ACTIVE CONTROL OF A GAS FLOW RATE IN AN ALTERNATING GRADIENT DIFFUSION CHAMBER USING LABVIEW by Max...
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ACTIVE CONTROL OF A GAS FLOW RATE IN AN ALTERNATING GRADIENT DIFFUSION CHAMBER USING LABVIEW by Max Trueblood & David LeBlanc ME240 Semester Project MS&T, Rolla, MO 65401 7 MAY 2010 FN: 10507 507—1200 ME240 Project YES.pptx 1
ACTIVE CONTROL OF A GAS FLOW RATE IN AN ALTERNATING GRADIENT DIFFUSION CHAMBER USING LABVIEW by Max Trueblood & David LeBlanc ME240 Semester Project MS&T,
ACTIVE CONTROL OF A GAS FLOW RATE IN AN ALTERNATING GRADIENT
DIFFUSION CHAMBER USING LABVIEW by Max Trueblood & David
LeBlanc ME240 Semester Project MS&T, Rolla, MO 65401 7 MAY 2010
FN: 10507 5071200 ME240 Project YES.pptx 1
Slide 2
OBJECTIVE: To actively control the outflow in the Alternating
Gradient Diffusion Cloud Chamber (ALGR) based on the pressure drop
across the sample metering tube inlet, so as to achieve stable
operation, and thus improve data collection. 2
Slide 3
Figure 1. Green lines take dilution air to probe, while red
lines take sample to instrumented trailer. Two one ton ingots of Pb
hold probe securely. 3 3
Slide 4
Figure 2. Easing up into the contrail of the target plane to
sample its particulates. 4
Slide 5
Figure 3. Sampling from a drones gas turbine engine at an
engine rebuilding facility. Goal here was to try to burn up all C
particles in extremely hot afterburner at right. 5
Slide 6
Figure 4. Dr Whitefield inspects engine at a hush house in
Amsterdam. 6 Dr Phil Whitefield
Slide 7
7 Figure 5. Typical size distribution from jet engine. Conc
(p/cc*nm) Particle Diameter, Xp (nm)
Slide 8
Figure 6. The condensation nucleus counter, CNC. The butanol
vapor condenses onto each small particle forming a droplet which is
~ 1000 X larger than the original particle. The optics are then
able to detect the individual droplets, allowing calculation of the
particle concentration. 8 Soaked with 1-Butanol Laser DETECTOR
Slide 9
Since EFF(Xp) = Ccnc(Xp) / Ctru(Xp) The true concentration at
diameter Xp is: Ctru(Xp) = [Ccnc(Xp) / EFF(Xp)] 9
Slide 10
10 Figure 7. Typical EFF vs. Xp for a CNC.
Slide 11
Figure 8. Overall schematic of the test setup. Ctru(Xp)
Cvnv(Xp) 11 EFF(Xp) = Ccnc(Xp) / Calgr(Xp)
Slide 12
Figure 9. Schematic of the differential mobility analyzer
(DMA). 12
Slide 13
Figure 10. Boltzmann charge distribution. 13
Slide 14
Figure 11. Alternating Gradient cloud chamber. Imperfect pumps
will cause a variation of P that disturbs the dPsmt. Hold dPsmt
very constant. Difficult! 14 Three pumps: AP1 Laser Ptle Counter
loop AP2 Filtered air at top AP3 Excess air at bottom Eight flows:
Q1 Excess at bottom Q2 Filtered at top Q3 LPC loop out Q4 LPC loop
Q5 AP2 make up Q6 LPC loop in Q9 LPC annular in Qsmt sample
metering tube Q1 Q9 ~ 1 to 4 L/m Qsmt ~ 0.010 L/m Qsmt = 3.55 *
dPsmt 5.42 dPsmt ~ 1 inch H2O MFC1 MFC2
Slide 15
Figure 12. The condensation nucleus counter, CNC. The butanol
vapor condenses onto each small particle forming a droplet which is
~ 1000 X larger than the original particle. The optics are then
able to detect the individual droplets, allowing calculation of the
particle concentration. 15 Soaked with 1-Butanol Laser
DETECTOR
Slide 16
Figure 13. Schematic of LPC. 16
Slide 17
Figure 14. Overall schematic of the test setup. Ctru(Xp)
Cvnv(Xp) 17 EFF(Xp) = Ccnc(Xp) / Calgr(Xp)
Slide 18
18 Figure 15. The DMA.
Slide 19
19 Figure 16. The CNC. This slide intentionally left blank.
Originally it showed a commercial CNC. You can get on the web and
find them. Look for Condensation Particle Counter or Condensation
Nucleus Counter
Slide 20
20 Figure 17. The top of the ALGR.
Slide 21
21 Figure 18. The switch box that allows choosing what controls
the MFCs.
Slide 22
Figure 19. The LPC setting at the bottom of the ALGR.
Slide 23
Figure 20. Alternating Gradient cloud chamber. Imperfect pumps
will cause a variation of P that disturbs the dPsmt. Hold dPsmt
very constant. Difficult.! 23 Three pumps: AP1 Laser Ptle Counter
loop AP2 Filtered air at top AP3 Excess air at bottom Eight flows:
Q1 Excess at bottom Q2 Filtered at top Q3 LPC loop out Q4 LPC loop
Q5 AP2 make up Q6 LPC loop in Q9 LPC annular in Qsmt sample
metering tube Q1 Q9 ~ 1 to 4 L/m Qsmt ~ 0.010 L/m Qsmt = 3.55 *
dPsmt 5.42 dPsmt ~ 1 inch H2O MFC1 MFC2
Slide 24
Figure 21. 24
Slide 25
Figure 22. Front panel of LV progm, no feedback control.
25
Slide 26
Figure 23. Block diagram of program with no feedback control.
26
Slide 27
27 The previous method allows one to control Q1 (bottom
outflow) a. Manually with the pot b. From labview program, but
still manually. I would really like to keep dPsmt constant. Thus a
feedback loop that controls Q1 based on comparing the actual dPsmt
to a set point value is what I really desire.
Slide 28
Figure 24. LV progm w feedback. 28
Slide 29
Figure 25. LV program w feedback. Notice the formula node.
29
Slide 30
Figure 26. Sample data, no feedback control. 30
Slide 31
Figure 27. Q1 and dPsmt, no feedback control. Q1 was
momentarily changed. 31
Slide 32
Figure 28. Computer controlled momentary change in Q1 and its
effect on dPsmt, no feedback. 32
Slide 33
Figure 29. Momentary change in Q2 and its effect on dPsmt, no
feed back. 33
Slide 34
Figure 30. Response for computer control with feed back loop in
program. Here there were 3 separate changes in the desired
dPsmt-sp. The effect on Q1 is shown. Note how the measured dPsmt
does go to a new value and then remains constant. Good!
Slide 35
CONCLUSIONS 1. The output or signal of the MFCs has been
successfully monitored by the labview program. 2. The MFCs have
been successfully controlled a. manually with potentiometers. b.
manually by the labview program. c. in an automated fashion with a
closed loop feed back with the LV progm. 35
Slide 36
36 FURTHER WORK: 1. Have the LV program actually read the LPC,
the dPsmt, etc, and calculate the C (p/cc) as given by the ALGR. 2.
Have the LV program read the CNC and log the Ccnc. 3. Have the LV
program compute the EFF = [Ccnc / Calgr ]. 4. MFC3 does not seem to
provide a signal that I can monitor. Broken? I can control it,
though, as proven by observing the rotameter in series with it. 5.
Make use of all the logged data to find the sweet spot of operation
of the ALGR where one gets reliable data. At this sweet spot, the
Calgr would remain constant even though some of the flows wandered
off their set points a small amount.
Slide 37
Acknowledgements: Thanks are due to Mr Mitch Cottrell and Mr
Steven Achterberg for helpful suggestions. 37