ShaunSG

iTrader: (1)

Sorry, and your effort in splitting the thread is much appreciated. I have much more to say.

Kind regards

ShaunSG

iTrader: (1)

No it doesn't. As the paper itself states the plug bias led to it and even then 23 is only part of the piston periphery. What about the other 3 areas? It is even less of an issue on a pentroof 4V with more or less centered plug.

Also the simulation doesn't include the stratification of the air fuel mix. When you spread dense fuel out across a hot surface, you cool it. Whatever temperatures there and in the area are reduced. If you would rather run the piston with hot zones with no squish and no quench, then I really don't know what to say.

As above, that paper doesn't take into account the charge stratification and even if it did, all it means that quench effect in that engine in that portion of the cylinder isn't effective.

Yes, IF. The thing is one has no proof for, or against it, then one should continue to listen to what the industry avatars have said about it. These stalwarts possessing the dedication, brains, balance, to get to where they are today and having always demonstrated consistent objectiveness in all they do and say.

The heating by compression is a given, but doesn't at all contradict that the energy absorbed by the fuel in its phase transition cools the areas where the spread and/or mixing occurs.

As above, non centered plug, no stratification simulated.

We don't even need to get into that because as long as flow qualities and effects are different between the two poles, then we need to differentiate. Besides that, the whole industry differentiates. I can tell you right now that Mercedes, Chrysler, BMW, General Motors, Honda and Mitsubishi differentiate, and it is the production car guys like these who are most interested in these motions. The racing guys care less but everyone I've talked to differentiates too.

Toyota in that paper should have used the term "charge motion inclination". They could have easily and just as erroneously picked "tumble motion inclination" but they didn't.

In an earlier post I listed 3 very real differences between tumble and flow.

I don't want to speak for others, but I'd call that 30 degrees off axis swirl. Only around 45 degrees do things get tough to differentiate - at which point it is easy to go to raw inclination angles in that very narrow range.

How do you differentiate between a road race car and a drag race car? Same issue. Everyone can and should differentiate between them and it is extremely easy to do so close to either in its purest form, the area where you can't or shouldn't differentiate them using either term, is very narrow and almost never seen.


The same one I mentiond in PM to you long ago regarding rotary CI engine.

ShaunSG

iTrader: (1)

It is very funny you telling me that what I call tumble, Chrysler would call swirl. Reason I say this is because I have heard Chrysler's lead engineer for designing cylinder heads and studying flow dynamics in heads and in-cylinder speak at length on these subjects, both in terms of production and race car applications, aided by flow visualizations from multiple tests. It turns out my definition is the same as his definition, which is in agreement with anyone I've ever talked to who is involved in with racing.

So I would be extremely surprised if you could show me Chrysler designed these pistons for swirl. As I said, there is no geometric bias to the hump design I can see, and unless the inclined area is tilted across its length, there is no way it is physically generating swirl as the industry defines it.



[Edit: I'd still like to see your paint diagrams out of curiousity. Besides that.. is there any way we can stop here and just agree to disagree? I think I've spent too much time on this issue which is quite frankly inconsequential to me as far foward as I can see. ]

Ron

Shaun is right. The industry defines swirl as charge motion about the cylinder's axis.

Or, what you get in fudge ripple ice cream.

SaabTuner

I think you misunderstood what I meant. What I meant was that the distance from the spark plug had more to do with the temperature of the gas over the surface of the piston than did the areas referred to as "quench pads". Because of that, it's hard to prove that adding quench pads to an already cool area, far from the spark plug, will cause any additional cooling.

The farthest parts of the piston from the spark plug with always be the coolest. The only way to tell if a quench pad is working is to see if it is cooler than a place on the piston of similar distance from the spark plug. In the case of the 2.2L Chrysler, zone 23 and zone 1 were similar distances from the spark plug.

If zone 23's quench pad were doing any significant cooling, it should have been cooler than zone 1. Since it wasn't, and both areas were cooling the combustion chamber in more or less equal amounts, how do you justify calling it a quench pad any more than calling zone 1 a "quench area"?

I know you don't have as much time as I do to read things over carefully, but page 5 has a comparison of simulated and measured temperatures for the piston surface. On the whole, they were very close. Either the simulation took into account stratification, or the stratification had relatively little effect on temperature.

I just can't agree with that. There are sooooo many other variable effects of the motion based on everything from combustion chamber design to swirl ratio. If we're going to come up with names for every kind of gasseous spinning motion and axis, we'd better start thinking up a few more names.

Obviously Toyota didn't differentiate.

In fact, in that paper you might have noticed that "swirl" and "tumble" had rather similar mean turbulence for that particular engine while the 35-45* inclination angles were drastically different. So if your determination for qualifying the use of a new name for a spinning motion is based on the motions effects, we really need to find a name for the motions between "swirl" and "tumble", since those motions can be more seperated from either pole than the poles are from eachother.

I hadn't meant to imply that Chrysler calls it swirl, merely instead, that I call it swirl. Apparently Toyota sometimes doesn't differentiate. So at least I'm not completely alone in this.

Same here. I'll probably end up drawing them on paper and scanning them later. Basically the volume on the smaller side of the hump shrinks faster than the larger side, so it forces air-fuel mixture out of the smaller area and into the larger one. Like I said, you'd call it tumble, though SCC called it swirl and I'd call it swirl.

Anyway, may as well just agree to disagree. No sense in bickering since this is getting rather subjective.

-Adrian

trinydex

iTrader: (12)

ok it's taken me a bit to catch up on all the terminology... but what the hell is the deal here?

the function of a quench pad is to reduce detonation, whether it be from removing the piston further from the spark plug or not doesn't really matter does it? and the reason they don't just move the piston (flat top) further from the head is so they can take advantage of squish and maximum piston evacuation.

and on taking advantage of squish... squish is causing turbulence at the sides of the piston squishing the gas and or air mixture towards everywhere else... how this cools or rather reduces detonation may be a mystery but the fact is it's doing it in a different way... so you must differentiate... one is an aero/fluiddynamics phenomemon and the other is possibly as saab has said... a geometric phenomenon.

as far as swirl and tumble go... they are what they are... you differentiate... you have to. the intermediaries will always be intermediatries. that's why we have parallel and perpendicular right? we don't call them both perpendicular just because there are intermediate angles... we call the intermediate angles by their respective numbers. do you have to make up a name for the stuff that is inbetween? no... why would you? you call it tumble or swirl plus an angle and if it's 45 they can call it critical swirl or tumble or mixed swirl and tumble.

additionally... with swirl you are capable of creating boundary layer vortices which is completely different from a tumble type vortex which would not hold to any boundary layer except when it "tumbles" down to join it, also with tumble you can have break away vortices that just propagate in "mid air" which would probably aid in fuel atomization and cleaner, more complete burn. with swirl an "upward" propagating vortex would take away from the boundary layer and then cause some disruption there (which may be good or bad, shrugs)

all this talk about nomenclature....

ShaunSG

iTrader: (1)

Thank you Trinydex!

trinydex

iTrader: (12)

well thank you guys for the discussion... cuz the theory is much elucidated now for all to see.

SaabTuner

Noooo no no. Not farther DOWN from the spark plug, farther to the side. Sorry for not being clearer before!

The squish's reduction in detonation is obvious and would not otherwise exist. The problem I have with "quench" is that the edges of the piston would cool the combustion charge just as much without any "quench pads" per se, because the end-gas is almost always in the region farthest from the spark plug (laterally) and that region is almost always the coolest region, quench pads or not. It's like calling your coolant "quench fluid" because it helps cool the end-gas.

As for swirl/tumble ...

Can we be pragmatic and compromise? I offer this compromise:

Meriam-Webster defines to swirl as "to move with an eddying or whirling motion". So how about this, ANY swirling motion in the combustion chamber can be called swirl BUT only swirling perpendicular to the cyllinder's axis, or a swirling motion which has a mobile center/axis, can be called tumble? That way tumble is a specific form of swirl.

My only objection was to the idea that tumble is a totally different phenomenon when it is spinning gasses just as swirl is spinning gasses. Tumble is just a certain kind of swirl.

Think of it like primates and humans. You can call any animal of the order primata a primate and be perfectly correct, but you can only call us human.

Seem fair enough?

zze86

iTrader: (8)

no, no please keep this thread as it is. though I haven't read most of this yet, it's interesting to see how the conversation develops and where it leads. Also I get the feeling if you do have another thread it'll just go off-topic as well.

going a bit off-topic isn't necessarily a bad thing in this case....

trinydex

iTrader: (12)

the only problem i have with that kind of definition of swirl and tumble is the fact that it still does not address the vortices associated with the different types of air movement. like the examples i cited, swirl and tumble can have vastly different aerodynamic/fluiddynamic effects or movements, and the combination of both must incorperate both types (or definitions) of movement and you can only analyze and attribute certain characteristics (of movement) with the "ideal" or paragon movement of the air... pure tumble or pure swirl.

it would be totally unfair to tumble to say that swirl causes rejoining of piston boundary layer gases from the "side wall" gases. and it'd be unfair to swirl to say that tumble makes the boundary layer adhere to the piston. both these affects could help sweep "stuck" fuel on the piston and also cool or heat the piston depending on where you are in the stroke of things, but if you had problems with only one... you'd have to specifically address it and if you did not differentiate then you would not know which to "fix".

i wouldn't say either is a specific case of the other... they're the same equivalent types of fluid motion in 3 dimentional space. each has it's unique set of freedoms and each has its unique set of limitations. and a linear combination of both gets you real complicated real world simulations.

as for quench... i'm sketchy to say the least about the details of how it actually reduces detonation. but i came across some reading from a guy that worked at one of the livermore labs circa 96 and they were doing some engine testing... they used a variable height cylinder head and brought it closer and closer to the piston. the quench padded pistons would reduce the detonation significantly and allow the head to be brought much closer to the piston, at one point they could have the piston touching the cylinder head at which point they called it maximum quench.

the problem with the edges of the piston cooling the charge or end gas or whatever is that you have a limit as to how close you can bring a flat piston to the head... with a quench pad (which you could call a coolant pad by your analogy, which i think may be legitimate because if there's maximum quench as a terminology then you could call it maximum cooled) you can bring the piston closer to the head and as i said before that aids in cylinder evacuation, plays a role in displacement geometry and also makes possible the maximum exploitation of squish.

EVOONYOASS

iTrader: (2)

Man I wish I knew what they hell ya'll are talking about, but it sounds interesting to say the least.

Anybody want to build my engine for free and explain it to me as you build it? I'll buy the beer.

trinydex

iTrader: (12)

uhm... have you seen that one video of the guy puttin' together the 4g63 together? if you haven't i think i can send it to you...

SaabTuner

Different vortices? Perhaps you're an FD major and I am not, but I have read my fair share of Fluid Dynamics (baroclinic generation forms, Rankine-Hugoniot jump condt. etc.) and it makes no sense to me that you'd have drastically different boundary layer properties. True the main vortex would "stick" to the piston if generated cleanly in swirl, but it could just stick to the cyllinder walls in tumble, depending on how it is generated. Because the primary vortex would be rotating in a different direction, the massflow currents around the boundary layers could be slightly, or dramatically, different, but it would depend on combustion chamber design and piston design as much as vortex angle.

If you really needed to "fix" something relating to swirl, you'll need to know exact swirl inclination, swirl ratio, and a whole host of other properties that you could not ever derive from merely a differentiation between "swirl" and "tumble". Aside from that, I originally intended only that the term "swirl" should be applied to all cases of swirling motion and that a more specific differentiation for most people would be merely an "intellectual excercise" since the difference is not meaningfull to most people.

So you wouldn't say that "tumble" is a form of spinning or swirling in a gas?

hahaha. They called it "maximum quench"? They didn't even change the quench at all; they changed the "squish". I guess that shows how well those terms are differentiated by "professionals".

You cannot change the cooling effect of the combustion chamber without either changing its temperature differential, coefficient of thermal conductivity, or surface area. They actually reduced the surface area, though the temperature differential might have increased. In either case, if the temperature differential increased, it was due to increased compression, not the quench pads since the differential would have increased across the entire piston surface.

I'm not saying that quench pads do not exist. I'm saying that they do not do any more "cooling" than the rest of the piston at a similar distance from the spark plug. Therefore, they do not do any more "quenching" than any other part of the piston. So they should be called squish pads and I will stand by that until I see some evidence that the "quench pads" do significantly more cooling than other areas of the piston, or even the head, at similar distances from the spark plug, already do.

But you know, we've spent so much time arguing about this. If we're not carefull, we're gonna get all mad and start hating on eachother. That's NOT what I wanted. I may be stubborn, and I refuse to back down without evidence, but I'm not trying to be an azz about it. I just don't agree. That's ALL.

So let's all sit back, get a few drinks, and enjoy being able to talk about this stuff in the first place.

Cheers,
-Adrian

ShaunSG

iTrader: (1)

Ah, a crisp Saturday morning.

Adrian, you can read yourself into a ditch if you don't reference and combine it to more pratical approaches - which is what the top people in the industry do. Theory can only take you so far. For example, the guys who have an extreme grasp of fluid dynamics and lots of reasearch money still combine it with flowbench testing, swirl and tumble rigs, PPT and CFD. What do you know that the top guys don't? This overconfidence is typical of engineers in training or fresh graduate engineers that have a general spirit of unwillingess to include actual and practical testing and work as a team and not alone.

If you want to cling to what one 16 year old paper originally written in Japanse that perhaps had that specific term mis-translated, unite yourself with SCC magazine (junk), and ignore what the OEM and race industries agree on today, then it is your loss. English Dictionary definition of a scientific term vs actual industry agreement? Please.. you're clutching at straws. There's no way a dictionary can keep up with evolution in these niches.

1 and 23 are not equidistant. Look at the diagram and see where the cross marked S is. 1 is also a valve relief area that has inherent quenching properites. As for stratifaction and temps. Where are the details on that engine in terms of what type of fuelling it ran? If it was a premixed or preheated mixture then there would be near perfect mixing and no stratification. Look at the RPM they tested at. I am sure the test engine is no where near a race type engine that has big poor SMD injectors, low injector location for response overfuel or periodic overfuel for cylinder cooling and higher overall thermal loads. You are trying to infer too much from a test that was meant to test other things. This is similar to previous turbo F1 thread where you shaped ideas around an assumption.