Singh Groove testing redux and CFD for groove positioning.

General engine tech -- Drag Racing to Circle Track

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Postby putztastics » Mon Apr 16, 2007 3:03 pm

CRE2004 wrote:Forgive me if this has been brought up or answered before, but has a before and after test been performed on this modification? Make 1/4 mile passes, pull heads, modify, make follow up passes?


I did a dyno test about a year ago, did you see the link a few posts up?

Note to SchmidtMotorWorks ==>> that test is the one I did about a year ago.


I view the grooves as something that can make a difference in a "use what you have with low octane pump gas" setting. Moving to race gas, high dollar parts and high dollar research would accomplish the same thing, eliminate detonation when on the edge, but some guys want to make pump gas work, that's the challange and that is where grooves might fit in.
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Postby Cammer » Mon Apr 16, 2007 3:36 pm

I do not want to step on any toes but:

Somender Singh patent #6,237,579 was issued May 29, 2001

http://en.wikipedia.org/wiki/Term_of_pa ... ted_States

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Postby putztastics » Mon Apr 16, 2007 3:51 pm

Cammer wrote:I do not want to step on any toes but:

Somender Singh patent #6,237,579 was issued May 29, 2001

http://en.wikipedia.org/wiki/Term_of_pa ... ted_States

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The dyno test I did was done with Somender Singh's permission.

The proposed second test will also hinge on his permission.
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New Dyno Test

Postby liquigas » Tue Apr 17, 2007 1:01 am

I can appreciate the desire to discover exactly what the grooves actually 'do' by themselves as an improvement to an unmodified engine..

but

Why not go the other direction? So far your test showed some variability in rpm ranges as far as benefit, but as I said a year ago, the real benefit of the groove is not in isolation from the rest of the tune settings.

With a mod like the groove, it seems unscientific to not take advantage of the benefits that the groove actually enables when making your comparison. That doesn't seem to make it into the conversation, but has a HUGE effect on the test results.

The symbiotic relationship between CR, Advance, Fuel type and Mixture produces a result that cannot necessarily be predicted by quantifying a single element separate from the rest. Besides, anyone actually using a groove will tune accordingly, not leave the engine at half capacity tunings when the groove allows so much more.

Out of fairness to the groove on this second test, what I mean by going the 'other direction' is: Why not compare the output of a max-tuned grooved head, to a max-tuned non-grooved head? You could even save some time and effort by using the same heads from last time. Singh seems to keep advocating the single groove as a really good starting point anyhow.

By testing multiple grooves before quantifying what a single groove is really capable of seems to defeat the purpose of discovery here.

[steps off soapbox] thanks for your resources though, it has answered and sparked a lot of questions for those of us without the resources to test this.

kdrolt

Postby kdrolt » Tue Apr 17, 2007 11:39 am

Rick360 wrote:
larrycavan wrote:...

I'm not certain if the grooves are funneling the flame to the charge that's laying in the quench area or laying a path for that charge to squeeze out to where there's a flame...or a combination of both..


I've read several of these threads about these and have always wondered if the grooves were providing the path into the quench area for the flame, instead of the other way around, just like you say Larry.


Flame speed is order(5 to 20 m/sec) in a non-boosted SI engine. So the above question could be re-worded as: which is faster, flame speed or forced convection in the groove?

IMO forced convection (in the groove) will be much greater than flame speed so the flame won't penetrate the jet (initially) but the jet will feed the flame rather quickly and foremost; the by-product of the jet will be turbulence and that will also help move the flame around.

The acoustic results are very interesting; EGT data taken at the same time would also be interesting. I will add that in an energy sense there is very little difference in the total energy between the with/without grooves, so there is not much extra power being made even though the grooved engine is quieter.

On the matter of more than one groove: remember that the more grooves you use, the less chamber surface area to squish, and therefore the less each groove can be forced. I understand placement of the groove(s) is key especially if you know something about how swirled the mixture is as the piston rises to TDC; IOW the groove probably always wants to be pointed twds the spark plug, but the angle used to get there can be good, indifferent, or bad depending on the direction of swirl.

Someone in one of the much-earlier threads made a comment that the groove method is probably a good thing to do on a head from the 1990s or earlier, especially for street use with pump gas. On race gas with newer heads, I'm not so sure.

I never could see how the area with the most distance (the groove) was supposed to "shoot" the fuel/air out. The widest gap approaching tdc would create less pressure than the rest of the quench area. Rick


See the "room full of basketballs" argument in one of the earlier (or earliest?) threads.

The flow in the entire squish region seeks to flow to the location of the least flow resistance. So if you provide a channel (the groove) then there will be a zone around the groove where the mixture will preferentially flow, and so you get a concentrated jet of mixture from the groove especially very late as the piston rises. The widest area (the groove gap) does taken away (as you said) from some of the squish area, so it's a compromise in design. You hope to gain more than you lose in power.

If it does help to speed the burn, then you could get away with using less spark advance and therefore absorb less work (and gain more shaft power) during the climb to TDC.... assuming it really does help.

On using the patented idea: it's published in the USPTO Gazette and it has a patent number --- that means (if the claims are written properly) that no one can gain fiscally from the idea without an agreement from Singh. But it also means that anyone can read the patent and try it for non profit use --- that's the point of patenting something and putting it in the public domain: to make it available to all so that progress occurs. Keeping it secret would inhibit commercial progress. FWIW.

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Re: New Dyno Test

Postby MadBill » Tue Apr 17, 2007 3:52 pm

liquigas wrote:I can appreciate the desire to discover exactly what the grooves actually 'do' by themselves as an improvement to an unmodified engine..

but

Why not go the other direction? So far your test showed some variability in rpm ranges as far as benefit, but as I said a year ago, the real benefit of the groove is not in isolation from the rest of the tune settings.

With a mod like the groove, it seems unscientific to not take advantage of the benefits that the groove actually enables when making your comparison. That doesn't seem to make it into the conversation, but has a HUGE effect on the test results.

The symbiotic relationship between CR, Advance, Fuel type and Mixture produces a result that cannot necessarily be predicted by quantifying a single element separate from the rest. Besides, anyone actually using a groove will tune accordingly, not leave the engine at half capacity tunings when the groove allows so much more.

Out of fairness to the groove on this second test, what I mean by going the 'other direction' is: Why not compare the output of a max-tuned grooved head, to a max-tuned non-grooved head? You could even save some time and effort by using the same heads from last time. Singh seems to keep advocating the single groove as a really good starting point anyhow.

By testing multiple grooves before quantifying what a single groove is really capable of seems to defeat the purpose of discovery here.

[steps off soapbox] thanks for your resources though, it has answered and sparked a lot of questions for those of us without the resources to test this.



I concur. It would be great if someone were to do a complete CFD workup to characterize the effect and optimize the configuration of the grooves on a popular engine combo, but realistically it's not going to happen. Alternatively, it's a cut 'n try program.

One approach would be something like:
o Put together a stout test engine with ~14:1 CR and a cam giving at least 240 psi cranking pressure.
o Rigorously controlling oil and coolant temp, etc., tweak spark and fuel for best possible steady-state power on 87 octane with no more than trace knock, at 500 RPM intervals from 1,500 RPM (or lowest revs that will accept WOT) to red line.
o Groove heads and repeat.
o Compare power, idle RPM, quality and vac., EGT, BSFC, jetting, SA, etc.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Postby liquigas » Tue Apr 17, 2007 5:36 pm

in an energy sense there is very little difference in the total energy between the with/without grooves, so there is not much extra power being made even though the grooved engine is quieter.


Last year's dyno test showed this +6 hp. for "free" with a tuning that took advantage of none of the groove's real world benefits.

If it does help to speed the burn, then you could get away with using less spark advance and therefore absorb less work (and gain more shaft power) during the climb to TDC.... assuming it really does help

(emphasis mine)

'Assuming' all of the results achieved so far are real and the absolute absence of any negative evidence, it would appear that something similar to burn acceleration is indeed happening. "more shaft power" is nothing trivial, especially in conjunction with increased turbulence.

That's exactly why it would be useful to see what the same engine with grooved heads is 'capable' of, using nothing more than the existing test equipment and altering the tuning settings.
-insert pithy comment here-

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Postby stevek » Tue Apr 17, 2007 8:36 pm

Gordon P. Blair's "Design and Simulation of Four Stroke Engines" SAE R-186

Page 471: Elevation view CFD of squish flow in a DI diesel engine.
Page 472: Plan view CFD of squish flow in a DI diesel engine.
Page 476: Actual in cylinder photo of 'vigorous squish action' at the end of a compression stroke.
Page 474 onwards: How to calculate the effect of squish in terms of: squish ratio; squish geometry - bore area, squish area, bowl area, bowl volume, squish band volume etc; squish velocity; squish kinetic energy; comparison and evaluation of squish velocities for various combustion chamber designs...lotsa stuff.

Covers both Gasoline and Diesel engines, so don't be put off by the 'D word'. Some simple diesel tech just made the gasoline engine a little better 'tis all! :wink:

There is a lot in there. It is a real gem of a book - look it up.

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Postby automotive breath » Tue Apr 17, 2007 8:42 pm

kdrolt wrote:... If it does help to speed the burn, then you could get away with using less
spark advance and therefore absorb less work (and gain more shaft power)
during the climb to TDC.... assuming it really does help...


Improvements in burn speed can help on both sides of TDC. The window
of opportunity for the pressure of expanding gases to exert force on the
piston top is very small. Engine efficiency is highest when we succeed at
burning a large portion of the air/fuel mixture early enough in the power
stroke to convert the energy created by the expanding gas in to usable
power at the crankshaft. With a burn thats too slow we succeed in
creating heat in the cooling system and exhaust as opposed to power.

The biggest opportunity for improvements in combustion is when burn
speed is at its lowest. Low RPM, lean mixture, weak ignition and exhaust
gas dilution from excessive overlap all contribute to the cause. It’s not
uncommon to see burn speed so slow that the mixture continues to burn
when the exhaust valve opens. In worse case scenario when the intake
valve opens, we have all seen flames come out of the carburetor on the
starting line. Others measure the temperature of fuel burning in the
header.

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Postby automotive breath » Tue Apr 17, 2007 9:43 pm

stevek wrote:...There is a lot in there. It is a real gem of a book - look it up.


I think I found this in Gordon P. Blair's "Design and Simulation of Four Stroke Engines"

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Postby LJW » Wed Apr 18, 2007 11:49 pm

stevek wrote:Gordon P. Blair's "Design and Simulation of Four Stroke Engines" SAE R-186

Page 474 onwards: How to calculate the effect of squish in terms of: squish ratio; squish geometry - bore area, squish area, bowl area, bowl volume, squish band volume etc; squish velocity; squish kinetic energy; comparison and evaluation of squish velocities for various combustion chamber designs...lotsa stuff.


There is a lot in there. It is a real gem of a book - look it up.



After reading page after page of speculation on this and other forums, stevek is the first to point out Prof. Blair's calculations of maximun squish velocities. :shock:
Two-Stroke tuners depend heavily on MSV calculations to configure engine characteristics. Squish velocity is like a lot of things in life, if a little bit's good, a lot more isn't necessarily better.

Larry

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Postby andrew1 » Thu Apr 19, 2007 1:17 pm

LJW wrote:
stevek wrote:Gordon P. Blair's "Design and Simulation of Four Stroke Engines" SAE R-186

Page 474 onwards: How to calculate the effect of squish in terms of: squish ratio; squish geometry - bore area, squish area, bowl area, bowl volume, squish band volume etc; squish velocity; squish kinetic energy; comparison and evaluation of squish velocities for various combustion chamber designs...lotsa stuff.


There is a lot in there. It is a real gem of a book - look it up.



After reading page after page of speculation on this and other forums, stevek is the first to point out Prof. Blair's calculations of maximun squish velocities. :shock:
Two-Stroke tuners depend heavily on MSV calculations to configure engine characteristics. Squish velocity is like a lot of things in life, if a little bit's good, a lot more isn't necessarily better.

Larry



I have read that excessive squish velocity can cause combustion problems with two stroke engines. Do you know what problems the excessive squish velocity causes? .and. Can too much squish velocity cause the same problems with four stroke engines? Two stroke engine squish area is not limited with the valves like a four stroke engines.

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Postby Unkl Ian » Thu Apr 19, 2007 1:29 pm

stevek wrote:Gordon P. Blair's "Design and Simulation of Four Stroke Engines" SAE R-186




Is this book still available new ?
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Postby allblowdup » Thu Apr 19, 2007 4:37 pm

In 2 strokes if you encounter to high of a squish velocity you can get deto. The gas has to be accelerated out of the squish area and as it is squished out it is compressed. From the compression comes heat and if it is compressed too much under acceleration then it can self ignite. Clearance and squish band width are both big factors. The best power is usually just before it starts to self ignite.
Mark

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Postby stevek » Thu Apr 19, 2007 6:12 pm

I bought his book about 6-7 months ago, from the SAE website.
http://www.sae.org/technical/books/R-186

My hardback copy arrived new, in shrink-wrapped plastic. It is an outstanding book - I thoroughly recommend you buy yourself a copy. Be warned, it is heavy on maths and engineering, not fluffy opinions. I consider this a good thing, but if you are not good with arithmetic - forget it!

Another good read is by Charles Fayette Taylor: "The Internal Combustion Engine in Theory and Practice". I recommend you buy both volumes. It is a little older and parts of it are now somewhat outdated, but it is still a good read if you want to build a very comprehensive background.


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