Injection Phase Research Articles

Frequency Synchronization and Coherent Combining of Two Fiber Ring Cavities

Low noise synchronization of the frequency and phase of a DFB fiber laser and two fiber ring cavities was achieved based on a two-channel optical injection lock and phase lock loop. Two-channel modulation signals of different frequencies were adopted to extract the phase noise signals of the two fiber ring cavities. Finally, the lasers from the two fiber ring cavities were coherently combined in the closed loop of the control system owing to the synchronous frequency and phase. The power stability and polarization stability of the combined laser was improved under the optical injection lock and phase lock loop. The phase noise of the two cavities was $6.56 \times 10^{-7}$ rad/Hz1/2 and $1.34 \times 10^{-6}$ rad/Hz1/2 at 10 Hz; and $7.77 \times 10^{-8}$ rad/Hz1/2 and $1.35 \times 10^{-7}$ rad/Hz1/2 at 10 kHz. The total combined power was ~580 mW in the closed loop, and the entire system oscillated under a single frequency, providing excellent power scaling ability.

MARBLE MÉLANGE: COMPOSITION VARIATIONS AND FORMATION MECHANISMS

The Olkhon terrane in the Western Baikal area accommodates four types of carbonate-silicate mixtures: injection (protrusion), metamorphic-boudinated, mingling, and tectonite marble mélange. The outcrops of injection mélange consist of a carbonate matrix with inclusions of native silicic rocks found in the immediate vicinities, commonly cover large areas and lack any distinct linearity in the map view. Mélange of the metamorphic boudinage type comprises diopsidite and tremilote-diopsidite fragments in a dolomitic or calcite-dolomitic matrix. Its origin is apparently due to tectonism and related metamorphism of quartz sandstones in Neoproterozoic strata on the passive margin of the Siberian craton. Mingling mélange appears as calcite marble or carbonate-silicate (calciphyre) veins with metadolerite and granite inclusions of different sizes. The veins formed by intrusion of carbonate and silicate melt batches and subsequent fragmentation of silicate rocks that crystallized earlier. Marble tectonites localized in narrow zones record the late phase of ductile marble injection.

Моделирование процессов топливоподачи для работы судового дизеля на водотопливной эмульсии

The article presents the results of the mathematical modeling of marine diesel’s fuel supply processes during the screw characteristic while using diesel fuel and water-fuel emulsion with 30% water content as alternative fuel. As a result of the research, the features of the fuel supply processes and the effect of alternative fuel on the serial fuel equipment injection characteristics during operation in nominal and partial modes were identified. Considering the quality of fuel equipment operation the following features were taken into account, they are: changing fuel supply characteristics; features of fuel atomization in the initial and final phases of injection; increasing stability of the injection in sequential cycles by increasing plunger active stroke; residual pressure oscillations in the high pressure line during injection consecutive cycles. Using the water-fuel emulsion it is possible to significantly increase a quality of marine diesel engine operation, to extend the stable fuel supply range of the serial fuel equipment both from the possibility of speed modes reducing during fine fuel feed and providing forced fuel feed due to absence of repeating injections.

Long-term outcome of novel combined surgical-injection treatment (COSIT) for large hepatocellular carcinoma: Stage 2A IDEAL prospective case series

BackgroundLarge hepatocellular carcinoma (HCC) treatment options have obvious limitations. Our trial comprises ipsilateral hepatic artery ligation and extrahepatic collaterals division (HALED, reinforced by percutaneous tumor injection controlling residual HCC arterial supply. We aimed to evaluate the long term safety and feasibility of the Combined Surgical and Injection of alcohol Treatment (COSIT) as a novel therapy for the large HCC. Material and methodsCandidates' clinical data of the of this case series were prospectively and sequentially reported in accordance with stage 2a development IDEAL (Idea, Development, Exploration, Assessment and Long-term monitoring) recommendations. It included adult patients with HCC (diameter >5 cm) subjected to COSIT coming to our center during a five years' trial evaluating the long term outcome measures. Study ID (NCT03138044 ClinicalTrials.gov). ResultsPatients were 21, their mean age (±standard deviation) was 61·9 (±9·3) years. Eleven (52.4%) patients had tumors diameter >10 cm. 17 (80.9%) patients were advanced BCLC stage. Six modifications were made in this injection phase till it came to a stability. The mean alcohol volume was 72.0 mls. The mean follow-up duration was 16 months. The median overall survival duration was 14 months. The one, three and five years' survival was 71.4%, 23.8% and 4.8%, respectively. Grade 3/4 and 4 Common Toxicity Criteria for Adverse Effects (v4.03) were encountered in 10 (47.6%) and one (4.8%) patients, respectively. ConclusionThis preliminary findings of COSIT can be a promising alternative treatment for patients having large HCC. Consequently, a multicenter stage 2b Exploration IDEAL trial is suggested.

Leveraging hydrogen as the low reactive component in the optimization of the PPCI-RCCI transition regimes in an existing diesel engine under varying injection phasing and reactivity stratification strategies

This research illustrates the novel interposed zone of partially premixed and reactivity-controlled combustion in conjunction with injection phasing and reactivity phasing strategies to understand the performance emission and stability characteristics of a single-cylinder common rail direct injection diesel engine. However, this study determined the optimum interposed zone of operation using Response Surface Methodology (RSM). The findings indicate that raising the rate of hydrogen induction enhances the stability of interposed zone of combustion. The interposed optimum regime has a 31.58% exergy efficiency and 99.1% desirability. Compared to the similar trial run, the optimization study revealed a 45.09% reduction in Soot, a 14.29% reduction in total unburnt hydrocarbon (TUHC), and a 39.83% reduction in NOx emission levels. Thus, experimental and predicted values have been compared. Hence, this variable injection and reactivity phasing under hydrogen enrichment strategies are feasible enough to achieve the goals of advanced low-temperature combustion (LTC) concepts in an existing diesel engine without making significant design modifications.

An estimation method of the fuel mass injected in large injections in Common-Rail diesel engines based on system identification using artificial neural network

An innovative method that is capable of evaluating the fuel mass of large injections (greater than 6 mg/shot) in real time is developed for passenger car Common-Rail injection systems, with the aim to reduce emissions and improve power performance. The proposed method requires only one additional pressure transducer installed on the rail-to-injector pipe, and its overall accuracy is within 1.4 mg.The feasibility of the estimation method is analyzed based on the characteristic curve theory, during the hydraulic injection phase, the fluid properties along the rail-to-injector pipe can be approximated based on a single signal, such as the pressure or the flow velocity, measured at the rail-to-injector tube downstream.Based on system identification using artificial neural network and physical equations, the pressure time distribution in the vicinity of the injector inlet is used as input to identify the pipe-passed fuel mass. This derived fuel quantities are verified to be well correlated with the measured injected mass in large injections under a wide range of working conditions. This estimation tool can be installed on a diesel engine with the relations implemented in the electronic control unit, allowing a more accurate evaluation of the injected fuel mass in real time.

Well Integrity Study for CO_2 WAG Application in Mature Field X, South Sumatra Area for the Fulfillment as CO2 Sequestration Sink

The most of today's global oil production comes from mature fields. Oil companies and governments are both concerned about increasing oil recovery from aging resources. To maintain oil production, the mature field must apply the Enhanced Oil Recovery method. water-alternating-gas (WAG) injection is an enhanced oil recovery method designed to improve sweep efficiency during injection with the injected water to control the mobility of . This study will discuss possible corrosion during and water injection and the casing load calculation along with the production tubing during the injection phase. The following study also performed a suitable material selection for the best performance injection. This research was conducted by evaluating casing integrity for simulate water-alternating-gas (WAG) to be applied in the X-well in the Y-field, South Sumatra, Indonesia. Corrosion prediction were performed using Electronic Corrosion Engineer (ECE®) corrosion model and for the strength of tubing which included burst, collapse, and tension of production casing was assessed using Microsoft Excel. This study concluded that for the casing load calculation results in 600 psi of burst pressure, collapse pressure of 2,555.64 psi, and tension of 190,528 lbf. All of these results are still following the K-55 production casing rating. While injecting , the maximum corrosion rate occurs. It has a maximum corrosion rate of 2.02 mm/year and a minimum corrosion rate of 0.36 mm/year. With this value, it is above NORSOK Standard M-001 which is 2 mm/year and needs to be evaluated to prevent the rate to remain stable and not decrease in the following years. To prevent the effect of maximum corrosion rate, the casing material must use a SM13CR (Martensitic Stainless Steel) which is not sour service material.

Research on drivability control in P2.5 hybrid system

The control of drivability in this paper contains the clutch start, the engine and motor anti-jerk control during tip in and tip out. First, the fast clutch start is divided into five phases as well as the smooth clutch start: the gear selection phase, the drag phase, the reduction phase, the injection phase and the gear engage phase. To avoid the jerk caused by the torque loss during the drag phase, the motor torque is defined to reserve in pure electric drive condition and to compensate the clutch torque. Second, the engine fast torque and slow torque anti-jerk control which contains enable conditions and torque ramp control based on overall wheel torque before filtering are presented. Third, the motor lash detection, brake detection, and anti-jerk control are introduced. Finally, the real vehicle tests are performed to show that the drivability system can greatly improve the driver’s comfort and reduce jerk during the clutch start, tip in and tip out process successfully. The fast clutch start time is reduced from 1.27s to 0.56s compared to the smooth clutch start. The smooth clutch start acceleration speed is reduced from 2.9 m/s^2 to 1.5 m/s^2 compared to the fast clutch start. The engine torque after filtering control during full acceleration changes from -0.6 m/s^2 to 1.8 m/s^2 and the motor torque after filtering control during 50% acceleration changes from 1.8 m/s^2 to -0.07 m/s^2 without obvious jerk.

Hybrid physics and data-driven modeling for unconventional field development and its application to US onshore basin

The objective of this study is to develop a hybrid model by combining physics and data-driven approach for optimum unconventional field development. We used physics-based reservoir simulations to generate training datasets. These uncalibrated priors were incorporated into data-driven machine learning (ML) algorithms so that the algorithms can learn the underlying physics between reservoir simulation input and output, cumulative oil production for parent and child wells. The reservoir simulations in a single half-cluster model consists of injection and production phases. This allows the algorithm to relate the impact of completion design, well spacing and timing to the production profiles. After performing a sensitivity analysis to reduce the number of training inputs, more than 20,000 simulations results were generated as the training data. The best accuracy, R2 = 0.94, was achieved with the neural network model after tuning hyper-parameters. Then, we incorporated the hybrid model with the genetic algorithm to perform efficient history matching to calibrate model parameters and predict estimated ultimate recovery (EUR) and net present value with 10% discount rate (NPV10). The great efficiency in the hybrid model takes only several minutes to complete a single well history matching. The calibrated model shows that the prediction from the hybrid model is physically meaningful compared to actual reservoir simulations, capturing the impact of fracture geometry, child well spacing and timing on the well production. With multiple history matching results, we populated value acreage maps (e.g., EUR and NPV10) which can benefit the unconventional field development planning. Lastly, a blind test was conducted in an area of interest to demonstrate that the proposed workflow can effectively predict a well performance in the area without sufficient data, utilizing calibrated model parameters from history matched results of adjacent wells. The proposed model can provide quick and scalable solutions that honor underlying physics to help decision making on unconventional field development based on production profile and economic metrics with various completion designs.

Effects of temperature and CO2/Brine cycles on CO2 drainage endpoint phase mobility – implications for CO2 injectivity in deep saline aquifers

The coupled process of (seasonal) CO2 downhole temperature cycles and natural CO2/brine drainage-imbibition cycles is an inherent feature of large-scale CO2 injection schemes during the injection phase of a geologic storage site. Analysis of long-term field injection data shows that the effect of temperature cycles on injectivity is significant and cannot be explained by changes in CO2 properties alone, raising the question of whether CO2-rock properties such as relative permeability are also changing. We present the results of lab-scale coreflood experiments designed to measure CO2 drainage endpoint phase mobilities and relative permeabilities for cyclic CO2 displacing brine at representative reservoir drainage pressure/temperature conditions, using Basal Cambrian Sandstone (BCS) core samples from the storage reservoir of a large-scale (>1Mtpa) CO2 injection scheme in operation. The isothermal experiments are conducted at three temperatures: average seasonal low, average seasonal high, and reservoir. The measurements also incorporate the effects of repeated saturation cycles (or saturation hysteresis), between ∼100% brine saturation and irreducible brine saturation for the same core sample for up to 12 repetitive drainage-imbibition cycles. The results show that the CO2/brine two-phase flow characteristics change after each flooding cycle. CO2 drainage endpoint phase mobility increases as temperature increases, but the mobility increases cannot be fully explained by the decrease in CO2 viscosity and rock permeability changes alone. CO2 endpoint relative permeability (measured at about 0.20 ± 0.1) contributes marginally to the CO2 phase mobility changes with temperature and exhibits a weak inconsistent dependency on temperature. Field scale injectivity of CO2 can be optimised in large-scale CCS injection schemes design by exploiting the CO2 temperature-CO2/brine cycling-phase mobility functional relationship where CO2 phase mobility is enhanced at higher CO2 downhole temperatures. Field data show that this effect, though significant, may be weakened or even overridden by other temperature-dependent phenomena.

Preliminary evaluation of a natural surfactant extracted from Myrtus communis plant for enhancing oil recovery from carbonate oil reservoirs

Surfactants are among the materials used to improve water properties for injection into oil reservoirs, and reduce injection phase and crude oil interfacial tension (IFT). Recently, the interest in the use of natural surfactants has increased and is constantly on the rise to solve some challenges of using chemical surfactants such as incompatibility with the environment and the high cost. In this study, we have used aqueous extract of powdered leaf of Myrtus communis as an available source of natural surfactant. The extracted surfactant was characterized by TGA, 1H NMR and FTIR techniques. The surfactant efficiency was demonstrated by performing some experiments including IFT and injection of chemical slug and surfactant into carbonate plugs. The surfactant adsorption on carbonate rock was also studied. It was observed that this natural surfactant can reduce IFT to 0.861 mN/m at surfactant critical micelle concentration (CMC) of 5000 ppm. This minimum IFT was further reduced at optimum salinity and alkali. Finally, an increase of 14.3% oil recovery by surfactant flooding and 16.4% oil recovery by ASP slug injection containing NaOH alkali and partially hydrolyzed polyacrylamide (PHPA) polymer with 0.5 PV volume from carbonate plugs was achieved.

Comparative LCA of conventional manufacturing vs. additive manufacturing: the case of injection moulding for recycled polymers

ABSTRACT Additive Manufacturing helps to develop production alternatives with new technologies and less environmental impacts. The comparative analysis was performed between two manufacturing processes using black recycled Acrylonitrile Butadiene Styrene (ABS) pellets to evaluate the potential environmental impacts between Injection moulding and Fused Deposition Modelling (FDM). The Life Cycle Assessment (LCA) and the Unit Process Life Cycle Inventory (UPLCI) methodology were adopted, which resulted in an impact assessment separated by operation modes and subunits of the equipment. The LCA results indicate a lower environmental impact of the FDM when the aim is to produce a batch size smaller than 14 parts. For batch sizes above 50 parts, the Injection moulding process generated less impact to the Global Warming Potential (GWP) and Cumulative Energy Demand (CED). The printing stage contributed the most to generating impacts for the FDM. In the Injection moulding process, the main responsible for generating impacts were the injection phase. Mechanical tensile tests were carried out with the parts obtained by the FDM with different infills (25%, 50%, 75% and 100%), and it was observed that parts with 100% infill obtained the best relation between mechanical properties and environmental impacts.

Quantitative accuracy in total-body imaging using the uEXPLORER PET/CT scanner

Absolute quantification of regional tissue concentration of radioactivity in positron emission tomography (PET) is a critical parameter-of-interest across various clinical and research applications and is affected by a complex interplay of factors including scanner calibration, data corrections, and image reconstruction. The emergence of long axial field-of-view (FOV) PET systems widens the dynamic range accessible to PET and creates new opportunities in reducing scan time and radiation dose, delayed or low radioactivity imaging, as well as kinetic modeling of the entire human. However, these imaging regimes impose challenging conditions for accurate quantification due to constraints from image reconstruction, low count conditions, as well as large and rapidly changing radioactivity distribution across a large axial FOV. We comprehensively evaluated the quantitative accuracy of the uEXPLORER total-body scanner in conditions that encompass existing and potential imaging applications (such as dynamic imaging and ultralow-dose imaging) using a set of total-body specific phantom and human measurements. Through these evaluations we demonstrated a relative count rate accuracy of ±3%–4% using the NEMA NU 2-2018 protocol, an axial uniformity spread of ±3% across the central 90% axial FOV, and a 3% activity bias spread from 17 to 474 MBq 18F-FDG in a 210 cm long cylindrical phantom. Region-of-interest quantification spread of 1% was found by simultaneously scanning three NEMA NU 2 image quality phantoms, as well as relatively stable volume-of-interest quantification across 0.2%–100% of total counts through re-sampled datasets. In addition, an activity bias spread of −2% to +1% post-bolus injections in human subjects was found. Larger bias changes during the bolus injection phase in humans indicated the difficulty in providing accurate PET data corrections for complex activity distributions across a large dynamic range. Our results overall indicated that the quantitative performance achieved with the uEXPLORER scanner was uniform across the axial FOV and provided the accuracy necessary to support a wide range of imaging applications.

Study on the Stability of Antibiotics, Pesticides and Drugs in Water by Using a Straightforward Procedure Applying HPLC-Mass Spectrometric Determination for Analytical Purposes

The stability of analytes is a critical point in chemical analysis, especially in the field of trace levels residue analysis. Nowadays, due to advances in analytical technology and in separation sciences, the analyses of water have been improved. Unfortunately, in this context, one of the most critical issues in water analysis include compound stability from sampling station to laboratory procedures. This study was carried out to explore the stability of several compounds in water from sampling to analysis concerning analytes reported in implementing decision 2018/840—Watch List. During method development and validation, the stability of compounds was investigated to detect the best operating conditions concerning sampling, extraction and analysis. In this paper, we report a study on the stability of antibiotics, pesticides and drugs in water determined using a straight-forward procedure applying mass spectrometric detection for analytical purposes. The laboratory tests were performed in Milli-Q water and surface water by analyzing samples through direct injection, solvent mixture (Water/ACN) and solid phase extraction system from time 0 to 168 h. All the analytes of the WL are stable in aqueous solutions with the addition of at least 25% ACN even after 168 h, and the analytes have shown a matrix effect on recovery of some analytes such as Famoxadone from sampling results (recovery in surface water 72%). For all the analytes investigated, recoveries were between 70 and 130% by using SPE procedures before UHPLC-MS/MS analysis, which is in good agreement with method validation procedures.

Mobility of nZVI in a Reconstructed Porous Media Monitored by an Image Analysis Procedure

Zero-valent iron nanoparticle (nZVI) technology has been found to be promising and effective for the remediation of soils or groundwater. However, while nanoparticles are traveling through porous media, they can rapidly aggregate, causing their settling and deposition. When nZVI are injected in the groundwater flow, the behavior (mobility, dispersion, distribution) is unknown in groundwater, causing the use of enormous quantities of them if used at the field scale. In this paper, a laboratory experiment was carried out with groundwater flow in a two-dimensional, laboratory-scale tank to assess the nanoparticle behavior by means of an image analysis procedure. A solution of zero-valent iron nanoparticles, Nanofer 25S particles, were used and glass beads were utilized as porous medium. The laboratory experiment included the use of a digital camera for the acquisition of the images. The image analysis procedure was used to assess the behavior of nZVI plume. A calibration procedure and a mass balance were applied to validate the proposed image analysis procedure, with the hypothesis that nanoparticles would be uniformly distributed in the third dimension of the tank (thickness). The results show that the nanoparticles presented small dispersive effects and the motion was strongly influenced from the higher weight of them with respect to the water. Therefore, the results indicate that nanoparticles have an own motion not strongly influenced by the fluid flow but more determined from the injection phase and gravity. The statistical elaborations show that the nZVI plume did not respond to the classical mechanisms of the dispersion.

Participation of the descending noradrenergic inhibitory system in the anti-hyperalgesic effect of acetaminophen in a rat model of inflammation

AimsThis study investigated the relationship between the analgesic efficacy of acetaminophen and the descending noradrenergic systems using rodent models of inflammatory pain. Main MethodsInflammatory pain models were established by carrageenan injection into rats' paws. The models were defined as acute (4 h after carrageenan injection), subacute (24 h after carrageenan injection), and late (1 week after carrageenan injection) phase. To evaluate intravenous acetaminophen treatment, the withdrawal threshold to mechanical stimuli was assessed simultaneously with in vivo microdialysis assay of noradrenaline levels in the locus coeruleus (LC). Further analyses were performed to observe the effect of yohimbine on the treatment and the impact of AM404 treatment, a metabolite of acetaminophen, on noradrenaline levels in the LC. Key findingsIn all phases, intravenous acetaminophen had a significant anti-hyperalgesic effect (p < 0.05). There was a significant time-dependent increase in the noradrenaline concentration within the LC (acetaminophen versus saline treatment; at 30 min, p < 0.001; 60 min, p < 0.01) in the subacute pain model, but not in the acute and late phase pain models. Intrathecal pre-injection of yohimbine attenuated the anti-hyperalgesic effect after acetaminophen injection only in the subacute model (p < 0.05). In the subacute pain model, intracerebroventricular administration of AM404 showed the same trend in noradrenaline levels as acetaminophen administration (AM404 versus vehicle group at 30 min, p < 0.001). SignificanceWe found the descending noradrenergic inhibitory system is involved in the antinociceptive action of acetaminophen in the subacute phase of inflammatory pain.

Modeling of fluid-induced seismicity during injection and after shut-in

We develop a fully coupled hydro-mechanical model to simulate fault slip due to fluid injection. We consider the interaction between a hydraulic fracture and pre-existing faults as well as the fluid exchange between the fracture/fault and the porous matrix. In order to consider a pressure diffusion mechanism, we set a relatively high permeability around the stimulated path. Our parametric study shows that a couple of factors affect the fault activation and its slip behavior such as fault properties, friction properties and injection scenario. We observe that pore pressure diffusion induces poroelastic stress change, which are able to produce shut-in events with a time and space lag. This mechanism also affects the slip behavior during injection in particular when the surrounding permeability is high (e.g., up to 1e-13 m2/s), and provides a new insight into understanding the occurrence of stronger seismic events after shut-in compared to the injection phase. In addition, we show that small perturbations may trigger large seismic fault slip which highlights the key role of the initial fault stress state. The results have profound implications for deep fluid injection related engineering as well as for soft cyclic injection strategies aiming to mitigate the risk of large earthquakes.

Integration of Borehole Image and Sonic to Evaluate Critically-Stressed Fractures to Optimize Production at FORGE Geothermal Field

Geothermal integration solutions as unconventional environment have workflows or methods that must be able to optimize existing data and be adapted to overcome existing challenges. The integration method consists of geology, Petrophysics and Geomechanics domains. Geological analysis to identify fractures, fracture classification, knowing the dip azimuth and the magnitude of the fracture, quantitative analysis (intensity, aperture and porosity) by using the wellbore image log. Petrophysics analysis is to distinguish open / healed fractures that analysed from sonic data. Fracture orientation analysed further for the stress calculation on fracture planes and to determine the effective fractures (most likely to flow) that has a high ratio of shear to normal stress. Geomechanical analysis in geothermal fields, among others, is to determine the dynamic permeability behaviour of fractures during the production / injection phase, determine the orientation and productive fracture interval. The integration is using FORGE well 21-31 in 8.5in section with depth interval 6,226 – 7,920 ft-MD and well 58-32 in 8.5in section with depth interval 7,390-7,527 ft-MD. Well 21-31 shows dominant fracture strike orientation to NNE-SSW, while Well 58-32 shows slightly different set strike orientation to N-S with minor striking to NE-SW and NW-SE. Evaluation of critically stressed fracture intended to have knowledge on production mechanism and based on analysis, fracture/fault that has high potential of shearing is striking to NNE-SSW and dipping to Westerly.

Large-eddy simulation of a multi-injection flame in a diesel engine environment using an unsteady flamelet/progress variable approach

In this work, large-eddy simulations (LESs) are conducted for a multiple-injection flame in a diesel engine environment using an unsteady flamelet/progress variable (UFPV) approach in which differential diffusion is considered. The suitability of the UFPV tabulation approach is first evaluated through a priori analyses using the state-of-the-art direct numerical simulation (DNS) dataset. Both the instantaneous data and the conditional values for the major and minor species' mass fractions are compared between the UFPV and the DNS. The comparisons show that the proposed UFPV tabulation approach can give good predictions for the multiple-injection flame at different injection phases. While the gas temperature and major species mass fractions can be accurately predicted with or without differential diffusion being considered in the UFPV flamelet library, the prediction accuracy for the highly diffusive species (e.g., hydrogen) in the main injection phase can be noticeably improved when differential diffusion is taken into account. The fully coupled LES/UFPV simulations show that the overall structure of the multiple-injection flame can be predicted, and the conditional thermo-chemical values are close to the filtered DNS dataset. The reasons for the remaining discrepancies found in the a priori analyses and the a posteriori simulations using the UFPV approach are analyzed.

Role of pre-ionization in NBI plasma start-up of Heliotron J using non-resonant microwave heating

Here, we report on role of pre-ionization using non-resonant 2.45 GHz microwave heating (P 2.45 GHz < 20 kW) in plasma start-up of neutral beam injection (NBI) for heliotron configurations in low beam power (P NB) under non-resonant heating condition. A rapid electron heating towards burn-through of the low-Z impurities was observed experimentally in the early phase of beam injection when the seed plasma density produced by the non-resonant heating was enough for the plasma start-up. Beam heating time to the burn-through increased with decreasing the seed plasma density and a critical density condition of the seed plasma for successful start-up was observed experimentally. Proper timing of the gas fuelling is critical for plasma expansion because the beam fuelling is not significant. A 0-dimensional (0D) model analysis of the NBI start-up developed in this study well reproduces the experimental results. The 0D model clarifies the physical mechanism of the NBI start-up using pre-ionization described as follows: (1) the seed plasma produces sufficient beam ions immediately after beam injection, (2) the beam ions heat up electrons that promote the ionization/dissociation of the background neutrals, (3) this process acts as a positive feedback loop resulting in further electron heating towards burn-through. The 0D model analysis shows that the critical density corresponds to the state at which the electron heating by the beam ions is equal to electron power loss due to conduction and ionization/dissociation.