Radial Gas Research Articles

Numerical study on zero-power operation strategy of radial gas wave refrigerator

Radial gas wave refrigerators uniquely integrate pressurization and refrigeration processes. This paper emphasizes optimizing the device's structure to reduce power consumption. It is beneficial for the application in large-flow scenarios or areas with limited power resources. A transient numerical analysis methodology is developed for precise simulation. The mechanism of power consumption is revealed through the lenses of gas force and angular momentum. Strategies including nozzle inclination and curved channel design are proposed. The optimization process is steered by the principles of the Design of Experiments (DOE) methodology. The main results are presented as follows. Optimal oblique incidence of the driving gas can reduce power consumption by up to 59.6%. Implementing a curved channel yields a maximum 71.2% reduction in shaft work. The device attains self-driven operation by combining the inclined port with the backward-curved arched channel. The optimal parameters identified are α=120°, β=60°, and γ=50°. With these settings, the device produces 85 W of power to counteract mechanical friction and improves refrigeration efficiency by 16.5% compared to traditional designs. This study lays the groundwork for the practical application of radial gas wave refrigerators.

Enhancing plasma arc penetration ability with radial gas flow

Enhancing plasma arc penetration ability with radial gas flow

Identification of Dynamic Force Coefficients for an Additively Manufactured Hermetic Squeeze Film Bearing Support Damper Utilizing a Pass-Through Channel

Abstract The following paper presents breakthrough experimental results for a new hermetic squeeze film damper (HSFD) concept that is integrally designed within an externally pressurized tilting-pad radial gas bearing support. The flexibly damped gas bearing module was designed for a 7.2″ (183 mm) diameter shaft and fabricated using direct metal laser melting (DMLM); also known as additive manufacturing. The bearing and HSFD were sized based on ongoing studies for oil-free supercritical carbon dioxide (sCO2) power turbines in the 8.5 MW–10 MW power range. The development of the new damper concept was motivated by past dynamic testing on HSFD, which generated frequency-dependent stiffness and damping force coefficients. In efforts to eliminate the frequency dependency, a new HSFD architecture was conceived that adds accumulator volumes and a pass-through channel to previously conceived HSFD flow network designs. The other motivation for the work is the need to develop a cost-effective and reliable oil-free bearing technology that is scalable to large power turbomachinery applications. There were several objectives for the following work. The first objective was to successfully design and fabricate a single piece bearing-damper using additive manufacturing, while dimensionally controlling critical design features. The paper discusses the manufacturing steps and shows cut-ups that reveal adequate clearance control capability with internal damper clearances. The second objective was to perform experimental testing with the new HSFD design in efforts to extract stiffness and damping coefficients for excitation frequencies within 20–160 Hz and peak vibration amplitudes between 0.25 mils (6.35 microns) to 1 mil (25.4 microns). The test results for a single HSFD bearing module indicated that the design modifications to the HSFD architecture were successful in eliminating nearly all the frequency dependencies for the stiffness force coefficient. The dynamic tests yielded a stiffness coefficient that varied between 112 klb/in. (19.6 MN/m) and 96 klb/in. (16.8 MN/m). The damping force coefficient however, exhibited relatively more variation with frequency with values residing between 175 lb-s/in. (31 kN-s/m) to 214 lb-s/in. (37 kN-s/m). Finally, the paper advances a three-dimensional fluid-structure interaction (FSI) model using transient finite element analysis (FEA) coupled to a computational fluid dynamics (CFD) model. The FSI analysis performed between 20 Hz and 80 Hz was used to predict the stiffness and damping of the HSFD using a quarter-section model of the damper. The FSI analysis was able to support test results by showing only a 6–7.4% change in the magnitude of force coefficients. Stiffness predictions agree reasonably well with experiments whereas damping is underpredicted.

The concept of axial movement of blast furnaces and temperature distribution on the horizon of air tuyeres

The purpose of the work is to clarify the data on temperature changes on the horizon of the air tuyeres of blast furnaces. The limitations associated with the implementation of the well-known concept of axial movement of blast furnaces in terms of temperature stabilization in the coke nozzle blast furnace are considered. Based on the comparison of the results of studies on the temperature distribution of coke and its fractional composition at level of air tuyeres, it is shown that on blast furnaces equipped with coneless filling devices and coal dust blowing units, the critical zone in the distribution of temperatures and their fluctuations in time is the intermediate zone between "bird's nest" and the center of the furnace. A temporary, but sufficiently long-term decrease in the temperature of coke to 1000 °C in the intermediate zone of modern blast furnaces is not accompanied by the danger of toterman formation, which is facilitated by the existence of an axial coke vent — a kind of heated core of the coke nozzle and sufficient thermal inertia of the furnace. It has been established that the increase in blowing costs affects distribution of coke temperatures on the horizon of air tuyeres in a similar way to the tendency of the hot strength of coke to deteriorate — the temperatures in the intermediate zone of the coke nozzle decrease. It is recommended to take into account the change in the quality of the loaded coke when choosing dimensions of the coke vent in the center of the furnace and the degree of forcing its course by blowing. In the conditions of using pulverized coal fuel, when working on coke of average quality, the most acceptable mode of organization of the radial gas flow is peripheral-axial with an advantage in the development of axial over peripheral. Despite some conventionality of the examples discussed in the article, it can be argued that a long axial stroke without stroke disturbances can be realized only if the intensity of the peripheral gas flow is maintained for specific conditions. That is, in an ideal form, axial movement of blast furnace melting is practically impossible.

Experimental investigations of the influence of radial gas mixing in an inert ceramic foam bed on thermal combustion of lean methane-air mixtures

The paper discusses the application possibilities of ceramic foam in a thermal combustion process of a lean methane-air mixture. The experiments were done in a ceramic foam bed. The foam (Vukopor ® A) was made mainly of Al 2O 3. The foam samples were packed in a tubular reactor symmetrically placed in a laboratory furnace. It was assumed that the tested foam should have a surface close to the monolith surface area which was tested in a previous work (Pawlaczyk and Gosiewski, 2015). Pore density of the tested foam was 10 PPI. The tested air mixture contained 0.51 - 0.76 vol. % of methane. The results show that thermal methane oxidation in foam is possible in the acceptable range of temperatures. The combustion process in foam is characterized by similar ignition temperature to tests carried out in monolith, a more intense course, and better methane conversion at lower temperatures.

Dynamic Characteristic and Performance Analysis of Claw Vacuum Pumps with Multi-Claw Rotors

The number of lobes of multi-claw rotors determines the performance of claw vacuum pumps including the pumping speed, dynamic characteristics, and operating conditions. In order to reveal the effects of the number of lobes on rotor performance, in this study, a geometric model of multi-claw rotors was established. The structure and geometric performance of multi-claw rotors including suction port and discharge port, pumping speed, and volumetric utilization ratio were compared. Furthermore, a dynamic characteristic model of claw rotors was established, and, therefore, axial gas forces, radial gas forces, and gas resistance torques of multi-claw rotors were obtained. The results indicate that double-claw rotors increased 34.67 % and 4.59 % in terms of pumping speed and volumetric utilization ratio compared to single-claw rotors, and triple-claw rotors showed similar increases as double-claw rotors. The triple-claw rotors have a 49.39 % and 31.38 % reduction in compression duration compared to the double-claw rotors and single-claw rotors. The gas resistance torques of the multi-claw right rotors are consistently more than that of the left rotors, which demonstrates that the multi-claw right rotors are more suitable to serve as the driving rotors. The research contents of this paper are of great theoretical significance for the selection of rotor lobes and the design of claw vacuum pumps with prominent dynamic characteristics.

SDSS-IV MaNGA: the role of the environment in AGN triggering

ABSTRACT The large- and small-scale environments around optically-selected AGN host galaxies and a control sample of non-active galaxies in the MaNGA survey have been investigated in order to evaluate the importance of the environment in AGN triggering. Using the MaNGA integral field spectroscopy, we quantify non-circular motions of the ionized gas and detect an excess of radial gas motions in AGN hosts relative to control galaxies, not associated to AGN feedback and are most likely the result of tidal interactions, possibly associated with the triggering of the AGN. We find that the large-scale environments are similar for the AGN hosts and control galaxies in our sample and are biased towards lower large-scale densities and group virial masses, suggestive that the large-scale environment properties is only relevant to the AGN phenomenon in an indirect way, in the form, e.g. of the morphology-density relation. The small-scale environment, as measured by the frequency and luminosity of close neighbours, was also found to be similar for AGN and control galaxies. However, we find a correlation between the intensity of the non-circular gas motions in AGN hosts and the strength of the tidal field, while the control sample does not present such correlation. Also, AGN hosts with the most intense radial gas motions present larger tidal fields than their control galaxies. These findings indicate that at least a fraction of the AGN hosts in our sample have been triggered by tidal interactions with nearby galaxies.

Numerical modelling of two-phase flow hydrodynamics of column flotation - validation against ERT data

ABSTRACT In mineral processing, column flotation is being used extensively for fine particle beneficiation. Although a few attempts were made to develop computational fluid dynamics (CFD) models for column flotation in the past, validation against comprehensive experimental data is yet to be demonstrated. This work employs an Eulerian-Eulerian model coupled with the standard k-ε turbulence model for modeling the hydrodynamics in the column flotation. The two-phase simulations were performed on both laboratory and industrial-scale column flotations. The two-fluid model was further modified with the appropriate interphase forces (Ishii-Zuber drag force and Tomiyama lift force) and population balance method (PBM) to accurately simulate and predict the bubble dynamics. The axial and radial gas holdup variations along with the axial liquid velocity are predicted at different air and liquid superficial velocities. The numerical predictions were then validated against the Electrical Resistance Tomography (ERT) data in a 4-inch laboratory column flotation and conductivity probe data in an industrial column flotation. The modified two-fluid model was able to predict accurate hydrodynamics close to ERT data. The gas holdup was found to increase with the superficial air velocity, liquid height, and liquid velocity. The gas holdup found uniformly dispersed radially at low superficial air velocities and heterogenous dispersed bubble flow at higher superficial velocities. A parabolic profile of liquid flow observed at higher superficial air velocities.

Spatial distribution of void fraction in the liquid slug in vertical Gas-Liquid slug flow

Vertical slug flow is characterized by the intermittent passage of two structures, the Taylor bubble and the liquid slug. The Taylor bubble is an elongated gas bubble with a bullet shape that flows upward and fills most of the radial cross-section, leaving room for an annular downward flow of a liquid film. The liquid slug is composed of the liquid phase carrying small, scattered bubbles and flowing upwards. The liquid slug presents three main regions: the wake, the development and the fully developed one. The liquid slug has a high concentration of dispersed bubbles in the wake region because of the entrainment mechanism. The detachment point (Dt) is a stagnation point with almost no dispersed bubbles around it, occurring close to the wall in the wake region end. Experimental data for the gas fraction in three different pipe diameters (26, 40.8 and 50 mm) were gathered in the 14-meter-high vertical flow experimental facility of the NUEM/UTFPR MULTILAB. The gas fraction along the liquid slug was evaluated by using a capacitive wire-mesh sensor (WMS) for quantitative results and a high-speed camera was used to analyze qualitative results. A new correlation to predict the average volumetric gas fraction along the unit cell is proposed. Radial and axial gas fraction distribution were analyzed and the detachment point was identified. The Reynolds and Froude number influence on the Dt point was evaluated and a new correlation to predict the Dt location (LDt) is proposed.

Study on the optimal channel angle design of radial gas wave ejector with performance examination under varying operating conditions

This paper proposes a novel type of GWE (named as DUT-R1) equipped with radial curved channels, which can enhance the energy transfer efficiency using centrifugal force. Through 3D simulation, the design method for the principal structural parameters was determined. The ejection rate (ξ) and total efficiency (ηT) of DUT-R1 with the optimal channel angles can reach 35.4% and 53.6%, respectively, which are 10.63% and 27.62% higher than those of pre-optimization model. Moreover, the shaft power consumption can also be decreased by 1.56 kW.A new experimental platform of DUT-R1 was established to validate simulation results and obtain the equipment application performance under different conditions. The device achieves its optimum performance under the design condition, proving the rationality of the angle design. The highest ηT and ξ can reach 49.5% and 29.75%, respectively. Moreover, the shaft power changes with the varying operating conditions, and the maximum variation within the experimental range is 0.81 kW. Compared to conventional axial-flow GWE, the ξ of DUT-R1 under its designed conditions can be enhanced by 15.38% to 30.43%, and the ηT experiences an increase of 6.52% to 28.95%. Furthermore, the DUT-R1 demonstrates an extended range of effective operating conditions.

A 2D steady state analytical model for atmospheric pressure RF plasma jet

This paper presents a 2-dimensional analytical model for plasma inside the discharge tube of an RF atmospheric pressure plasma jet (APPJ) in coaxial geometry. Since the model is a steady state one, it requires that the frequency of the applied RF be high enough so that the formation of streamers and plasma bullets is suppressed and that continuous plasma is present throughout the RF cycle. It is also assumed that power absorption is due to electron-atom collisions in the bulk plasma. The model takes into account gas flow, yielding a flow-diffusion axial flux that aids the exit of the plasma into the atmosphere. The inputs to the model are the reactor dimensions, average power fed (P av ) and the flow velocity of the gas (ug) using which the model yields the plasma density along with its radial and axial profiles, electron temperature, axial and radial particle fluxes, gas heating, flux, and energy of the plasma particles escaping from the discharge tube into the ambient air. Experiments were undertaken on an RF-powered jet at 13.56 MHz. Substituting the average RF power, measured using voltage and current probes, into the model gives the plasma density n ≈ 3.9 × 1017(≅2.8 × 1019)m−3 at for He (Ar). The corresponding electron temperature given by the model is for He (Ar). It is hoped that the developed model would be able to provide a comprehensive methodology for analyzing APPJs.

Experimental study on radial diffusion characteristics of diesel–pentanol spray

It is always a hot topic to find alternative fuel for diesel. Pentanol is a potential alternative fuel for diesel. In this study, different volume ratios of fuel were obtained by adding pentanol to diesel. On the high-pressure common rail experimental platform, the spray processes of pure diesel and diesel–pentanol blends were observed and analyzed, and the differences of radial diffusion capability between different experimental fuel sprays were evaluated. The maximum radial diffusibility was analyzed through the maximum width and the maximum width corresponding to the axial position. The radial diffusion capacity of the whole was analyzed by means of the average width and spray cone angle, and the area of the gas entrainment area was analyzed. The results showed that the addition of pentanol enhanced the radial diffusion ability and gas entrainment ability of diesel sprays.

SDSS-IV MANGA: THE RADIAL DISTRIBUTION OF PHYSICAL PROPERTIES WITHIN GALAXIES IN THE NEARBY UNIVERSE

Using the largest sample of galaxies observed with an optical integral field unit (IFU, the SDSS-IV MaNGA survey, ≈10000 targets), we derive the radial distribution of the physical properties obtained from the stellar continuum and the ionized-gas emission lines. Given the large sample, we are able to explore the impact of the total stellar mass and morphology by averaging those radial distributions for different bins of both global properties. In general, we find that most of the properties exhibit a negative gradient, with a secondary impact by global properties. Our results confirm the intimate interplay between the properties of the stellar component and those of the ionized gas at local (kpc) scales to set the observed radial gradients. The resemblance of the gradients for similar global properties indicates statistical similar histories of star formation and chemical enrichment, with an initial radial gas distribution following the potential of the galaxy.

Numerical Simulation of Flashing Flows in a Converging–Diverging Nozzle with Interfacial Area Transport Equation

Flashing flows of initially sub-cooled water in a converging–diverging nozzle is investigated numerically in the framework of the two-fluid model (TFM). The thermal non-equilibrium effect of phase change is considered by an interfacial heat transfer model, while the pressure jump across the interface is ignored. The bubble size distribution induced by nucleation, bubble growth/shrinkage, coalescence, and breakup is described based on the interfacial area transport equation (IATE) and constant bubble number density model (CBND), respectively. The results are compared with the experimental data. Satisfactory prediction of the axial pressure distribution along the nozzle as well as the flashing inception, is achieved by the TFM-IATE coupling method. It was also found that the vapor production in the diverging section was overpredicted, and the radial gas volume fraction distribution deviated from the experiment. The radial diameter profiles exhibit opposite patterns at the nozzle throat and near the outlet, and similar trends can be observed for the superheated degree. A poly-disperse method is suggested to be introduced to describe the evolution of interfacial area concentration.

Experiments and modeling of fluidized bed steam-biomass char gasification with a red-mud oxygen carrier at particle scale for chemical looping

Chemical Looping Combustion (CLC) of biomass provides a low-cost way for CO2 negative emission. It creates complex multi-component flows including solids of oxygen carrier and fuel, and gasses of steam and/or CO2 as well as other gasification products. Experiments and modeling of steam-gasification of biomass char were investigated using a low-cost red mud as oxygen carrier materials. Effects of temperature, steam concentration, H2 inhibition on chemical reaction kinetics and mass transfer were experimentally investigated and modeled. A self-designed macro-TGA was used to detect its oxidization kinetics under isothermal conditions. The red mud oxygen carrier reduced inhibitory effect of H2 on carbon reaction, thus enhancing char conversion remarkably. With the neglect of the external mass limitation on char conversion, the reaction kinetics during reduction process was calculated by an experimentally-fitted function, expressing the char conversion. Pore structure evolution during the char conversion on kinetics was considered and its function was obtained based on the experimental results. The radial gas profiles under the bed of red mud particles by the solution of interparticle and external mass transfer coupled with the kinetics of char gasification were obtained, revealing the whole process of char conversion in CLC process. A semi-empirical kinetic model, including both of chemical and diffusion processes, provided a good insight of oxidation reaction kinetics, which was proven to be better than the classic models. The experimental data and modeling results got high agreement in both reduction and oxidation reactions.

Reliable Automatic Control of Radial Gas Distribution on Blast Furnace Throat

Reliable Automatic Control of Radial Gas Distribution on Blast Furnace Throat

3D Modeling of the Molecular Gas Kinematics in Optically Selected Jellyfish Galaxies

Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can perturb or even strip away their gas while leaving the stars undisturbed. We model the distribution and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204, JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure stripping. We analyze MUSE@VLT data and CO data from the Atacama Large Millimeter Array searching for signatures of radial gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206, which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in JO204 and JW100, but more uncertain in JO201 and JO206. We show that our sample follows the molecular gas mass–size relation, confirming that it is essentially independent of environment even for the most extreme cases of stripping. Our findings are consistent with the molecular gas being affected by the ram pressure on different timescales and less severely than the atomic and ionized gas phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.

Modeling Transient Flow Behavior of Off-Center Fractured Well with Multiple Fractures in Radial Composite Gas Reservoirs

Summary Vertical hydraulic fracturing is widely used to develop low-permeability gas reservoirs. Uneven distribution of formation permeability and stress leads to multiple-wing hydraulic fractures with different lengths, which results in the wellbore not being the center of the circular stimulated reservoir volume (SRV) region. Therefore, to simulate the wellbore pressure of this phenomenon, a semianalytical model of the off-center multiwing fractured well in radial composite gas reservoirs is presented and the corresponding solution method is shown. The model is verified with the numerical solution, and eight flow regimes can be distinguished under the ideal case, which includes bilinear flow, fracture interference, linear flow, radial flow of inner region, transition flow of inner region, and radial flow of inner region. Compared with the previous model in which the well is at the center of radial composite gas reservoirs, in this paper we present an obvious “step” after the inner region radial flow regime, which is related to the off-center distance and radius of the inner region. In addition, the effects of some important parameters (such as off-center distance, permeability mobility, inner region radius, and fracture distribution) on typical curves are discussed. Finally, field well testing data are used to verify the accuracy of the model.

Vibration characteristics control of hybrid radial gas foil bearing-rotor system: Simulation and experiment

Currently, tiny, high-speed rotating machines frequently employ air foil bearings. Air is employed as the working medium, however, when the rotor speed is high, the rigidity of the air film is insufficient, which restricts the usage of air foil bearings. This study utilizes the external gas supply method of hydrostatic gas bearings to strengthen the air film stiffness of air foil bearings. The original air foil bearings are combined with external gas supply piping to create the hybrid gas foil bearing(HGFB), which may be utilized to increase the air film support stiffness of the bearings through the external gas supply. Additionally, by altering the gas supply pressure, this bearing may be used to actively manage the vibration characteristics of the shaft system, allowing the bearing performance to be adjusted to changing operating conditions. The static and dynamic properties of the HGFB with a 24 mm diameter are solved in this study using Newton's iterative approach and the finite difference method. The bearing-rotor system is modeled using this information. An Analysis is done on the impact of various air supply pressures and throttle hole widths on bearing performance and vibration characteristics of the shaft system. In this article, the vibration parameters of the bearing-rotor system are tested using an open-loop control test. The open-loop control experiment on the vibration response of the bearing-rotor system is performed using HGFBs with orifice sizes of 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm. The experimental results confirm the accuracy of the simulation results. Correspondingly, this paper conducted closed-loop control comparison experiments on the vibration properties of the bearing-rotor system using the PID control method and the fuzzy PID control method in succession. It then evaluated the control effect of the two control strategies on the vibration of the bearing-rotor system and managed to improve the conventional PID control method used for gas bearings.

Hydrodynamic instability of premixed tubular flame stabilized in stretched rotating flow

The paper analyzes the hydrodynamic instability of a cylindrical flame stabilized in a converging rotating gas flow simulating the flow in a cyclone combustion chamber. The analysis was carried out within the framework of a two-dimensional model describing the gas flow with radial and tangential supply of combustible gas through the walls of a cylindrical chamber. In the stationary case, the gas flow in combustion products and the combustible mixture is described by the solution for a rotating tornado-shaped vortex. The rotation of the gas creates a centrifugal force, which has a stabilizing effect on the flame perturbations. The dependences of the perturbations growth rate on the wave vector of perturbations, the radial and tangential inlet gas velocities, and other parameters of the problem are obtained. The analytical criterion of neutral stability separating regions of stable flame with respect of any perturbations and flame instability in the plane of radial and tangential velocities is obtained. In the absence of rotation and at the large flame radii, the model converts into the Landau- Darrieus model of flame hydrodynamic instability.