turbobluestreak Posted February 10, 2009 Share Posted February 10, 2009 It sounds like it’s as big of a pain like fluent but I can tell the user interface is friendlier. We have fluent at wright state university and it’s a pain to use. How long until we can see some dynamic results? tbs Quote Link to comment Share on other sites More sharing options...
MONZTER Posted February 10, 2009 Author Share Posted February 10, 2009 Dynamic results would be great, but I am still thinking about the proper simulation, and what would be the set-up. So say an engine is spinning 7000 RPM. the cam is at half speed so each valve opens about 58 times per second. How different would this dynamic situation be vs testing them all open at 1 time. Also, consider there would be no shock wave being created so the results would still be so so. In the modeler program (which we don’t have) you can actually dynamically open and close the valves, and then apply a moving mesh in the solver. We have an 16 processor cluster we run on, but I think this would even hurt it. What are your thoughts? Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 10, 2009 Share Posted February 10, 2009 Monzter, I'm a little confused about the theory behind the streamliners. Do you have any references to articles/papers on this? The intake stream liners appear to be parallel to the ports? I don't understand how these will promote swirl, if I'm correct in thinking that swirl is essentially turbulent flow. It looks to me like they would be trying to make the flow `straighter'. Or is the flow following a vortex pattern down the runners (hard to see from the vids sorry), and so these ridges are effectively presenting an angled sheet to the flow, resulting in it `tripping' over the ridge and becoming more turbulent that way? The exhaust ones also puzzle me. I understand that the flow is in the opposite direction, which is why they have a smooth face and where the intake ones are sharper. Are you trying to split the flow around the top of the ridge and make it straighter as it flows outwards? Also, do the ridges form some minor function in reducing the restriction caused by the valve protrusion? Again, as its the most important questions, do you have any recommended articles/further reading on this? Many thanks, Dave Quote Link to comment Share on other sites More sharing options...
turbobluestreak Posted February 11, 2009 Share Posted February 11, 2009 I didn't realize that it wouldn't create a shock wave in the test. I see where you're coming from with the valves being open that much it’s almost like they are just open constantly. I guess what I'm looking for the moving mesh to do is run through a combustion cycle to see intake and exhaust flows relative to piston/valve timing at an instant in time. tbs Quote Link to comment Share on other sites More sharing options...
MONZTER Posted February 11, 2009 Author Share Posted February 11, 2009 Monzter, I'm a little confused about the theory behind the streamliners. Do you have any references to articles/papers on this? I have attached something that might help The intake stream liners appear to be parallel to the ports? no not realy, they bend with the ports in the direction I want the flow to go. I want swirl in the combustion chamber not in the ports. In the ports I want clean laminar flow. I don't understand how these will promote swirl, if I'm correct in thinking that swirl is essentially turbulent flow. It looks to me like they would be trying to make the flow `straighter'. Or is the flow following a vortex pattern down the runners (hard to see from the vids sorry), and so these ridges are effectively presenting an angled sheet to the flow, resulting in it `tripping' over the ridge and becoming more turbulent that way? I think your talking more about tumble, a concept used in 4 valve pent roof chambers. Look up the articles from a guy called "The Old One" with endyne performance, good stuff. The exhaust ones also puzzle me. I understand that the flow is in the opposite direction, which is why they have a smooth face and where the intake ones are sharper. Are you trying to split the flow around the top of the ridge and make it straighter as it flows outwards? yep Also, do the ridges form some minor function in reducing the restriction caused by the valve protrusion? helps keep the flow smooth just like wind passing over an airplane wing Again, as its the most important questions, do you have any recommended articles/further reading on this? see attached Many thanks, Dave Here is a really good article on heads, that I found very clear and to the point. Give it a read and I can look into making some more pictures to better explain what I am trying to acomplish. ( I cant get it to upload any ideas? its 12 mb .zip file) Quote Link to comment Share on other sites More sharing options...
Careless Posted February 11, 2009 Share Posted February 11, 2009 Here is a really good article on heads, that I found very clear and to the point. Give it a read and I can look into making some more pictures to better explain what I am trying to acomplish. ( I cant get it to upload any ideas? its 12 mb .zip file) http://www.savefile.com i would like a copy of this too, please you r0x. best deep engine analysis on L's I've seen. Quote Link to comment Share on other sites More sharing options...
MONZTER Posted February 11, 2009 Author Share Posted February 11, 2009 Here is the link to the scan of the article http://www.savefile.com/files/1998523 Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 11, 2009 Share Posted February 11, 2009 Legend. Thanks Monzter. Will have a read. I was thinking about this on my walk to work, maybe you could approximate it by taking the integral of the cam lift function, ie, the average area under the curve, ie, root mean square. This might at least get a somewhat approximate measure of how open the valves are if you consider them not moving. This is obviously a poor estimation, but perhaps better than just running them at full open which might be a tad optimistic. Quite right about it not producing the shockwaves, but perhaps you could run the tests at an RPM where the ram-effect of the shockwave reflections is minimal, and thereby minimuze the infidelity in the simulation? Of course, I guess this assumes that the shockwaves have no other effect, which is in itself a large oversight I'd guess. Dave Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 11, 2009 Share Posted February 11, 2009 Makes sense re swirl in the chamber during compression, and not turbulence in the port during intake. Feel kinda stupid for not getting that. Are you sure they won't create a tumbling block? It looks to me in your vids that the flow is in a vortex as it proceeds down the ports. That doesn't mean its not laminar I think, just that its not flowing straight down the port. Also, it would also seem important to keep in mind that the place where flow is most likely to become turbulent in the port I think is the inside edge of the turn. Too sharp a turn and the air will separate there. Did you do any work focussing on that bit? Also, any close up vids of the end of the port/valve during this flow? Would be very interesting to see. Many thanks, Dave Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 12, 2009 Share Posted February 12, 2009 Also, can an admin please make this a sticky. Dave Quote Link to comment Share on other sites More sharing options...
X64v Posted February 12, 2009 Share Posted February 12, 2009 I was thinking about this on my walk to work, maybe you could approximate it by taking the integral of the cam lift function, ie, the average area under the curve, ie, root mean square. This might at least get a somewhat approximate measure of how open the valves are if you consider them not moving. I was thinking this sounded like at least a closer approximation. Though the dynamic model would be much better, even without shockwave effects, because the 'average' setting wouldn't show you any problems that might arise when the valve lift perhaps passes 'x' amount of lift. +1 on the sticky. Quote Link to comment Share on other sites More sharing options...
tfreer85 Posted February 12, 2009 Share Posted February 12, 2009 I want your job and career + throw in the car and I'll let you live....now givit! Seriously, great work Monzter. Quote Link to comment Share on other sites More sharing options...
MONZTER Posted February 12, 2009 Author Share Posted February 12, 2009 here are some more pics, close up on the valve head area. click on the picture for the super huge view. I also uploaded some more video, but Youtube really destroys the quality:icon13: enjoy Quote Link to comment Share on other sites More sharing options...
Daeron Posted February 12, 2009 Share Posted February 12, 2009 Many thanks for the Vizard article!! I think I have heard this referenced but I have yet to find it. It is well worth jumping through the hoops to register to download it!! Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 12, 2009 Share Posted February 12, 2009 Hmm.. i didn't have to jump through any hoops: Direct link: http://dl3u.savefile.com/f43d3ac330d2e8056c3bfd867a0bb750/Document.pdf Monzter, cheers for the close ups. So the flow is not in a vortex shape, its not tumbling over the ridges, and the valve is quite shrouded by the bore. I'll finish reading the Vizard article before I post any more naive questions. Dave Quote Link to comment Share on other sites More sharing options...
1artworkz Posted February 12, 2009 Share Posted February 12, 2009 Here is a really good article on heads, that I found very clear and to the point. Give it a read and I can look into making some more pictures to better explain what I am trying to accomplish. (I can't get it to upload any ideas? its 12 mb .zip file) He is a better and smaller version that you can print on 8.5-11" paper. http://www.garymolitor.com/head-porting.pdf Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted February 14, 2009 Share Posted February 14, 2009 What if... instead of trimming down the valve guide support/streamliner deal (I don't know what its actually called), you added material there in the shape of an airfoil to shroud as much of the valve stem as possible? In free-stream I think the lower Cd would more than make up for the increase frontal area of such a shroud, but I'm not sure what the effect would be when you've got the limited cross sectional area of a port. It seems like most of the air will be following the outer radius of the port, so maybe such a streamlined projection would only need to extend to about the port centerline. Adding material there doesn't seem like a very easy job though. I just had knee surgery... so if this idea really sucks, I blame the pain killers =) Quote Link to comment Share on other sites More sharing options...
MONZTER Posted February 14, 2009 Author Share Posted February 14, 2009 What if... instead of trimming down the valve guide support/streamliner deal (I don't know what its actually called), you added material there in the shape of an airfoil to shroud as much of the valve stem as possible? In free-stream I think the lower Cd would more than make up for the increase frontal area of such a shroud, but I'm not sure what the effect would be when you've got the limited cross sectional area of a port. It seems like most of the air will be following the outer radius of the port, so maybe such a streamlined projection would only need to extend to about the port centerline. Adding material there doesn't seem like a very easy job though. I just had knee surgery... so if this idea really sucks, I blame the pain killers =) Ya that make sence. This is what I did, the guide supports are only as wide as the guides, but smmoth out the front and back of the guide to make them more streamlined. You can see this in the Cad model in this view you can see how clean the flow around the guide boss is Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted February 16, 2009 Share Posted February 16, 2009 Normally a cylindrical shape in an air stream produces a large wake behind it. My idea was to shroud as much of the valve stem as possible to avoid that. After looking at your CFD I think that the port walls prevent the wake from forming, and keep the air pretty laminar as it flows around the valve stem, making my idea probably not very worthwhile. Oh well, it would be interesting to see if it did anything. =) Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 16, 2009 Share Posted February 16, 2009 Does your CFD software tell you a CFM rating at a certain pressure? If so you could compare to a couple flow benches to see how it pertains to real life. If so, what sort of flow are you looking at? If this was already covered and I missed it, sorry. Quote Link to comment Share on other sites More sharing options...
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