Search Results (84)

With the advancement of industrial IoT and artificial intelligence technologies, bearing maintenance is gradually evolving toward predictive maintenance. For large bearings, the internal grease must be replaced promptly once it has deteriorated. As the core lubrication component of such bearings, the suction and discharge device directly determines the efficiency of grease discharge and the operational stability of the bearing. To address the issue of insufficient intake capacity in existing units, this study employs the Herschel–Bulkley non-Newtonian fluid model to analyze intake characteristics and conduct multi-parameter co-optimization, revealing the underlying mechanisms by which vacuum level, grease temperature, and the chamfer structure of the grease inlet pipe influence suction performance. Based on the yield stress and shear thinning characteristics of the grease, the flow equation for the inlet section was derived, and the analytical and CFD results showed consistent trends. With the volumetric flow rate in the inlet section as the optimization objective, a multi-parameter co-optimization of the vacuum level, temperature, and chamfer radius was conducted through orthogonal experiments. The results show that under the optimal parameter combination, the inlet volumetric flow rate was significantly increased, and grease supply stability was markedly improved. The research findings provide a theoretical basis and engineering reference for the design optimization of the suction and discharge device for wind turbine bearings. Full article

Part II of this study builds upon the mathematical framework developed and validated in Part I for describing the geometry and volumetric performance indicators of an innovative three-rotor hydraulic pump with bilateral lantern meshing. This part focuses on the numerical investigation and multi-objective optimization of these indicators through the proper selection of geometric parameters. The aim of the study is to establish the isolated and combined influence of the dimensionless geometric parameters—number of teeth $z$, relative lantern radius $r_c^{\ast }$, and cycloid shortening coefficient $\mathsf{\lambda }$—on the actual flow rate $Q$ and the volumetric efficiency ${\mathsf{\eta }}_v$ under various operating conditions, while maintaining the overall dimensions of the pump element in the radial and axial directions. Through detailed numerical analysis and subsequent rigorous analytical proof, it has been established that the optimal values of the geometric coefficients $r_{c,opt}^{\ast }$ and ${\mathsf{\lambda }}_{opt}$ are strictly determined and provide a simultaneous global maximization of both indicators ($Q,{\eta }_v$), regardless of the operating pressure $p$, rotational speed $n$, or the viscosity of the working fluid. However, an analytically irresolvable conflict regarding the number of teeth $z$ has been identified: a small number maximizes the flow rate, whereas a large number increases the volumetric efficiency. To overcome this contradiction, the problem is formulated within the class of mixed-integer nonlinear programming (MINLP), and multicriteria Pareto optimization is applied, combined with the PSIMS method for the selection of optimal compromise solutions. An empirical relationship (with a coefficient of determination of $R^2=0.9603$) has been derived, which defines the optimal number of teeth $z_{opt}$ as a function of the operating pressure and rotational speed. The proposed methodology provides a reliable and applicable tool for designing highly efficient three-rotor pumps tailored to specific operational requirements. Full article

This study experimentally investigates the mixed convection heat transfer performance of CuZnFe₂O₄–water-based magnetic nanofluids in a cylindrical minichannel under the influence of external magnetic fields. Nanofluids with three different volumetric concentrations (0.25%, 0.50%, and 0.75%) were synthesized and characterized in terms of thermophysical properties. The experiments were conducted within the Richardson number range of 0.1–10 to ensure mixed convection conditions, while magnetic field intensities of 220 G, 300 G, and 380 G were applied using custom-built electromagnets. Results show that suspending CuZnFe₂O₄ nanoparticles significantly enhances the heat transfer rate compared to pure water, mainly due to increased thermal conductivity and particle–fluid interactions. The application of a magnetic field further augments the Nusselt number by disturbing the thermal boundary layer and intensifying particle motion, leading to up to 64.4% improvement compared with pure water at similar Reynolds numbers. In addition, Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) were employed to determine the most influential parameters on heat transfer performance and to develop a predictive correlation for the Nusselt number as a function of Reynolds number, nanoparticle concentration, and magnetic field intensity. The findings highlight the combined effects of nanoparticle suspension and magnetic field application as a promising approach for enhancing heat transfer in low-flow mixed convection regimes, offering valuable insights for thermal management in miniaturized cooling systems. Full article

The present Part I of the comprehensive study is dedicated to establishing the fundamental mathematical and experimental apparatus required for the multi-criteria optimization of the geometric parameters of an innovative three-rotor hydraulic pump with bilateral lantern meshing, subjected to the actual volumetric flow rate $Q$ and the volumetric efficiency ${\eta }_v$. A complex approach integrating similarity theory, dimensional analysis, and mathematical modeling is employed to define and refine the two objective functions subject to optimization. Based on the area of geometric existence of the gearing and additionally imposed geometric and operational constraints, the exact domain for seeking the optima of $Q$ and ${\eta }_v$ is defined. Based on the statistical processing of experimental data, empirical dependencies of the objective functions are derived, accounting for the influence of the pump’s geometric parameters, the operational conditions and the physical properties of the fluid. The criterion equation of the volumetric efficiency, approximated using all experimental data, was obtained with a very high coefficient of determination $R^2=0.9898$. The rest of the study, related to parameter optimization, is contained in Part II. In it, through numerical investigation and analytical proof, the universal optimal parametric values of the dimensionless geometric coefficients (the relative lantern radius $r_{c,opt}^{*}$ and the shortening coefficient ${\lambda }_{opt}$) are identified to achieve maximum flow rate and volumetric efficiency. Furthermore, in Part II, a multi-criteria Pareto optimization (MINLP) is conducted to resolve the engineering conflict regarding the number of teeth $z$, and a direct simple algebraic dependency $z=f\left(p,n\right)$. The generalized results from both parts provide a methodological toolkit and recommendations for the optimal selection of the geometric parameters in the design of pumps of this type with respect to the actual flow rate and volumetric efficiency, in accordance with the operating conditions and regimes. Full article

Currently, hydrogen has become an indispensable topic when discussing the energy transition. Determining the amount of hydrogen produced or lost through leaks is a critical issue. Recently, with the emergence of the low-cost MQ-8 resistive semiconductor sensor, which is sensitive to hydrogen and responds with an output voltage $V_{out}$, there has been considerable interest in its use in small laboratory experiments. The combination of the volumetric method, the MQ-8 sensor, and the BME280 sensor (for temperature, pressure, and humidity) is of significant interest and has industrial applications. This work presents an in-depth study of the combination of the traditional volumetric method with the MQ-8 and BME sensors. Sensor validation metrics were evaluated to ensure the reliability of the results. The pressure remained approximately constant due to the system configuration. The results indicate that for a current of 1 A, it is possible to determine the approximate volume of hydrogen as a function of the sensor’s output voltage. For low currents ranging from 0.76 to 250 mA, the results indicate that it is possible to determine the approximate hydrogen flow rate as a function of the voltage detected by the sensor. With further investigation, it will be possible to propose the use of MQ-8 and BME280 sensors in environments containing hydrogen. Full article

The future of low-emission aviation lies in electric aircraft propulsion systems based on fuel cells. One of the challenge lies in designing and testing critical components, such as heat exchangers, and studying their impact on system-level performance and power densities. This paper presents the design and experimental characterization of a compact TPMS gyroid-pipe heat exchanger with embedded coolant channels. Thermal–hydraulic performance is quantified using heat transfer rates and pressure drop measurements. Three design variants of the gyroid pipe are prototyped and experiments are performed for a range of mass flow rates and temperatures. The results are presented in terms of heat exchanger characteristics and the design operating points are determined. A comparison is made between the gyroid-pipe design and a conventional louvered-fin-plate heat exchanger. The results show that the louvered-fin-plate design outperforms the gyroid-pipe design, mainly due to higher pressure loss. Additional design variants of the gyroid-pipe heat exchanger, in which the TPMS curvatures are stretched along the air length, improve the thermal and hydraulic performance. The gyroid-pipe heat exchanger design is beneficial as its volumetric and gravimetric power densities are higher than those of a conventional heat exchanger. This is important for reducing the mass of the system and ensuring the feasibility of a fuel cell system in aviation. Full article

Targeted coverage of crushed grass segments under the fruit tree canopy synergistically achieves the agronomic goals of soil moisture conservation, weed suppression, and soil fertility improvement. To address issues like incomplete grass cutting and high risk of damaging fruit trees in complex orchard environments with traditional mowing devices, a lateral grass discharge blade for orchard mowers was designed. Based on airflow field theory, the dynamic basis of the airflow field, critical conditions for carrying crushed grass segments, and their movement laws on the blade and in the air were analyzed to identify key factors affecting discharge. CFD simulations were conducted using the Flow Simulation module of SolidWorks 2021 to explore the effects of the blade airfoil’s long side, short side lengths, and horizontal included angle on the outlet velocity and outlet volumetric flow rate of crushed grass segments, determining the reasonable parameter range. With these three as test factors and the two indicators above, orthogonal tests and parameter optimization were performed via Design-Expert 13.0 software, yielding optimal parameters: long side 125 mm, short side 35 mm, horizontal included angle 60°, corresponding to 9.105 m/s outlet velocity and 0.045 m³/s volume flow rate. A prototype mowing device with these parameters was fabricated for orchard field tests. Results show an average stubble stability coefficient of 94.2%, average over-stubble loss rate of 0.39%, and crushed grass segment distribution variation coefficient of 23.8%, meeting orchard mower operation requirements and providing technical support for orchard weed mowing, coverage, and utilization. Full article

This article presents a database focused on measuring the experimental performance of a pilot parabolic trough collector (PTC) combined with the meteorological conditions corresponding to the installation site. Water was chosen as the fluid to recirculate through the PTC circuit. The data were recorded between August and September, assuming that global radiation was adequate for use in the concentration process. The database comprises seven experimental tests, which contain variables such as time, inlet temperature, outlet temperature, ambient temperature, global radiation, diffuse radiation, wind direction, wind speed, and volumetric flow rate. Based on the data obtained from this pilot PTC system, it is possible to provide relevant information for the installation and construction of large-scale solar collectors. Furthermore, the climatic conditions considered allow key factors in the design of multiple collectors to be determined, such as the type of arrangement (series or parallel) and manufacturing materials. In addition, the data collected in this study are key to validating future theoretical models of the PTC. Finally, considering the real operating conditions of a PTC in conjunction with meteorological variables could also be useful for predicting the system’s thermal performance using artificial intelligence-based models. Full article

Direct injection in hydrogen engines enables flexible combustion control, improves engine efficiency, and reduces the risk of abnormal combustion. However, implementing this injection strategy is challenging due to the need to provide a relatively high volumetric fuel flow rate, achieve a specified degree of mixture stratification, and account for the functional and technological limitations of the injection system. These challenges highlight the relevance and objectives of the present study. The mathematical model of a turbocharged engine cycle has been refined to account for the influence of injection parameters on combustion kinetics. On the basis of mathematical modeling, the injection pressure and injector area were determined to ensure the specified injection conditions. For the late injection strategy, a method was proposed to select the start of injection based on a specified value of the “relative ignition timing” criterion. Engine operation was simulated across the full range of operating modes for both early and late injection strategies. The results show that the late injection strategy increases the maximum indicated thermal efficiency by approximately 2%, reduces peak in-cylinder pressure by about 1 MPa, lowers maximum nitrogen oxide emissions by a factor of 1.4, and ensures knock-free operation across all modes compared to early injection. Full article

Ionic liquids (ILs) are recognized as environmentally friendly solvents due to their high CO₂ absorption capacity, ease of recovery, and chemical stability, making them a promising alternative to conventional solvents for CO₂ capture. In this study, a rate-based mathematical model was developed for a rotating packed bed (RPB) absorber employing 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) as the solvent. The model incorporates mass, energy, and momentum balances, coupled with a thermodynamic model whose parameters were determined using experimental data. The rate-based model was validated against experimental results obtained from the RPB absorber. To enhance predictive accuracy, a sensitivity analysis of various mass transfer correlations was conducted, and simulations were performed based on the outcomes of this analysis. The model provided detailed radial profiles of pressure, gas and liquid flow rates, CO₂ concentration, temperature, volumetric mass transfer coefficients, and both gas- and liquid-phase resistances. The results indicated that the CO₂ capture efficiency and mass transfer coefficients in both phases increased with rotational speed along the bed’s radial direction. Furthermore, the RPB was designed for a flue gas stream from a fired heater in a petrochemical unit containing 10.74 mol % CO₂. The optimal liquid-to-gas ratio at a large scale was found to be 0.3 kg/kg, achieving a CO₂ removal efficiency of 98%. Under these conditions, the required motor power at an outer radius of 1.55 m was approximately 24.6 kW. Furthermore, comparison with a conventional packed bed showed that the liquid-phase volumetric mass transfer coefficient in the RPB was significantly higher, confirming its superior mass transfer performance. Full article

The dynamic response of pump valve motion directly influences the volumetric efficiency of drilling pumps and serves as a critical factor in performance enhancement. This study presents a coupled fluid–structure interaction (FSI) analysis of a novel secondary cushioned pump valve for drilling systems. A validated 3D transient numerical model, integrating piston–valve kinematic coupling and clearance threshold modeling, was developed to resolve the dynamic interactions between reciprocating mechanisms and turbulent flow fields. The methodology addresses critical limitations in conventional valve closure simulations by incorporating a geometrically adaptive mesh refinement strategy while maintaining computational stability. Transient velocity profiles confirm complete sealing integrity with near-zero leakage (<0.01 m/s), while a 39.3 MPa inter-pipeline pressure differential induces 16% higher jet velocities in suction valves compared to discharge counterparts. The secondary cushioned valve design reduces closure hysteresis by 22%, enhancing volumetric efficiency under rated conditions. Parametric studies reveal structural dominance, with increases in cylindrical spring stiffness lowering discharge valve lift by 7.2% and velocity amplitude by 2.74%, while wave spring optimization (24% stiffness enhancement) eliminates pressure decay and reduces perturbations by 90%. Operational sensitivity analysis demonstrates stroke frequency as a critical failure determinant: elevating speed from 90 to 120 rpm amplifies suction valve peak velocity by 59.87% and initial closing shock by 129.07%. Transient flow simulations validate configuration-dependent performance, showing 6.3 ± 0.1% flow rate deviations from theoretical predictions (Q_{t_max} = 40.0316 kg/s) due to kinematic hysteresis. This study establishes spring parameter modulation as a key strategy for balancing flow stability and mitigating cushioning-induced oscillations. These findings provide actionable insights for optimizing high-pressure pump systems through hysteresis control and parametric adaptation. Full article

The universalization of basic sanitation remains a challenge. For the development of sanitation infrastructure projects, it is essential to use water consumption data that accurately reflect reality, ensuring greater precision. This study aimed to determine the per capita contribution to fecal sewage (Cp) in six quilombola residences in Goiás (Brazil). The research was conducted in two phases: (a) a literature review on Cp in similar communities (CpL) and (b) the determination of Cp in six residences from different rural communities (CpP), varying in the number of inhabitants (8, 8, 5, 2, 1, and 1 persons in households R1 to R6, respectively). Flow measurements were obtained using a volumetric flowmeter (nominal flow rate of 1.5 m³/h) installed in the water pipeline supplying the toilet(s) of each household. A dearth of Cp data was observed in the literature, particularly for rural areas. Research on this topic remains in its infancy, as evidenced by the small number of publications (nine papers) published between 2006 and 2022, of which 44.4% reported on-site measurements. In the present study, the CpP ranged from 12.10 L/cap.day to 21.79 L/cap.day, with a mean of 16.22 L/cap.day (CV = 0.239). These calculated values lie within the lower (9.9 L/cap.day) and upper (51.5 L/cap.day) ranges reported in the literature. Generally, estimated data are higher than values calculated from flowrate measurements, highlighting the importance of direct measurements—which can also help reduce construction costs. Therefore, it is recommended that flowrate measurements and Cp calculations be expanded to residences with diverse demographic and geographic characteristics, also incorporating meteorological data, to obtain more accurate results. Full article

This study seeks to investigate the heat dissipation process in a minichannel heat exchanger, commonly employed for cooling electronic components. The analysis centers on two key factors: global thermal resistance (G_TR) and the heat transfer coefficient. The innovation of this study resides in the development and analysis of a mini heat exchanger optimized using chemometric methods to achieve efficient thermal dissipation. Various conditions, including the power source, volumetric flow rate, and ambient temperature, were varied at both low and high levels to assess their impact on these variables and establish the optimal conditions for heat dissipation. The cooling of electronic components, such as processors, remains a topic of ongoing research, as the miniaturization of components through nanotechnology requires enhanced heat dissipation within increasingly smaller spaces. This experimental study identifies the optimal conditions for both G_TR and the heat transfer coefficient within the examined parameters. G_TR is minimized with a power of 30 W, an ambient temperature of 29 °C, and a flow rate of 2.50 L·min⁻¹. The results indicate that electrical power was the most significant variable affecting G_TR, while ambient temperature also played a determining role in the heat transfer coefficient. Full article

Precise flow measurement is crucial in fluid power systems. Especially in combination with pressure, hydraulic power can be particularly beneficial for predictive maintenance and control applications. However, conventional flow sensors in fluid power systems are often invasive, thus disrupting the flow and yielding unreliable measurements, especially under transient conditions. A common alternative is to estimate the flow rate using pressure differentials along a pipe and the Hagen–Poiseuille law, which is limited to steady, laminar, and incompressible flows. This study advances a previously introduced analytical soft sensor, demonstrating its ability to accurately determine the transient pipe flow beyond laminar conditions, without requiring a dedicated flow rate sensor. This method provides a robust and computationally efficient solution for real-world hydraulic systems by applying two pressure transducers. A key contribution of this work is the investigation of signal filtering, revealing that even a simple first-order low-pass filter with a 100 Hz cutoff frequency significantly improves accuracy, which is demonstrated for pulsation frequencies of 5, 10, and 15 Hz, where the filtered results closely match experimental data from a test rig. These findings underscore the soft sensor’s potential as a reliable alternative to traditional flow sensors, offering high accuracy with minimal computational overhead for a wide range of flow conditions. Full article

The use of solar energy is a promising solution to reduce dependence on fossil fuels. Flat-plate collectors (FPCs) are commonly employed to harness solar energy, but their performance is often limited by thermal resistance, surface deterioration, and inefficient heat dissipation. This study investigates the performance enhancement of an FPC integrated with porous copper foam through numerical simulations. The porous foam increases surface area and improves heat transfer by creating a complex flow path for the working fluid. Key parameters such as the porous foam height ratio (S), Darcy number (Da), and volumetric flow rate ($\dot{V}$) are analysed to determine their impact on thermal performance. The results indicate that a maximum Nusselt number (Nu) of 28.85 and an outlet temperature of 306.81 K is obtained for S = 1. A decrease in Da from 10⁻² to 10⁻⁶ and an increase in $\dot{V}$ from 0.25 L/min to 1 L/min enhance the Nu by 5.7% and 8.8%, respectively. The friction factor (f) increases with increases in S, a decrease in Da and an increase in $\dot{V}$. The performance evaluation criteria (PEC) are obtained to be maximum at S = 0.4, Da = 10⁻² and $\dot{V}$ = 0.25 L/min. These findings demonstrate the potential of porous copper foam in improving FPC efficiency. Full article