2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello Henry.

In my last post it was mentioned the:

“Quasi-constant volume spark ignition combustion” paper:

(Copyright 2009, SAE International):

https://dspace.lboro.ac.uk/dspace-jspui ... 5b2%5d.pdf



Three universities of UK are involved in the project:

Rui Chen and Edward Winward
Loughborough University, UK

Paul Stewart
University of Salford, UK

Ben Taylor and Dan Gladwin
Sheffield University, UK



Here is the pattakon OPRE Tilting 2-stroke prototype engine:



(333 cc, bore 84mm, stroke 30+30=60mm
(same bore to stroke ratio with BMW's boxer R1200GS of 2013)
weight: 8.5Kp (19lb) without the exhaust pipe and the carburetor
height: 250mm)

and here is an animation of it:



and here is a plot showing the comparison of the piston motion profile of the OPRE with 1.3:1 con-rod to stroke ratio (blue curve) in comparison to a conventional (red curve) having 2.0:1 con-rod to stroke ratio:




(for more: http://www.pattakon.com/pattakonTilting.htm )


Here is an application of the OPRE Tilting that could change the world:







According the lab tests and the analysis presented in the above mentioned SAE paper of the three UK universities, the OPRE Tilting is a great engine design, from many viewpoints.

Please do read the paper having the spark ignition OPRE Tilting in mind.


Thanks
Manolis Pattakos.

[manolis]

Hello J.A.W.

You write:
“& some late model cars list - fairly shocking - possible excessive oil consumption rates as 'acceptable' - in handbook blurbs..
(Such as BMW officially advising that consumption/loss - of a litre per thousand kilometres - is within book specification!)”


A typical problem / issue for the Honda Civic VTEC (B16A2 engine) sport cars, too (typical subject for discussion in many Honda forums).

(like the one hosting the pattakon VVA-roller prototype:





youtube video at https://www.youtube.com/watch?v=-zzW8YkReLU )



If a BMW is OK consuming one liter per thousand of kilometers, something is wrong.


With 7 lit of fuel per 100Km (a typical fuel consumption), this means that for every 70 liters of fuel, the BMW is OK to consume 1 lit of lubricant!

70 to 1 fuel to oil ratio is fine for most 2-strokes.

1:70=1.5%, i.e. more than what the giant marine 2-stroke engines consume.

Achates Power claims, for their Opposed Pistons with the side crankshafts, some ten times lower lubricant consumption.

Thanks
Manolis Pattakos

[henry]

Manolis

The Loughborough research paper does suggest that there are likely to be efficiency advantages to a longer dwell at TDC but I'm not sure that too much can be read into it given they only ran at a slow tick over.

It seems a shame that they didn't talk to you at the conference. If nothing else they could have used your experience to calibrate their altogether more complex, and hence potentially erroneous system.

[henry]

Manolis: the advantages of the increased dwell at TDC of your engine are an obviously important claim. The most significant challenge for diesel engine manufacturers today appears to be control of NOx and particulates. Do you know of any research that would suggest that the longer mix and burn you anticipate would help, or hinder, or make no difference to the pursuit of lowering these emissions?

On related point, given this slow approach to TDC is there a possibility that the specific point of combustion initiation might vary more than a more conventional design? I assume that the combustion actually starts over a range of pressure/temperature values and in your design these seem likely to occur over a wider range of crank angle. Might this have noise and vibration repercussions?

It might suit RCCI combustion, who really knows without simulation using accurate combustion models what that piston motion about tdc can be advantageous for, given the high inertial mass slower engine speeds are likely it's more efficient operation, slowing the piston velocity further seems counter intuitive. There maybe some CI combustion mode that suits this. RCCI is dual fuel mixing the characteristics of two fuels. Used to achieve better emmisions and power.

Normally one defines these issues first then designs an engine with the features to best meet goals, has all the performance metrics identified at the start so they can be used to verify design. Without you are not verify anything. Is it better? No measure of success.

There are dozens of metrics that need to be defined,
Crankcase pressure, blow-by gasses, temperature. Imep, Bmep, Bmep/Imep ratio, heat loss, thermal monitoring of hot spots and expansion, fatigue.

The list is huge, I have a huge information model schema that holds the Central point of truth for all engine revisions. It's big data on its own.

A measurement protocol is needed to verify each one or your just playing, no one can take it seriously without metrics to assess it by.

Engine control strategies to meet regulations or is it just another dieselgate. One really needs to control liner temperature for emmisions and effective combustion they are the same really
Otherwise it's an exercise in turning a large piece of metal into smaller pieces.

RCCI looks interesting although the practicalities of duel fuel might be a challenge for the average motorist. I'm not sure why you think it would be better suited to a long dwell at TDC, perhaps you could elaborate.

You again assert that the high reciprocating inertia would mean Manolis' design would need to operate at low speed. The first time round he responded with some data and calculated values that refute that assertion. You might do him the courtesy of explaining which of his numbers is wrong or misinterpreted.

You have also asserted, in an earlier post, that the longer dwell would inevitably lead to slow combustion based on an expectation of low turbulence. Have you looked at the combustion chamber design in this engine? It has a very compact combustion space formed in the pistons with very large squish areas driving turbulence.

The Loughborough paper Manolis refers to gives some indication of the theoretical benefits from increasing dwell angle in relation to the Otto cycle. Although at very low speed their initial results support the theory. They certainly don't disprove it.

[gruntguru]

The problem gets severe (cannot be hidden) at the “higher” revs wherein the lack of time causes the steep drop of the torque.

For instance, here is a dyno from a Subaru Boxer Diesel:

http://www.pattakon.com/tempman/Subaru_ ... l_Dyno.jpg

From 3,600rpm (peak power) to 4,400rpm (i.e. within only 800rpm) the torque drops by one third.

The steep drop you are referring to is due to reduced fuelling to avoid overspeed. (not denying that falling efficiency due to limited time for combustion also exists. "Overspeed" could be a mechanical limitation or one of reduced efficiency) In the old days of course this was a mechanical system and was referred to as a governor. Nowadays it is simply mapped into the engine management computer.

[manolis]

Hello Gruntguru


The spark ignition 2.0 liter Boxer of Subaru (2013), with 86mm bore and 86mm stroke, seems to run reliably until 7,500rpm (peak power at 7,000rpm):





Quote from http://www.subaru.com.mt/tec_boxer.html



“2.0-LITRE DOHC TURBO SUBARU BOXER DIESEL

The world's first commercial Horizontally-Opposed Diesel Engine developed for passenger vehicles is the SUBARU BOXER DIESEL. When petrol engines are converted to diesel, strengthening of the engine block usually makes the engine bigger and heavier. The SUBARU BOXER, however, was originally designed with rigidity in mind, allowing the 92.0 mm x 75.0 mm bore and stroke of the 2.0-litre petrol four-cylinder engine to be changed to a square 86.0 mm x 86.0 mm design. The result is a more compact combustion chamber and greater fuel efficiency, and combined with a higher pressure common rail fuel injection, an improved oxidizing catalyst with closed Diesel Particulate Filter (DPF), a variable nozzle turbo and electric power steering, these all help to reduce fuel consumption and CO2 emissions. Ceramic glow plugs also quicken starting in cold weather. And whilst meeting the ultra-clean EURO5 emission standards, the engine delivers even more torque compared to previous models. A prodigious 350-Nm of peak torque is delivered at a lower 1,600 rpm – providing smooth, free-breathing performance at any speed. These advantages are evidence of the vision that Subaru has in using the Horizontally-Opposed Engine.”

End of Quote.


You write: “The steep drop you are referring to is due to reduced fuelling to avoid overspeed.”

But we talk for only 4,000rpm.
And the “same” engine can operate above 6,500rpm “for ever”.

From another viewpoint: they should protect the driver and the passengers more than the engine: in a steep uphill, during an overtake, the overrevving (without such drop of power / torque) is safety.


By the way, according the theory in the previous posts, if in the Subaru Diesel it was used the “pulling rod” architecture (substantially longer dwell of the piston at the Combustion Dead Center) the Power – Torque plot would change to something like:



Even if the engine could not rev reliably above 4,400rpm, even then the advantages are obvious.


Thanks
Manolis Pattakos

[J.A.W.]

Hi Manolis, & if the CI Subaru only makes power to ~4,000 rpm - then it has no real excuse for not being a 2T..
..since not only could it actually get some work done*, but it could perhaps be somewhat excused re: its oil consumption..

Subaru are noted as excessive oil consumption offenders, & their complex 'boxer' mills have never been fuel miserly either..

www.consumerreports.org/cro/magazine/20 ... /index.htm

* I do note the data you have provided re: potential of the mechanical advantage of your design..

[63l8qrrfy6]

You have shared a link to show that a 2 stroke has similar HC emissions to a 4 stroke producing the same power.

You used that as an argument to claim that oil consumption must be the same too. I explained why I think that comparison is unreliable.

[J.A.W.]

I noted current marine engines, but it appears you missed the boat M-f..

The contention was.. ( & you'd know this ..if you were paying due attention.. rather than trolling)..
..that engines with ports cut into their sleeves, per se - have excess oil consumption & HC emissions problems..
..but quite evidently, that aint necessarily so..

[63l8qrrfy6]

I noted current marine engines, but it appears you missed the boat M-f..

The contention was.. ( & you'd know this ..if you were paying due attention.. rather than trolling)..
..that engines with ports cut into their sleeves, per se - have excess oil consumption & HC emissions problems..
..but quite evidently, that aint necessarily so..

Do you have oil consumption data for the 2 engines then ?

[J.A.W.]

Penrite state that their synthetic 2T injection oil for current outboards can be used at a ratio of 100-to-1 ( fuel-to-oil).
I can operate via the HCCI function while trolling for fish at low speed .. but your version of trolling is much slower yet..

[63l8qrrfy6]

Penrite state that their synthetic 2T injection oil for current outboards can be used at a ratio of 100-to-1 ( fuel-to-oil).

That would help if you would state the fuel consumption and also point to a 4 stroke of similar power with a known oil consumption!

[63l8qrrfy6]

[quote=J.A.W.
[/quote]

I did look it up and so far 2 strokes consume more oil than equivalent 4 strokes.
I found nothing to say that they are even remotely similar.

This is the truth and it has been known for decades, regardless of your convoluted arguments.

[63l8qrrfy6]

I drive a 2016 M2 and changed the oil after 1500 miles of running the engine in. It's now close to 8k miles of serious abuse and it is not showing a loss at all (yes it's an electronic level, don't know how accurate it is).

My daily is a 6 year old 320D which has just over 120k miles on it - has never required topping up between services.
I never drove a car that burned 1 lire per 1000 km and I did drive quite a few cars.

Regular changes are due to oil degradation, they have nothing to do with oil consumption.

There might be the odd engine out there, but normal cars do not consume 1l/1000 km !

[manolis]

Hello J.A.W.

Either 2-stroke or 4-stroke, the lube specific consumption should have the same limit.


Supposing a fuel consumption of 7lt/100Km, according the following plot of Achates Power (2012):



a car equipped with their side-crankshaft Opposed Piston 2-stroke engine cannot consume more than 70*0.00227=0.16liters of lubricant per 1,000Km.

Note: the 0.227% is the maximum lube consumption.

(the above 0.16liters of lubricant per 1,000Km drops to 0.124l/1,000Km if the average, and not the maximum, lubricant consumption is used in the calculation).


A BMW 4-stroke car engine having more than six times higher lubricant consumption than a 2-stroke engine, is a scandal.


Scandal or not, if you try to communicate with BMW’s R&D, or Subaru’s R&D, or Honda’s R&D about the excessive lubricant consumption of their cars (and the air pollution they cause), I am sure they will not reply (at least not technically).
Unless the sender is an organization like the EPA of USA, and the letter is asking them to fix the problem under the threat of a few billion dollars fine.


The big engine makers have better things to do than answering technical letters.


The strange thing is that even small companies refuse to answer in technical questions, even a few months before bankrupting.

In the past we tried several times to communicate with EcoMotors (OPOC). Now they appear closed / bankrupted.

Also with Mce-5 France (i-VCR). They are closed / bankrupted for years.

Also with Martin JetPack. For several months they appear idle.

Etc.


We are trying to communicate with Achates Power.

Thanks
Manolis Pattakos