Laminar vs turbulent flow.. January 25, 2016 03:07PM
Doing some reading, In a tube or pipe laminar flow will move more fluid than turbulent flow.. This is a well researched subject. Will this work downstream from a turbocharger? I assume that down stream from the turbo the air is VERY turbulent. Has anyone experimented with this?
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Re: Laminar vs turbulent flow.. January 25, 2016 04:15PM
I believe you are talking in a diesel application, right?

Not sure on the turbo exit characteristics, I'd stand to be educated. I would be curious how fluid introduction matters. Given a diesel premise, would laminar flow be best? Or a turbulent flow that intermixes better with water-injection deriving a better cooling replacing maximum flow rates with a better-by-volume-density flow?

I have no first-hand knowledge either way, but please teach me.

CP
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Re: Laminar vs turbulent flow.. January 25, 2016 10:24PM
Radial, or swirling flow, is slow. The faster you can get to laminar flow out the exhaust the better. The shortest way to get gasses out of the exhaust is when they are flowing in a straight line.

There's a reason for all these oversized stacks on tractors these days.They serve a purpose.
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Re: Laminar vs turbulent flow.. January 26, 2016 02:27AM
There's a lot to be said about laminar flow. I ran a cam driven fuel pump on a N/A V-8 engine that was said to be too small. It worked fine because I made sure that all turns and fittings were as non-restrictive as possible. The idea behind what I did was to decrease the amount of fuel returning to the tank, which caused agitation of the fuel in the tank. Plus obviously, the smaller fuel pump would require less horsepower to operate. I actually taught classes in hydraulic and pneumatics at one time, and did a lot of research into turbulent vs. laminar flow along with taking some very advanced courses offered by manufacturers. The air exiting a turbocharger compressor discharge (exducer) has a tornado effect with the swirling of the discharge air. Flow (preceding post) is correct in stating the fact about swirling air vs. straight flow. The compressor discharge would be better served with the compressed air moving in as straight as line as possible. This can also improve what is referred to as a "boundary layer". One way to decrease the tornado effect of the air exiting the compressor is too created and expansion area. This allows the air to stabilize due to the larger cross sectional area. While it is true there will be a reduction in velocity of the air stream (Bernoulli's Principle) when the turbulent compressed air reaches this point, the flow will straighten out and regain it's pressure aft of the expansion area. With the air now flowing in a more stable state, the air along the internal walls of the plumbing system will slow down, decreasing parasitic drag on the walls. This allows flow from just above the boundary layer to flow faster with less restriction. This should result in a more stable air flow, and decreased heat (minimal reduction) generated by the flow These are part of the theories that turbine engines are designed on, and we know that designers of turbine engines work diligently to design them as efficient as possible. Food for though and my two cents worth.
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Re: Laminar vs turbulent flow.. January 26, 2016 03:40AM
IF there was a way to build a devise in the crossover pipe that would align the air to eliminate swirl the flow would be greater?. Can we assume that the parasitic drag caused by swirl contributes to heating of the compressed air? AND how large would a turbulent air eliminator have to be to actually smooth the huge mass of air generated by a competition turbocharger on a diesel engine?
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Re: Laminar vs turbulent flow.. January 26, 2016 05:01AM
Gonzo 1066, I doubt there is much heat generated due to the turbulence in the compressor discharge. The majority of the heat would be created in the compressing of the air as it leaves the exducer tip of the compressor wheel and enters the diffuser. An expansion chamber just following the compressor discharge and preceding the intake manifold could help to dampen the effects of the turbulence, Thus increasing actual air flow and air stream stability. I'm not claiming to be an expert, but there are actual calculations involved in gas expansion. Gonzo 1066, what size plumbing (tubing) do you have exiting your compressor discharge currently? I'll talk with a friend of mine who may be able to provide me with the proper formulas to calculate the maximum diameter and length of the expansion chamber.
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Re: Laminar vs turbulent flow.. January 26, 2016 07:29AM
The turbo crossover pipe is a 4"
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Re: Laminar vs turbulent flow.. January 26, 2016 07:51AM
Wouldn't we call that type of apparatus an intercooler?



Edited 1 time(s). Last edit at 01/27/2016 07:54AM by neilsroom.
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Re: Laminar vs turbulent flow.. January 26, 2016 07:37AM
There is a reason that runner intake style manifold has such a big long tube with smaller runners going to the intake ports on the head.
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Re: Laminar vs turbulent flow.. January 26, 2016 02:39PM
Quote
RockinRam96
There is a reason that runner intake style manifold has such a big long tube with smaller runners going to the intake ports on the head.

I understand that concept of a long runner helping to tame turbulence. I was wondering if anyone has done any true laminar flow testing.
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Re: Laminar vs turbulent flow.. January 26, 2016 07:07PM
What would happen if you came out of the turbo with 4 in pipe for 6 inches then expand it to 5 in with a funnel back down to 4 in going into the intake creating a chamber to let it equalize, the squeeze it back dawn creating velocity into the intake? Their is no science behind this just me asking a stupid question
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Re: Laminar vs turbulent flow.. January 27, 2016 02:31AM
John, in essence, you would be creating an expansion chamber by doing that. What comes into play is the internal cross sectional area. Inside diameter and length of the expansion chamber need to match the amount of air flow (SCFM) produced by the compressor, which as we all know varies with RPM, exhaust temperature and engine load. I realize that there are restrictions created by the back pressure into the cylinders at any given pressure ratio. This is where calculations come into play. As I said earlier, I'm not an expert, but I've seen the calculations done on another application (mainly turbine engines). Neilsroom is correct in the fact that an intercooler or aftercooler would help this expansion to happen, thus helping to decrease the swirling or turbulence created as the compressed air exits the compressor discharge. The dilemma is that some classes can't run either intercoolers or aftercoolers. The expansion of the turbulent gasses in such a device (chamber) would allow some dwell time (milli or micro seconds) for the turbulence to decrease before the compressed air continues its course towards the intake manifold and eventually the cylinders.
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Re: Laminar vs turbulent flow.. January 27, 2016 02:34AM
If you do a search of laminar flow, the most common demonstrations are with water. They use a larger pipe filled with small tubes ( in this case drinking straws) to align the water stream. It is amazing how much more flow there is with aligned water. I know that all fluids (air included) has vortacies in it.
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Re: Laminar vs turbulent flow.. January 27, 2016 07:21AM
I think one thing you need take into consideration is fluids under pressure vs free flowing fluids and fluids vs gasses.

Turbulent and laminar flow has to deal with viscous fluids, we are talking gasses under pressure here.
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Re: Laminar vs turbulent flow.. January 27, 2016 10:46AM
A fluid is a gas or a liquid.

Turbulent and laminar flows are ways to describe the flow of any fluid, regardless of viscosity or operating pressure.
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Re: Laminar vs turbulent flow.. January 27, 2016 04:07AM
So I have been following this since Gonzo posed the question. Would the expansion chamber idea be the same as some of the dozer intakes I have seen with a "log" on top with two runners going down? The pipe coming from the compressor discharge (3") turning towards the front end of the tractor then doing a 180 degree turn back straight in to a 5" pipe that then dual feeds the intake. I see this as letting the air "settle" before entering the engine but it would also lose velocity correct? Which is more important, velocity or calm air? To Gonzo's last point, would it be worthwhile to make something in the intake that is removable that would help straighten the air right out of the turbo or does it matter where it happens? Thinking that this might be something I would like to try on the dyno. Just trying to follow the conversation and maybe learn something.
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Re: Laminar vs turbulent flow.. January 27, 2016 04:35AM
Zachp, I would say you're correct on your assumption of the use of the dozer cross over tube. I'm sure that at some point International engineers probably discovered a problem with the discharge air. The idea of the chamber allows this dwell time I referred to earlier. This as you stated, "letting the air settle" before entering the intake manifold. Once this compressed air expands in the chamber, velocity does decrease, but the existing pressure created by the compressor discharge continues to force the "air charge" towards a point of exit, which is eventually the cylinders. At first, the velocity slows down in the chamber, but the chamber deceases in volume as it goes towards the chamber discharge. At this point the velocity will again increase as it enters the reduced cross sectional area of the smaller system plumbing (tubing). The difference I believe at this point is, that the turbulence would have been at least reduced, if not negated. At this point, if well designed mandrel type bends are used, the air flow should now be in a laminar flow, thereby increasing actual velocity. One thing that a lot of people don't understand about "Fluid Dynamics" is, there is an absolute difference between flow and pressure, but that one can affect the other.
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Re: Laminar vs turbulent flow.. January 27, 2016 10:27AM
Ok to expand and complicate things; in the above scenario, at what point would you insert the water injection? Where the air is more turbulent and will mix with the water better or where the air is straight/settled? I think it best where the air is turbulent thus as close to the turbo as possible before it gets to the chamber and is allowed to settle out. I have a theory of trying to make something like Gonzo stated of "straws" to straighten the air out early coming out of the turbo and letting it slide through mandrel bends into the chamber and then intake. Think this would accomplish anything or hurt more than it would help?
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Re: Laminar vs turbulent flow.. January 27, 2016 01:39PM
The air coming out of the compressor outlet is way closer to laminar flow than the air going in to the compressor intake. You would be surprised at the length of the vortex in front of the compressor intake wheel. I would guess any gain you would experance with an expansion chamber in the intake crossover would be a result of increased volume not better flow. A expansion area/ step/ chamber on the exhust side of the turbo can and will increase flow by breaking down turbulence.
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Re: Laminar vs turbulent flow.. January 27, 2016 02:43PM
This is interesting, I dont know if any of this discussion will have a positive impact on horsepower BUT it is interesting.

[www.youtube.com]
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Re: Laminar vs turbulent flow.. January 27, 2016 07:46PM
On the exhaust side of the turbine, you can do it abruptly. IE a 3" opening with a large flat donut...3" id and 6-8" od exhaust stack. That will take the spin right out of it. I'm not so sure the issue is as critical on the compressor side But could be done the same way, with large pipe and abrupt changes in size.There's probably some of this done already by using heavy wall o'ring adapters welded to the intake plumbing.

Look at some of the world record street cars with turbos. They dump the exhaust as fast and as close as they can to the turbine wheel, and use large pipe for the intake plumbing, especially if the intercooler is in the trunk.
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Re: Laminar vs turbulent flow.. January 30, 2016 02:13AM
[youtu.be]

Interesting video on flow.
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