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Flow-blurring atomization is an innovative twin-fluid atomization approach that has demonstrated superior effectiveness in producing fine sprays compared to traditional airblast atomization methods. In flow-blurring atomizers, the high-speed gas flow is directed perpendicular to the liquid jet. Under specific geometric and physical conditions, the gas penetrates back into the liquid nozzle, resulting in a highly unsteady bubbly two-phase mixing zone. Despite the remarkable atomization performance of flow-blurring atomizers, the underlying dynamics of the two-phase flows and breakup mechanisms within the liquid nozzle remain poorly understood, primarily due to the challenges in experimental measurements of flow details. In this study, detailed interface-resolved numerical simulations are conducted to investigate the two-phase flows generated by a planar flow-blurring atomizer. By varying key dimensionless parameters, including the dynamic-pressure ratio, density ratio, and Weber number, over wide ranges, we aim to comprehensively characterize their effects on the two-phaseflow regimes and breakup dynamics.
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Low temperature reaction kinetics inside an extended Laval nozzle: REMPI characterization and detection by broadband rotational spectroscopy
Chirped-Pulse Fourier-Transform millimeter wave (CP-FTmmW) spectroscopy is a powerful method that enables detection of quantum state specific reactants and products in mixtures. We have successfully coupled this technique with a pulsed uniform Laval flow system to study photodissociation and reactions at low temperature, which we refer to as CPUF (“Chirped-Pulse/Uniform flow”). Detection by CPUF requires monitoring the free induction decay (FID) of the rotational coherence. However, the high collision frequency in high-density uniform supersonic flows can interfere with the FID and attenuate the signal. One way to overcome this is to sample the flow, but this can cause interference from shocks in the sampling region. This led us to develop an extended Laval nozzle that creates a uniform flow within the nozzle itself, after which the gas undergoes a shock-free secondary expansion to cold, low pressure conditions ideal for CP-FTmmW detection. Impact pressure measurements, commonly used to characterize Laval flows, cannot be used to monitor the flow within the nozzle. Therefore, we implemented a REMPI (resonance-enhanced multiphoton ionization) detection scheme that allows the interrogation of the conditions of the flow directly inside the extended nozzle, confirming the fluid dynamics simulations of the flow environment. We describe the development of the new 20 K extended flow, along with its characterization using REMPI and computational fluid dynamics. Finally, we demonstrate its application to the first low temperature measurement of the reaction kinetics of HCO with O2 and obtain a rate coefficient at 20 K of 6.66 ± 0.47 × 10−11 cm3 molec−1 s−1.
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- Award ID(s):
- 2247776
- PAR ID:
- 10515759
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 159
- Issue:
- 21
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0178533
