Central Nozzle Research Articles

Influence of adjacent nozzles on flow and fuel atomization characteristics of the central nozzle in a triple-nozzle combustor

This paper examined the influence of adjacent nozzles on the flow and fuel atomization characteristics of the central nozzle in a triple-nozzle model combustor. High-frequency particle imaging velocimetry testing for airflow and phase Doppler particle analyzer testing for fuel particles were employed. Under the central nozzle air intake mode, the momentum exchange between the swirling flow and the surrounding stationary air leads to a seemingly shrinking flow field. While under the triple nozzles air intake mode, the low static pressure at the geometric center between adjacent nozzles attracts the swirling flows to converge, resulting in a larger expansion angle. Confinement has a complex impact on swirling flow. When the angle of the swirling airflow is small, it guides the flow to expand. However, when the angle becomes too large, it restricts further expansion. Observed Sauter mean diameter (SMD) peaks for the tested cases lie within a similar range, suggesting comparable spray angles. Nevertheless, the triple-nozzle air intake mode exhibits consistently higher SMD values and significantly greater spray core penetration depth. Instantaneous flow characteristics deepen the understanding of these differences in atomization results. The large range of airflow oscillation under the central nozzle air intake mode allows the airflow to directly interact with the droplets. While under the triple-nozzle air intake mode, the air flow path is too far away from the spray, resulting in that most droplets do not receive sufficient aerodynamic forces for atomization.

Experimental and numerical investigations into cold flow characteristics of multiple micro-mixing jets for hydrogen-rich gas turbines

To explore the flow field of micro-mixing jets, cold flow characteristics of a model Micromix burner were investigated by particle image velocimetry (PIV) system and Large-eddy simulation (LES) model. Results show that LES results are in good agreement with experimental results. In the flow field of multiple micro-mixing jets, the jet velocities of nozzles farther away from the burner center have a high increase and decay rate. When the outlet Reynolds number increases, the Reynolds stress increases first and then decreases in the merging region indicating that the velocity fluctuation disappears in the second jet half, but it has little effect on the flow field structure. Comparing the flow fields of round multiple micro-mixing jets, the merging point and combined point in the elliptical jets flow field move backward. Moreover, the maximum velocity for elliptical jets is also faster than the round jets, which is caused by the high turbulent kinetic energy in the elliptical jet flow field. When the tube spacing increases from 2 to 3 times the tube diameter, positions of the two feature points change linearly. Further, the surrounding jets can decrease the velocity attenuation of the center nozzle and elongate the axial length of the two feature regions.

The Effect of Heterogeneous Natural Gas–Hydrogen Input Into F-Class Gas Turbine Combustor As a Combustion Optimization Method

Abstract The global push to combat climate change by transitioning to clean power generation is accelerating. One promising avenue involves using hydrogen in place of natural gas in gas turbine-based power plants. While the development of new hydrogen combustors shows potential, advancements in operational technologies are needed to ensure higher hydrogen cofiring with existing combustion systems. In our study, we propose a novel approach called heterogeneous natural gas–hydrogen input: varying hydrogen content between different nozzle groups in gas turbine combustors. Using a full-scale combustor of an F-class gas turbine model, we experimentally investigated the impact of heterogeneous hydrogen concentrations at the center and outer nozzles on combustion dynamics and emissions, comparing these with homogeneous fuel supply cases of 100% natural gas and natural gas–hydrogen mixtures. While hydrogen cofiring did not change the maximum amplitude of combustion dynamic pressure across the total frequency range, peak amplitudes in the 125–245 Hz domain were linearly proportional to the hydrogen cofiring ratio, with a 41.2% increase at 30% cofiring identified as a possible limiting factor. Our findings revealed a significant correlation between NOx emissions and combustion stability under varying levels of heterogeneity. Higher heterogeneity with intensive hydrogen input into the center nozzle improved cofiring performance, reducing the peak amplitude in the limiting frequency domain by 22% for a 25% cofiring ratio, potentially extending the critical hydrogen cofiring ratio. Implementing heterogeneous natural gas-hydrogen inputs emerges as a promising method to enhance combustion stability and enable effective hydrogen cofiring.

Passive control of thermoacoustic instability in a high-efficiency domestic gas stove with fine-tuning burner

Thermoacoustic oscillation is a significant challenge in the development of advanced thermal power and propulsion systems. The present work focuses on the whistling phenomenon in the practical burners of a developing high-efficiency domestic gas stove. The acoustic analysis is conducted by a Helmholtz acoustic solver, identifying the 1/2 wave longitudinal mode in the outer ring or center nozzle and its upstream pipe and estimating the modal eigenfrequencies fa=599Hz and fb=647Hz which are close to the main frequency of the whistling measured in experiments. The sequential flame images captured by a high-speed camera are processed by a dynamic mode decomposition method to illustrate flame structure oscillations at the peak frequency mode. The results verify that thermoacoustic oscillations are the generation mechanism of the whistling and display the periodic fluctuation characteristics of the flame and the spatial distribution of heat release. Moreover, both structural fine-tuning designs help to achieve better suppression for thermoacoustic oscillations and avoid the whistling phenomenon. These structural fine-tuning strategies have been researched for several decades but rarely reported to be applied to industrial burners in previous work. Motivated by this, it will provide a new insight into the investigation of burner structures on thermoacoustic behaviors and the application of these passive control strategies.

Particle deposition on the convergent nozzle walls of thermal-spray guns

The present study investigates particle depositions on convergent nozzle walls of (HVOF) spray guns, a process that reduces nozzle lifetime and degrades operation stability and reliability. We perform three-dimensional, two-way coupled simulations of reactive particle-laden compressible flow through a typical thermal spray gun nozzle. We determine critical radial particle velocities at which particles deposit on the wall. We characterize critical velocities concerning particle trajectories, particle diameter, and downstream location of particles deviating from the nozzle center. The critical velocity decreases with particle diameter and increases with the downstream location at which particles deviate from the nozzle center. We exclude the possibility that single particle–particle collision events create sufficient radial particle momentum for deposition. We use the gained insights to propose mitigating measures against particle depositions.

Investigation of the three-dimensional structure of low-swirl methane-hydrogen flames with multiple UV cameras-based OH* chemiluminescence tomography

Blending hydrogen with natural gas is useful for reducing CO2 emissions, but this alters the flame structure, creating challenges for flame stability. Numerous researches on methane-hydrogen flame structure have been carried out based on two-dimensional combustion diagnostic techniques such as flame chemiluminescence and planar laser-induced fluorescence. In this paper, a low-cost OH* chemiluminescence imaging system consisting of 8 ultraviolet (UV) cameras is proposed to reconstruct the three-dimensional (3D) structure of methane-hydrogen flames, and validated through use of the correlation coefficient. Further experimental investigations of the low-swirl methane-hydrogen flames are performed by this computed tomography of chemiluminescence (CTC) system. The flame properties are determined to evaluate the effects of various fractions of blended hydrogen on the flame structure, including the flame center of mass, flame surface density and fractal dimension. Results showed that the flame initially has bowl-shape structure. The flame height gradually decreases and the flame cross-sectional area increases as the blended hydrogen fraction increases. Meanwhile, the bottom of the flame moves toward the nozzle outlet. Nevertheless, when the blended hydrogen fraction reaches 50%, the flame transforms into a cup-shaped flame and shows a double-layer flame structure. When the flame is bowl-shaped, the flame center of mass moves away from the nozzle center axis with increasing blended hydrogen fraction, but the fractal dimension and flame surface density are not sensitive to the blended hydrogen fraction. In contrast, when the flame is cup-shaped, the flame center of mass moves towards the nozzle center axis, and the flame surface density and fractal dimension increase significantly, indicating the increase of flame wrinkling. These results reveal that blending hydrogen leads to two distinct flame structures and characteristics in low-swirl flame, also demonstrate that the proposed 3D low-cost CTC system based on multiple UV cameras is well-suited for combustion diagnostics.

Experimental Study on Double Jet Flames with Different Nozzle Diameters

Double jet flames are commonly observed in the energy industry. A facility consisting of a double jet flames apparatus, was designed to experimentally simulate the interaction of double jet fires with different spaces and nozzle diameters. It has been found that the exit momentum, nozzle diameters and nozzle spacing significantly affect the flame behavior. The experimental results show that the flame merging probability (Pm) of double jet fires with different nozzle diameters can be fitted with dimensionless parameters that couple the Froude number(Fr) and the distance between fire sources. Additionally, it has been observed that the difference in height between the two flames can be used as a parameter to determine the correlation between flame height and the distance to the nozzle center.

Rozwiązanie problemu tworzenia się zatorów w rurociągach podczas transportu gazu poprzez proces automatycznego strumieniowania

The article presents the application of autoejection process to ensure efficient operation of pipeline systems and gas separation installations when it is impossible to remove and utilize the condensate from the pipelines. Thus, in the suggested ejector, a single common stream is separated into two streams, i.e., an active and a passive stream, as opposed to two separate independent streams in existing ejection devices. As a result, we refer to such an ejection process as autoejection, or a self-ejection process. Such a procedure is run in the pipeline with the goal of blowing and dusting the liquid phase through the central high-velocity nozzle in circumstances of mass blocking and coating rather than expelling the liquid from the pipes. On the cross-sectional area of the belts, the velocity profiles of flows in laminar and turbulent regimes are known to differ greatly from one another. The adhesion forces acting from the tube's central axis outwards, towards its walls cause the flow rate to decrease. There is a cross-sectional interaction of flows in this mode, according to experimental studies of turbulent flows. As a result, compared to the laminar domain, the flow velocities in this regime are more equally distributed across the cross-section of the flow, and their values are roughly equal to the flow's average value. In this case, based on the dependences of the flow ∆p = f(W), it is known from the calculations and the table that at such velocity limits of the flows, the “braking” pressure (p0) of the liquid coating on the pipe walls corresponds to the maximum velocity of the central gas flow. The autoejection process can occur due to the difference between the static pressures. Unsaturated absorbent coatings can be blasted off the tube absorber's walls using this technique and blended back into the main gas stream. Gas-liquid autoejectors installed along the pipe absorber's length make it possible to use this method. The purpose and principles of autoejectors’ operation are considered and a perspective of their application in tube absorbers is noted.

Stress concentration factor based design curves for cylinder-cylinder connections in pressure vessels

The results of the parametric analysis of the cylinder-cylinder intersections in pressure vessels, performed in both elastic and plastic regions, are discussed in this study. Besides, the outcomes that contribute to the development of classical solutions in the literature are addressed as design curves depending on stress concentration factors (SCF). To begin with, the maximum stresses for cylinder-cylinder connections were calculated by finite element analysis and SCF values were obtained. In these calculations, external local loads acting on the nozzle centre and internal pressure are the main variables for loading conditions. Following that, different parametric approaches and loading conditions are presented to develop design curves for cylinder/cylinder connections by changing the main geometric parameters, such as cylinder and nozzle radii, and their thicknesses. A new approach is presented using these new curves thus allowing industrial designers to calculate maximum nozzle stresses without the need to undertake a thorough finite element analysis.

Numerical study of flame characteristics in a reduced-diameter vortex combustor

In this paper, the combustion process in a vortex combustor, which is composed of two volutes, a center nozzle, and a reduced-diameter cavity, is studied by CFD simulation. The combined effect of the center jet and cyclone vortex on the flame structure is revealed by analyzing the fuel transport mechanism and flow field characteristics. Results show that under different fuel and air supply conditions, two typical flame structures may form inside the combustor. When the equivalence ratio is 0.5 and the power is 40 kW and 50 kW, Flame A will be produced, which is mainly distributed near the center nozzle. Under other conditions, Flame B will be generated, which is a two-layer structure with an inner layer surrounding the center nozzle and an outer layer near the wall. The construction of Flame B inside the reduced diameter vortex combustor is mainly attributed to the strong cyclonic flow, which breaks the recirculation in the flow field, transporting the fuel to the near wall region and promoting secondary combustion. At this time, the methane burn rate can be as high as 99 %, which is 10 % higher than the methane burn rate of Flame A.

Simulation of gas dynamics of oxygen flow and hydrodynamics of cooling water flow in tuyere tips with tangential optimized nozzles and results of their pilot tests.

The blowing mode largely determines the technical and economic indicators of BOF smelting, which was confirmed during the technological audit of the BOF shop of Azovstal Iron and Steel Works, carried out in 2021. It was found that the blowing mode of the process using an oxygen lance of the basic design was noticeably shifted from the optimal one in the direction of “hard” blowing. In a significant number of melts this led to an increase in the specific consumption of metal sheets, deterioration of lime assimilation by slag, dephosphorization and desulphurization of the metal. Taking into account that adjustment of the blowing mode by changing the working height of blowing and oxygen consumption did not provide a stable positive result, changes were made in the design of the tuyere tip. The design of the head with tangential arrangement of nozzles is proposed to “soften” the blowing of melts. The advantages and dis-advantages of oxygen lances of this type are considered. Numerical modeling of the gas dynamics of the oxygen flow and the hydrodynamics of the flow of cooling water in a tip with a tangential arrangement of nozzles has been per-formed. On the basis of simulation results, two variants of an improved design of the tips of 350-t LD converters with five (variant 1) and four (variant 2) main peripheral tangentially oriented nozzles and a central nozzle of lower throughput were developed to use them mainly in the second and first periods of the campaign according to the lining of the converters, respectively. It is shown that the design parameters of the nozzle blocks provide an oxygen jet outflow regime close to the design one in the main range of oxygen operating flow rates and a “non-separated” outflow regime with a decrease in the off-design ratio down to 0.8. The design parameters of the cooling system provide both an acceptable loss of water pressure in the head (0.9 MPa), the absence of local low-speed vortex zones of water, and a fairly high average coolant flow rate along the most heat-stressed (the lower) surface of the tip (about 4.5 m/s). As a result of industrial testing of a pilot batch of experimental heads with five main peripheral tangentially oriented nozzles, manufactured at the plant’s own repair and mechanical base, an increase in the resistance of copper tips was found to be 1.2 times, the resistance of lances to removal for cleaning from accretion was found to be 6.8 times, reduction in the specific consumption of metal charge by 0.9–5.6 kg/t, an increase in the dephosphorization and desulfurization coefficients of metal in the converter by 0.7–1.5 and 1.3–3.2%, respectively.

Hydrogen Jet Flame Control by Global Mode

In this study, we employ the potential of the global instability phenomenon to qualitatively alter the dynamics of a turbulent flame. We adopt the large eddy simulation method and an in-house numerical code. For the combustion process we do not include explicit sub-filter modeling. The accuracy of this ‘no combustion model’ approach is verified by comparison against the Eulerian Stochastic Fields method. We include several test cases representing different flow regimes, including convective and absolutely unstable conditions. The focus is on a counter-current configuration, which includes a central jet nozzle supplying hydrogen fuel surrounded by a somewhat larger co-axial nozzle sucking fluid from the surroundings of the central nozzle. The suction generates a counterflow where global instability is found to be triggered if sufficiently strong suction is applied. The critical suction value IGI\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_{GI}$$\\end{document} is larger if the level of the inlet turbulence intensity Ti\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_i$$\\end{document} is increased. Depending on the suction strength, the flame quickly stabilizes, either as being attached to the nozzle or as a lifted flame hovering at a height of a few fuel nozzle diameters. Additionally, it is shown that increasing Ti\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_i$$\\end{document} can assist an initially lifted flame to attach to the nozzle. Flame lifting is the result of self-induced strong toroidal vortices that lead to leaner combustion conditions of the mixture upstream of the flame base. The toroidal vortices prevent upstream flame propagation and lead to a very intense mixing process that gives rise to the lifted reaction zone. This ensures almost complete fuel combustion at a short distance from the inlet. On the contrary, when the suction strength is below IGI\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_{GI}$$\\end{document}, the flames are attached and a high temperature near the fuel inlet causes an increase in molecular viscosity. This tends to laminarize the mixing layer between the fuel and oxidizer. The flames appear as if they were laminar and non-premixed over a long distance from the inlet. In such a situation, a significant amount of fuel remains unburned.

Structural design and flow field characteristics analysis of a new spin-on multi-hole jet drill bit for radial horizontal wells

In order to improve the rock breaking and drilling capacity of the jet bit in radial drilling, a new spin-type multi-hole jet bit was designed. The RNG K-ε turbulence model is used to analyze the flow characteristics of the internal and external flow fields of the designed jet bit, and the influence of the rotational speed and nozzle distribution on the flow field characteristics of the jet bit is analyzed to provide a basis for the design and structural parameter optimisation of the jet bit in radial horizontal wells. The results show that the internal flow field of the jet bit can be divided into four zones: the forward jet zone, the bottomhole overflow zone, the reverse overflow zone and the low-speed reverse flow zone. The reverse jet consists of six straight jets uniformly distributed along the circumferential direction and arranged at equal angles around the axis of the rotating body in the flow field. The reverse jet also impinges on the well wall to form an overflow zone, which provides self-propulsion and acts as a reaming agent. As the injection distance increases, the axial velocity rapidly decreases to zero and the decay velocity of the three groups of jets gradually approaches at the impact wall. Rotational speed has an effect on the decay of the flow velocity at the centre of the forward jet axis. When the angle of inclination is very small, the rotational speed has almost no effect on the decay of the axial velocity of the jet. The greater the angle of inclination, the greater the linear angular velocity at the jet exit, the more the jet mixes with the surrounding crossflow, the faster the dissipation of jet energy and the faster the jet decays along the axis. Controlling the magnitude of the rotational speed has to be taken into account in the design. Initially, the optimum values of the different structural parameters were determined as the central nozzle coinciding with the drill axis, the central forward nozzle deflection angle of 20°, the external nozzle deflection angle of 20° and the external nozzle tension angle of 15°.

MODELLING THE PROCESS OF OXIDISING IMPURITIES IN A METAL BATH USING COHERENT NOZZLES

The main task of the oxygen-converter process is to produce a liquid metal semi-product with specified properties. It is directly related to the optimization of the blowing mode and devices responsible for the process and technical and economic parameters of melting. The effectiveness of the organization of the process of introducing oxygen into the melt, and, accordingly, assimilation by the metal bath basically depends on the design of the lance nozzles. In electrometallurgy, coherent nozzles are used to improve bath mixing performance and activate processes (a central nozzle for supplying oxygen and a peripheral one surrounding it for supplying gas as a fuel that forms an enveloping flame). Therefore, the authors conducted a study of the influence of coherent top nozzles on the oxidation of impurities in the metal bath under the conditions of the use for the oxygen-converter process (with oxygen supplied to both parts of the nozzle). A high-temperature simulation of the oxidation process of Si from hot metal was carried out by using a Cu-Zn melt (1%) when comparing blowing through a nozzle of a coherent type with a peripheral part of 75% and a conventional nozzle of the equivalent diameter.

Simulation and Analysis of the Influence of Sounding Rocket Outgassing on In-Situ Atmospheric Detection

The Meridian Project’s sounding rocket mission uses a mass spectrometer to conduct in-situ atmospheric detection. In order to assess the influence of surface material outgassing and the attitude control jet on the spectrometer’s detection, a sounding rocket platform was modeled and simulated. Using the physical field simulation software COMSOL and the Monte Carlo method, this study investigated whether the gas molecules from the two cases could enter the in-situ atmospheric mass spectrometer’s sensor sampling port after colliding with the background atmosphere. The simulation results show that the influence of surface material outgassing on the in-situ atmospheric detection is very small, even under the conditions of medium solar activity and medium geomagnetic activity, while the influence of the attitude control jet on the in-situ atmospheric detection is large but can be reduced by reducing the low-altitude attitude control operation and decreasing the transmission probability. Through simulation optimization and according to engineering needs, increasing the nozzle outlet cross-sectional area, increasing the temperature of the gas used for attitude control, increasing the nozzle rotation angle, increasing the nozzle outlet angle, or increasing the nozzle center height can reduce the transmission probability. This model can simulate and analyze the influence of both surface material outgassing and attitude control jets on in-situ atmospheric detection, optimize relevant parameters, and provide new ideas for relevant work.

A new method for regulating Pelton turbine based on ejection of discharged flow

Hydropower plants (HPPs) contribute a significant share of Russia’s electricity generation. With the prospects of developing this sector and harnessing the hydroenergy potential, it is necessary to consider methods for modernizing hydroelectric installations. This article examines a new method for regulating active (Pelton) turbines based on modifying the nozzle flow rate through the ejection of spent liquid from the runner using a jet pump. The relevance of this solution lies in the potential to increase the operational duration of high-head pumped-storage hydropower plants (PSHPPs) and improve reliability by eliminating or reducing the intensity of operation of the regulating needle in the guide apparatus. Various structural configurations for incorporating the jet pump into the hydrosystem of HPPs/PSHPPs with Pelton hydro turbines are discussed. Parallel and series configurations offer specific advantages and disadvantages. A methodology for determining the expression to calculate the parameters of the injecting device, depending on the turbine’s characteristics, is presented based on a mathematical model of the jet pump with a central nozzle.

Double coaxial pipe jet control using DBD-PA and bluff body

In this study, a double-tube burner nozzle with a DBD-PA (dielectric barrier discharge plasma actuator) and flame holder was employed to regulate the lifted flame. The flame holder held the lifted flame and the DBD-PA regulated the lifted flame to suppress the lifted flame’s vertical oscillation. To form a lifted flame, pseudo-biogas, a mixture of CH4 and CO2 in the ratio of 6:4, was jetted out through an inner nozzle and air through an annular nozzle. To control the air jet and prevent the lifted flame’s vertical oscillation, the DBD-PA was installed inside an annular nozzle. The DBD-PA was driven intermittently at regular intervals to produce a tangential flow in the same direction as the jetting gas, and the flame holder was placed above the nozzle outlet on the nozzle center axis. The finding indicated that by driving the DBD-PA at the slightly lower frequency than the frequency of the naturally shedding vortices in the free jet, the lifted flame’s vertical oscillation can be reduced by collapsing the jet’s vortex ring at a steady position and with a steady cycle. By impeding the lifted flame’s vertical oscillation, it is forecasted to reduce the blowout of the lifted flame and combustion noise.

STUDY OF THE PHYSICAL CHARACTERISTICS OF STREAMS EMERGING FROM COHERENT-TYPE NOZZLES

The main controlling factor in oxygen converting with top blowing is the stream of oxygen, which penetrate the metal bath and promotes the flow of heat, mass exchange and chemical processes. The inherent characteristics of the oxygen jet are created by the nozzle tip with nozzles that may differ in design depending on the issue they solve.
 In the electrometallurgical industry, coherent nozzles consisting of a central nozzle for supplying the main oxygen jet and a surrounding annular nozzle for supplying shielding gas, mainly methane, are used to ensure deep penetration of the oxygen jet into the melt and to improve the mixing processes of the bath. This design of the nozzle, according to available published data, ensures the elongation of the main jet while preserving its momentum.
 The paper presents the results of a study using a modified liquid manometer of the features of the action of jets flowing out of nozzles of a coherent type of different designs (the ratio of the outer and central parts of 25%, 50% and 75%) under blowing conditions that correspond to the conditions of top blowing during industrial oxygen conversion. The conducted research made it possible to establish that when the share of the peripheral part is more than 50%, the main controlling link of the jet is the central nozzle, and when the share is smaller, it is the peripheral slotted part. The jets flowing out of the nozzles of the coherent type with the share of the peripheral part more than 50% have a greater force of action on the liquid compared to the force of action of the corresponding central nozzle, by the amount from 33 to 74%relatively. The design of nozzles with a share of the peripheral part of the order of 25% practically does not create conditions for improving the power characteristics of the jet.
 According to the results of the established conclusions, it is possible to recommend the use of nozzles of the coherent type with a share of the peripheral part of more than 50% as nozzles, for example, of the second row for top blowing lance, which have a slag-forming effect, contributing to better penetration into the melt compared to the corresponding cylindrical ones, that will intensify the processes of mixing and slag formation in the bath

A Modified Calculation Method for a Centered Water Nozzle Steam–Water Injector

A centered water nozzle steam–water injector is driven by cold water to pump steam at a low pressure and to produce a high outlet water pressure. It can be used as a safety pump in a light water reactor to inject cooling water into the reactor core with no power supply in case of an accident. In this study, a modified calculation method for a centered water nozzle steam–water injector is proposed and verified by experimental data in the literature. The calculation method consists of a water nozzle model, a steam nozzle model, a mixing section model, and a shock wave model. Comparisons between the calculated results and the experimental results under different inlet steam pressures, inlet water pressures, and back pressures are conducted, and the calculated results show good agreement with the experimental results. The calculated results with different back pressures show that no shock wave occurs in the mixing section when the back pressure is small, but with the back pressure increasing, the pressure undergoes a dramatic increase in the throat tube, and the shock wave position moves towards the inlet of the mixing section. Due to the complexity of shock wave characteristics, it is necessary to conduct a more in-depth study of shock wave characteristics in the mixing section to determine more detailed boundary conditions for shock wave generation.

Study on hydrodynamic characteristics of the liquid-solid circulating fluidized bed with a central pulsating nozzle by numerical approach

• A novel LSCFB with a central pulsating nozzle is proposed. • Hydrodynamics of the riser was studied by three-dimensional numerical simulation. • With the central pulsating flow, the radial interphase mixing degree is enhanced. • Regression formulas of the axial and radial slip velocities are obtained. Pulsating fluidization is gaining increasing attention due to its superiority in efficiency improvement. A novel type of liquid–solid circulating fluidized bed with a central pulsating nozzle was proposed to improve the reaction efficiency in this work. Based on Eulerian-Eulerian two-fluid model and the kinetic theory of granular flow, the hydrodynamic characteristics in the riser was investigated by three-dimensional numerical simulation. The effects of pulsating liquid flow and particle properties on the distributions of solids holdup, the radial velocity of the particles, the slip velocity and the radial mixing degree were studied. The simulation results showed that with the addition of the central pulsating liquid flow, the particles displayed apparent radial motion, and the interphase mixing degree as well as the interphase mass transfer efficiency were enhanced. Based on the numerical results, the regression formulas of the axial and radial slip velocities were obtained respectively.