Nozzle Area Research Articles

Numerical Simulation and Experimental Study the Effects of Process Parameters on Filament Morphology and Mechanical Properties of FDM 3D Printed PLA/GNPs Nanocomposite.

The selection of optimal process parameters has a decisive effect on the quality of 3D printing. In this work, the numerical and experimental methods were employed to investigate the FDM printing deposition process of PLA/GNPs nanocomposite. The effect of process parameters on cross-sectional morphology and dimension of the deposited filament, as well as the mechanical property of the FDM printed specimens were studied. The extrusion and the deposition process of the molten PLA/GNPs nanocomposite was simulated as a fluid flow by the paradigm of CFD, the effects of printing temperature and shear rate on thermal-physical properties, such as viscosity and surface tension, were considered in models. Under the assumptions of non-Newtonian fluid and creep laminar flow, the deposition flow was controlled by two key parameters: the nozzle temperature and the nozzle velocity. The numerical model was verified by experiments from four aspects of thickness, width, area, and compactness of the deposited PLA/GNPs nanocomposite filament cross-section. Both the numerical simulation and experiment results show that with the increase of nozzle temperature and nozzle velocity, the thickness, area, and compactness of the deposited filament decreases. While the width of deposited filament increased with the increase of nozzle temperature and decrease of nozzle velocity. The decrease in thickness and the increase in width caused by the change of process parameters reached 10.5% and 24.7%, respectively. The tensile strength of the printed PLA/GNPs specimen was about 61.8 MPa under the higher nozzle temperatures and velocity condition, an improvement of 18.6% compared to specimen with the tensile strength of 52.1 MPa under the lower nozzle temperatures and velocity condition. In addition, the experimental results indicated that under the low nozzle velocity and nozzle temperature condition, dimensional standard deviation of the printed specimens decreased by 52.2%, 62.7%, and 68.3% in X, Y, and Z direction, respectively.

Design Optimization and Variable Geometries Implementation of a High Bypass Three-Shaft Turbofan Engine for EIS2050

Abstract This paper aims to develop an advanced three-shaft turbofan engine with ultrahigh bypass ratio (BPR) for entry-into-service (EIS)2050. The boundary approaching method is utilized to obtain the optimal engine for a series of engines with different fan diameters. Furthermore, the flight mission analysis was carried out to fully consider the engine performance and weight penalty. The optimum engine employs a 3.26 m fan diameter with ultrahigh BPR reaching 21.39. The corresponding specific fuel consumption (SFC) is 11.42 (g/s)/kN, which is 3.88% lower than the 2.95 m fan diameter engine. However, the weight penalty has offset part of the benefits, and the block fuel reduction is 2.5%. Sensitivity analysis results reveal that the low-pressure turbine (LPT) efficiency plays a dominant role in engine performance. Afterwards, the effects of variable geometry are investigated including the blow-off valve (BOV), variable inlet guide vane (VIGV), and bypass variable area nozzle (VAN). Results show that combining the three measures would boost engine performance and save fuel. The designed schedule for the combination of VIGV, BOV, and VAN has generated a reduction in block fuel, NOx, CO2, and H2O reaching 3.36%, 5.55%, 2.47%, and 2.53%, respectively.

Part-load efficiency boost in offshore organic Rankine cycles with a cooling water flow rate control strategy

Global concerns regarding greenhouse gas emissions and global warming have necessitated the speed up in using renewable energies and more efficient use of fossil fuels in the oil and gas industry. Harvesting gas turbine heat by organic Rankine bottoming cycles has raised as a potential solution to cut carbon dioxide emissions in offshore oil and gas installations. Offshore power cycles are expected to operate most of their operational life at part-loads where they suffer from poor efficiency. The purpose of this article is to boost the part-load efficiency of offshore organic Rankine cycles and keep it as close as possible to the design value. Here an operational strategy based on cooling water flow control is developed and added to a sliding pressure control logic and a variable area nozzle turbine control strategy. An in-house tool is developed for the design of organic Rankine cycles and the simulation of off-design control strategies. A design methodology is presented to optimize the cycle power output while minimizing the cycle footprint offshore. The proposed control strategy was successful in keeping the part-load efficiency close to design value and achieving a 5% reduction of annual carbon dioxide emissions.

Simulation and validation of the gas flow in close-coupled gas atomisation process: Influence of the inlet gas pressure and the throat width of the supersonic gas nozzle

The effectiveness of a close-coupled gas atomisation process largely depends on the operational and the geometric variables. In this study, Computational Fluid Dynamics (CFD) techniques are used to model and simulate the gas flow in the melt nozzle area for a convergent-divergent, close-coupled gas atomiser in the absence of the melt stream. Firstly, a reference case, in which the atomisation gas is nitrogen at 50 bar and a supersonic gas nozzle with a throat width of L0 has been modelled, is presented. Then, the influence of both the inlet gas pressure and this design parameter are investigated, comparing the numerical results provided by simulations varying the inlet pressure from 5 to 80 bar and modelling different convergent-divergent gas nozzles with throat widths of 0.29∙Lo, 0.5∙Lo, 0.77∙Lo and 2∙Lo respectively. The simulation results show how similarly these two parameters modify gas mass flow rates, gas velocity fields, aspiration pressures in the melt delivery tube or the size of the recirculation zones below the melt nozzle. Therefore, it can be stated that this geometric variable of the gas nozzle may be as relevant as the inlet pressure in the atomisation process. The most important novelty of this study is related to experimental validation of the numerical results using the Particle Image Velocimetry (PIV) technique and through direct measurements of gas mass flow rates, with a clear correlation between simulated and measured data. Moreover, some results obtained with experimental atomisations using copper and nitrogen are also presented. The experimental results show that finer powders are produced by increasing the atomising pressure or the throat width of the supersonic gas nozzle, which can be directly related to the gas flow dynamics calculated numerically.

Розрахунково-методичне забезпечення для проведення комплексних розрахунків надзвукового обтікання летальних апаратів з прямоточними повітряно-реактивними двигунами

This paper discusses the use of the authors’ fast methods and programs for the calculation of 3D supersonic flow about a flying vehicle and thermogas dynamic processes in the components of an airframe-integrated ramjet. To conduct fast comprehensive calculations, use is made of marching methods, which are two to three orders of magnitude faster than pseudoviscosity methods. 3D supersonic flows about the airframe, in the inlet section of the air intake, and in the exhaust jet are calculated using a “viscous layer” model or Godunov’s scheme for the inviscid approximation. Subsonic flows in the outlet section of the air intake and in the combustion chamber are calculated using a “narrow channel” or a quasi-one-dimensional model. The elements of the presented methods and programs that complement a previously proposed fast comprehensive model are described in more detail. A method for assigning the spatial shape of the flying vehicle surface and the ramjet duct walls is described. A simplified approach to determining the critical area of the exit nozzle in the one-dimensional approximation is proposed. The paper substantiates the advantages of marching methods over pseudoviscosity ones in the predesigning of ramjets with direct account for flow choking, which may occur in the combustion chamber or the exit nozzle. The calculated 3D flows in the individual components and the full assembly of a stylized-shape flying vehicle are presented. The main advantages of the proposed methods and programs are their comprehensiveness and fast computation speed. Their use in the calculation of 3D supersonic flow about a ramjet flying vehicle shortens the ramjet component predesigning time.

Numerical analysis on effect of blend ratio on co-combustion characteristics of semi-coke and bituminous coal in swirl burner

ABSTRACT Semi-coke is the coproduct of low-rank coal in the preparation of oil and gas, but the current utilization rate of fine-powder semi-coke is low, which limits the development of the low-rank coal pyrolysis industry. This paper uses the numerical simulation method to study the co-combustion characteristics of a large proportion of bituminous coal mixed with semi-coke in a swirl burner. The results show that, in the primary combustion region, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are lower, and the O2 concentration increase is higher. In the over-fired air (OFA) nozzle area, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are higher, and O2 concentration is lower. In addition, with the increase of the blend ratio of semi-coke, the main combustion position of the fuel is transferred to the vicinity of the OFA nozzle area, which weakens the degree of air-staging combustion of the furnace. The synergistic effect of co-combustion of semi-coke and bituminous coal helps to reduce the NO concentration at the furnace outlet and improve the combustion efficiency. By comprehensive considering the stable operation of the boiler, burnout rate, and NO emission concentration, the recommended blend ratio of semi-coke should not exceed 60%.

The Effects of Nozzle Inclination, Area Ratio, and Side-Hole Aspect Ratio on the Flow Behavior in Mold

During the steel continuous casting, the submerged entry nozzle (SEN) plays a crucial role in the fluid characteristic of fluid steel, which further affects the slab quality. In this paper, a nozzle model is developed to study the influences of nozzle inclination, nozzle area ratio, and side hole aspect ratio on the fluid characteristic of fluid steel. The results show that when the nozzle angle increased from 10° to 20°, the impact points of the narrow surface were 0.402 m, 0.476 m, and 0.554 m away from the meniscus, respectively. In addition, when the nozzle area ratio increased from 0.96 to 1.16, it resulted in a significant decrease of the speed of high-temperature liquid steel flowing out of the nozzle. Moreover, when the side-hole aspect ratio was 1.47, the maximum turbulent kinetic energy of the free surface reached 0.00141 m2 s−2. Furthermore, when the aspect ratio was 1.67 and 1.84, a slight difference existed, and the maximum turbulent kinetic energy was almost 0.00095 m2 s−2. The proposed model can provide theoretical basis and guidance for nozzle optimization.

A-Variant Design of Hypersonic Ludwieg Tube Wind Tunnel

To improve the operation efficiency of conventional Ludwieg tube tunnel, a fast-acting valve is usually deployed between the storage tube and Laval nozzle in order to separate the high- and low-pressure air. However, the disturbance produced by the fast-acting valve as well as the nonuniform heating of storage tube affects the flow quality of the hypersonic Ludwieg tube. Stimulated by the motivation of overcoming the mentioned problems, the feasibility of a novel configuration of hypersonic Ludwieg tube is explored in this research. Upon this study, we introduced an additional Laval nozzle and settling chamber to the conventional Ludwieg tube tunnel, while the cross-section area of the main Laval nozzle is smaller than that of the introduced Laval nozzle. To begin with, the flow evolution along the dual-throat Ludwieg tube was analyzed theoretically; subsequently, numerical simulations were conducted to study the starting process of the dual-throat Ludwieg tube tunnel, and emphasis was placed on the influence of different throat area ratios and settling chamber lengths upon the startup time of wind tunnel. Lastly, the flowfield of the dual-throat Ludwieg tunnel was characterized by measuring the Mach number distribution and pitot pressure fluctuation in the test section as well as the pressures along the overall tunnel. The results show that this novel configuration of Ludwieg tube is applicable and it offers the opportunity for flow quality improvement for conventional Ludwieg tubes with small penalty of reducing the tunnel’s efficient running time.

Design and Geometrical Optimization of Nozzle to Reduce Noise for Jet Engine

A scientific payload is used for deep space observations. It consists of several components, which are used to observe and detect the objects and its details. Such payloads are used to collect data for tin-filer research and understanding about the universe and to know its hidden mysteries. This research is conducted using several observatory instruments like, X-ray spectroscope, hyper spectral image camera, laser ranging instruments, etc. In this project. a mechanical configuration of X-ray spectroscope is designed considering all the design parameters and constraints. Boeing recently tested a scaled variable area jet nozzle capable of a 20% area change Shape Memory Alloy actuators were used to position 12 interlocking panels at the nozzle exit. A closed loop control system was used to maintain a range of constant diameters with varying flow conditions and to vary the diameter under constant flow conditions. Acoustic data by sideline microphones and flow field measurements at several cross-sections using PIV was collected at each condition. In this paper the variable area nozzle's design is described. The effect of the nozzle's diameter on acoustic performance is presented flow field data is shown including the effects of the joints between the interlocking panels.

Performance of a turbojet engine with fluidic thrust vectoring

AbstractThe objective of the present work is to estimate the performance of a turbojet engine during Fluidic Thrust Vectoring (FTV) employed by injecting the secondary-jet at the throat of a convergent nozzle. The nozzle performance maps and effective nozzle throat area obtained from experiments are coupled with the performance of a conventional engine (without FTV) using an iterative algorithm developed as a part of this work. The performance is estimated for different flow rates of secondary-jet sourced either from a separate compressor or the engine’s compressor. During FTV, the operating point shifted towards the surge line with increased turbine entry temperature. The desired and obtained vector angles and thrust magnitudes are different. At high secondary-jet flow rates, the turbine operation moved out of its performance map. These aspects should be incorporated while integrating the FTV at the system level, thus, asserting the importance of FTV studies coupled with engine performance.

Insights into ZrO2- and Al2O3-based submerged entry nozzle clogging for the continuous casting of RE-treating sulfur resistant casing steel

The ZrO2- and Al2O3-based submerged entry nozzle (SEN) clogging during continuous casting of a RE-treating sulfur resistant casing steel is studied experimentally based on morphological analysis and the related thermodynamic calculations. The results show that the ceramic cloggings exists both in the inner-wall and outlet regions of SEN, while the latter is the main reason for terminating the casting with its clogging reaching 77% in the nozzle cross section area. The clogging is caused by RE-containing inclusions from molten steel and reoxidation products by the reaction between RE in molten steel and the initial formed cloggings on nozzle refractory. The possible existence state of RE in molten steel with its content has been discussed, and the clogging mechanism studied in detail. To prevent nozzle clogging, suggestions are given for continuous casting of the RE-treating steel with a modified RE treatment strategy for less solid inclusions and solute [RE] presented in liquid steel during refining process. Additionally, the optimization of nozzle geometry and its refractory materials may help as well.

The influence of Variable Geometry Control on a R290 Ejector Refrigeration System

The large-scale deployment of ejector refrigeration systems (i.e., solar-based ejector refrigeration systems), although representing a promising alternative compared with mechanical compressor ones, is hindered due to limitations regarding ejector control modes. Indeed, ejectors are fluid-dynamics controlled devices and, because of their fixed geometry, they operate at their highest efficiency in a narrow range of operating conditions, which is in contrast with the dynamic pressure and temperature levels characterizing real applications. In this context, variable geometry ejectors (VGE) represent a promising solution to increase the flexibility and operation range of this component. The present study aims to extend the present body of knowledge regarding VGE systems, evaluating the impact of a spindle-provided ejector operated with R290 on the performance of the refrigeration system. The analysis has been carried out using an integrated lumped parameter/CFD approach, thus linking the local flow properties and global performances. Different spindle positions have been tested to assess how the different nozzle area ratios affect both the entrainment ratio and the critical pressure. Results showed that increasing primary nozzle area ratio the system can effectively reduce the thermal input, increasing the average COP at the expanse of a lower critical pressure. In conclusion, using a moving spindle control system might ensure an improvement of the ejector performance.

Visualization of Pre-Chamber Combustion and Main Chamber Jets with a Narrow Throat Pre-Chamber

<div class="section abstract"><div class="htmlview paragraph">Pre-chamber combustion (PCC) has re-emerged in recent last years as a potential solution to help to decarbonize the transport sector with its improved engine efficiency as well as providing lower emissions. Research into the combustion process inside the pre-chamber is still a challenge due to the high pressure and temperatures, the geometrical restrictions, and the short combustion durations. Some fundamental studies in constant volume combustion chambers (CVCC) at low and medium working pressures have shown the complexity of the process and the influence of high pressures on the turbulence levels. In this study, the pre-chamber combustion process was investigated by combustion visualization in an optically-accessible pre-chamber under engine relevant conditions and linked with the jet emergence inside the main chamber. The pre-chamber geometry has a narrow-throat. The total nozzle area is distributed in two six-hole rows of nozzle holes. A novel optical pre-chamber assembly was designed and tested on an optical engine, with combustion only in the pre-chamber volume, using methane (99.5% purity CH<sub>4</sub>) as fuel. A separate measurement was carried out using a metal pre-chamber assembly to study the emergence of the pre-chamber jets into the main chamber to assess the difference between the pre-chambers. The combustion process was captured using a broadband camera and pressure transducers in both chambers (pre- and main chamber). The combustion inside the pre-chamber starts at the spark location; the flame propagates along the cone and subsequently propagates fast inside the throat. The broadband combustion luminosity exhibited a non-proportional relation with the heat release rate (HRR) due to the CO<sub>2</sub>* chemiluminescence. An HSV-model (Hue Saturation Value) analysis revealed the predominance of premixed combustion during the first stage of the process, followed by infrared flame radiation. Finally, although the optical pre-chamber assembly showed a faster pressure increase, the combustion process is similar to the metal pre-chamber assembly on a mass burnt scale.</div></div>

Development of a huge hybrid 3D-printer based on fused deposition modeling (FDM) incorporated with computer numerical control (CNC) machining for industrial applications

Abstract As recent advances in additive manufacturing (AM) technology has grown rapidly over the past decades, a wide range of applications in the various field has been proposed. Especially, large-scale 3D printing technology has emerged as one of the most innovative alternatives to the traditional manufacturing process due to its simple, fast, and cost-efficient features. In this article, we proposed a large-scale hybrid manufacturing equipment of the three-dimensional (3D) printer based on fused deposition modeling (FDM) incorporated with CNC machining. Our manufacturing system is designed to produce a product having dimensions up to 3,000 mm × 4,000 mm × 1,200 mm with an extruder having an extrusion rate of 30 mm·s−1 and nozzle area of 15 mm2 × 15 mm2. We also optimized the operating conditions of our equipment including the shape of the nozzle, the temperature of the heater, and the RPM of the machining tool. The performance of the equipment was confirmed by pilot production via sand-casting. We expect that our hybrid manufacturing system can be widely used to produce various shapes of large-scale mold as a cost-effective alternative to conventional methods in the manufacturing process.

Optimisation of a hybrid NS–DSMC methodology for continuous–rarefied jet flows

The present work uses a hybrid Navier–Stokes (NS) and Direct Monte Carlo Simulation (DSMC) with a one-way coupling strategy to simulate a steady-state cold nitrogen flow expanding from a highly pressurised millimetre-sized nozzle into the vacuum. Such methodology was experienced in the context of micro-thrusters by Grabe et al. or La Torre et al.. However, it has some limitations regarding the computational cost as well as the coupling strategy that prevent its use for industrial cases. More specifically, according to common criteria, the area close to the inner nozzle exit wall is defined as a rarefied area with strong gradients and high density involving heavy DSMC computational cost. Moreover, the one-way method requires a supersonic condition at the interface between rarefied and continuous flows, which is not verified close to the nozzle wall. The present study aims to optimise the hybrid methodology by removing the inner nozzle area from the rarefied calculation and studying the influence of the continuous to rarefied flow interface definition. In order to remain as close as possible to the rarefied physics, a Maxwell wall condition is used during NS calculation as an attempt to reproduce the wall bounce on velocity and temperature that might be yielded by rarefied effects. The methodology shows good agreement with micro-thruster available data and its optimisation allows a significant computational cost decrease.

Hydrodynamic design of a circulating water channel based on a fractional-step multi-objective optimization

In this study, a multi-objective optimization of a circulating water channel (CWC) circuit was conducted to reduce the circuit's total pressure loss and limit the construction costs. The numerical optimization system was composed of an optimal Latin hypercube design (Opt LHD), a fast flexible space-filling design (FFF design), the Design Program for Wind Tunnels and Circulating Water Channels (DPWC), a support vector machine (SVM), a support vector regression (SVR), and a particle swarm optimization (PSO). To save simulation time, a simplified CWC model was proposed and verified to replace the complete CWC model. The optimization process was divided into two steps. In the first step, four design variables, including the casing's diameter, the diffuser's width ratio, the diffuser's height ratio, and the nozzle's area ratio, were selected to reshape the circuit, and an initial sample set for classification was constructed through CFD simulation. Then, a design subspace was extracted by an SVM to avoid flow separation in derivative CWCs. In the second step, a new sample set was constructed in the design subspace, and an SVR-based surrogate model was constructed based on it. Finally, the multi-objective optimization was performed within the design subspace. Optimization results showed that the CWC's total pressure loss was negatively correlated with the CWC's surface area. The optimal CWC circuit was selected from the Pareto front of two-objective optimization. Numerical results of the optimal CWC circuit showed that the total surface area increased by 7.5% while the total pressure loss significantly decreased by 19.3%, and that the residual hydrodynamic performance met the design requirements.

Evaluation of wide-range coal combustion performance of a novel down-fired combustion technology based on gas–solid two-phase flow characteristics

In order to achieve peaking carbon dioxide emissions and carbon neutrality, a variety of down-fired combustion technologies has been proposed. The existing central air supplied combustion technology (CASCT) used for burning blended bituminous coal faces some serious problems. In order to solve the problem of the wide-range coal combustion in down-fired boiler, this study proposes a novel primary air biased combustion technology (PABCT). The coal gas–solid two-phase flow characteristics and numerical simulation of combustion characteristics under the PABCT and CASCT were compared. The results indicated that compared with the CASCT, under the PABCT, the velocity attenuation in the vertical direction is slower and the airflow diffusion range is smaller below the arch. The attenuation rate of particle volume flux with the downward flow of pulverized coal is slow, and the space utilization rate of the lower furnace is high under the PABCT. The thermal numerical simulation confirms the conclusion obtained from the cold gas–solid two-phase experiment. The PABCT exhibits the characteristics of large undershoot depth of coal/air flow, low temperature in the burner nozzle area, high burnout, low NOx emissions, and slag prevention, thus making it more suitable for wide-range coal combustion from the perspective of furnace flow and combustion.

Base drag estimation in suddenly expanded supersonic flows using backpropagation genetic and recurrent neural networks

In recent years, base pressure management has gained a lot of industrial importance due to its applications in missiles and projectiles. For certain aerodynamic vehicles, the base pressure becomes a critical factor in regulating the base drag. That prompted the current work to develop input–output relationships for a suddenly expanded flow process using experiments and neural network-based forward and reverse mapping. The objective of forward mapping (FM) is to predict the responses, namely base pressure (β), base pressure with cavity (βcav), and base pressure with rib (βrib), for a known combination of flow and geometric parameters, namely Mach number (M), nozzle pressure ratio (η), area ratio (α), and length to diameter ratio (ψ). On the other hand, an effort is made to decide the optimal set of flow and geometric parameters for achieving the desired base pressure by reverse mapping (RM). Neural network-controlled backpropagation and recurrent and genetic algorithms have been employed to carry out the forward and reverse mapping trials. A batch mode of training was employed to conduct a parametric study for adjusting and optimizing the neural network parameters. Due to the requirement of massive data for batch mode training, the data required for training was achieved using the response equations developed through response surface methodology. Further, the forecasting performances of the neural network algorithms are compared with the regression models (FM) and among themselves (RM) through random test cases. The findings indicate that all evolved neural network (NN) models could make accurate predictions in both forward and reverse mappings. The results obtained would help aerodynamic engineers control various parameters and their values that affect base drag.

Investigation of Pobeda furnace bubbling zone physics using cold modeling method Part 2. Hydro-gas dynamics of liquid blowing with gas using bottom gas-protected lance

The cold flow simulation of the Pobeda furnace bubbled bath hydro-gas dynamics was performed using the bottom lance in a protective gas shell. It was shown that gas infusion into liquid at Ar = 5÷60 is carried out in pulse-coupled mode. The gas-liquid interaction area was investigated at Ar = idem for separate and joint air egress through ring and round nozzles. A two-phase zone was formed in liquid that consisted of a «leg» featuring different geometrical shape, a cavity and a gas-liquid layer over the bath surface at all considered Ar values. The most peculiar features of blowing zone formation, flame configuration and its structure depending on blow injection configuration and Ar values were found out. It was detected that ejected liquid prevails in the cavity structure at intensive blowing through the lance center and ring gap, and its content increases as gas flow rate rises in the shell, and the «leg» near the nozzle exit consists of the gas phase. An assumption was made that the presence of additional sulfide melt amount in the oxidative jet provides more complete magnetite destruction in the bath volume and protective skull formation in close proximity to the nozzle. Sizes of most indicative geometrical areas of flame were quantified, and they demonstrated periodical and extreme jet spread behavior in liquid. Empirical equations were obtained that describe the relation between maximum longitudinal and transverse «leg» sizes at dynamical conditions of blow injection into the shell (Ar shell ) and central tube (Ar center ) for two value ranges Ar shell ≥ Ar center and Ar shell ≤ Ar center . It was found that blow injection into the shell increases «leg» extension velocity on the nozzle exit up to 137 mm/s. The dependence of average splash lift height (H avg , m) above the calm bath surface was defined, which is H avg = 0.027(Ar shell + Ar center ) 0.27 within 25 ≥ Ar shell ≥ 5 and 60 ≥ Ar center ≥ 12 ranges. Schlichting equation was used to calculate the value of maximum offset from the nozzle surface where the joint axial movement of ring and round jets in liquid is maintained with equal velocities. It is assumed that the protective effect of the bottom lance with the shell appears in the lance belt area over a distance of 7–10 cm from the nozzle exit. It was noted that the cavity after separation from the nozzle moves down vertically, and the countercurrent liquid flow bounding on the cavity front moves in an opposite direction slipping the phase interface with comparable velocity. Due to more intensive changes in the interaction zone transverse size in the nozzle area and noticeable lateral liquid movement it was recommended to take corrective actions to decrease the erosive effect of melt in the Pobeda furnace lance belt at the initial jet development area.

The Hydrodynamics of Translational−Rotational Motion of Incompressible Gas Flow within the Working Space of a Vortex Heat Generator

The paper presents the results of analytical and experimental studies of the hydrodynamics of the translational−rotational motion of incompressible gas flow within a working space of a variable-geometry vortex heat generator. The terminal velocity and pressure have been identified analytically. The effect of vortex generation on the ratio of the parameters has been analyzed. A mathematical model has been developed with a simplified design scheme that simulates the movement inside a vortex channel with fixed elements. On the basis of mathematical modelling, the influence of the apparatus-constructive (AC) design of the working space of a vortex heat generator on the generation of vortices inside the apparatus has been analyzed. The influence of the main geometric and hydrodynamic parameters of the device on the indicators of its energy efficiency has been investigated. The obtained models show the critical regions where the most intense cavitation zones are possible. An analysis of the hydrodynamics of the incompressible gas motion within the working space of the newly designed vortex heat generator with variable geometry has helped define both the terminal velocity and pressure. In addition, the effect of the facility geometry on the generation of vortices favoring cavitation was determined. The model studies have been carried out in terms of liquid loading changes in the 0.001–0.01 m3/s range. The changes in a velocity field within a working channel have been analyzed for the channel geometry, where a cone angle γ is 0° to 25°, with 130, 70, and 40 mm widths for the working channel. It has been identified that a sufficient axial symmetry of the heat carrier along a vortex accelerator enables the heat carrier inlet through a turbulizing nozzle. The dependence of the nozzle area, the effect on the efficiency of the vortex heat generator angle of attack of the vortex accelerator, and the ratio of the length and diameter of the vortex zone of the heat generator to its energy efficiency in general have been defined experimentally. These studies could be instrumental in the design of vortex heat generators whose geometry corresponds to the current requirements concerning energy efficiency. It has been found that the geometry of the vortex accelerator improves the operation of the heat generator by 35% in comparison with similar available designs.