell 2017 models in their country’s. But new 2018 model will come with euro 4 and it will easy pass euro 4 with elections fuel injection and lower emissions. But there is new problem for KTM, in 2020 we will have new big problem called euro5. But we all hope KTM will find solution for this and make EXC and XC models legal for street.”



End of Quote.



It seems that during the next two years KTM has to find a better, than the TPi, solution for the emissions of their 2-strokes.



Here is what a third party (he is a mechanical engineer) wrote yesterday, answering to another member in a discussion in the F1 Technical Forum:

“I think you are missing the clear advantages of a system which can achieve what Manolis is trying to do.

1. The ability to separate the phasing of the exhaust and transfer events can only be beneficial. Remember that the degree of such separation in the PatATE is a design variable which can be optimised to suit the intended application. The conventional two stroke is limited to zero separation - should we assume that this is optimal for every application? Many of the characteristics (exhaust emissions in particular) that make two strokes unsuitable for the applications where four strokes dominate, could be suppressed in the PatATE.
2. A large increase in port width permits larger ports for better flow and faster open/close rates.
3. Shared exhaust/transfer function of the hybrid port provides cooling for the otherwise problematic exhaust port.
4. Cooler exhaust port should allow reduced lube rate.
5. Exhaust reversion could be dramatically reduced - again less stress on the lube and reduced lube consumption.

The goal is not a simple engine to compete in the weed-whacker market - it is a more sophisticated two stroke with all the advantages (other simplicity) without the disadvantages.”

Thanks
Manolis Pattakos


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Old 07-16-2017, 09:55 AM   #13
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The catch is that there's a much better solution to the emissions problem; electric vehicles. We'll see how that develops, but I expect that children looking at today's IC engines in museums will marvel at how we ever could build such complex things. In my model boat racing world, electric power is rapidly replacing IC engines. Electric model boats have held the ultimate speed record for years. Nostalgia for the past will keep modelers building wonderful replicas of IC and steam engines, but I don't see how IC engines can compete with electric power in all but the very largest vehicles as battery costs go down. Even your mower, chain saw, and weedeater will have cordless electric power.

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Old 07-16-2017, 10:12 PM   #14
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Didn't some of the three 2-stroke motorcycles with timing details quoted have systems which actually varied effective port timing depending upon revs, load, etc. making the graphs a very incomplete description of their induction?

- Nick
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Old 07-17-2017, 01:26 PM   #15
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Several people are developing a
that is at least partially throttled by sliding the exhaust and transfer ports. Power valves on the exhaust port are very common.

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Old 07-18-2017, 06:08 AM   #16
Niels Abildgaard
 
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Quote:
Originally Posted by lohring View Post
The catch is that there's a much better solution to the emissions problem; electric vehicles. We'll see how that develops, but I expect that children looking at today's IC engines in museums will marvel at how we ever could build such complex things. In my model boat racing world, electric power is rapidly replacing IC engines. Electric model boats have held the ultimate speed record for years. Nostalgia for the past will keep modelers building wonderful replicas of IC and steam engines, but I don't see how IC engines can compete with electric power in all but the very largest vehicles as battery costs go down. Even your mower, chain saw, and weedeater will have cordless electric power.

Lohring Miller

man carrying aircrafts for more than one hour fligths will be IC some time yet.

http://www.homemodelenginemachinist....t=26218&page=2
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Old 07-18-2017, 08:33 AM   #17
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Hello Niels.


In the following it is further explained the difference the PatATE architecture brings to the 2-strokes.


Here is the port map of the famous Aprilia RS250 of 1999 (two cylinders in V90, oversquare design with 56mm bore and 50.6mm stroke):



The porting is focused on the faster blowdown: the “peak” (?) exhaust duration is 209.3 degrees and the “typical” (?) exhaust duration is 193.4 degrees, while the duration for the side transfer ports is only 129.6 degrees and the duration for the boost port is only 127.3 degrees.

The transfer is not only 64 degrees narrower than the exhaust, but its maximum (at the BDC) is not bigger than the maximum of the exhaust.


The above way of presenting the porting of a 2-stroke does not fit with the asymmetrical porting of the PatATE.


Here is a different presentation of the porting of a, say, modified to PatATE Aprilia RS 250:



The ports of the Aprilia RS250 are shown by black line.

The red triangular is the exhaust of the PatATE RS250, the blue triangular is the transfer of the PatATE RS250.


Going from top to bottom:

The exhaust of the PatATE starts opening substantially later (at, say, 87 degrees before the BDC) than the exhaust of the original RS250 (which opens at 105 / 97 degrees before the BDC).

The (red) exhaust opens at a higher rate than in the RS250.
Soon the exhaust area of the PatATE gets larger than the exhaust area of the RS250 (and as mentioned before, the Aprilia RS250 is focused on a larger exhaust area for the sake of a faster blowdown).

Some 20 degrees later the transfer (blue) of the PatATE starts opening at a very slow rate, giving time to the blowdown to complete. At the angle wherein all the transfer ports of the original RS250 open, the area of the transfer of the PatATE is still quite small, with a substantially smaller rate of increase.

At the BDC the rate of exhaust closing and the rate of transfer opening of the “PatATE” are about the same.
At the BDC the area of the exhaust port is still larger than the area of the original RS250 exhaust port.

As the piston moves towards the next (lower in the diagram, see the beige arrows) TDC, the transfer of the PatATE strengthens and the exhaust weakens / reduces until it closes completely.

For another 20, or so, degrees the transfer of the PatATE remains open to complete the transfer, while the exhaust is closed.

According the plot, the transfer remains open several degrees later than the transfer of the original RS250; also the exhaust of the RS250 remains open several degrees after the closing of the transfer of the PatATE.



On the same diagram, going from left to right is like moving along the periphery of the cylinder, with the zero angle being at the center / middle of the exhaust ports.

The exhaust of the RS250 covers, at maximum, about 120 degrees on the periphery of the cylinder, the transfer of the RS250 covers the rest cylinder but has, necessarily, substantially shorter height.

The exhaust and the transfer of the PatATE extend, each, for some 180 degrees along the periphery of the cylinder, but they are substantially asymmetrical relative to the BDC: the exhaust is significant before the BDC (blowdown, upped half of the plot) while the transfer is significant after the BDC (filling of the cylinder by the compressed gas in the crankcase, lower half of the plot).
The height of the transfer and the height of the exhaust are equal.



It is a long post.

However this is a different and useful way to present the porting (and not only) of a 2-stroke engine.

Even for the conventional 2-strokes, in a diagram like this one can put the relative pressures (or temperatures, or gas velocities etc) without the need to explain whether they refer to the downwards motion of the piston (expansion stroke) or to the upwards motion of the piston (compression stroke).

Thanks
Manolis Pattakos
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Old 07-18-2017, 10:17 AM   #18
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Quote:
Originally Posted by Niels Abildgaard View Post
man carrying aircrafts for more than one hour fligths will be IC some time yet.
And furthermore will continue to use tried and tested designs with as few modes of potential failure as possible in order to meet the requirements for aircraft engines.
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Old 07-18-2017, 01:42 PM   #19
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That might be true, but it all depends on battery development. There are some
being tested with current batteries. A respected engineer thinks
are possible with a little better batteries.

Lohring Miller

Quote:
Originally Posted by Niels Abildgaard View Post
man carrying aircrafts for more than one hour fligths will be IC some time yet.

http://www.homemodelenginemachinist....t=26218&page=2
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Old 07-18-2017, 03:03 PM   #20
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My bid for future 60 to 200 horsepower aircraft engines look more or less like this.

http://i.imgur.com/SOqAT4f.jpg


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