Design of de Laval nozzles for gas-phase molecular studies in uniform supersonic flow

Durif, Olivier

doi:10.1063/5.0060362

Cited by 14 publications

(2 citation statements)

References 69 publications

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“…Although a few groups have focused on improving the airstream channel of the meltblown die, doing so would likely improve the meltblown airstream field and thereby lead to an ultrafine meltblown fiber. The Laval nozzle is a type of shrink-expansion nozzle invented by Gustav Patrik de Laval for steam engine applications and is now used in numerous situations. , Laval nozzles accelerate low-velocity airstreams to produce a high-velocity airstream and can even accelerate airstream from subsonic to supersonic speeds. Tan et al installed Laval nozzles under the traditional meltblown die and studied the characteristics of the meltblown airstream field with and without Laval nozzles.…”

Section: Introductionmentioning

confidence: 99%

Influence of a Meltblown Die with a Laval Airstream Channel on the Manufacturing Process of a Polymer Fiber Based on an Orthogonal Test and Simulation Analysis

Guo,

Zhu

2023

ACS Omega

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A Laval nozzle is a device that accelerates a low-speed airstream to form a high-speed airstream. In this work, we use a Laval nozzle in the airstream channel design of a meltblown die to improve the tensile properties of the fiber in the airstream field of the meltblown die. The features of the airstream field of the meltblown die are analyzed by numerical simulation. For a given parametrization, six factors may be tuned to optimize the performance of the Laval airstream channel of the meltblown die. We thus use a five-level, six-factor orthogonal test method to optimize the airstream channel of the meltblown die to determine the various factors that influence the airstream field beneath the meltblown die. The results show that the optimized Laval meltblown die performs better than the traditional die and that the widths of the larynx and expansion segment most strongly affect the airstream velocity beneath the Laval meltblown die. Compared with a traditional die, the Laval die optimized by orthogonal testing increases the peak airstream velocity by 17.54%, average velocity by 96.81%, average temperature by 12.32%, and peak pressure by 14.61% and produces weaker turbulence intensity near the spinneret. These characteristics make the airstream beneath the die more stable and uniform and accelerate the attenuation of the fiber diameter, producing more polymer nanofibers. These results demonstrate a valuable approach to the design and optimization of meltblown dies and provide a technical reference for the production and application of the meltblown fiber production equipment.

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Section: Introductionmentioning

confidence: 99%

Influence of a Meltblown Die with a Laval Airstream Channel on the Manufacturing Process of a Polymer Fiber Based on an Orthogonal Test and Simulation Analysis

Guo,

Zhu

2023

ACS Omega

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“…Accurate design of the profile of the Laval nozzle is essential in creating a flow with the desired expansion. The methods used in calculating the nozzle profile involves two main steps [16][17][18][19][20][21] . The first involves calculating the shape responsible for the isentropic core using the "method of characteristics" while the second involves calculating the boundary layer accounting for the viscosity of the gas flow.…”

Section: Simultaneous Kinetics and Ringdown (Skar)mentioning

confidence: 99%

UF-CRDS: a pulsed uniform supersonic flow apparatus coupled with continuous-wave cavity ringdown spectroscopy

Thawoos¹

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Investigating low temperature reaction kinetics of elementary reactions is key to understanding many phenomena of astrochemical importance. Since the introduction of CRESU (A French acronym that stands for reactions kinetics in uniform supersonic flow) method it has been widely used to study many reactions at temperatures as low as 13 K. The uniform supersonic flow provides a continuous flow with unform temperature and density which act as a wall-less configuration avoiding condensations effects along the walls when cooling down to low temperatures. The uniform flow is achieved by a Laval nozzle (a convergent-divergent nozzle). Traditionally, laser induced fluorescence (LIF) is used to probe reactants in the flow. In this thesis I describe a new instrument in which highly sensitive continuous wave-cavity ringdown spectroscopy (cw-CRDS) is coupled with a pulsed uniform flow for the first time, a "uniform flow cavity ringdown spectrometer," UF-CRDS. The UF-CRDS setup is equipped with a pulsed uniform flow system which is produced by means of a high throughput piezoelectric stack valve combined with a Laval nozzle. In addition to the Laval nozzles built in collaboration with Dr. I.R. Sims from University of Renne, 3D printed Laval nozzles designed using a Matlab program developed in-house are also used. These nozzles are validated experimentally as well as theoretically using a computational fluid dynamics program, OpenFOAM. Cavity ringdown spectroscopy is an absorption technique which measures the rate of decay of trapped light with an optical cavity made by two high reflectivity mirrors. As this method measures the rate of decay of light instead of light intensity, it is largely immune the intensity fluctuations of the light source. The UF-CRDS apparatus is equipped with a DFB diode laser or an ECDL laser that can be tuned between 1411-1419 nm and 1280-1380 nm respectively. The CRDS system consists of two planoconcave high reflectivity mirrors ([greater than] 99.99 percent) at these wavelengths. These are separated by 800 mm and with them we could achieve a maximum ringdown decay time constant of about 160 [mu]s. For time-independent absorbing samples, the enhanced rate of power loss compared to the empty cavity leads to faster exponential decays. When the concentration of the absorbing species changes on the time scale of the empty cavity ring-down time, non-exponential decays result, for which the instantaneous decay rate in excess of the empty cavity reference case provides a time-resolved measure of the sample absorbance. S. Brown et al. recently introduced a method, simultaneous kinetics and ringdown (SKaR), where a single background normalized ringdown is applied to follow the rate of the reaction. We successfully combined the unform flow with the SKaR technique for the first time. We choose vibrationally excited CN formed by photolysis of cyanogen bromide (BrCN) using an excimer laser operated at 248 nm (70 mJ/pulse) as our primary radical species of interest. This molecule has relatively strong transitions in the frequency range of the DFB laser and is a highly reactive radical so it makes an excellent candidate to demonstrate the capabilities of the instrument. We have performed detailed examination of the rate of reaction of vibrationally excited CN(v=1) with O2, NO and butadiene isomers at temperatures 70 K and 24 K. The reaction of CN(v=1) + O2 proceeds via association of the reactants to form a [NCOO] complex which then mainly follows through a lowest energy pathway leading to elimination of an O atom instead of re-dissociation or reaction to NO + CO. On the other hand, for the reaction of CN(v=1) + NO mainly follows through a pathway which leads to dissociation of the complex [NCNO], where it leads to vibrational relaxation of CN through a barrierless pathway. We have measured the rates for these reactions at both 24 and 70 K temperatures and they are in line with the experimental and theoretical calculations found in literature. Another reaction of interest is the reaction of CN(v=1) with butadiene isomers. Both experimental and theoretical evidence suggests the isomers 1,2 and 1,3-butadiene enters through a barrierless PES to form long lived C5H6N complexes. We have measured the rate of reaction for both reactions and we see a substantial difference in their reaction rate. The rate of reaction for the 1,3-butadiene is in excellent agreement with the reported rates for the reaction with (v=0), suggesting no evidence of vibrational enhancement. The related reaction of CN with 1,2-butadiene at low temperatures has not been studied, to our knowledge.

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Space-marching inverse design of subsonic, transonic, and supersonic internal flowfields

ZHANG,

YI,

ZHAO

et al. 2024

Chinese Journal of Aeronautics

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Design of de Laval nozzles for gas-phase molecular studies in uniform supersonic flow

Cited by 14 publications

References 69 publications

Influence of a Meltblown Die with a Laval Airstream Channel on the Manufacturing Process of a Polymer Fiber Based on an Orthogonal Test and Simulation Analysis

Influence of a Meltblown Die with a Laval Airstream Channel on the Manufacturing Process of a Polymer Fiber Based on an Orthogonal Test and Simulation Analysis

UF-CRDS: a pulsed uniform supersonic flow apparatus coupled with continuous-wave cavity ringdown spectroscopy

Space-marching inverse design of subsonic, transonic, and supersonic internal flowfields

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