Supersonic Gas Research Articles

Primary and secondary breakup of molten Ti64 in an EIGA atomizer for metal powder production

Electrode Induction melting Gas Atomization (EIGA) is a free-fall gas atomization process used to produce metal powders, where a swirling supersonic gas jet hits a molten metal stream atomizing it into droplets through various fragmentation mechanisms. Fragmentation mechanisms of molten Ti64 are investigated by high-speed video visualization. The role of gas pressure and melting chamber overpressure on the fragmentation mechanisms and on the particle size distribution is determined. The mechanisms observed are fiber breakup, bag breakup and Rayleigh breakup for primary fragmentation and bag breakup and shear breakup for secondary fragmentation. Increasing the gas pressure promotes shear breakup and creates finer droplets. A model based on log-stable law is proposed to fit the mass distribution according to the dominant fragmentation regime. A good agreement is observed between the different analysis (dominant atomization regime, mass cumulative distribution evolution, parameters of log-stable law). A criterion for prediction of nozzle clogging is devised.

Development of technology for obtaining nanostructured composite coating of Kh20N80–Cr–TiC

The paper presents results of a comprehensive study on the development of technology for the production of composite nanostructured functional coatings based on the Kh20N80 – chromium – TiC system using the supersonic cold gas dynamic spraying method. Composite coating powders are obtained by chromium plating of a matrix powder made of alloy Kh20N80 followed by the application of a reinforcing coating of TiC nanoparticles. The resulting coating has a high level of microhardness, modulus of elasticity and resistance to wear. A distinctive feature of the resulting coating is its reliable operation without destruction for a long time (more than 4800 hours).

RESEARCH OF SUPERSONIC FLOW IN SHORTENED NOZZLES OF ROCKET ENGINES WITH A BELL-SHAPED TIP

The flow in a shortened nozzle with a bell-shaped tip is considered. A comparison of the wave structures of the supersonic gas flow in shortened nozzles with short and long tips formed by compression and stretching of the original bell-shaped nozzle for connection, respectively, with the long and short conical part of the base nozzle at the same nozzle length was carried out. Under operation conditions at sea level and low pressure at the nozzle inlet (P0<50·105 Ра), a large-scale vortex structure, starting from the corner point of the nozzle inlet, is observed in both nozzles. In addition, in the long tip, a small-scale vortex is observed on the wall near its cut. A barrel-shaped wave structure of hanging jumps with a closing Mach disc is formed in the flow in both nozzles, inside which a "saddle-shaped" wave structure of low intensity is noticed. In the separation flow in the tip (when Р0<50·105 Ра and Рн = 1·105 Ра), the pressure on the wall in the separation zone is slightly lower (by ≈ 5-10%) than the external pressure Рн. When the engine is operating in the upper layers of the atmosphere, the static pressure on the section of both tips is proportional to the pressure at the entrance of the nozzle. In the cross-section, starting from the axis of the nozzle to ~0.89 R/Ra (the ratio of the current value of the radius R to the radius of the nozzle wall at the outlet Ra), the pressure decreases to a value proportional to the pressure at the nozzle inlet. Then, it increases linearly to the value of the pressure on the tip wall, which is proportional to the pressure at the nozzle inlet. This is due to the wave structure of the flow inside the nozzle. It was established that with a decrease in the length of the nozzle conical part, the impulse coefficient of the nozzle decreases significantly for operating at sea level and slightly decreases for operating in the upper layers of the atmosphere. The results of calculations correlate satisfactorily with the experimental study results of the flows in shortened nozzles with a bell-shaped tip

Laser-machined two-stage nozzle optimised for laser wakefield acceleration

In this paper, the modelling and manufacturing of a two-stage supersonic gas jet nozzle enabling the formation of adaptive plasma concentration profiles for injection and acceleration of electrons using few-cycle laser beams are presented. The stages are modelled using the rhoSimpleFoam algorithm of the OpenFOAM computational fluid dynamics software. The first 200–300 ${\rm \mu}$ m diameter nozzle stage is dedicated to 1 % N2 + He gas jet formation and electron injection. By varying the pressure between the first and second stages of the injectors, the electron injection location could be adjusted, and the maximum acceleration distance could be ensured. By changing the concentration of the nitrogen in the gas mixture, the charge of the accelerated electrons could be controlled. The second nozzle stage is designed for acceleration in fully ionised He or hydrogen gas and forms the optimal plasma concentration for bubble formation depending on the laser pulse energy, duration and focused beam diameter. In order to reduce the diameter of the plasma profile formed by the first nozzle and the concentration drop gap between the two nozzles, a one-side straight section was introduced in the first nozzle. The shock wave reflected from the straight section of the wall propagates parallel to the shock wave of the intersecting supersonic jets and ensures a minimal gap between the jets. The second-stage longitudinal plasma concentration profile could have an increasing gas density gradient to compensate for dephasing between the electron bunch and the plasma wave due to wave shortening with increasing plasma concentration.

Comparison of Computational Methods and Approaches Applied in Formulation of Boundary Conditions in Lagrange’s Ballistic Problem

This paper compares algorithms for constructing a differential solution to the gas dynamics equations in the surrounding of a moving boundary. In order to compare the algorithms, the Lagrange problem, also known as the piston problem, was chosen as a test problem. A comparison was made between the author’s algorithm based on the method of characteristics and the classical approach with a fictitious cell using the solution of the Riemann problem. Calculations were carried out for the case of subsonic and supersonic gas motion. Comparisons were made on a fixed grid with a dynamically expanding cell (Euler grid) and on a uniformly expanding grid (Arbitrary Lagrangian-Eulerian – ALE grid). The problem was solved using numerical schemes of second order in time and space Lax - Wendroff type: the Richtmyer scheme and the MacCormack scheme. The results of calculations using the characteristics method were used as a benchmark solution. The comparative analysis carried out allows conclusions to be drawn regarding the accuracy of the individual approaches, as well as the scope of their applicability.

Jet penetration and particle dispersion behaviors of supersonic gas–solid oxygen jet under high ambient temperature

Supersonic gas-powder mixing jets are widely utilized across various industrial processes such as fluidized bed, drug delivery, and steelmaking. In the current study, the impact of high-temperature environment on flow pattern and heat transfer behaviors of supersonic gas-powder flow in the convergent-divergent nozzle are numerically studied via Euler-Lagrangian method. Following validation through experiments, simulations are conducted across diverse conditions, involving four distinct ambient temperatures and powder feeding rates. The results reveal the following insights: (i) Increasing the ambient temperature from 500 K to 1000 K enhances the gas penetration depth and slows down the decay of particle velocity; (ii) The low-temperature gas within the jet core can obtain more energy from external environment via convection and thus expands more sufficiently; (iii) Once the powder mass flow rate surpasses a specific threshold of 8 kg/s, it fundamentally disrupts the supersonic flow structure and causes a large subsonic region downstream of the nozzle exit, substantially diminishing the capacity to accelerate particles; (iv) Increasing the particle feeding rate to 4 kg/s markedly amplifies particle radial dispersion; (v) Increasing the velocity difference between phases enhances both momentum and energy transfer. These findings offer significant insights into the behavior of supersonic gas-powder jets within high-temperature environments, contributing to the understanding of their dynamics and potential applications.

APPLICATION OF TWISTER SUPERSONIC GAS-LIQUID SEPARATOR FOR IMPROVED NATURAL GAS RECOVERY IN A PROCESS STREAM

Natural gas is one of the most precious natural resources that generates foreign earnings for its host nation. Energy is the building block of modern society and natural gas is one of the cleanest primary energy sources. The production and subsequent recovery of natural gas is a challenging aspect of the entire natural gas value chain. One of the problems associated with natural gas utilization is the extraction and conditioning of the gas, as most of the fractions are extracted with certain percentages of water and other contaminants. To solve the problem of liquid carryover and gas entrainment in gas processing and recover an excellent volume of gas, several types of gas separators have been developed. This case study aims to solve the problem of gas wastage and recurrent plant downtime. Notore Chemical Industries is our focus as one of the largest natural gas consumers, situated in Rivers State Nigeria. The company has several plant downtimes due to the inefficiency of the conventional separator. The inefficiency of the installed knock-out drum separator in dispersing the condensate from the feed supplied by Nigerian Gas Company (NGC) and delivering the required dry gas to the plant battery limit has been one of the leading causes of the plant recording downtime. This work presents a reliable separation process using the Twister supersonic gas separator to recover a high percentage of dry natural gas (Methane). Feed gas data was collected from the plant after several visits and a computer-based simulation was conducted. From the simulation using the Aspen Hysys package, it was seen that the Twister supersonic gas separator is more efficient than the knockout drum separator. Less methane and less condensate were produced using the knockout drum separator at 0.699% and 0.092% respectively while the Twister supersonic gas separator produced methane and condensate at 95.15% and less condensate at 0.0047% respectively.

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.

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.

CFD study of gas-powder injection characteristics in a novel lance with supersonic shrouding jet

Supersonic gas–solid jets are widely applied in the spraying coating processes, drug delivery, and metallurgical reactors, due to exceptional penetrating capabilities. In this study, a novel lance is designed to increase the penetration depth of gas–solid flow by utilizing a supersonic shrouding jet (SSJ). Subsequently, the numerical model based on the Eulerian-Lagrangian framework is applied to analyze the supersonic gas-powder flow within the lance. After validating the reliability of numerical model with experimental data, the gas-powder flow characteristics are discussed. The results indicate that the presence of SSJ enhances the powder velocity and penetration depth significantly by blending supersonic gas. Moreover, the particle-gas momentum interaction primarily occurs inside the central pipe and downstream of the lance exit. Along the radial direction, the particle dispersion is the result of the combined interplay between lift force and particle–particle collisions. The lift force enhances particle collision frequency, and these collisions, in turn, facilitate the conversion of axial momentum into radial momentum, resulting in substantial radial acceleration. When SSJ exits, the particle radial dispersion is constrained, primarily due to the reduced particle residence time. Additionally, the introduction of low-temperature oxygen from SSJ results in a reduction in both the carrier gas and particle temperatures. The results provide meaningful insights into understanding the supersonic gas–solid flow mechanisms of the SSJ lance.

Formulation of the problem of structured-element modeling of jet interference in a nozzle block

The objects of research are supersonic composite jet flows, as well as structural elements of flows (shock and acoustic waves, gas dynamic discontinuity surfaces), which act with each other and with various technical objects. Such objects may be structural elements or parts of special technical systems that experience loads during operation, or are subjected to targeted effects in order to improve their mechanical properties. The research is carried out in order to develop mathematical models describing the interaction of structural elements of the flow supersonic gas jets among themselves in composite jets. When performing the work, various methods allowing to model gas-jets flows and processes are considered. To solve the problem method of structured- element modeling of gas-jet processes was chosen [1–4]. This method focused on the creation of engineering methods for calculating launch gas-dynamics problems. The scope of application of the method can cover not only space roket, also civilian industry is in part where they face the problems of jet flow. For example with the need to improve the reliability of products, their strength and metal characteristics. The direction of subsequent theoretical and experimental research, which determine the development of the structural-element method, are determined and clarified.

Analysis of a turbofan engine using a parametric loop

PurposeIn this study, the performance analysis of the split flow turbofan engine with afterburners has been examined using the parametric cycle analysis method. The purpose of this study is to examine how engine performance is impacted by design parameters and flight ambient values and to develop a software in this context.Design/methodology/approachSoftware has been developed using the open-source PYTHON programming language to perform performance analysis. Mach number, compressor/fan pressure ratio, bypass ratio and density were used as parameters. The effects of these variables on engine performance parameters were investigated.FindingsParametric cycle analysis has been calculated for different flight conditions in the range of 0–2 M and 0–15,000 m altitude for turbofan engines. With this study, basic data were obtained to optimize according to targeted flight conditions.Practical implicationsAs a result of the performance analysis, the association between the flight conditions and design parameters of engine were determined. A software has been developed that can be used in the design of supersonic gas turbine engines for fast and easy simulation of the design parameters.Originality/valueThe variables used in the literature have been analyzed, and the results of the studies have been incorporated into the developed software, which can be used in innovative engine design. Software is capable to be developed further with the integration of new algorithms and models.

SPECTRAL DYNAMIC STIFFNESS METHOD FOR THE FLUTTER PROBLEM OF COMBINED PLATES

At present time, the spectral dynamic stiffness method is being actively developed as an alternative to the finite element method for vibration and stability problems of composite structures from beams, rods, plates and shells. This approach, based on exact solutions of governing differential equations, makes it possible to more effectively study the problem in the medium and high frequency ranges, and gives analytical expressions for natural modes. It is proposed to use the advantages of this method to study the problems of dynamic stability and flutter of an orthotropic composite plate in a supersonic gas flow. Using the linear approximation of piston theory, solution of the problem is investigated according to the Galerkin method on the basis of the eigenforms of a composite plate in vacuum. According to this approach the boundary value problem is reduced to a homogeneous infinite linear algebraic system of equations with coefficients are depending from physical-mechanical and geometrical parameters of the problem. The frequency parameter is included in the system linearly, that allows us to reduce eigenproblem for infinite system to the problem of determining the eigenvalues and vectors of a matrix. The convergence of the Galerkin method depending on the number of basis functions is studied numerically. It is shown that the first 16 eigenforms provide the good convergence of the method. Examples of numerical implementation are given, obtained solution allow us to study the dependence of the critical velocity from the properties of the material and geometry of the combined plate.

Supersonic dusty gas flow past a cylinder in Eulerian–Lagrangian framework

The present study utilizes computational methods to analyze two-dimensional particle-laden flow over a circular cylinder. The effect of seeding of dust particles in the viscous flow of a compressible gas is analyzed. A new solver has been developed for the purpose of studying multi-phase flows in the supersonic regime. Most of the prior research has primarily focused on flows characterized by low Mach numbers and the absence of shock waves, and there have been very few studies dealing with supersonic dusty gas flows. This study considers a supersonic Mach number and investigates the effect of particle size and particle volume fraction on dusty-gas flow over a circular cylinder. The simulation results reveal that the seeding of particles in the flow creates perturbations. The present work also highlights the influence of particles on flow separation and the subsequent increase in the skin friction coefficient and coefficient of drag. The study shows that for supersonic flows, at the same volume fraction, larger particle size creates more instabilities in the flow, while smaller particles are responsible for increased drag on the cylinder, owing to a greater frequency of collisions.

Optimally Controlled Turbulent Boundary Layers in Supersonic Gas Flows

Optimally Controlled Turbulent Boundary Layers in Supersonic Gas Flows

A hybrid computational approach for modeling cold spray deposition

Cold spray (CS) is a cold-state technology that uses high-velocity supersonic gas flow to propel and deposit powder particles onto a substrate surface. The design and optimization of the cold spray deposition process were recently achieved via the experimental trial-and-error approach, which is laborious and costly. The present study presents a computationally efficient hybrid method for simulating cold spray coating deposition, applied explicitly to Ni coating used for wear applications. The model effectively synergizes meshless and meshed computational schemes in predicting the thermo-mechanical deformation of the impacting Ni particles and SS304 steel substrate. During the simulations, the point cloud (PC) of deformed particle domains is converted into a high-quality finite element (FE) mesh with novel PC processing algorithms. The simulations are carried out for various particle characteristics and spraying conditions. The numerical predictions are validated by comparing them with other numerical schemes and previous experimental studies. The main results indicate that the kinetic energy and morphology of the impacting Ni particles strongly influence plastic deformation and temperature rise in the substrate and predeposited coating particles. Plastic deformation is more prominent at the particle edges and mating material interfaces. At the same time, the temperature rise does not reach the melting point but can allow for recrystallization near highly localized regions of the coating microstructure, even at lower deposition rates. Compressive residual stresses are also observed across the coating and substrate layers, with a non-uniform and nonlinear residual stress field due to complex interactions among neighboring particles. The study aims to provide a robust numerical framework for designing and optimizing cold spray deposition parameters for industrial coatings, bridging the knowledge gap and enabling efficient and cost-effective simulations for process optimization.

Thermal protection of a lunar lander from multi-engine plumes using thin film cooling

During the descent and ascent of the lunar lander, the gas plume exhausted from its engine imposes a significant thermal load on the lander when it approaches the lunar surface. This challenge becomes more pronounced for multi-engine landers due to the intricate interactions between their plumes, making it difficult to ensure adequate thermal protection for the lander. In this study, a thermal protection method utilizing a supersonic cold gas film is proposed to shield the lander bottom from high-temperature backflow from the lunar surface. Unlike conventional film cooling that relies on the boundary layer flow, our approach is specifically designed to accommodate irregular surfaces of the lander bottom. The applicability of this heat protection method in vacuum or low-pressure environments is first confirmed. Subsequently, the effects of three key annular injector parameters, including total pressure, expansion ratio, and injection angle are investigated. Our findings reveal that increased coolant total pressure results in better protection, while the effects of the expansion ratio vary with different coolant total pressures. Under our conditions, an annular injector angle of 45∘ is determined to be the optimal choice for enhancing cooling efficiency.

Experimental investigation on the aero-optical effects of supersonic gas films with various cooling fluids.

Despite the fact that a supersonic cooling gas film can efficiently insulate aerodynamic heating, its interaction with the mainstream generates a sophisticated flow structure which may cause significant aero-optical ramifications. This study aims to analyze the fluid structure and wavefront distortion of supersonic gas film when subjected to varying nozzle pressure ratios (NPR) by employing two distinct cooling refrigerants, namely C O 2 and air. Within the NPR range of 0 to 2, a linear relationship exists between the wavefront distortion of both C O 2 and air films, while the C O 2 film exhibits higher wavefront distortion than the air. Additionally, the influence of condensation on the discrepancies in aero-optical effects of the two refrigerants is discussed.

Detailed and simplified plasma models in combined-cycle magnetohydrodynamic power systems

Magnetohydrodynamics (MHD) is a subject concerned with the dynamics of electrically conducting fluids (plasma) and can be applied in electric power generation. As a unique technology for producing direct-current electricity without moving parts, it can be utilized within a high-temperature topping power cycle to be combined with a traditional bottoming power cycle, forming a combined-cycle MHD system. This study presents governing equations for the electric field and current density field within a moving plasma subject to an applied magnetic field. The modeling equations are described at four descending levels of complexity. Starting with the first level of modeling, which is the most general case, where no assumptions are made regarding the electric field, plasma velocity field, applied magnetic field, or electrode geometry. In the second level of modeling, the magnetic field is treated as one-dimensional. In the third level of modeling, a specific Faraday-type magnetohydrodynamics plasma generator channel is considered, having two continuous electrodes acting as parallel constant-voltage terminals. In the fourth (and simplest) level of modeling, an additional approximation is made by setting the Hall parameter to zero and replacing all vector fields with scalar quantities. For that simplest model, a representative set of operation conditions (electric conductivity 20 S/m, temperature 2800 K, supersonic plasma gas speed 2000 m/s with Mach 2.134, and magnetic flux density 5 T) shows that the optimum idealized electric power that can be extracted from a unit volume of plasma is estimated as 500 MW/m3. This is a much larger volumetric power density than typical values encountered in reciprocating piston-type engines (0.2 MW/m3) or rotary gas turbine engines (0.5 MW/m3). Such an extremely high power density enables very compact power generation units.

Development of technology for obtaining functional coatings from Kh15Yu5 steel powders

The paper presents the results of research on the development of technology for the application of functional coatings with high values of adhesion strength, microhardness and wear resistance using the method of supersonic cold gas dynamic spraying. Oxidized powder from X15Yu5 steel was used as a starting material for obtaining such coatings.