Energy Conversion Efficiency Research Articles

Spherical Ru/FeOx composite as a bifunctional electrocatalyst for overall water splitting in neutral media

Electrochemical water splitting stands out as a promising technology for H2 production, due to its simplicity and high energy conversion efficiency. Therefore, it is a key issue to develop and design efficient catalysts for overall water splitting (OWS), especially in neutral media. Herein, the present study presents a stable bifunctional electrocatalyst, namely a spherical structure consisting of ruthenium and iron oxide composite supported on iron foam (Ru/FeOx), which was prepared using a simple two-step process. In 1.0M PBS, the optimized Ru/FeOx-300 demonstrates low overpotentials of 30 and 212mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10mAcm-2, respectively. More impressively, Ru/FeOx-300 requires only 1.505V to achieve a current density of 10mAcm-2 and exhibits superior electrochemical stability for 24h in a two-electrode neutral electrolyzer. The outstanding catalytic performance and stability of Ru/FeOx-300 nanospheres for water splitting are attributed to the binder-free integrated structure, the enhanced charge transfer facilitated and the synergistic effect between Ru and FeOx. This study offers a novel approach to the development of high-efficiency electrocatalysts for overall water splitting in neutral media.

Dye-sensitized solar cells achieved with multi-layered SnO2/ZnO composite photoanodes through precise control of thickness and composition

AbstractThe spin coating is cost-effective, straightforward, and highly suitable for the large-scale production of solar cells. In this study, we report the fabrication of SnO2/ZnO composite films for dye-sensitized solar cells (DSCs) using a simplified and cost-effective spin-coating technique on fluorine-doped tin oxide glass substrates. This study introduces a new way of preparing a multi-layered composite thin film using a suspension containing colloidal SnO2 nanoparticles and ZnO nanoparticles followed by sonication and aging of TiO2-free high-efficiency DSCs. Our approach provides a facile way of obtaining a uniform film of tunable thickness with high reproducibility by adjusting the total number of coating cycles. The spin-coating process achieved a nano-sized SnO2-covered ZnO layer, contributing to enhanced conversion efficiency in DSCs. A specific number of seven coating cycles was identified as optimal for achieving the aspirational performance. Under standard AM 1.5 irradiation with an intensity of 100 mW/ cm2, the fabricated SnO2/ZnO composite films revealed an overall energy conversion efficiency of 6.5% with a thickness of 2.06 µm which is impressive for a TiO2-free DSC. This achievement indicates the potential of the developed fabrication process for cost-effective and scalable production of efficient DSCs with SnO2/ZnO composite.

Atomistic insight into the interfacial reaction and evolution between FeCr alloys and supercritical CO2 with impurities

The supercritical CO2 cycle offers high thermal efficiency and flexibility, enhancing energy conversion efficiency and utilization. As the commercialization of supercritical CO2 cycles advances, the stability of the metal-CO2 interface is the key to ensure the safety of this power cycle. In this paper the interfacial reactions between FeCr alloys and CO2 with impurities were investigated using the oxidation thermodynamics and molecular dynamics. With the increase of Cr content in FeCr alloy, the adsorption stability of SO2 and CO2 molecules on the surface of FeCr alloy became stronger, in which CO2 molecules were adsorbed and decomposed in two ways. When the C-O bond was broken, the detached O atom was in a free state or reorganized into O2 molecule, while the CO molecule would be separated from the CO2 molecule. In the initial oxidation stage, adding appropriate amount of H2S in CO2 environment could reduce the diffusion of O atoms from the CO2 molecule to Fe20Cr alloy, and the stress in the oxide film would not increase. The early oxidation behavior of Fe20Cr alloy in CO2 with H2S impurity gas may prove to be an effective method for enhancing its oxidation resistance of Fe20Cr alloy.

Enhancing Wind Energy Conversion Efficiency: A Novel MPPT Approach Using P&O with ADRC Controllers versus PI Controllers with Kp and Ki Optimization via Genetic Algorithm and Ant Colony Optimization

Enhancing Wind Energy Conversion Efficiency: A Novel MPPT Approach Using P&O with ADRC Controllers versus PI Controllers with Kp and Ki Optimization via Genetic Algorithm and Ant Colony Optimization

Proposal design and thermodynamic optimization of an afterburning-type isothermal compressed air energy storage system integrated with molten salt thermal storage

The isothermal compressed air energy storage is a potential technique for large-scale energy storage. In this study, the molten salt thermal storage is integrated with the afterburning-type isothermal compressed air energy storage system, which uses liquid piston compression technique, to enhance the thermal performances. Thermodynamic models of the hybrid energy storage system were developed, and the genetic algorithm was used to optimize multiple parameters to enhance the energy efficiency. Four operation modes, i.e., the high, medium-high, medium-low, and the low output power modes were proposed, to enhance the operational flexibility of the hybrid energy storage system. When the system operates in the operation mode of medium-low output power, a portion of afterburning heat is stored in the molten salt and used in the operation mode of low output power. Results show that the roundtrip efficiency of high, medium-high, medium-low, and the low output power modes are 63.57 %, 59.33 %, 57.13 %, and 83.28 %, respectively. Exergy analysis was carried out to quantify the irreversibilities of key components. In the three modes of operation with afterburning, the combustion chamber has the highest portion of exergy loss, and in the operation mode without afterburning, the exergy loss of heat exchangers is higher than that of expanders.

Experimental investigation of high-temperature latent heat storage packed bed using alloy-based phase change materials

This study explores the effectiveness of a high-temperature latent heat thermal energy storage (LTES) system incorporating Al-Si-based microencapsulated phase change material (MEPCM) composite pellets within a cylindrical packed bed. A parametric analysis was conducted to examine the impact of varying pellet sizes (1, 3, and 5 mm) and airflow rates (20–50 L min−1) on the efficiency of heat storage and discharge. The experimental approach included controlled charging and discharging cycles at temperatures ranging from 500 to 800 °C, with Reynolds numbers between 17.6 and 261. The findings indicate that the system achieved a maximum round-trip efficiency of 0.93, with no substantial gains observed beyond a Reynolds number of 150. Additionally, the results reveal the importance of minimizing heat loss to improve system efficiency, particularly during the discharge phase. These insights are crucial for optimizing the design and operational parameters of high-temperature LTES systems to enhance energy storage efficiency.

Whale Optimized Distributed Computing Data Lake for Energy Storage

This paper presents the Whale Seahorse Optimization Distributed Computing (WSODS) algorithm, a novel approach that combines the Whale Optimization Algorithm (WOA) and Seahorse Optimization Algorithm (SOA) within a distributed computing framework. WSODS aims to address complex optimization challenges across various domains, including power storage systems and data lake architectures. The algorithm's performance was evaluated based on key metrics such as data processing time, system throughput, resource utilization, and scalability. The evaluation results indicate that WSODS significantly enhances system performance. In the context of power storage systems, WSODS improves energy efficiency, storage capacity, charging and discharging rates, and round-trip efficiency. For data lake architectures, WSODS achieves lower data processing times, higher system throughput, and competitive resource utilization while demonstrating good scalability with increasing data loads. The evaluation results indicate that WSODS significantly enhances system performance. In the context of power storage systems, WSODS improves energy efficiency from 92% to 98%, storage capacity from 480 MWh to 500 MWh, charging rate from 45 MW to 55 MW, discharging rate from 55 MW to 64 MW, and round-trip efficiency from 88% to 94% over 100 iterations. For data lake architectures, WSODS achieves lower data processing times (450 seconds compared to 600 seconds for GA), higher system throughput (75 MB/s compared to 55 MB/s for GA), and competitive resource utilization (80% CPU and 65% memory), while demonstrating good scalability with processing time for a 2x data load at 920 seconds compared to 1250 seconds for GA. These findings suggest that WSODS is a versatile and robust optimization tool capable of driving advancements in energy efficiency, data analytics, and distributed computing. Further research and real-world applications are recommended to fully explore its potential and capabilities.

Optimization of the solar cell based on cadmium telluride by adding the CdSeTe absorbing layer (heterostructure simulation)

Cadmium telluride solar cells are among the most common devices for photovoltaic applications. However, the energy conversion efficiency of these elements remains insufficiently high. Using the SCAPS programming environment, research and optimization of a classical thin-film solar cell based on CdTe were carried out. The structure of this element consisted of ITO as a transparent conductive contact, a cadmium sulfide (CdS) layer, and a cadmium telluride (CdTe) absorber layer with a metal contact. To optimize this structure in terms of power conversion efficiency, the influence of the thickness and concentration of acceptor impurities in the CdTe absorbing layer, as well as the influence of the thickness and concentration of donor impurities in the CdS buffer layer, were considered. It was established that the optimal thicknesses for the CdS buffer layer and absorption CdTe layers are 50 nm and 3000 nm, respectively. An additional CdSeTe layer between the CdS and CdTe layers has been proposed as one of the optimization options to improve the device efficiency. The main photovoltaic parameters of such a solar cell were analyzed depending on the thickness of the CdSeTe layer and its selenium content. It has been demonstrated that adding CdSeTe solid solution to the 1500 nm thick CdTe absorber layer increases the efficiency of the solar cell by 6.84 %. The main photovoltaic characteristics of CdS/CdTe and CdS/CdSeTe/CdTe solar cells were compared. The results showed that the simulated CdS/CdSeTe/CdTe structure provides better photoconversion efficiency in the AM1.5G light spectrum compared to the classical CdS/CdTe structure. Such elements can be used to form highly efficient solar panels

Savanna Plants Have a Lower Hydraulic Efficiency than Co-Occurring Species in a Rainforest

A plant species can have diverse hydraulic strategies to adapt to different environments. However, the water transport divergence of co-occurring species in contrasting habitats remains poorly studied but is important for understanding their ecophysiology adaptation to their environments. Here, we investigated whole-branch, stem and leaf water transport strategies and associated morphology traits of 11 co-occurring plant species in Yuanjiang valley-type savanna (YJ) with dry–hot habitats and Xishuangbanna tropical seasonal rainforest (XSBN) with wet–hot habits and tested the hypothesis that plants in YJ have a lower water transport efficiency than co-occurring species in XSBN. We found high variation in whole-branch, stem and leaf hydraulic conductance (Kshoot; Kstem and Kleaf) between YJ and XSBN, and that Kstem was significantly higher than Kleaf in these two sites (Kstem/Kleaf: 16.77 in YJ and 6.72 in XSBN). These plants in YJ with significantly lower Kshoot and Kleaf but higher sapwood density (WD) and leaf mass per area (LMA) showed a lower water transport efficiency regarding less water loss and the adaptation to the dry–hot habitat compared to co-occurring species in XSBN. In contrast, these co-occurring plants in XSBN with higher Kshoot and Kleaf but lower WD and LMA tended to maximize water transport efficiency and thus growth potential in the wet–hot habitat. Our findings suggest that these co-occurring species employ divergent hydraulic efficiency across YJ and XSBN so that they can benefit from the contrasting hydraulic strategies in adaptation to their respective habitats.

Energy Advantages and Thermodynamic Performance of Scheffler Receivers as Thermal Sources for Solar Thermal Power Generation

This article examines the prospects of Scheffler solar receivers integrated into renewable energy power plants for civil applications. This kind of solar receiver can offer satisfactory energetic performance with acceptable energy conversion efficiency when compared to other technologies to harness solar energy since the high-quality focal receiver can reduce heat losses also supposing great levels of evaporation temperature. In this research, energetic optimization and a broad assessment of Scheffler-type solar receivers are thoroughly conducted for variable sun radiation and considering a broad range of working conditions. To achieve this goal, thermodynamic optimization of the chief factors was attained via a numerical model which calculated the energy efficiency of the Scheffler solar receiver at part-load working conditions by computing all energy losses negatively affecting the heat exchange phase in the cavity receiver. The results obtained in this study show that the solar collector efficiencies of Scheffler receivers appear more promising than that of usual parabolic trough collectors; moreover, Scheffler receivers persisted with less sensitivity to reductions in solar radiation intensity. For these reasons, solar power systems based on Scheffler-type systems can be used from tens to hundreds of kW to ensure the energetic supply of small urban settlements with acceptable efficiency, optimistic investments, simple construction and reduced overall sizes.

Intracellular Gold Nanocluster/Organic Semiconductor Heterostructure for Enhancing Photosynthesis

AbstractPhotosynthetic microorganisms, which rely on light‐driven electron transfer, store solar energy in self‐energy carriers and convert it into bioenergy. Although these microorganisms can operate light‐induced charge separation with nearly 100 % quantum efficiency, their practical applications are inherently limited by the photosynthetic energy conversion efficiency. Artificial semiconductors can induce an electronic response to photoexcitation, providing additional excited electrons for natural photosynthesis to improve solar conversion efficiency. However, challenges remain in importing exogenous electrons across cell membranes. In this work, we have developed an engineered gold nanocluster/organic semiconductor heterostructure (AuNCs@OFTF) to couple the intracellular electron transport chain of living cyanobacteria. AuNCs@OFTF exhibits a prolonged excited state lifetime and effective charge separation. The internalized AuNCs@OFTF permits its photogenerated electrons to participate in the downstream of photosystem II and construct an oriented electronic highway, which enables a five‐fold increase in photocurrent in living cyanobacteria. Moreover, the binding events of AuNCs@OFTF established an abiotic‐biotic electronic interface at the thylakoid membrane to enhance electron flux and finally furnished nicotinamide adenine dinucleotide phosphate. Thus, AuNCs@OFTF can be exploited to spatiotemporally manipulate and enhance the solar conversion of living cyanobacteria in cells, providing an extended nanotechnology for re‐engineering photosynthetic pathways.

An active and durable perovskite electrode with reversibly phase transition-induced exsolution for protonic ceramic cells

Protonic ceramic cells (PCCs) possess great application potential, attributed to their cleanliness and high energy conversion efficiency. However, designing active air electrodes with both high stability is challenging. Herein, we report a nanospinel-modified perovskite oxide, Nd0.5Ba0.5Mn0.7Co0.15Ni0.15O3−δ-(CoxNiy)3O4 (CNO@NBMCN), obtained by a reversibly phase transition-induced exsolution process, as a highly active and durable air electrode for PCCs. Phase-field simulations reveal the intrinsic mechanism of nanoparticles strongly pinning to the substrate in a high-temperature oxidizing environment. The CNO@NBMCN electrode exhibits remarkable low area specific resistance (0.38 Ω cm2 at 600 °C) and exceptional stability (degradation rate 0.01 % h−1). It is confirmed by soft X-ray absorption spectroscopy that the construction of the heterostructure leads to more distortion in Mn–O octahedra and weaker metal–oxygen bonds, thereby contributing to the formation of oxygen vacancies. And the exceptionally high durability supported by both fast ion surface exchange and charge transfer at triple-phase boundaries. A single cell with the CNO@NBMCN air electrode achieves outstanding performances in the fuel cell (peak power density of 1.28 W cm−2) and electrolysis modes (current density of −2.14 A cm−2 at 1.3 V), recorded at 700 °C. This work inspires innovative design concepts for robust heterogeneous electrocatalysts.

A novel bi-level optimal strategy-assisted design boosting discovery of specific surface area of perovskite oxide for effective photocatalysis

Due to the inherent property of materials, photocatalysis plays a crucial role in diverse applications, such as the degradation of organic pollutants, fuel production, and nitrogen fixation. Perovskites, in particular, are remarkable for their high light absorption rate and energy conversion efficiency within the visible light range, thereby positioning them as promising photocatalysts. Given that specific surface area (SSA) is a critical metric for evaluating photocatalytic performance, accurately and quickly predicting the SSA of perovskites has emerged as a key area of technical research. Therefore, it is essential to explore the relationship between potential materials descriptors and SSA, which can significantly expedite the discovery of photocatalyzed perovskite materials with high SSA. In this study, we proposed a bi-level optimization method that combines descriptors identified strategy and model optimization strategy for predicting the SSA of unknown perovskite candidates, thereby elucidating the relationship between material features and SSA. Initially, at the upper level, the Gradient Boosting Regression combined with Recursive Feature Elimination (RFE-GBR) method was employed to identify crucial features that are closely correlated with the SSA of photocatalyzed perovskites. Subsequently, the Sure Independence Screening.Sparsifying Operator (SISSO) was utilized to develop new descriptors that exhibited strong correlations with SSA. Based on refined descriptors identifiied at the upper level, at the lower level, the optimal model strategy was obtained by Improved Osprey Optimization Algorithm (IOOA) using golden sine strategy and Gradient Boosting Regression (GBR) regression to tune the key parameters of GBR for optimizing SSA. The optimal designing method achieved remarkable predictive performance with R2 (R-squared) score of 0.90 and MAE (Mean Absolute Error) of 3.97 m2/g, along with 5-fold cross-validation. Then this method was applied to predict the SSA of 300 unidentified ABO3 perovskites. Comparison with experimental data revealed that our approach significantly accelerated the development of perovskite materials with superior photocatalytic properties, showing the potential of our model in advancing the field of photocatalysis.

Novel Structures for PV Solar Cells: Fabrication of Cu/Cu2S-MWCNTs 1D-Hybrid Nanocomposite

The production of cost-effective novel materials for PV solar cells with long-term stability, high energy conversion efficiency, enhanced photon absorption, and easy electron transport has stimulated great interest in the research community over the last decades. In the presented work, Cu/Cu2S-MWCNTs nanocomposites were produced and analyzed in the framework of potential applications for PV solar cells. Firstly, the surface of the produced one-dimensional Cu was covered by Cu2S nanoflake. XRD data prove the formation of both Cu and Cu2S structures. The length and diameter of the one-dimensional Cu wire were 5–15 µm and 80–200 nm, respectively. The thickness of the Cu2S nanoflake layer on the surface of the Cu was up to 100 nm. In addition, the Cu/Cu2S system was enriched with MWCNTs. MWCNs with a diameter of 50 nm interact by forming a conductive network around the Cu/Cu2S system and facilitate quick electron transport. Raman spectra also prove good interfacial coupling between the Cu/Cu2S system and MWCNTs, which is crucial for charge separation and electron transfer in PV solar cells. Furthermore, UV studies show that Cu/Cu2S-MWCNTs nanocomposites have a wide absorption band. Thus, MWCNTs, Cu, and Cu2S exhibit an intense absorption spectrum at 260 nm, 590 nm, and 972 nm, respectively. With a broad absorption band spanning the visible–infrared spectrum, the Cu/Cu2S-MWCNTs combination can significantly boost PV solar cells’ power conversion efficiency. Furthermore, UV research demonstrates that the plasmonic character of the material is altered fundamentally when CuS covers the Cu surface. Additionally, MWCN-Cu/Cu2S nanocomposite exhibits hybrid plasmonic phenomena. The bandgap of Cu/Cu2S NWs was found to be approximately 1.3 eV. Regarding electron transfer and electromagnetic radiation absorption, the collective oscillations in plasmonic metal-p-type semiconductor–conductor MWCNT contacts can thus greatly increase energy conversion efficiency. The Cu/Cu2S-MWCNTs nanocomposite is therefore a promising new material for PV solar cell application.

Performance study of an innovative dual injection mode injector for marine low-speed dual-fuel engine

Marine low-speed dual-fuel engines typically have two sets of fuel injection system, main-injection and micro-injection. In order to make the fuel injection system of marine low-speed dual-fuel engine compact in structure and flexible in injection control, an innovative dual injection mode injector (DIMI) which can achieve both the functions of main-injection and micro-injection was proposed. The switching between main-injection and micro-injection mode of the injector is achieved through the collaborative control of dual solenoid valves. Based on the constructed AMESim model, the injection quantity characteristic and hydraulic efficiency of the DIMI were investigated under different working conditions and injection modes. The results show that, when the DIMI in main-injection mode achieves injection quantity characteristic similar to those of a traditional electronically controlled injector (TECI), the electromagnetic forces of solenoid valves of the DIMI are less required to 80% of that of the TECI, and the fuel return quantity and hydraulic efficiency of the DIMI are comparable to those of the TECI under the same working conditions. By changing the minimum limit height of the needle of the DIMI under micro-injection mode, different ranges of micro-injection quantity could be designed according to the requirements of the engine, and the control accuracy of injection pulse width (IPW) on micro-injection quantity is higher than on main-injection quantity. Both the hydraulic efficiency of the DIMI under main-injection and micro-injection mode increase with the rail pressure and IPW in the small IPW range, then gradually tend to be saturated with the increase of IPW. As the minimum limit height of the needle increases, the injection quantity and hydraulic efficiency of the DIMI under micro-injection mode increases overall, however, the saturation values of the hydraulic efficiency in micro-injection mode under different needle minimum limit heights are still smaller than those in main-injection mode.

Advanced Wastewater Treatment: Synergistic Integration of Reverse Electrodialysis with Electrochemical Degradation Driven by Low-Grade Heat

The reverse electrodialysis heat engine (REDHE) represents a transformative innovation that converts low-grade thermal energy into salinity gradient energy (SGE). This crucial form of energy powers reverse electrodialysis (RED) reactors, significantly changing wastewater treatment paradigms. This comprehensive review explores the forefront of this emerging field, offering a critical synthesis of key discoveries and theoretical foundations. This review begins with a summary of various oxidation degradation methods, including cathodic and anodic degradation processes, that can be integrated with RED technology. The degradation principles and characteristics of different RED wastewater treatment systems are also discussed. Then, this review examines the impact of several key operational parameters, degradation circulation modes, and multi-stage series systems on wastewater degradation performance and energy conversion efficiency in RED reactors. The analysis highlights the economic feasibility of using SGE derived from low-grade heat to power RED technology for wastewater treatment, offering the dual benefits of waste heat recovery and effective wastewater processing.

Spider Webs‐Inspired Aluminum Coordination Hydrogel Piezoionic Sensors for Tactile Nerve Systems

AbstractPiezoionics, a new frontier that employs mobile ions as energy and charge carriers, plays an important role in new energy and intelligent electronics. However, a significant challenge consists in balancing the structural design of metal ions coordination hydrogel (HG‐MI) piezoionics for current conduction, voltage generation, and especially mechanical adaptability. Herein, inspired by the spider webs' unique structure, a strategy by realizing the full potential of metal‐ligand ions ([(OH)Cl2]3−) to facilitate the keggin‐type structure AlOHAlOH generation together with activate functional carboxyls is introduced. Impressively, the whole property of the product HG‐AlPAC, especially the mechanical performance is improved. For example, the toughness of HG‐AlPAC is 2.75 MJ m−3, more than twofold that of traditional HG‐AlAS/AC/AN samples. Due to the stable fixation of ─Al─OH─ thus promoting Cl− separation upon external force, HG‐AlPAC achieves a piezoionic coefficient of 0.89 mV KPa−1 and energy conversion efficiency of 1.29%, promising for mechanical‐electrical conversion and sensing. Combined with the good mechanical performance with the excellent piezoionic properties, underscores its potential as a tactile nerve system of analgesia patients to prevent them from being injured. This work intends to provide a stride toward mechanically robust self‐powered piezoionic sensors and offer insights into ionotropic materials for energy harvesting, human‐machine interaction, and biointerface.

Enhancing Thermoelectric Performance of Mg3Sb2 Through Substitutional Doping: Sustainable Energy Solutions via First-Principles Calculations

Mg3Sb2-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg3Sb2 via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg3Sb2, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 106 S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 106 S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg3Sb2 as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions.

Enhancing hydraulic efficiency in jet impingement sprinklers: Comparative analysis of aperture ratios compared with non-impingement sprinklers

A jet impingement sprinkler was designed based on asymmetric collision between the primary and secondary jets to replace traditional rotating sprinklers that require additional water distribution devices to provide suitable water distribution at low pressures. The study focuses on the ratio of apertures between primary and secondary nozzles, deriving a theoretical relationship based on jet momentum. The factors contributing to the variation in hydraulic performance between jet-impingement and non-impinging sprinklers are elucidated by combining hydraulic performance experiments with experiments using high-speed photography (HSP). The results show that the developed jet impingement sprinkler achieved a smoother water distribution trend. The wetted radius and Christiansen's uniformity coefficient of the jet impingement sprinkler were evaluated using the Criteria Importance via the Intercriteria Correlation (CRITIC) method. A comparison of the average scores shows that an aperture ratio of 1.66 performs best under full pressure. By contrast, an aperture ratio of 1.33 exhibited superior performance at low pressure. Jet deflection angle and jet breakup length were obtained through HSP experiments. The relative error between the measured and theoretical jet deflection angles was less than 5%, demonstrating the reliability of the proposed theoretical calculation method. A non-linear curve was used to establish the relationship among the aperture ratio, diameter of the primary nozzle exit, jet breakup length, average measured jet deflection angle, working pressure, and wetted radius. The relative error between the calculated and measured values was within 4%, indicating the suitability of the new formula for calculating the wetted radius of jet impingement sprinklers.

Liquid Water Transport and Distribution in the Gas Diffusion Layer of a Proton Exchange Membrane Fuel Cell Considering Interfacial Cracks

The proton exchange membrane fuel cell (PEMFC), with a high energy conversion efficiency, has become an important means of hydrogen energy utilization. However, water condensation is unavoidable in the PEMFC because of low operating temperatures. The impact of liquid water on PEMFC performance and stability is significant. The gas diffusion layer (GDL) provides a critical transport path for liquid water in the PEMFC. Liquid water saturation and distribution in the GDL determine water flooding and mass transfer efficiency in the PEMFC. In this study, focusing on the effects of the water introduction method, osmotic pressure, and contact angle, the liquid water transport in the GDL was numerically investigated based on a pore-scale model using the volume of fluid (VOF) method. The results showed that compared with the conventional water introduction method without cracks, the saturation and spatial distribution of water inside the GDL obtained in the simulation were more consistent with the experimental results when the water was introduced through the microporous layer (MPL) crack. It was found that increasing the osmotic pressure resulted in a faster rate of water penetration, faster approaching the steady-state performance, and higher saturation. The ultra-high osmotic pressure contributed to the secondary breakthrough with a significant increase in saturation. Increasing the contact angle caused higher capillary resistance, especially in the region with small pore sizes. At a constant osmotic pressure, as the contact angle increased, the liquid water gradually failed to penetrate into the small pores around the transport path, causing saturation reduction and an ultimate failure to break through the GDL. Increasing the contact angle contributed to a higher breakthrough pressure and secondary breakthrough pressure.