Actual Operating Conditions Research Articles

Oxygen corrosion of reboiler tube served in production of dilution steam from heat exchanger of petrochemical refinery

This paper reports the oxygen corrosion of heat exchanger tubes serviced in dilute steam generation system. The floating head heat exchanger employed in a petrochemical industry underwent remnant corrosion failures particularly at lower passes of tube bundle. Initially remote field eddy current inspection technique was employed for tube bundle conditional assessment and further, root cause of degradation of tube had been analyzed. Comprehensive experimental techniques including visual examination, tube chemistry analysis, external tube surface morphological analysis, elemental mapping, scanning electron microscopy, light microscopy and x-ray diffraction studies were employed. The tube surface at the degraded position with its cross sectional examination was rigorously evaluated as well. Moreover, actual steam parameters such as pH, conductivity and iron & chloride concentration have been monitored in the petrochemical facility. The detailed analysis concluded that dissolved oxygen in boiler feed water (BFW) was the root cause for corrosion failure. Several other foreign elements were detected and source of each element was discussed in the context of actual heat exchanger operating conditions. Simulated conditions of BFW service have electrochemically been evaluated in two different dissolved oxygen concentrations at 7.5 ppm and 12.7 ppm, respectively. Even small increase of dissolved oxygen in BFW could lead to promotion of oxygen reduction reaction. Theoretically SA179 tubes operated at pH of 9.75 could lead to formation of bicarbonate and it could protect the tube in absence of dissolved oxygen as evaluated by Molecular Dynamics simulation. However, according to obtained results, tube has been degraded due to presence of dissolved oxygen in BFW. Various contributing factors such as external paint/coat removal, absence of de-aerator system in BFW treatment and improper corrosion inhibitor programme were discussed. Several practical countermeasures have been suggested to mitigate oxygen corrosion failure in petrochemical refineries.

An UAV system for visual inspection and wall thickness measurements in ship surveys

This article presents the development of a UAV system designed to perform visual inspections and thickness measurements in ships’ cargo tanks. That includes the conception and evolution of the different components and subsystems of this UAV system and several tests, including some carried out in actual operating conditions. It also presents a near-wall positioning and propulsion system designed and developed to improve stability and avoid collisions. The paper also describes an articulated arm designed around an EMAT probe for wall thickness measurement. The measurement chain developed for this purpose includes all the electronics and computing necessary to send data in real-time to a ground station. Flying near walls poses challenges that compromises accuracy when approaching each measurement target points. Therefore, the wall approach and departure flight maneuvers are fully automatic. That facilitates and speeds up the inspection task that may require measurements on thousands of locations specified by the surveyor. The proposed UAV system aims to automate and improve the long and expensive surveys and inspections in the marine industry by reducing their time and costs.

Experimental study on the influence of the Buoyancy number on heat transfer in a pin-fins channel under rotational conditions

The trailing edge of turbine blades poses a significant challenge for research in internal cooling technology. In previously published studies on heat transfer coefficient (HTC), the limitations of experimental testing techniques have hindered the ability to scale up the rotational radius ratio in a similar manner, resulting in significantly lower Buoyancy number (Buo) values tested compared to the actual operating conditions of turbine blades, leading to biased HTC results.This article delves into experimental studies to explore the HTC of a pin-fin channel. The experimental testing encompassed a broad spectrum of conditions, including varying inlet Reynolds numbers ranging from 5000 to 70,000, rotation numbers (Ro) from 0 to 1.0, temperature ratio from 0.04 to 0.22, rotational radius ratio (r/D) from 20 to 52.33, and Buo from 0 to 2.55. For the same Buo, there is a significant difference in HTC, with the high Ro and low TR scenario demonstrating a distinct advantage in HTC compared to the low Ro and high TR condition. Furthermore, heat transfer enhancement was observed at approximately 30 % of the dimensionless positions. Therefore, to achieve more accurate HTC results, it is necessary to precisely match the values of Re, Ro, Buo, TR, and r/D.

Development of a DNN model using calibrated simulation for the optimal control of HVAC systems

Acquiring actual data for developing data-based prediction models for the optimization of control setpoints (hereinafter referred to as optimal control (OC)) in heating, ventilation, and air conditioning (HVAC) systems is challenging, especially when changing control setpoints while considering all possible boundary conditions. Thus, considering the scalability of OC, it is a promising solution to generate sufficient learning data according to the control settings using a highly accurate simulation model, build a source model, and expand the learning model based on the actual data of the target system. This is the first study to improve the scalability of OC aiming to develop a deep neural network (DNN) model to predict the power consumption of a heat source system. First, this study will construct a calibrated heat source system simulation model and then use the generated learning data to train a DNN model. The actual operation conditions of the target building and heating system located in Vietnam were analyzed using operation data. A physics-based simulation model of the target heat source system was developed and calibrated using actual operation data to improve accuracy. By using the calibrated simulation, sufficient learning data was generated for all control settings allowing for the development of a learning model based on DNN that predicted the power consumption of the heat source system. In addition, a highly accurate prediction model through hyperparameter optimization was secured.

Comparative Study of Simulation of Temperature Rise in Ring Main Unit.

The Ring Main Unit (RMU) is a critical device in power distribution systems used for connecting and distributing electricity. However, due to its compact internal structure and high current load, heat dissipation issues are particularly prominent. To address this problem, this study innovatively proposes a simplified RMU model, employing finite element simulation methods to accurately solve for the ohmic losses of conductors under actual operating conditions and obtain ohmic loss data for various components. This is the first in-depth investigation of the RMU's temperature rise problem using such a comprehensive approach. Subsequently, the temperature field was solved using two different temperature field analysis modules, with a detailed comparison and analysis of the simulation results to identify similarities, differences, and trends in temperature distribution. The results indicate that the temperature field solution model, which considers convective heat transfer, is more accurate and aligns with actual operating conditions. This research provides an innovative approach and practical solutions for the design and optimization of RMUs. Future research can further explore multiphysics coupling analysis methods to address structural design and mandatory validation issues for high and ultra-high voltage RMUs and other electrical equipment, thereby providing important insights for engineering design.

Reviewing experimental and theoretical efforts and key findings regarding hydrodynamic journal bearing geometry

Abstract Journal bearing operation particularly in regard to marine applications is significantly affected by the performance of the most critical operational factors. Specifically, the lubricating oil film within journal bearing is so often than not subject to hazardous deterioration and ultimate failure in real operating conditions. Considering such fact, the current study is intended to carry out a literature survey regarding the efforts towards enhanced journal bearing performance based on proper selection of geometrical design for journal bearing. The aggregated data were thoroughly analyzed and assessed utilizing experimental, theoretical as well as numerical means. The outcomes derived from the conducted review represent firm grounds for carrying out extensive modifications into journal bearing design for marine applications. Further, such data will possibly be employed in future research investigations to extend the capability of journal bearing and its functions to attain the most possible enhanced performance in actual operating conditions. Apparently, the vast majority of both experimental and theoretical studies into journal bearing geometrical designs for enhanced performance, 66 in all, have been focused on surface texture accounting for 26.67 % (29 research studies) and 32.43 % (33 research studies) of the total investigations under study respectively. Regarding the experimental studies, realizing promoted performance of lubricating oil film by working on pressure profile has evidently obtained the largest contribution representing 35.5% of the overall bulk of the reviewed efforts, Figure 6.

Research on Partial Discharge Characteristics of Suspension Defect in GIS under the Action of Voltage and Current

Abstract Gas insulated switchgear (GIS) is a critical component in power system, and the insulation testing is crucial before putting it into operation. Despite passing AC withstand tests, some GIS equipment exhibit insulation faults during operation. Existing AC withstand tests fall short in detecting all insulation faults in GIS equipment. To address this issue, a proposal is made to conduct a comprehensive simulation of actual GIS equipment operating conditions through a combined voltage and current boost test, aiming to address the limitations of existing tests. This study, based on a 330kV GIS test platform, compares the partial discharge characteristics of suspension defects under traditional voltage-boosting mode and the combined voltage and current boost mode. The research investigates the influence of simultaneously applying voltage and current on discharge characteristics. It is observed that the voltage and current boost combined mode significantly increase the partial discharge inception voltage (PDIV) and the corresponding apparent discharge compared to other modes. The apparent discharge quantity after a certain period of current flow during the discharge development process is greater than that observed in other modes. The current notably enhances the ultrasonic amplitude of partial discharge. These findings establish an experimental foundation for conducting voltage and current combined boost tests in the field.

A new accelerated thermal fatigue experiment method of pistons and its application

This study proposed a new test method to take the piston instead of the internal combustion engine as the experimental object and use electromagnetic induction heating and auxiliary cooling to simulate the actual operating conditions of the piston during engine start-stop, to achieve accurate control of the temperature of the heating and cooling cycles. The experimental process can be accelerated by worsening the service conditions. In order to prove the feasibility of this scheme, the temperature field distribution, fatigue life, and failure mode of the piston are compared and analyzed using finite element simulation, theoretical calculation, and surface topography observation. The results show that the error between the simulated temperature value of the key point of the piston and the experimental value of the actual operating condition is less than 5%, the position and value of the maximum temperature of the piston under the thermal fatigue test condition are consistent with the actual engine operating condition, the error between the fatigue life test results and the theoretical calculation results is less than 10%, and the location and cracking mode of the main crack is consistent with the actual working condition. It is proved that the test method is reasonable and feasible, which can provide an important guarantee for the fast and efficient design of high-performance pistons.

Influence of binder content on gas-water two-phase flow and displacement phase diagram in the gas diffusion layer of PEMFC: A pore network view

Understanding the gas-water flow dynamics in the gas diffusion layer (GDL) is one of the keys to improving the proton exchange membrane fuel cell's (PEMFC) overall performance and avoiding water flooding. Yet, the relationship between the two-phase flow and micro-scale GDL structures (including binder, PTFE, and fiber skeleton) is not well understood. In this study, three-dimensional GDL structures with different fractions of binder contents (φb=0%∼50%) and a fixed porosity of 75.6 % are confidently reconstructed based on high-resolution images from the confocal microscope, implying that the addition of binder will increase the number of large pores and cause a bimodal throat size distribution through morphology analysis. Thereafter, drainage simulations are performed under a wide range of capillary number (−9 < log Ca <0) and viscosity ratio (−3 < log M < 2) by the pore network model (PNM), which robustly predicts the displacement phase diagram of viscous fingering, capillary fingering, stable displacement, and transitional regime. In the viscous fingering and stable displacement regime, the nonwetting phase saturation (Snw) is nearly the same for different φb, implying the fluid invading pathway does not change much with the addition of binder. However, in the capillary fingering regime (refer to the actual operating conditions), Snw increases rapidly with φbat the breakthrough time and its transient value continues to increase until the steady state, which may be attributed to the increased fractions of pores above the capillary threshold attributed by the bimodal throat size distribution. In addition, the effective water permeability increases sharply with φb, whereas the gas permeability remains almost constant, which means such pore structure alteration by adding the binder is beneficial to water disposal in PEMFC. This research provides insights into delineating the effect of pore and throat size distribution alteration by adding binder on two-phase dynamics in GDL.

Study on the vibration characteristics of double-row tapered roller bearings for high-speed rail axle box

PurposeThe purpose of this paper is to establish a dynamic model considering the actual operating conditions of the train and to study the dynamic performance and vibration characteristics of axle box bearings under different operating conditions.Design/methodology/approachIn this paper, based on the internal contact characteristics of double-row tapered roller bearings, a dynamic model considering the actual operating conditions of the train is established. The correctness of the model is verified by the vibration test of the bearing. Comparative analysis was conducted on the effects of axial force, radial force and rotational speed on the angular velocity of the cage, slip rate and vibration acceleration level of the inner ring.FindingsAs the force increases, the slip rate of the cages on both sides decreases, and the vibration acceleration level of the inner ring increases. With the increase of rotational speed, the cage slip rate of the axle box bearing increases and the vibration acceleration level of the inner ring increases.Originality/valueA dynamic model is established considering the actual operating conditions, and the dynamic performance and vibration characteristics of the axle box bearing under different operating conditions are analyzed by numerical method. The research content can provide reference for the parameter design of high-speed railway bearings.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0085/

Progressive Test and Evaluation Strategy for Verification of KF-X AESA Radar Development

This paper describes a progressive test and evaluation strategy for verification of Korean Fighter eXperimental (KF-X) AESA(Active Electronically Scanned Array) radar development. Three progressive stages of development test and evaluation were officially performed from simulated test conditions to actual operating conditions according to standards: radar function/performance and avionics integration. KF-X AESA radar development is repeatedly verified by progressive stages consisting of five tests: Roof-lab ground test, System Integration Laboratory(SIL) ground test, Flying Test Bed(FTB) test, KF-X ground test, and KF-X flight test. As a result, the risk factor decreases as stages and tests progress. Therefore, development test and evaluation of KF-X AESA radar are successfully performed at low development risk.

Modified reconstruction of boiler numerical temperature field based on flame image feature extraction

ABSTRACT Computational fluid dynamics (CFD) method is a common method to obtain the temperature field distribution within the furnace. However, in order to reduce computational complexity, the numerical simulation involve simplifications in boundary conditions and model parameters. As a result, the temperature field distribution deviates from the actual operating conditions. This paper proposes a numerical temperature field modification method based on flame images. Flame images corresponding to the operational conditions are collected using the Industrial Flame Monitoring System (IFMS). The flame images are preprocessed, and the contour of the flame’s core region is extracted using the Mask Region-based Convolutional Neural Network (Mask R-CNN) method. The geometric features of the flame are extracted, and matrix calculations are applied to modify the numerical temperature field. The modified temperature field exhibits a deviation in the combustion center, aligning with the actual operation of the boiler. A comparison between the modified temperature field and the temperature measurements from flue gas shows consistent temperature trends. The absolute error (AE) under different operating conditions is under 8.8 K, and the relative error (RE) remains below 1.3%. The analysis results demonstrate that it can enhance the accuracy of temperature field calculations by the modification from flame image features.

Effect of runner radial installation deviation on the flow characteristics of the 1000MW turbine

Abstract The flow simulation of a hydraulic turbine is not limited to calculations and analyses under ideal conditions and simplified models, but it should also consider the existence of radial installation deviations in actual operating conditions and their influence on the flow of the turbine. Therefore, this study focuses on a 1000MW unit and analyzes the internal flow characteristics under actual operating conditions while considering the radial installation deviations of the turbine wheel. The results show that the absolute value of pressure increases with the increase of radial deviation, but the difference value remains almost constant. And it also indicates that the magnitude of the radial forces increases with the increase in radial installation deviations. There are two linear relationship curves, one before 0.5mm and one after 0.5mm, with the latter growing at a faster rate. Furthermore, taking the crown as an example, the influence of the wall velocity-generated dynamic pressure on the clearance is different. Lastly, considering the magnitude of the combined forces and vibration amplitude, the crown is the most critical part that should be given attention. The research findings can guide the high-quality installation of 1000MW units during major overhauls and provide valuable technical references for similar units. The research outcomes can also guide the initial installation and major overhaul stages of 1000MW units and offer beneficial technical references for other similar units.

Tribological evaluation of thermoplastic polyurethane-based bearing materials under water lubrication: Effect of load, sliding speed, and temperature

Polymers are widely used in bearing applications. In the case of water-lubricated stern tube bearings, thermoplastic polyurethane (TPU)-based composites are used due to their excellent wear resistance, corrosion resistance, and tunable mechanical properties. Their tribological performance, however, depends on operating conditions. In this work, TPU was blended with carbon fiber, graphene platelet, and ultra-high molecular weight polyethylene (UHMWPE). Friction tests of TPU based-composites against copper countersurface were carried out in water to mimic the actual operating conditions of the bearing. Most of the resulting contacts were in the boundary lubrication regime, in which friction was attributed to both contact mechanics of asperities as well as water lubrication. Our results show that the viscoelasticity of TPU has a considerable impact on its tribological performance. Water lubrication at 50 °C promotes the softening of polymer surface material during sliding, resulting in higher fluctuation in the coefficient of friction and wear loss. This is attributed to the reduced thermomechanical properties. In addition, Schallamach waviness is observed on worn surface. The tribological properties of TPU are significantly improved by the inclusion of carbon fiber, graphene platelet, and UHMWPE. The formation of graphene transfer-layers and UHMWPE transfer film reduces friction and wear loss, while the inclusion of carbon fiber enhances wear resistance due to improved mechanical properties and load bearing capacity.

Microbial nanomaterials: Role in sustainable agricultural practices

The increased use of chemical fertilizers, pesticides, soil-based heavy metals to improve productivity in agriculture results into higher pollution level in agroecosystem. It has become a major issue on a global scale that seriously jeopardizes people’s health and welfare as well as affects society and overall economy. In view of this, there is an urgent need to detect pollutants in the agroecosystem so that remediation practices can be implemented in time. The evolution of more responsive, affordable and precise technology is needed to create nano-sensors or nanodevices that can be used to monitor agricultural pollution, and the processes involved in pollution control. Major focused ones are those that can detect pollutants at very low concentration levels, as well as point-to-point sensing, in situ, and uninterrupted monitoring devices that offer synchronized data. These sensors are readily available in the market for the detection of organic pollutants, gases, volatile organic molecules, heavy metal ions, hazardous metal ions, etc. but they consume a lot of power and lack sophisticated technologies for improved selectivity and sensitivity. Their precision, sensitivity, response speed and environmental stability under actual operating conditions can all be improved with the aid of nanotechnology. In this study an attempt was made to describe how microbial biosensors can be used to detect toxic materials in agroecosystems. Additionally, an application of nanomaterials as pesticides and antimicrobial agent has also been discussed.

Electrical behavior and water phase transformation in multi‐walled carbon nanotube/polytetrafluoroethylene composite films

AbstractMulti‐walled carbon nanotubes (MWCNTs) with excellent physiochemical properties have been recently applied to energy/power generation and storage systems encompassing polymer electrolyte membrane fuel cells (PEMFCs). However, there is a lack of investigations of the properties of MWCNT composites themselves under the actual operating conditions of systems. In this paper, MWCNTs/polytetrafluoroethylene (PTFE) composites were fabricated as electric and hydrophobic components for energy/power systems. The electrical properties, heating behavior, hydrophobicity, and water evaporation behavior of the composites are characterized within the operating voltage ranges of PEMFC. With 50% MWCNT content, the conductivity and the contact angle were 11.83 S/cm, and the contact angle 128.1°, respectively. The MWCNT/PTFE composite film showed a linear temperature rise with voltages and rapid temperature saturation within 40 s. The rate in the initial heating range was measured at 0.5°C/s for the voltage of 0.5 V. The voltage increase induced an exponential decrease in the height of water droplets on the composite surface. The evaporation rate increased almost 10‐fold, from 0.013 mm/min at 0.0 V to 0.12 mm/min at 1.0 V. The proposed characteristics of the functional composite provide insights into the material requirements for electrochemical devices, including PEMFC.Highlights Multi‐walled carbon nanotube/polytetrafluoroethylene composites can be applied to energy storage and power generation. Key properties of the composites are proposed for polymer electrolyte membrane fuel cell (PEMFC) operating conditions. The composite has a fast heating by high conductivity and temperature uniformity. Water‐vapor transformation under PEMFC operating voltage is quantified.

Two‐stage stochastic‐robust planning of distributed energy storage systems with Archimedes optimisation algorithm

AbstractWith the advancement of energy storage technologies, energy storage systems (ESSs) have emerged as a promising solution for distribution networks to mitigate the impact of intermittent and violate renewable energy sources. The optimal planning of distributed ESS is studied to minimise the investment and operational costs for the distribution system operator. To address the various uncertainties associated with load demand and distributed generation, the authors formulate the problem as a two‐stage stochastic‐robust optimisation problem. The proposed formulation implements various representative scenarios of actual operating conditions and constructs the robust uncertainty set to ensure feasibility under worst‐case scenarios. In view of the computational complexity of the proposed model, a solution approach combining the Archimedes optimisation algorithm and the global optimisation method is presented. By decomposing the investment and operation stages, the subproblems are relaxed into mixed integer second‐order cone programming models, which can be solved in parallel based on scenarios. Numerical studies are carried out on a 17‐node test system to demonstrate the validity of the proposed model and algorithm. In addition, a comparison between the proposed method and the genetic algorithm is performed, to illustrate its superiority in solving speed and solution optimality.

Experimental Validation of Electrothermal and Aging Parameter Identification for Lithium-Ion Batteries

Modeling and predicting the long-term performance of Li-ion batteries is crucial for the effective design and efficient operation of integrated energy systems. In this paper, we introduce a comprehensive semi-empirical model for Li-ion cells, capturing electrothermal and aging features. This model replicates the evolution of cell voltage, capacity, and internal resistance, in relation to the cell actual operating conditions, and estimates the ongoing degradation in capacity and internal resistance due to the battery use. Thus, the model articulates into two sub-models, an electrothermal one, describing the battery voltage, and an aging one, computing the ongoing degradation. We first propose an approach to identify the parameters of both sub-models. Then, we validate the identification procedure and the accuracy of the electrothermal and aging models through an experimental campaign, also comprising two real cycle load tests at different temperatures, in which real measurements collected from real Li-ion cells are used. The overall model demonstrates good performances in simulating battery characteristics and forecasting degradation. The results show a Mean Absolute Percentage Error (MAPE) lower than 1% for battery voltage and capacity, and a maximum absolute error on internal resistance that is on par with the most up-to-date empirical models. The proposed approach is therefore well-suited for implementation in system modeling, and can be employed as an informative tool for enhancing battery design and operational strategies.

Ion Dynamics at the Intermediate Charging State of the Sodium Vanadium Fluorophosphate Cathode.

Na super ionic conductor (NASICON)-type polyanionic vanadium fluorophosphate Na3V2O2(PO4)2F (NVOPF) is a promising cathode material for high-energy sodium-ion batteries. The dynamic diffusion and exchange of sodium ions in the lattice of NVOPF are crucial for its electrochemical performance. However, standard characterizations are mostly focused on the as-synthesized material without cycling, which is different from the actual battery operation conditions. In this work, we investigated the hopping processes of sodium in NVOPF at the intermediate charging state with 23Na solid-state nuclear magnetic resonance (ssNMR) and density functional theory (DFT) calculations. Our experimental characterizations revealed six distinct sodium coordination sites in the intermediate structure and determined the exchange rates among these sites at variable temperatures. The theoretical calculations showed that these dynamic processes correspond to different ion transport pathways in the crystalline lattice. Our combined experimental and theoretical study uncovered the underlying mechanisms of the ion transport in cycled NVOPF and these understandings may help the optimization of cathode materials for sodium-ion batteries.

Power plant systems performance assessment with applications of combined pinch and exergy analysis

Steam power plants forms an effective share of global electricity production. Thus, improving such plants performance is crucial to minimize its environmental effects and to enhance operational economy. Al-Mosyab thermal power station in Iraq is considered as a case study of this paper, with an objective of achieving best system performance. A combined pinch & exergy analysis (CPEA) is conducted under actual operating conditions. Further analytical attempt is varying pressure (165, 175, 185) bar, and temperature (450, 550, 620) °C at selected cycle location. Examining thereby the impact of each variable on the system power output, exergy destruction and 2nd low efficiency. The Engineering Equation Solving program (EES) is used for the simulation of each system components under these various operating conditions. The yielded results showed that the maximum mechanical & thermal output are (36.75 & 94.88) % of fuel energy respectively, while, turbine, boiler and condenser irreversibility and 2nd law efficiency are (157.76, 1086.18, 303.19) kJ/kg) and (88.36, 68.97, 28.68) % respectively. The analytical part of the analysis however showed that the high-pressure turbine network output increases by about (1%) with pressure variation, while such increase rise up to (70%) with temperature variation. Final concluded results predicted that best performance could be obtained at maximum pressure and temperature of (175) bar and (620) °C respectively.