Cold Model Experiments Research Articles

Experimental and numerical investigation of isolator in three-dimensional inward turning inlet

Numerical simulation about a three-dimensional inward turning inlet with isolator and combustor was performed to study the flow field structure and flow characteristics of shock train. Cold and hot model wind tunnel experiments were carried out to compare the effects of cold and hot condition on shock train characteristics. The result shows that no oscillation phenomenon of the shock train was observed in the cold model experiment, but oscillation back and forth occurred in the hot model experiment. The trend of pressure distributions are consistent in cold and hot condition before the combustor. But it changed in the combustor where the pressure presented a continuous rising trend in cold condition, while a trend of rising first and then descending in hot condition. Establishing the corresponding relationship between throttling ratio and gas-oil ratio is beneficial to predict the property of the isolator in hot condition according to the cold condition.

Experimental study on the removal of FCCS catalyst particles by electrostatic separation

ABSTRACT Electrostatic separation is a technology for removing catalyst particles from fluid catalytic cracking slurry (FCCS). In this study, the particle trajectory was simulated by COMSOL Multiphysics based on theories and deductions. To verify whether these theories are reasonable for an electrostatic separation simulation, a mixture of alkylbenzene and catalysts was used to characterize the FCCS, and a cold model experiment was carried out, Moreover, the effects of the raw material properties, operating conditions and material properties on the efficiency of the separation were investigated. The results showed that the separation efficiency increased with decreasing glass sphere diameter because the porosity decreased. With the increase in the size of the catalyst particles, the dielectrophoretic (DEP) force increased rapidly and played a more important role, and the separation efficiency increased. Increasing the separation time helped adsorb the catalyst particles that were far from the contact point of the glass ball, and some particles in these areas were unable to be adsorbed. The electrostatic separator has the optimal voltage, and this value decreased with decreasing glass sphere diameter. The experimental results were consistent with the theoretical analysis. Through the nonlinear fitting of a large number of experimental data points, the prediction model of the device was obtained.

Influence of rotational speed and aspect ratio on the flow patterns of different fluids subjected to rotation about vertical axis

The quality of the Centrifugal cast primarily depends on flow behavior of the melt during its rotation in addition to other process parameters.The opaque nature of mold and melt posses problems in the analysis of fluid behavior.The present investigation therefore focus on cold modeling experiments for vertical centrifugal casting in which permanent fluids such as water, SAE90 and Glycerine were subjected to vertical axis of rotation in a transparent mould at room temperature, in which the fluid flow patterns were observed with respect to variation in the process parameters such as thickness of the cylindrical fluid, viscosity, aspect ratio and rotational speed of mould.For high aspect ratio and maximum thickness the fluid cylinder was observed to be conical in shape. In a mould having aspect ratio 0.5 and 1.0, for different fluid thickness, the complete fluid cylinder was formed in the range of 350–450 rpm. The maximum G value required either to form complete fluid cylinder or the fluid to reach extreme point of the cylindrical mould was found to be in the range of 10G–28G,14G–39G using mould of aspect ratio 0.5 and 1.0 respectively and the lift of of the fluid was found to be easier in case of high viscous fluid. Also the melt flow behaviour has been studied by obtaining cast of Al-12%Si at diffetent rotational speeds. The results obtained in cold modeling experimentation were validated by CFD simulation using ANSYS Fluent software also compared with actual cast.

Gas-particle turbulent flow of foursquare tangential jets in a simplified pulverized-coal firing boiler

An experimental cold-model of a simplified tangential firing boiler was established to investigate the mesoscale turbulent flow behaviors, including gas vortex structures, particle motions and interactions between two phases. A modified PIV technology, employing two pairs of lasers and cameras, was applied to measure the velocity and velocity gradient of turbulent flow in foursquare tangential jets alternatively. At a given initial gas velocity and particle mass loading, the interaction between gas and particles was studied at three different particle sizes. It was found that two main coherent vortex structures, circular eddy and hairpin eddy, distributed mainly in low speed area and heavy impingement area, respectively. The characteristics of particle motion in foursquare tangential jets correlated with gas turbulence dissipation, particle size, particle concentration and particle density. Small particles were easily entrained by gas vortex, so that they consumed more turbulence energy and attenuated the gas turbulence intensity. On the contrary, large particles had more inertia and led to heavier impingement in the chamber center, resulting in particle random distribution and complex momentum transfer between gas and particles. Moreover, large particles stretched the coherent vortex to be narrow and long, while small particles pulled down the vortices rotation intensity.

Short-term repeated HRV-16 exposure results in an attenuated immune response in vivo in humans.

IntroductionNaturally, development of adaptive immunity following HRV infection affects the immune response. However, it is currently unclear whether or not HRV re-exposure within a short time frame leads to an altered innate immune response. The “experimental cold model” is used to investigate the pathogenesis of HRV infection and allows us to investigate the effects of repeated exposure on both local and systemic innate immunity.Methods40 healthy male and female (1:1) subjects were nasally inoculated with HRV-16 or placebo. One week later, all subjects received HRV-16. Baseline seronegative subjects (n = 18) were included for further analysis.ResultsInfection rate was 82%. Primary HRV infection induced a marked increase in viral load and IP-10 levels in nasal wash, while a similar trend was observed for IL-6 and IL-10. Apart from an increase in IP-10 plasma levels, HRV infection did not induce systemic immune effects nor lower respiratory tract inflammation. With similar viral load present during the second HRV challenge, IP-10 and IL-6 in nasal wash showed no increase, but gradually declined, with a similar trend for IL-10.ConclusionUpon a second HRV challenge one week after the first, a less pronounced response for several innate immune parameters is observed. This could be the result of immunological tolerance and possibly increases vulnerability towards secondary infections.

Filtration Performance of Coal Pyrolysis Flying Char Particles in a Granular Bed Filter

The filtration of flying char particles from coal pyrolysis vapors plays a very important role in enhancing yields and quality of pyrolysis oil. In this work, the performance of coal pyrolysis flying char particles in a granular bed filter (GBF) was studied in cold model experiments. A filtration model was developed using a macroscopic phenomenological method that describes the filtration of the GBF. The polynomial expression of the relative filter coefficient (F) and the nonlinear expression of the relative pressure drop ratio (G) were applied in the new model. The unsteady state of granular filtration was captured, demonstrating that the GBF performance could be predicted by the new model. Effects of superficial gas velocity, thickness of granular layer, and dust mass concentration on collection efficiency and pressure drop were analyzed. An excellent performance of the GBF was obtained and the total collection efficiency could reach a span between 98% and 99.9%. In the case of lower dust mass concentra...

Improving particle flow in liquid-solid countercurrent extraction tower by insert structure optimization: A combined study on experiments and DEM simulations

The particle velocity distributions in the liquid-solid countercurrent nylon 6 extraction tower equipped with different types of inserts were investigated by both cold-model experiments and 2D-DEM simulations. The cold-model experiment results near the insert were well interpreted by the distribution of the particle contact force acquired from the DEM simulation. Compared with the disordered particle flow caused by a conventional single-funnel insert, the uniform particle flow could be realized by a special combination of single-funnel inserts with 53° and 35° dip angles of the upper and lower parts, respectively. In addition, a new type of insert, the multi-funnel insert, was found to be more beneficial in improving the uniformity of the particle velocity distribution because it made the particle contact force near the insert uniform. Furthermore, the mass flow state could be maintained in a wider range of discharge rate, which implied an enhancement of the operating flexibility of the tower equipped with the multi-funnel insert. These developed inserts have the potential to be applied in large-scale liquid-solid countercurrent extraction processes.

Design and cold model experiment of a continuous-wave deuteron radio-frequency quadrupole

Design and cold model experiment of a continuous-wave deuteron radio-frequency quadrupole

Influence of primary air cone length on combustion characteristics and NOx emissions of a swirl burner from a 0.5 MW pulverized coal-fired furnace with air staging

This paper presents experimental research on cold flow, combustion characteristics, and NOx emissions of a swirl burner with air staging. The aim of the research is to investigate the influence of primary air cone length on the swirl burner performance. Cold flow air experiments on a centrally fuel-rich swirl burner with an over-fire air ratio of 25% were performed, and it was observed that when the dimensionless primary-air cone length (i.e., Lp/Li, Lp and Li respectively denoting the primary-air cone length in the cold-modeling experiments and inner secondary-air cone length) increases from 0 to 0.75, the diameter and length of the recirculation zone reduces from 0.91 d and 1.51 d to 0.68 d and 0.57 d, respectively. An investigation was conducted in a 0.5 MW laboratory furnace in order to optimize the primary-air cone length of a centrally fuel-rich swirl burner. The flame stability, performance of ignition, and burnout are significantly improved by decreasing the primary-air cone length. The NOx emissions measured at the furnace exit with a cone length Lp/Li = 0 decreased by 50.3% compared to those measured with a cone length Lp/Li = 1.0. Based on the evaluation of flame stability, performance of the ignition, burnout, and low NOx emissions, the optimum value of primary-air cone length was observed to be Lp/Li = 0.

Effects of DC electric fields on meso-scale structures in electrostatic gas-solid fluidized beds

Electric fields have great potential to control meso-scale structures, typically bubbles and agglomerates in gas-solid fluidized beds. However, previous research only considered the effects of polarization forces and ignored the electrostatic effects. This work, by means of cold model experiments, for the first time investigates the effects of DC electric fields on meso-scale structures in a 3-D fluidized bed with electrostatic effects. Results show that particles will also experience the Coulomb force under the effects of electrostatics besides of polarization forces, and the effects of these two electric field forces are different. The Coulomb forces make particles migrate at lower field strengths, then increases the bubble size and breaks up agglomerates. While at higher field strengths, the polarization forces result in formation of agglomerates and reduction of bubble size. Therefore, the effects mechanism of electric fields is the competition effects between the Coulomb force and the polarization forces. The critical transition field strength, at which the predominant position of Coulomb and polarization forces on bubbles and agglomerates changes, is significant in the control of meso-scale structures by DC electric fields.

Flow Patterns of Feed Spray in Different Fluid Catalytic Cracking Feed Injection Schemes

The helium tracer method is used to investigate the residence time distribution and flow patterns of feed spray in different fluid catalytic cracking feed injection schemes by cold model experiments. The axial Peclet number in the upward and downward oriented feed injection schemes was obtained by fitting the residence time distribution into the one-dimensional axial dispersion model with an open–open boundary condition. Results suggest that the flow pattern of the mixed stream is closer to complete mixing in the initial contact region of spray with catalysts when the nozzles are mounted downward. A flow pattern variation index β is proposed to show the flow patterns in the feed injection schemes quantitatively. It is shown that a larger β is obtained when the feed nozzles are faced downward, meaning that the flow pattern of mixed stream in the feeding zone can develop more quickly from a likely complete mixed flow into a likely plug flow.

Bubble Motion and Gas-Liquid Mixing in Metallurgical Reactor with a Top Submerged Lance

Abstract The multiphase fluid mixing and bubble motion in a scale-down Isa smelting furnace with a top submerged lance were investigated through cold water model experiments. The mixing time in the liquid bath was determined by a novel criterion, and the bubble formation frequency and gas-liquid contact area were also measured by high-speed photographing. The empirical equations of mixing time (Tm) relating to mixing energy (ε) were ${T_{{\rm{m}},s}} = 913{\varepsilon ^{ - 0.5}}$ for solid tracer and ${T_{{\rm{m}},l}} = 624{\varepsilon ^{ - 0.48}}$ for liquid tracer, respectively. The mixing time trended down with the increasing of bubble formation frequency, affected slightly by the bubbles with small size and decreased obviously when increasing the gas-liquid contact area. The optimal conditions of gas flow rate, bath height, lance submerged height and lance diameter to guarantee high-efficiency mixing and low-level surface fluctuation/splashing were obtained.

Cold Model Experiment and Numerical Simulation of Flow Characteristics of Multi-phase Slag

Cold Model Experiment and Numerical Simulation of Flow Characteristics of Multi-phase Slag

A new design method for fluidized bed conversion of largely heterogeneous binary fuels

Binary fuels of a fluidized bed combustor or gasifier are solids composed of two groups of particles. Their optimal handling in the same bed becomes rather difficult if their hydrodynamic properties differ by two orders of magnitude or more. Both of these fuel classes are directly fed into the reactor in most cases but the rather homogeneous fuel originally fed switches into a binary character inside the reactor in some others. A typical example of the latter case is the thermal utilization of rubber wastes. A novel design is proposed in the present paper by setting up a non-mixing, non-elutriated binary bed. Design criteria and procedure are formulated as well. One of the known calculation methods is proposed to be applied for assuring a segregated bed by means of choosing the bed components, geometry, and gas velocity conveniently. Cold model experiments are proposed to be applied for assuring no elutriation of the fine fuel particles and no sinking of the coarse fuel particles in the same time. A simple experiment is proposed for determining the common minimum fluidization velocity of the binary bed because known calculation methods can not be applied here.

Modeling of Quasi-Four-Phase Flow in Continuous Casting Mold Using Hybrid Eulerian and Lagrangian Approach

Lagrangian tracking model combined with Eulerian multi-phase model is employed to predict the time-dependent argon–steel–slag–air quasi-four-phase flow inside a slab continuous casting mold. The Eulerian approach is used for the description of three phases (molten steel, liquid slag, and air at the top of liquid slag layer). The dispersed argon bubble injected from the SEN is treated in the Lagrangian way. The complex interfacial momentum transfers between various phases are considered. Validation is supported by the measurement data of cold model experiments and industrial practice. Close agreements were achieved for the gas volume fraction, liquid flow pattern, level fluctuation, and exposed slag eye phenomena. Many known phenomena and new predictions were successfully reproduced using this model. The vortex slag entrapment phenomenon at the slag–steel interface was obtained using this model, some small slag drops are sucked deep into the liquid pool of molten steel. Varying gas flow rates have a large effect on the steel flow pattern in the upper recirculation zone. Three typical flow patterns inside the mold with different argon gas flow rates have been obtained: double roll, three roll, and single roll. Effects of argon gas flow rate, casting speed, and slag layer thickness on the exposed slag eye and level fluctuation at the slag–steel interface were studied. A dimensionless value of Have/h was proposed to describe the time-averaged level fluctuation of slag–steel interface. The exposed slag eye near the SEN would be formed when the value of Have/h is larger than ~0.4.

Oscillation-Mark Formation and Liquid-Slag Consumption in Continuous Casting Mold

Traditional understanding on the complex multiphysics phenomenon of the meniscus in the oscillating mold for continuously cast steel, including oscillation-mark formation and liquid-slag consumption, has never considered the shape influence of the flux channel between the mold wall and the solidifying shell surface. Based on the reciprocating oscillation of mold, this study was carried out to calculate theoretically the periodic pressure and the liquid-slag layer thickness in the flux channel for the upper and the lower meniscus that possess different shapes in combination with a transient equilibrium profile of the flux channel as well as the sinusoidal and the nonsinusoidal oscillation modes of mold. The effect of flux channel shape on the multiphysics phenomenon in the meniscus was determined by the physical oscillation simulation by using an experimental cold model mold. The results show that the shape difference between the upper and the lower meniscus leads to the opposite direction of pressure in the flux channel. The pressure in the opposite direction plays a respective role in oscillation-mark formation and liquid-slag consumption in an oscillation cycle of mold, and thus, it makes a new mechanism for explaining the multiphysics phenomenon in the meniscus. The oscillation mark is initially formed by the rapid increase of positive channel pressure in the upper meniscus, and most of the liquid slag is infiltrated into the flux channel by the negative channel pressure in the lower meniscus from the end of a positive strip time to the beginning of the next positive strip time, including the negative strip time in between. Furthermore, the physical characteristics of the lubrication behavior in the meniscus are summarized, including liquid-slag infiltration, solidifying shell deformation, and the thickness change of the liquid-slag layer.

Aerodynamic characteristics of a 350-MWe supercritical utility boiler with multi-injection and multi-staging: Effects of the inner and outer secondary air distribution in the burner

Prior to commercial operation of the first-ever 350-MWe supercritical down-fired boiler incorporating multiple injection and multiple staging combustion technology, cold modeling experiments varying the inner-to-outer-secondary air (ISA/OSA) ratio (applying ratios of 0:10, 2:8, 5:5, 6:4 and 10:0) were performed within a 1:13 scale model of the boiler furnace. The aim of these trials was to establish an optimal inner and outer secondary air distribution model for the burner in the full-scale furnace. At ratios of 0:10 and 2:8, the fuel-rich flow apparently diffused toward the furnace center zone after leaving the corresponding nozzle outlet, resulting in the formation of relatively small recirculation zones below the arches and independent fuel-rich and fuel-lean flow streamlines. In contrast, at ISA/OSA ratios greater than or equal to 5:5, the strengthened carrying effect of the inner secondary air significantly reduced the diffusion of the fuel-rich flow. Consequently, the fuel-rich and fuel-lean flow streamlines combined in the middle region of the lower furnace and the recirculation zones under the arches enlarged. As the ISA/OSA ratio was increased from 0:10 to 10:0, the line fitting slopes for the downward airflow decay curves increased from 1.8 to 3.0, meaning that the downward airflow decayed more rapidly, such that the penetration depth was reduced. Finally, at ISA/OSA ratios of 0:10 and 2:8, the initial flow-field deflection was observed to gradually adopt a symmetrical pattern.

Interaction behaviour between top blown jet and molten steel during BOF steelmaking process

During oxygen steelmaking process, a systematical description of the interaction behaviour between top blown jet and molten steel is extremely important. In the present study, a cold model experiment and the corresponding numerical simulation were carried out to illustrate the highly complex interaction process inside an 80-t converter. First, the interaction process was presented in a numerical way. On this basis, the quantitative effect of pertinent operational parameters on the interaction process was investigated. To clearly describe the cavity appearance, the cavity shape index () was put forward, which is a dimensionless factor to demonstrate the cavity shape related to cavity depth and cavity width. In addition, a functional relationship correlating cavity shape index and blowing number was proposed. It can be concluded that higher blowing number (NB) results in deeper cavity depth and smaller cavity width. Moreover, the effect of cavity shape on the stirring characteristics and the mixing effect in the converter were investigated. The results show that lower and higher cavity shape index may lead to longer mixing time in smelting process. For 80-t converter, the penetration depth and impact width should be controlled approximately equal ( fluctuates around 1) to obtain better mixing effect.

Modeling of Droplet Generation in a Top Blowing Steelmaking Process

Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modeling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work, a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by Subagyo et al. on the basis of dimensionless blowing number (N B). The blowing number was re-evaluated at the impingement point of jet with taking into account the temperature effect of change in density and velocity of the gas jet. The result obtained from the work shows that the modified blowing number N B,T at the furnace temperature of 1873 K (1600 °C) is approximately double in magnitude compared to N B calculated by Subagyo and co-workers. When N B,T has been employed to the Subagyo’s empirical correlation for droplet generation, a wide mismatch is observed between the experimental data obtained from cold model and hot model experiments. The reason for this large deviation has been investigated in the current study, and a theoretical approach to estimate the droplet generation rate has been proposed. The suitability of the proposed model has been tested by numerically calculating the amount of metals in slag. The study shows that the weight of metals in emulsion falls in the range of 0 to 21 wt pct of hot metal weight when droplet generation rate has been calculated at ambient furnace temperature of 1873 K (1600 °C).

Effects of serostatus and gender on the HRV-16-induced local immune response

The “experimental cold model” is widely used to investigate effects of HRV infection. However, effects of serostatus and gender on the HRV-induced immune response have not been clarified.40 healthy seropositive and seronegative (1:1) male and female (1:1) subjects were inoculated with HRV-16.HRV infection increased viral load in nasal wash, which tended to be more pronounced in seronegative subjects. Furthermore, HRV infection increased levels of IP-10, IL-6, and IL-10 and leukocyte numbers in nasal wash of seronegative, but not of seropositive subjects. No differences in any of the parameters were found between both sexes.The HRV-induced local immune response is diminished in seropositive subjects compared with seronegative subjects, while gender does not influence this response. These results have important implications for the design of future experimental cold studies: seronegative subjects, from both sexes can be included.