Bottom Nozzle Research Articles

Stabilized, flat iron flames on a hot counterflow burner

Metal powder combustion has traditionally been studied to mitigate the risk of industrial accidents and to determine the contributions of metals as additives to the performance of energetic materials. Recently, there has been growing interest in exploring the potential of metal powders as recyclable, zero-carbon energy carriers as an alternative to the hydrocarbons known to contribute to climate change. The present work introduces, for the first time, a stabilized flat iron flame. The counterflow burner used in this work is comprised of an inverted ceramic nozzle which sits above, and is aligned axially with, a lower nozzle producing a laminar flow of particles suspended in an oxidizing gas. A stabilized methane flame sits inside the top nozzle and the hot combustion products impinge upon the two-phase flow from the bottom nozzle, creating a stagnation plane. Spherical iron powder, with 90% of the particles less than 2.5 µm in size, is pre-loaded into a piston and dispersed using mixtures of 30% and 40% oxygen balanced in argon. Flame speeds are measured using particle image velocimetry (PIV), while flame temperatures are determined using multicolour pyrometry. It is found that flame speeds range between 30 cm/s and 45 cm/s for both oxidizing mixtures. Despite having fuel loadings below stoichiometric concentrations, the observed particle combustion temperatures are close to the adiabatic flame temperature of the stoichiometric mixture, indicating combustion in the diffusion-controlled regime for these small particles. Finally, the independence of the flame speeds with respect to oxygen concentration suggests flame propagation in the discrete regime.

Physiochemical and thermal properties of silica Aerogel–Poly vinyl alcohol / Core–Shell structure prepared using fluidized bed coating process for thermal insulation applications

This work proposes a process for the fabrication of a silica aerogel (SA)–polyvinyl alcohol (PVA) core–shell structure using the fluidized bed method. First, nearly spherical hydrophobic SA particles with a diameter between 0.5 mm and 3.0 mm were prepared from rice husk ash via a sodium silicate route and ambient-pressure drying. Subsequently, a specific batch size of the SA particles was suspended in a heated air stream and sprayed with aqueous PVA using a bottom nozzle via the fluidized bed process. Coating of an individual SA particle is possible for large particle sizes and hydrophobization of the SA surface prevents penetration of PVA into its pores. The core–shell structured material showed a combination of high thermal insulation and good mechanical stability, rendering it suitable for use as filler in polymer resin, paints, and coatings. The core–shell structured material had an average density of 0.09 g cm−3 with well-preserved SA pores. The average shell volume fraction was 2.5%; the shell thickness varied below 50 μm, and was mostly approximately 20 ± 5 μm. Thermal analysis using transient plane hot-disk method and thermogravimetric analysis showed that the SA–PVA/core–shell structure exhibited lower thermal conductivity (0.035 W/mK) and higher thermal stability than uncoated SA.

Virtual reality development and simulation of BMI nozzle inspection system for use during regular refueling outage of APR1400 family of reactors

Reactor vessel bottom mount instrumentation nozzle is J-groove welded to reactor vessel inside. This location has shown leaks in some NPPs in the past such as pinhole leaks at the South Texas Project in 2003 and a similar trace of leak at Palo Verde Unit 3 in 2013. Inspection of reactor vessel bottom mounted instrumentation nozzle weld crack requires removal of reactor internals in the case of APR1400 family of reactors without special tools. In Korea, the removal of reactor internals is prohibited during regular refueling outage following regulatory guidelines, hence the inspection of defects in reactor vessel bottom mounted instrumentation nozzle from inside of reactor vessel has not been performed during a regular refueling outage. In this study, a remote weld inspection system for reactor vessel bottom mounted instrumentation nozzles is developed in a virtual environment, and the operation of the inspection system was simulated to prove the validity of the system. The aim of the reactor vessel bottom mounted instrumentation nozzle inspection system was to inspect reactor vessel bottom mounted instrumentation nozzle during regular refueling outage without removing RI. This allows inspection of reactor vessel bottom mounted instrumentation nozzle weld for every refueling outage and allows finding defect at an early stage of defect formation and prevent reactor vessel crack caused by primary water stress corrosion cracking which lead to the bottom mounted instrumentation nozzle leak.

Numerical and experimental studies of aggregate blocking in mortar extrusion

Numerical and experimental study of aggregate blocking in extrusion of mortar is presented. The studied system consists of a pipe with a nozzle at the tip. Fresh mortar is modeled by composite particles consisting of hard-core representing a sand particle surrounded by soft-shell layer representing interstitial cement paste. For the experimental study, two kinds of mortars are studied. The first kind is a mortar composed of monosized glass beads. This mortar is used for comparison with numerical results. The second kind of mortar is more realistic, polydispersed particles are used by replacing glass beads by standard sand. The effects of the dimension of the bottom nozzle opening, the rheological properties of the cement paste and the paste volume proportion on the blocking of mortar are studied both experimentally and numerically. For mortars composed of monosized beads, experiments and simulations both show that the main parameter governing aggregate blocking is the ratio ‘a’ between the bottom opening diameter of the nozzle and the beads diameter. Rheological properties of the paste and paste volume proportion are less influential. Experimental results obtained on both kinds of mortar confirm the limit ratio ‘a’ identified numerically in all the cases, except for the lower cement paste volume proportion (0.54 in our study) for which ‘a’ has to be slightly increased to avoid blocking.

Experimental study on slag splashing of an 80 t combined blown converter

Physical modelling of slag splashing practice of an 80 t combined blown converter was conducted in this paper. Through measuring the mass flux of splashed slag, the effect of different operating parameters on slag splashing was investigated. By means of variance analysis, the influence significance of different operating parameters on slag splashing was obtained, and the optimal combination of operating parameters were acquired as follows: lance height 600 mm, top gas flowrate 18000 Nm3 h−1, four nozzles lance, bottom nozzle configuration D4, bottom gas flowrate 100 Nm3 h−1, and amount of remained slag 10%. In addition, the relation between the agitation energy of top blow and mass flux of splashed slag was discussed, and the estimation model for mass flux of splashed slag during BOF slag splashing practice was proposed through data analysis.

Acoustic emission monitoring during hydrotesting of a mounded LPG storage vessel of petrochemical industry

One mounded LPG storage vessel of petrochemical plant got suddenly exposed to cryogenic nitrogenand developed cracks in the shell plate adjacent to the bottom nozzle and was subsequently repair welded.The structural integrity of the repair weld region was assessed by NDT examinations. The integrity of there paired weld region was conrmed by conducting hydrotest. Acoustic emission (AE) monitoring during thehydrotest was also carried out. The acoustic emission signals generated during the hydrotest indicated thatthe signals were due to structural noise and microyielding of the vessel material. During the repressurizingcycle of the hydrotest, negligible AE signals were generated and this conrmed the structural integrity of therepair welded region of the vessel monitored by acoustic emission technique (AET).

Distribution of Liquid Flow Rates in the Process of Bubbling with Gas Through Gas-Permeable Inserts

The authors studied the distribution of the vertical components of the rate in the ascending gas-liquid flow when blowing through the bottom nozzle at two levels under three modes of neutral gas supply. It was estimated that under the intensities of gas (nitrogen) of 2 and 4 L/min-t the type of rates distribution in both cross-sections does not differ from the generally accepted one and practically does not depend upon the intensity of gas supply.

Formation of a cool diffusion flame and its characteristics

Low-temperature (∼700 K) “cool” flames formed with n-heptane fuel were observed in the experiments conducted under microgravity. Recently, Won et al. demonstrated experimentally that such “cool” flames could be established under normal gravity. However, as ozone was added to air for supporting the flames in that experiment, the fundamental question on the formation of a self-supported n-heptane/air “cool” flame remained unanswered. A numerical investigation is conducted for (1) finding an answer to this question and (2) determining a procedure for establishing a “cool” flame. A standard opposing-jet burner is considered. Investigations are performed using a well-tested CFD code. A reduced mechanism that successfully captured the “cool” flames in microgravity is used. Calculations have demonstrated that a “cool” diffusion flame can be established with n-heptane under normal gravity without resorting to flame-speed promoters such as ozone, pressure or temperature. Using velocities of 4 and 7 cm/s and temperatures of 400 and 300 K for the fuel and air jets, respectively, a stable “cool” flame was obtained. Flame was ignited through increasing the temperature of the air jet to a value >724 K and then a self-sustained “cool” flame was obtained by decreasing the temperature back to 300 K. Parametric studies are performed on the applied gravitational force such that the heavy n-heptane flowed upward from the bottom nozzle or downward from the top nozzle. In general, flame remained flat with or without the gravity. However, when the fuel jet was at the bottom, it expanded faster and moved the flame closer to the fuel nozzle. “Cool” flame could not be stabilized for the same velocity and temperature conditions when fuel flowed from the top. “Cool” and normal diffusion flames obtained with identical flow conditions are compared. Limiting stretch rate for extinguishing the “cool” flame is determined.

Experimental research on performance parameters of a self-excited pulsed jet device

The self-excited pulsed jet is characteristically efficient and inexpensive. To develop an optimal pulsed jet, the structural and operating parameters affecting its peak hitting power were studied. The optimal range of cavity length and diameter, the areal ratio of the bottom and top nozzles, the bottom nozzle length, and the target distance and working pressure were all determined.

Agglomeration in counter-current spray drying towers. Part B: Interaction between multiple spraying levels

A new experimental method is developed here to investigate agglomeration in spray drying towers operating with multiple nozzles. It allows studying independently the contribution of each spray to the product and obtaining a valuable insight into the agglomeration processes. The paper studies a two level swirl counter-current dryer of detergent in a full-scale production system. It shows that operation with two nozzle levels increases the energy efficiency compared to the use of single sprays, but in turn promotes both agglomeration and elutriation of powder from the top of the dryer. The product size distribution becomes bi-modal and the composition and porosity of the product more heterogeneous due to the different thermal histories experienced by droplets from each spray. The method described here controls the air temperature and humidity nearby the nozzles to quantify the agglomerates resulting from particle contacts within each individual spray or from their interaction. Particle agglomeration is shown to be suppressed at the bottom of the dryer where the heat transfer rates are highest and promoted at the top spray, which originates a second coarse mode in the size distribution. Both levels do not operate independently; the powder elutriated upwards from the bottom nozzle is captured entirely by the top spray when it is centrally located. By isolating the independent impact of each nozzle in a dryer, the method provides powerful data to correlate the agglomeration behaviour with local process conditions, and so facilitate the development and validation of spray dryer models.

Numerical Simulation of an Argon Stirred Ladle with Top and Bottom Injection

The stirring of a molten steel ladle with argon injection through a top submerged lance and a bottom nozzle is numerically studied here through Computational Fluid Dynamics (CFD) simulations. Three lance submergence depths and three injection velocities are considered in the CFD numerical experiments. The turbulent dissipation rate is employed to characterize the stirring phenomenon. The mixing times are determined from the gas flow rate, ladle geometry and bath depth using an empirical correlation.

Critical Compressive Forces and the Modes of the Loss of Stability in the Instrumentation Tube Guides of the Fuel Assemblies of Nuclear Reactors WWER-1000

Consideration is given to the strain stability at axial compression of the tubular instrumentation tube guide connecting the top nozzle and the bottom nozzle of the fuel assembly of the nuclear reactor WWER-1000. The influence of the grip conditions of the edges of the instrumentation tube guide on the values of critical compressive forces and stresses and also on the shape of the bend at the stability loss has been studied. The changes in the compressive stress and force conditioned by the stochastic nature of the change in the parameters during the operation of the fuel assemblies of nuclear reactors can be comparable with the obtained relatively low critical values of 1.8 to 7.5 MPa of the compressive stress and the values of 6 to 24 kgf (kilogram-force) of the compressive force at which the bending of instrumentation tube guides is possible due to the loss of stability. Due to the insignificant minimum value and the difference between different values of the critical compressive force answering the loss of stability of the guide channel like a long compressed rod it is quite possible that the shape of the instrumentation tube guide bent due to the loss of stability during the operation will have several inflection points that will considerably hamper the motion of the regulating elements of the reactor protection and control system. Due to this fact it is reasonable to develop design diagrams that allow for the determination of critical compressive forces and axial stresses in the instrumentation tube guides taking into consideration their interaction with the top nozzle and the bottom nozzle and the spacer grid of the fuel assembly and this problem requires additional studies.

Heat Transfer Characteristics from Single Group Slot Jet Impingement on the Strip Surface for the Hot Rolling Ultra-Fast Cooling

As for the impinging jets of single group slot nozzles, the heat transfer of the top and bottom strip surface is uneven which is mainly caused by the various jet distances of the top and bottom nozzle to the strip surface and the effect of gravity. In this study, the convective heat transfer process of the top and bottom strip surface due to single group slot nozzles in the ultra-fast cooling (UFC) system was studied by the fluid-structure interaction finite element method. The distributions of the flow field and heat transfer for the top and bottom strip surfaces were obtained under the various parameters. The results showed that, the difference value of the average Nusselt numbe for the top and bottom strip surface was decreased with the increase of the jet velocity, but when the jet velocity was up to 5m/s it remained almost the same. The uniformity of the top and bottom surface was improved by the jet impingement height (h) for the h<45mm. It was found that for h=25mm, the heat transfers of the top and down surfaces were more evenly, and the different value of average Nusselt number for the decreased by about 12.6%-28% as the jet impingement height increased from 25mm to 45mm when the slot width was 5mm.

Slag Splashing in a Basic Oxygen Furnace under Different Blowing Conditions

The influence of three different blowing conditions on the slag splashing process in a basic oxygen furnace for steelmaking is analyzed here using two-dimensional transient Computational Fluid Dynamics simulations. Four blowing conditions are considered in the computer runs: top blowing, combined blowing using just a bottom centered nozzle, combined blowing using two bottom lateral nozzles, and full combined blowing using the three top and the three bottom nozzles. Computer simulations show that full combined blowing provides greater slag splashing than conventional top blowing.

Investigation of Bulging Behavior of Coke Drum—A Practical Analysis of Bulging Under Complex Quench Conditions

Coke drums undergo cyclic operations typically in the temperature range from room temperature to about 500 °C (930 °F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is uneven during quenching, and can vary in each cycle of the quenching operation. Such a complicated thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging and/or cracking. The authors have investigated the bulging behavior of the coke drum by the thermal elastic-plastic finite element (FE)-analysis, considering the existence of the overmatch welds and uneven temperature field during quenching (Ohata et al., 2011, “Investigation of Bulging Behavior of Coke Drum—Feasible Study on Causes of Bulging,” ASME PVP2011-57276, Baltimore). In this paper, a practical FE-analysis is developed to estimate the complex strain that leads to bulging under uneven temperature fields during quenching. The actual temperature and strain data during operation are collected by thermocouples and high temperature strain gauges. A thermal analysis model, including an evaluation of boiling heat transfer on the shell's inner surface, is established to simulate the measured shell behavior of the coke drum. By utilizing this FE-analysis model, several parameters thought of as causal factors in bulging can be examined under the uneven temperature profile that is likely to occur during actual operation. This analytical approach can also provide effective technique for improvements in shell durability.

Investigation of Bulging Behavior of Coke Drum: Feasible Study on Causes of Bulging

Coke drums undergo cyclic operations typically in the temperature range from ambient temperature to about 500 °C (930 °F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is no more uneven in quenching, and can vary in each cycle of quenching operation. Such complicate thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging or cracking. This study makes investigations into the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis. In this work, a feasible study is conducted on potential causes of bulging. As factors inducing a heterogeneous plasticity in the shell structure of the coke drum, the strength overmatch of welds and the uneven temperature field in quenching as well as quenching conditions are focused. The analytical result shows that strength overmatch in girth seam welds can be one of the causes of plastic distortion under one operating cycle. The lower rising rate of cooling source can induce plastic straining over the whole shell wall, which tends to induce more remarkable plastic distortion.

원자로 내부 구조물 형상 처리 방법이 축소 APR+ 유동분포 예측 정확도에 미치는 영향에 관한 수치적 연구

원자로 노심 입구에 위치한 내부 구조물들은 형상 및 노심 입구까지의 상대적 거리에 따라 노심 입구유량분포에 상당한 영향을 미칠 수 있다. 본 연구에서는 원자로 내부 구조물 형상 처리 방법이 축소 APR+ 유동분포 예측 정확도에 미치는 영향을 조사하기 위해 상용 전산유체역학 소프트웨어인 ANSYS CFX R.14를 사용하여 원자로 내부 구조물들의 실제 형상을 고려한 계산을 수행하였고 다공성 매질 가정을 적용한 계산 결과와 비교하였다. 결론적으로 노심 입구 상류에 위치한 원자로 내부 구조물의 실제 형상을 고려함으로써 노심 입구 유량 분포를 더 정확하게 예측할 수 있었다. 따라서 충분한 계산 자원이 확보된 조건인 경우라면 정확한 노심 입구 유량분포를 계산하기 위해 노심 입구 상류에 위치한 원자로 내부 구조물들(예: 하부지지구조물 바닥판 및 노내 계측기 노즐 지지판)의 실제 형상을 고려해서 계산하는 것이 필요하다.

FE Analysis of Hot Strips’ Temperature Distribution in Laminar Cooling Process

The temperature distribution of the hot-rolled strip in the ROT cooling process was calculated and analyzed using ABAQUS in this paper. The complicated heat transfer coefficients of hot strip considering the position effects of top and bottom nozzles, and the non-uniform heat transfer situation along the width direction were defined by user subroutine. The simulation results were in good correlation with test results. It’s helpful for further analysis to improve the temperature distribution uniformity and the simulation accuracy for FE model, and guide the on-site production.

Study and Application of Bottom Blowing Technique of Combined Blowing Converter

The water modelling experiments of 300 t converter concerning combined blowing parameters, the number, and configuration of bottom nozzles are carried out. The results show that the arrangement of 16 bottom nozzles at 0. 40D and 0. 45D (hearth diameter) concentric circles is the reasonable solution. The combined blowing steelmaking technique of 300 t converter has been developed through experiments and studies relating to optimizing the top-bottom combined blowing pattern, the number and configuration of the bottom nozzles, the type selection of bottom nozzle, and bottom nozzle maintenance techniques. The results show that the product of w[c] • w[o] at endpoint is reduced from 0.00262 to 0.00243, average TFe content is decreased by 2%, phosphorus distribution is raised from 70. 85 to 78. 95, sulfur distribution is raised from 3.43 to 4.32 and manganese content is raised by 0. 02%.

CAST3M modelling of a spent fuel assembly bending during a handling accident Rod failure risk evaluation from the experimental results of spent fuel rod bending test

The fuel handling operating rules exclude any accidental risk. However in the framework of the PRECCI R&D project, the bending of a spent fuel assembly resulting from its locking during a translation displacement is taken into account. This enabled us to develop an approach based on experiments and calculations that allows us to simulate the behaviour of an assembly under such loading. This study was carried out in CEA laboratories with the funding and the technical support of EDF. A three points bending test on a spent fuel rod segment was performed at the Laboratory for Mechanical Behaviour of Irradiated Materials (LCMI). From the experimental strength-displacement curve, a maximum failure strain, a maximum failure curvature and an equivalent constitutive equation were determined. CAST3M modelling of the fuel rod taking into account the elasto-plastic behaviour of the clad and the cracking of the UO2 fuel pellets was verified by the experimental results. Consequently, the identification of the respective contributions of the clad and of the pellets to the rod global behaviour was made possible. A two dimensional assembly with beam elements was modelled with CAST3M. The properties of the beams modelling the different parts of the assembly (top and bottom nozzle, grids) were chosen and adjusted according to their materials (zirconium alloys, steel) in order to obtain stiffness, tensile and shear behaviour, sliding and holding functions close to the experimental ones. Assembly bending calculations were performed. In order to obtain a rod integrity estimator, their maximum calculated strains and curvatures as a function of the bending angles can be compared to the failure experimental ones.