Expected Operating Conditions Research Articles

Selected issues of hydropneumatic suspension design for a high-speed tracked vehicle.

The effective operation of high-speed tracked vehicles in a combat vehicle configuration depends primarily on the correct identification of the expected operating conditions, already in the design or modernisation phase. This applies to both terrain, meteorological and climatic conditions. This approach considers the most unfavourable driving conditions and the level of dynamic loads acting on the vehicle hull, crew and equipment when making calculations. The dominant source of dynamic loads is movement at high speed on unpaved roads, off-road and when overcoming natural and artificial terrain obstacles of a predetermined or random nature. An important system responsible for the safety and reliability of this type of vehicle is the suspension. An appropriate design of the suspension parameters allows to reduce the negative dynamic loads (research hypothesis). The aim of the research was to develop a preliminary project of an initial suspension element – a hydropneumatic spring for a high-speed tracked vehicle - that allows minimising dynamic loads. The study used both theoretical and empirical research methods, including analysis, synthesis, deduction, induction, comparison and inference. The paper presents selected issues from the suspension design process for a high-speed tracked vehicle equipped with a hydropneumatic suspension. The problem was solved in three stages. In the first stage, the design of the hydropneumatic suspension unit, placed in the control arm, was made and the basic parameters were selected. In the second, the spring characteristic of the hydropneumatic unit was determined on the example of a hypothetical vehicle with assumed tactical and technical parameters. In the third stage, the strength of the control arm structure, under the heaviest load conditions, was checked using the Finite Element Method (FEM). The results obtained showed that the advantages of the hydropneumatic suspension, such as: progressive spring characteristics, improved vibration damping, possibility of introducing a semi-active or active suspension system, modularity of the structure and ease of maintenance and repair, make it more and more widely used in modern high-speed tracked vehicles.

Safety and Resilience Bayesian Belief Network (SR-BBN) for ATM

This study delves into the realm of Air Traffic Management (ATM) and its criticality in ensuring the safety and resilience of aviation systems. Traditionally, safety has been approached reactively (Safety I), but with the complexities of socio-technical systems like ATM, a shift towards proactive measures is essential. This research explores Resilience Engineering (RE) and Safety II, emphasizing learning from a system’s adaptability in everyday situations. ATM, a multifaceted system, relies on technology, organization, and human interactions, striving to maintain equilibrium among these pillars for safe and efficient operations. Any changes to these elements can disrupt this balance, necessitating a systemic perspective. Safety in ATM depends on resource availability, timeliness, and coordination among organizations and humans, while resilient performance extends safety beyond the expected operating conditions. To unify safety and resilience, this study introduces the Safety Resilience-Bayesian Network (SR-BBN) model. This model integrates data-driven and knowledge-based approaches, categorizing variables into separations, external factors, nominal conditions, and Air Traffic Controller (ATCO) strategies. The SR-BBN model aids in predicting safety outcomes and identifies influential variables.

Wind turbine main bearing rating lives as determined by IEC 61400‐1 and ISO 281: A critical review and exploratory case study

AbstractThis paper studies the rating lives of wind turbine main bearings, as determined by the IEC 61400‐1 and ISO 281 standards. A critical review of relevant bearing life theory and turbine design requirements is provided, including discussion on possible shortcomings such as the existence (or not) of the bearing fatigue load limit and the validity of assuming linear damage accumulation. A detailed exploratory case study is then undertaken to determine rating lives for two models of main bearing in a 1.5 MW wind turbine. Rating life assessment is carried out under different conditions, including various combinations of main bearing temperature, wind field characteristics, lubricant viscosity, and contamination levels. Rating lives are found to be sufficiently above the desired 20‐year design life for both bearing models under expected operating conditions. For the larger bearing, operational loads are shown to be below or close to the bearing fatigue load limit a vast majority of the time. Key sensitivities for rating life values are temperature and contamination. Overall, the results of this study suggest that an ISO 281 rating life assessment does not account for reported rates of main bearing failures in 1 to 3 MW wind turbines. It is recommended that a similar analysis be undertaken for ISO/TS 16281 rating lives, along with further efforts to identify principal root causes of main bearing failures in future work, possibly leading to a new application standard specific to this component. It is also recommended that the impacts of partial wake impingement on main bearing rating lives are investigated.

Thermal resistance of steels with increased strength properties for pressure vessels of advanced VVER reactors of various designs

The paper considers the results of structural studies and mechanical tests after a long-term thermal exposure of laboratory heats of the metallurgically improved 15Kh2NMFA steel and steel with an increased content of nickel considered as materials for the pressure vessels of advanced VVER-type reactors of various designs. It has been shown that, both for the improved 15Kh2NMFA steel and the high-nickel steel, there are no signs of grain boundary embrittlement after an segregation provoking embrittlement heat treatment. This is explained by the extremely low grain boundary segregation of phosphorus in the initial state caused by a high degree of the structure dispersity as well as by rather a low content of impurities. Besides, no changes have been found in the yield strength value for the improved 15Kh2NMFA steel, which agrees with the structure investigation results. For the high-nickel steel, a tendency towards a minor yield strength decrease by 5 to 10% and a regular reduction of the critical brittleness temperature has been revealed. A decrease in the mechanical properties has been caused by a relatively low temperature of tempering for the high-nickel steel and, accordingly, by the potential occurrence of the structure recovery during long-term thermal exposure, as evidenced by the results of an X-ray diffraction analysis. Despite the structure recovery in the high-nickel steel under the long-term thermal exposure, the main strengthening carbide phases remain stable. Due to this, the yield strength value remains at a relatively high level that exceeds the values for the modern VVER-type vessel steels, even in the case of a thermal exposure much in excess of the expected operating conditions for advanced VVER reactors. The observed decrease of critical brittleness temperature during the long-term thermal exposure contributes to an increase in the steel resistance to brittle fracture.

Design and Analysis of Self-Energising Unmanned Underwater Vehicle (UUV)

This research focuses on the development of a self-energizing underwater vehicle that utilizes wave energy to power its circuit. The objective of the research work is to demonstrate the feasibility of harnessing renewable energy sources in an underwater environment and showcase the potential for sustainable power generation. To ensure the structural integrity of the vehicle under water, rigorous simulation analysis has been conducted using ANSYS software. The hull design has undergone thorough scrutiny to determine its ability to withstand water pressure at depths of up to 5 meters. The simulation results confirm that the submarine's hull design is robust and capable of withstanding the expected operating conditions. This study holds great significance in the field of marine engineering as it explores alternative energy sources for underwater applications. By harnessing wave energy, this work contributes to the development of sustainable technologies that can potentially revolutionize underwater operations. The use of renewable energy sources minimizes environmental impact and reduces reliance on traditional power sources. Throughout this research, challenges were encountered, including optimizing the turbine system efficiency, ensuring reliable power transfer, and maintaining the structural integrity of the submarine. These challenges were addressed through careful design considerations and iterative improvements. The knowledge gained from this study can be applied to various underwater applications such as marine exploration, environmental monitoring, and data collection. Future research and development should focus on enhancing the turbine design, integrating advanced power management systems, and conducting field tests to validate the system's performance in real-world-scenarios.

Probabilistic surrogate-based optimization of ship hull-propulsor design with bi-level infill sampling technique

This work develops a new multi-level hull-propulsor optimization tool, systematically considering the full range of expected operating conditions. Different solvers with variable fidelities are used to evaluate hydrodynamic objective functions and constraints. The bi-fidelity surrogate model is applied to integrate the accuracy advantage of a medium-fidelity solver with the efficiency advantage of a low-fidelity solver. A bi-level technique of infill sampling integrated with a new version of multi-objective evolutionary algorithms is presented to enhance the effectiveness of the surrogate models. A ship velocity- and sea state-based joint probability density function is employed to take into account the real lifetime operational space. The well-known S175 containership, KP505 propeller and a MAN B&W marine engine are utilized as the initial hull-propulsor model. The final results show that the optimization framework is able to achieve some optimum hull-propulsor designs from the lifetime fuel consumption and energy efficiency design index points of view and to reduce the overall lifetime ownership cost significantly.

Optimization of 3×3 inch NaI(Tl) detector related to energy, distance and bias voltage

There are different types of radiation detectors (gas-filled, semiconductor, scintillator etc.) and various working principles (ionization, electron-hole pair production, excitation) used in radiation detection. It is important that any detector is selected according to its intended use and that the detector is operated under appropriate conditions. NaI(Tl) scintillation detectors are widely used in nuclear spectroscopic studies due to their known advantages. Prior to carrying out such studies, it is first necessary to know the response function of the detector against radiation under the expected operating conditions and to perform the appropriate calibrations. It is important that certain factors are optimized, such as the experimental setup (source-to-detector position, shielding, source activity etc.), gain, bias voltage, and shaping time, which can each significantly affect the response function. In addition, in computational studies based on experimentation, optimization is gain more significant since it is assumed that such experimental studies are carried out under optimum conditions. In this study, in order to determine the most suitable operating conditions for a 3 × 3 inch NaI(Tl) detector; a coaxial sample holder was manufactured to enable different source-to-detector distances (5–15 cm) to be tested, and spectra were then obtained using different bias voltages (750–850 V) and sources with different energies in the range of 81–1332 keV. Through the use of efficiency values obtained for each condition, line and 3D surface plots were drawn and the relations between efficiency and distance, energy and bias voltage examined. The results showed that the efficiency value had an exponentially decreasing characteristic that was dependent on the energy and source-detector distance, and had the highest value at a bias voltage of around 800 V.

Latest results of Longevity studies on the present CMS RPC system for HL-LHC phase

The present Compact Muon Solenoid Resistive Plate Chambers system has been worked efficiently during Run I and Run II of data taking period (Shah et al., 2020) [1]. In the coming years of operation with the High Luminosity LHC (HL-LHC), the expected rate and integrated charge are expected to be about 600 Hz/cm2 and 840 mC/cm2, respectively (including a safety factor of three). Therefore, the HL-LHC phase will be a challenge for the RPC system since the expected operating conditions are much harsher than those for which the detectors have been designed, and could introduce non-recoverable aging effects which can alter the detector properties. A longevity test has been started at the CERN Gamma Irradiation Facility to estimate the impact of HL-LHC conditions on the RPC detector performance in order to determine whether the RPC system will survive the harsher background conditions expected at HL-LHC. The latest results of the irradiation test will be presented.

Models of the electromechanical system of the floating wave power station

The structure of the electromechanical system (EMS) of a floating wave power plant (FWPP) is developed, which, in addition to generating electricity, protects coastal structures or individual objects on the high seas. The mechanisms of formation of moments on the FWPP shaft are analyzed. Problems are formulated to determine the relationship between the capacity of an electric accumulator and the volume of the water basin of an energy concentrator. Mathematical and simulation models of EMS components are developed. The power ratios of the EMS components and the rated power of the FWPP under the expected operating conditions are determined. Keywords: model, energy converter, electromechanical system. kryukov@nntu.ru

Preliminary assessment of the possibility to use large-diameter pipes of Х52 steel for transportation of pure gaseous hydrogen under pressure

To assess resistance to hydrogen embrittlement caused by the presence of hydrogen in the transported product, and, accordingly, suitability of pipes for hydrogen transport, the base metal of large-diameter pipes of X52 strength class manufactured by JSC “ChelPipe” (part of the PJSC “TMK” group of companies) was studied. The work included the study of pure gaseous hydrogen effect under pressure up to 10 MPa on change in mechanical characteristics of the base metal of large-diameter pipes (LDP) during preliminary hydrogen charging for various time periods in a stationary autoclave under pressure, and during simultaneous loading with a slow strain rate (SSRT) under expected operating conditions. Results of the X52 LDP metal study show that there is no significant impact on the effect of gaseous hydrogen under pressure for up to 144 hours on mechanical characteristics of the base metal determined by static uniaxial tension (decrease in ductile characteristics does not exceed 9 %). During SSRT at a rate of not more than 1·10–6 s–1 in pure gaseous hydrogen environment under a pressure of 10 MPa, the change in strength and ductile characteristics does not exceed 13 % in comparison with reference tests in nitrogen environment under the same pressure. The results obtained allow us to consider that the base metal of low-alloy pipe steel with ferrite-perlite microstructure of X52 strength class is sufficiently resistant to hydrogen embrittlement. Final confirmation of the possibility to use LDP made from steel under study will be the results of further qualification tests, including the study of the weld metal and heat-affected zone properties.

Numerical simulation of deformations of a specimen of a composite helicopter blade as part of a resonant vibration set-up

To determine the fatigue life of the tail rotor blade of a helicopter made of polymer composite materials (CM), a method of fatigue testing of the specimens of the blade with accompanied numerical modeling of the deformed state has been developed. The tests are carried out on a resonant vibration set-up, with simultaneous reproduction of a forcing harmonic transverse force and a constant longitudinal tensile force. The tests are carried out by a vibration loading mode equivalent in fatigue damage, which includes one level of variable load in the thrust plane and in the plane of rotation. The equivalent mode is formed based on the variable loading spectrum of the blade, which is obtained from the results of flight measurements of the loads on the tail rotor, as well as the repeatability of the expected operating conditions of the helicopter. The tests are accompanied by computational and experimental studies, which include finite element calculation of the stress state and modal analysis of the standard blade and the test specimen, as well as the strain measuring of the structure. According to the results of the research, the vibration loading modes are corrected.

Study Explores Cost-Effective, Ecologically Sound Fluid-Disposal Methods

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202917, “Cost-Effective and Ecologically Sound Fluid Disposal During Well Cleanup and Post-Fracturing Flowback Operations,” by Yakov Shumakov, Florian Hollaender, SPE, and Bertrand Theuveny, SPE, Schlumberger. The paper has not been peer reviewed. The complete paper summarizes the results and lessons learned from the application of different methods used for fluid disposal in a wide range of well-testing operations around the globe. These were used to determine that economical and environmentally responsible solutions exist for fluid disposal during these operations. The complete paper also details a field-proven and cost-effective fluid-storage solution using a shuttle tanker during well-test and flowback operations offshore. Fluid-Disposal System Ecologically sound and safe fluid disposal during well testing and cleanup is one of the primary objectives, from an operational standpoint, of any temporary surface well-test package. Each fluid-disposal system is designed and sized for each operation according to the expected operating conditions. Typical fluid-disposal systems include the following. Water-Filtration System. In this system, produced water is first separated from hydrocarbons at the surface by using the well-test separator included in the temporary surface package; then, it is treated to remove as much oil as possible before discharge overboard. Even after effective treatment, however, produced water still contains traces of oil at parts-per-million levels. Overboard discharge of any kind is controlled strictly by environmental regulators and legislation. The primary pollutants of concern are hydrocarbons and grease; therefore, most treatment technology for water produced offshore is geared toward removing these contaminants. Mobile water-treatment systems are ideal for fast-response or urgent situations, as well as supplemental or temporary operations such as completions, workovers, or well testing. They are often used to assist during plant startup and maintenance outages when the water-treatment system is unavailable or cannot meet water-production requirements. Temporary Fluid Storage. Provisional storage of produced hydrocarbons has been used successfully in the past and is still considered an optimal solution for operations with a relatively small volume of liquid hydrocarbons produced. In offshore operations, one important factor beyond the space on the deck of offshore rigs is the limit on the volume of live crude that can be stored permanently on the rig. The limitation in recoverable liquid volume applies a significant constraint on the duration of the test; thus, this disposal technique is applicable mainly on gas wells and in environmentally sensitive areas.

СОВЕРШЕНСТВОВАНИЕ МЕТОДИКИ ПРОГНОЗИРОВАНИЯ РАСПРЕДЕЛЕНИЯ РЕСУРСА МАШИН И ИХ ЭЛЕМЕНТОВ

The structural and technological modernization of machines as a whole, as an integral part of maintenance in its modern sense, acquires a more rigorous scientific basis and ultimately contributes to a significant improvement in the quality indicators of machines. It is this approach to solving the problems of increasing the life of machines, based on a deep analysis of the results of scientific research, operation and repair experience, that will allow us to achieve positive results. During repair, it is impossible to automatically achieve the same high degree of accuracy of assembly of aggregates and machines as in the process of mass production of new samples, and, consequently, in these cases, manufacturing errors of assembly can have a more noticeable effect on reducing the life of aggregates and machines. An objective assessment of such an impact, of course, is possible only on the basis of the results of special studies to establish the dependence of the service life of parts on certain technological factors. Variants of structural reliability schemes have been compiled depending on the ranks of repair costs, based on the assessment of the probability of the appearance of the limiting condition of machines by the levels of maintainability of its assembly units. The probabilistic relationship obtained in this way will be maintained throughout the entire period of operation of the machine until its overhaul, provided that during this period the level of maintainability of its components remains unchanged. On the basis of structural schemes and analysis of the background of production and operation, the requirements for the resource indicators of assembly units are determined. The analysis of the expected operating conditions and loading modes of the machine, as well as taking into account the technological factors of its manufacture (repair), allows you to establish the resource distributions of the machine of the first major repair and the numerical value of the coefficient of variation of this distribution. An expression was obtained for restoring the probability distribution of providing a machine resource, calculations using which showed that the distribution function restored according to the structural scheme has parameters corresponding to the pre-selected distribution of the machine resource.

Stability Analysis of Microgrid Islanding Transients Based on Interconnected Dissipative Subsystems

To ensure successful islanding of microgrids after a fault has occurred, the transient stability should be analyzed under a set of expected operating conditions during the design and operation of microgrids. Transient stability analysis is conventionally performed with time-domain analysis which is computationally expensive and does not quantify the stability margin. Energy-based methodologies can determine the stability margin, however existing methodologies require significant simplifications to be applied to the microgrid model. The energy-based stability analysis methodology proposed in this paper enables the analysis of high-dimension nonlinear microgrid systems and quantification of the stability margin within reasonable time. The performance of the methodology is validated by analyzing a case study microgrid and comparing the results to time-domain analysis and to a state-of-the-art methodology proposed in the literature. The results indicate that the proposed methodology has a significantly lower computational burden and similar accuracy compared to existing energy-based methodologies. The methodology is able to improve the probability of stable islanding of the case study microgrid from 74% up to 94% when only optimizing the design, and up to 100% when optimizing design and control actions.

A neuro-fuzzy approach for tracking maximum power point of photovoltaic solar system

This work presents a hybrid soft-computing methodology approach for intelligent maximum power point tracking (MPPT) techniques of a photovoltaic (PV) system under any expected operating conditions using artificial neural network-fuzzy (neuro-fuzzy). The proposed technique predicts the calculation of the duty cycle ensuring optimal power transfer between the PV generator and the load. The neuro-fuzzy hybrid method combines artificial neural network (ANN) to direct the controller to the region where the MPP is located with its reference voltage estimator and its block of neural order. After that, the fuzzy logic controller (FLC) with rule inference begins to establish the photovoltaic solar system at the MPP. The obtained simulation results using MATLAB/simulink software for the proposed approach compared to ANN and the perturb and observe (P&O), proved that neuro-fuzzy approach fulfilled to extract the optimum power with pertinence, efficiency and precision

Design and experimental validation of a high level electropneumatic source

The study and characterization of non-linear phenomena in silencers and microperforated panels under high sound pressure level and mean flow require a dedicated experimental bench with adequate acoustic sources. For this purpose, electropneumatic sources are excellent candidates to reach the expected operating conditions in the laboratory. The challenge is to design a source that can generate a high tonal sound level (> 160 dB SPL) under a significant mean flow (M > 0.1) with a low harmonic distortion. The objective is to focus on mastering the design process of such a tonal source based on an analytical modeling of the physical phenomenon of tonal sound generation and flow as a function of geometrical and pneumatic supply parameters. Based on this validated analytical modeling, a new original source has been developed with the objective of generating a pure harmonic sound in the frequency range [100; 800] Hz, that can reach 180 dB in an infinite duct, combined with a flow up to Mach 0.3. For this purpose, a flow chopper system with a digitally optimized pattern has been specifically developed to minimize harmonic distortion. Considering the need to experimentally evaluate the rate of harmonic distortion with a high degree of accuracy, a complex envelope analysis by Vold-Kalman was implemented in post-processing. Finally, an experimental test campaign was set up on a dedicated bench to test with an open ended duct, for different supply pressures going from 2.07 105 to 3.45 105 Pa, the performances of the new acoustic source. The results of this test campaign show that the device can generate a tonal sound level with a distortion of less than 40 % for the second order and less than 20 % for the higher orders, with a sound pressure level that can reach 186 dB at the resonances in presence of an average flow reaching M = 0.24. These observations are consistent with the predictions of both analytical and numerical models.

An Innovative Tunable Rule-Based Strategy for the Predictive Management of Hybrid Microgrids

This work proposes a methodology for the optimal training of rule-based management strategies, to be directly implemented in the industrial controller of hybrid off-grid microgrids. The parameters defining the control rules are optimally tuned resorting to different evolutionary algorithms, based on the expected operating conditions. The performance of the resulting management heuristics is compared with conventional approaches to optimal scheduling, including Mixed Integer Linear Programming (MILP) optimization, direct evolutionary scheduling optimization, and traditional non-trained heuristics. Results show how the trained heuristics achieve a performance very close to the global optimum found by the MILP solution, outperforming the other methods, and providing a single-layer commitment and dispatch algorithm which is easily deployable in the microgrid controller.

Microstructure and Properties of TiAl-Based Alloys Melted in Graphite Crucible

This paper presents the chemical and phase composition, microstructure, and selected properties both at room temperature and at the temperature corresponding to the expected operating conditions of three successive generations of TiAl-based alloys (Ti-47Al-2W-0.5Si, Ti-45Al-8Nb-0.5(B,C), and Ti-45Al-5Nb-2Cr-1Mo-0.5(B,C)-0.2Si) melted in a vacuum induction furnace with high-density isostatic pressed graphite crucibles. The obtained results of mechanical and physical properties of the produced alloys were compared to the properties of reference alloys with similar chemical composition and melted in a cold copper crucible furnace. The effect of increased carbon content in the produced alloys due to the degradation of the graphite crucible during melting is higher strength properties, lower plastic properties, higher coefficient of thermal expansion, and improved creep resistance. It was shown that the proposed technology could be successfully used in the production of different generation TiAl-based intermetallic alloys.

Design of the new supporting structure for the passive stabilizing shell assembly of RFX-mod2

An upgrade of RFX-­mod toroidal machine assembly is under development, aimed at widening the explored operational scenarios both in RFP and Tokamak configuration. The main design driver for this machine upgrade, named RFX-mod2, is the enhancement of the ‘shell-plasma proximity’, which is expected to provide a significant improvement in the plasma magnetic confinement. In order to achieve this goal, the existing Passive Stabilizing Shell will be adapted in order to be enclosed in the new vacuum vessel. This reconfiguration of the internal components of the experiment requires the design of a new structure aimed at supporting both the shell and the plasma facing components. The paper describes the design aspects of the shell assembly, with particular focus on the thermo-mechanical FEM analyses performed to verify the design of the components at the expected operating conditions.

A Generic Power Converter Sizing Framework for Series-Connected DC Offshore Wind Farms

Wind farms featuring a series-connected dc collection system have been shown to offer advantages in terms of total conversion efficiency and amount of offshore-deployed equipment. To ensure proper exploitation of these benefits, it is necessary to determine the ratings of wind turbine converters. These ratings must be sufficient to cover the expected operating conditions over the life of the wind farm, without unnecessarily oversizing the equipment. As shown in this article, the variable string current results in an interdependence of operating points among wind turbines that has to be considered for sizing these converters. This article proposes a generic sizing framework for such single-string, series-connected dc wind farms. This framework is applied to three wind farm configurations featuring differential power processing, voltage-source converters, and diode-bridge rectifiers and buck converters. Finally, a case study for a 450 MW offshore wind farm demonstrates the implementation of this sizing methodology and quantifies the design tradeoffs between converter ratings and energy production enabled from those converters. In two of the studied wind farm configurations, significant rating reductions are achievable while still avoiding energy curtailment for >99.7% of the energy production of an equivalent ac wind farm.