Air Foam Research Articles

Stability mechanism of viscoelastically enhanced surfactant air foam for low permeability reservoir

Polymer has been widely studied as an effective means to improve foam stability in reservoir exploitation. Nevertheless, the deployment of this technology in low-permeability reservoirs may prove challenging and could potentially result in formation damage. The innovation of this study is the utilization of viscoelastic surfactants to create enhanced air foam with wormlike micelles and three-dimensional network structures. This can result in a synergy between the properties of fluidity control and oil washing efficiency, thereby enhancing the strength of the foam. The supramolecular self-assembly property facilitates the injection of the foam into the formation while preserving its original structure and properties, thereby enhancing the stability of the foam and markedly improving the recovery of low permeability reservoirs. The viscoelastically enhanced air foam system is composed of the zwitterionic surfactant erucylamido propyl betaine (EHSB) and the anionic surfactant sodium dodecyl sulfate (SDS), which has been designated EHSB-SDS. The foam performance was evaluated using the Waring Blender method and rheological behavior, with foam fluid viscosity, initial foam volume (V0), half-life for drainage (td) and foam half-life (tf) serving as the evaluation indicators. The influence of temperature, salinity and oil content on foam performance is considered to explore the reservoir adaptability. The dynamic/micro stability, macro rheological properties, interfacial viscoelasticity and Zeta potential of the enhanced air foam system were further studied to clarify the stability mechanism of enhanced air foam system. The td, tf and composite index of EHSB-SDS is 56.6 min, 36 h and 648000 mL·min, respectively. The viscoelastic surfactants form wormlike micelles, which increase the foam solution viscosity. This results in a slow drainage speed and the rupture of the bubbles. The adsorption of surfactant at the gas/liquid interface results in an increase in surface activity, interfacial expansion modulus and zeta potential, which serves to enhance the strength of the liquid film and the electrostatic repulsion among bubbles. These three factors are primarily responsible for the stability of the foam. The research establishes a theoretical basis for the effective development of low permeability reservoirs and new foam flooding technology.

DEVELOPMENT OF A TEST SAMPLE OF A SYSTEM FOR GENERATING AND SUPPLYING COMPRESSED AIR FOAM

An effective fire extinguishing agent for class A fires is the compressed air foam formed in Compressed Air Foam Systems (СAFS). Such systems have become widespread in leading countries such as the USA, Germany, China, and others. It is worth noting that the technical parameters of CAFS (intensity and consumption of an aqueous solution of foaming agent/air), implemented in the practice of fire extinguishing in the form of industrial samples, are designed and manufactured in such a way as to ensure effective extinguishing of developed fires of a significant area. When using existing samples for obtaining compression foam, a problem arises, which lies in the limited possibilities of regulating the supply of compression foam (intensity and consumption of the aqueous solution of the foaming agent/air), under which it is possible to use it with modified additives when extinguishing laboratory fires of solid combustible materials, and the lack of a smooth regulation of its supply. As a result of the research, the authors proposed a compressed air foam system to study its properties with the content of modified additives when changing the composition of the liquid and air that make it up. The manufactured system has the following parameters: multiplicity of 4–20, working pressure of systems of 4–8 bar, smooth adjustment of the consumption of aqueous solution/foaming agent of 2–20 l/min, and smooth adjustment of gas fraction consumption of 8–450 l/min. In particular, it is possible to adjust the consumption of the aqueous solution of the foaming agent and air, to work in dependant and autonomous mode, to regulate the intensity of the foam supply using nozzles of different diameters, and to change the porosity of the porous body in the foam generator. Further, we developed a system for measuring the flow of aqueous solution and air, which is a hardware and software complex. The system allows saving the measurement results to a PC in the form of an Excel spreadsheet for further development of dependencies and simultaneously displaying the flow rate of the aqueous foaming agent solution and air on the display screen and PC in real-time. Keywords: compressed air foam, class A fires, compressed air foam systems, modified additives.

X-ray microstructural insight into the mechanical behaviour of ligth-weight cemented soils

Light-weight cemented soils (LWCS) – that is, materials prepared by mixing natural soil, water and cement with air foam, are characterised by a heterogeneous microstructure, consisting of large foam-induced voids distributed in a cemented porous matrix. The reduced volume weight coupled with a good mechanical strength makes LWCS suitable for many geotechnical applications. However, the role of the microstructure on their macroscopic mechanical behaviour is not completely clear. A novel experimental investigation on the mechanical response of LWCS under triaxial loading paths using in situ x-ray microtomography is presented here, focusing on the evolution of foam-induced porosity. The tomographies are acquired during the shear phase of multiple triaxial compression tests, performed at different confining stress levels. Image analysis is employed for obtaining porosity maps and incremental strain fields of the samples. At low confining stress, the sample deformation essentially consists in the progressive opening of sub-vertical dilatant fractures connecting the foam-induced voids. At higher confining stresses, localised compactions develop in the cemented matrix along the directions coherent with the deviatoric load path. The results presented above indicate that the deformation and failure mechanisms of LWCS strongly depend on the mean stress level.

Influence of modified additives on the properties of compressed air foam

The object of this study is the properties of compressed air foam with the use of modified additives: its drainage time and expansion ratio. The main properties of compressed air foam that affect the effectiveness of fire extinguishing are its drainage time and expansion ratio. At the same time, a number of authors have confirmed that the introduction of chemically modified additives into the composition of water fire extinguishing substances makes it possible to increase the effectiveness of fire extinguishing. The problem to be solved was to determine the influence of five modified additives (NH4)2HPO4, NH4H2PO4, (NH4)2СO3, K2CO3 and KCl in the concentration range of 1–5 % by mass on the expansion ratio and drainage time of the compressed air foam. The results showed that the content of additives (NH4)2HPO4, NH4H2PO4 and (NH4)2СO3 in the aqueous solution of the foaming agent does not affect its expansion ratio within the given limits. On the other hand, with K2CO3 and KCl additives, it was not possible to obtain compressed air foam with a expansion ratio of 5–20, that is, their inefficiency in compressed air foam was noted. The characteristic dependence of the effect of (NH4)2HPO4, NH4H2PO4 and (NH4)2СO3 additives on drainage time has been determined. The greatest drainage time is characteristic of the K≈20 generation mode. The highest recorded drainage time index was established for NH4H2PO4, namely 5.45 min; for (NH4)2HPO4 the drainage time was lower by 8 %; for (NH4)2СO3 the drainage time was lower by 20 %. At the same time, with the use of (NH4)2HPO4, NH4H2PO4 and (NH4)2СO3, it is characteristic to obtain a foam with lower drainage time compared to foam of a conventional composition. Thus, for foam with a expansion ratio of K≈20, the drainage time of foam with NH4H2PO4 is lower by 17 %, with (NH4)2HPO4 by 23 %, and with (NH4)2СO3 by 33 %. The effect of reducing the drainage time of the foam can have a decisive role in reducing its effectiveness when used for extinguishing flammable liquids due to the extinguishing mechanism but is not decisive for extinguishing solid substances. Therefore, the fire-extinguishing effectiveness of compressed air foam with modified additives during the extinguishing of solid combustible materials in comparison with the conventional CAF composition requires further study

Numerical Simulation of Internal Flow Field in Optimization Model of Gas–Liquid Mixing Device

This article studies the influence of structural parameters of the optimization model for the gas–liquid mixing device of a fire truck (compressed air foam lift fire truck, model JP21/G2, made in China) on the liquid phase volume fraction, static pressure, velocity streamline, and the influence of smaller flow rates on the mixing effect. By using the computational fluid dynamics (CFD) software FLUENT 2021 R2, numerical simulations were conducted on the fluid domain model of the gas–liquid mixing device of the JP21/G2 fire truck. The changes in the mixing effect time dimension, liquid phase volume fraction, static pressure, and velocity streamline inside the gas–liquid mixing device were obtained. The optimal mixer structure combination in practical applications was inferred through orthogonal experiments, and the influence of flow rate on the optimal pipe diameter and shortest mixing distance was obtained through variable flow rate simulation experiments. The numerical simulation results show that the presence of bent pipes in the JP21/G2 real vehicle model hinders the gas–liquid mixing process. A straight pipe section of at least 8 m was added after the bent pipe to ensure the mixing effect. The optimal parameter combination for orthogonal experiments had an accurate value of 50°-50°-220 mm. Under the same pipe diameter, using a larger flow rate can achieve better mixing effects.

Multi-scale experimental study on properties of compressed air foam and pressure drop in the long-distance vertical pipe

Compressed air foam has been gradually applied in super high-rise buildings due to its high extinguishing efficiency and great transportation ability. However, the transport characteristics of compressed air foam are unclear because the foam is a complex gas-liquid two-phase fluid. In this study, multi-scale experiments were conducted to investigate the foam properties of compressed air foam and pressure drop in the long-distance vertical pipe. The results show that the foam is compressed as a whole when pressure increases, resulting in a significantly increased foam density. At higher pressures, the bubble coarsening degree decreases, accompanied by a narrower particle size distribution and an increased foam size homogenization. Moreover, a critical pressure phenomenon is observed in foams with different foam expansion ratios. The average foam diameter stabilizes gradually with pressure changes after exceeding the critical pressure. A theoretical model for foam density is developed, considering various pressures, temperatures and foam expansion ratios. When the compressed air foam is transported in the vertical long-distance pipe, the pressure decreases in a slightly downward curve, which is due to the decrease in foam density. Finally, a prediction model for the pressure drop of compressed air foam in the long-distance vertical pipe is proposed, which considers changes in foam density. The accuracy of the prediction model is verified by the multi-scale experimental results. The results deepen the understanding of foam flow in the long-distance vertical pipe and provide useful guidance for applications of compressed air foam in super high-rise buildings.

Bio‐Based Foams to Function as Future Plastic Substitutes by Biomimicry: Inducing Hydrophobicity with Lignin

To replace common plastics, bio‐based alternatives are needed. Cellulose foams, as plant‐based materials, are the most attractive solution, being often biodegradable and inexpensive and having the potential for distributed production. Cellulose and its derivatives, as raw materials, present a fundamental challenge, as they are hydrophilic. Herein, this problem is solved by drawing inspiration from the hydrophobic barrier that lignin creates in wood and applying lignin to methylcellulose (MC) foams. The lignin (0.0–1.0 wt% being the range studied here) is applied directly to the suspension consisting of water and MC (1.8 wt%), which is then foamed and solidified to a dry 3D porous structure. By comparing different types of lignin and the resulting surface morphologies, it is shown that organosolv lignin (OL) most strongly self‐assembles to the air–foam interfaces, achieving area fractions up to 27%. Using different concentrations of OL, how hydrophobicity—described by the initial water contact angle and its time evolution—increases with increasing lignin concentration is then shown. Thus, significantly increased water resistance (up to 91 times higher compared to the pure MC foam), a crucial property for developing novel bio‐based materials that can compete with traditional plastics, is able to be achieved.

Air‐laid and foam‐laid nonwoven composites: The effect of carrier medium on mechanical properties

AbstractThermoplastic nonwoven composites were produced with the air‐laying and foam‐forming processes from cellulosic and plastic fibers. The two raw material combinations were (1) PP/PE (fiber length 3 mm), PP/PE (12 mm), fluff pulp fibers (2 mm) and (2) PP/PE (3 mm), fluff pulp fibers, viscose (10 mm). After forming, the fibrous sheets (400 gsm) were bonded with heat pressing (145°C). The effect of the carrier medium, air or aqueous foam, on the tensile and impact properties and sheet structure was explored. The air‐laids differed from the foam‐laids by sheet anisotropy, density, and the lack of an additional bonding regime between wood fibers due to the dry forming process. The PP/PE bonding fibers gave the air‐laids a good capacity to elongate compared to the foam‐laids. The advantage was lost when nonbonding viscose was added. The impact strength was dependent on the PP/PE dosage and the sheet density, rather than the moisture‐induced bonding between wood fibers. The changing long/short fiber ratios caused gradual shifts in sheet properties, usually a reduction in a mechanical property as the share of short fiber increased in the mix. Economic analysis revealed that increasing fluff content can reduce raw material costs, providing a possibility for cost optimization in total production costs.

Effect of the foam flow rate on extinguishing process for low-expansion foam AFFF, FP, and S based on CAF system

Compressed air foam (CAF) system has been proposed as an excellent method for fighting liquid fuel fires, where the foam flow rate is the critical factor in determining the efficiency. However, the existing research of the effect of foam flow rate on CAF system limited to extinguishing time, while ignoring the detailed quantitative study on some characteristic parameters during the extinguishing process, particularly the flame height. Aiming at investigating the influence of foam flow rate on these parameters, a series of CAF extinguishing tests were carried out in the range of different foam flow rates from 10 to 80 L/h. Results indicate that with an increase in the gas–liquid ratio, the extinguishing time for AFFF, FP, and S initially decreases by 69.9 %, 47.1 %, and 59.0 %, respectively. This reduction continues until reaching a minimum at a gas–liquid ratio of 10:1. When foam is released onto the fuel surface at a low flow rate of 10 L/h, flame height increases rapidly by approximately 50 to 100 mm caused by air entrainment, whereas at a higher flow rate of 45 L/h, this parameter decreases quickly over time. Further, the extinguishing time decreases gradually with increasing foam flow rate, dropping from over 100 s to around 30 s in the range of 10 to 80 L/h. Based on experimental data of this study, the extinguishing time model on foam flow rate has been developed for typical foam of AFFF, FP and S. The findings of this study provide valuable insights for optimizing the effective utilization of the CAF system.

Study on Gas-Liquid Coaxial Jet Foam Generator and Its Foaming Characteristics.

In order to solve the difficulty of the existing compressed air foam system with low FER and difficult in having both the FER and range. A new type of foam generator for CAFS was designed, an air-liquid coaxial foam generator, which produces foam with high FER (the ratio of the foam volume to the volume of the foam solution) and large output momentum. In this paper, experiments on the foam production performance of a gas-liquid coaxial jet foam generator were carried out with different parameters, such as liquid flow rate, gas flow rate, and foam output end diameter. The variation of FER, foam half-life, range, foam volume, and compressed air utilization rate with the experimental parameters were analyzed. The results show that the foaming performance of the foam generator tends to rise in the range of 8-12.4 m3/h at a fixed gas flow rate, the FER and foam half-life are negatively related to it, and the foaming performance tends to decrease in the range of 12.4-18 m3/h. The best foaming performance was achieved when the liquid volume of the foam generator was 12.4 m3/h. For the liquid volume value in different intervals, the foaming performance varies with the air supply volume. When the liquid volume is higher than 12.4 m3/h, increasing the air supply volume is beneficial to improve the foaming performance, and when the liquid volume is lower than 12.4 m3/h, increasing the air volume does not improve the foaming performance. The effect of the diameter of the foaming chamber on the foaming performance is not monotonic, and an optimum value exists. Compared with similar devices, the gas-liquid coaxial jet foam generator has strong advantages in FER and range and has better application prospects for fire control in restricted spaces.

Evaluation of a compressed air foam system to clean quail rearing facilities

Evaluation of a compressed air foam system to clean quail rearing facilities

Experimental and numerical study on the pressure drop and flow pattern of liquid foam in a foam generator

In the present study, a comprehensive analysis of the pressure drop, flow pattern, and foam structural properties of vertical upward two-phase flow in a Kenics static foam generator of a compressed air foam system was carried out. A liquid with an extremely low surface tension (16.5 mN/m) was used for making the foam. The effects of the number of elements (number of individual elements combined into the mixer), aspect ratio (the ratio of length to diameter of each element), and transition angle (transition angle between elements) of the Kenics mixers on the pressure loss during foam generation were studied in detail over a wide range of Reynolds numbers through experiments and numerical simulation. A new pressure drop correlation was successfully obtained by scaling analysis and the modified Lockhart–Martinelli correlation was proposed to describe the pressure drop during foam generation. Furthermore, the experimental results validated the proposed correlation and exhibited good reliability and predictive accuracy. Finally, four flow patterns for foam generation in vertical pipes that were different from the classical gas–liquid two-phase flow patterns were proposed, and the relationships among the pressure drop, flow pattern, and foam structural properties were explored. This research expands the study of foam generation in vertical tubes containing a built-in spiral structure with low flow resistance. It provides new insights and guidance for developing continuous foam manufacturing.

Design of fluorine-free foam extinguishing agent with high surface activity, foam stability and pool fire suppression by optimization of surfactant composition and foam system

To meet the environmental requirement of foam extinguishing agent, a novel fluorine-free surfactant named amino-terminated polyether modified silicone (ATPMS) was successfully synthesized, and then in combination with hydrocarbon surfactant prepared fluorine-free foam extinguishing agent. The study carefully investigated surface tension, foamability, foam stability and fire extinguishing performance of fluorine-free foam extinguishing agent. The results indicate that ATPMS has a low surface tension of 21.17 mN/m, which combined with hydrocarbon surfactant at the mass concentration ratio of 1:1 imparts high surface activity. The sodium lauryl ether sulfate (AES)/ATPMS system owes the optimal comprehensive performance with an initial foam height value of 85.8 mm, a surface tension value of 24.76 mN/m and a foam stability value (the ratio of foam height between initial foam and five-minute foam) of 64.0 % at critical micelle concentration (CMC), respectively. Fire suppression test shows that the obtained fluorine-free foam extinguishing agent is effective in fighting diesel pool fires. The firefighting efficiency of foam agent links to the mixing chamber structure of compressed air foam fire extinguishing system (CAFS). When the mixing chamber of CAFS has a recurrent segment length of 50 mm and the filled particle size of 10 mm, the firefighting efficiency of fluorine-free foam extinguishing agent is optimal with a fire extinguishing time of 33 s and a temperature drop rate of 6.49 °C/s.

Performance improvement of photovoltaic-thermal collector equipped with copper metal foam air channel

ABSTRACT Avoiding high temperatures in photovoltaic cells with appropriate cooling is necessary to increase their conversion efficiency. Passive cooling systems using metal foam in the air channel were investigated, but an overall assessment is necessary for its viable application. In this numerical study, the thermal, electrical, and exergy efficiencies, as well as the entropy generation of a PVT are analyzed in the presence of copper metal foam in the air channel. The investigation is performed using a CFD code based on the pressure-based finite volume method. The non-Darcy effects of the porous foam are taken into account. Validation of the numerical model is made by comparison of the numerical predictions with experimental results of the literature. The outcomes indicate that varying the porosity from 1 to 0.89 increases the thermal energy, electrical energy, and exergy efficiency from 44.50% to 67.01%, 10.64% to 11.54%, and 12.01% to 13.19%, respectively, while the entropy generation decreases from 1.3116 W/K to 1.2942 W/K. Furthermore, the optimum thickness of the cooling channel is determined (30 cm for 0.93 copper foam porosity).

Study on an all-in-one foaming agent with corrosion inhibition for air foam flooding

Abstract Foam has been widely used in drilling, well washing, and oil driving during the development of oil and gas fields. Although air foams have been successfully employed as an enhanced oil medium, the oxygen they contain can seriously corrode piping systems, which can have a negative influence on output. This work used a combination of sodium dodecyl sulfate (SDS), dodecyl aminopropyl betaine (LAB), sodium dodecylbenzene sulfonate (SDBS), and cosurfactants to solve the problem above. The corrosion inhibitor hydrazine hydrate (N₂H₄·H₂O) was added as corrosion inhibitor. The foaming (air)-corrosion inhibitor all-in-one (SLN) was obtained with the formulation of SDS: LAB: N₂H₄·H₂O = 8:2:4. The foam volume of 0.7 % SLN was measured to be 515 mL at room temperature with a half-life of 4.1 min using the stirring method. The initial foam height of this all-in-one agent was measured to be 15.6 cm at 30 °C using the Roche foaming method. The foam height was still maintained at 15.5 cm after 20 min with a foam height retention of 99.2 %. The foam height retention rate was 50.0 % at 70 °C. Moreover, the formulation had good salt resistance to common inorganic salts in oilfield water. It should be emphasized that the SLN all-in-one agent has strong corrosion inhibition performance, and the corrosion inhibition rate can reach up to 96.9 %. The surface tension of this SLN all-in-one agent was reduced to 27.8 mN m−1 at a concentration of 0.1 %. It indicated that the all-in-one agent might increase the stability of the foam by decreasing the surface tension, thus improving the persistence of the foam and the effect of the repelling oil.

Macroscopic behavior and microscopic structure of serpentine-MgO carbon sequestration foamed concrete

This paper proposes a novel approach for preparing foamed concrete that involves the substitution of Portland cement with serpentine wastes and magnesium oxide (MgO), along with the utilization of carbon dioxide (CO2) foam instead of air foam. The existence of CO2 foam promotes the dissolution and carbonation of MgO and serpentine. Six distinct sample groups with varying serpentine proportions ranging from 0% to 50% were meticulously prepared. The incorporation of serpentine enhanced the sample fluidity and prolonged the sample setting time. The results demonstrated that the serpentine-MgO samples achieved the highest unconfined compressive strength (1.4 MPa) at a serpentine proportion of 30%, and excessive serpentine content negatively influenced the mechanical performance and microstructure development. The improvements in carbonates content, morphologies and microstructure in samples containing 30% serpentine proved the low-carbon potential of the proposed approach. Overall, serpentine-MgO carbon sequestration foamed concrete (SC-FC) could emerge as a promising sustainable construction material for CO2 sequestration.

Investigations into magnesium oxide carbon sequestration foamed concrete: Mechanical performance, microstructure and environmental benefits

This paper proposes an innovative preparation measure for magnesium oxide (MgO)-based foamed concrete. Carbon dioxide (CO2) foam has been introduced into the sample as a substitute for air foam, resulting in a novel formulation referred to as MgO carbon sequestration foamed concrete (MCFC). This innovation facilitates the setting and hardening of MgO-based foamed concrete under ambient conditions. Basic mechanical properties were tested at three different ages. At the age of 28 days, the resultant MCFC has demonstrated mechanical performance comparable to conventional Portland cement-based foamed concrete including unconfined compressive strength and stain-stress behavior. Through SEM NMR and X-ray CT, the MCFC sample exhibited an increasingly compact matrix and an evolving distribution of pore structure as time progressed. Furthermore, a comprehensive life cycle assessment has revealed that MCFC has the potential to reduce carbon emissions by up to 50% when compared to conventional cement-based foamed concrete. The results imply that MCFC presents itself as a viable alternative to conventional PC-based foamed concrete, offering equivalent mechanical performance while delivering superior environmental advantages for engineering applications.

Experimental investigation of flow patterns and rheological characteristics of compressed air foam in horizontal tube

The use of compressed air foam (CAF) for fire suppression has undergone rapid development in recent years. It has been successfully applied in fire incidents in the petroleum and chemical industries. The increasing need to fighting fires at high elevations necessitates an understanding of the rheological characteristics, pressure gradient changes, flow characteristics, and regularities of CAF within long firehoses. Therefore, this paper focuses on an investigation of the flow characteristics of CAF at foaming agent concentrations ranging from 0.1% to 1.2% and gas–liquid ratios ranging from 5 to 25. Specifically, it explores foam characteristics, pressure loss, and the relationship between flow rate and foaming agent concentration. The findings reveal that CAF exhibits four flow patterns: wave flow, elastic flow, ring flow, and dispersion flow. For most CAF firefighting applications, a foaming agent concentration of 0.3%–0.5% and a gas–liquid ratio of approximately 10 are suitable. However, for fire isolation purposes, a foaming agent concentration of 0.7%–1.0% and a gas–liquid ratio of over 15 should be employed. By utilizing a power-law rheological model and an experimental regression method, a prediction model is obtained for the flow characteristics and pressure loss of CAF in pipelines. The predictions of the model exhibit an error of less than 10% when compared with experimental results, validating the model. The results of this study provide a theoretical basis and technical support for understanding liquid supply resistance loss, which is crucial for maximizing firefighting effectiveness.

Experimental investigation into the self-carbonation mechanism of magnesium oxide carbon sequestration foamed concrete

A novel technique involves the preparation of foamed concrete utilizing MgO as a substitute for Portland cement (PC) and CO2 foam in place of air foam. This technique is referred to as “magnesium oxide (MgO) carbon sequestration foamed concrete (MCFC)" that enables self-carbonation of Reactive MgO cement-based concrete under ambient conditions without any accelerated carbonation curing conditions. The developed technology enhances the carbonation efficiency of MgO-based materials by combining a foaming agent with CO2 curing. The even mixing of CO2 foam with MgO, referred to the uniform distribution and incorporation of CO2 throughout the sample, facilitated by the foaming agent, leads to the production of ions within the cement, promoting the carbonation of dissolved Mg2+ ions and the formation of hydrated magnesium hydroxyl carbonates (HMHCs). Eight sample groups were prepared to explore the potential of MCFC in CO2 sequestration. XRD, TG-DTA, and SEM techniques were employed to investigate the mineral phase and carbonation products in MCFC. The pore structure, pore-size distribution, and porosity of MCFC under different curing conditions were investigated using X-ray and NMR. The self-carbonation enabled by CO2 foams improved the microstructure and mechanical performance of MgO-based samples. Notably, the morphology, microstructure, and carbonate content improvements resulted in a significant 100% increase in the 28-day compressive strengths (2 MPa) compared to the control sample cured under ambient conditions.

Wood stack fire tests to evaluate the influence of extinguishing medium and driving pressure on fire extinguishing efficacy of forest trees

In order to explore efficient fire extinguishing agents for forest fires and further enhance fire prevention and extinguishing technology, an outdoor fire extinguishing test platform for burning wood stacks is constructed to simulate fire extinguishing scenarios in an open-air environment. Comparative analysis of fire extinguishing performance of hydrogel extinguishing agent and compressed air foam (CAF), and exploring cooling effect of fire extinguishing agent on internal high temperature of wood stacks under three driving pressures of 0.45 MPa, 0.55 MPa and 0.65 MPa. Test results show that both hydrogel extinguishing agent and CAF can effectively extinguish woodpile fires. Hydrogel fire extinguishing agents are more efficient in extinguishing fires by comparing extinguishing time and agent dosage. CAF in the early stages of firefighting, there is a momentary enhancement of flame, which leads to an increase in temperature of wood stacks and heat radiation fluxes. In contrast, hydrogel fire extinguishing agents can quickly reduce temperature and heat radiation flux of wood stacks, and cooling effect is significant; When driving pressure is increased from 0.45 MPa to 0.65 MPa, the flame extinguishing time gradually decreases. Analyzing cooling capacity in terms of consumption of extinguishing agent, hydrogel extinguishing agent increases about 40 %, while cooling capacity of CAF increases only about 22 %; Hydrogel's cooling efficiency is better than CAF, and increasing driving pressure helps to improve agent cooling efficiency. Among them, CAF needs to be within a specific gas driving pressure range, which can minimize negative effect of gas driving pressure and enhance its cooling efficiency.