Harsh Operating Conditions Research Articles

A Robust Control Strategy for Effective Field-Oriented Control of PMSMs

Field-Oriented Control (FOC) is widely recognized as a standard framework for Permanent Magnet Synchronous Motor (PMSM) drives. Linear control techniques are commonly employed in designing controllers for this strategy. However, traditional control methods often exhibit performance limitations and reduced robustness, particularly under harsh operating conditions, which makes the FOC structure less appealing and less effective. To address and overcome these challenges, this study proposes a Second-order Non-singular Terminal Sliding (SNTS) mode approach to achieve fast, accurate, and robust tracking for the FOC control structure applied to PMSM drives. The SNTS method combines the benefits of non-singular terminal sliding mode and second-order control laws. This approach ensures rapid and precise tracking while minimizing steady-state errors by using a nonlinear terminal sliding mode surface instead of a linear one. Furthermore, the system state transitions smoothly along the sliding mode surface with continuous functions, which reduces chattering around the sliding surface. The second-order control law incorporated into this method helps mitigate chattering and achieve fast convergence. The Lyapunov stability theory is employed to verify the stability of the SNTS technique designed for the PMSM system. Simulation and experimental validation on a hardware platform confirm the effectiveness and superiority of the proposed SNTS method, demonstrating its capability to enhance the performance of speed controllers for PMSM drives.

Study on the change of the oil-paper insulation’s AC conductivity characteristics based on dielectric response in frequency domain

Oil-immersed power equipment (transformers and high voltage bushings) are key components of power systems. Oil-paper insulation has endured complex and harsh operating conditions when used as a primary insulation system, so it is essential to determine the insulation state of oil-paper insulation system to ensure a stable operation for the power grid. The oil-paper insulation’s conductivity behavior can effectively characterize the degree of insulation deterioration. However, the relationship between the alternating current (AC) and direct current (DC) conductivity behavior for oil-paper insulation systems is still unclear in current research, resulting in limitations in the traditional evaluation model’s application. Therefore, this paper uses oil-paper insulation materials under different aging to carry out relevant research about the changing features of the complex AC conductivity under different test temperature environments. The influence of oil-paper insulation aging, test temperature, and excitation frequency on the complex AC conductivity is verified. Considering the correlation between low-frequency AC conductivity and DC conductivity, the frequency range of AC conductivity is extended by means of frequency temperature and conductance double translation. The temperature dependence of the AC conductivity behavior is defined over a wide frequency test range. The relaxation polarization process dominated the AC conductivity variation law is obtained. The impact of experimental temperature and insulation aging on the cumulative characteristic parameters of AC ionic mobility is clarified. This study theoretically corrects the traditional calculation model for AC conductivity of oil-paper insulation. The bias in conductivity calculations caused by only considering a single relaxation polarization process is eliminated. The conductivity model that can characterize multiple relaxation polarization processes in the dielectric is established. This model provides theoretical support for the later assessment of oil-paper insulation state depending on conductance behavior.

Interconnected expanded graphite/stearic acid networks for self‐lubricating PA6 composites with excellent heat dissipation performance

AbstractThe improvement in social production efficiency demands increasingly faster mechanical operation speeds. However, under high‐speed friction conditions, the frictional heat generated by nylon 6 (PA6) components is difficult to dissipate efficiently, leading to severe wear and subsequently threatening the safe operation of the equipment. In this work, interconnected expanded graphite/stearic acid (EG/SA) networks in PA6 composites were constructed to achieve fast frictional heat dissipation and self‐lubricating properties by a simple hot‐pressing method. The synergistic lubrication of EG and SA results in PA6 composites with a low coefficient of friction (COF) of 0.12, a 74.5% reduction compared to pure PA6. The low COF reduces the generation of frictional heat, while the conduction and absorption of frictional heat by the EG/SA network accelerates the dissipation of frictional heat, ultimately lowering the contact temperature from 106.9°C to 40.6°C. The specific wear rate of the PA6 composite is as low as 1.7 × 10−5 mm3 N−1 m−1, which is 90.1% lower than that of pure PA6. This study provides a new solution for the rapid dissipation of frictional heat in polymer composites under harsh operating conditions and broadens the application range of wear‐resistant polymer composites.Highlights Expanded graphite (EG) prevents stearic acid from leaking through adsorption. The interconnected EG network transfers frictional heat to stearic acid. The phase transition of stearic acid can absorb heat and promote lubrication. The low COF and high heat dissipation make PA6 composites highly wear‐resistant.

Design Principle and Regulation Strategy of Noble Metal‐Based Materials for Practical Proton Exchange Membrane Water Electrolyzer

AbstractGreen hydrogen holds immense promise in combating climate change and building a sustainable future. Owing to its high power‐to‐gas conversion efficiency, compact structure, and fast response, the proton exchange membrane water electrolyzer (PEMWE) stands out as the most viable option for the widespread production of green hydrogen. However, the harsh operating conditions of PEMWE make it heavily dependent on noble metal‐based catalysts (NMCs) and incur high operational and maintenance costs, which hinder its extensive adoption. Hence, it is imperative to improve the performance and lifespan of NMCs and develop advanced components to reduce the overall costs of integrating PEMWE technology into practical applications. In light of this, the fundamental design principles of NMCs employed in acidic water electrolysis are summarized, as well as recent advancements in compositional and structural engineering to enhance intrinsic activity and active site density. Moreover, recent innovations in stack components of practical PEMWE and their impact on cost‐benefit and lifespan are presented. Finally, the current challenges are examined, and potential solutions for optimizing NMCs and PEMWE in electrocatalytic hydrogen production are discussed.

Bismuth sensitized iron oxide on exfoliated graphene oxide (Bi–Fe2O3@GO) for oxygen evaluation reaction

Electrochemical water splitting is a promising approach towards a sustainable and renewable energy source. However, the demand for high anodic potential and sluggish kinetics of oxygen evolution reaction (OER) restrict the efficiency and feasibility of the water-splitting process. In this quest, transition metal oxides and alloys are considered potential candidates owing to their natural occurrence and high redox potential for OER. However, many associated challenges in their use are still there to be addressed. Here, we designed a new class of bismuth-doped iron oxide on exfoliated graphene oxide by optimizing the metal loading on the conductive support to facilitate the flow of charge during catalysis. The catalytic ability of the synthesized Bi-doped nanocomposites was evaluated in activating the OER under extreme alkaline conditions (1 MKOH). On screening different combinations, 20Bi–Fe2O3@GO was identified as the most efficient and sustainable electrocatalyst even under harsh operating conditions, with an onset potential of 1.48 V and a Tafel slope of 65 mV/dec. The current study offers a new class of Bi-doped electrocatalysts, where the precise doping of Bi and the optimized loading of metal was found the key to achieving low onset potential and high current density to initiate OER.Graphical abstract

Operation study of the photovoltaic thermal heat pump integrated energy system under trigeneration condition and harsh conditions

In recent years, the photovoltaic thermal heat pump has gained significant attention as a near zero-carbon energy technology, due to the comprehensive ability to provide heating in winter, cooling in summer, photovoltaic power generation and domestic hot water throughout the year. However, owing to the incomplete research on the system operating characteristics in trigeneration condition and harsh conditions, the production performance and operational stability of the photovoltaic thermal heat pump were not widely recognized. In view of the above problems, the following studies were conducted in this paper: First, the integrated energy system based on the modular photovoltaic thermal heat pump was designed and constructed. Then, the system operation in severe hot and cold season was carried out and the operational stability of the system under harsh operating conditions was demonstrated sufficiently. Afterwards, the operation of the system under the continuous trigeneration operation were analyzed. During the 7-day trigeneration operation, the average hot water output was 12.12 tons and the average photovoltaic power generation was 88.5 kWh in the daytime heating operation. Besides, the average coefficient of cooling performance was 2.32 in the nighttime cooling operation and the effective cooling-supply time of the system was approximately 4 h.

Endomelanconiopsis endophytica Lipase Immobilized in Calcium Alginate for Production of Biodiesel from Waste Cooking Oil

The increasing global demand for biodiesel is due to the urgent need to replace fossil diesel with a fuel based on renewable energy sources. Although chemical catalysis is widely used to produce biodiesel, it uses harsh operating conditions, has high energy consumption, and generates unwanted byproducts. In this scenario, biocatalysis stands out as an efficient and environmentally friendly alternative to chemical catalysis. In biocatalysis, the use of immobilized enzymes plays an important role in the reduction in costs. In this sense, we investigated the use of the lipase produced by an Amazonian endophytic fungus in an immobilized form in the transesterification of waste cooking oil for biodiesel production. The fungus Endomelanconiopsis endophytica QAT_7AC demonstrated a high production of lipase. The lipolytic extract was precipitated in ethanol, which increased the specific enzyme activity. The lipolytic extract and the precipitated lipolytic extract were immobilized in calcium alginate beads. Immobilization efficiency was over 89%. The immobilized biocatalysts showed thermal stability and were used in the production of biodiesel using waste cooking oil and ethanol. It was possible to reuse them for up to four reaction cycles, with yields greater than 70%. These results prove the efficiency of immobilized biocatalysts in the production of biodiesel from waste oils.

Theoretical investigation on propane dehydrogenation over extraframework Ga hydride species trapped at Al-pairs in MFI zeolite

Ga/ZSM-5 is widely used to catalyze propane dehydrogenation (PDH). For the harsh operation conditions, the detailed active species, and the plausible reaction pathways that are responsible for the observed superior PDH performance remain unresolved for Ga/ZSM-5. Reduced extraframework Ga hydride species trapped at zeolite framework Al-pairs, including b[GaH]2+, [Ga]+-BAS, [GaH2]+-BAS, etc. are an important kind of Ga species known as active species for PDH. In this work, the PDH pathways these over these Ga species were investigated theoretically at temperatures and pressures relevant to experiments. We showed that dynamically generated undercoordinated b[GaH]2+ would exhibit significantly higher catalytic activity at PDH conditions as compared with other Ga hydride species. The most plausible PDH pathway over b[GaH]2+ is the carbenium pathway. The Ga species and BAS act in concert in promoting the H2 elimination and β-H transfer, and in turning PDH efficient. Ga hydride species may also form as intermediates along the PDH pathways as active sites for subsequent activation and conversion of propane, suggesting the evolution of Ga hydride species trapped by Al-pairs in Ga/ZSM-5 at operation conditions. The findings are expected to pave the way for better understanding of the experimentally observed operation condition dependent PDH performance of Ga/ZSM-5.

Experimental study on fireproof of aviation lubrication oil tank

Abstract This paper presents an experimental study on the fireproof performance of aeroengine lubrication oil tanks. By constructing a simplified lubrication oil tank model and simulating the harsh operating conditions of engine fires, the oil tank was exposed to flames generated by a standard burner for testing. The study monitored and recorded key parameters such as temperature, pressure, flow rate, and phase changes within the tank. The results indicate significant differences in the temperature distribution characteristics of the tank walls under different inlet temperatures and flow conditions. In the rigorous 15-minute flame test, all tests successfully completed the fire verification process.

Development of hybrid first principles – Artificial intelligence models for transient modeling of power plant superheaters under load-following operation

This paper develops different approaches for synergistic integration of physics-based models with data-driven models for modeling of high temperature power plant superheaters. Two types of data-driven models are developed, namely all-nonlinear static-dynamic neural network models as well as models obtained using a Bayesian machine learning approach. Series, integrated, and parallel coupling of first-principles models and data-driven models are proposed. Algorithms for solving the training problems for the data-driven models and for simulation of the hybrid models are developed. The developed approach is applied to high temperature power plant superheaters that face considerable modeling and measurement challenges. Measurement challenges arise due to harsh operating conditions that not only make placement of sensors difficult, but life of the placed sensors very limited. Modeling challenges arise due to complex inhomogeneous spatial distribution of flue gas and steam flowrates, especially under load-following operation and uncertainties in heat transfer characteristics because of multiple factors such as stochastic spatio-temporal variation of ash deposits on the superheater tubes in coal-fired power plants, internal oxide scale formation in the tubes, etc. First-principles two-dimensional differential–algebraic equation models of two industrial superheaters, one from a natural gas combined cycle plant and another from a coal-fired power plant, are developed. The results from the models are compared against industrial operational data. For all cases studied in this work, it is observed that both for steady-state and dynamic data, the hybrid models have much higher accuracy than when only the respective first-principles models are used. For example, during prediction of the average outside tube wall temperature of superheater tubes at the combined cycle power plant, the root mean squared error observed for the standalone first-principles model improved from 12.3 °C to 0.5 °C post hybridization with data-driven models. Similarly, while predicting the main steam outlet temperature in the coal-fired plant, the hybrid models resulted in reduction of the root mean squared error value from 19.5 °C to around 2 °C. In addition, the hybrid models yield highly resolved spatio-temporal temperature profiles that can be helpful for developing monitoring approaches of these critical components under load-following operation.

Ceramic matrix composites for corrosion-resistant next-generation nuclear reactor systems: A conceptual review of enhancements in durability against molten salt attack

Ceramic matrix composites (CMCs) are emerging as a key material class for enhancing corrosion resistance in next-generation nuclear reactor systems, particularly in high-temperature molten salt environments. These environments, critical for advanced nuclear reactors such as molten salt reactors (MSRs), present severe challenges, including aggressive chemical attacks that degrade traditional structural materials over time. This conceptual review explores the development and application of CMCs to improve the durability and corrosion resistance of nuclear reactors exposed to molten salt attacks. CMCs, which consist of ceramic fibers embedded in a ceramic matrix, offer significant advantages, such as high thermal stability, mechanical strength, and improved corrosion resistance compared to conventional materials. This review examines how CMCs can be tailored to withstand harsh operational conditions, with a focus on the selection of ceramic phases, fiber-matrix interactions, and innovative fabrication techniques that enhance their protective capabilities. Key challenges addressed include the optimization of composite design to resist molten salt corrosion, the effects of temperature on the material properties, and the long-term stability of CMCs under extreme conditions. Advances in surface treatments, coatings, and the development of hybrid CMC systems are also discussed, highlighting their potential to further enhance durability. The review outlines the use of advanced characterization techniques, such as high-temperature corrosion testing and in situ microscopy, to evaluate CMC performance in molten salt environments. Additionally, it identifies knowledge gaps in current research, emphasizing the need for long-term studies on CMC behavior under realistic reactor conditions. This review concludes by proposing future research directions and technological advancements required to integrate CMCs into next-generation nuclear reactor designs, aiming to improve system reliability and operational safety.

Investigation of softening in hardfaced layers during welding

Hardfacing is a widely used technique to create wear-resistant layer on the base material to ensure good durability and performance under harsh operating conditions. However, despite its effectiveness in improving wear resistance, hardfaced layers can sometimes exhibit softening phenomena during welding, compromising their mechanical properties and overall performance. In this research, the effect of heat input was investigated in case of Fe-based hardfacing material with high Cr content. 4 different heat inputs were applied with gas metal arc welding and significant differences were determined in hardnesses, which can be influential to the lifetime of hardfaced parts. Hardness drop happens in the heat-affected zones between the hardfaced layers and the highest heat input causing the most significant softening (20% hardness drop).

Fluorescent Protein PEGylation for Stable Photon Manipulation in Deep‐Red Light‐Emitting Devices

AbstractPEGylation is a classic strategy to reduce denaturation and immunogenicity in therapeutic proteins, bioimaging, and drug delivery. However, this concept has not been applied to incorporate biogenic materials as functional components in optoelectronics. Herein, PEGylation is rationalized as an effective tool to stabilize fluorescent proteins in solid‐state photon manipulation down‐converters integrated into bio‐hybrid light‐emitting diodes. In short, the archetypal red‐emitting protein mCherry is nonspecifically PEGylated with methoxypolyethylene glycols (mPEG) chains of different lengths (mPEG‐350/‐750/‐2000). These derivatives hold the same photoluminescence figures‐of‐merit of mCherry, but an improved resistance against organic solvents, pH, temperature, and polymers (in solution/dry‐coatings) upon increasing the mPEG length. Indeed, the best‐performing mCherry‐mPEG‐2000 adduct leads to deep‐red devices with threefold enhanced color stability (>300 h) under harsh operation conditions (150 mW cm−2) over the prior art. Different device architectures along with spectroscopic, thermocycling, and electrochemical impedance spectroscopy studies of the prepared coatings aid in rationalizing that PEGylation successfully reduces i) nonreversible thermal denaturation, ii) aggregation in solid‐state, and iii) photo‐induced oxidation and H+‐transfer deactivation of the chromophore, since oxygen diffusivity and H+‐reorganization across the protein skeleton are slowed down by strong H+‐bonding/hydrophobic mCherry‐mPEG interactions. Hence, this simple supramolecular modification is of utmost relevance for future advances in protein‐based optoelectronics.

ENHANCING MECHANICAL RELIABILITY OF SILVER SINTERED JOINTS WITH COPPER NANOWIRES IN HIGH-POWER ELECTRONIC DEVICES

Abstract This study investigated the mechanical reliability of silver-sintered die attachment under harsh operating conditions, and explored the advantages of adding copper nanowires to improve the bond's mechanical properties. Samples were prepared using a template-assisted electrochemical deposition process to coat the substrate surface with copper nanowires, and were subjected to thermal aging at various temperatures to assess their mechanical reliability. Results showed that the incorporation of copper nanowires in the substrate interface significantly reduced degradation in shear strength as a result of thermal aging, acting as mechanical reinforcement and improving the interfacial resilience against mechanical shear stress. The addition of copper nanowires also reduced the void formation in the thermal aging, resulting in a more robust and reliable bond. The study demonstrates the potential of using copper nanowires as a reinforcing agent to enhance the mechanical properties of silver-sintered die attachment, particularly for high-temperature applications.

High dynamic performance based by sliding mod control of quadrotor MAV

The paper focuses on strong control of high dynamic performance based on the sliding mode in order to control the quadrotor MAV. The model used in the simulation is the Newton-Euler model, and also choose the Mambo Parrot quadrotor parameters, to improve the latter's performance in terms of accuracy and robustness in case the impedance control chosen by the manufacturer needs to be changed. The results of which gave effectiveness and efficiency compared to classical controls PID and sliding mode. High dynamic performance control (HDP) is a type of control system designed to provide the highest level of performance over a wide range of operating conditions. This control is not a regulator but an organizing technique. It uses a prediction-based approach to anticipate rapid variations in system states and disturbances and to generate real-time commands to correct tracking errors and maintain system stability. This approach allows HDP control to achieve high performance while maintaining system stability, even under harsh operating conditions.

تحسين جدول صيانة المعدات الدوارة باستخدام معيار التكلفة المتوقعة الكلية ومعيار تباين التكلفة

Inspection and maintenance of rotating equipment have gained credit in petrochemicals, refineries and oil and gas industries over the past decades due to the hazard failures resulting from overpressures and fluctuated temperatures surrounding the industrial zone. Therefore, any equipment operating under the harsh operational conditions should take the cost and time of inspection and maintenance into account. Maintenance of rotating equipment is an expensive event in terms of the cost and time, which are the driving forces to improve the maintenance performance. The paper aimed at optimizing the maintenance schedule for the grouped pumps in the refinery plant using the expected cost criterion and expected cost-variance criterion. This is characterized by the application of techniques to prolong equipment life, minimize downtimes, and enhance all aspects of reliability, availability and maintainability. The results showed that the cost and time of maintenance could optimize based on the rotating equipment, which could implement according to the preventive and corrective maintenance policy. The results analysis has revealed that applying optimization of maintenance schedule could help practitioners in decision-making to estimate the optimal cost and time, and reduce planning efforts in the future. Keywords: Pumps equipment, Maintenance policy, Cost and time of maintenance.

Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells

Recent research into Rh and Ce0.80Gd0.20O1.90-impregnated La0.20Sr0.25Ca0.45TiO3 fuel electrodes for solid oxide fuel cells has demonstrated the high-stability of these material sets to a variety of harsh operating conditions at small scales (1 cm2 active area button cells), as well as commercial scales (100 cm2 cells) in short stacks (5 cells) and full micro-combined heat and power systems (60 cells). In this work, the authors present a comprehensive evaluation of the ability of these novel titanate-based materials to function as fuel electrodes in solid oxide electrolysis cells (SOECs). Short-term and durability testing of button cell scale SOECs highlighted the limited stability of lanthanum strontium manganite-based air electrodes, under CO2 and steam electrolysis conditions, with lanthanum strontium cobaltite ferrite-based air electrodes offering improved degradation characteristics. Upscaling of this optimized cell chemistry to a 16 cm2 active area SOEC and testing under CO2, CO2/H2O and H2O electrolysis conditions demonstrated encouraging performance over a period of ∼600 h, with stable co-electrolysis performance at ∼−7.5 A at 1.47 V for the first 100 h.

Fault Intelligent Diagnosis for Distribution Box in Hot Rolling Based on Depthwise Separable Convolution and Bi-LSTM

The finishing mill is a critical link in the hot rolling process, influencing the final product’s quality, and even economic efficiency. The distribution box of the finishing mill plays a vital role in power transmission and distribution. However, harsh operating conditions can frequently lead to distribution box damage and even failure. To diagnose faults in the distribution box promptly, a fault diagnosis network model is constructed in this paper. This model combines depthwise separable convolution and Bi-LSTM. Depthwise separable convolution and Bi-LSTM can extract both spatial and temporal features from signals. This structure enables comprehensive feature extraction and fully utilizes signal information. To verify the diagnostic capability of the model, five types of data are collected and used: the pitting of tooth flank, flat-headed sleeve tooth crack, gear surface crack, gear tooth surface spalling, and normal conditions. The model achieves an accuracy of 97.46% and incorporates a lightweight design, which enhances computational efficiency. Furthermore, the model maintains approximately 90% accuracy under three noise conditions. Based on these results, the proposed model can effectively diagnose faults in the distribution box, and reduce downtime in engineering.

Enhancement of tribological performance of PTFE/aramid fabric liner under high-temperature and heavy-load through incorporation of microcapsule/CF multilayer composite structure

Liners suffer from low service life under high-temperature and heavy-load conditions, hindering their widespread use in aerospace applications. A novel strategy of incorporating polyaryl ether sulfone/polymethylphenlsiloxane (PES/PMPS) microcapsules and carbon fibers (CFs) into the polytetrafluoroethylene (PTFE)/aramid fabric liner was used. At the micro-scale level, the worn surface morphology and the transfer film morphology were analyzed to reveal the tribological mechanisms. At the nano-scale level, molecular dynamics simulation was used to analyze the formation mechanism of the transfer film. The results showed that the friction coefficient and wear rate of the liner with microcapsule/CF multilayer structure were reduced by 17 % and 24 %, respectively. The incorporation of microcapsule/CF multilayer structure can be effectively applied to enhance the tribological performance of liners in harsh operating conditions.

Enhancing durability of superhydrophobic surfaces via nanoparticle-induced bipolar interface effects and micro-nano composite structures: A femtosecond laser and chemical modification approach

Superhydrophobic coatings are vital in energy, aerospace, and chemical engineering, while their complex preparation and limited durability hinder widespread application. Therefore, inspired by the unique structures of hydrophobic cotton surfaces and mosquito eyes in nature, a durable aluminum alloy superhydrophobic surface is developed using a combination of femtosecond laser and chemical modification methods. Initially, porous microneedle micro-nanostructures are ablated on the surface of the aluminum alloy via femtosecond laser technology. Then, epoxy resin modified with γ-aminopropyl triethoxysilane (KH550) forms a covalently bonded intermediate layer. Finally, biphasic silicon dioxide (BP-SiO2) nanoparticles modified by hexadecyltrimethoxysilane (HDTMS) are used to construct the top hydrophobic layer. The covalent interface interactions between the aluminum alloy substrate and the intermediate layer, as well as between the intermediate layer and the top layer, significantly enhance the durability of the superhydrophobic surface. The prepared F-M@KH-EP/BP-SiO2 coating exhibits outstanding superhydrophobic properties, with a water contact angle (CA) as high as 168.56° and a sliding angle (SA) as low as 1.52° More encouragingly, the composite coating maintains its excellent water resistance even when subjected to harsh mechanical durability damage, including sandpaper wear, tape stripping tests, water drop and sand impact tests. Moreover, the prepared coatings maintain distinguished non-wettability in harsh operating conditions such as corrosive liquid environments, ultraviolet radiation, ultrasonic vibration, etc. Additionally, the coating demonstrates remarkable self-cleaning properties. Superhydrophobic surface durability is significantly enhanced by combining nanoparticle-induced bipolar interface effect and micro-nano structures. These findings provide theoretical reference for the design and application of durable superhydrophobic coatings.