Supercritical CO2 generator using bubble collapse by water hammer

• We developed a new apparatus to dynamically generate a supercritical CO2 bubble.
• The CO2 bubble was generated in a water-filled tube using water hammer.
• Maximum internal pressure of CO2 bubble reached 12.7 MPa and we obtained supercritical CO2 for 60 μs.
• Experimental internal pressure profiles agreed with numerical simulations.
• We perform parametric study of increase of external pressure to optimize the duration of scCO2.

We have developed a new apparatus to dynamically generate supercritical CO2 (scCO2) bubbles in water using a water hammer facility by efficiently concentrating water energy. We measured the internal and external pressures of a CO2 bubble covered with a rubber membrane using pressure transducers, and observed the bubble's oscillations by a high-speed video camera. We evaluated the maximum duration of the scCO2 for conditions 60 μs in experiments. We performed numerical simulations using the Rayleigh–Plesset equation by substituting the experimental external pressure profiles of the bubble and confirmed that numerical results agreed with the experimental internal pressure. Moreover, in the minimum external pressure condition where we experimentally achieved the condition of scCO2 in the bubble for 16 μs by water hammer, we obtained the maximum duration of scCO2 conditions up to 55 μs by numerical simulations assuming isotropic compression.

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