Steady-state Load Research Articles

Reliability research of hypervapotron under steady-state thermal load

As one of the key components, the divertor target directly facing the plasma and bearing the high thermal load makes a great impact on the operation of tokamak. Reliability research needs to be performed to verify the rationality of this structure. In this paper, optimization and reliability studies were performed for the hypervapotron structure, which referred to the model proposed by Escourbiac et al. Euler-Euler model coupled with the RPI boiling model was used in process of subcooled boiling numerical analysis for hypervapotron. Heat transfer performance with different types of fin was studied and the downstream triangular fin was eventually adopted in the optimized design. Based on this, process of optimizing the gap between the fin and the wall was conducted. The thermal-mechanical analysis results showed that the optimized design can satisfy allowable temperature and structural strength requirements under steady-state thermal load of 10 MW/m2. Subsequently, elastoplastic analysis during cyclic loads was conducted to search local weak spots. Fatigue life was calculated to be 7725 cycles based on numerical analysis and S-N curve. Ratchet assessment result of 10 cycles of thermal stress showed that this design can prevent ratchet failure. This paper proposed one new design of divertor target unit and verified its reliability on fatigue life and ratchet failure, also providing one system analysis process and method for hypervapotron thermal reliability.

Acoustics and vibrations in a complex piping network with pump startup–shutdown transients

Pump dynamic operational conditions result in extreme transient events that can enhance the response of piping networks. The predominant transients during rapid startup and shutdown are mainly studied for centrifugal pumps and are scarce for reciprocating pumps. Our study extends the conventional steady-state analysis to include the effect of reciprocating pump dynamic loading on pulsatile flow-induced acoustics and vibrations in a complex piping network. The forced response resulting from acoustical–structural coupling is assessed by utilising the one-dimensional multiphysics piping acoustic model and beam structural model. The network responses to pulsatile flows during dynamic pump loading (rapid start-up-shutdown events) are compared to the responses due to pulsatile flows during steady-state pump loading. With pump startup–shutdowns operations accompanied by pulsatile flows, the network response is the result of the combination of the transient and steady-state characteristics of plane acoustic waves and structural vibrations. The dynamic pump loading excites the fundamental, low-frequency acoustic eigenmode that causes transient loading of pipeline similar to reservoir–pipe–valve (RPV) systems.

Fishtail Divertor and its basis surface thermal load bearing performance

Fishtail Divertor (FTD) configuration is a dynamic magnetic field divertor configuration that uses the AC coil installed on the back of the divertor target plate to realize the swing of the strike line. The most important driving force of FTD configuration design is to improve the thermal bearing performance of divertor target plate. Under FTD configuration, the maximum temperature of divertor target plate will eventually reach a dynamic equilibrium state, and it have an obvious jump at both ends of the swing area. With the increase of the swing frequency, FTD configuration can more effectively improve the thermal load bearing performance of the divertor target plate. However, if only to alleviate the steady-state heat load, the swing frequency of FTD no need to be higher than 100 Hz. FTD configuration has engineering application prospects in future fusion reactors. Under a swing distance of 10 cm and a thermal load condition of qp=100MW/m2 and λT=5mm (steady state), Triangular wave Fishtail Divertor (TFTD) swing frequency exceeds 5 Hz or Sine wave Fishtail Divertor (SFTD) swing frequency exceeds 20 Hz, the maximum temperature of target plate can be lower than 900 K. At the same conditions expect the swing frequency is 100 Hz, the maximum temperature under TFTD and SFTD can lower than 700 K and 800 K respectively.

A Review on Failure Analysis of Turbine Blades of Aero Gas Turbine Engine

Almost all commercial electrical power on earth is generated with a turbine, driven either by wind, water, steam or burning gas. Turbine blades are subjected to very strenuous environments inside a gas turbine. They face high temperatures, high stresses, and a potentially high vibration environment. All these factors can lead to blade failure, resulting in catastrophic failure of turbine. In the event of turbine blade failure, turbine does not work and this leads to shutdown of power plant from one to four weeks or longer, depending on the extent of the damage and the procedure used to make the machine operational again, which results in economic loss and service to mankind also stops. For each day of a forced outage, a utility could lose hundreds of thousands of rupees in electrical power. The external and internal surface damages include corrosion, oxidation, crack formation, erosion, foreign object damage and fretting. The internal damage of microstructure include γ’ phase, CoNi3 [(Al, Ti)] phase aging (rafting), grain growth, brittle phases formation, carbides precipitation, creep and grain boundary void formation. These damages produce dimensional change which results in increase in operational stress that leads to deterioration in turbine efficiency. The deterioration of blade material is related to the high gas temperature, high steady state load levels (centrifugal load) and high thermal transient load (trips, start-ups, start downs). In this research, a review of common failures due to metallurgical defects found in gas turbine discussed is presented.

Rheological characteristics of marine sediments from the Ulleung Basin, East Sea to estimate the mobility of submarine landslides

In estimating the geohazards posed by submarine landslides, the rheological properties of marine sediments are of significant importance for their postfailure dynamics. We report an experimental study of the rheological behavior of marine sediments taken from the Ulleung Basin, East Sea and their influence on numerical simulations of debris flow runout. Marine sediments exhibit a typical yield stress behavior, such as that of low-activity clays. For the materials examined, different yield stresses are observed depending on the shearing methods. Steady-state and oscillatory shear tests were conducted for different volumetric concentrations of sediment. According to the test results, the Bingham yield stresses under controlled shear stress and shear rate range from approximately 100 Pa to 1500 Pa, but the yield stresses under oscillatory shear loads range from approximately 25 Pa to 3500 Pa for a given sediment concentration. In the latter cases, the value obtained in the elastic region is approximately doubled. Experiments under steady-state and oscillatory shear loads can be helpful in determining the yield points in the elastic and viscous regions and in explaining changes in the structure of the soil sample due to shear. We apply the range of measured yield strength values to numerical simulations of debris flow runout using a Herschel-Bulkley model and find that only the lowest values of yield strength, despite the low sediment concentrations, could account for the observed runout and thickness distribution. We infer that significant wetting must occur during debris flow motion to attain the observed runout.

Analysis and Operation of a High DC-AC Gain 3-ϕ Capacitor Clamped Boost Inverter

This article introduces a three-phase capacitor clamped inverter with inherent boost capability by relocating the filter components from the AC side to the configuration’s midpoint. This topology has several distinguishing characteristics, including: (a) low component count; (b) high DC-AC gain; (c) decreased capacitor voltage stresses; (d) improved power quality (extremely low voltage and current THDs) without the use of an AC-side filter; and (e) decreased voltage stresses on power semiconductor devices. Simulations were carried out on the MATLAB Simulink platform, and results under steady-state conditions, load and reference change conditions, and phase sequence change conditions, along with THD profiles, are presented. This inverter’s performance was compared to that of similar converters with intrinsic gain. A 1200 W experimental prototype was built to demonstrate the system’s feasibility and benefits. When compared to existing topologies, simulation and experimental results indicate that the proposed inverter provides superior high gain, smooth control, low stress, and a long life time.

Surface Damage and Microstructure Evolution of Yttria Particle-Reinforced Tungsten Plate during Transient Laser Thermal Shock

Tungsten and its alloys are considered to be the most nominated plasma-facing materials in fusion reactors, which will be exposed to enormously rigorous conditions such as thermal load, plasma exposure, and neutron radiation. At present, the research on the behavior of oxide particle-reinforced tungsten-based materials under long-term steady-state heat load and transient thermal shock is insufficient. The purpose of this study is to investigate the performance of yttria particle-reinforced tungsten plates prepared by the wet chemical method under heat loads by means of indirect coupling experiments. An Nd:YAG laser device is used to perform thermal shock events. The surface damage and microstructure evolution of rolled and fully recrystallized samples exposed to laser thermal shock are observed and analyzed. The cracking threshold of the rolled and fully recrystallized samples is about 0.40~0.48 GW/m2; the degree of surface damage of them aggravates with the increased laser power density. What is more, cracks or even melting damage could be observed on the surface and be accelerated by the process of recrystallization, resulting in the degradation of the ability to withstand the thermal shock of the material.

Far-UVC (222\xa0nm) efficiently inactivates an airborne pathogen in a room-sized chamber

Many infectious diseases, including COVID-19, are transmitted by airborne pathogens. There is a need for effective environmental control measures which, ideally, are not reliant on human behaviour. One potential solution is Krypton Chloride (KrCl) excimer lamps (often referred to as Far-UVC), which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. Research demonstrates that when KrCl lamps are filtered to remove longer-wavelength ultraviolet emissions they do not induce acute reactions in the skin or eyes, nor delayed effects such as skin cancer. While there is laboratory evidence for Far-UVC efficacy, there is limited evidence in full-sized rooms. For the first time, we show that Far-UVC deployed in a room-sized chamber effectively inactivates aerosolised Staphylococcus aureus. At a room ventilation rate of 3 air-changes-per-hour (ACH), with 5 filtered-sources the steady-state pathogen load was reduced by 98.4% providing an additional 184 equivalent air changes (eACH). This reduction was achieved using Far-UVC irradiances consistent with current American Conference of Governmental Industrial Hygienists threshold limit values for skin for a continuous 8-h exposure. Our data indicate that Far-UVC is likely to be more effective against common airborne viruses, including SARS-CoV-2, than bacteria and should thus be an effective and “hands-off” technology to reduce airborne disease transmission. The findings provide room-scale data to support the design and development of effective Far-UVC systems.

Cross-code comparison of the edge codes SOLPS-ITER, SOLEDGE2D and UEDGE in modelling a low-power scenario in the DTT

As reactor-level nuclear fusion experiments are approaching, a solution to the power exhaust issue in future fusion reactors is still missing. The maximum steady-state heat load that can be exhausted by the present technology is around 10 MW m−2. Different promising strategies aiming at successfully managing the power exhaust in reactor-relevant conditions such that the limit is not exceeded are under investigation, and will be tested in the Divertor Tokamak Test (DTT) experiment. Meanwhile, the design of tokamaks beyond the DTT, e.g. EU-DEMO/ARC, is progressing at a high pace. A strategy to work around the present lack of reactor-relevant data consists of exploiting modelling to reduce the uncertainty in the extrapolation in the design phase. Different simulation tools, with their own capabilities and limitations, can be employed for this purpose. In this work, we compare SOLPS-ITER, SOLEDGE2D and UEDGE, three state-of-the-art edge codes heavily used in power exhaust studies, in modelling the same DTT low-power, pure-deuterium, narrow heat-flux-width scenario. This simplified, although still reactor-relevant, testbed eases the cross-comparison and the interpretation of the code predictions, to identify areas where results differ and develop understanding of the underlying causes. Under the conditions investigated, the codes show encouraging agreement in terms of key parameters at both targets, including peak parallel heat flux (1%–45%), ion temperature (2%–19%), and inner target plasma density (1%–23%) when run with similar input. However, strong disagreement is observed for the remaining quantities, from 30% at outer mid-plane up to a factor 4–5 at the targets. The results primarily reflect limitations of the codes: the SOLPS-ITER plasma mesh not reaching the first wall, SOLEDGE2D not including ion-neutral temperature equilibration, and UEDGE enforcing a common ion-neutral temperature. Potential improvements that could help enhance the accuracy of the code models for future applications are also discussed.

Constraining organic matter composition and dynamics as a dominant driver of hypoxic blackwater risk during river Murray floodplain inundation

AbstractThe ecology of floodplain ecosystems evolved according to the historical frequency and extent of inundation. In many dryland rivers, inundation frequency has reduced due to regulation, competition for water resources and climate change. In some rivers infrastructure has been constructed to enable temporary rises in water level and more frequent floodplain inundation, delivering environmental water to ecosystems that are dependent on surface water. During such events, the release of dissolved organic carbon (DOC) from inundated plant material may result in depletion of dissolved oxygen (DO). If the rate of DO depletion exceeds re‐aeration, hypoxic conditions can occur. Models have been developed to represent these processes, however, there is a wide range of chemical and biological interactions, and hence model parameters, involved. The aim of this research was: (1) identify the dominant parameters through sensitivity analysis, (2) design and implement a field monitoring program to quantify the inherent variability in those parameters, and (3) translate that input variability into the modelled DO, ultimately to support risk management decisions when planning delivery of environmental water. The results indicated that the mass of organic matter on a floodplain had the greatest impact on the modelled DO concentrations. Based on the field monitoring results, the steady state load of organic matter, that is, when the accumulation and decay rates are equal, was estimated, and vegetation mapping used to apply the field monitoring results across the floodplain for a 206 km reach of river of the River Murray, Australia. The model results from multiple, cumulative, operations identified one particular high‐risk operational site. The results are useful to prioritize monitoring effort to focus on the most sensitive model parameters and indicate that the likelihood of hypoxic conditions can be reduced through slower rates of inundation and timing events to coincide with periods with lower water temperature. The methodology developed can be transferred to other sites where hypoxic conditions are a potential outcome associated with delivery of environmental water.

SOLPS-ITER simulations of high power exhaust for CFETR divertor with full drifts

One of the major challenges for the Gigawatt-class Chinese Fusion Engineering Testing Reactor (CFETR) is to efficiently handle huge power fluxes on plasma-facing components , especially the divertor targets. This work investigates the effects of two candidate radiation impurity species, argon (Ar) and neon (Ne), with two different divertor geometries (baseline and long leg divertor geometry) on the reduction of steady-state power load to divertor targets in CFETR by using the SOLPS-ITER code package with full drifts and kinetic description of neutrals. The modeling results show clearly that increasing the seeding rate of Ar or Ne with fixed fueling gas D2 injection rate reduces the target electron temperature and heat flux density for the baseline divertor geometry, which can be reduced further by higher D2 injection rate. With a high impurity seeding rate, partial detachment with steady-state power load at the divertor target below the engineering limit of 10 MW m−2 is demonstrated. In addition, the radiation efficiency for Ar is better than that for Ne. Increasing the divertor leg length reduces the electron temperature and heat load at the targets. This modeling, therefore, suggests that a long leg divertor design with Ar seeding impurity is appropriate to meet the CFETR divertor requirements.

New organic-air flow fuel cell and electrolyser for stationary energy storage

In this work, we propose an innovative hybrid flow battery using anthraquinone disulfonic acid (AQDS) based negolyte in an AQDS-oxygen fuel cell and AQDS-oxygen electrolyser as a discharging and charging devices, respectively. The performance of the system is studied under defined conditions (SoC, temperature) using a complex methodology including EIS, dynamic load curves, steady-state galvanostatic loads and galvanostatic charge-discharge cycles. The internal components of both devices are optimised with respect to performance and its stability. When compared to a standard vanadium-based negolyte, the AQDS-based fuel cell shows lower ohmic resistance and lower capacity fade due very slow AQDS permeation through the cation-exchange membrane. On the other hand, its open circuit voltage is approx. 0.48 V lower and the fuel cell shows higher overall resistance due to deteriorating performance of oxygen gas diffusion electrode, which is most probably related to the adsorption of the permeated AQDS on the platinum electro-catalyst. The method of performance restoration by applying opposite polarization to the fuel cell is successfully tested and optimised enabling stable battery operation. • Innovative organic-oxygen fuel cell and electrolyser proposed. • Acidic solution of anthraquinone disulfonic acid (AQDS) used as negolyte. • Stable performance of the electrolyser with Ir-based positive electrode. • Fuel cell performance decay due to deactivation of catalyst layer. • Fuel cell performance can be restored by reverse polarization.

Thermo-Mechanical Analysis and Design Update of the Top Cap Region of the DEMO Water-Cooled Lithium Lead Central Outboard Blanket Segment

Within the framework of the EUROfusion research and development activities, the Water-Cooled Lithium Lead (WCLL) Breeding Blanket (BB) is one of the two candidates to be chosen as the driver blanket for the European DEMO nuclear fusion reactor. Hence, an intense research work is currently ongoing throughout the EU to develop a robust conceptual design able to fulfil the design requirements selected at the end of the DEMO pre-conceptual design phase. In this work, the thermo-mechanical analysis and the design update of the top cap (TC) region of the DEMO WCLL Central Out-board Blanket (COB) segment is presented. The scope of the work is to find a design solution of the WCLL COB TC region able to fulfil the design requirements, prescribed by the reference RCC-MRx code, under the selected nominal and accidental steady state loading scenarios. The activity herein presented moved from the WCLL COB reference design, purposely modified in compliance with the adopted thermal and mechanical requirements in order to attain a robust TC region geometric layout. In the end, a geometric configuration called “TC region-mod++” was determined, foreseeing a TC able to safely withstand both nominal and accidental loads. Nevertheless, some criticalities still hold in the internal stiffening plates and, therefore, further and finer analysis are necessary to fully match the goal. In any case, it was also found that the proposed approach for the design update is promising and worthy to be further pursued. The work was performed following a theoretical–numerical approach based on the finite element method (FEM) and adopting the quoted Ansys commercial FEM code.

Design and analysis of piston using aluminum alloy and composites in Solidworks and Ansys

The present paper reports the modelling and analysis of piston fabricated from Steel, Aluminum alloy and Composites for 4-stroke petrol engine of a specific version followed by comparison between the both. Solidworks software is used for 3D modelling of the piston. Ansys software is used for static structural and steady state thermal analysis of the piston. A static-structural analysis is being performed to find out the deformation, stresses, strains, and forces in structures or factors caused by the loads. A static analysis calculates the impact of steady loading conditions on a structure, while ignoring inertia and damping as those carried by time varying loads. Steady state thermal analysis is used for evaluating the thermal equilibrium of a system in which the temperature remains constant over time. Steady-state thermal analysis can be used to determine the temperature distributions in an object with thermal loads that do not vary with time. The heat transfer includes conduction, convection and radiation. Most thermal analyses are steady state thermal analyses. Total Deformation, Factor of Safety (F.O.S.), Equivalent (Von-mises) stress and Equivalent (Von-mises) strain were obtained under static structural analysis for piston using different materials. Total heat flux, Directional heat flux and temperature distribution were obtained using steady state thermal analysis. Performance of standard material used for piston and aluminum alloys was compared and the best material was recommended for manufacturing of piston.

Modeling of active and reactive power steady state load in optimal reactive power planning

With the flow of time, the load patterns in electricity markets are changing rapidly in world-wide. The power engineers are becoming more vigilant to provide an uninterrupted power supply at any loading conditions. This article proposes a unique planning strategy of reactive power (VAr) considering static load model in power transmission systems. The active and/ or reactive power oriented exponential load model for static load is considered during the study of load flow solution. The power losses from load flow solution is measured and minimized through the proper placement of compensation devices. Series and shunt type FACTS (flexible ac transmission system) devices are used in order to compensate the flow of reactive power. Also, the separate and collective effects of active and reactive power exponents on load flow study are included during total operating cost (TOC) calculation of the system. The TOC is formulated empirically by adding different cost components such as cost owing to real power loss, VAr generation cost component, compensation device cost components and line charging cost. To validate the impetus of the proposed model, IEEE 14, IEEE 39 and IEEE 118 bus transmission systems are considered in this research work.

Fatigue life prediction of hypervapotron for CFETR divertor

The engineering design of China Fusion Engineering Testing Reactor (CFETR) will be finished in the end of this year. Compared with Experimental Advanced Superconducting Tokamak (EAST), this is a large development which means closer to commercial fusion reactors. The design objective of CFETR divertor requires a steady-state thermal load of 10–20MW/m2 exhaust. There are several design options for the CFETR divertor. Hypervapotron with its superior performance has been researched for several decades as one important candidate for future fusion device divertor. In this paper, a new design of hypervapotron plasma facing unit (PFU) was developed. Horizontal and longitudinal ribs were adopted to generate more vaporized cores to enhance heat transfer. Some optimizations were performed based on the allowable max heat flux (MAHF) to get the final design. Rensselaer Polytechnic Institute (RPI) boiling model of Eulerian Multiphase fluid and k-epsilon model of Viscous were chosen to deal with sub-cooled boiling. 3Sm rule and Bree-diagram was used to confirm the rationality of the structure after thermal-mechanical analysis. Numerical simulation results suggested that CuCrZr alloy will experience cyclic plastic strain. Based on this, fatigue life prediction of the hypervapotron PFU at a steady-state heat flux of 10MW/m2 were carried out through local stress-strain method, neuber curve and design fatigue life curve. Eventually, a fatigue life of approximately 1.2489 year was verified for CFETR divertor. This paper provides a systematic method for fatigue life prediction and reliability analysis of hypervapotron.

Constant Voltage Model of DFIG-Based Variable Speed Wind Turbine for Load Flow Analysis

At present, the penetration of wind-driven electric generators or wind power plants (WPPs) in electric power systems is getting more and more extensive. To evaluate the steady state performances of such power systems, developing a valid WPP model is therefore necessary. This paper proposes a new method in modeling the most popular type of WPP, i.e., DFIG (doubly fed induction generator)-based WPP, to be used in power system steady state load flow analysis. The proposed model is simple and derived based on the formulas that calculate turbine mechanical power and DFIG power. The main contribution of the paper is that, in contrast to the previous models where the DFIG power factor has been assumed to be constant at unity, the constant voltage model proposed in this paper allows the power factor to vary in order to keep the voltage at the desired value. Another important contribution is that the proposed model can be implemented in both sub-synchronous and super-synchronous conditions (it is to be noted that most of the previous models use two different mathematical models to represent the conditions). The case study is also presented in the present work, and the results of the study confirm the validity of the proposed DFIG model.

Performance of a capstone gas turbine based power plant working on high Butane LPG

This paper presents the operational performance results of a 30 kW microturbine generator (MTGs) fed with high butane content liquefied petroleum gas, while subjected to a test procedure involving steady and transient load conditions. To evaluate the performance, measurements of turbine and generator parameters were gathered from its original unit controller, as load changes were applied. For the stand-alone mode detailed graphs of the test results are presented, showing the transparency and robustness of the turbine-generator set to the used fuel, judging by the quality of the output electric parameters. The results from this performance testing provide good insight into the use of high-butane content liquefied petroleum gas as fuel for the tested microturbine. The continuous use of a fuel would need more tests to establish that the life of the critical components of the microturbine are not hampered from what they are on the baseline fuel.
 The course of selected performance parameters in the microturbine generator is described in this document. The analysis of test results of the microturbine under steady-state and transient operation have been made. Both in steady state and transient conditions, values of output power, speed fluctuation, emissions, noise levels, and exhaust gas temperatures remained under acceptable levels.

A journal bearing performance prediction method utilizing a machine learning technique

A predictive analytics methodology is presented, utilizing machine learning algorithms to identify the performance state of marine journal bearings in terms of maximum pressure, minimum film thickness, Sommerfeld number, load and shaft speed. A dataset of different bearing operation states has been generated by solving numerically the Reynolds equation in the hydrodynamic lubrication regime, for steady-state loading conditions and assuming isothermal and isoviscous lubricant flow. The shaft has been modelled with four different values of misalignment angle, lying within the acceptable operating range, as defined in the existing regulatory framework. The journal bearing was modelled parametrically using generic geometric parameters of a marine stern tube bearing. The lift-off speed was estimated for each loading scenario to ensure operation in the hydrodynamic lubrication regime and the effect of shaft misalignment on lift-off speed has been evaluated. The generated dataset was utilised for training, testing and validation of several machine learning algorithms, as well as feature selection analysis, in order to solve several classification problems and identify the various bearing operational states.

A new generalized cross-connected switched capacitor multilevel inverter topology with high output voltage gain for single phase solar PV unit

Switched capacitor multilevel inverters are gaining much attention these days due to their merits like voltage boosting and voltage balancing characteristics. A Cross Connected Switched Capacitor Multilevel Inverter (C2SC-MLI) topology is proposed in this work. It can synthesize thirteen levels in the terminal voltage waveform and with a voltage boost ratio of 1:3. The topology is extendable by adding additional “n” modules in series. The number of levels (NLevel) and the voltage gain can be increased up to 4i+9 and 1:(i+2) respectively by connecting ‘i’ such ‘n’ modules. The topology also has inherent voltage balancing ability. To prove the advantage of proposed topology it is compared with recent switched capacitor multilevel inverter topologies and conventional multilevel inverter topologies in terms of number of power electronic components required, cost and voltage gain. The performance of proposed topology is validated using simulation in MATLAB and with an experimental prototype rated 0.1 kW fed by a solar PV emulator under steady state and dynamic loading conditions.