Safe Operating Conditions Research Articles

Safe operating conditions of isoperibolic homogeneous semibatch reactions: Effect of mixing heat

The mixing heat in a semibatch reactor may lead to an increase or decrease of the reaction initial temperature, which has an impact on the safety of the reaction. In this paper, the effect of mixing heat on the safe operating conditions of isoperibolic homogeneous semibatch reactions was studied. Mass and energy balance models considering mixing heat were constructed. Based on the balance models, boundary diagrams and adiabatic temperature diagrams were compared under different mixing heat levels. The mixing heat and reaction heat of esterification reaction between propionic anhydride and sec-butanol were measured by EasyMax. According to the experimental results, the effect of mixing heat on the thermal runaway critical cooling temperature was investigated. The results indicated that the mixing heat had a significant effect on the thermal behavior state of the reaction. The critical criterion considering the mixing heat can more accurately predict the safe reaction operating conditions for the isoperibolic homogeneous semibatch reactions. This work provided helpful suggestions for predicting safe operating conditions of reactions at different mixing heat effect levels.

Macroporous vanadium dioxide–reduced graphene oxide microspheres: Cathode material with enhanced electrochemical kinetics for aqueous zinc-ion batteries

Aqueous zinc-ion batteries are being extensively investigated owing to their safe operating conditions. Therefore, the search for cathode materials with optimum composition and nanostructure that enable high zinc-ion storage performance is underway. This study introduces a procedure for the formation of vanadium dioxide-nanoflake-reduced graphene oxide composite (P-VO2@rGO) microspheres with open pores through spray pyrolysis. Spherical cathode materials are formed by spray pyrolysis through the addition of polystyrene nanobeads and graphene oxide nanosheets in the spray solution. This enabled the formation of porous and crumpled graphene oxide microspheres, wherein thin VO2 nanoflakes are anchored. As a cathode for zinc-ion batteries, P-VO2@rGO exhibits a high rate capability (159 mA h g−1; current density = 5.0 A g−1) and stable cycle performance for the 300 cycles at 1.0 A g−1. To discern the synergistic effect of the reduced graphene oxide (rGO) and 3D-porous structure with a small crystal size on the zinc-ion storage, control samples (VO2-rGO composite and porous VO2 microspheres) are synthesized and tested as cathodes for zinc-ion batteries. The synergistic effect of compositing rGO and introducing porous structure with small crystal size enables high reversible capacity and enhances electrochemical kinetics of the electrode.

Bifurcation Analysis of Active Electrical Distribution Networks Considering Load Tap Changers and Power Converter Capacity Limits

The aim of this article is to analyze the parameter stability and power transfer limits of active distribution networks with power converters and load tap changers by using bifurcation theory.First, the nonlinear model of a representative distribution grid with mixed loads and power converters is derived. Frequently neglected effects of converter capacity limits and transformers with load tap changers are considered, and for this purpose, static and dynamic saturations are modeled by using approximations based on smooth functions. In addition, a solution based on an antiwindup scheme is provided to model load tap changers without numerical convergence problems. These methods allow their integration to the model in a comprehensive way. Results show the impact of converter parameters and its limits on system stability as well as the impact of weak grid conditions. Moreover, they show that these effects can destabilize the system under, seemingly, safe operating conditions. The results indicate that reactive power support from converters can improve stability margins and the performed analysis can help in the design of the converter control parameters. Experimental results obtained from the laboratory environment comprising two distributed generators and a grid emulator are used for the validation of the contributions of this article.

Electric-Drive-Reconstructed Onboard Charger for Solar-Powered Electric Vehicles Incorporating Six-Phase Machine

In this article, a novel electric-drive-reconstructed onboard charger (EDROC) is proposed for the solar-powered electric vehicle that incorporates a six-phase machine drive. The power traction inverter and the machine are re-leveraged to implement charging operation, further minimizing the incremental mass accordingly. In particular, charging and driving operations can be simultaneously carried out via the vehicle-roof photovoltaic panels, significantly expanding EV mileage range. First, the operation scenario and the topology of the proposed EDROC are introduced. Next, the operational principle is analyzed, as well as the indispensable conditions for safe and stable operation are studied. Thereafter, control schemes are designed and elaborated in terms of the simultaneous driving and charging mode and the dc charging mode. To this end, a 2-kW laboratory prototype is conducted, and experimental results are presented to verify the steady-state and dynamic behavior of the proposed EDROC system under different operation modes.

D-S evidence based FMECA approach to assess potential risks in ballast water system (BWS) on-board tanker ship

Ballast water is essential for cargo ships since it stabilizes vessels at sea. Most ships are equipped with a ballast water system (BWS) to maintain safe operating conditions. This paper attempts to perform a risk assessment for the BWS on-board tanker ship as it poses a major threat to the operational safety of the ship, marine environment, and cargo. To achieve this purpose, the paper utilizes a robust methodology integrating D-S evidence (Dempster-Shafer) theory and FMECA (Failure mode effects and criticality analysis). In the methodology, while the D-S evidence theory introduces a proper mathematical framework to handle epistemic uncertainty in the assessment of risk parameters and to prioritize failure modes as intended, the FMECA is capable of evaluating system potential failures and their causes. Hence, the risk priority number (RPN) can be calculated to assess potential hazards and their consequences in BWS on-board ships. Besides its theoretical insight, the paper contributes to marine safety inspectors, safety researchers, and HSEQ (Health, Safety, Environment, and Quality) managers to identify potential hazards, effects, and consequences in case of BWS failures on-board tanker ships.

Generalized Method for Determining the Width of a Safe Maneuvering Area for Bulk Carriers at Waterway Bends

There are a number of empirical methods for determining the width of safe maneuvering areas for ships on waterways. These methods are relatively accurate for straight sections of waterways and less accurate for curves of the waterways. When designing waterways in detail or determining the conditions for their safe operation, more accurate methods (e.g., simulations) are used. However, such studies require relatively large expenditure involving the construction of simulation models of various vessels and water areas, and conducting a real-time simulation experiment with a sufficiently large number of maneuvers performed by highly qualified navigators (pilots, captains). This study deals with the problem of determining the width of safe maneuvering areas of ships on the bends of the waterway based on the results of simulation studies. A new empirical method was developed to determine the width of safe maneuvering areas of loaded bulk carriers passing through fairway bends under deteriorated hydro-meteorological conditions. The method was developed on the basis of a generalization of the results of many simulation experiments carried out at various stages of the Świnoujście–Szczecin fairway reconstruction and a determination of the safe operating conditions for ships passing through the fairway.

Global sensitivity analysis to identify influential model input on thermal risk parameters: To cottonseed oil epoxidation

Thermal runaway is still an important cause of accident in chemical industry. To evaluate the risk of such events, thermal risk assessment, which is a part of process safety, must be done. This assessment determines the safe operating conditions of a process by evaluating the thermal risk of an exothermic system. Nevertheless, based on thermal risk assessment, it is not possible to know which model inputs have the most influence on the thermal risk parameters. The knowledge of the most influential model inputs on thermal risk parameters is important to establish adequate safety barriers. Global sensitivity analysis was used to evaluate the influence of model inputs and their interaction on thermal risk parameters. It was performed on the exothermic system: epoxidation of cottonseed oil by performic acid in semibatch mode under isoperibolic conditions. The maximum reaction temperature and the time to reach this maximum reaction temperature were chosen as thermal risk parameters. We have also studied the influence of model inputs on the temperature rise. In the operating conditions of this study, it appeared that two parameters have the most influence on maximum reaction temperature and the temperature rise: the initial concentration of hydrogen peroxide and the jacket temperature, and one parameter for the time to reach this temperature: the jacket temperature.

Low-Cost Sensory Glove for Human–Robot Collaboration in Advanced Manufacturing Systems

Human–robot collaboration (HRC) enables humans and robots to coexist in the same working environment by performing production operations together. HRC systems are used in advanced manufacturing to improve the productivity and efficiency of a manufacturing process. The question is which HRC systems can ensure that humans can work with robots in a safe environment. This present study proposes a solution through the development of a low-cost sensory glove. This glove was developed using a number of hardware and software tools. The sensory glove analysed and computed the motion and orientation of a worker’s hand. This was carried out to operate the robot through commands and actions while under safe operating conditions. The sensory glove was built as a mechatronic device and was controlled by an algorithm that was designed and developed to compute the data and create a three-dimensional render of the glove as it moved. The image produced enabled the robot to recognize the worker’s hand when collaboration began. Tests were conducted to determine the accuracy, dynamic range and practicality of the system. The results showed that the sensory glove is an innovative low-cost solution for humans and robots to collaborate safely. The sensory glove was able to provide a safe working environment for humans and robots to collaborate on operations together.

Observation of gunpowder-like thermochemical responses of a thermal energy storage system based on KNO3/NaNO3/Graphite exposed to a heat transfer fluid

• Safe operation condition for latent-type thermal energy storage is sought. • Solar salts can explosively react with expanded graphite under moderate heating. • Heat transfer fluid for such phase change materials accelerates chemical reaction. • Gunpowder-like thermal runaway is observed in thermal energy storage system. An application of latent-type thermal energy storage (TES) system and its issues associated with the safe operation for TES composite materials (i.e., solar salts (KNO 3 /NaNO 3 ) and expanded graphite) are investigated. This work is aimed to present the compatibility of various compositions of TES materials with a heat transfer fluid (HTF) to provide a guideline for safe and reliable system usage. The thermochemical characteristics and chemical kinetic mechanism for HTF-diluted TES samples were measured using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) with additional numerical analysis for validation of the constructed reaction kinetics. Amongst the range of percent HTF dilutions, 20 wt% HTF dilution in comparison to no HTF dilution showed the strongest exothermic runaway reaction. For instance, with a decrease in the onset temperature, the time to runaway was shortened, while the change in the heat of reaction was not significant. The numerical simulations with chemical kinetics obtained using thermochemical analysis revealed that the reaction runway characteristics of HTF-diluted TES materials show a similar detonative behavior as of gunpowder. Moreover, the function of HTF in TES system appeared to be identical to that of sulfur in gunpower as its specific percent composition was responsible for accelerating an exothermic chemical reaction.

RESEARCH OF ELECTRIC POWER INDUSTRY MODELS AND METHODS OF ELECTRICITY QUALITY MEASUREMENTS

During the reconstruction of existing and construction of new energy facilities, mostly modern imported equipment is used, which is not certified in Ukraine due to inconsistencies in domestic standards. This creates difficulties in coordinating projects with government agencies regarding building codes and regulations, energy efficiency requirements, safety requirements, and so on. There are also no standards in Ukraine regarding the functioning of the energy market. Therefore, it is necessary to update the array of ND industry, for the implementation of which it is necessary to develop appropriate scientific and methodological principles for improving the system of these documents. The introduction of international standards as national standards of Ukraine will remove many controversial issues in the modernization of energy facilities, promote domestic energy equipment in the Western market, create conditions for parallel operation of Ukraine's energy system with European energy associations, improve the quality of energy. But updating the regulatory framework of the industry requires significant time and money, so it is necessary to properly organize this process in order to improve the technical and economic efficiency (EE) of energy in the shortest possible time with minimal costs. One of the methods of solving this problem is complex standardization (CS), the methodological foundations of which were laid in Soviet times, but are outdated due to changing economic conditions and basic criteria for assessing the efficiency of energy facilities, especially their impact on humans and the environment. Therefore, it is necessary to develop a new approach to the COP in the field of electricity in modern conditions, in particular, to develop a model of the COP, methods, classification of tasks and determine the priority of standardization in the field of electricity. Standardization in the electricity sector should cover all major areas of industry development and contribute to the creation of conditions for safe operation of electricity facilities, ensuring rational energy consumption, improving the technical level and environmental safety of energy facilities, ensuring reliable and efficient operation of Ukraine's integrated energy system. Therefore, the development of the COP model should be based on the structural model of the power industry, which corresponds to the real conditions of the industry. To ensure the cost-effectiveness of the COP, it is necessary to develop a new methodology for evaluating EE development and implementation of standards for energy equipment in market conditions, as well as methodological approaches to economic optimization of the sequence of implementation of standards. Thus, the development of scientific and methodological principles for improving the system of regulatory documents of the electric power industry of Ukraine is an urgent and important task, the solution of which will contribute to the effective updating of the regulatory framework of the industry.

A Multihull Boat’s Fatigue Analysis at Early Design Phase

Fatigue analysis and life cycle prediction of a naval craft or a commercial ship are one of the most critical phases of structural integrity calculations. Many structural failures have occurred due to insufficient structural design, production methods, and inappropriate operational environmental conditions. As a result of the deterioration of the structural integrity, the occurrence of both vital and economic losses becomes inevitable. This paper emphasises the importance of fatigue and life cycle analyses at the early design phase since the fatigue phenomena are generally considered in the late design stages. In this study, fatigue calculations and life predictions were carried out by the Palmgren–Miner method. The wave rosette, also called long-term wave directionality, was used as the wave spectrum approach. Based on wave loads and accelerations, an FE analysis was carried out using the Maestro Marine Altair Partner Alliance (APA) software. The undamaged life prediction of the vessel was calculated based on different sea states and vessel speeds. A specific scenario, which was prepared based on the International Code of Safety for High-Speed Craft, was also analysed to compare the fatigue life of the vessel with regards to safe operating conditions for passengers and crew. In this study, the effect of sea states, environmental conditions, and materials used on the fatigue behaviour of the vessel are discussed and analysed. As a result of this study, the shortest and the longest undamaged life spans based on the loading scenarios are put forth clearly. Analyses and calculations prove that loading scenario 5 is the most effective scenario in terms of the undamaged life span of the boat. On the contrary, loading scenario 1 gives the shortest service life. The main reason behind this phenomenon is the relation between the fatigue endurance limit and load cycles.

Experimental Investigation of Polymer-Induced Fouling of Heater Tubes in the First-Ever Polymer Flood on Alaska North Slope Part II

Summary A polymer flood pilot has been ongoing in the Schrader Bluff viscous oil reservoir at Milne Point on the Alaska North Slope. The results from the pilot are encouraging. However, a major concern of the operator is the influence of polymer on the production system after breakthrough, especially the fouling in heat exchangers. This work applies a multiexperimental approach to study the severity of polymer-induced fouling in both dynamic and static states of produced fluids to determine safe operating conditions. Dynamic scale loop (DSL) tests were conducted to study fouling due to polymer at different skin temperatures (165–350°F) in a dynamic state of fluid flow where the fluids’ flow mimics the residence time of fluids in the heat exchanger of the field pilot. Static deposit tests were also conducted at similar skin temperatures of 165–250°F using a novel experimental apparatus designed and built in-house. It was found that at higher skin temperatures of 250–350°F, tube blocking was observed in the DSL tests, whereas the tests at 165–200°F did not show any tube blocking, even in a more extended test period. The deposit test showed that the deposit rate generally increases with skin temperature, and the presence of polymer aggravates the fouling. The copper tube performs best when the skin temperatures are 165–200°F, while the stainless steel tube performs best at a skin temperature of 250°F. These experiments also manifested the influence of the cloudpoint of the solution as the deposit rate increased significantly when the skin temperature was higher than the solution cloudpoint. The study provides a source of practical guidance to the field operations.

Unveiling unique steric effect of threonine additive for highly reversible Zn anode

Aqueous Zn-ion batteries (ZIBs) exhibit a great potential for large scale energy storage applications due to their low cost and safe operating conditions. However, the dendritic growth of Zn caused by the random diffusion of Zn2+ ions on the Zn anode during operation shortens the cycle life of ZIBs. In this study, an ultra-trace amount of threonine (TH) was used as an electrolyte additive for the first time. Results showed that the TH molecules were adsorbed on the Zn anode surface. These molecules restricted the planar diffusion of Zn2+ ions through steric effects, which effectively inhibited the hydrogen evolution reaction and suppressed the dendritic growth of Zn. The assembled Zn//Zn symmetric cell with the TH additive showed stably cycling characteristics for over 580 h at 1 mA cm−2 with a capacity of 1 mAh cm−2, and the carbon cloth (CC)//Zn half-cell with the TH additive exhibited a high coulombic efficiency of 99.5%. Moreover, the Zn//CVO full cells with TH additive exhibited better capacity retention properties than the cell fabricated using the pure electrolyte. This work provides an encouraging path for development of low cost and efficient electrolyte additives for dendrite-free ZIBs.

Enviro-economic investigation of various flare gas recovery and utilization technologies in upstream and downstream of oil and gas industries

The flaring network is an inseparable part of the oil, gas, and petrochemical industries to provide safe and reliable operating conditions. Since flaring results in significant greenhouse gas emissions and economic loss, over the last decade, different processes have been developed to recover and utilize flare gas in upstream and downstream of oil and gas industries. According to the wide range of flare and associated gas specifications, all flare gas recovery and utilization technologies are not always feasible and economically justified. Since performing a detailed analysis on all available recovery processes is time-consuming, a guideline for an initial screening and crossing out unattractive economic options for a specific flare gas would be beneficial. In the current research, for seven flare gas recovery and utilization technologies (compression and reinjection to well, natural gas liquids, gas to liquids, methanol and dimethyl ether production, liquefied natural gas, and power generation using reciprocating internal combustion engine cycle) and sixteen flare and associated gas samples economic analysis has been carried out. The results indicate that power generation using the reciprocating internal combustion engines is economically justifiable for an extensive range of flare gas specifications. The calculation of CO2 emissions shows that by using flare gas recovery and utilization technologies, the CO2 emission can be reduced by 50–90% compared to the flare stack. According to the results obtained in this study, some guidelines are provided for an initial screening on the flare gas recovery and utilization technologies.

Investigating the mechanism of frost penetration under railway embankment and projecting frost depth for future expected climate: A case study

A common issue for railways constructed in cold regions is the development of localized frost heave on the surface of railway tracks during winter and track softening during the spring thaw. Both frost heave and thaw softening cause track geometry degradation and often require frequent maintenance and the reduction of train speeds to ensure safe operating conditions. This study investigated the mechanism of frost development within a railway embankment through field observations and numerical simulations. This paper uses the temperature measurements from an instrumented section of railway track in Ontario, Canada to calibrate a numerical model and then uses this model to quantify the effect of ambient temperature and the amount of snowfall on the frost penetration within railway foundations. The results show a widespread frost zone develops within the embankment that could last until spring. The sensitivity analysis conducted as part of this study shows ambient temperature has a stronger effect on frost penetration than snow on the ground. Moreover, this paper proposes a simplified methodology to combine numerical model results and data from climate models to project future frost depth at a given location. The application of this methodology at the study site of this project indicated the frost will penetrate less under future climate but still to sufficient depths to reach the frost-susceptible layers of subgrade.

Ammonia-hydrogen-air gas turbine cycle and control analyses

Blending ammonia with hydrogen has the potential of replacing conventional hydrocarbon fuels to reduce carbon emissions. However, the uncertainties of determining safe, stable, and efficient operating conditions remain a great challenge. Furthermore, although control technologies have been in the scope of interest for gas turbine manufacturers, those are not yet specialized for NH 3 –H 2 /air gas turbines. Therefore, this paper identifies the cycle performance of an NH 3 –H 2 /air gas turbine in comparison to a CH 4 /air gas turbine, thus highlighting the operating conditions in which the NH 3 –H 2 /air gas turbines show higher performance compared to the CH 4 /air gas turbines. The results have been obtained by developing a LabVIEW code which has also been utilized to serve as a control code for the NH 3 –H 2 /air and CH 4 /air gas turbines. The system identification stage of calibrating the controller has been achieved for both gas turbines by determining the system's sensitivities, thus providing an accurate calibration of the controlling parameters. • Higher NH3–H2/air gas turbines performance compared to CH4/air gas turbines. • System identification, cycle, and sensitivity analyses of NH3–H2/air gas turbines. • Developing and calibrating an NH3–H2/air gas turbines controller.

Analysis of Battery Thermal Management System for Electric Vehicles using 1-Tetradecanol Phase Change Material

In a world where great efforts are being made to reduce carbon emissions and pollution, electric vehicles are becoming more appealing. Vehicles based on internal combustion engines are slowly being phased out and electric or hybrid vehicles are replacing them. Batteries being the primary power source of these vehicles, an effective battery thermal management system is required to ensure safe operation conditions and durability in all environments. The application of 1-Tetradecanol as a Phase Change Material (PCM) in a Battery Thermal Management System (BTMS) is studied, for its use in an electric vehicle that uses Lithium Iron Phosphate (LiFePO4) battery. In the present work, a computational model is developed using a professional modelling software, ANSYS Fluent to investigate the thermal performance of 1-Tetradecanol PCM during its melting process within a cylindrical enclosure. The thermal behaviour of the system under the influence of proposed BTMS is studied. However, pure PCM based passive thermal management systems are not perfect due to their inherent low conductivity, which may be improved by incorporating conductivity enhancing materials. It was evident from the results that, it has the potential to be a better alternative to conventional battery thermal management systems and can be a lightweight and cost effective PCM passive thermal management system to limit the temperature of EV batteries to acceptable operating ranges.

Onboard optimization of multi-arc trajectories with constraints on duration of arcs

Autonomous operation of rocket-powered vehicles is a promising technique that could significantly improve the adaptiveness of rocket-powered vehicles. However, to remedy in-flight engine failures and allow mission changes, the autonomous operation requires an onboard method to optimize the powered trajectories. While onboard methods to optimize the powered trajectories have been proposed before, none of them considered the constraints on duration of arcs in multi-arc trajectory optimization problems. The constraints on the duration of burn arcs and coast arcs often arise from the safe operating conditions of rocket engines, and violating these constraints will likely result in physically-infeasible trajectories. Determining the optimal duration of each arc while satisfying the constraints is a challenging problem for onboard trajectory optimization methods. In this paper, an onboard method to optimize multi-arc trajectories is proposed that is capable of enforcing the constraints on the duration of burn arcs and coast arcs. The proposed method employs a hybrid regularization approach to facilitate the convergence of the duration of arcs. Quadratic penalty terms and fixed-radius trust-region terms are simultaneously used to limit the change of duration of arcs between iterations. The two terms complement each other, contributing to the efficiency of the hybrid regularization approach. Moreover, we propose an optimality-based stopping criterion that certifies the optimality of optimized duration of arcs and helps reduce unnecessary iterations. Numerical results on an onboard computational platform are provided to validate the efficiency of the proposed method.

Safe Operating Conditions of Isoperibolic Homogeneous Semibatch Reactions: Effect of Mixing Heat

Safe Operating Conditions of Isoperibolic Homogeneous Semibatch Reactions: Effect of Mixing Heat

Analytical and experimental investigation of roll stability of a truck towing a special purpose trailer with no suspension

There are an increasing number of systems available to increase roll stability; however some are not present on all vehicles. Most recent research is focused on ways to improve roll stability, but research into the roll stability of existing vehicles is also important in determining safe operating conditions. This study investigates the roll stability of three vehicles towing a special-purpose trailer currently in use that has no brakes or suspension. Multibody dynamics models of the vehicles were built to simulate vehicle performance on high-speed turns and lane changes. Model validation was performed by comparing results between the simulation and physical testing. Roll stability was assessed by comparing static roll threshold (SRT) and load transfer ratio (LTR) values. All of the vehicles were shown to meet performance standards on a smooth surface, but introduction of surface roughness significantly decreased the roll stability of the trailer due to the lack of suspension.