Variations In Operating Parameters Research Articles

Super-large diameter slurry shield tunnel encountering boulder formation: Detection, treatment and data analysis

Boulders pose substantial challenges in coastal urban tunnel engineering. This study, for the first time, utilizes extensive closely spaced borehole data from 3486 drilling points obtained during actual tunnelling through boulder strata to evaluate the effectiveness of microtremor detection, analyze variations in operational parameters, and assess the efficiency of blasting treatment. Additionally, leveraging borehole data, a 3D reconstruction of the soil-boulder-bedrock stratum was developed, and the stratum content ratio at the excavation face was derived. A multivariate linear regression model was established to explore the relationship between boulder geology and construction parameters. The results demonstrated that microtremor surveys effectively identified boulder distributions by analyzing horizontal-to-vertical spectral ratio curves and differences in surface wave phase velocity. Field drilling confirmed the high accuracy of microtremor predictions, particularly in areas with dense or thick boulder layers. Post-blasting secondary drilling revealed boulder fragments smaller than 30 cm, meeting the operational requirements for shield cutter and crusher systems. The presence of boulders was found to increase thrust, torque, and overturning moments, as well as cause abnormal cutter wear. Blasting significantly reduced the standard deviation of operational data, demonstrating its effectiveness in stabilizing tunnelling performance. Regression analysis showed a strong correlation between geological conditions and tunnelling parameters, with results indicating that blasting operations effectively mitigate the adverse impacts of boulders on shield tunnelling performance. This study aims to provide valuable insights and references for future engineering projects encountering similar complex geological conditions.

Evaluation of Adsorption Ability of Lewatit® VP OC 1065 and Diaion™ CR20 Ion Exchangers for Heavy Metals with Particular Consideration of Palladium(II) and Copper(II).

The adsorption capacities of ion exchangers with the primary amine (Lewatit® VP OC 1065) and polyamine (Diaion™ CR20) functional groups relative to Pd(II) and Cu(II) ions were tested in a batch system, taking into account the influence of the acid concentration (HCl: 0.1-6 mol/L; HCl-HNO3: 0.9-0.1 mol/L HCl-0.1-0.9 mol/L HNO3), phase contact time (1-240 min), initial concentration (10-1000 mg/L), agitation speed (120-180 rpm), bead size (0.385-1.2 mm), and temperature (293-333 K), as well as in a column system where the variable operating parameters were HCl and HNO3 concentrations. There were used the pseudo-first order, pseudo-second order, and intraparticle diffusion models to describe the kinetic studies and the Langmuir and Freundlich isotherm models to describe the equilibrium data to obtain better knowledge about the adsorption mechanism. The physicochemical properties of the ion exchangers were characterized by the nitrogen adsorption/desorption analyses, CHNS analysis, Fourier transform infrared spectroscopy, the sieve analysis, and points of zero charge measurements. As it was found, Lewatit® VP OC 1065 exhibited a better ability to remove Pd(II) than Diaion™ CR20, and the adsorption ability series for heavy metals was as follows: Pd(II) >> Zn(II) ≈ Ni(II) >> Cu(II). The optimal experimental conditions for Pd(II) sorption were 0.1 mol/L HCl, agitation speed 180 rpm, temperature 293 K, and bead size fraction 0.43 mm ≤ f3 < 0.6 mm for Diaion™ CR20 and 0.315-1.25 mm for Lewatit® VP OC 1065. The maximum adsorption capacities were 289.68 mg/g for Lewatit® VP OC 1065 and 208.20 mg/g for Diaion™ CR20. The greatest adsorption ability of Lewatit® VP OC 1065 for Pd(II) was also demonstrated in the column studies. The working ion exchange in the 0.1 mol/L HCl system was 0.1050 g/mL, much higher compared to Diaion™ CR20 (0.0545 g/mL). The best desorption yields of %D1 = 23.77% for Diaion™ CR20 and 33.57% for Lewatit® VP OC 1065 were obtained using the 2 mol/L NH3·H2O solution.

Investigations into Hydraulic Instability during the Start-Up Process of a Pump-Turbine under Low-Head Conditions

To investigate the hydraulic characteristics during the start-up process of a full-flow pumped storage unit under low-head conditions, numerical simulations were conducted to study the dynamic characteristics during the process, providing a detailed analysis of the dynamic behavior of the internal flow field during the transition period as well as the associated variation in external performance parameters. Study results revealed a vortex-shedding phenomenon during the initial phase of the start-up process. These vortices restrict the flow, initiating a water hammer effect that abruptly elevates the upstream pressure within the runner. As the high-pressure water hammer dissipated, the flow rate rapidly increased, leading to a secondary but relatively weaker water hammer effect, which caused a momentary drop in pressure. This series of events ultimately resulted in significant oscillations in the unit’s head. After the guide vanes stop opening, the vortex structures at the runner inlet and outlet gradually weaken. As the runner torque continues to decline, the unit gradually approaches a no-load condition and enters the S-shaped region. Concurrently, pressure pulsations intensify, and unstable vortex formations reemerge along the leading and trailing edges of the runner blades. The escalated flow velocity at the runner’s exit contributes to the elongation of the vortex band within the draft tube, ultimately configuring a double-layer vortex structure around the central region and the pipe walls. This configuration of vortices precipitates the no-load instability phenomenon experienced by the unit.

Carbon Dioxide Adsorption by Variation in Operating Parameters of Sound Assisted Fluidization Using Coal Based Fine Activated Carbon

This research delves into the promising domain of CO2 capture through fine solid activated carbon adsorbent, offering a more energy-efficient alternative to traditional adsorption methods. The central challenge addressed here is the utility of cheaper CO2 adsorbent, fine powder materials whose properties can be precisely tailored via molecular-level fictionalization. Equally vital is selecting an optimal fluidizing column configuration that maximizes CO2 interaction with adsorption particles and enhances adsorption efficiency. The proposed solution is a fluidized bed column uniquely equipped with integrated acoustic vibrations to counteract interparticle forces common in fine powders. For adsorption evaluations, sound-assisted fluidized-bed experimentation on a laboratory size was set up. Adsorbent material activated carbon made up of coal underwent rigorous testing between a range of 20 Hz-200 Hz and 20 dB-135 dB. Results reveal the beneficial effects of acoustic enhancement of fluidization quality and adsorption efficiency, increased adsorption capacity, enhanced bed utilization, and accelerated adsorption rates. Extensive research has been conducted on the detailed effects of major operational variables on adsorption performance, notably frequency, sound intensity, and minimum fluidization velocity. The findings highlight the pivotal role of particle size with mean size 75 microns range as a determinant of adsorption capacity at 100 Hz and 125 dB. At the end of experimentation, the adsorbent considered for the experiment is compared to the study adsorption capacity at operating conditions. The research concludes with a discussion on the effects of influencing parameters for adsorption on employing sound vibrations using fluidization technique adsorption for CO2 capture.

Process stability in anaerobic Digestion: Unveiling microbial signatures of full-scale reactor performance

Anaerobic digestion is responding to the growing demand for sustainability by exploring alternatives for methane production through renewable processes. The target is to implement stable production systems at industrial scale that can accommodate heterogeneous feedstocks with seasonal or intermittent availability. In this study, we investigated the microbiomes of six full-scale biogas plant digesters, operated under continuous production with distinct feedstock and varying operating parameters, by monitoring multiple time points over an 18-month period. This time-course experiment analyzed 114 Metagenome-Assembled Genomes alongside physico-chemical assessments to identify common and plant-specific indicators for operational management. Results identify a Limnochordia and a Dysgonomonadaceae bacteria, as well as Candidatus Methanoculleus thermohydrogenotrophicum, as widespread and potentially desirable components of the microbiota for resilient digestion of varying waste, including the peculiar olive pomace. The abundance of individual taxonomic groups and their reconstructed metabolic pathways aligned with the availability of their fermentation substrates, finding a prevalence of beta-oxidizing bacteria with lipid-rich olive pomace. Monitoring through perturbation events revealed possible causative and remediative microbiological factors, in particular Methanosarcina flavescens and Candidatus Syntrophosphaera thermopropionivorans could contribute to restoration of reactor performance. This work showcases relationships between digester operation and its microbiome, supporting microbial monitoring as a tool to increase biogas production efficiency.

Energy performance tradeoff assessment for varying design parameters in office buildings

ABSTRACT Energy performance and heat release from buildings can differ with variations in envelope and operational parameters. This study presents an evidence-based assessment for different study locations in Japan including Sapporo, Tokyo, and Osaka. The analysis used a comparative approach using a reference energy performance simulation model for large office buildings using EnergyPlus to assess the impact of design variations on building performance. The analysis included 66 simulations with 10 design parameters and 2 construction types. The study coupled energy performance with heat release from the building towards outdoor environments since heat release can influence the local thermal environments. Desirable tradeoffs were observed for timber constructions by increasing the cooling setpoint by 1°C reduced cooling and heating energy use by 10.7% and 11.9% in Sapporo, 8.5% and 22.7% in Tokyo, and 6.8% and 24.4% in Osaka. Similarly, cooling and heating peak loads were reduced by 5.9% and 2.4% in Sapporo, 5.4% and 2.0% in Tokyo, and 6.5% and 5.2% in Osaka. Additionally, nighttime heat release also decreased by 12.4% and 13.6% in Sapporo and Tokyo, and 6.2% and 5.7% in Osaka for concrete and timber constructions. The study provides early-stage design support for energy-efficient buildings and improved local thermal environments.

Integrated design and optimization of a conceptual double drum dryer for drying of wheat flour slurry: Experimental validation and computational analysis

AbstractThis study presents a novel conceptual laboratory‐scale double drum dryer (LDD) optimized for the efficient drying of wheat flour slurry into flakes. The research stems from the need to address the complexities of previous methodologies, lack of studies on industrial‐sized dryers, and high cost. The methodology involved designing dryer components, transmission system, creating engineering drawings, and simulating LDD with varied operating parameters. Verification was done using industrial double drum dryer (IGD) data and MATLAB simulations. Parameters were explored including temperature (120–140°C), drum dimension (0.1–0.7 m), and film thickness (0.3–0.6 mm). The design closely matched real‐world performance metrics with mean relative deviations of 2.67%, 3.30%, 10.12% for drum speed, water content, and throughput respectively. The predictive model outperformed the IGD, achieving a 9.13% increase in throughput. Optimal LDD parameters were identified 0.7 m length, 0.2 m diameter, 0.3 mm film thickness, 40% slurry TSS, 120°C temperature, and 4.47 rpm rotational speed, resulting in 3.00% water content and 132.78 kgh−1 throughput offering valuable insights for similar applications in the food industries.Practical applicationsThe research on the novel laboratory‐scale double drum dryer for drying wheat flour‐based slurry holds significant practical implications in the food industry. Firstly, the optimized design and simulation‐based approach offer a cost‐effective and efficient solution for small‐scale food processing businesses aiming to produce wheat flour flakes. By identifying optimal drying parameters, including temperature, drum dimensions, and film thickness, the research enables precise control over the drying process, leading to enhanced product quality and throughput. Moreover, the close agreement between simulation results and industrial observations validates the effectiveness of the proposed methodology, instilling confidence in its practical applicability. The development of a prototype based on these findings facilitates the adoption of this technology by small‐scale enterprises, empowering them to improve their production processes and competitiveness. Overall, this research contributes to advancing drying technology in the food industry, offering tangible benefits in terms of product quality, efficiency, and operational cost reduction.

Enhancing simultaneous nitrification and denitrification in a plant-scale integrated fixed-film activated sludge system: Focusing on the cooperation between activated sludge and biofilm

To further remove nutrients through simultaneous nitrification and denitrification (SND), the integrated fixed-film activated sludge (IFAS) system has become one of the most efficient pathways for modifying the existing wastewater treatment plants. This study investigated the cooperation between suspended activated sludge and carrier-attached biofilm for promoting SND in different seasons in a plant-scale IFAS system. The results showed that the involvement of biofilm could stimulate SND, removing 23.9 % of influent total nitrogen (TN) in the aerobic IFAS system. The nitrification rate and the SND ratio were much influenced by the temperature, resulting in higher TN removal efficiency in summer (90.3 %) than that in winter (86.4 %). The highest SND ratio of 67 % could be achieved at the temperature of 23 °C. Additionally, the SND ratio also depended on a variety of operational parameters (such as dissolved oxygen (DO), COD/NH4+-N, and mixed liquor suspended solids (MLSS)). High-throughput sequencing technology further confirmed that the composition of the functional bacterial communities in activated sludge significantly differed from that in biofilm. Nitrifying bacteria were mostly detected in biofilm samples, while more denitrifying bacteria existed in activated sludge, thus resulting in the enhancement of synergic nitrogen removal via SND in the IFAS system.

A view on the performance comparison between adiabatic and internally-cooled dehumidification processes using liquid desiccant

Humidity control is emphasized in various fields. However, the effectiveness comparison between adiabatic dehumidifier (AD) and internally-cooled dehumidifier (ICD) was only conducted in limited cases, without comprehensive understanding of different cooling mediums and working conditions. In this study, the component effectiveness of these two dehumidifiers is parametrically compared. When chilled water serves as cooling medium, AD has sensible effectiveness of 0.65 and latent effectiveness of 0.84 under baseline case, while those of ICD are 0.52 and 0.85 respectively. AD performs better under higher sensible loads, and ICD is more capable of dealing with more moisture transfer. Low water temperature, low air-desiccant ratio and adequately low water-desiccant ratio also highlight the superiority of AD. When secondary air serves as cooling medium, AD always has higher effectiveness than ICD in the studied range, and the superiority is more significant at lower temperature and humidity of secondary air. Sensible effectiveness of 0.44 and latent effectiveness of 0.78 for AD are obtained under baseline case, while those of ICD are 0.07 and 0.74 respectively. ICD has better adaptivity than AD at a circumstance with great variation of operation parameters. The results contribute to enlightening insights for further design of moisture capture components.

Diesel/biodiesel/biogas mixtures driven compression ignition internal combustion engines constructal design

This paper introduces a first and second law based transient mathematical model for 4-stroke compression ignition internal combustion engines (CI-ICE) driven by diesel/biodiesel/biogas mixtures to allow for the maximization of system performance. In this way, the CI-ICE morphology that provides easier access to the currents that flow through it is sought, according to constructal law. The total entropy generated in the CI-ICE cycle was calculated by adding the entropy generation in all strokes. An optimization problem was formulated based on the variation of operating and geometric parameters, and the objective functions were the effective and 2nd law efficiencies, ηef and ηII, as well as the destroyed exergy fraction, yD. The optimal ranges found for the bore-stroke, compression and conrod-crank ratios were 0.51≤Bopt≤1.25; 2.07≤ROD/CSopt≤4.14, and 10.23≤CRopt≤33.44 in which ηefηIImax≃0.330.37 with yD,min≃0.66 for D100 (pure diesel), and ηefηIImax≃0.310.35 with yD,min≃0.64 for B50D25NG25 (biodiesel/diesel/natural gas blend). The maxima and minimum found were sharp, since ηef and ηII varied up to 71% and 69% in comparison to their maximum values, respectively, and yD up to 45% in comparison to its minimum value within the adopted ranges of variation of the optimized parameters. Such large variations stress the importance of considering the optimized CI-ICE morphology in actual design, i.e., CI-ICE constructal design.

A microwave-regenerable multi-walled carbon nanotube/polyaniline/Fe3O4 ternary nanocomposite for quantifiable sorption of cationic and anionic dyes

The coexistence of toxic dyestuffs in the aquatic environment requires the urgent development of a multifunctional sorbent for their efficient sequestration from aqueous solutions. To achieve this objective, a ternary nanocomposite consisting of an amphoteric, multi-walled, carbon nanotube/polyaniline/magnetite (MWCNTs/PANI/Fe3O4) was successfully synthesized through the co-precipitation of magnetite (Fe3O4) onto the surface of a pre-existing binary composite of MWCNTs/PANI. The structural and morphological features of MWCNTs/PANI/Fe3O4 were scanned using a variety of analysis methods: Fourier transform infrared spectroscopy; both scanning and transmission electron microscopies; energy-dispersive X-ray analysis; thermogravimetric analysis. The capacity of MWCNTs/PANI/Fe3O4 to adsorb cationic dye (Methylene blue, MB), and anionic dye (Congo red, CR) were discerned inclusively under variable operational parameters. The sorption processes of both MB and CR dyes onto MWCNTs/PANI/Fe3O4 were pH-dependent. The sorption process of both dyes onto MWCNTs/PANI/Fe3O4 was reported to fit with the Langmuir model, while the sorption kinetics fitted with the pseudo-second-order kinetic model. The prepared MWCNTs/PANI/Fe3O4 exhibited satisfactory sorption capacities of 142.85 mg g−1 (initial solution pH (pH0): 2.94) and 166.66 mg g−1 (pH0 = 10.03) of the CR and MB dyes, respectively. Dye adsorption followed the monolayer chemisorption phenomenon. The sorption process was exothermic. The application of microwave irradiation caused effective regeneration, and this finding confirmed the renewability of the composite for at least 4 successive sorption/desorption cycles. Using MWCNTs/PANI/Fe3O4 ternary nanocomposite in dye removal looks promising, as its high adsorption capacity, magnetic properties, and renewability offer an efficient, sustainable, and easily recoverable solution for removing dyes from wastewater.

Evaluation of a concentrated solar power-driven system designed for combined production of cooling and hydrogen

The current technique of hydrogen generation and cooling production raises climatic problems, which calls for the investigation of cleaner alternatives. No research has been conducted to propose and analyze a solar thermal power cycle-based water electrolysis for on-site production of hydrogen and the detailed exergy analysis of a series flow double-effect absorption chilling machine employed for large solar cooling. In this regard, a helically coiled tube embedded central receiver is used in the heliostat field for the simultaneous production of solar cooling and green hydrogen to meet the increasing needs of energy and fuel sustainably. The combined system is composed of four sub-systems including a heliostat field, LiBr–H2O operated series-flow double effect absorption refrigeration cycle (DEARC), organic Rankine cycle (ORC), and proton exchange membrane (PEM) electrolyzer. The system was examined from energy and exergy perspectives in the Engineering Equation Solver (EES) using library data of REFPROP for obtaining the thermodynamic properties of working fluids. The results of the thermodynamic model for the combined system are validated. Furthermore, the effect of ambient temperature, solar irradiation, and type of ORC working fluid on the hydrogen and cooling production, and the overall energy and exergy efficiency of the combined system are examined. A computational fluid dynamics simulation applying ANSYS-FLUENT was used to examine how coil curvature ratio and coil torsion affect solar heat transfer fluid (SHTF) pressure and temperature leaving the receiver. The coil curvature ratio affects temperature increase more than coil torsion. Solar heat transfer fluid outlet temperature increases by 36.9 % when the coil curvature ratio increases from 0.063 to 0.095 at direct normal irradiations (DNI) 1200 W/m2, input temperature of 92°C, and coil torsion of 0.032. The response of the cogeneration cycle to varying operating parameters is examined. Application of R141b as the ORC fluid results in a large increase of cooling exergy efficiency from 14.98 % to 63.48 % when the ambient temperature is increased from 15 °C to 45 °C whereas the exergy efficiency of the combined system is marginally improved. The exergy distribution presents for ORC operating on R141b, out of 100 % input solar exergy, 16.42 % is generated as hydrogen exergy and 13.67 % cooling exergy, 66.79 % is the exergy destroyed, and the rest 3.12 % is exergy loss. Exergy analysis is utilized to identify the sources of losses in useful energy within the components of the system considered and provides a more realistic and meaningful assessment than the traditional energy analysis. The results justify a need for the promotion of exergy analysis through policy decisions in the context of the global energy and environment crisis.

Study on performance and structure optimization of self-priming pump based on response surface method

ABSTRACT This paper aims to improve the performance of a self-priming pump by optimizing blade geometry parameters, with the head and efficiency as the targeted objectives. Based on the Response Surface Methodology (RSM), the Computational Fluid Dynamics (CFD) were conducted to investigate the pressure distribution characteristics inside the pump chamber and the variations in pump performance parameters. By analyzing the internal pressure field of the pump, it is concluded that adjusting the blade curvature radius and the outlet angle can change the area and uniformity of the low-pressure zones within the fluid to improve the pump performance. The results show that the fitted regression equations indicate that the blade curvature radius and the blade outlet angle have a significant impact on pump performance, while the blade inlet angle has a relatively minor effect. When the outlet angle β 2 = 60 ∘ , the change of the inlet angle β 1 and the curvature radius R has basically no impact on the efficiency. The self-priming pump achieves its optimum performance when β 1 = 50.8 ∘ , β 2 = 52 ∘ and R = 84.9 mm. Compared to the original model, the optimized model’s head increases by 7.12%, H = 34.12 m; and the efficiency improves by 3.40%, η = 63.8.

A hybrid MCDM optimization for utilization of novel set of biosynthesized nanofluids on thermal performance for solar thermal collectors

Recent advancements in solar technology have spurred researchers to develop a precise and cost-effective method for monitoring solar radiation across diverse environmental conditions. This study focuses on optimizing performance parameters by replacing conventional nanofluids, produced through chemical and physical processes, with biosynthesized counterparts. Biosynthesized nanoparticles, derived from biological sources like microorganisms or plants, offer a promising avenue for enhancing solar panel efficiency. Through the construction and testing of an integrated photovoltaic thermal system, varying operating parameters have been explored to maximize photovoltaic efficiency. The highest overall efficiency, reaching approximately 62 %, was achieved with biosynthesized Graphene oxide nanofluid under higher Direct Normal Irradiance (DNI) levels, while the lowest was observed with Aluminum oxide nanofluid at lower DNI values. Employing Multi-Criteria Decision methods such as Analytical Hierarchical Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), nanofluids were ranked based on criteria including Exergy loss, Surface temperature, Overall efficiency, and Electrical efficiency, with weights of 49.58 %, 28.43 %, 13.45 %, and 8.54 % respectively. TOPSIS prioritized Graphene Oxide as the most favorable nanofluid, followed by Copper-Oxide and Cerium-Oxide, while Aluminum-Oxide received the lowest priority in optimizing PV panel performance.

Research on the factors affecting the product filtration efficiency in mineral processing plants

Filtration is a long-standing process but the technology has changed slowly, mainly based on the increase in filtration pressure and changes in the characteristics of filter media. The problem is high moisture remains product, requiring more expensive technologies (thermal drying) and long processing times. In the mineral processing industry, not only concentrates but also tailings need to be dewatered. The test samples were Cam Duong apatite concentrated and tailing ore, Ta Phoi copper concentrated and Sin Quyen tailing ore, Cua Ong fine coal, and Dak Nong red mud. All samples’ properties have been defined by sieving analyses, SEM method, and gravitational density measurement. Then, samples were experimented with using the Nutsche high-pressure filtration in the variable operational parameters. While the sludge concentration affected the specific resistance, the filter cake height and filtration pressure did not affect as much. At the suitable condition (homogeneous filter cake, 1 bar pressure difference, and 50 grams solid weight), the specific resistance and residual moisture content of the filter cake are around 2.5x10-12÷1.5x10-13 m-2, 15÷25%, respectively. Through the test results, some recommendations are mentioned in order to perfect the process and scale up for industrial production.

Friction Behavior of Fingers on Micro-Textured Flexible Surfaces

Abstract Compared to rigid materials, people have a distinct tactile perception when touching flexible materials. Moreover, adding micro-patterns to the surface enhances the tactile experience even further. This sensation arises from the physical stimulation of frictional behavior between the skin and flexible materials. Therefore, this study focuses on human fingers as the research subjects and employs flexible materials with micro-textured surfaces as frictional objects. A friction test setup is designed to conduct a series of finger friction experiments, and theoretical explanations are provided to elucidate the reasons for performance variations. Research findings show that as the normal load increases, the frictional force gradually increases while the friction coefficient decreases. The former is attributed to the expanding contact area, while the latter is due to the inconsistent rate of frictional force increment with the normal load. The impact of friction velocity is mainly caused by changes in the viscous forces generated at the liquid film in the contact interface and the energy loss in elastic hysteresis. On the other hand, the effect of surface micro-topography is primarily a result of the transition between partial contact and full contact modes under the influence of normal load, leading to alterations in the contact area. Overall, during the finger friction process on a flexible micro-textured surface, changes in contact area play a vital role in modifying frictional performance, with adhesive friction exerting a more significant influence than deformation friction. This study summarizes the variations in frictional performance parameters based on experiments and analyzes the effects of contact area changes and deformation friction mechanisms from a theoretical perspective, providing a theoretical foundation for exploring the genesis of delicate tactile sensations during friction.

Operando analysis of in-plane heterogeneity for the PEM electrolyzer cell: Mappings of temperature and current density

The internal multi-physical fields of a proton exchange membrane electrolyzer cell (PEMEC) are affected by various factors, exhibiting an intricate coupling state. During electrolysis process, the complexity manifests as heterogeneous distribution of in-plane temperature and current density, potentially leading to local hot spots and performance degradation. Such challenges pose threats to the lifespan and operational safety of PEMEC. This study developed temperature measurement endplates and segmented printed circuit board (PCB), enabling operando measurement of in-plane temperature and current density distribution inside a 25 cm2 lab-scale PEMEC. The mappings of temperature and current density were plotted, and the in-plane heterogeneity was assessed by the introduced indexes. The results indicate that variations in operational parameters affect the balance among cell heat production, heat dissipation, and heat input in the flow area, leading to temperature distribution heterogeneity. The migration mechanism of high-temperature zone is elucidated. Factors such as water-gas flow and local conduction contribute to the heterogeneity in current density distribution. Additionally, specific operating conditions including cold and warm start-up, and water starvation are taken as cases, and a detailed analysis is conducted on the dynamic behaviors of current and temperature distribution and the heterogeneity evolution. This work not only provides experimental evidence for the electrical-thermal characteristics inside the PEMEC but also offers insights for local performance evaluation and operation fault diagnosis in practical applications.

Influence of operating parameters on metal flow and thermal characteristics in an EMBr-single-ruler controlled CSP funnel-shaped mould

Electro-magnetic brake (EMBr), as a necessary technique to adjust the metal flow within the mould, has been extensively applied in the continuous casting (CC) production. The EMBr technique, if appropriately applied, can take the benefit of braking effect to weaken jet impingement effect, suppress fluid disturbance and stabilize surface fluctuation. As a result, to obtain a reasonable flow pattern within the CC mould, the braking performance of EMBr technique needs to be flexibly adjusted according to the variation of operational parameters. In this article, to obtain a braking performance of a commonly used EMBr-single-ruler technique within an optimal range, the effect of operating parameters on the metal liquid flow and thermal characteristics in a compact strip production (CSP) thin slab mould is described through a 3-D mathematical modeling of multi-physical field coupling. The results illustrate that the braking performance of the EMBr-single-ruler device is weakened with the increase of the casting speed or the mould width. For the effect of the casting speed and mould width on the metal flow with the application of an EMBr device, an optimum braking performance of the EMBr-single-ruler device can be obtained under the matching parameters of a magnetic induction intensity of 0.30 T and a casting speed of 4.5 m ∙ min‒1 together with a mould width of 1500 mm. Relative to the absence of the EMBr-single-ruler device, the maximum surface fluctuation height is controlled at 6.2 mm, and the mean surface temperature is raised to 1803.6 K. Based on these findings, we conclude that the proper utilization of the EMBr-single-ruler device can avoid the entrainment of flux powder and improve the melting performance of flux powder.

A novel aeroengine real-time model for active stability control: Compressor instabilities integration

Developing a high-confidence entire aeroengine model that accurately incorporating unstable modes is imperative for advancing active stability control. This paper proposes a real-time model for the active stability control of aeroengines, which integrates the compressor's instability into the classical component level model (CLM). Firstly, the principles of CLM and modeling methods for inlet distortion, compressor instability dynamics, and air injector are introduced. Then, the collaborative relationship between the compressor and the other engine's components are studied to construct a real-time model with coupled instability mechanisms, involving the extension of compressor characteristics and the parameters matching between various instability models and the CLM. Finally, simulation cases under multiple unstable modes are set up to verify the effectiveness of the model, and standard instability detection algorithms are employed to confirm the confidence of the unstable signals generated by the model. The results show that the proposed model effectively captures the dynamic characteristics of stall and surge, as well as the steady-state and dynamic simulation capabilities during full operating range. Besides, it can also simulate the impact of the inlet distortion and the air injection on compressor stability. The pulsating characteristics of pressure signals and the variations of performance parameters of the model during stall and surge are highly consistent with the real test data. Moreover, the model achieves a single-step run time of no more than 7.16 ms on the embedded platform, fulfilling real-time requirements. Consequently, the model can serve as a foundation for verifying three critical aspects of active stability control: instability detection, practical actuator, and feedback control algorithms.

Optimizing Distillery Effluent Treatment through Sono-Electrocoagulation: A Response Surface Methodology Approach

This work is an effort to remediate rice grain-based biodigester effluent (BDE) by applying the sono-electrocoagulation (SEC) process using Iron as a sacrificial electrode to accomplish this process. A batch reactor is used for the investigation. The effect of the SEC process on the reduction of chemical oxygen demand (COD) and color from the wastewater was studied by varying operating parameters including ultrasonic power (U), current density (j), initial pH (pHi), and electrolysis time (t) in the ranges of 20-60 W, 49.5-247.5 A/m2, 2-10 and 12-60 minutes respectively. The results obtained were optimized by using central composite design (CCD) which is a special feature of the response surface method (RSM). This tool is well applicable in the SEC process to explores the relationships between different varying operating parameters with two responses namely COD and color removal efficiency. The RSM is to use a sequence of designed experiments to obtain an optimal response. The analysis demonstrated that the quadratic regression model fitted well with SEC-generated data. Moreover, no significant difference was found between experimental and predicted data. The coefficient of determination (R2) of 0.9995 and 0.9895 were observed for COD and color removal efficiency. Results indicated that the COD removal efficiency of 93% and color removal efficiency of 88% were found at optimum conditions U of 50, J of 198 A/m2, pHi of 7, and t of 48 minutes.