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 MAY 2010 FN: —1200 ME240 Project YES.pptx 1

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

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

Figure 2. Easing up into the contrail of the target plane to sample its particulates. 4

Figure 3. Sampling from a drone’s 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

Figure 4. Dr Whitefield inspects engine at a hush house in Amsterdam. 6 Dr Phil Whitefield

7 Figure 5. Typical size distribution from jet engine. Conc (p/cc*nm) Particle Diameter, Xp (nm)

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

Since EFF(Xp) = Ccnc(Xp) / Ctru(Xp) The true concentration at diameter Xp is: Ctru(Xp) = [Ccnc(Xp) / EFF(Xp)] 9

10 Figure 7. Typical EFF vs. Xp for a CNC.

Figure 8. Overall schematic of the test setup. Ctru(Xp) Cvnv(Xp) 11 EFF(Xp) = Ccnc(Xp) / Calgr(Xp)

Figure 9. Schematic of the differential mobility analyzer (DMA). 12

Figure 10. Boltzmann charge distribution. 13

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 ~ L/m Qsmt = 3.55 * dPsmt – 5.42 dPsmt ~ 1 inch H2O MFC1 MFC2

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

Figure 13. Schematic of LPC. 16

Figure 14. Overall schematic of the test setup. Ctru(Xp) Cvnv(Xp) 17 EFF(Xp) = Ccnc(Xp) / Calgr(Xp)

18 Figure 15. The DMA.

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

20 Figure 17. The top of the ALGR.

21 Figure 18. The switch box that allows choosing what controls the MFCs.

Figure 19. The LPC setting at the bottom of the ALGR.

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 ~ L/m Qsmt = 3.55 * dPsmt – 5.42 dPsmt ~ 1 inch H2O MFC1 MFC2

Figure

Figure 22. Front panel of LV progm, no feedback control. 25

Figure 23. Block diagram of program with no feedback control. 26

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.

Figure 24. LV progm w feedback. 28

Figure 25. LV program w feedback. Notice the formula node. 29

Figure 26. Sample data, no feedback control. 30

Figure 27. Q1 and dPsmt, no feedback control. Q1 was momentarily changed. 31

Figure 28. Computer controlled momentary change in Q1 and its effect on dPsmt, no feedback. 32

Figure 29. Momentary change in Q2 and its effect on dPsmt, no feed back. 33

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!

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

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.

Acknowledgements: Thanks are due to Mr Mitch Cottrell and Mr Steven Achterberg for helpful suggestions. 37

QUESTIONS? 38

39