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An Investigation of Diffraction, Reinitiation and Amplification Behaviors in Detonations of Varying Fuel-Oxidizer Mixtures

Millard, Benjamin
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518276531766

Abstract Details

2022, MS, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
This study seeks to further explore a detonation amplification that is caused by detonation diffraction and reinitiation event as a detonation passes through an area expansion. A study of changes in detonation amplification behavior was conducted using varying back pressure, equivalence ratios, and fuel oxidizer mixture to change the cell size and subsequent incoming detonation criticality. Detonation criticality being defined as the actual number of detonation cells divided by the critical number of cells also is theorized to influence relationship between area expansion and amplification behavior. A new pneumatic system was developed to allow the detonation reaction mixture to be controlled. This detonation was then passed into an area expansion chamber where the amplification process was observed using ion probes to measure wave speed and pressure probes to measure pressure impulse after which the detonation is exhausted out of the chamber. Three amplification behaviors are observed, spike amplification, steady amplification, and end wall amplification. The steady amplification behavior occurs in detonations close to criticality or in smaller area expansion. The steady amplification behavior lacks the significant pressure spike at reinitiation with this reinitiation happening near the inlet of the chamber, reaching a pressure amplification of 2 to 3 times the steady-state impulse. Spike amplification occurred at lower detonation critically or in larger area expansion and is characterized by a reinitiation spike in impulse pressure to a peak amplification of between 3.5 to 5 times the incoming steady-state impulse with this typically occurring further in the chamber. This spike is followed by rapid attenuation of the pressure impulse to a lower amplified state with a slower attenuation observed during steady amplification. The third behavior of end wall amplification was observed to not recouple until near the end wall, this results in the peak amplified state being at the outlet of the chamber. This was amplified further than either of the other two behavior and was characterized by a dramatic recoupling at the end wall. This behavior was generally observed in detonations that are both very subcritical and when expanding into a larger area expansion. The trend observed when changing criticality is that some threshold crossed in which a detonation will first display steady amplification at low cell size, then spike amplification behavior when the criticality is decreased, and then finally end wall amplification once the cell size passes a final threshold. The effect of cell size appears to be compounded by the change in area ratio with detonations being observed to transition between detonation behavior when changing the area ratio without changing the incoming detonation criticality. This study was however limited in its ability to directly measure detonation criticality and instead draws conclusions based on cell size data from previous studies. Lastly, an optical study showed that two different reinitiation behaviors observed in the spike amplification range with one of the reinitiation behaviors matching that found in a previous study, with a third behavior capture that is believed to show the reinitiation mechanism at the end wall amplification behavior.
Daniel Cuppoletti, Ph.D. (Committee Member)
Timothy Ombrello, Ph.D. (Committee Member)
Jongguen Lee, Ph.D. (Committee Member)
140 p.
Aerospace Materials

Recommended Citations

Citations

  • Millard, B. (2022). An Investigation of Diffraction, Reinitiation and Amplification Behaviors in Detonations of Varying Fuel-Oxidizer Mixtures [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518276531766

    APA Style (7th edition)

  • Millard, Benjamin. An Investigation of Diffraction, Reinitiation and Amplification Behaviors in Detonations of Varying Fuel-Oxidizer Mixtures. 2022. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518276531766.

    MLA Style (8th edition)

  • Millard, Benjamin. "An Investigation of Diffraction, Reinitiation and Amplification Behaviors in Detonations of Varying Fuel-Oxidizer Mixtures." Master's thesis, University of Cincinnati, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518276531766

    Chicago Manual of Style (17th edition)

ucin1659518276531766
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This open access ETD is published by University of Cincinnati and OhioLINK.