Supersonic Nozzle Research Articles

Quantitative Definition of Spray Edge With Extinction Diagnostics and Evaluation of Attenuation Coefficient for Liquid Jets in Supersonic Crossflow

Abstract A quantifiable, reproducible, and repeatable definition of the three-dimensional spray width and depth for a canonical jet in an open-source supersonic crossflow is presented. An expanding Mach 2 dry-air crossflow is generated through a converging-diverging nozzle with a 25.4 mm by 230 mm wide throat area. A one-millimeter injector with ethanol seeding provides the liquid injection. Injector characteristics and losses are quantified through a calibrated cavitating venturi. Momentum flux ratios ranged from 0.1 to 20, and Reynolds number scaled by the injector diameter ranged from 5000 to 40,000. A shadowgraph setup with a telecentric lens provides uniform magnification for precise and repeatable measurements from injection to 150 mm downstream of the jet. A Phantom v2012 camera with a frame rate of 20 kHz and shutter time of 285 ns was employed. Light transmittance is defined and calculated for each image pixel with a ratio method paired with no-spray images collected immediately before injection. These values are then related to an attenuation coefficient by incorporating spray width profiles collected with cross-sectional Mie-scatter imaging at multiple axial locations with a burst mode laser.

The Effect of Internal Combustion Engine Nozzle Needle Profile on Fuel Atomization Quality

This article presents the results of research on the impact of changing the cross-section of an atomizer’s flow channel, which is caused by changing the flow geometry of the passive part of the needle on the drop diameter distribution of the fuel spray. A three-hole type H1LMK, 148/1 atomizer with hole diameters, dN, equal to 0.34 mm, is analyzed. A nozzle with a standard (i.e., unmodified) needle and three nozzles using needles with a modified profile in the flow part of the needle, marked by the code signatures 1L, 2L, and 3L, are tested. An increasing level of fuel turbulence characterizes the needles during the flow along their flow part due to the use of one (1L), two (2L), and three (3L) de Laval toroidal nozzles, respectively, obtained by mechanically shaping the outer surface of the flow part of the spray needle. The spray produced is tested using the Malvern Spraytec STP 500 device cooperating with the dedicated Malvern version 4.0. During the tests, measurements and an analysis of the spray droplet size distribution over the entire injection duration, equal to 7 ± 2 ms, are made for each nozzle. The experiment makes it possible to determine the effect of the nozzle needles’ profiles on the time distribution of the actual droplet diameters; the time distribution of the Sauter mean droplet diameters, D[3,2]; the percentile shares of the droplet diameters Dv (10), Dv (50), and Dv (90); the distribution span during the development of the spray stream; and the time distribution of the shares of the droplets with diameters belonging to selected diameter classes D[x1−x2] in the spray. The results of the measurements of the drop diameter distribution indicate that using atomizers with a modification to the flow channel allows for an increase in the share of droplets with smaller diameters compared to the standard atomizer.

Numerical study on thermal hydraulics characteristics during steam submerged jet condensation from rectangular CD nozzle

The phenomenon of steam-water direct contact condensation (DCC) has significant importance in nuclear industry due to its rapid and efficient heat and mass transfer rates. In this numerical study, three dimensional simulations of steam submerged jet condensation from rectangular converging-diverging (CD) nozzle into subcooled water has been investigated. The steam condensation phenomenon has been captured from thermal phase change model as user defined function (UDF) in ANSYS Fluent software. The computational results were validated using experimental results as well as previously published numerical study. The effects of steam pressure and water temperature on distributions of various thermal hydraulics parameters including velocity, pressure, temperature, heat and mass transfer characteristics have been studied. The steam pressure and water temperature have been kept in the range of 200–500 kPa and 20–60 °C, respectively. The maximum value of jet velocity and heat transfer coefficient have been found as 803 m/s and 2.73 MW/m2K respectively. The peak velocity value increases with steam pressure. After maximum expansion point, the velocity profile curve is shifted downstream with steam pressure. The axial pressure distribution first decreases and then increases from expansion-compression waves. The axial temperature profile followed the similar trend as observed for axial steam pressure distribution. At constant steam pressure, the maximum rate of heat transfer coefficient decreases with the increase in water temperature. The maximum mass transfer rate under prescribed flow conditions has been found as 2789.8 kg/m3s. The peak mass transfer rate decreases with steam pressure and water temperature. The peak rates for heat and mass transfer have been observed in the nearby vicinity of nozzle exit location.

Численное исследование полидисперсных двухфазных течений в осесимметричном сопле Лаваля с учетом силы Магнуса, действующей на вращающиеся капли

The available papers on two-phase flows in de Laval nozzles are focused on the effect of various initial conditions, models of coagulation, fragmentation, and rotation of droplets on their local and integral characteristics. Some papers note that due to the difference in the velocities of the gas and droplets along the nozzle axis, the Magnus force acts on the rotating droplets perpendicular to the specified difference and deflects the trajectories of the droplets toward the nozzle wall. In an earlier paper, the authors proposed a mathematical model of a two-phase flow in an axisymmetric de Laval nozzle that accounts for the Magnus force on the basis of the kinetic equation. The present article is devoted to a numerical study of a polydisperse two-phase flow in a de Laval nozzle with account for the coagulation, fragmentation, and rotation of droplets and the Magnus force. This study is based on the “monodisperse” model of fragments developed by I.M. Vasenin and A.A. Shreiber, the method of labeled drops (the Lagrange method), and the finite-difference schemes of second order accuracy. The calculations are carried out for a test nozzle configuration with condensate formation on the nozzle wall both with and without the Magnus force accounted. The calculated results show that the Magnus force has different impacts on the trajectories of droplets of various sizes. It should be noted that the limiting trajectories of the droplets approach the nozzle wall due to the Magnus force, resulting in the earlier dropout on the wall. Therefore, when designing the divergent section of the nozzle, it is necessary to consider the revealed approach of the location of the dropout, which is associated with the Magnus force, to the nozzle throat.

Improving environmental efficiency of gas purification by low-temperature treatment

This paper discusses low-temperature gas purification to improve environmental efficiency. Modern methods of gas cooling are also considered. A mathematical model is proposed for changing the parameters of an ideal gas when flowing through an opening - a Laval nozzle. A graph of the temperature of the gas at the outlet of the Laval nozzle is plotted at a different pressure ratio at the inlet and outlet of the nozzle. The conclusion was made based on the obtained values.

Impact of static pressure and Mach number velocity on flow characteristics within a convergent-divergent nozzle.

Impact of static pressure and Mach number velocity on flow characteristics within a convergent-divergent nozzle.

CFD simulation of flyash fluidized-bed pulverization with superheated steam

The supersonic pulverization technology uses superheated steam generated by the boiler to generate supersonic airflow through the Laval nozzle, and accelerates the flyash fed into the crushing chamber by the screw feeder, and then the flyash can be crushed in mutual collision and friction process. The present paper conducted CFD simulation of fluidized-bed pulverization with superheated steam, and both the velocity filed and the particle tracks are obtained. Convergence test was performed firstly to verify the numerical results, and three different meshes and several different numbers of particles are employed here to show the average velocity of the particles through a certain horizontal plane. The effect of some key parameters, such as distance between the two opposite nozzles and feeding locations of the flyash to the velocity filed and the particle velocity are also numerically investigated. Results show that, the best distance between the two opposite nozzles of the four-nozzle case is 142 mm and the average particle velocity distribution varies little with the flyash feeding position for the present jet mill model.

Experimental study of a butanol film motion with a co-current gas flow inside a supersonic nozzle

The results of experimental study of the local characteristics of a butanol near-wall film interacting with a co-current air flow in a supersonic nozzle with a geometric Mach number M = 3.75 are presented. The thickness and velocity of the butanol film front as well as waves on its surface in different cross-sections of the nozzle were measured. The role of the boiling process on the film flow inside the nozzle is studied and its effect on the measured film thickness is shown.

Experimental study on boundary layer of internal flow visible supersonic nozzle

The high-frequency pulsation noise generated by the turbulent boundary layer on the wall of a Laval nozzle can significantly affect the quality of the flow field at the nozzle outlet. In this study, a supersonic wind tunnel with visible internal flow is designed and fabricated to observe the development and evolution of the boundary layer on the contraction and expansion surfaces of a Laval nozzle, as well as to study the flow field inside the supersonic nozzle. The subsonic, transonic and supersonic profiles of the nozzle are designed by bicubic curve, Hall method and classical characteristic line method respectively. The results of numerical calculation and total pressure measurement show that the flow field at the nozzle outlet of the wind tunnel is uniform and stable, and the deviation of Mach-number-root mean square is better than the qualified level of China's national military standard. Nanoparticle-tracer based planar laser scattering (NPLS) technology is used to carry out the flow display test of the internal flow visual supersonic nozzle, and the fine structure image of the whole flow field in the nozzle is obtained. The image clearly shows the development and evolution of the boundary layer in the nozzle. The interface between boundary layer and main stream and the wall curve of nozzle transition region are extracted by image processing technology. The fractal dimension of the extracted boundary layer contour is calculated, thereby establishing the corresponding relationship between the fractal dimension and the boundary layer state, and determining the transition position of the boundary layer. The results show that the transition position of the nozzle profile is closer to downstream than that of the nozzle straight wall. The fractal dimension can qualitatively judge the flow state of the boundary layer; however, it is necessary to distinguish between laminar boundary layers and hairpin vortices in the initial transition stage by considering the thickness of boundary layer.

Modular supersonic nozzle for the stable laser-driven electron acceleration.

The sharp density down-ramp injection (shock injection) mechanism produces the quasi-monoenergetic electron beam with a bunch duration of tens of femtoseconds via laser wakefield acceleration. The stability of the accelerated electron beam strongly depends on the stability of the laser beam and the shock structure produced by the supersonic gas nozzle. In this paper, we report the study of a newly designed modular supersonic nozzle with a flexible stilling chamber and a converging-diverging structure. The performance of the nozzle is studied both numerically and experimentally with the computational fluid dynamics simulation and the Mach-Zehnder interferometry method. The simulation results and the experimental measurements are well consistent, and both prove the effectiveness of the stilling chamber in stabilizing the gas flow.

Design and CFD Simulation of Supersonic Nozzle by Komega turbulence model for Supersonic Wind Tunnel

This paper presents an impressive design of a convergent divergent (C-D) nozzle using the method of characteristics for a Mach number 2 test section. The nozzle’s geometry was meticulously crafted in SolidWorks, and its performance was evaluated through a CFD simulation in Ansys Fluent R22 software. Results showed excellent agreement between the simulation and analytical data, with the Mach number ranging from 1.78 to 2. The study also compared turbulence modeling techniques, concluding that the k-omega model produced superior results. The supersonic wind tunnel achieved remarkable efficiency, completing a run at 1.8 Mach number in just 6 seconds. Overall, the study showcased exceptional accuracy and meticulousness.

Numerička analiza udarnog voza u konusnim mlaznicama sa ravnim grlom

The overexpanded flow regime in supersonic rocket engine nozzles presents different shock wave structures due to the geometrical configurations of the internal walls. In the present investigation, the study of the shock train phenomenon is addressed for a group of convergentdivergent conical nozzles with straight-cut throats for the overexpanded flow condition for NPR=12. The viscous and compressible flow field under stationary conditions is simulated with the RANS model in the ANSYSFluent R16.2 code, which applies the finite volume method (FVM) to discretize the computational domain. The Spalart-Allmaras turbulence model is used, and Sutherland's law is used for the viscosity as a function of temperature. The results show that, in the straight-cut throat section, as its length increases, the flow accelerates and decelerates with the presence of oblique shocks, which forms a definite shock train structure, where the flow velocity fluctuations are within the estimated Mach number range of 0.6 to 1.8. Increasing the throat length significantly affects the flow development at the nozzle outlet, which decreases the thrust force.

Ion acceleration from the interaction of ultrahigh-intensity laser pulses with near-critical density, nonuniform gas targets

Using one-dimensional, long-timescale particle-in-cell simulations, we study the processes of ion acceleration from the interaction of ultraintense (1020 W cm−2), ultrashort (30 fs) laser pulses with near-critical, nonuniform gas targets. The considered initially neutral, nitrogen gas density profiles mimic those delivered by an already developed noncommercial supersonic gas shock nozzle: they have the generic shape of a narrow (20 μm wide) peak superimposed on broad (∼1 mm, ∼180 μm scale length), exponentially decreasing ramps. While keeping its shape constant, we vary its absolute density values to identify the interaction conditions leading to collisionless shock-induced ion acceleration in the gas density ramps. We find that collisionless electrostatic shocks (CES) form when the laser pulse is able to shine through the central density peak and deposit a few 10% of its energy into it. Under our conditions, this occurs for a peak electron density between 0.35 nc and 0.7 nc. Moreover, we show that the ability of the CES to reflect the upstream ions is highly sensitive to their charge state and that the laser-induced electron pressure gradients mainly account for shock generation, thus highlighting the benefit of using sharp gas profiles, such as those produced by shock nozzles.

Tracking plume-regolith interactions in near-vacuum conditions

An experiment to track and measure the transient phenomenon of plume-liberated regolith in near-vacuum conditions was performed in a dedicated plume-regolith facility housed at the University of Glasgow. This facility with a total volume of around 82 m3 can simulate a soft or hard landing event on “extraterrestrial” sub-atmospheric pressures. Particle image velocimetry method was used to estimate the ejection velocity and ejected angle of regolith particles, and its limitations are discussed. Glass microspheres that are matched with the size of the Lunar and Martian moon “Phobos” surface regoliths are used as simulants. With an exit Mach number of 6.6, a heated convergent–divergent nozzle represents the lander nozzle. Preliminary results capture ejecta development up to 30 ms from plume impingement. Flow visualization reveals the initial moments of plume boundary growth and regolith ejection. The vector images indicate a triangular-shaped sheet of particles sweeping from the regolith bed at a positive inclination with a local maximum velocity close to 100 m/s. The low-density “Phobos” simulant advances at a higher speed, reaches higher elevations, and covers a larger spatial area compared to a higher-density “Lunar” simulant. Observation of the crater formation reveals the difference in cohesive forces between the selected simulants. A higher inclination of particle ejection of more than 50° adjacent to the jet indicates particle entrainment originating from the interior of the crater. Stream traces reveal the deflection of ejected particles upon impingement on the lander surface at close proximity.

CFD Analysis of De Laval Nozzle of a Hybrid Rocket Engine

: The study gives a general overview of the CFD-simulated gas flow via the nozzle of a De Laval rocket engine. In CFD software, the mesh is generated using the nozzle’s geometry. In this work, CFD methods are used to compare a number of factors with those derived from classical theory, such as pressure, velocity, temperature, and arear ratios. The results of computational modelling of CFD simulation are comparable to those found from theoretical calculations.

Optimization of Cold Spray Nozzles Based on the Response Surface Methodology

Spraying technical parameters are important factors that affect spraying efficiency. Most studies on spraying technical parameters use single-factor methods to study the speed of spray particles, and few scholars have studied the joint influence of multiple factors. This article uses gas temperature, particle size, and gas pressure as independent variables, and the independent variables interact. The design-expert method was used to establish a linear regression equation model of the velocity of sprayed Al and Cu particles at the Laval exit and the velocity before deposition with the substrate, and the response surface analysis method was used to predict the optimal spraying parameters of Al and Cu particles. The study found the contribution rate of three factors to particle velocity: the prediction of particle velocity at the exit of the Laval nozzle and before deposition with the substrate was realized; the error between the predicted value of particle velocity and the actual value obtained by simulation is less than 1.6 %, indicating that the speed linear regression equation established is effective and reliable in predicting the simulation results; the optimal spraying parameters and particle speeds of Al and Cu particles were obtained through response surface analysis.

Visualization of sidewall vortices in rectangular nozzle supersonic blowdown wind tunnel

This study focuses on the details of the geometry and dynamics of sidewall vortices observed in supersonic wind tunnels with a rectangular cross section of the nozzle and the test section. The formation of sidewall vortices limits the accuracy of the data measured during wind tunnels' testing due to a reduced area of uniform core flow results. Most of the test data presented in this work are generated using Mie scattering visualization for M = 4 flow, with CO2 seeded up to 7% mole fraction. The Mie scattering results are complemented by data from fast pressure sensor and schlieren visualization. It is shown that the formation of vortices is caused by a transverse pressure gradient realized in the supersonic nozzle due to the gas under-expansion. The vortex external mixing layer is strongly perturbed in time but remains globally geometrically similar with streamwise distance. The vortex-generated dominant flow disturbances are in the frequency range of f = 10–50 kHz, doubling the magnitude of baseline power spectral density. The authors' viewpoint is that sidewall vortex generation is a more generic phenomenon than was thought previously.

Computational and Investigational Proportional Flow Study on Cd Nozzle

As part of our study , we had to design, produce, and test a convergent-divergent type nozzle with a specific area ratio. The goal of this project is to replicate the operation of a converging-diverging nozzle, which is possibly the most significant and fundamental piece of engineering hardware involved with propulsion and high-speed gas flow.For this, we first examined a specific area ratio. Three distinct designs are constructed for the given area ratio (convergent, divergent, and convergent divergent).The flow through the nozzle is analysed under various back pressure situations. Then, using the values obtained from the analysis, we constructed the nozzle and evaluated its operation. We also tested the choke conditions under varied back pressures and the mass flow rate that corresponds to it. Finally, we plotted the curve of mass flow rates vs. pressure distribution with practical values. Thus, with the assistance of our department faculty, we successfully accomplished this assignment.

Supersonic jet noise and screech tone suppression using cross-wire

This experimental investigation is aimed at assessing how the introduction of a cross-wire at the exit of a CD nozzle influences the performance of a supersonic nozzle. The study focuses on cold air jets generated by De Laval nozzles equipped with cross-wires and baseline configurations, particularly at design Mach numbers of 1.5 and 1.75. The investigation involves collecting measurements from the noise field emitted by the cross-wire nozzle with a 2% obstruction at the exit. This passive control approach effectively reduces the occurrence of screech tones in both over-expanded and under-expanded conditions in the azimuthal plane at appropriate operating pressures. Various acoustic parameters, including sound pressure levels (SPL), Strouhal numbers, and the overall sound pressure level spectra (OASPL) are recorded. Schlieren imaging captures images of shock cell patterns, illustrating the impact of shock-associated noise. In comparison to a baseline nozzle, the results demonstrate that a CD nozzle equipped with a cross-wire proves to be a proficient screech tone suppressor, leading to an average reduction of up to 5 dB in OASPL in under-expanded and over-expanded scenarios.

The influence of gas heating on the calculated supersonic parameters of gas-powder flow at slag blower in the converter. Message 2

The article presents the results of numerical modeling of the interaction of a supersonic non-calculated gas-powder jet with the surrounding strongly heated environment of the converter cavity, including slag particles ejected by the jet. The method of determining the depth of penetration of the jet into the melt is the subject of many years of discussion, but it has not been solved analytically. A new approach to solving this problem is proposed, which consists in the fact that in this work the structure is considered not according to the laws of subsonic turbulent flow, but as supersonic, not calculated. In this paper, there is a task - to increase the stability of the slag crust, nitrogen supply of MgO powder is provided, which, in turn, enters the jet and slows it down. To solve this problem, the solution of many parametric equations is proposed to establish the effect of heating on the qualitative characteristics of the slag crust on the surface linings. A physical model has been created that predicts the outflow of a gas-powder jet (N2 + powder) from a Laval nozzle. The formation outside the jet nozzle is established, which becomes a supersonic non-computational structure with a shock wave. The most important hydro-gas-dynamic characteristic of the gas jet flow is its momentum, which depends on a number of factors and physical effects. The scheme for solving a fairly high-tech problem involves the following: calculation of the parameters of the gas-powder flow at the exit from the nozzle; calculation of the amount of added gas mass from the environment; temperature: pulse speed; jet power, etc. It was established that in some cases, when a chemical connection between the slag and the lining is ensured (when there is an optimal value of MgO and CaO in the slag), it is possible to stop the supply of refractory powder and then the slag will be inflated only with a nitrogen jet. Using the law of constancy of momentum in different cross-sections of the jet (for example, in the outlet cross-section of the nozzle and in the fixed cross-section of the XX stream), it is possible to calculate: total momentum, average mass velocity of the nitrogen-powder jet, average mass temperature of the jet. It is shown that the power of the gas-powder jet flowing into the melt is most significantly affected by the heating of the gas-dispersed flow to the temperature before the nozzles. It was established that an increase in temperature from 50°C to 600°C leads to an increase in momentum by almost 2.75 times. The joint solution of almost 50 equations (messages 1 and 2) makes it possible to visually present the picture of the interaction of the supersonic jet with shock waves and melt, as well as to develop recommendations for improving the energy efficiency of slag-blowing technology. Since conducting an experiment in the converter cavity is difficult, the results of numerical calculations are verified by the method of special cases