Increasing Jet Velocity Research Articles

Prediction of interface morphology formed by the oblique gas jet impinging on a liquid surface

This study presents a theoretical analysis of the oblique gas jet impingement process on a liquid surface, elucidating the evolution of the flow field distribution and the influence of jet parameters on cavity shape dynamics. By integrating surface tension effects, the existing Blanks and Chandrasekhara model was refined to develop an advanced predictive model for cavity morphology. The theoretical framework was substantiated through numerical simulations and corroborated with experimental measurements of cavity dimensions, captured using state-of-the-art machine vision technology. The findings reveal a consistent trend in cavity dimension variations: an increase in the cavity surface width with the elevation of the impinging angle from the vertical and an escalation in gas jet velocity. Conversely, a reduction in the impinging angle coupled with an increase in jet velocity leads to a deeper cavity. To enhance the predictive accuracy, the model underwent iterative optimization, incorporating experimental data and accounting for jet parameters. The refined model demonstrated achieved a maximum error of 0.135 mm and a minimum error of 0.03 mm, providing reliable forecasts of cavity depth, which is pivotal for applications in fluid dynamics and related engineering fields.

Liquid breakup and droplets behavior of free triple-impinging jets with different impinging distance

The breakup characteristics and droplet behavior of free triple-impinging jets (FTIJs) were investigated using a high-speed camera. The liquid sheet and droplets breakup mechanism, liquid sheet breakup length, width, droplet diameter and velocity, were studied under different jet velocity and horizontal impinging distance and perpendicular impinging distance. The results revealed that with increasing jet velocity from 1.42 m/s to 6.61 m/s, different breakup modes were observed: closed-rim mode, open-rim mode, rimless mode, and wave or ligament mode. At low jet velocities, increasing impinging distance delayed the development of breakup mode. Based on experimental observations, the sheet breakup mechanism is categorized into two main regimes with four subregimes. Droplet breakup occurs in two stages: growth and necking, however, at high jet velocities complete breakup was achieved. Increasing jet velocity led to an increase in liquid sheet breakup length, width, and droplet velocity but a decrease in droplet diameter. Conversely, increasing impinging distance resulted in a decrease in liquid sheet breakup width and droplet radial velocity but an increase in droplet diameter. The effect of perpendicular impinging distance on axial velocity and breakup length was found to be more significant than that of horizontal impinging distance due to the effect of perpendicular nozzle. The findings indicate that the perpendicular jet greatly enhances atomization. This study provides a theoretical basis for designing and optimizing FTIJs.

Analysis of Surface Drag Reduction Characteristics of Non-Smooth Jet Coupled Structures

To enhance the service life of shipping equipment and minimize surface wear, this study employs biomimetic principles, integrating fitted structures with jet dynamics to model three configurations: non-smooth structures, single jet structures, and non-smooth jet-coupled structures. We utilized the SST k-ω turbulence model for numerical simulations to investigate the drag reduction characteristics of these structural models. By varying the jet angle and speed, we analyzed the changes in viscous resistance, pressure differential resistance, and drag reduction rates at the wall surface. Furthermore, the mechanisms of compressive stress, velocity fields, vortex structures, and shear stress on drag-reducing surfaces were elucidated, revealing how these factors contribute to drag reduction in non-smooth jet-coupled structures. The results indicate that the non-smooth jet-coupled structure exhibits superior drag reduction performance at a main flow field velocity of 20 m/s. As the jet velocity increases, the viscous drag on the surface of the non-smooth jet-coupled structure decreases, while the pressure differential drag increases. Conversely, variations in the jet angle have a minimal effect on viscous drag but lead to a reduction in pressure differential drag. Specifically, when the jet velocity is set at 1 m/s, and the jet angle is 60°, the drag reduction achieved by the non-smooth jet-coupled structure peaks at 7.48%. Additionally, the non-smooth jet-coupled structure features a larger area characterized by low shear stress, along with an increased boundary layer thickness at the bottom; this configuration effectively reduces surface velocity and consequent viscous drag.

Decay characteristics and application predictions of far-field high-pressure water: Jet velocity and volume fraction

In the field of deep mining engineering, high-pressure water jets progress toward larger diameters and higher velocities to enhance their impact performance. Understanding the decay characteristics as well as their implications remains challenging. In this article, the jet spread coefficients (k and c) within the empirical model of jet diffusion are determined by series of lab experiments, while simulations using the Eulerian method are conducted by implementing the modified diffusion model as a subroutine. The effects of spread coefficient, jet velocity, and nozzle diameter on the degree of jet decay are studied. The results show that the jet spread coefficient increases logarithmically with increasing jet velocity. With the increase in nozzle diameter, the growth of spread coefficient k of the jet gradually decreases. Increasing the nozzle diameter and spread coefficient k can effectively reduce the decay degree of jet axial velocity and water volume fraction. Notably, although the increase in jet velocity does not impact the decay of axial velocity, it exacerbates the decay of water volume fraction. Similarly, the increase in spread coefficient c has no effect on the reduction of water volume fraction, but it intensifies the decay of jet axial velocity. The combined effects of increased jet velocity and jet spread coefficient weaken the degree of jet decay. The research presents a comprehensive and innovative study of jet diffusion and attenuation phenomena. These insights not only expand the application of jet diffusion models but also provide theoretical support for understanding and optimizing the application of jets.

A comparative study on the premixed ammonia/hydrogen/air combustion with spark ignition and turbulent jet ignition

Turbulent jet ignition (TJI) is an advanced ignition mode that can enhance ignition and combustion performance, and it is a potential ignition strategy for ammonia/hydrogen internal combustion engines. This study aims to investigate the ignition and combustion characteristics of lean ammonia/hydrogen/air ignited by TJI, and the different ignition modes were compared. The results indicate that active TJI with auxiliary hydrogen injection in the pre-chamber improves the ignition and combustion performance of ammonia/hydrogen/air, and the appropriate shift of the pre-chamber equivalence ratio towards the rich side is considered optimal. As the ammonia fraction increases, the ignition mechanism in the main chamber changes from flame ignition to jet ignition. The advantage of TJI is mainly shown in high ammonia fraction mixtures, which is reflected in significantly lower ignition delay and combustion duration. In addition, TJI reduces the sensitivity of combustion to ammonia fraction compared to SI, due to the high ignition energy, initial flame area and turbulence provided by the hot jet. In TJI mode, the increase in jet velocity seems to be detrimental to the radial development of flames near the orifice, which may result in an increase in the duration of the final stage of combustion.

Experimental and numerical study on the formation and detachment of bubbles at orifices under the impinging jet flow

Three detachment patterns, i.e. single bubble pattern, double bubble pattern, atomizing pattern, are observed as the jet velocity increases. The bubble formation and detachment model are established, and the intensification mechanisms of the impinging jet on the bubble formation and detachment is revealed: Instantaneous flow field fluctuations changes the direction of the pressure difference force, forcing the bubble to detach and shortening the bubble growth time. The fluctuations of the flow field cause the total force on the bubble in the radial direction to be non-zero and the displacement of the bubble in the radial direction appears, which reduces the axial drag and the resistance of bubble to leave the orifice. In summary, under the effect of the impinging jet, the growth time of the bubble is shortened and the detachment size is reduced, which provides the possibility of producing small bubbles through large-diameter holes.

Experimental and model investigation of spreading characteristics of the liquid sheet formed by jet impinging on a circular plane

The focus of this paper is on the spreading characteristics of the liquid sheet formed by jet impinging on a circular plane. The liquid sheet is studied in two parts: the liquid film that spreads radially on the circular plane, and the free liquid sheet after leaving the circular plane, the former determines the initial thickness and velocity of the latter. Experimental results show that, for the liquid film on the circular plane part, as the jet velocity increases, the liquid film thickness increases due to the film velocity loss caused by the inelastic collision. The liquid film thickness is positively correlated with the jet radius and negatively correlated with the circular plane radius. Liquid viscosity slows the spreading of liquid film, forms the boundary layer, and thickens the liquid film. The surface tension inhibits the velocity loss due to the inelastic collision. For the free liquid sheet part, surface tension and gravity promote the bending of the liquid sheet. The larger the initial momentum of the liquid sheet leaving the circular plane, the larger the maximum spreading range of free liquid sheet reaching the equator. As for the theoretical model, a film velocity correction coefficient reflecting collision loss is introduced to improve the radial spreading theory of the liquid film on a solid surface, and a streamline function is assumed to solve the momentum integral equation of free liquid sheet. The predicted streamline agrees well with the experimental data.

Modelling the dynamics of microbubble undergoing stable and inertial cavitation: Delineating the effects of ultrasound and microbubble parameters on sonothrombolysis

Sonothrombolysis induces clot breakdown using ultrasound waves to excite microbubbles. Despite the great potential, selecting optimal ultrasound (frequency and pressure) and microbubble (radius) parameters remains a challenge. To address this, a computational model was developed to investigate the bubble behaviour during sonothrombolysis. The blood and clot were assumed to be non-Newtonian and porous, respectively. The effects of ultrasound and microbubble parameters on flow-induced shear stress on the clot surface during stable and inertial cavitation were investigated. It was found that microbubble translation towards the clot and the shear stress on the clot surface during stable cavitation were significant when the bubble was about to undergo inertial cavitation. While insonation of large microbubble (radius of 1.65μm) at low frequency (0.50 MHz) produced the highest shear stress during stable cavitation, selection of these parameters is not as intuitive for inertial cavitation due to the strong competing effect between jet velocity and translational distance. An increase in jet velocity is always accompanied by a decrease in the translational distance and vice versa. Therefore, a right balance between the jet velocity and the translational distance is critical to maximise the shear stress on the clot surface. A jet velocity of 303 m/s and a distance travelled of 5.12μm at an initial bubble-clot separation of 10μm produced the greatest clot surface shear stress. This is achievable by insonating a 0.55μm microbubble using 0.50 MHz and 600 kPa ultrasound.

Prediction of the Individual Aortic Stenosis Progression Rate and its Association With Clinical Outcomes

BackgroundThe progression rate of aortic stenosis differs between patients, complicating clinical follow-up and management. ObjectivesThis study aimed to identify predictors associated with the progression rate of aortic stenosis. MethodsIn this retrospective longitudinal single-center cohort study, all patients with moderate aortic stenosis who presented between December 2011 and December 2022 and had echocardiograms available were included. The individual aortic stenosis progression rate was calculated based on aortic valve area (AVA) from at least 2 echocardiograms performed at least 6 months apart. Baseline factors associated with the progression rate of AVA were determined using linear mixed-effects models, and the association of progression rate with clinical outcomes was evaluated using Cox regression. ResultsThe study included 540 patients (median age 69 years and 38% female) with 2,937 echocardiograms (median 5 per patient). Patients had a linear progression with a median AVA decrease of 0.09 cm2/y and a median peak jet velocity increase of 0.17 m/s/y. Rapid progression was independently associated with all-cause mortality (HR: 1.77, 95% CI: 1.26-2.48) and aortic valve replacement (HR: 3.44, 95% CI: 2.55-4.64). Older age, greater left ventricular mass index, atrial fibrillation, and chronic kidney disease were associated with a faster decline of AVA. ConclusionsAVA decreases linearly in individual patients, and faster progression is independently associated with higher mortality. Routine clinical and echocardiographic variables accurately predict the individual progression rate and may aid clinicians in determining the optimal follow-up interval for patients with aortic stenosis.

Numerical study on transport and deposition characteristics of particles associated with heat setting process in opposed jet flow field

The transport and deposition of particles accompanying the heat setting process in the opposed jet air supply system have a significant impact on the equipment safety. This paper used the Realizable k–ε model to simulate the flow field distribution of the impinging jet and the Lagrange method to track the trajectory of particles, by considering factors, such as jet velocity (7–13 m/s), oven temperature (413–473 K), and particle size (1–30 μ m ) changes, the instantaneous force process of particles was analyzed and their deposition mechanism was revealed. The numerical results have been well validated, with the root mean square error of within 10%. The results indicate that the flow field form of the opposed jet significantly affects particle placement on the surface of the air duct, the maximum turbulent vortex structure appears at the inlet of the air duct on both sides of the protruding nozzle, enhancing the capture of particles. Under the influence of gravity, the lower surface of the air duct becomes the main deposition surface, this phenomenon becomes more pronounced as the particle size increases and the maximum deposition rate difference between the upper and lower layers is 37%. The number of particles deposited on the rear end of the air duct is greater than that on the front end, and the deposition rate decreases with the increase in jet velocity. In the initial stage, a temperature gradient appeared in the machine room, which provided upward lift for the particles, resulting in more small diameter particles ( d p < 10 μ m ) depositing on the upper surface of the air duct. The results can provide theoretical support for the fire prevention and pollutant purification of equipment, such as heat setting machines.

Numerical investigation of the instability of dry granular bed induced by water leakage

AbstractUnderground pipe defects or cracks under transport infrastructure can cause water leakage to upper soil layers (e.g. subgrade and capping), inducing local cavities or even failure of overlying road/railway formation. Although numerous studies on the instability of granular beds induced by injected water have been conducted, most of them focused on the behaviour of saturated granular beds, while research on dry granular beds is still limited. This paper aims to address this gap using a numerical model coupling volume of fluid method with discrete element method. We observed that dry granular beds go through three distinct regimes as water jet velocity increases including stationary, stable deformation with heave and fluidisation. However, the flow velocities required to deform and fluidise dry granular beds are significantly higher than those required for saturated beds. Increasing granular bed thickness can alter its failure mechanism from full depth to localised erosion, leading to cavity formation around pipe cracks prior to the bed fluidisation. The gravitational and frictional components of granular mass are identified as two main resisting forces of dry granular beds against water jet force, evidenced by the increase of critical jet velocities as particle density and friction coefficient increase. Nevertheless, the moblised zone of granular mass is practically independent of both the buried depth of dry granular beds.

On the concrete breakage by pulsed water jet impact: Fracture characteristic, stress and damage evolution laws

To reveal the dynamic response characteristic and damage-fracture evolution laws of concrete under pulse water jet impact, the numerical simulations on pulse water jets impinging concrete for different operating parameters were established based on SPH-FEM coupling algorithm and verified in this paper. The concrete-breaking effects of pulse water jet and continuous water jet were compared, and the effects of key jet parameters and concrete strength on the damage-fracture characteristics of concrete were investigated. And the damage and stress evolution laws inner concrete were revealed. The results show that there is a better concrete-breaking effect for pulse water jet by repeatedly utilizing the extremely high water-hammer pressure and effectively weakening the water-cushion effect, compared with continuous water jet. The broken pit area and the total length of main cracks decrease with the increase of pulse length, and there is an optimal pulse spacing for pulse water jet to improve the concrete-breaking effect. The broken pit area and the total length of main cracks both linearly increase with the increasing jet velocity and exponentially increase with the increasing jet diameter. As the concrete strength increases, the broken pit area shows an S-shaped curve decreasing trend and the total length of main cracks exponentially decreases. The broken pit width first rapidly increases and tends to stabilize with the increase of jet velocity and concrete strength, and changes linearly with jet diameter and is less affected by pulse length and spacing. The farther away from the jet impact center, the longer the damage cumulative period of concrete due to the jet impact energy attenuation. In horizontal direction, concrete breakage range is approximately 4–5 times of jet diameter; in vertical direction, the previous pulses will cause concrete to be destroyed or damaged, and the subsequent pulses will make the damaged concrete suffer greater stress, causing more serve damage. And the induced stress peak decreases in form of Power function with the increasing distance. The research results could provide theoretical guidance for the parameters selection of pulse water jet efficiently breaking concrete.

Numerical simulation of jet impact process with different jet velocities in a negative pressure ambient

The effect of jet velocity on jet impingement process was of great importance. However, the process of jet impingement and fragmentation is highly complex and involves various physical and thermal phenomena. Therefore, our current work primarily focuses on using computational fluid dynamics (CFD) method to investigate the effect of jet velocity on the characteristics of jet impingement in a negative pressure ambient. The Realizable k-ε model is employed to simulate the turbulent flow process, and an improved Mixture model is used to describe the distribution behavior of the gas-liquid phases. The characteristics of flow field, pressure distribution, velocity distribution, turbulence kinetic energy distribution and vortex behavior were analyzed under different jet velocities at a negative pressure of 31.6 kPa. The results indicate that as the jet velocity increases, the core of jet impingement pressure also increases. The above situation resulted in fragment effect enhancement and an increased number of atomized droplets. These findings provide a theoretical basis for further research on the jet impingement-negative pressure deamination reactor (JI-NPDR).

Targeted Radiation Exposure Induces Accelerated Aortic Valve Remodeling in ApoE-/- Mice.

Thoracic radiation therapy may result in accelerated atherosclerosis and in late aortic valve stenosis (AS). In this study, we assessed the feasibility of inducing radiation-induced AS using a targeted aortic valve irradiation (10 or 20 Grays) in two groups of C57Bl6/J (WT) and ApoE-/- mice compared to a control (no irradiation). Peak aortic jet velocity was evaluated by echocardiography to characterize AS. T2*-weighted magnetic resonance imaging after injection of MPIO-αVCAM-1 was used to examine aortic inflammation resulting from irradiation. A T2* signal void on valve leaflets and aortic sinus was considered positive. Valve remodeling and mineralization were assessed using von Kossa staining. Finally, the impact of radiation on cell viability and cycle from aortic human valvular interstitial cells (hVICs) was also assessed. The targeted aortic valve irradiation in ApoE-/- mice resulted in an AS characterized by an increase in peak aortic jet velocity associated with valve leaflet and aortic sinus remodeling, including mineralization process, at the 3-month follow-up. There was a linear correlation between histological findings and peak aortic jet velocity (r = 0.57, p < 0.01). In addition, irradiation was associated with aortic root inflammation, evidenced by molecular MR imaging (p < 0.01). No significant effect of radiation exposure was detected on WT animals. Radiation exposure did not affect hVICs viability and cell cycle. We conclude that targeted radiation exposure of the aortic valve in mice results in ApoE-/-, but not in WT, mice in an aortic valve remodeling mimicking the human lesions. This preclinical model could be a useful tool for future assessment of therapeutic interventions.

Effect of Relative Jet Temperature in Supersonic Dual-Impinging Jets

Short takeoff and vertical landing aircraft configurations involve multiple jets that impinge onto the deck surface in tandem and lead to several adverse effects. This study reports on the experimental characterization of supersonic dual-impinging jets by systematically varying their relative jet temperature. A sonic converging and Mach 1.5 converging–diverging (CD) nozzles are employed. The expansion ratio of the converging nozzle is maintained at 0.96, 1.19, and 1.59, and the CD nozzle is operated at a fixed nozzle pressure ratio of 3. The temperature ratio of the jet from the CD nozzle is varied from 1.0, 1.3, and 1.7. For a fixed momentum of the jet pair, an increase in jet temperature intensified the nearfield noise and unsteadiness on the impingement surface. At short impingement heights, resonance in the heated jet was the primary source of unsteadiness. At a fixed impingement height, an increase in jet temperature led to a systematic increase in tonal frequency, while jet instability mode shapes were retained. Furthermore, the mean flowfield of sonic jet and fountain regions remain unaffected, and an increase in supersonic jet velocity is observed. This is also accompanied by an increase in unsteadiness in the fountain upwash.

Excitation of Acoustic Modes by Tone Harmonics of a Hole in a Jet-Driven Helmholtz Oscillator

Periodic pressure fluctuations were studied experimentally in the model of a jet-driven Helmholtz oscillator with a cylindrical chamber with a round air jet impinging on the sharp edge of the outlet. The evolution of the amplitude–frequency spectrum of the hole tone from its appearance at a jet velocity of about 2 m/s to excitation of the first acoustic resonance mode at the Helmholtz frequency was studied. The hole tone was a family of harmonics that progressively became more complex as the length and velocity of the jet increased. The successive occurrence of a family of acoustic modes on the harmonics of the jet tone with a further increase in jet velocity is studied. Modes at the Helmholtz frequency arose alternately on the harmonics of the hole tone in the gain band of the oscillator, starting from the highest harmonic. The first mode occurred at the highest harmonic; the second mode, at the previous harmonic; and so on. The final mode arose at the fundamental harmonic of the hole tone and had the maximum amplitude. With a further increase in the Reynolds number, periodic pressure fluctuations became disordered turbulent fluctuations. With a sufficient chamber size and jet velocity, azimuthal and half-wave resonances appeared at the highest harmonic of the hole tone. The largest Reynolds number at which resonance at the Helmholtz frequency was observed was 105.

Numerical analysis of nonlinear interaction between a gas bubble and free surface in a viscous compressible liquid

Liquid viscosity has a potential effect on bubble dynamics. This paper is concerned with bubble dynamics in a compressible viscous liquid near the free surface. The liquid–gas flow is modeled using the Eulerian finite element method coupled with the volume of fluid method. The numerical results have been shown to be in excellent agreement with those from the spherical bubble theory and experiment. Parametric studies are carried out regarding the Reynolds number Re and the stand-off parameter γd. It clearly demonstrated that the liquid viscosity inhibits bubble pulsation, jet flow, free surface jet, and bubble splitting. Quantitatively, as Reynolds number Re decreases, the maximum bubble volume, jet tip velocity, free surface spike, and crown height decrease, and the toroidal bubble splitting weakens. As the stand-off parameter γd increases, the maximum bubble volume, jet velocity, and bubble average pressure peak increase while the height of the free surface spike decreases. Close observation reveals that the free surface crown tends to disappear at small Re or large γd, further indicating the complex mechanism behind the crown spike evolution.

An experimental study of the characteristics of blended hydrogen-methane non-premixed jet flames

The addition of hydrogen to natural gas promotes the reactivity of fuel and thus increases the jet fire risk from pipeline leakage during the transport process of blended hydrogen-natural gas. Aiming to evaluating the potential jet fire risk, this paper experimentally studied the characteristics of H2/CH4 jet flames at varied heat release rates (HRRs) with H2 volume fraction (fv) ranging from 0% to 90% by two circular nozzles (diameters: 3 and 5 mm). The results show that with the increase of H2 volume fraction, two competing effects on flame height were observed, that is, the increase in mixture molecular diffusivity, radicals pool, and air entrainment decreases the flame height, while the increase in flame temperature and jet velocity of fuel flow with a small flow Reynold number increases the flame height. Comparisons of different previous correlations of flame height with current experiments were conducted to obtain the applicable flame height model for H2/CH4 flames. The ratio of flame width to flame height for two nozzle diameters increases with dimensionless HRR when HRR is small, and then becomes nearly constant (∼ 0.145). The flame width normalized by nozzle diameter has a power dependence on dimensionless HRR, i.e., 0.48 and 0.59 power for the 3 and 5 mm nozzle, respectively. Further theoretical analysis suggested the dimensionless correlations of lift-off height of H2/CH4 flames with fv ≤ 50%.

Study of the thickness of the liquid film formed by a round water jet impinging on a curved cylindrical wall

An experimental setup has been established to investigate the thickness profiles of the liquid film formed by an oblique round water jet impinging on curved walls. The influence of the jet velocity, jet angle, and radius of curvature of the curved wall on the thickness profile of the liquid film has been investigated. Both on the flat and curved walls, as the jet velocity increases, the mode of the liquid film transitions from laminar to turbulent, and the thickness of the liquid film decreases first and then increases along the flow direction. The transition velocity range for the curved walls with the radius of curvature R = 30 mm is 19.1–25.08 m/s (Re = 10 946–14 373). Both on the flat and curved walls, the thicknesses of the liquid film increase in the downstream part of the liquid film while decreasing in the upstream part, as the jet angle increases. The laminar and turbulent thickness prediction models of liquid film on flat walls were extended to curved walls by replacing the distance away from a stagnation point with the radius of curvature. Predictions obtained by the present models agree well with measurements. Errors of the film thickness between the predictions and measurements along the centerline are mainly less than 20%, and the correlation coefficients (σc) are mainly located in 0.85–0.99.

Numerical Simulation on the Smoke Prevention Performance of Air Curtains in an Island-Type Subway Station

Subway fires are a major threat to the safe and smooth operation of subway stations. In this paper, an island-type subway station was taken as an example to conduct a series of numerical simulations using Fire Dynamics Simulator (FDS). The temperature, visibility, and CO concentration in the subway station were analysed under different thicknesses and jet velocities of the air curtains. The smoke-prevention performance of the air curtains in the subway station was investigated. As the thickness and jet velocity increase, the flame tilts significantly, which greatly hinders the spread of smoke toward the stairs. The smoke temperature and CO concentration on the left side of the air curtains gradually decrease, while the visibility increases significantly. For a 3 MW fire scenario, to satisfy the evaluation criteria, the results show that the thickness of the air curtains needs to be at least 0.3 m, and the jet velocity needs to be at least 2 m/s. The sealing effectiveness (Esealing) tends to increase and then remains constant with increasing momentum, and the maximum is obtained when the momentum of the air curtains (Ia) is 12.5 kg·m/s2. Meanwhile, it is found that an energy-saving efficiency of 85.2% can be achieved by replacing positive pressure ventilation with air curtains. The results of this work can provide a significant reference for the design of smoke protection in subway stations.