Search Results (400)

In response to the need for separation and utilization of residual film mixtures after transformation of protaetia brevitarsis larvae, a pneumatic drum-sieve-type separator for transforming mixtures of protaetia brevitarsis larvae was designed. First, the suspension velocity of each component was determined by the suspension speed test. Secondly, the separation process of residual film, larvae, and insect sand was formulated on the basis of biological activities, shape differences, and aerodynamic response characteristics. Eventually, the main structural parameters and working parameters of the machine were determined. In order to optimize the separation effect, a single-factor experiment and a quadratic regression response surface experiment containing three factors and three levels were carried out, and the corresponding regression model was established. The experimental results showed that the effects of the air speed at the inlet, inclination angle of the sieve cylinder, and rotational speed of the sieve cylinder on the impurity rate of the residual film decreased in that order, and that the effects of the rotational speed of the sieve cylinder, inclination angle of the sieve cylinder, and air speed at the inlet on the inactivation rate of the larvae decreased in that order. Through parameter optimization, a better combination of working parameters was obtained: the rotational speed of the sieve cylinder was 24 r/min, the inclination angle of the sieve cylinder was −0.43°, and the air speed at the inlet was 5.32 m/s. The average values of residual film impurity rate and larval inactivation rate obtained from the material sieving test under these parameters were 8.74% and 3.18%, with the relative errors of the theoretically optimized values being less than 5%. The results of the study can provide a reference for the resource utilization of residual film and impurity mixtures and the development of equipment for the living body separation of protaetia brevitarsis. Full article

The use of 3D printing holds significant promise to transform the construction industry by enabling automation and customization, although key challenges remain—particularly the control of fresh-state rheology. This study presents a novel formulation that combines potassium-rich biomass fly ash (BFAK) with an air-entraining plasticizer (APA) to optimize the rheological behavior, hydration kinetics, and structural performance of mortars tailored for extrusion-based 3D printing. The results demonstrate that BFAK enhances the yield stress and thixotropy increases, contributing to improved structural stability after extrusion. In parallel, the APA adjusts the viscosity and facilitates material flow through the nozzle. Isothermal calorimetry reveals that BFAK modifies the hydration kinetics, increasing the intensity and delaying the occurrence of the main hydration peak due to the formation of secondary sulfate phases such as Aphthitalite [(K₃Na(SO₄)₂)]. This behavior leads to an extended setting time, which can be modulated by APA to ensure a controlled processing window. Flowability tests show that BFAK reduces the spread diameter, improving cohesion without causing excessive dispersion. Calibration cylinder tests confirm that the formulation with 1.5% APA and 2% BFAK achieves the maximum printable height (35 cm), reflecting superior buildability and load-bearing capacity. These findings underscore the novelty of combining BFAK and APA as a strategy to overcome current rheological limitations in digital construction. The synergistic effect between both additives provides tailored fresh-state properties and structural reliability, advancing the development of a sustainable SMC and printable cementitious materials. Full article

Driven by stringent emission regulations, advanced combustion modes utilizing turbulent jet ignition technology are pivotal for enhancing the performance of marine low-speed natural gas dual-fuel engines. This review focuses on three novel combustion modes, yielding key conclusions: (1) Compared to the conventional DJCDC mode, the TJCDC mode exhibits a significantly higher swirl ratio and turbulence kinetic energy in the main chamber during initial combustion. This promotes natural gas jet development and combustion acceleration, leading to shorter ignition delay, reduced combustion duration, and a combustion center (CA50) positioned closer to the Top Dead Center (TDC), alongside higher peak cylinder pressure and a faster early heat release rate. Energetically, while TJCDC incurs higher heat transfer losses, it benefits from lower exhaust energy and irreversible exergy loss, indicating greater potential for useful work extraction, albeit with slightly higher indicated specific NOx emissions. (2) In the high-compression ratio TJCPC mode, the Liquid Pressurized Natural Gas (LPNG) injection parameters critically impact performance. Delaying the start of injection (SOI) or extending the injection duration degrades premixing uniformity and increases unburned methane (CH₄) slip, with the duration effects showing a load dependency. Optimizing both the injection timing and duration is, therefore, essential for emission control. (3) Increasing the excess air ratio delays the combustion phasing in TJCPC (longer ignition delay, extended combustion duration, and retarded CA50). However, this shift positions the heat release more optimally relative to the TDC, resulting in significantly improved indicated thermal efficiency. This work provides a theoretical foundation for optimizing high-efficiency, low-emission combustion strategies in marine dual-fuel engines. Full article

To address the issue where the axial negative velocity on the cylinder wall of the traditional bottom-inlet rotor classifier causes fine particles to be mixed into coarse powder, reducing classification efficiency, this study proposes adding guide vanes to the rotor classifier. By improving the stability of the secondary elutriation flow field, we enhance the secondary classification of coarse particles. Airflow simulations based on ANSYS Fluent show that the guide vanes can significantly strengthen the intensity of the secondary elutriation zone, increase the tangential velocity in the classification zone, and reduce the particle concentration in the secondary air volute. The key results are as follows: when the installation angle is 30°, the classification accuracy reaches its peak with K = 0.71, and the cut size D₅₀ = 48.9 μm. This research provides a theoretical basis for optimizing the structural design of classifiers. Full article

Knowledge of propagation methods is crucial for conserving endangered plant species. Cycads are highly threatened, and propagation protocols using seeds and stem cuttings are well-understood. No air layer technique has been developed for cycad propagation, so the objective of this study was to develop a working protocol for adding this technique for cycad conservation. We opened wounds on mature Cycas edentata de Laub. stems to expose cortex and vascular tissue then installed an air layer medium to determine if adventitious roots would form. In one experiment, the peripheral vascular cylinder was exposed from 90° to 360°; in a second experiment, the use of auxin-promoting root stimulants was compared with a control group with no stimulants; and in a third experiment, the interior vascular cylinders were exposed in addition to the peripheral vascular cylinder. Every replication in every experiment developed adventitious roots beginning about 8 weeks and were ready to harvest with 10 cm roots by 14 weeks. The robust roots were about 1 cm in diameter, geotropic, and restricted to the outermost vascular cylinder exposed on the upper surface of the wounds. The number of roots and total root length per propagule increased by more than 300% as the percentage of exposed vascular tissue increased from 90° to 360°. Air layer techniques can be added to the cycad conservation toolbox, and its use may aid in conserving this threatened group of plants. Full article

Substantial boosts in the low-energy nano-oxygenation of incoming process water were achieved at a municipal wastewater treatment plant (WWTP) upstream of activated sludge (AS) aeration lanes on a single-pass basis by means of an electric field nanobubble (NB) generation method (with unit residence times of the order of just 10–15 s). Both ambient air and O₂ cylinders were used as gas sources. In both cases, it was found that the levels of dissolved oxygen (DO) were maintained far higher for much longer than those of conventionally aerated water in the AS lane—and at DO levels in the optimal operational WWTP oxygenation zone of about 2.5–3.5 mg/L. In the AS lanes themselves, there were also excellent conversions to nitrate from nitrite, owing to reactive oxygen species (ROS) and some improvements in BOD and E. coli profiles. Nanobubble-enhanced Dissolved Air Flotation (DAF) was found to be enhanced at shorter times for batch processes: settlement dynamics were slowed slightly initially upon contact with virgin NBs, although the overall time was not particularly affected, owing to faster settlement once the recruitment of micro-particulates took place around the NBs—actually making density-filtering ultimately more facile. The development of machine learning (ML) models predictive of NB populations was carried out in laboratory work with deionised water, in addition to WWTP influent water for a second class of field-oriented ML models based on a more narrow set of more easily and quickly measured data variables in the field, and correlations were found for a more facile prediction of important parameters, such as the NB generation rate and the particular dependent variable that is required to be correlated with the efficient and effective functioning of the nanobubble generator (NBG) for the task at hand—e.g., boosting dissolved oxygen (DO) or shifting Oxidative Reductive Potential (ORP). Full article

The microstructure and surface behavior of iron-based 304 stainless steel after temperature exposure was studied by Mössbauer spectroscopy, powder X-ray diffraction, scanning electron microscopy, energy dispersive analysis and positron annihilation. The tested specimens were in the form of cylinders produced by the casting process. The samples were annealed in air in the 600–1000 °C temperature range for 36 h. Under the influence of temperature, cast 304 stainless steel underwent austenitic–ferritic transformation and tended to form an oxide layer on the surface. The oxides were mainly found in the thin surface layer (0.3 μm) and consisted of Fe oxides and oxides of alloying elements (Cr and Mn) in the form of corundum, while, in the bulk region (10 μm), the phase transformation of austenite to ferrite occurred. Surface phase inhomogeneity was studied by Mössbauer spectroscopy. The method of positron annihilation was used to study defects and the effect of annealing on the formation and removal of a defect structure. Full article

This study investigates the impact of circumferential angle (φ) and interaction angle (θ) between hydrogen jets and diesel sprays in a co-axial hydrogen–diesel injector on combustion and emissions in a hydrogen–diesel dual-fuel engine using 3D CFD simulations. The results demonstrate that a co-axial dual-layer nozzle design significantly enhances combustion performance by leveraging hydrogen jet kinetic energy to accelerate fuel–air mixing. Specifically, a co-axial alignment (φ = 0°) between hydrogen and diesel sprays achieves optimal combustion characteristics, including the highest in-cylinder pressure (20.92 MPa), the earliest ignition timing (−0.3° CA ATDC), and the maximum indicated power of the high-pressure cycle (47.26 kW). However, this configuration also results in elevated emissions, with 29.6% higher NOx and 34.5% higher soot levels compared to a φ = 15° arrangement. To balance efficiency and emissions, an interaction angle of θ = 7.5° proves most effective, further improving combustion efficiency and increasing indicated power to 47.69 kW while reducing residual fuel mass. For applications prioritizing power output, the φ = 0° and θ = 7.5° configuration is recommended, whereas a φ = 15° alignment with a moderate θ (5–7.5°) offers a viable compromise, maintaining over 90% of peak power while substantially lowering NOx and soot emissions. Full article

The activity of the present work is part of a research project aimed at proposing a solution for off-grid charging stations relying on the adoption of a reciprocating engine fuelled with alternative renewable fuels. This technology has as its main advantage the zero-carbon emissions impact of biofuels with small modifications to current ICE technology and refuelling infrastructure. This research is founded on preliminary experimental tests carried out on a six-cylinder spark-ignition engine adapted to pure ethanol fuelling with a single-point injection system. The experimental results obtained at different engine loads have been useful to build and validate a CFD model by testing several kinetic mechanisms and for the proper calibration of a flame speed model. Nevertheless, due to the chemical and physical properties of alcohols such as ethanol, this type of fuelling system leads to a significant non-uniformity of the mixture among the cylinders, and in some cases, to rich air-to-fuel ratio; numerical simulations are performed to address such an issue, and to evaluate performance and exhaust emissions, in terms of CO, CO₂, and NO_x. Finally, a study on spark timing variation is presented as well, to study its effect on performance and pollutants. Full article

Considering that piston internal combustion engines will remain essential converters of chemical energy into mechanical energy for an extended period, providing optimal diagnostic tools for their operation is imperative. Mechanical vibrations generated during machine operation constitute one of the most valuable sources of information about their technical condition. Their primary advantage lies in conveying diagnostic data with minimal time delay. This article presents a novel approach to vibroacoustic diagnostics of the combustion process in internal combustion piston engines. It leverages vibration signals carrying information about the pressure in the engine cylinder during fuel–air mixture combustion. In the proposed method, cylinder pressure information is reconstructed from vibration signals recorded on the cylinder head of the internal combustion engine. This method of signal-to-signal processing uses deep artificial neural network (ANN) models for signal reconstruction, providing an extensive exploration of the abilities of the presented models in the reconstruction of the pressure measurements. Furthermore, a novel two-network model, utilizing a U-net architecture with a dedicated smoothing network (SmN), allows for producing signals with minimal noise and outperforms other commonly used signal-to-signal architectures explored in this paper. To test the proposed methods, the study was limited to a single-cylinder engine, which presents certain constraints. However, this initial approach may serve as an inspiration for researchers to extend its application to multi-cylinder engines. Full article

In-situ chemical oxidation (ISCO) is a common method to remediate chlorinated ethene contaminants in groundwater. Monitoring the effectiveness of ISCO can be hindered because of insufficient observations to assess oxidant delivery. Advantageously, potassium permanganate, one type of oxidant, provides the opportunity to use its strong electrical signal as a surrogate to track oxidant delivery using time-series borehole geophysical methods, like electromagnetic (EM) induction logging. Here we report a passive ISCO (P-ISCO) experiment, using potassium permanganate cylinders emplaced in boreholes, at a chlorinated ethene contamination site, Naval Air Station Pensacola, Florida. The contaminants are found primarily at the base of a shallow sandy aquifer in contact with an underlying silty-clay confining bed. We used results of the time-series borehole logging collected between 2017 and 2022 in 4 monitoring wells to track oxidant delivery. The EM-induction logs from the monitoring wells showed an increase in EM response primarily along the contact, likely from pooling of the oxidant, during P-ISCO treatment in 2021. Interestingly, concurrent natural gamma-ray (NGR) logging showed a decrease in NGR response at 3 of the 4 wells possibly from the formation of manganese precipitates coating sediments. The coupling of time-series logging and well-chemistry data allowed for an improved assessment of passive ISCO treatment effectiveness. Full article

Compressed air energy storage (CAES) systems represent a critical technological solution for addressing power grid load fluctuations by generating electrical power during peak load periods and storing energy during low load periods. As a prominent branch of CAES, isothermal compressed air energy storage (ICAES) systems have attracted significant research attention due to their elimination of requirements for high-temperature storage chambers and high-temperature compressors. Implementing constant-pressure operation in air storage reservoirs not only enhances energy storage density but also improves system safety. However, existing constant-pressure air storage methodologies necessitate supplementary infrastructure, such as high-pressure water reservoirs or elevated hydraulic columns, thereby escalating capital expenditures. This study introduces a novel constant-pressure air storage strategy for ICAES systems utilizing a linear-driven liquid piston mechanism. The proposed approach achieves constant-pressure air storage through the dual-mode operation strategies of buffer tanks (CBA and CBP modes) and hydraulic cylinders (CPP and CPW modes), eliminating the requirement for an auxiliary high-pressure apparatus or extensive civil engineering modifications. A prototype two-stage constant-pressure ICAES architecture was proposed, integrating low-pressure equipment with liquid pistons and providing detailed operational processes for preconditioning, energy storage, and power generation. A comprehensive mathematical model of the system is developed and validated through process simulation and performance characterization of a 100 kWh capacity system. It demonstrates that under operational conditions of 1 MPa of low pressure and 5 MPa of storage pressure, the system achieves an efficiency of 74.0% when the low-pressure equipment and liquid piston exhibit efficiencies of 85% and 90%, respectively. Furthermore, parametric analysis reveals a negative correlation between system efficiency and low-pressure parameters. Full article

This study aims to investigate the impact of combustion chamber geometry and biodiesel on the performance of diesel engines under various load conditions. Simulations were conducted using AVL FIRE software, followed by experimental validation to compare the performance of the prototype Omega combustion chamber with the optimized TCD combustion chamber (T for turbocharger, C for charger air cooling, and D for diesel particle filter). This study utilized four types of fuels: D100, B10, B20, and B50, and was conducted under different load conditions at a rated speed of 1800 revolutions per minute (rpm). The results demonstrate that the TCD combustion chamber outperforms the Omega chamber in terms of indicated thermal efficiency (ITE), in-cylinder pressure, and temperature, and also exhibits a lower indicated specific fuel consumption (ISFC). Additionally, the TCD chamber shows lower soot and carbon monoxide (CO) emissions compared to the Omega chamber, with further reductions as the load increases and the biodiesel blend ratio is raised. The high oxygen content in biodiesel helps to reduce soot and CO formation, while its lower sulfur content and heating value contribute to a decrease in combustion temperature and a reduction in nitrogen oxide (NOx) production. However, the NOx emissions from the TCD chamber are still higher than those from the Omega chamber, possibly due to the increased in-cylinder temperature resulting from its combustion chamber structure. The findings provide valuable insights into diesel engine system design and the application of oxygenated fuels, promoting the development of clean combustion technologies. Full article

This study evaluates the potential of hydrogen as a clean additive to conventional diesel fuel. Experiments were carried out on a single-cylinder, air-cooled diesel engine under half- and full-load conditions, across engine speeds ranging from 1000 to 3000 rpm. Hydrogen, produced on site via a proton exchange membrane electrolyser, was supplied to the engine at a constant flow rate of 0.5 L/min. Compared to pure diesel, the hydrogen–diesel blend reduced specific fuel consumption by 10% and increased brake thermal efficiency by 10% at full load. Emissions of carbon monoxide and carbon dioxide decreased by 13% and 17%, respectively, at half load. Additionally, nitrogen oxide emissions dropped by 17%. These results highlight the potential of hydrogen to improve combustion efficiency while significantly mitigating emissions, offering a viable transitional solution for cleaner power generation using existing diesel infrastructure. Full article

In this study, the photonic band structure, transmissivity, and electric field distribution of a two-dimensional photonic crystal coupled waveguide structure are calculated using the supercell technique and finite element method. The waveguide consists of circular $KNb{O}_3$ and functional dielectric cylinders embedded in air. The dielectric constant of a functional medium cylinder is spatially dependent, which is realized through the electro-optic and Kerr effects. The dielectric constant function is defined as ${\epsilon }_c\left(r\right)=k·r+b$ ($0⩽r⩽r_c$), where the coefficient k and parameter b can be adjusted by an external electric field. By tuning k and b, the transmission characteristics of the waveguide, including the propagation direction and light field distribution, exhibit significant adjustability. Specifically, parameter b enhances or suppresses the transmissivity at output ports 1 and 2. By utilizing the regulatory capability of functional media on waveguide transmission characteristics, optical filters with specific filtering functions can be designed. These findings provide novel design strategies for advanced optical devices. Full article