Increase In Ratio Research Articles

Research on the implementation of free piston engine generator at various compression ratios and combustion performance of multiple fuels

The Free Piston Engine Generator (FPEG) is a novel energy conversion system that directly couples a free piston engine with a linear generator. Its ability to adjust the compression ratio over a wide range without complex auxiliary structures and its adaptability to different fuels have garnered significant attention. To improve the efficiency and cleanliness of FPEG, This study employs an FPEG prototype test bench, using ethanol and n-propanol as raw materials, mixed with aviation kerosene (RP-3) at volume ratios of 20 %, 40 %, and 60 %, respectively. It investigates the impact mechanisms and operating characteristics of different running parameters on the compression ratio of FPEG when using different fuels, and to analyze the combustion and emission characteristics of FPEG under various compression ratio conditions. The results show that compared to gasoline, the alcohol/RP-3 mixtures (with alcohol content >40 %) have higher brake thermal efficiency and significantly reduced CO emissions. As the compression ratio increases, the brake thermal efficiency of alcohol/RP-3 mixtures further improves, while CO and HC emissions decrease. At higher compression ratios, the n-propanol/kerosene blends show higher efficiency and lower CO and HC emissions. These findings provide important insights into the multi-fuel application of FPEG and the potential for cleaner energy conversion.

Analysis of Factors Affecting CO2 Emissions in Türkiye Using Quantile Regression

This study aims to show how the impact of factors on carbon dioxide (CO2) emissions differs at the quantile level and to demonstrate the superiority of the quantile regression method over the OLS method by using quantile regression and ordinary least squares (OLS) methods in order to examine the factors affecting CO2 emissions in Türkiye in depth. Covering the period 1990–2021, this study evaluates the relationship between CO2 emissions and GDP per capita growth, population growth, and renewable energy consumption. One of the important findings of the study is that the increase in the population ratio, which is insignificant according to the OLS method, positively affects CO2 emissions at the 0.25 quantile point. According to both OLS and quantile regression methods, GDP growth does not affect CO2 emissions, while renewable energy consumption has a significant and negative effect according to both models. These results demonstrate that economic growth has no discernible impact on CO2 emissions in Türkiye, while investments in renewable energy can significantly lower emissions and open the door for quantile regression to be used more widely in related research. Unlike traditional methods that focus only on the conditional mean, the quantile regression method provides a comprehensive framework for Türkiye’s sustainable development policies by exploring factor effects at different emission levels.

Microstructural Evolution and Mechanical Properties of Reeled X65 Pipeline Steel during Cyclic Plastic Deformation and Natural Aging

The reel laying is recognized as a cost‐effective installation process for offshore pipelines. However, the mechanical properties are modified due to plastic deformation during the reel laying and lowering process of reeled pipelines and the subsequent natural aging in service. Cyclic plastic deformation (CPD) is conducted on X65 pipeline steel to simulate the strain experienced in the reel‐laying and lowering process, and then, the CPD specimen is aged at 250 °C to simulate natural aging in service. The dislocation configurations gradually evolve from dislocation lines and tangles into dislocation walls and cells due to the increase in strain level. After CPD and aging, the tensile strength increases by about 25 MPa, which is not significantly affected by the last introduced load direction and strain level. At the end of compressive loading, the yield strength and yield ratio decrease, but the uniform elongation increases significantly. In contrast, at the end of tensile loading, the yield strength and yield ratio increase, but the uniform elongation decreases slightly. The yield strength further increases as the strain level increases from 2 to 3%. Therefore, CPD and aging modify the mechanical properties of X65, considerably depending on the last introduced load direction and strain level.

H2 Optimization of a New Type of Tuned Lever Inerter-like Mass Damper (TLIMD) for Attenuating Structure Vibrations

The lever or the lever-type mechanism can achieve an inertia amplification effect by appropriately calibrating its structural configuration, and it is also proven to be one of the most cost-effective solution for the inerter realization compared with other mechanical devices. Benefitting from this property, the present paper adopted a new type of tuned lever inerter-like mass damper (TLIMD) for attenuating stochastic load-induced structure dynamic responses. A set of closed-form formulae for the TLIMD optimal parameters are developed by the use of H2 norm optimization criterion, wherein the structure’s inherent damping is explicitly accounted for. It is theoretically demonstrated that the TLIMD optimal parameters are mainly dominated by three critical parameters, i.e., the damper mass ratio, the lever length ratio (known as the inertia amplification ratio) and also the host structural damping. The proposed formulae for the TLIMD optimization are validated through the seismic analysis, where two classic inerter-based dampers (i.e., the tuned mass damper inerter (TMDI) and the tuned inerter damper (TID)) optimized by the numerical technique are included in the discussion. It is found that the TLIMD has a superior advantage in reducing the structure responses and also exhibits stronger robustness for the detuning condition than the classic inerter-based dampers. Furthermore, the increase in the damper mass ratio and the lever length ratio can be beneficial for enhancing its performance.

Mechanical, thermal and gas separation properties of copolyimides and their thermal rearrangement copolymer membranes with spirobisindane structures

In this work, two kinds of dimaine monomers with spirocyclic structures, including 3,3,3′,3′-tetramethyl-6,6′-bis[3-amino-4-hydroxyphenoxy]-1,1′-spirobisindane (TBAHS) and 3,3,3′,3′-tetramethyl-bis(5-amino-6-hydroxyphenyl)-1,1′-spirobisindane (TBHAS) are firstly synthesized. Then, the two diamines TBAHS and TBHAS are copolymerized in different molar ratios with equimolar 4,4′-(hexafluoroisopropenyl)diphthalic anhydride (6FDA) to synthesize poly(amic acid) (PAA) solution, followed by thermal imidization to obtain a series of copolyimide (coPI) membranes. Next, these coPI(TBAHS-TBHAS) specimens are subjected to thermal rearrangement (TR) treatment at 450°C to obtain the corresponding coTR(TBAHS-TBHAS) copolymer membranes. The influences of the molar ratio of TBAHS to TBHAS, thermal treatment temperature and time on the microstructures and properties of the PI and TR copolymers are investigated. With the increase of rigid TBHAS molar ratio, the glass transition temperature ( Tg) and d-spacing value of the coPI(TBAHS-TBHAS) samples are significantly enhanced. Furthermore, as the thermal treatment temperature increases, the mechanical properties of the copolymer membranes display a sharply decline trend, but the d-spacing values are obviously increased. When the molar ratio of TBAHS to TBHAS is 7:3, the gas permeabilities of the coTR membrane reach 1140.5, 1180.6, 306.6, and 44.9 Barrer for H2, CO2, O2, and N2, respectively. Meanwhile, the ideal selectivity of O2/ N2 is 6.82, suggesting a superior separation performance close to the 2015 upper limit. Furthermore, with the increase of thermal treatment temperature and time, the gas permeabilities are also improved.

A preliminary experimental study on atomization rainfall properties by two-jet collision in high dam discharge

The energy dissipation method commonly employed for flood discharge in high dams involves the collision of jets in the air. This approach frequently results in the issue of flood discharge atomization. This study experimentally investigates the rainfall characteristics resulting from the interaction between a surface-orifice jet and a deep-orifice jet during high dam discharges. The research explores various flow rate ratios and collision angles of the two jets, focusing on the spatial distribution of rainfall intensity, as well as the size and velocity of droplets post-collision. The findings revealed that the rainfall distribution on the horizontal plane resembles a mushroom cloud, with the maximum rainfall intensity at the center. Increasing the collision angle between the jets significantly increases the dispersion range of atomized rainfall, while the maximum intensity decreases. Additionally, as the jet flow rate ratio increases, the dispersal range of rainfall initially expands before stabilizing, with relatively minor variations in intensity. Following a two-jet collision, the trajectory of the jet was derived, and the associated parameters were determined using experimental data. The probability distributions for droplet size and velocity closely approximated Gaussian distributions. The study also observed that the number of droplets per unit time, along with the ensemble-averaged diameter and velocity, initially increases and then decreases longitudinally. Meanwhile, the number of droplets per unit time gradually decreases in the lateral direction, while the ensemble-averaged diameter and velocity remain relatively constant. Furthermore, with an increase in the jet flow rate ratio, both the ensemble-averaged diameter and velocity of droplets follow a pattern of initial increase and subsequent decrease, while the collision angle has no significant impact.

Neighborhood Opportunity is Associated with Completion of Hepatocellular Carcinoma Surveillance Prior to the Diagnosis of Hepatocellular Carcinoma in Patients with Cirrhosis

BackgroundThe Ohio Opportunity Index (OOI) is a multidimensional index used to quantify neighborhood-level resources to access a wide array of factors that influence health. This study examined the relationship between neighborhood opportunity and completion of guideline-concordant hepatocellular carcinoma (HCC) screening in patients with cirrhosis. MethodsThis retrospective study included patients with cirrhosis and HCC who received care at The Ohio State University Wexner Medical Center between 1/1/2015 and 12/31/2021. High opportunity was defined as a score greater than the third quartile of the study cohort. Modified Poisson regression models with robust variance examined the association, on the prevalence ratio (aPR) scale, between guideline-concordant HCC screening and high neighborhood opportunity status. ResultsThis study included 157 cirrhosis patients newly diagnosed with HCC. Only 25.5% of the patients completed HCC surveillance within 6 months prior to diagnosis. The OOI was a significant predictor of adherence in all models. For every ten-percentile increase in OOI score, there was a consistent increase in the prevalence ratio (PR) of pre-diagnosis HCC surveillance (PR=1.37, 95% CI 1.10-1.71). This effect remained significant after controlling for sociodemographic, clinical, and cirrhosis-related variables (adjusted PR=1.38, 95% CI 1.02-1.85. Compared to those with high OOI (i.e.,≥Q3), patients in the lowest opportunity quartile had a 64% lower prevalence of HCC screening (PR=0.36, 95% CI 0.26-0.50). ConclusionNeighborhood opportunity status has a dose-dependent effect on HCC surveillance adherence in patients with cirrhosis. Future studies should identify neighborhood-level interventions to reduce socioeconomic disparities in HCC diagnosis and outcomes.

Gastroesophageal reflux disease, mood swings, and frozen shoulder: A two-sample, two-step Mendelian randomization study.

A Mendelian randomization (MR) study was undertaken to establish a causal link between gastroesophageal reflux disease (GERD) and frozen shoulder (FS), examining whether the risk of GERD with FS is mediated through mood fluctuations. Genetic loci from populations of independent European ancestry were selected as instrumental variables for GERD, FS, and mood swings. The primary analysis employed the inverse-variance weighted method supplemented by 3 additional analytical methods. This was conducted using two-sample and two-step MR analyses. This study explored the correlation and mediating effects of mood swings between GERD and FS. Our study employed heterogeneity and horizontal diversity, and sensitivity analysis was conducted using the leave-one-out method to explore the robustness of the results. In the two-sample MR analysis, for every 1-unit increase in the log-transformed odds ratio (OR) of GERD, the corresponding OR increased to 1.844 (inverse-variance weighting: OR = 1.844, 95% confidence interval: 1.47-2.30, P < .001). In the two-step MR analysis, we found that mood swings played a mediating role in the association between GERD and FS. We assessed this mediating effect using the delta method (b = 0.181, SE = 0.059, OR = 1.199, 95% confidence interval: 1.072-1.349). Analysis of the data using the above methods indicated that GERD is a risk factor for FS, and mood swings mediate between the 2. Therefore, GERD and mood swings should be included in the health management of patients with FS.

The Economic Implications of Population Aging on Current Account Balance

This paper focuses on the demographic determinants of current account balance (CAB) across income groups, continents, and time periods between 1993 and 2021. The benchmark model employs a panel data analysis, particularly a two-way effects estimator (Baltagi, 2021), with CAB as the main dependent variable, while savings rate (SAV) is used as an alternative dependent variable. It was found that the old dependency ratio, fertility rate, life expectancy, population growth, and mortality rate have a statistically significant effect on CAB and SAV, but the effects are heterogeneous across income groups and continents. In Africa, an increase in the old dependency ratio has a negative effect on CAB in accordance with the theories of Modigliani & Sterling (1983), Graham, (1987), and Masson & Tryon (1990). Fertility rate has a negative effect on CAB in Africa while having an ambiguous effect in Asia and Europe. In line with the findings of Mason & Lee (2006), there is a positive relationship between fertility rates and CAB and SAV in lower-middle-income countries and negative relationship in high-income countries. Conversely, population growth affects negatively CAB and SAV in lower middle-income countries and positively in high-income countries.

Development of a Negatively Charged Polyether Sulfone Membrane Enriched with MIL-101(Cr)-Modified Magnetic Activated Pyrolytic Coke for Enhanced Dye Removal, Permeability, and Antifouling Properties

Developing high-performance nanofiltration membranes for effectively treating wastewater contaminated with organic pollutants has become increasingly important. Given the hazardous nature of these contaminants, proper treatment of wastewater is crucial before it is released into natural water bodies. This study synthesized a novel composite membrane by incorporating Fe3O4@APC@MIL-101(Cr) nanocomposites into a polyether sulfone (PES) matrix using a phase inversion technique. The inclusion of 0.5wt.% Fe3O4@APC@MIL-101(Cr) significantly enhanced the membrane's hydrophilicity, porosity, and surface characteristics. The optimized membrane achieved an impressive pure water flux (PWF) of 90.24L/m²h, reflecting a 400% improvement over pristine PES membranes. Moreover, it exhibited excellent rejection rates of 97.21% for crystal violet (CV) and 99.43% for methylene blue (MB), alongside a rejection efficiency of 57.73% for the anionic dye methyl orange (MO). The antifouling performance was notably improved, as evidenced by an increase in the flux recovery ratio (FRR) from 46% for bare PES membranes to 81.11% for hybrid membranes. Additionally, the effects of various salt types on the membrane's separation performance were investigated. The Fe3O4@APC@MIL-101(Cr) modified PES membranes demonstrate significant potential as effective candidates for treating wastewater contaminated with dye pollutants.

Colorimetric and fluorometric sensing of polar E120 in juice and environmental water samples using mannitol-functionalized magnetic nanoparticles and nitrogen-doped carbon dots

In this study, mannitol-functionalized magnetic nanoparticles (MMNPs) as a unique nanosorbent and N-doped fluorescent carbon dots (N-CDs) as a cost-effective nanosensor were created and utilized, for the first time, for dispersive micro-solid-phase extraction (Dµ-SPE) to determine carmine (E120) dye in water samples and juices. The modification of the magnetic nanoparticles with mannitol was designed to enhance the responsive potential for adsorption of the polar E120 dye from complex sample matrices through electrostatic interaction. The as-fabricated N-CDs fluorescent probe exhibited a high fluorescence quantum yield (Φs) of 43.1 %, allowing for accurate fluorometric detection of E120 dye. The as-synthesized MMNPs nanosorbent and fluorescent N-CDs nanoprobe were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Energy Dispersive X-ray (EDX), Thermogravimetric analysis (TGA), and Vibrating-sample magnetometer (VSM). Density Functional Theory (DFT) studied the E120 dye structure using Gaussian 09 to explore the interactions between E 120 dye molecules and MMNPs/N-CDs. The impact of the critical adsorption and detection experimental factors was investigated and adjusted. A minimal amount of MMNPs nanosorbent (150 mg) is sufficient for E120 extraction in an acceptable time of 15 min. Furthermore, with a high determination coefficient, the adsorption characteristics fit with the models of Langmuir isotherm and first-order kinetics. The adsorption capacity (qe) of the as-fabricated MMNPs was 87.7 mg.g−1. After adsorption, E120 dye was fluorometrically analyzed using nitrogen-doped carbon dots as a fluorescent nanosensor via the inner filter effect (IFE) mechanism. Under the optimized conditions, the proposed fluorometric procedures showed a linear increase in the fluorescence ratio with increasing the E120 concentration in the range of 1.0 – 160.0 μg.mL−1 with detection (LOD) and quantitation (LOQ) limits of 0.27 and 0.83 μg.mL−1, respectively. The relative standard deviation (%RSD) did not exceed 2.34 %. The proposed methodology was successfully applied to determine E120 dye in juice and environmental water samples with % recovery ranged from 89.2-106.1 % and 92.9–107.2 %, respectively offering a reliable and environmentally friendly alternative to traditional detection methods with potential applications across various industries.

Flow-induced vibration and heat transfer characteristics of three elliptical cylinders arranged in an isosceles triangle

This study investigates the flow-induced vibration (FIV) and heat transfer behavior of three heated cylinders arranged in an isosceles triangle configuration at a Reynolds number of 100. A dynamic model for the FIV of two-dimensional, elastically supported cylinders was developed using computational fluid dynamics simulations and overset mesh technology. The effects of aspect ratio (AR) and angle of attack (α) were examined by varying α from 30° to 90° and AR from 0.75 to 2.0, with AR = 1.0 corresponding to a circular cross section. To study FIV, the two-degree-of-freedom motion of the cylinders was analyzed across a range of reduced velocities (Ur = 2–12). The results indicate that as α increases, the impact of the upstream cylinder's wake on the downstream cylinders gradually weakens, resulting in lower vibration amplitudes and higher heat transfer rates for the downstream cylinders. Notably, when α reaches 90°, the streamwise amplitude becomes almost negligible. At α = 30° and 45°, the average Nusselt number of the downstream cylinder is generally lower than that of the upstream cylinder. However, when α reaches 60°, the average Nusselt number of the downstream cylinders becomes noticeably higher than that of the upstream cylinder. As the aspect ratio increases, the lock-in region of the cylinders shifts from being concentrated at Ur = 6 and 8 to Ur = 4 and 6, indicating that the increase in aspect ratio raises the vortex shedding frequency.

Wave mode observation of hydrogen/oxygen driven rotating detonations in the hollow and annular rotating detonation rocket engine

The rotating detonation rocket engine (RDRE) fueled by hydrogen/oxygen propellant represents a promising propulsion technology due to its high thermodynamic efficiency and propellant superior specific impulse. The rotating detonation wave (RDW) must propagate in a specific propagation mode while maintaining the self-sustaining state to ensure stable operation. An experimental system of hydrogen/oxygen fueled RDRE was developed in the present study. The operation of RDRE and propagation mode of RDW were investigated under atmospheric pressure conditions, and both hollow and annular combustors were tested. The high-frequency pressure fluctuations in the RDRE were measured by the dynamic pressure transducer, while a high-speed camera was used to capture images of flame luminescence at the rear end of the RDRE. The experimental results showed that the RDW could be initiated and reached a self-sustaining propagation state with hydrogen/oxygen propellant in the hollow and annular RDRE. A single-wave mode, a two-wave co-rotating mode, and a three-wave co-rotating mode were visualized under different conditions. With the increase in the equivalence ratio, the number of rotating detonation fronts decreased, and the variations in the RDW propagation modes were consistent in the hollow and annular RDRE. However, when the equivalence ratio exceeds 1.2, the propagation velocity decreases sharply in the annular combustor, while in the hollow combustor the RDW propagates stably, revealing a higher upper limit for the equivalence ratio. Also, the dominant frequency distribution was more concentrated in the hollow combustor. The findings provide valuable insight into the variations in detonation modes related to the equivalence ratio and combustor configuration.

Large-scale dual-responsive ClO2 controlled-release film for strawberry preservation

Chlorine dioxide (ClO2) exhibits promising potential for the application in food preservation. However, the large-scale production of controlled-release ClO2 films faces challenges. The sodium chlorite microcapsules (Micro-SC) were successfully prepared in this study using polyvinyl alcohol (PVA) as the wall material through the spray drying method. Furthermore, A large-scale preparation of temperature and humidity dual-responsive ClO2 controlled-release films (Micro-SC@EVA) was achieved using melt extrusion. The film could release ClO2 triggered by water vapor for 36 days. The antibacterial effects were significantly enhanced with the increase of microcapsule ratio from 4 % to 8 %. The Micro-SC@EVA film reduced the total viable count and wight loss of strawberries, inhibits ethylene production, and extended the shelf life of by 150 % compared with the control group at 25 °C. The application evaluation results show that the novel approach for the large-scale preparation of ClO2 controlled-release film holds significant implications for food packaging.

Automated Design Process of a Fixed Wing UAV Maximizing Endurance

Unmanned aerial vehicle (UAV) design necessitates significant effort in prototyping, testing, and design iterations. To reduce design time and improve wing performance, an automated design and optimization framework is proposed utilizing open-source software, including OpenVSP: VSPAERO &amp; Parasite Drag Tool, XFOIL, and Python. This study presents a preliminary UAV wing design methodology, emphasizing weight estimation, drag analysis, stall prediction, and endurance optimization. The maximum takeoff weight of the UAV was calculated after estimating the empty weight using a linear regression from data from 20 existing similar UAVs. The wing and engine sizing were determined using the matching plot technique. A solver with low-fidelity models, combining the Vortex Lattice Method (VLM) and analytical expressions, was used to predict the drag coefficient and maximum lift coefficient of the designed wing. An optimization process using a genetic algorithm was applied to maximize endurance while satisfying requirements such as rate of climb, stall, and maximum speeds. The optimized wing was analyzed with computational fluid dynamics (CFD), and its aerodynamic characteristics were compared with those obtained using VLM and the suggested aerodynamic solver. According to the CFD results, the proposed aerodynamic solver estimated the drag coefficient at zero angle of attack with an error of 17.2% compared to 63.1% using the VLM classic method. The error on the maximum lift coefficient estimation was limited to 5.3%. In terms of optimization, the framework showed an increase in the endurance ratio of up to 2% compared to the Artificial Neural Network method coupled with XFLR5. The primary advantage of the suggested framework is the utilization of open-source software, giving a cost-effective and accessible solution for small and medium-sized startups to design and optimize UAVs to achieve mission objectives.

Analysis of the interfacial evolution characteristics of hollow droplet impact on a liquid pool

The impact dynamics of a hollow droplet on a liquid pool have significant implications across various industrial applications. This study employs numerical simulations to explore the dynamic evolution of the interface during the impact of a hollow droplet on a liquid pool. The investigation focuses on the effects of varying the hollow ratio Dr and liquid pool depth h* while maintaining a constant volume of liquid within the droplet shell. The findings reveal that both the hollow ratio Dr and pool depth h* critically influence the formation of ejecta + lamella, and vortex rings after the impact of a hollow droplet on a liquid pool. The confinement effect of the pool bottom can influence the evolution of the splashing, while the internal air in the hollow droplet can absorb a part of the impact energy during the collision. Specifically, at shallow pool depths, the interface primarily evolves into ejecta + lamella structures, whereas at greater pool depths, vortex ring formation is predominant. Furthermore, an increase in the hollow ratio leads to a reduction in the critical pool depth hc* at which the transition between these interfacial modes occurs. These findings indicate that, in practical applications involving the impact of hollow droplets on liquid pools, sufficient attention should be given to the pool depth. This enhances our understanding of the bottom pressure, droplet impact, and vortex formation, which is of significant relevance to related industrial technologies.

Experimental study on chloride ion permeability of carbonated recycled aggregate concrete considering the effects of multiple factors

The chloride ion permeability is an important index of durability of carbonated recycled aggregate concrete (CRAC), but the resistance to chloride ion permeability of CRAC is affected by many factors and has yet been fully explored, which needs further systematic study. Considering the effects of the replacement ratio of carbonated recycled coarse aggregate (CRCA), the carbonation time of CRAC, the bending load level, the carbonation temperature of CRAC, and the replacement ratio of carbonated recycled fine aggregate (CRFA), the resistance to chloride ion permeability of CRAC was investigated by conducting tests in this paper. The results indicated that, compared with the non-carbonated recycled aggregate concrete (NCRAC), the electric flux of CRAC decreased by 9.14% to 37.34%. An increase in the replacement ratio of CRCA could reduce the resistance to chloride ion permeability of CRAC, while an increase in CRAC carbonation time had a significant effect on improving the resistance to chloride ion permeability. When the replacement ratio of CRCA was 100%, as the carbonation time increased from 0 to 14 days, the maximum reduction in electric flux of CRAC was 31.66%. With the same replacement ratio of CRCA, as the bending load level increased, the decrease in electric flux of CRAC showed an increasing trend compared to that of NCRAC. The resistance to chloride ion permeability of CRAC could be improved with an increase in carbonation temperature. Compared with the CRAC with carbonation temperature of 20 °C, the electric flux of the CRAC with carbonation temperature of 40 °C decreased by 11.03%. When the replacement ratio of CRFA was in the range of 0 to 20%, the resistance to chloride ion permeability of CRAC could be improved by incorporating CRFA, but the improvement effect was not significant. Therefore, compared with the NCRAC, the resistance to chloride ion permeability of CRAC is enhanced, and the research results can provide data support for the engineering application of CRAC.

Experimental Study and Sensitivity Analysis of Performance for a Hydrogen Diaphragm Compressor

As the critical infrastructure of hydrogen in transportation, the energy consumption of hydrogen refuelling stations plays a pivotal role in the progress of hydrogen energy within the transportation sector. Volumetric and isentropic efficiencies serve as metrics for evaluating compressor performance. To investigate the extent of factors, including suction pressure, pressure ratio, overflow pressure, and rotational speed, to the efficiencies of the diaphragm compressor, an experimental rig was set up in this study. The volume and energy losses were analysed by studying pressure–volume diagrams. The result shows that elevating suction pressure results in an increased isentropic efficiency. Specifically, raising suction pressure from 0.2 MPa to 0.8 MPa yields a 10.2% increase in isentropic efficiency. The increase in pressure ratio leads to a reduction in volumetric efficiency but an increase in isentropic efficiency. When the pressure ratio increased from 3 to 7, the volumetric efficiency decreased by 6.5% in volumetric efficiency, but the isentropic efficiency increased by 9.8%. Moreover, the escalation in rotational speed corresponds to a decrease in both volumetric and isentropic efficiencies. As the rotational speed increased from 420 r/min to 660 r/min, volumetric efficiency dropped by 9.6%, and isentropic efficiency experienced a 19.2% decrease.

Gap defect and freeze-thaw cycles effects on mechanical characteristics of concrete-filled steel tube stub columns with experimental and theoretical investigation

As concrete-filled steel tube (CFST) structures become more prevalent in engineering, their durability garners significant attention. Mechanical characteristics of concrete-filled steel tube stub columns under the combined influence of gap defect and freeze-thaw cycles is presented with experimental and theoretical investigation in the paper. Twenty-six concrete-filled steel tube stub columns were designed to study the combined effects on failure mechanisms, axial compression-strain response, strength, and ductility. The experimental results indicate that as the number of freeze-thaw cycles and gap ratio increase, the deformation of the specimen increases and the deformation time advances. The specimen's strength and ductility are decreased by the combined effect of these factors. In the most severe cases, the specimen's overall strength and ductility are reduced by 29.4 % and 44.0 %, respectively. Subsequently, a finite element numerical model is established to parametrically analyze the concrete-filled steel tube stub column. Results show that the degree of restraint in the concrete-filled steel tube significantly influences the reduction in strength and ductility of the specimens. The stronger the restraining effect, the less the degradation of strength and ductility caused by the combined impact of the two factors. Therefore, it is crucial to effectively restrain the concrete within the concrete-filled steel tube to ensure structural safety and durability.

Predictions of windage heating and flow characteristics in a high-speed rotating seal of aero-engine

The labyrinth seal plays a crucial role within the secondary air system of an aeroengine, significantly impacting its safety and reliability. This paper presents a comprehensive evaluation of the complex windage heating phenomenon within a high-speed rotating labyrinth seal system. Employing similarity criteria and dimensional analysis, the multifactorial influences on the seal system are thoroughly characterized. A dedicated high-speed rotating labyrinth seal test rig was constructed to conduct an experimental investigation into the windage heating characteristics of a four-tooth, stepped-slanted labyrinth seal. The results demonstrate a peak windage heating of 11.8 K and windage heating coefficient of 1.14 when the inlet temperature rose from ambient to 100 °C, under the rotating Mach number of 0.418 and pressure ratio of 1.1. Conversely, as the seal clearance increased from 0.2 mm to 0.6 mm, with a rotating Mach number of 0.487 and a pressure ratio of 2.0, the windage heating coefficient decreased to 0.57. Furthermore, five dimensionless operating cases were analyzed using similarity principles to elucidate the correlation between system performance and the combined effects of strong rotating flow and windage heating characteristics. The analysis revealed that the windage heating coefficient exhibited a decreasing trend with increasing flow Reynolds number, effective pressure ratio, inlet swirl ratio, and dimensionless clearance, as the effective pressure ratio increase from 1.1 to 5.0, with the rotating Mach number of 0.624 and flowing Reynolds number of 9600, the windage heating coefficient decrease from 1.831 to 0.797, representing a 56 % reduction. Conversely, the windage heating coefficient increased with a rising rotating Mach number, while the flowing Reynolds number demonstrated a minor influence.