Originally Posted by dcorn;
The way you describe the progressive controller for the turbo is interesting. A turbo spools up and reaches a set psi, then the rpms keep rising as the boost stays the same. Technically the injection system sprays the same amount of water/meth/whatever after that set boost level and at any RPM. Correct?
What about a centrifugal supercharger? I am about to put on a progressive kit like this, but my blower starts building boost at about 3500-4000rpm and reaches 10-11psi by redline. There is no boost plateau so the injection should keep increasing up until I shift. Should I set the controller to peak the injection pressure at a lower rpm than redline or should I set it at my maximum boost so that the power keeps building throughout the rpm range? Lots of stuff to think about, definitely subscribing to this thread. The Centrifugal surcharge obeys the square law - boost is not strictly linear to RPM rise - hence it rarely see much boost at low RPM. If we discussing the WAI flow matching the power curve, it will also need match the fuel demand. For this to work well, we have to take account of the specific fuel consumption of the set up. More fuel is needed to supply the added load imposed by the supercharger - If you base the WIA flow relative to boost and and not fuel flow, you need to make some adjustment on your fuel map to compensate the non-linearity between the two flows - fuel=3D and PPS=2D. It will not going be a simple "bolt-on and go" affair - but pretty close. |
Each different type of medium that you flow through a specific type of conduit will record a different reading at the measured point. Viscosity of the medium and frictional factors of the specific material of the conduit will contribute to the variance in your collected data. Gasses, obviously, will not give you the same values as liquids, but for the test you propose, air would give a relative recordable value.
First of all it is not theory, the information I passed along is based on engineering constants. As to your question, yes if the pressure was equal on both sides of the check valve the spring would not open. But, that is not the case in an injection system. You have a constant pressure on the upstream side of the valve and when that meets or exceeds the spring value, naturally the valve opens. The difference is that you have an open orifice (the spray nozzle) that is very much open. Because of this, the pressure passes through the valve to the nozzle and into your device (or I/C pipe in our case). Petro/Chemical plants all over the world use similar set-ups for chemical injection in cooling towers, lube oil systems etc. The more critical the system the more sophisticated the pressure control device becomes.
Originally Posted by Richard L
(Post 4709050)
Thanks for chiming in, I share your input. It is a difficult one to explain.
The easiest way to determine if there is pressure drop or after the checkvalve is setting up a test rig - a video to record the test and post it here. I have all the equipment at our works and If enough people want this done, I am more than happy to set it up. Before we go further, do you think the the following set up is acceptable? I can only do this with air as I can generate accurate and stable air pressure much easier than water. Pressure source => gauge => checkvalve=> gauge => variable restrictor (jet replacement) Back to your theory, if the pressure is the same between the two chambers (before CV and after CV) the CV should close? |
Originally Posted by cpoevo
(Post 4709067)
^You will see a pressure drop across the valve. You will not see a 20psi drop across the valve, there will be a pressure drop across the valve just a very small amount. You also have to consider flow through the valve not just the pressure.
I am be able to explain why you think this is the case. If you have any open ended checkvalve, you will not see any pressure at all. Mass flow generates pressure = keeps the valve open - agreed 100%. But if you have a restriction downstream (water jet), the flow will no longer able to keep the valve open, 20psi differential remains true. |
No, because you have a constant upstream psi value.
Originally Posted by Richard L
(Post 4709175)
If the pressure drop is small than 20psi, the valve should close by definition?
I am be able to explain why you think this is the case. If you have any open ended checkvalve, you will not see any pressure at all. Mass flow generates pressure = keeps the valve open - agreed 100%. But if you have a restriction downstream (water jet), the flow will no longer able to keep the valve open, 20psi differential remains true. |
Originally Posted by Richard L
(Post 4709175)
If the pressure drop is small than 20psi, the valve should close by definition?
I am be able to explain why you think this is the case. If you have any open ended checkvalve, you will not see any pressure at all. Mass flow generates pressure = keeps the valve open - agreed 100%. But if you have a restriction downstream (water jet), the flow will no longer able to keep the valve open, 20psi differential remains true. Every bend, valve, fitting, or anything else installed in the line will create pressure loss. The size of the hose or pipe will also effect the pressure of the pump. The loss usually will not be noticeable on a gauge though. I understand basic fluid theory and know how to apply it, I just suck at explaining it. |
isnt this easy to prove if the checkvalve is a source of restriction...
constant pressure source - 125psig A - pressure source/pump -> nozzle B - pressure source/pump -> checkvalve -> nozzle the difference in volume output of injectant will indicate if the CV is a source of restriction A - B = 0, no restriction A - B >0, there is restriction from checkvalve or is this too simplified? |
This is getting to become a good discussion. I think I'd better set up the simple test and than we can discuss the result.
It looks pretty 50/50 for the time being. I will do it with air first and if time permit, I set up with water with a 22psi checkvalve. |
Originally Posted by Whoosh
(Post 4709044)
What do you base your opinion on? My information is based on 37 years in the engineering business. I size piping systems, valves and pumps on a regular basis. I would refer you to Crane Flow of Fluids Through Valves, Fittings and Pipe manual so that you may see the error of your decision. As I stated earlier, there will be a pressure drop, but depending on the orifice size of the valve it can be less than 1# and as high as 3-4#.
I find most all of what Richard has written to be very informative and accurate, but on this one case, he is quite wrong. I've only been in the chemical industry (chemical engineer) for 20 yrs, graduated in 87, so you have me on experience. Yes, I have a Crane manual right behind me, in my book case, haven't cracked it open for probably 10 yrs or so. Haven't needed to. :beer: If you need an engineering type example..... say you have a boiler that makes 150# steam, and you let down 150# steam across a pressure regulator (pretty darn close to the ball/spring design Richard showed) to control another header at 50#, you're saying that regulator is only going to take a 1-4# drop? Last time I checked, that's 100#'s. The cross sectional area for flow will change based on flow demands, but the pressure drop across the regulator remains constant at 100#'s. |
Originally Posted by SlowCar;
isnt this easy to prove if the checkvalve is a source of restriction...
constant pressure source - 125psig A - pressure source/pump -> nozzle B - pressure source/pump -> checkvalve -> nozzle the difference in volume output of injectant will indicate if the CV is a source of restriction A - B = 0, no restriction A - B >0, there is restriction from checkvalve or is this too simplified? Your test is simple and will get result. Didn't you once set something up similar a months or twos ago with a digital weighing machine. For I could remember, the test with two checkvalves flows less than one with one checkvalve. It will be interesting to do the same with no checkvalve at all and plot the three - three points are very useful. Do you still have the link? |
Originally Posted by dubbleugly01;
why is it that everyone has to throw their pedigree around when a different opinion is posted? {thumbup}
I've only been in the chemical industry (chemical engineer) for 20 yrs, graduated in 87, so you have me on experience. Yes, I have a Crane manual right behind me, in my book case, haven't cracked it open for probably 10 yrs or so. Haven't needed to. :beer: If you need an engineering type example..... say you have a boiler that makes 150# steam, and you let down 150# steam across a pressure regulator (pretty darn close to the ball/spring design Richard showed) to control another header at 50#, you're saying that regulator is only going to take a 1-4# drop? Last time I checked, that's 100#'s. The cross sectional area for flow will change based on flow demands, but the pressure drop across the regulator remains constant at 100#'s. If A(CV) - B(no CV)=0 than I will correct the text and apologise. {thumbup} |
Originally Posted by Richard L
(Post 4709544)
It is difficult to set this up with pump with pulses, even with damper etc. The checkvalve react with peak pressure rather average pressure. I normally test prototype with air than water. I will get myself with a pressure vessel so I can get pressurise water with little or no ripple.
Your test is simple and will get result. Didn't you once set something up similar a months or twos ago with a digital weighing machine. For I could remember, the test with two checkvalves flows less than one with one checkvalve. It will be interesting to do the same with no checkvalve at all and plot the three - three points are very useful. Do you still have the link? i'll redo the 3 experiment today after work: A - pump -> nozzle B - pump -> checkvalve -> nozzle C - pump -> checkvalve<->checkvalve -> nozzle Pump = pulsing on-demand shurflo Time for injectant collection = 60secs Checkvalve = swagelok 25psig crack :beer: |
Originally Posted by SlowCar
(Post 4709595)
i think the hosting site erased those files because they were huge.
i'll redo the 3 experiment today after work: A - pump -> nozzle B - pump -> checkvalve -> nozzle C - pump -> checkvalve<->checkvalve -> nozzle Pump = pulsing on-demand shurflo Time for injectant collection = 60secs Checkvalve = swagelok 25psig crack :beer: |
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In no way did I intend to belittle you or to throw around my "pedigree". If you are in engineering then you know that you must substantiate any statement or finding. The flaw in your thinking comes from trying to equate a regulator with a spring check. The regulator sole purpose, as you stated, is to reduce downstream pressure and hold it at a constant. A spring check serves two functions a) as a backflow preventer and b) to limit low pressure pulses from traveling downstream. Once opened (or cracked) the upstream pressure can rise to any set value and the resultant downstream pressure will be equal to that pressure minus the sum of pressure drop across the valve and line losses.
Richard, because I'm anal by nature and wanted to get a second opinion on your testing methods, I asked our Sr. Process Engineer what would be the most accurate testing device and set-up. Here is what we concluded: Air as your medium would be acceptable (not totally accurate, but acceptable). You will need a regulated air source. (compressor w/ regulator). All connected piping should be hard piped for repeatability (any bends or kinks will change your readings). Install one (1) pressure gauge upstream of the check. Install a centrally located check valve with a known spring pressure. Hard pipe to a spray nozzle installed in a larger diameter sealed tube (say 2-3 ft. long). Install a pressure gauge in the end of the sealed tube. To test, merely turn on your air source with a regulated starting pressure below the spring pressure. Open the regulator up untill you read 30# on the gauge in the sealed tube. At that point, read the pressure on the gauge in the upstream gauge. Subtract the downstream gauge from the one upstream and this will give you your pressure drop for the total system.
Originally Posted by dubbleugly01
(Post 4709526)
why is it that everyone has to throw their pedigree around when a different opinion is posted? {thumbup}
I've only been in the chemical industry (chemical engineer) for 20 yrs, graduated in 87, so you have me on experience. Yes, I have a Crane manual right behind me, in my book case, haven't cracked it open for probably 10 yrs or so. Haven't needed to. :beer: If you need an engineering type example..... say you have a boiler that makes 150# steam, and you let down 150# steam across a pressure regulator (pretty darn close to the ball/spring design Richard showed) to control another header at 50#, you're saying that regulator is only going to take a 1-4# drop? Last time I checked, that's 100#'s. The cross sectional area for flow will change based on flow demands, but the pressure drop across the regulator remains constant at 100#'s. |
Originally Posted by Whoosh
(Post 4709656)
A spring check serves two functions a) as a backflow preventer and b) to limit low pressure pulses from traveling downstream. Once opened (or cracked) the upstream pressure can rise to any set value and the resultant downstream pressure will be equal to that pressure minus the sum of pressure drop across the valve and line losses.
No worries about belittling me, I love a good debate. I've been wrong before, I'm sure I'll be wrong some time soon again. Just not this time {thumbup} |
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