Increase In Gas Permeability Research Articles

Reduced Surface Area for the Oxygen Reduction Reaction in Porous Electrode via Electrical Conductivity Relaxation.

Oxygen reduction reaction (ORR) performance of porous electrode is critical for solid oxide fuel cells (SOFCs). However, the effects of gas diffusion on the ORR in porous media need further investigation, although some issues, such as nonthermal surface oxygen exchange, have been attributed to gas diffusion. Herein, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with various porosity, pore radii and gas permeability were investigated via the electrical conductivity relaxation method and analysed using the distributed of characteristic time (DCT) model. The ORR is revealed with three characteristic times, which are gas diffusion, oxygen exchange via the surface corresponding to small pores, and oxygen exchange to large pores. Gas diffusion delays the oxygen surface exchange reaction, resulting in very low chemical oxygen surface exchange coefficient compared with that obtained with dense sample under the assumption that all the surfaces are active for the ORR. Reduced surface area is thus defined to quantitatively represent the gas diffusion effects. The reduced surface area increases with increasing gas permeability, demonstrating the importance of electrode engineering for fast gas transport. Moreover, reduced surface area is suggested for replacing the specific surface area to calculate the electrode polarization resistance using the ALS model.

Recycling and 3D-Printing Biodegradable Membranes for Gas Separation-toward a Membrane Circular Economy.

Polymer membranes employed in gas separation play a pivotal role in advancing environmental sustainability, energy production, and gas purification technologies. Despite their significance, the current design and manufacturing of these membranes lack cradle-to-cradle approaches, contributing to plastic waste pollution. This study explores emerging solutions, including the use of biodegradable biopolymers such as polyhydroxybutyrate (PHB) and membrane recycling, with a focus on the specific impact of mechanical recycling on the performance of biodegradable gas separation membranes. This research represents the first systematic exploration of recycling biodegradable membranes for gas separation. Demonstrating that PHB membranes can be recycled and remanufactured without solvents using hot-melt extrusion and 3D printing, the research highlights PHB's promising performance in developing more sustainable CO2 separations, despite an increase in gas permeability with successive recycling steps due to reduced polymer molecular weight. The study emphasizes the excellent thermal, chemical, and mechanical stability of PHB membranes, albeit with a marginal reduction in gas selectivity upon recycling. However, limitations in PHB's molecular weight affecting extrudability and processability restrict the recycling to three cycles. Anticipating that this study will serve as a foundational exploration, we foresee more sophisticated recycling studies for gas separation membranes, paving the way for a circular economy in future membrane technologies.

Decarboxylation cross‐linking of fluorescein‐based copolyimides for gas separations

AbstractA fluorescein‐based diamine, 2‐(3,6‐bis(4‐amino‐3‐hydroxyphenoxy)‐9H‐xanthen‐9‐yl) benzoic acid (CADA), was synthesized and copolymerized with Durene and 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to form a 6FDA‐Durene/CADA (3:2) copolyimide. The copolyimide was thermally cross‐linked at 300–425°C to form a series of decarboxylated cross‐linked polyimides. Compared with the 6FDA‐CADA polyimide, the incorporation of Durene diamine increased gas permeability of the pristine and the thermally cross‐linked polyimides greatly. The copolyimide cross‐linked at 375°C showed separation performance to the O2/N2 gas pair beyond the 1991 Robeson upper limit, while the CO2/CH4 separation property of the copolyimide cross‐linked at 425°C (PI‐425) was close to the 2008 Robeson upper limit. Moreover, the anti‐CO2‐induced plasticization property of the 6FDA‐Durene/CADA(3:2) copolyimides was improved by cross‐linking. The copolyimides cross‐linked at 350°C and above were not plasticized at a CO2 pressure up to 30 atm. This study showed that gas transport property of the decarboxylated cross‐linked polyimides could be improved significantly by the incorporation of bulky diamino moiety. The fluorescein‐based copolyimide had great potentials for gas separation applications.

A research on destress mechanism of underlying roadway for gas outburst prevention in deep, low‐permeability coal seam

AbstractGas outbursts pose a significant threat in the mining of deep low‐permeability coal seams. As mining depth increases, there is a rise in coal and gas dynamic disasters, rendering the gas outburst prevention technology from shallow mining areas unsuitable for deep coal seam exploitation. Addressing the challenges posed by deep, highly gassy coal seams, this study introduces a gas outburst prevention technology integrating destressing in the close distance underlying roadway with gas drainage. The article investigates the relevant technical parameters and assesses the feasibility of this approach. First, it establishes destressing model for the underlying roadway to derive an analytical solution for stress distribution in the coal seam. Second, appropriate technical parameters are designed considering the seepage characteristics of gas in the coal seam. Finally, the gas drainage technical scheme is implemented at Qujiang coal mine to verify its on‐site effectiveness. Field test results indicate an increase in gas permeability within the coal seam following destressing in the underlying roadway, accompanied by significant improvements in the efficiency of gas drainage and the advancement speed of the coal roadway. Specifically, the driving speed of the coal roadway has escalated from 40 m/month to 150 m/month. These outcomes demonstrate the potential of this technology as a promising approach for preventing gas outbursts in the challenging context of deep, low‐permeability coal seams, facilitating swift coal roadway excavation.

Effect of mechanical stretching and low amount of silica adding on gas transport properties of poly(butylene succinate-co-adipate) films

This work aimed at studying the influence of a post drawing process on the morphology and the gas permeability of a PBSA (Polybutylene succinate-co-adipate) film. Two films were studied, one of neat PBSA and one filled with 1%wt of silica. The influence of silica was also studied. Reference films of PBSA and PBSA + Si presented a spherulitic morphology despite a difference of spherulites sizes and long period. After stretching, this isotropic morphology changed to an oriented one, as shown by WAXS measurements. SAXS analysis revealed that stretching led to a lamellae organization in the stretching direction, with lamellae oriented perpendicular to the stretching direction. Thermal characterizations have shown that stretching did not modified the degree of crystallinity for both systems. The helium, carbon dioxide and oxygen permeability increased with stretching, mainly due to the orientation of crystalline lamellae, decreasing the diffusion path. Moreover, for PBSA + Si stretched films, small non-percolating voids were evidenced around the silica particles which could also make gas transport easier. Thus, for both systems, this increase in gas permeability happened in a different way.

Effects of stone powder on microstructure of manufactured-sand concrete and its gas permeability

With the development of infrastructure construction, natural sand resources have become increasingly scarce, and the use of manufactured sand has become inevitable. The unique stone powder in manufactured sand could significantly influent the concrete performance. To characterize the stone powder, a physical filling model was used to quantify the particle grading buildup. Isothermal calorimetry and thermogravimetric analysis determined the corresponding chemical activities. Subsequently, non-destructive testing flow methods were designed, referred to as nuclear magnetic resonance (NMR) and hydrostatic balance (HB), to test the pore structure, and a quasi-stationary flow method was used to test the gas permeability of the manufactured sand concrete. Finally, a random hierarchical bundle model using the NMR-HB method was proposed to predict the gas permeability of concrete based on the pore size distribution. The results showed that a moderate amount of stone powder could reduce the heat of hydration, increase the hydration products, improve the filling effect, and decrease gas permeability. A certain fineness of the stone powder could increase the heat of hydration, increase the hydration products, compact the pores from 4.5 to 50 nm, reduce the filling effect, and increase gas permeability. The maximum relative difference between the predicted and experimental gas permeability values of the random tube bundle model was reduced to 34.38 % using the NMR-HB method, whereas this value was 70.87 % using the mercury intrusion porosimetry (MIP) method.

Polynorbornenes with carbocyclic substituents: A perspective approach to highly permeable gas separation membranes

Gas transport properties of two sets of polynorbornenes bearing carbocyclic substituents of different nature (cyclohexyl, norbornyl, phenyl groups, and framed oligocyclic moieties) were systematically studied. The influence of side chain carbocyclic substituents on gas permeability and separation selectivity for CO2-containing gas pairs and gaseous hydrocarbons was evaluated. It was found that the presence of carbocyclic moieties in side chains of polynorbornenes promotes the increase in gas permeability similarly to that of SiMe3 groups, with this effect being enhanced by the increase in the number of cycles in the substituents. As a result, P(CO2) of the metathesis polymer with pentacene-based substituents is equal to 1200 Barrer. Studied polynorbornenes with carbocyclic substituents displayed promising gas separation selectivities: CO2/N2 separation selectivity up to 41 (above the 2008 upper bound in the Robeson diagram) and solubility-controlled hydrocarbon separation selectivity up to 16 for the n-butane/methane gas pair. For the polymer with pentacene-based substituents, the separation of the mixture of hydrocarbons and aging were studied. The studies revealed that the mixed gas C4/C1 separation selectivity of this polymer reaches 4, and a two-time reduction of permeability occurs in 8.5 months. Therefore, the incorporation of carbocyclic groups in the side chains of polynorbornenes can be considered as an efficient strategy for the design of polymeric gas separation membrane materials.

Preparation and characterisation of heat‐resistant fluorinated co‐polyimides and their gas transport characteristics

A series of fluorinated co-polyimide films based on the 6FDA-FTPPA/BAFL backbone were prepared from 4-(3-fluoro-4-(trifluoromethyl)phenyl)-2,6-bis(4-aminophenyl)pyridine (FTPPA),commercial 9,9-bis(4-aminophenyl)fluorene (BAFL), and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), with varying ratios of FTPPA:BAFL units (3:1, 2:1, 1:1, 1:2, and 1:3). Co-polyimides not only exhibit high thermal stability ( Tg > 357°C), good optical properties (λcutoff > 327 nm) and hydrophobicity (contact angle >91.4°), but also favorable solubility properties in both high and low boiling organic solvents. The fractional free volume of the polymers was simulated using molecular mechanics and molecular dynamics and correlated with experimental gas separation data. The presence of bulky groups led to high FFVs (>17.8%) and the formation of large microcavities with diameters ranging from 5.48 to 5.72 Å, which efficiently increased gas permeability. In pure gas permeation experiments, the permeability coefficients of CO2 and He for the 6FDA-FTPPA/BAFL (3:1) film were 41.48 and 79.38 bar, respectively, which were superior to those of commercial Matrimid and Kapton in terms of gas permeability. In especial, the 6FDA-FTPPA/BAFL (1:2) and 6FDA-FTPPA/BAFL (1:3) in co-polyimide membranes exhibited the most attractive separation performance for O2/N2 gas pairs, approaching the 1991 Roberson upper limit.

Low-Loading Mixed Matrix Materials: Fractal-Like Structure and Peculiarly Enhanced Gas Permeability.

Mixed matrix materials (MMMs) containing metal-organic framework (MOF) nanoparticles are attractive for membrane carbon capture. Particularly, adding <5 mass % MOFs in polymers dramatically increased gas permeability, far surpassing the Maxwell model's prediction. However, no sound mechanisms have been offered to explain this unusual low-loading phenomenon. Herein, we design an ideal series of MMMs containing polyethers (one of the leading polymers for CO2/N2 separation) and discrete metal-organic polyhedra (MOPs) with cage sizes of 2-5 nm. Adding 3 mass % MOP-3 in a polyether increases the CO2 permeability by 100% from 510 to 1000 Barrer at 35 °C because of the increased gas diffusivity. No discernible changes in typical physical properties governing gas transport properties are detected, such as glass transition temperature, fractional free volume, d-spacing, etc. We hypothesize that this behavior is attributed to fractal-like networks formed by highly porous MOPs, and for the first time, we validate this hypothesis using small-angle X-ray scattering analysis.

Morphological features of the cuticle of hatching eggs of chickens and turkeys subjected to pre-incubation treatment

Improving the productivity of poultry, especially egg crosses, depends on the quality of the bioceramic calcite (CaCO3) layers and surface glycoprotein film of the egg (cuticle). These are the barriers that control the flow of gases and water vapor. Any disruptions in the transport process can lead to a significant reduction in egg hatchability. It has been proven that treatment of chicken and turkey eggs with acid solutions (acetic acid or hydrochloric acid) and sodium hypochlorite prior to hatching has increased egg hatchability compared to the control. In view of this, the aim of this study was to investigate the protective structures of incubation eggs of chickens and turkeys using non-destructive electron microscopic methods and computer processing of digital images of the cuticle coatings of these eggs for reliable prediction of the degree of increase in gas permeability of the cuticle-shell system due to the destructive effect of various chemicals, including disinfectants, for pre-hatching egg treatment. In the experiments, hatching eggs of Leghorn White hens (n = 90) 15–20 weeks of laying and Broad Breasted White turkeys (n = 80) were used. The antimicrobial agents used in the experiments were a 0.6% solution (0.08 mol/L) of sodium hypochlorite, a 2.5% solution (0.4 mol/L) of acetic acid, and a 5.0% solution (1.40 mol/L) of hydrochloric acid. Using the computer analysis of digital electron microscopic images of the egg surface with the software packages Visilog and FemtoScan Online, it was experimentally proved that the destructive effect of these substances on the cuticle-shell system increases in the range of sodium hypochlorite &lt; hydrochloric acid &lt; acetic acid, which positively correlates with the gas permeability of hatching eggs of chickens and turkeys and the egg hatchability index. The presence of fundamentally different morphological features and correlations of the cuticle of chicken and turkey eggs in response to the action of acids and oxidants used for pre-hatching treatment was shown. The digital markers of the cuticle-shell system state, obtained from analytical programs of digital images, have been established, which makes it possible to reliably predict the indicators of increasing the hatchability of chicken and turkey eggs under the conditions of using certain chemicals. The prospect of further research is to study the effect of modern complex antimicrobial agents on the hatchability of poultry eggs of different species.

Gel-forming composition to increase the efficiency of water isolation in horizontal wells

Relevance. The need to develop new technical and technological solutions to improve the efficiency of water isolation in wells with horizontal termination in reservoirs with layered heterogeneity of the formation. Aim. To identify and propose a promising gel-forming composition for conducting water isolation in wells with horizontal termination in reservoirs with layered heterogeneity of the formation. Object. A well with a horizontal termination in reservoirs with layered heterogeneity of the formation. Methods. Laboratory and bench studies of the gel-forming composition for isolating water inflow in wells with different reservoir permeability by modifying it with functional additives and further adapting its application to various mining and geological conditions of the well; technology of injection of compositions with different viscosity in wells with horizontal termination in reservoirs with layered heterogeneity of the formation. Results. The paper considers the theoretical aspects of a hydrophobic layer formation on a watered reservoir surface effected by a hydrophobic composition, when it enters the reservoir. The paper introduces the mechanism of a water-insulating screen formation during injection of a gel-forming composition. The authors have defined the basic requirements for the gel-forming composition. They developed the formulation of the gel-forming composition with a different gelation time from 1 to 8 hours. Due to the composition injection, a water insulation screen is formed that can withstand significant water flow pressure. The water breakthrough pressure varies and depends on the initial permeability: with an increase in gas permeability from 0.1 to 1 mm2 of the breakthrough pressure it decreases by water and ranges from 4.5 to 11.5 MPa/m.

A comprehensive study on transport behaviour and physicochemical characteristics of PU/based 3-phase mixed matrix membranes: Effect of [HNMP][HSO4] ionic liquid and ZnO nanoparticles

The gas separation industry has witnessed a significant focus on mixed matrix membranes (MMMs) due to their exceptional potential, surpassing the performance of conventional polymeric membranes. This study aimed to develop and evaluate MMMs using polyurethane (PU) as the polymer matrix and zinc oxide (ZnO) and ionic liquids (ILs) as fillers. PU/ZnO, PU/IL, and PU/ZnO/IL MMMs were prepared utilizing the dry-phase inversion method, and their efficacy in separating CO2, CH4, and N2 gases was investigated under various conditions. A comprehensive characterization protocol using FTIR, FESEM, TGA, AFM, and tensile testing was employed for their thorough characterization. The membranes’ transport properties were assessed at different pressures and filler concentrations. Results showed that IL incorporation increased gas permeability by enhancing solubility, diffusion, ionic interactions, swelling, and accessible volume. Incorporating ZnO and IL particles in the PU matrix simultaneously improved transport properties, particularly selectivity. Robeson’s diagram analysis shows that the PU/0.5%ZnO/2%IL MMM performed best. Furthermore, molecular simulation methods, including Monte Carlo and molecular dynamics simulations, assessed adsorption isotherms and physicochemical properties such as free volume, density, and X-ray diffraction. Simulation outcomes were highly reliable with experimental results, affirming the results’ efficiency and validation. Overall, this study demonstrated the efficiency of using ZnO and IL in the MMMs, highlighting their potential in gas separation applications.

Roots of Cynodon dactylon increase gas permeability and gas diffusion coefficient of highly compacted soils

Roots of Cynodon dactylon increase gas permeability and gas diffusion coefficient of highly compacted soils

Stress and permeability evolution of high-gassy coal seams for repeated mining

Coal bed methane reservoirs in China are generally characterized by high stress and low gas permeability coefficient. Protected layer mining has the effect of unloading pressure and increasing gas permeability coefficient. There are few studies in the case of repeated mining with an orthogonal arrangement of the protected layer. Based on the engineering practice of the high gas coal seams group in Xinjing coal mine, a combination of numerical simulation and field test was used. The distribution law of plastic zone, stress-strain and gas permeability coefficient of the protected layer under the two states of single mining and repeated mining were obtained. The stress and gas permeability coefficient distribution of the protected layer was divided into 5 and 6 zones in plane for single and repeated mining cases. The field test tested the distribution law of stress, gas pressure, deformation, and gas permeability coefficient, and verified the reliability of the numerical simulation results. According to the characteristics of gas permeability coefficient distribution under the condition of repeated mining, a method for accurate gas extraction is proposed. The results of the study have important implications for the design of gas extraction schemes in orthogonal repeated mining situations.

Influence of grass root density on gas permeability and water retention in water hyacinth‐based biochar amended soil

AbstractThe present study focuses on the effect of root density on gas permeability and water retention in biochar‐amended soil used as a cover material in landfills. Biochar amendment of soil is important measurement in landfill cover, while vegetation is an important for ecological restoration. Despite its importance, little attention has been given to the adaptation of vegetated biochar‐amended soil in landfill cover. The interactions between the biochar, vegetation, and soil concerning the gas permeability remain unknown, which may lead to unexpectedly increased waste gas emissions in landfill covers. To enhance the utilization efficiency of biochar amendment and vegetation techniques in landfill covers, further investigation of their coupled effects on gas permeability and water retention is necessary. Four different treatments were applied to manufacture series of soil columns: bare soil (BS), biochar‐soil composite (BSC), vegetated biochar‐soil composite with low planting density (VBSCL) and high planting density (VBSCH). The soil water characteristic curve and gas permeability were observed under natural wetting and drying cycles. The results showed that VBSCL increased gas permeability by 142% as compared to BSC. VBSCH enhanced gas permeability by 168% as compared to BSC. This was due to the spreading and decaying root systems forming preferential pathways for gas transfer. Additionally, VBSCL and VBSCH made around a 10% increase in volume water content at the whole suction range, while BSC just enhanced around 20% water content at the low suction range (less than 10 kPa). The combination of roots and biochar have significantly enhanced water retention during entire suction range due to capillarity.

Hierarchical conductive metal-organic framework films enabling efficient interfacial mass transfer

Heterogeneous reactions associated with porous solid films are ubiquitous and play an important role in both nature and industrial processes. However, due to the no-slip boundary condition in pressure-driven flows, the interfacial mass transfer between the porous solid surface and the environment is largely limited to slow molecular diffusion, which severely hinders the enhancement of heterogeneous reaction kinetics. Herein, we report a hierarchical-structure-accelerated interfacial dynamic strategy to improve interfacial gas transfer on hierarchical conductive metal-organic framework (c-MOF) films. Hierarchical c-MOF films are synthesized via the in-situ transformation of insulating MOF film precursors using π-conjugated ligands and comprise both a nanoporous shell and hollow inner voids. The introduction of hollow structures in the c-MOF films enables an increase of gas permeability, thus enhancing the motion velocity of gas molecules toward the c-MOF film surface, which is more than 8.0-fold higher than that of bulk-type film. The c-MOF film-based chemiresistive sensor exhibits a faster response towards ammonia than other reported chemiresistive ammonia sensors at room temperature and a response speed 10 times faster than that of the bulk-type film.

Damage and failure characteristics of coal and surrounding rock under shaped blasting

The high crustal stress in deep coal mining undermines the efficiency and safety of blasting operations conducted to increase gas permeability in the coal seam. Therefore, in this study, theoretical research, computer-based numerical simulations, and experiments were conducted to investigate the damage and fracture characteristics of a coal body and surrounding rock subjected to shaped blasting. ANSYS LS-DYNA was employed for numerical simulations to understand how a shaped jet is formed and how damage occurs in shaped blasting. A model of crack evolution under the influence of detonation gases that is based on fracture mechanics theory was constructed to analyze the mechanism underlying the directional propagation of detonation cracks in shaped blasting. In the conducted experiments, shaped blasting resulted in the creation of an oval-shaped fragmentation area, which was evidence that the shaped cartridge limited the loss of energy in fragmentation, allowed detonation cracks to evolve further in the specimen, and caused the formation of a main crack that propagated in the direction along which energy was concentrated (i.e., directional damage). Compared with ordinary blasting, shaped blasting facilitated more efficient blast energy use and reduced undesirable blast disturbance to the surrounding rock by 58% according to the computed tomography image of resistivity. The results of this study provide valuable insights on safe and efficient coal production.

The Effect of Preconditioning Temperature on Gas Permeability of Alkali-Activated Concretes.

Alkali-activated materials (AAM) are binders that are considered an eco-friendly alternative to conventional binders based on Portland cement. The utilization of industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) instead of cement enables a reduction of the CO2 emissions caused by clinker production. Although researchers are highly interested in the use of alkali-activated concrete (AAC) in construction, its application remains very restricted. As many standards for hydraulic concrete's gas permeability evaluation require a specific drying temperature, we would like to emphasize the sensitivity of AAM to such preconditioning. Therefore, this paper presents the impact of different drying temperatures on gas permeability and pore structure for AAC5, AAC20, and AAC35, which contain alkali-activated (AA) binders made from blends of FA and GGBFS in slag proportions of 5%, 20%, and 35% by the mass of FA, respectively. The preconditioning of samples was performed at 20, 40, 80, and 105 °C, up to the obtainment of constant mass, and then gas permeability was evaluated, as well as porosity and pore size distribution (mercury intrusion porosity (MIP) for 20 and 105 °C). The experimental results demonstrate up to a three-percentage-point rise in the total porosity of low-slag concrete after 105 °C in comparison to 20 °C, as well as a significant increase in gas permeability, reaching up to 30-fold amplification, contingent upon the matrix composition. Notably, the alteration in pore size distribution, influenced by the preconditioning temperature, exhibits a substantial impact. The results highlight an important sensitivity of permeability to thermal preconditioning.

Structural evolution and gas separation properties of thermally rearranged polybenzoxazole (TR-PBO), polymer-carbon transition (PCT) and early-stage carbon (ESC) membranes derived from a 6FDA-hydroxyl-functionalized Tröger's base polyimide

The changes in physical, chemical, and gas permeation properties of a heat-treated hydroxyl-functionalized Tröger's base-derived intrinsically microporous polyimide, 6FDA-HTB, were systematically studied. Polyimide samples were heat-treated for 30 min at a fixed temperature to form (i) polybenzoxazole (PBO) by thermal rearrangement (TR) from ∼420 to ∼440 °C, (ii) polymer-carbon transition (PCT) from ∼460 to ∼500 °C, and (iii) early-stage carbon (ESC) membranes from >500 to 600 °C. As frequently observed in previous studies, TR-derived PBO membranes showed an increase in gas permeability with a concomitant decrease in gas-pair selectivity. The intermediate PCT region represents a transition state from a PBO to a partially carbonized polymer with superior properties by showing a simultaneous boost in gas permeability and gas-pair selectivity. The ESC membranes formed between 550 and 600 °C possessed further enhanced selectivity due to tightening of the amorphous CMS structure. A 135-day aged 6FDA-HTB-600 membrane showed very high hydrogen permeability of 3544 barrer coupled with an outstanding H2/CH4 selectivity of 939. The mixed-gas separation properties of selected aged samples, pristine 6FDA-HTB, PBO (6FDA-HTB-420), intermediate PCT (6FDA-HTB-480), and early stage CMS analogs (6FDA-HTB-550 and 600), were investigated using a 1:1 CO2/CH4 feed up to 30 bar. In this series, early-stage CMS membranes displayed the best mixed-gas CO2/CH4 separation properties with performance significantly surpassing the 2018 polymer mixed-gas upper bound.

SIMULATION OF THE PROCESS OF FILLING POLYSTYRENE FOAM FOUNDRY MOLD WITH THE METAL

Modern approaches to prefabrication production consist in the maximum approximation of the shape and size of the blanks to the finished part, which essentially makes the final part cheaper. One of the methods of precision casting is casting in gasified models, or foam models. The basis is the task of developing a theoretical model of filling a polystyrene foam model with liquid metal. The analysis of the process of filling the mold with a gasified model and the process of filling the mold with a closed sprue system are considered. The analysis of the obtained solutions shows that the movement of the metal has the character of aperiodic oscillations. The speed of metal in quantity is maximum at the initial moment of metal processing in the form and happens as it is filled. The pressure of the steam-gas mixture at the initial moment of time exceeds the pressure of the weak metal in the riser, which provides the possibility of metal ejection from the bowl. At the same time, the pressure in the mold cavity changes little with the increase in gas permeability of the mold, which is explained by the small gap between the melting front of the model and the metal mirror. However, with an increase in gas permeability due to a decrease in back pressure, the speed of the metal in the mold cavity and the path traveled by it increase. The analysis of the system of equations allows predicting the behavior of metal during the design of molds for the summer, which reduces the probability of production defects.