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Forced venturi

  1. Oct 22, 2016 #1
    I have a model venturi Ive created useing a air compressor letting the compressed air out of a small nozzle at the end of the air hose attached to the compressor. The nozzle is placed within a pipe causing the release of air directly torward the right of the pipe then to atmosphere leaving very little restriction within the pipe. The left of the pipe is a sealed system which has about 25cfm of air spilling from it into the left of the pipe.ó Simply put, how do i calculate the needed amount of air needed to pass through the nozzle into the pipe to create sufficient suction to pull the 25cfm from the left of the nozzle to the right and leave a less than atmospheric pressure behind the nozzle. (Leave a minor vacuem) The variables i have are: pipe diameter 1.5" available cfm from compressor is available up to 120cfm.
    I may be overcomplicating the obvious, but the goal is to scavenge the 25cfm constantly as effectivly as possible.
  2. jcsd
  3. Oct 26, 2016 #2


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    The design of these units is part science, art and experience; and, in most cases it is more of a trial and error process. I designed a steam water jet pump variation many years ago based upon a similar unit of ta different geometric configuration and did not have clue as to how my unit would perform until we tested it. So it is really in your best interest to buy a unit sized for your requirements from a current manufacturer.

    I don't know if you have already done a web search on this subject; but, I did a quick one today and found the below paper on the "design of air/air eductors" which illustrates all of the design variables and supposedly the equations, but even before you look at it, I warn you that it is essentially indecipherable as a design guide.


    The only basic advice I can give you if you decide to try and design your own unit is that it should be designed so the jet is sized to operate at a pressure and flow rate below that available from its air supply system so that a valve may be installed ahead of the jet to adjust its flow to obtain the best results on your first try and then based upon the test results try to scale that design to match your requirements; but, don't expect to get there with only one design revision.

    PS This is advise from an engineer with 20 years of experience in new product research and development for high performance pressure relief valves and a patent for an automated steam/water eductor pump design.
  4. Oct 26, 2016 #3
    The link was very helpful in getting me calcuable efficiency equation. I should be able to tinker with its variables to find the median range. Im a newb inventor and in route to be testing scavengeing systems for efficiency retrieval on engines with performance increases. Since when was a giant metel plumber pipe good enough for anything besides tiolets and bath tubs? Lol. Thanks!
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