Fluorescent Wet Flow Testing (cylinder head)
04-03-2006, 06:55 PM
#1
Fluorescent Wet Flow Testing (cylinder head) Here is a very interesting article concerning cyinder head wet flow testing. You can find more good articles here under tech talk www.rehermorrison.com
Tech Talk Article 40
"Wet Flow Revelations:
The Monsoon Inside Your Motor"
by Darin Morgan
Page 1
If you expected to find David Reher’s column on this page, I hope you won’t be too disappointed to find my words here instead. I’m in charge of cylinder head development at Reher-Morrison Racing Engines, and David asked me to write about the extraordinary impact of wet flow testing on our R&D program. I’ve given presentations on our wet flow development at the Performance Racing Industry (PRI) trade show and the Advanced Engine Technology Conference. Since most National DRAGSTER readers can’t attend these events, David thought that Technically Speaking would be a good way to spread the news. He also promised that he’d be back on this page in a few weeks.
Every racer is familiar with dry flow testing; it’s become commonplace in every form of motorsports. In wet flow testing, we add a liquid to the airstream to simulate the behavior of atomized fuel in the engine. Many professional engine builders have built there own wet flow benches. They have told me that after hundreds of hours on there benches, they learned nothing. That does not mean that wet flow testing is useless. It simply means there testing procedures where useless. That all changed last summer when Joe Mondello and Lloyd Creek came up with the fabulous idea. Design a wet flow bench that everyone could use, Make it affordable and make it useful. They have accomplished there task in a BIG way! I was the lucky benefactor of one of the third machine they built. Joe Mondello called and asked me to work with there new bench using our current Pro Stock heads. Since then we have learned so many new and wonder full things about wet flow dynamics and continue to learn more every day.
The mechanics of wet flow testing are straightforward: the intake port is pressurized and liquid is introduced into the air stream with an atomizer. A clear plastic cylinder sleeve allows the operator to observe and record the behavior of the fuel droplets in the valve bowl and combustion chamber. The liquid is then separated from the air and captured in a recovery canister.
Watching wet flow in a cylinder is like trying to see individual rain drops in a hurricane. Adding dye to the mixture helps, but only slightly – the dye reveals gross trends, but not the important details. The breakthrough came when Mondello and Creek came up with the idea to add fluorescent dye to the mixture and observe the motion with an ultraviolet light. What had been invisible suddenly became perceptible – and what they saw was a revelation!
The fluorescent dye allowed us to see the behavior of the air/fuel mixture in fine detail. We could watch as a vortex would form, grow, and move around the chamber like a miniature tornado as we adjusted the valve lift. We could spot areas where the vortices joined to form a cyclone of fuel and air. We could see where flow was turbulent, and where it was stagnant. We felt like blind men who had been given the gift of sight.
The first thing that came to light was the myth of fuel wash. Like most racers, I believed that clean areas on the chamber walls and piston dome indicated where fuel had fallen out of suspension and cleaned off the carbon. Wet flow testing revealed the truth: The shiny areas are where there is the least amount of fuel. This lean mixture burns quickly and completely. In fact, the most fuel fallout occurs where there is a dark, sooty burn pattern on the chamber and piston. That is where the fuel falls out of suspension, creating a vortex. In this condition, the fuel burns, but it burns too slowly and too late in the cycle to create usable cylinder pressure.
Usually the burn pattern that we see on the chambers and pistons mimics what we see on the wet flow bench at the upper ranges of valve lift. For example, our Pro Stock engines use a cam with 1-inch valve lift, and the burn signature in the chamber is almost identical to what we observe on the wet flow bench at .800-inch valve lift.
What had appeared to be chaos in the cylinder now became a fluid and predictable motion, thanks to the fluorescent dye and ultraviolet light. We saw how the vortices spin in a clockwise or counterclockwise direction depending on the port orientation and the direction of the airflow. We watched as they started small, gained size and speed, and rotated clockwise or counterclockwise around the chamber.
One of the variables that significantly affects power is spark plug wetting. If there is a vortex of raw fuel droplets near the plug gap, it is very difficult to ignite the mixture. The wet flow bench allowed us to see whether a vortex formed near the plug gap and then take steps to move it away.
We also discovered that there is a strong tendency for vortex generation around the exhaust valve. The fuel converges in a big rotating ball, and its energy is wasted because it burns too late and too slowly to create useful cylinder pressure on the power stroke. In an inefficient engine, this fuel is expelled into the exhaust port while it is still burning, raising the exhaust gas temperature and superheating the valve guides. This isn’t a simple problem to solve, but now we know where to focus our efforts.
Wet-flow technology is already migrating to sportsman engines. The shape, cross-sectional area and velocity characteristics of the ports in our Raptor big-block sportsman cylinder head came directly from our Pro Stock research. There is a small “wing” in the Raptor’s intake runner that takes the wet flow off the floor and literally launches it back into the airstream. The port has to be designed around this wing; you can’t just put a wing in a port and gain power. That’s one example of how we have applied wet flow technology to sportsman engines.
In a perfect world, the air/fuel mixture would be 100 percent homogenous. The atomized fuel droplets would all be the same size and surrounded by an adequate number of oxygen molecules for complete combustion. Unfortunately, we don’t live in a perfect world. Thanks to Joe Mondello and Lloyd Creek the wet flow bench is starting to show us how imperfect the world inside a racing engine really is.
# # #
© Reher-Morrison Racing Engines, 2003
web@rehermorrison.com
Tech Talk Article 40
"Wet Flow Revelations:
The Monsoon Inside Your Motor"
by Darin Morgan
Page 1
If you expected to find David Reher’s column on this page, I hope you won’t be too disappointed to find my words here instead. I’m in charge of cylinder head development at Reher-Morrison Racing Engines, and David asked me to write about the extraordinary impact of wet flow testing on our R&D program. I’ve given presentations on our wet flow development at the Performance Racing Industry (PRI) trade show and the Advanced Engine Technology Conference. Since most National DRAGSTER readers can’t attend these events, David thought that Technically Speaking would be a good way to spread the news. He also promised that he’d be back on this page in a few weeks.
Every racer is familiar with dry flow testing; it’s become commonplace in every form of motorsports. In wet flow testing, we add a liquid to the airstream to simulate the behavior of atomized fuel in the engine. Many professional engine builders have built there own wet flow benches. They have told me that after hundreds of hours on there benches, they learned nothing. That does not mean that wet flow testing is useless. It simply means there testing procedures where useless. That all changed last summer when Joe Mondello and Lloyd Creek came up with the fabulous idea. Design a wet flow bench that everyone could use, Make it affordable and make it useful. They have accomplished there task in a BIG way! I was the lucky benefactor of one of the third machine they built. Joe Mondello called and asked me to work with there new bench using our current Pro Stock heads. Since then we have learned so many new and wonder full things about wet flow dynamics and continue to learn more every day.
The mechanics of wet flow testing are straightforward: the intake port is pressurized and liquid is introduced into the air stream with an atomizer. A clear plastic cylinder sleeve allows the operator to observe and record the behavior of the fuel droplets in the valve bowl and combustion chamber. The liquid is then separated from the air and captured in a recovery canister.
Watching wet flow in a cylinder is like trying to see individual rain drops in a hurricane. Adding dye to the mixture helps, but only slightly – the dye reveals gross trends, but not the important details. The breakthrough came when Mondello and Creek came up with the idea to add fluorescent dye to the mixture and observe the motion with an ultraviolet light. What had been invisible suddenly became perceptible – and what they saw was a revelation!
The fluorescent dye allowed us to see the behavior of the air/fuel mixture in fine detail. We could watch as a vortex would form, grow, and move around the chamber like a miniature tornado as we adjusted the valve lift. We could spot areas where the vortices joined to form a cyclone of fuel and air. We could see where flow was turbulent, and where it was stagnant. We felt like blind men who had been given the gift of sight.
The first thing that came to light was the myth of fuel wash. Like most racers, I believed that clean areas on the chamber walls and piston dome indicated where fuel had fallen out of suspension and cleaned off the carbon. Wet flow testing revealed the truth: The shiny areas are where there is the least amount of fuel. This lean mixture burns quickly and completely. In fact, the most fuel fallout occurs where there is a dark, sooty burn pattern on the chamber and piston. That is where the fuel falls out of suspension, creating a vortex. In this condition, the fuel burns, but it burns too slowly and too late in the cycle to create usable cylinder pressure.
Usually the burn pattern that we see on the chambers and pistons mimics what we see on the wet flow bench at the upper ranges of valve lift. For example, our Pro Stock engines use a cam with 1-inch valve lift, and the burn signature in the chamber is almost identical to what we observe on the wet flow bench at .800-inch valve lift.
What had appeared to be chaos in the cylinder now became a fluid and predictable motion, thanks to the fluorescent dye and ultraviolet light. We saw how the vortices spin in a clockwise or counterclockwise direction depending on the port orientation and the direction of the airflow. We watched as they started small, gained size and speed, and rotated clockwise or counterclockwise around the chamber.
One of the variables that significantly affects power is spark plug wetting. If there is a vortex of raw fuel droplets near the plug gap, it is very difficult to ignite the mixture. The wet flow bench allowed us to see whether a vortex formed near the plug gap and then take steps to move it away.
We also discovered that there is a strong tendency for vortex generation around the exhaust valve. The fuel converges in a big rotating ball, and its energy is wasted because it burns too late and too slowly to create useful cylinder pressure on the power stroke. In an inefficient engine, this fuel is expelled into the exhaust port while it is still burning, raising the exhaust gas temperature and superheating the valve guides. This isn’t a simple problem to solve, but now we know where to focus our efforts.
Wet-flow technology is already migrating to sportsman engines. The shape, cross-sectional area and velocity characteristics of the ports in our Raptor big-block sportsman cylinder head came directly from our Pro Stock research. There is a small “wing” in the Raptor’s intake runner that takes the wet flow off the floor and literally launches it back into the airstream. The port has to be designed around this wing; you can’t just put a wing in a port and gain power. That’s one example of how we have applied wet flow technology to sportsman engines.
In a perfect world, the air/fuel mixture would be 100 percent homogenous. The atomized fuel droplets would all be the same size and surrounded by an adequate number of oxygen molecules for complete combustion. Unfortunately, we don’t live in a perfect world. Thanks to Joe Mondello and Lloyd Creek the wet flow bench is starting to show us how imperfect the world inside a racing engine really is.
# # #
© Reher-Morrison Racing Engines, 2003
web@rehermorrison.com
04-04-2006, 09:13 PM
#3
Excellent read. Seems like an extremely basic idea that you wouldn't think people would just now realize in adding UV-reactive substance to see the entire atomization. Of course, I didn't think of it, just saying it goes to show such a small difference will net us so much more knowledge in determining flow patterns and developing better heads/engines.
04-05-2006, 12:55 AM
#6
Originally Posted by ArcticZ28
Excellent read. Seems like an extremely basic idea that you wouldn't think people would just now realize in adding UV-reactive substance to see the entire atomization. Of course, I didn't think of it, just saying it goes to show such a small difference will net us so much more knowledge in determining flow patterns and developing better heads/engines.
Bret
04-05-2006, 02:13 AM
#7
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Originally Posted by TAF Motorsports
I asked the question in that other thread...
Is wetflow testing relivant for fuel injection?
Is wetflow testing relivant for fuel injection?
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04-05-2006, 03:51 AM
#8
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That's not true at all. Wet-flow testing applies to the fluid dynamics of any passageway, whether that passage normally carries wet flow or not.
The biggest insights one gains from wet-flow analysis is the details of the turbulant flows within a larger stream system. This concept applies to intake manifolds and passageways in general.
For example, a wet flow test might reveal that the vertical support pillars in the center of the LSX plenum perhaps aid flow by redistributing vortices and similar phenomena; or they might just act like big walls. Either way, adequate wetflow testing (using a clear intake and a lot of time for analysis) would show you exactly what is happening.
It would be very useful for comparing computational fluid dynamics models (like those in solidworks for example) for a 3d structure, to what actually goes on in real life in that structure.
The biggest insights one gains from wet-flow analysis is the details of the turbulant flows within a larger stream system. This concept applies to intake manifolds and passageways in general.
For example, a wet flow test might reveal that the vertical support pillars in the center of the LSX plenum perhaps aid flow by redistributing vortices and similar phenomena; or they might just act like big walls. Either way, adequate wetflow testing (using a clear intake and a lot of time for analysis) would show you exactly what is happening.
It would be very useful for comparing computational fluid dynamics models (like those in solidworks for example) for a 3d structure, to what actually goes on in real life in that structure.
04-05-2006, 12:02 PM
#10
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One thing I question is, the article seems to indicate they
are watching vortices develop in real time which means
static flow; I wonder how relevant this is to a chopped-
flow system where the timescale is less than the time to
"spool up" the little tornadoes.
are watching vortices develop in real time which means
static flow; I wonder how relevant this is to a chopped-
flow system where the timescale is less than the time to
"spool up" the little tornadoes.
04-05-2006, 12:07 PM
#11
Originally Posted by 67camaro
yes...the intake port on fuel injected engines still flows fuel since the injector is placed before the port. on the other hand wet flow testing an ls1 intake would be useless.
What about wet flowing it for us guys running a wet nitrous kit that is not direct port?
04-05-2006, 12:41 PM
#12
Originally Posted by jimmyblue
One thing I question is, the article seems to indicate they
are watching vortices develop in real time which means
static flow; I wonder how relevant this is to a chopped-
flow system where the timescale is less than the time to
"spool up" the little tornadoes.
are watching vortices develop in real time which means
static flow; I wonder how relevant this is to a chopped-
flow system where the timescale is less than the time to
"spool up" the little tornadoes.
i was thinking the same thing.
then i got carried away, wondering what teh effects are as the bottom of the cyl (the piston) comes up and down... then started wondering if you could make a clear cyl(block)/piston with a crank and valvetrain, and spin it via electric motor.
spin it real time, then record the whole thing on high speed camera.......
LOL.. really easy to let your mind go free on that idea... nice article.
04-05-2006, 01:15 PM
#14
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Jimmy has a very good point!
I think he is saying that with a running engine the intake pulses from other cylinders would disrupt flow on the cylinder in which the vortices form (on the cylinder you are analyzing)?
In short with a moving motor, there may not be enough time for the vortices to form?
I think he is saying that with a running engine the intake pulses from other cylinders would disrupt flow on the cylinder in which the vortices form (on the cylinder you are analyzing)?
In short with a moving motor, there may not be enough time for the vortices to form?
04-05-2006, 01:29 PM
#15
id be interested to actually see all of this working somewhere... but something else id be interested to see would be the effect on the air/fuel when the valve closed...
would the quick closing valve have a swirl form behind it as it quickly closed? that intake valve moving is a large amount of area for that small combustion chamber... and its quickly moving "up" inside there...
i like learning/thinking about this kind of stuff.. i just wish i had the money/time to pursue it...
would the quick closing valve have a swirl form behind it as it quickly closed? that intake valve moving is a large amount of area for that small combustion chamber... and its quickly moving "up" inside there...
i like learning/thinking about this kind of stuff.. i just wish i had the money/time to pursue it...
04-05-2006, 01:30 PM
#16
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They have some extremely advanced software that simulates all this stuff VERY VERY well.
One of my friends got his paws on it, very expensive stuff. Perks of being a grad student I guess.
One of my friends got his paws on it, very expensive stuff. Perks of being a grad student I guess.
04-05-2006, 06:58 PM
#17
In the article he mentions a ramp in the intake track. Look at the ramp (TALKING ABOUT VORTEC SWIRL) CNC'd into this OEM LS7 head. I have never seen this type of port work on any other custom ported LSx head . Although all factory LSx heads have a ramp cast into the intake port, most head porters remove it.
Last edited by gollum; 04-05-2006 at 08:58 PM.
04-05-2006, 07:25 PM
#18
We (RevXtreme.com) sent our top techs to Reher Morrison engine building school for their certification. Darin is a genius to say the least. The wet flow bench is a mess...we were covered w/florescent liquid when done! But it was amazing no matter what you are wanting to flow. We could see with our piston design where the "hot" spots were on the piston and just how evenly the fuel mixture is distributed. He also has a great video on reversion and fuel injection. Watching an Indy motor rev at insane RPM's and seeing the fuel mixture hover ABOVE the stacks!
The class (highly recomended no matter what your engine & HP building profficiancy) was fascinating (and I have been building, maintaining, & repairing race engines for years...Top Dragster & Super Comp Alky ones). Darin & the crew shared secerets with us that are 1-2 years away from public release (something Warren Johnson would NEVER do), and we came away with far more knowledge than I ever expected.
We worked with (and still are) Darin on the LS1/LS7 performance heads in development & still stay in touch sharing info.
Reher Morrision is one of the most technologically advanced engine building facilities I have ever visited & value their knowledge enough to send each of our senior techs there in the future.
The class (highly recomended no matter what your engine & HP building profficiancy) was fascinating (and I have been building, maintaining, & repairing race engines for years...Top Dragster & Super Comp Alky ones). Darin & the crew shared secerets with us that are 1-2 years away from public release (something Warren Johnson would NEVER do), and we came away with far more knowledge than I ever expected.
We worked with (and still are) Darin on the LS1/LS7 performance heads in development & still stay in touch sharing info.
Reher Morrision is one of the most technologically advanced engine building facilities I have ever visited & value their knowledge enough to send each of our senior techs there in the future.
04-05-2006, 09:24 PM
#20
Originally Posted by 'hoochie2
In regards to Darin Morgan's article - I can say that while he and David Reher were visiting/testing/developing at Dart last Summer, Darin was ALL OVER the wet flow bench. He mentions this in this post: http://speedtalk.com/forum/viewtopic...ht=rehermaskin
And yes this is relevent in FI motors too, as fuel and air still come in contact in the runners to an extent, the bowl and the combustion chamber.
And yes this is relevent in FI motors too, as fuel and air still come in contact in the runners to an extent, the bowl and the combustion chamber.
http://speedtalk.com/forum/viewtopic...ht=rehermaskin
Last edited by gollum; 04-05-2006 at 09:30 PM.