Search Results (79)

Meso-scale combustors face persistent challenges in sustaining stable combustion and efficient heat transfer due to high surface-to-volume ratios and attendant heat losses. In contrast, larger outlet diameters exhibit weaker recirculation and more diffused temperature zones, resulting in reduced combustion efficiency and thermal confinement. The behavior of non-premixed flames in meso-scale combustor has been investigated through a comprehensive numerical study, utilizing computational fluid dynamics (CFD) under stoichiometric natural gas (methane)–air conditions; three outlet configurations (6 mm, 8 mm, and 10 mm) were analysed to evaluate their impact on temperature behaviour, vortex flow, swirl intensity, and central recirculation zone (CRZ) formation. Among the tested geometries, the 6 mm outlet produced the most robust central recirculation, intensifying reactant entrainment and mixing and yielding a sharply localised high-temperature core approaching 1880 K. The study highlights the critical role of geometric parameters in governing heat release distribution, with the 6 mm configuration achieving the highest exhaust temperature (920 K) and peak wall temperature (1020 K), making it particularly suitable for thermoelectric generator (TEG) integration. These findings underscore the interplay between combustor geometry, flow dynamics, and heat transfer mechanisms in meso-scale systems, providing valuable insights for optimizing portable power generation devices. Full article

Background: Alzheimer’s disease is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Gamma (γ) oscillations are closely linked to learning and memory, and recent interest has grown around Gamma ENtrainment Using Sensory stimulation (GENUS) as a non-invasive neuromodulation strategy. However, the therapeutic impact of vibrotactile gamma stimulation under varying physical parameters such as acceleration remains underexplored. Methods: Differentiated SH-SY5Y cells were treated with amyloid-β (Aβ) and exposed to vibrotactile stimulation at 2.2 or 4.0 m/s². In vivo, male C57BL/6N mice (7 weeks old, 35 g) were administered scopolamine to induce neurotoxicity and randomly assigned to sham, scopolamine, donepezil, or vibrotactile stimulation groups (n = 10 each). Behavioral tests, biochemical assays, Western blotting, and immunohistochemistry were performed to evaluate cognitive function, oxidative stress, cholinergic activity, synaptic plasticity, and neuroinflammation. Results: In vitro, SH-SY5Y cells exposed to amyloid-beta (Aβ) were treated with vibrotactile stimulation, resulting in enhanced neuronal marker expression at 2.2 m/s². In vivo, mice receiving stimulation at 2.2 m/s² showed improved cognitive performance, reduced oxidative stress, restored cholinergic function, suppressed neuroinflammation, and enhanced synaptic plasticity. Mechanistically, these effects were associated with activation of the AKT/GSK3β/β-catenin pathway. Conclusions: Our findings demonstrate that vibrotactile gamma stimulation at 2.2 m/s² exerts greater therapeutic efficacy than higher acceleration, highlighting the importance of optimizing stimulation parameters. This work supports the potential of acceleration-tuned, non-invasive GENUS-based therapies as effective strategies for cognitive recovery in neurodegenerative conditions. Full article

To mitigate flood damage caused by overflow from a levee, it is essential to prevent the levee failure or extend the time to breaching. Although turfgrass on a levee slope is effective in suppressing erosion, insufficient maintenance can reduce its coverage. When overtopping occurs under such non-uniform turfgrass conditions, the flow tends to entrain air. In spillways, air entrainment is known to reduce friction loss; therefore, it may also contribute to lowering shear stress and erosion depth. This study conducted flume experiments with artificial turf arranged in various patterns on levee slopes to investigate flow patterns, air entrainment, and erosion. The flow pattern changed depending on the turf arrangement and overflow depth, and air entrainment occurred due to water surface fluctuations around the turfgrass. The inception point of air entrainment was found to be similar to or shorter than that observed in stepped spillways. Furthermore, the experiments showed a tendency for erosion depth to decrease once air entrainment is fully developed. This finding is significant because it suggests that erosion can potentially be minimized not only by reinforcing the levee structure itself but also by modifying flow characteristics through designs that promote air entrainment. Full article

To commercialize supersonic and hypersonic passenger aircraft and reusable spaceplanes, we are developing a small-scale supersonic flight experiment vehicle as a flying testbed for technical demonstrations in high-speed flight environments. This experiment vehicle is equipped with a fuel tank and an oxidizer tank, and the propellants inside the tanks slosh due to changes in acceleration during flight. In this situation, there is a risk of gas entrainment during liquid discharge, which could potentially cause an engine malfunction. To avoid such a situation, we considered installing a propellant management device (PMD) inside the tank to suppress the gas entrainment. In this study, a capillary type PMD with a screen channel structure, commonly used in satellites featuring no moving parts, was adopted due to its applicability to a wide acceleration range. The PMD was designed with a structure featuring cylindrical mesh screen nozzles installed at the top and bottom of a cylindrical tank. A one-dimensional flow analysis model was developed taking into account factors such as the pressure loss across the mesh screens and the flow loss within the mesh screen nozzles, which enabled the identification of conditions under which gas entrainment occurred. In this analytical model, separate formulations were developed using Hartwig’s and Ingmanson’s formulas for evaluating the flow losses through the mesh screens. Furthermore, by applying the flow analysis model, the specifications of the mesh screens as key parameters of the PMD, together with the nozzle diameter and nozzle length, were selected. Moreover, we fabricated prototype PMDs with each nozzle and conducted visualization tests using a transparent tank. The tests were conducted under static conditions, where a gravitational acceleration acted downward, and the effects of the cylindrical mesh screen length and discharge flow rate on the free surface height at which gas entrainment occurred were investigated. This experiment demonstrated the effectiveness of the propellant acquisition mechanism of the present PMD. The height of the free surface was also compared with the experimental and analytical results, and it was shown that the results obtained by using Ingmanson’s formula for pressure loss through the screen mesh were closer to the experimental results. These findings demonstrated the validity of the one-dimensional flow analysis model. Full article

The two-phase ejector has gained prominence in heat pump systems as a device that effectively mitigates throttling losses through expansion work recovery. This investigation employs three-dimensional computational fluid dynamics (CFD) simulations to analyze the parametric effects of the mixing channel geometry on the entrainment characteristics in an R410A ejector. After validating the model according to the experimental data, the parameter analysis was carried out, and four key geometric parameters were changed within a certain range: the nozzle exit position (NXP = 13–19 mm), the pre-mixing channel convergent angle (CA = 20–60°), the diameter ratio (DDR = 5.0–7.1), and the length-to-diameter ratio (LDR = 8.9–12.4). Multi-variable optimization studies revealed optimal geometric configurations at NXP = 17 mm (about 3.5D_mix), CA = 30°, DR = 6.4, and LDR = 11.1, yielding an optimized mass entrainment ratio enhancement of 23.6% compared to baseline designs. This research provides actionable guidelines for the design of high-efficiency ejector components for heat pump applications. Full article

The thermally driven ejector refrigeration system is generally used to recover industrial waste heat to improve the energy efficiency of industrial processes. However, for conventional single-stage ejector refrigeration systems (ERSs), the higher-pressure steam derived from high-temperature waste heat elevates the primary fluid pressure, resulting in significant pressure mismatch with the secondary fluid, which consequently leads to large irreversible losses and substantial degradation in system performance. To address this issue, a novel hybrid ejector refrigeration system (NHERS) is proposed and analyzed under design and off-design conditions using thermodynamics. The results indicate that under design conditions, compared to the conventional single-stage ejector refrigeration system, the proposed hybrid ejector refrigeration system can achieve increases of about 20.6% in the entrainment ratio, around 15.2% in the coefficient of performance (COP), and about 21.4% in exergetic efficiency. Analyzing its performance under off-design conditions to provide technical solutions for the flexible operation of the hybrid ejector refrigeration system proposed in this paper can broaden its application scenarios. Consequently, the proposed NHERS demonstrates remarkable superiority in energy conversion and transfer processes, showing certain application prospects in the field of medium- to high-temperature industrial waste heat recovery. Full article

Concrete quality is essential for highway guardrails in mountainous terrain to overcome freeze–thaw cycles, and manufactured sand (MS) concrete is potentially a more sustainable construction material. This paper aims to optimize the mechanical strength and freeze-thaw resistance of MS concrete for highway guardrails. The effects of water-to-binder (W/B) ratio (0.38–0.42), air-entraining agent (AEA) (0–0.5‱), fly ash (FA) (10–30%) and binder contents (360–380 kg/m³) on the properties of MS concrete were investigated. The mechanism behind the factors was further studied with scanning electron microscopy (SEM) and mercury injection porosimetry (MIP). Results showed that increasing W/B ratio, AEA and FA contents led to the reduction of compressive strength, but improved freeze–thaw resistance by reducing the mass loss during the cyclic freeze–thaw. SEM and MIP illustrated that the increase in W/B ratio and AEA addition increased the pore volume and caused a more porous structure, but increasing FA and binder contents densified the structure of MS concrete. This is consistent with the evolution of compressive strength and freeze–thaw resistance. This study offers an optimization method to obtain MS concrete with good compressive strength and freeze–thaw resistance for highway construction. Full article

In this paper, the separation characteristics of mist remover in a wet flue gas desulfurization system are numerically simulated, and the separation mechanism in the channel of mist remover is analyzed considering the influence of droplets on wall recombination, diffusion, and splash. Considering the influence of re-entrainment, a gas–liquid separation model was established to reflect the coupling effect of air flow, droplets, and liquid film in the process of defogging. A computational model based on the energy loss coefficient κ was established, and the numerical simulation of flue gas flow in a single channel of a baffle demister was carried out using the computational fluid dynamics method. The effects of plate distance, plate angle, droplet diameter, and flue gas velocity on the separation efficiency were simulated and analyzed. Based on the response surface method, the model for separation characteristics and structure optimization design of the demister is established, and the influence level of each factor is analyzed. Full article

Artificial upwelling (AU), a geoengineering technique aimed at transporting nutrient-enriched deep-sea water to the sunlit surface layers through artificial systems, is increasingly recognized as a promising approach to enhance oceanic fertility and stimulate primary marine productivity, thereby bolstering the ocean capacity for carbon sequestration. Several air-lifted AU systems have been implemented in countries such as Norway and China. However, research on the optimization of the air injection pipeline network (AIPN)—a critical component of the air-lifted AU system—remains limited. This paper introduces a refined minimum spanning tree algorithm to propose a novel approach for optimizing the AIPN. Furthermore, the bubble-entrained plume loss rate (N_BEP) is developed as a model to assess the efficiency of air-lifted AU systems, which is applied to three case studies involving air-lifted AU systems of varying scales. The findings indicate that the enhanced minimum spanning tree algorithm outperforms the conventional Prim’s algorithm, leading to an average 87% reduction in N_BEP of the optimized AIPN, compared to the AIPN of previous air-lifted AU systems while improving system stability. Consequently, the proposed optimization method for AIPN offers valuable scientific and practical insights for the engineering design of the air-lifted AU systems across diverse scales, offering transformative potential for large-scale carbon sequestration and marine productivity enhancement. Full article

Equations are developed for the relative sliding velocities, entrainment velocities, forces, friction coefficients, effective radius of curvature, oil film thickness, friction loss, and meshing efficiency for a novel closed movable tooth gear reducer. Using these equations, the relative sliding velocities and entrainment velocities of the reducer are studied. The meshing efficiencies and their changes along with meshing positions and main parameters are analyzed. Changes of the meshing efficiencies along with load torque are also studied. An efficiency experiment of the reducer prototype is carried out. Results indicate that the meshing efficiency of the novel closed reducer increases with increasing eccentric distance. When an error in the eccentric distance occurs, the meshing efficiency is significantly reduced. The measured efficiency is close to the calculated one, supporting the theoretical studies. Full article

Cemented Sand, Gravel, and Rock (CSGR) dams have traditionally used either Conventional Vibrated Concrete (CVC) or Grout-Enriched Roller Compacted Concrete (GERCC) for protective and seepage control layers in low- to medium-height dams. However, these methods are complex, prone to interference, and uneconomical due to significant differences in the expansion coefficient, elastic modulus, and hydration heat parameters among CSGR, CVC, and GERCC. This complexity complicates quality control during construction, leading to the development of Grout-Enriched Vibrated Cemented Sand, Gravel, and Rock (GECSGR) as an alternative. Despite its potential, GECSGR has limited use due to concerns about freeze–thaw resistance. This project addresses these concerns by developing an air-entrained GECSGR grout formulation and construction technique. The study follows a five-phase approach: mix proportioning of C₁₈₀6 CSGR; optimization of the grout formulation; determination of grout addition rate; evaluation of small-scale lab samples of GECSGR; and field application. The results indicate that combining 8–12% of 223 kg/m³ cement grout with 2–2.23 kg/m³ of admixtures, mud content of 15%, a marsh time of 26–31 s. and a water/cement ratio of 0.5–0.6 with the C₁₈₀6 parent CSGR mixture achieved a post-vibration in situ air content of 4–6%, excellent freeze–thaw resistance (F300: mass loss <5% or initial dynamic modulus ≥60%), and permeability resistance (W12: permeability coefficient of 0.13 × 10⁻¹⁰ m/s). The development of a 2-in-1 slurry addition and vibration equipment eliminated performance risks and enhanced efficiency in field applications, such as the conversion of the C₁₈₀4 CSGR mixture into air-entrained GECSGR grade C9015W6F50 for the 2.76 km Qianwei protection dam. Economic analysis revealed that the unit cost of GECSGR production is 18.3% and 6.33% less than CVC and GERCC, respectively, marking a significant advancement in sustainable cement-based composite materials in the dam industry. Full article

Complex harvesting environments and varying crop conditions often lead to threshing cylinder blockage and increased entrainment loss in maize grain harvesters. To address these issues, an electric-driven automatic control system for maize threshing concave clearance based on real-time entrainment loss monitoring was developed. The system automatically adjusts concave clearance parameters at different harvesting speeds to maintain grain entrainment loss within an optimal range. First, an adjustable concave structure based on a crank-link mechanism was designed, with a threshing clearance adjustment range of 15–47 mm and motor rotation angle of 0–48°. Subsequently, an EDEM simulation model of the mixed material discharge inside the threshing cylinder was established to determine the optimal installation position of the entrainment loss monitoring sensor based on piezoelectric ceramic-sensitive elements. The sensor was positioned at the left tail end of the concave sieve, with a minimum distance of 58 mm between the sensitive plate centerline and threshing concave sieve and an installation angle of 65° relative to the horizontal plane. A maize threshing clearance control method based on fuzzy neural network PID control algorithm was proposed, and Simulink simulation optimization verified its superior performance with fast response speed. After system integration, field trials were conducted at low, medium, and high operating speeds with preset ideal entrainment loss intervals. The results showed that control was unnecessary at low speed, the control system-maintained entrainment loss within set range at medium speed, and maximum threshing clearance was needed at high speed. Finally, comparative trials of threshing performance with and without the control system were conducted at medium harvesting speed. Results showed that the entrainment loss rate decreased by 43.75% with the control system activated, significantly reducing maize threshing entrainment losses. This study overcame the barrier of maize threshing parameter adjustment being heavily reliant on manual experience and provided theoretical support for the intelligent grain harvesting equipment. Full article

As rice yield rises, the issue of broken axis windings in mature rice threshing drums is becoming increasingly severe. To disclose the winding characteristics and signal traits of the drums during the threshing process of mature rice, this paper undertakes an analysis of the winding characteristics and signals of the drums in rice with the assistance of a vibration test and analysis system. Since rice can lead to drum winding and shaft breakage, this paper alters the driving mode of the drums to exhibit the influence of rice on them. Firstly, the transfer characteristics of the frame need to be studied and analyzed, followed by subsequent research. The test results indicate that the horizontal displacement of the cylinder axial trajectory rises with the growth of the transmission chain, while the vertical displacement drops with the growth of the transmission chain. Additionally, to investigate the effect of mature rice on the threshing performance of horizontal axis II and horizontal axis III, a control variable method was employed. This approach allowed for the observation of how mature rice influences the threshing roller by systematically adjusting both the threshing gap and the rotational speed of the roller. It can be discerned from the test results that with the reduction of the threshing gap of affected mature rice, the unstripped rate gradually declines, while the entrainment loss rate gradually increases. As the rotational speed of horizontal shaft roller III increases, the rate of uncleared material gradually decreases, while the rate of entrainment loss progressively rises. The research findings can furnish a reference for the winding characteristics of rice on rollers and the enhancement of vehicle driving comfort. Full article

The integrated gasification combined cycle is a relatively new and eco-friendly power generation technology. However, this process produces coal gasification slag (CGS) as a by-product, which is usually landfilled or discarded. To enable efficient recycling of CGS, this study investigated the effects of using pretreated CGS as a fine aggregate on the quality and durability of concrete. A pretreatment system comprising sieve screening, size reduction, and wet flotation processes was devised. Experiments were conducted to evaluate the properties and durability of concrete prepared using mixtures of pretreated or non-pretreated CGS, ordinary Portland cement, crushed gravel, and crushed sand (CS). The results demonstrate that pretreated CGS (P_CGS) reduces the amounts of water-reducing and air-entraining agents required. In particular, it reduces the losses of air content induced when using CGS. P_CGS effectively increases the compressive strength of concrete; however, the strength decreases by 8–10% if the CGS content is >50%. P_CGS exhibits durability similar to that of commonly used CS, indicating its potential applicability as a valuable recycled construction material and safe aggregate for enhancing concrete durability. Full article

The gas–liquid Venturi injector has been widely applied in industrial production due to its advantages of high entrainment and low energy consumption. In this study, Computational Fluid Dynamics (CFD) was employed to investigate the effect of the gas–liquid interface structure within the mixing section on entrainment behavior by varying the geometry of the mixing section during gas–liquid coaxial flow. The simulation results indicate that along the jet direction, the gas–liquid interface generally transitions from a smooth cylindrical shape to a lobed structure in the mixing section. Surface waves mainly appear in the lobed region. Furthermore, lobed and surface wave structures reduce pressure loss and enhance entrainment. Additionally, the study found that longer mixing sections enhance entrainment under low flow resistance. This study provides valuable insights for achieving high jet entrainment and offers supplementary research on gas–liquid interface structures in jets constrained by solid boundaries. Full article