Start-up Tests Research Articles

Novel bio-inspired memetic salp swarm algorithm and application to MPPT for PV systems considering partial shading condition

This paper proposes a novel bio-inspired optimization method named memetic salp swarm algorithm (MSSA). It is developed by extending the original salp swarm algorithm (SSA) with multiple independent salp chains, thus it can implement a wider exploration and a deeper exploitation under the memetic computing framework. In order to enhance the convergence stability, a virtual population based regroup operation is used for the global coordination between different salp chains. Due to partial shading condition (PSC) and fast time-varying weather conditions, photovoltaic (PV) systems may not be able to generate the global maximum power. Hence, MSSA is applied for an effective and efficient maximum power point tracking (MPPT) of PV systems under PSC. To evaluate the MPPT performance of the proposed algorithm, four case studies are undertaken using Matlab/Simulink, e.g., start-up test, step change of solar irradiation, ramp change of solar irradiation and temperature, and field atmospheric data of Hong Kong. The obtained PV system responses are compared to that of eight existing MPPT algorithms, such as incremental conductance (INC), genetic algorithm (GA), particle swarm optimization (PSO), artificial bees colony (ABC), cuckoo search algorithm (CSA), grey wolf optimizer (GWO), SSA, and teaching-learning-based optimization (TLBO), respectively. Simulation results demonstrate that the output energy generated by MSSA in Spring in HongKong is 118.57%, 100.73%, 100.96%, 100.87%, 101.35%, 100.36%, 100.81%, and 100.22% to that of INC, GA, PSO, ABC, CSA, GWO, SSA, and TLBO, respectively. Lastly, a hardware-in-the-loop (HIL) experiment using dSpace platform is undertaken to further validate the implementation feasibility of MSSA.

Time-dependent shear rate inhomogeneities and shear bands in a thixotropic yield-stress fluid under transient shear.

We study the rheological responses and shear-rate inhomogeneities and shear banding behaviors of a thixotropic fumed silica suspension in shear startup tests and flow reversal tests. We find that this suspension under transient shear exhibits not only viscoelasticity, yielding, kinematic hardening, and thixotropy, but also time-dependent shear inhomogeneities including bands when the apparent shear rate is below a critical value between 0.1 and 0.25 s-1. Through multiple shear startup tests and flow reversal tests, we find that thixotropy promotes flow heterogeneity while kinematic hardening suppresses it. We propose a simple thixo-plastic constitutive equation that can qualitatively predict the important features of the rheological response and banding dynamics in shear startup tests and flow reversal tests.

Microearthquakes preceding a M4.2 Earthquake Offshore Istanbul

A primary hurdle in observing small foreshocks is the detection-limit of most seismic networks, which is typically about magnitude M1-1.5. We show that a start-up test of a borehole-based seismic network with a much lower detection limit overcame this problem for an Mw4.2 earthquake. This earthquake occurred offshore of Istanbul, Turkey, on a fault system that is likely to rupture in an M > 7 event in the coming decades. In the three days before and two after, a total of 62 or more earthquakes, including at least 18 foreshocks, came from the mainshock source area. The signal similarity of the foreshocks shows a clear increase during the hours before the Mw4.2 mainshock. Similar foreshock sequences have recently been reported for a few well monitored M > 7 plate-boundary earthquakes. The sequence surrounding the Mw4.2 gives the impression of stochastic failures that ended up interactively unloading stress concentrations. The Mw4.2 mainshock then resulted from the accumulated release of significantly smaller events, as suggested by other field and laboratory studies.

A New Method to Estimate Induction Machine Parameters from the No-Load Startup Transient

The paper proposes a new method to estimate the electrical parameters of three-phase induction machines based only on the voltages and currents of the stator acquired during a no-load startup test. The method is based on the instantaneous impedance and on the rotor speed, both estimated according to procedures detailed in the paper. Parameter variations with the speed are determined based on the concept of data windowing and using a single-cage model. Theoretical and practical considerations are presented and discussed, with the method being validated through simulations and also through experimental results obtained for eleven machines with power from 5.5 to 75 kW. The most relevant characteristic of the proposed method is that the variation of the resistance and leakage inductance of the rotor during the transient, caused mainly by skin effect, can be effectively and systematically assessed. The practical results proved that the method has great potential to advantageously replace traditional no-load and blocked-rotor tests as it requires less time and has much lower associated costs.

Dynamic leader based collective intelligence for maximum power point tracking of PV systems affected by partial shading condition

This study presents a novel maximum power point tracking (MPPT) algorithm via dynamic leader based collective intelligence (DLCI) of PV systems affected by partial shading condition (PSC). Different from the conventional meta-heuristic algorithms, DLCI is consisted of multiple sub-optimizers, which can achieve a much wider exploration by fully collaborating the optimization ability of various searching mechanisms instead of a single searching mechanism. In order to achieve a deeper exploitation, the sub-optimizer with the current best solution is chosen as the dynamic leader for an efficient searching guidance to other sub-optimizers. Although the multiple sub-optimizers of DLCI will result in a higher computational complexity, it can offer an enhanced searching ability and a more stable convergence compared to that of conventional meta-heuristic algorithms. Since it does not reply on the system model, DLCI can be easily applied to other optimization tasks. Four case studies, including start-up test, step change in solar irradiation with constant temperature, gradual change in both solar irradiation and temperature, and daily field data of solar irradiation and temperature in Hong Kong, are undertaken. They attempt to evaluate the effectiveness and advantages of DLCI in comparison to that of conventional incremental conductance (INC) and eight typical meta-heuristic algorithms, e.g., genetic algorithm (GA), particle swarm optimization (PSO), artificial bees colony (ABC), Cuckoo search algorithm (CSA), grey wolf optimizer (GWO), moth-flame optimization (MFO), whale optimization algorithm (WOA), and teaching–learning-based optimization (TLBO), respectively. Lastly, a dSpace based hardware-in-the-loop (HIL) test is carried out to validate the implementation feasibility of DLCI based MPPT technique. Both the case studies and HIL test demonstrate that the searching ability of DLCI can be significantly improved via an effective coordination between multiple sub-optimizers, which can make the PV system generate more energy (up to 36.64%) and smaller power fluctuation (up to 21.17%) than other methods with a single searching mechanism.

Physical startup tests calculations for Dukovany NPP using MOBY-DICK macrocode

Abstract Physical startup tests are an important part of the operation of each nuclear reactor fuel cycle. This paper is focused on calculations of these tests for Dukovany NPP using MOBY-DICK diffusion macrocode. In this paper two tests are presented, specifically SCRAM test and “Weight of the 6th group of control assemblies” test. Both tests are described, methodology of calculation is introduced and results of calculations are compared with experimental data.

Modeling, Simulation and Analysis of Induction Motor for Electric Vehicle Application

High power induction motor (IM) is widely used in industries and recently has been put into electric vehicle as the replacement of the internal combustion engine. In order to study the characteristics of the IM, a model of three-phase squirrel cage induction motor is designed and developed using MATLAB Simulink tool. Synchronous reference frame (SRF) technique is implemented to simplify the equivalent circuit model. Based on state space form, a flux linkage equation is developed using three stages transformation matrices. It demonstrated a good performance with fast response for AC start-up test, where simulated induced torque, rotor speed, mechanical output power, efficiency, slip and stator current waveforms were generated accordingly. Indeed, the developed IM model can be used as a starting platform to further study and analyses the IM drives performance for electric vehicle application.

Unsteady Pressures Influenced by Trapped Air Pockets in Water-Filled Pipelines

Trapped air pockets may cause severe operational problems in water-filled pipelines. This paper investigates the dynamic behaviour of a single trapped air pocket. A single air pocket creates distinct changes of amplitude, shape and timing of unsteady flow pressure waves when it is located at some point in a pipeline. The severity of the resulting hydraulic transients depends on the size, pressure and position of the trapped air pocket. In this paper, the air pocket is incorporated as a boundary condition in the discrete gas cavity model (DGCM) that also considers the effects of unsteady skin friction. Two distinct case studies are presented: (1) start-up test case (flow starting from rest) and (2) shut-down test case (flow stoppage). The start-up test case has been performed in the University of Montenegro pipeline apparatus (length 55 m, internal diameter 18 mm). A trapped air pocket is confined at the downstream end of the pipeline. The transient event is initiated by rapid opening of a valve positioned at the initial air/water interface. The shut-down test case has been carried out in the University of Adelaide laboratory apparatus (length 37 m, internal diameter 22 mm). A trapped gas pocket is maintained near the midpoint of the pipeline. The shut-down event is initiated by rapid closure of the downstream-end valve. Results of numerical simulations and laboratory investigations are presented and they show profound effects of unsteady skin friction on pressure histories.

Effect of a functional polymer on the rheology and microstructure of sodium alginate

Here, we report on the effect of functional copolymer poly(N-isopropylacrylamide-co-4-vinyl-phenylboronic acid) (NIBA) on the rheology and network structure formed by sodium alginate (SA) through linear and nonlinear viscoelasticity measurements. The hydrogel moduli at pH 3 increased with increasing NIBA addition, while the yield point decreased. Furthermore, these hydrogels showed strain-softening behavior, weak G″-overshoot marking the onset of nonlinearity, and good self-healing properties after large deformation. The zero-strain nonlinearity parameter (Q0) was found to be more sensitive to NIBA-addition than the linear viscoelastic properties. The blends showed a clear peak in the startup test except for SA alone and the peak intensity increased with increasing NIBA-concentration. Finally, based on all data, gelation mechanism and interaction of SA and NIBA will be clarified.

Test Stand for the Experimental Investigation of Turbochargers with 3D Printed Components

Abstract The paper discusses the universal test stand which allows determining the characteristics of turbochargers. Currently, there are works carried out in the world aimed to develop innovative fluid-flow machines, made partly with the use of rapid prototyping technology. This type of manufacturing technology allows reducing production time and costs in comparison to conventional methods of prototyping. This article also discusses start-up tests of the experimental test stand using a commercial turbocharger and the comparison between calculated and experimental results. In this paper, there are also described some modifications of the test stand, made prior to the start-up test, which were necessary to get more accurate characteristics of turbochargers. This work is an introduction to the investigation on turbomachines, whose elements were manufactured using the rapid prototyping technology.

Measurement of vibration and stress for APR-1400 reactor internals

Abstract The U.S. Nuclear Regulatory Commission, Regulatory Guide 1.20 needs to perform a comprehensive vibration assessment program for reactor internals during preoperational and startup testing for nuclear power plants and extended power uprate. Although the measurement program is one of the core programs, it is rarely carried out except for a first-of-a-kind or a unique design. This article describes measurement results of vibration and stress for the comprehensive vibration assessment program for an APR-1400 reactor internals. The measurement was performed at an upper guide structure during the pre-core hot functional test of Shin Kori unit 4 reactor internals because the Shin Kori unit 3 and 4 are the first construction project for the APR-1400, and the upper guide structure assembly was to design change compared with the valid prototype. We confirmed that all measured results are within the test acceptance criteria. It means that the structural integrity of the APR-1400 reactor internals was secured for the flow-induced vibration.

RELAP5/MOD3.3 Analysis of the Loss of External Power Event with Safety Injection Actuation

The code assessment typically comprises basic tests cases, separate effects test, and integral effects tests. On the other hand, the thermal hydraulic system codes like RELAP5/MOD3.3 are primarily intended for simulation of transients and accidents in light water reactors. The plant measured data come mostly from startup tests and operational events. Also, for operational events the measured plant data may not be sufficient to explain all details of the event. The purpose of this study was therefore besides code assessment to demonstrate that simulations can be very beneficial for deep understanding of the plant response and further corrective measures. The abnormal event with reactor trip and safety injection signal actuation was simulated with the latest RELAP5/MOD3.3 Patch 05 best-estimate thermal hydraulic computer code. The measured and simulated data agree well considering the major plant system responses and operator actions. This suggests that the RELAP5 code simulation is good representative of the plant response and can complement not available information from plant measured data. In such a way, an event can be better understood.

Biosolids composting at the Borough of Mechanicsburg, PA WWTP

Abstract The Borough of Mechanicsburg, located in central Pennsylvania, was experiencing challenges in finding sufficient agricultural fields to continue the beneficial use of their anaerobically digested liquid wastewater treatment plant Class B biosolids. At the time, the only alternative available was dewatering and going to landfill, which is significantly more expensive. Due to environmental concerns and costs related to the alternatives, biosolids composting was selected to produce a Class A/EQ (Exceptional Quality) biosolids product, thus providing expanded opportunities for beneficial use. From the initial feasibility review to operational status, the implementation spanned nine (9) years, starting in 2005. The upgrade to composting was in conjunction with many other plant upgrades. Material Matters, Inc. provided support through the entire process including the feasibility study, pilot testing, cost assessment, compost facility design requirements, equipment assessment and recommendation, start-up testing, software development, permitting, fertilizer registration, product promotion, and marketing.

Numerical Simulation of Measurements during the Reactor Physical Startup at Unit 3 of Rostov NPP

The results of numerical calculations and measurements of some reactor parameters during the physical startup tests at unit 3 of Rostov NPP are presented. The following parameters are considered: the critical boron acid concentration and the currents from ionization chambers (IC) during the scram system efficiency evaluation. The scram system efficiency was determined using the inverse point kinetics equation with the measured and simulated IC currents. The results of steady-state calculations of relative power distribution and efficiency of the scram system and separate groups of control rods of the control and protection system are also presented. The calculations are performed using several codes, including precision ones.

The study of the mitigation strategy of Lungmen ABWR nuclear power plant using RELAP5 and FRAPTRAN with the interface SNAP

In this study, the model of Lungmen ABWR NPP (nuclear power plant) using RELAP5 with the interface SNAP was established. This RELAP5/SNAP model performed the mitigation strategy simulation and study. The main systems of the mitigation strategy are RCIC (Reactor Core Isolation Cooling System), ADS (Automatic Depressurization System), and AC-Independent Water Addition System (ACIWA). This research focuses to assess the usefulness of the mitigation strategy under Fukushima-like conditions. There are three steps in this study. The first step is the establishment of Lungmen NPP RELAP5/SNAP model using the systems data, startup tests reports, and FSAR. The second step is the mitigation strategy simulation and analysis under Fukushima-like conditions using the RELAP5/SNAP model. In this step, the case without mitigation strategy was also performed to evaluate the mitigation strategy effectiveness. Finally, the FRAPTRAN analysis with the interface SNAP was performed in this study. This can evaluate the mechanical property and integrity of fuel rods. According to the RELAP5 results under Fukushima-like conditions, the mitigation strategy can maintain the PCT (peak cladding temperature) below the criteria (1088.7 K). And the FRAPTRAN results also present that the mitigation strategy can keep the fuel rods integrity. It indicates that Lungmen NPP would be in a safe situation when Lungmen NPP performs the mitigation strategy.

The startup performance and microbial distribution of an anaerobic baffled reactor (ABR) treating medium-strength synthetic industrial wastewater

ABSTRACTIn this study, an anaerobic baffled reactor (ABR) with seven chambers was applied to treat medium-strength synthetic industrial wastewater (MSIW). The performance of startup and shock test on treating MSIW was investigated. During the acclimation process, the chemical oxygen demand (COD) of MSIW gradually increased from 0 to 2,000 mg L−1, and the COD removal finally reached 90%. At shock test, the feeding COD concentration increased by one-fifth and the reactor adapted very well with a COD removal of 82%. In a stable state, Comamonas, Smithella, Syntrophomonas and Pseudomonas were the main populations of bacteria, while the predominant methanogen was Methanobacterium. The results of chemical and microbiological analysis indicated the significant advantages of ABR, including buffering shocks, separating stages with matching microorganisms and promoting syntrophism. Meanwhile, the strategies for acclimation and operation were of great importance. Further work can test reactor performance in the treatment of actual industrial wastewater.

Physical startup tests for VVER-1200 of Novovoronezh NPP: advanced technique and some results

Abstract The intention of the startup physics tests was to confirm design characteristics of the core loading and their compliance with safety analysis preconditions. The program of startup tests for the leading unit is usually composed in such a way that is is possible to study as much neutron-physical characteristics as possible in the safest condition of zero power. State-of-the-art safety analysis is including computer codes that use three dimensional neutron kinetics and thermohydraulics models. For the substantiation of such models, for its validation and verification there is a need in reactor experiments that implementing spatially distributed transients. We based on such statements when composing hot zero power physical startup program for the new VVER-1200 unit of Novovoronezh NPP. Several tests unconventional for VVER were developed for that program. It includes measuring the worth for each of control rod groups and measuring of single rod worth from the inserted groups – test that models rod ejection event in some sense.

Influence of pre-shearing on rheometric measurements of an oil-based drilling fluid

Drilling fluids are suspensions of solid particles and present thixotropic and elastoviscoplastic behaviors simultaneously, which turn their rheological characterization into a challenging task. Rotational rheometers are widely employed to determine the properties of these fluids, and one major challenge in rheometric tests carried out with thixotropic fluids is to obtain repeatable results. Submitting the fluid specimen to a known shear history by performing a pre-shear procedure is commonly used to achieve repeatable results with thixotropic fluids. In this paper, the effect of different pre-shearing conditions on the rheological measurements of an oil-based drilling fluid was investigated using cross-hatched parallel plates. Firstly, an adequate aging time to ensure complete fluid restructuring was determined by monitoring the storage modulus, G′, over an oscillatory time sweep experiment. Shear-rate controlled start-up tests were then conducted to evaluate the gel strength and the steady-state shear stress. Nine different pre-shearing conditions were evaluated, and each experiment was performed three times. Finally, the results were analyzed by using two statistical tools: a two-way analysis of variance (ANOVA) and the Tukey’s range test. The analysis shows that despite the good repeatability achieved when the same pre-shear condition is applied, the pre-shearing affects not only the gel strength but also the steady-state shear stress. The ANOVA also revealed that the effect of the pre-shearing shear rate on the fluid rheological behavior is statistically more significant than the effect of the pre-shearing time. The same analysis was performed after 10 s and 10 min of aging, and similar results were obtained.

Schematics for experimental units with pump feed system of propellant components for hydrogen LPE PS units

The development of the advanced cryogenic liquid-propellant engines (LPE) for rocket-space systems (RSS) may require a wide range of autonomous tests of combustion chambers (CC) and gas generators (GG) in experimental units (EU) with pressure and pump feed systems (FS) of propellant components (PC): to be conducted. The article deals with the experimental units with turbopump assembly (TPA) having recirculation and closed circuits and various feed circuits for the gas generator turbine drive unit. Recommendations on startup stabilization and test conditions have been developed by the authors.

A neutron transport and thermal hydraulics coupling scheme to study xenon induced power oscillations in a nuclear reactor

A multi-physics computational methodology to analyze xenon induced power oscillations in a nuclear reactor is developed and presented. The methodology development takes into account both neutron transport and thermal hydraulics behaviors and their inter-dependent feedbacks in a nuclear power reactor as a function of fuel burn-up. The methodology uses the Monte Carlo N-Particle radiation transport computational code (MCNP6) along with its fuel transmutation module (CINDER90), a semi-analytic single channel analysis tool for thermal hydraulics and the SIGACE code suite for temperature dependent neutron interaction cross section processing. A Python script developed couples the physics codes for full automation. The accuracy of the multi-physics computational methodology developed was verified through a benchmark calculation for the published core parameters of a startup test performed at Yonggwang Power Reactor Unit No. 3. The power axial offset and xenon axial offset parameters were calculated for this benchmark case and used to quantify the oscillatory behavior observed, the results of this benchmark study is also presented here. The results showed that the developed methodology was able to capture the underlying phenomena governing xenon induced power oscillations in a nuclear reactor.