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How to measure the instantaneous mass flow rate for small, abrasive AlO2 particles?

  1. Feb 16, 2006 #1


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    Hi all,

    I've been asked to search for a way, cost isn't that big of an issue, to measure flow rate in real-time of small, fast, abrasive particles (AlO2). These particles are, on average, 50 microns in diameter, and are shot out of a nozzle, itself just a bit bigger than 50 microns.

    Another requirement is that this detection system be non-invasive, i.e. it does not obstruct the flow itself.

    So far, I've looked into using Cavity Ringdown Spectroscopy (CRDS), but it doesn't seem suitable because the method employed is tracking particles in the air, which are very small and very low speed.

    I've also looked at a multi-pass optical cell, but that's more tailored towards analysis of exhaust gases and the like.

    I'm currently looking at Continuous Opacimeters [pdf], where they shoot light across the direction of the flow, and based on the attenuation, certain characteristics can be shown.

    Any ideas on how to measure the mass flow rate of small AlO2 through a tube/nozzle?
  2. jcsd
  3. Feb 16, 2006 #2


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    Laser doppler anemometry?
  4. Feb 17, 2006 #3


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    I'm currently reading about it, and so far it looks good!

    My concern atm is that it says its been used for gases and liquids ...

    I'll read into whether it can be used for small, particle flow.



    Actually, the ppt presentation they have on that site also says "Velocity of particles
    ", and it looks like tracer particles are needed to measure the velocity.

    How nice: AlO2 are the size of their tracer particles! :D

    I'll update you once I show my supervisor this.
    Last edited: Feb 17, 2006
  5. Feb 18, 2006 #4


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    Good stuff. Yeah, it's for fluid flow, but I was assuming that your particles would be suspended in air anyway. As far as I know, the seeding particles just need to be reflective, I don't think it matters too much what they actually are.

    Let me know how it goes anyway!

    How important is it to measure in real-time? High-speed video might be an easier option if it's viable.
  6. Feb 19, 2006 #5


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    Seems that they've tried LDA in the past, and there were issues in calibrating it and such.

    In addition, my supervisor said that he's more interested in how concentrated the flow is, i.e. amount of particles flowing through a volume in the tube at any one single time.

    He wants this because it seems that the AlO2 comes out in clumps, i.e. many particles come out, then very little, then many, etc.
    However, we want to have a way of quantifying this amount of flow at any one time, hence, the opacimeter since the extinction coefficient is a measure of how much light is extinct => how many particles flow through.

    Here's a picture of the setup:

    Is there any other device, preferably very easy to install and setup, that gives an instantaneous indication of how many particles are going through the tube?
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