Chamber Wall Research Articles

Power-Law Nanofluid Magnetohydrodynamics Combined Convection in the Presence of Heat Absorption/Generation: A Lattice Boltzmann Analysis to Compute Thermal Performance Index

Endeavors to improve the performance of thermal systems have always been of great noticed due to their extremely high importance in industrial and engineering applications. For this intention, in the existing simulation, several effective strategies have been evaluated to determine the amount of heat transfer and entropy formation caused by the combined convection of non-Newtonian nanofluid with particles Brownian motion. Based on the findings via LBM simulation, it has been observed that changing the position and speed direction on the chamber wall helps to control the flow characteristics, and thus significantly changes the thermal performance of the system. The least effect of the magnetic field in reducing the value of the Nusselt number in all the positions of applying the speed belongs to the state where the wall direction is aligned with the force of gravity. In the case where the middle part of the vertical wall has speed, the formed flow power inside the chamber is 29% and 45% higher than when the first third and the last third of the wall have speed. The presence of a strong magnetic field leads to the reduction of convection effects, which is more evident for moving up the vertical wall. When the middle part of the wall has speed, if the magnetic field is applied to the middle part of the chamber to the highest value, the reduction of the average Nusselt number is about 35% and 39% more than the case when the magnetic field is applied to the first third and the last third of chamber. To have a higher average Nusselt number value, reducing the fluid power-law index and enhancing the Reynolds number value are effective strategies. To control the effects of the magnetic field, it is very effective to reduce the shear force on the chamber wall and expose the fluid flow to the heat absorption/production phenomenon. By reducing the value of fluid power-law index, the effect of magnetic field and heat absorption/production becomes more evident. In Re=200, the reduction of the thermal performance index for enhancing the Hartmann number value to the highest value is about 39% for n = 0.45, while this effect is about 31% and 24% for n = 0.7 and n = 0.95, respectively. By exposing the current to heat production, the effect of the magnetic field is reported to be about 55% higher than in other cases. Although heat production enhances the amount of Be value by about 66% compared to the heat absorption mode, it leads to an increase in the thermal performance index. The highest value of the system thermal performance index (0.82) can be achieved by upward moving the middle part of the chamber wall in the absence of magnetic field for heat absorption mode at the lowest power-law index and the highest Reynolds number value.

Sample heating above 1400 K in a diamond anvil cell

In high-pressure experimental methods, sample heating in the pressure chamber of a diamond anvil cell is an important topic, and numerous efforts have been made to improve and develop new technologies. In this paper, we propose a new type of internal resistance heating technique, the composite heating gasket, prepared by integrating an annular heater into the sample chamber for direct heating of the sample. As the effective heating area covers the entire pressure chamber wall, a relatively quasi-uniform temperature field is formed within the sample chamber. At the same time, the integration design reduces the risk of diamond oxidation and enables direct measurement of the spectroscopic properties of samples at high temperatures. The preparation of the composite heating gasket is simple and repeatable, and its heating performance is stable at temperatures above 1400 K. When the sample diameter is 210 μm and no thermal insulation is used, the diameter of the temperature zone in which the temperature difference is less than 10 and 20 K exceeds 120 and 170 μm, respectively. The composite heating gasket represents a significant advancement in providing a uniform temperature field for in situ measurements with diamond anvil cells at high pressure and temperature.

Quantity and diameter of dentinal tubules of human teeth and teeth of experimental animals according to scanning electron microscopy data

Insight into the interrelation between the structure and mechanical properties of dentin of a tooth is crucial for prevention and treatment of oral cavity diseases. The study of the structure of dental dentin is important for understanding the pathogenetic mechanisms of the spread of cariogenic microflora in progressive dental caries to the pulp and periodontium, as well as for the interpretation of the results of studies of dental dentin-adhesive materials. The in vitro research presented here involved the examination of coronal dentin in 46 intact teeth from rats, cats, dogs, and humans at various distances from the pulp chamber, with a focus on the quantity and diameter of dentinal tubules. The calculations were based on the analysis of 155 scanning electron microscope photographs of the enamel surface and pulp chamber wall. The researchers calculated the quantity and diameter of dentinal tubules per unit area, which they measured at various distances from the pulp chamber. It was found that dentinal tubules are the widest near the pulp chamber wall, where the average diameter ranged from 1.7 to 2.8 µm. The highest values were found in premolars of young humans and the lowest - in the incisors of rats. In the middle portion of the dentin, the diameter of dentinal tubules ranged from 1.0 to 13.3 µm, while at the periphery, it was 0.6–0.9 µm. The highest density of dentinal tubules per unit area was found closest to the pulp horn, and the lowest was in the enamel region. Near the pulp chamber wall, the average density of dentinal tubules ranged from 50 000 to 90 000/mm², in the middle of the dentin, it ranged from 37 000 to 50 000/mm², and at the periphery, it ranged from 10 000 to 25 000/mm². All examined teeth exhibited straight dentinal tubules, except for the rats’ incisors, which showed local irregularities. A comparison was made based on the quantity and width of dentinal tubules in the examined animals and humans.

Enhancing the Yield of a Lab-on-a-Disk-Based Single-Image Parasite Quantification Device.

The recently proposed single-image parasite quantification (SIMPAQ) platform based on a Lab-on-a-Disc (LOD) device was previously successfully tested in field conditions, demonstrating its efficiency in soil-transmitted helminth (STH) egg detection and analysis on the level delivered by the current state-of-the-art methods. Furthermore, the SIMPAQ provides relatively quick diagnostics and requires small amounts of sample and materials. On the other hand, in a recent related study, it was revealed that the performance of the SIMPAQ method can be limited due to the action of the tangential Euler and Coriolis forces, and the interaction of the moving eggs with the walls of the LOD chamber. Here, we propose a new improved design that allows us to overcome these limitations and enhance the yield of the SIMPAQ LOD device, as demonstrated in experiments with a synthetic particle model system and real parasite eggs. Despite the simplicity, the proposed design modification is demonstrated to allow a substantial improvement in the yield of the SIMPAQ device, i.e., above 90% of parasite eggs and 98% of synthetic model particles were transported to the field of view. The new design proposed here will be further examined in the new generation of SIMPAQ devices within ongoing research on STH egg detection in field conditions.

A novel perfusion bioreactor promotes the expansion of pluripotent stem cells in a 3D-bioprinted tissue chamber

While the field of tissue engineering has progressed rapidly with the advent of 3D bioprinting and human induced pluripotent stem cells (hiPSCs), impact is limited by a lack of functional, thick tissues. One way around this limitation is to 3D bioprint tissues laden with hiPSCs. In this way, the iPSCs can proliferate to populate the thick tissue mass prior to parenchymal cell specification. Here we design a perfusion bioreactor for an hiPSC-laden, 3D-bioprinted chamber with the goal of proliferating the hiPSCs throughout the structure prior to differentiation to generate a thick tissue model. The bioreactor, fabricated with digital light projection, was optimized to perfuse the interior of the hydrogel chamber without leaks and to provide fluid flow around the exterior as well, maximizing nutrient delivery throughout the chamber wall. After 7 days of culture, we found that intermittent perfusion (15 s every 15 min) at 3 ml min−1 provides a 1.9-fold increase in the density of stem cell colonies in the engineered tissue relative to analogous chambers cultured under static conditions. We also observed a more uniform distribution of colonies within the tissue wall of perfused structures relative to static controls, reflecting a homogeneous distribution of nutrients from the culture media. hiPSCs remained pluripotent and proliferative with application of fluid flow, which generated wall shear stresses averaging ∼1.0 dyn cm−2. Overall, these promising outcomes following perfusion of a stem cell-laden hydrogel support the production of multiple tissue types with improved thickness, and therefore increased function and utility.

Abstract 19192: Deciphering the Cardioprotective Role of Ufm1 Modification in Cardiac Remodeling

UFM1 (ubiquitin-fold modifier 1) is a novel Ub-like protein that covalently modifies protein substrates via a highly conserved E1 (UBA5)-E2 (UFC1)-E3 (UFL1) enzymatic cascade. UFM1 modification (ufmylation) controls multiple pathophysiological events and is implicated in various human diseases. However, the significance of ufmylation in cardiac health remains poorly understood. We have previously reported that ufmylation is upregulated in compensated, hypertrophic mouse hearts but decreased in failing human hearts. Inhibition of ufmylation by targeted ablation of the E3 UFM1 ligase 1 (UFL1) in mouse hearts resulted in dilated cardiomyopathy under baseline and stress conditions. Targeted deletion of a putative UFM1 target, UFBP1, also evokes endoplasmic reticulum (ER) stress, leading to dilated cardiomyopathy While these exciting data reveal the pivotal role of ufmylation in the maintenance of ER/cardiac homeostasis, it remains unclear whether ufmylation of cardiac proteins is required for heart function and if so, how ufmylation regulates cardiac function. To determine the role of UFM1 modification in cardiomyocytes we have generated cardiac specific UFM1 CKO mice. The UFM1 CKO mice developed dilated cardiomyopathy at resting condition, as indicated by left ventricle (LV) wall thinning, chamber dilatation and impaired contractility at 4 months of age, which were further exacerbated by 6 months. To test the hypothesis that UFM1 protects the heart by modifying cardiac proteins we replenished UFM1-deficient mice with WT and conjugation deficient UFM1 via AAV9. Restoration of WT-UFM1 expression, but not the conjugation-deficient mutant, attenuated cardiac dysfunction of UFM1CKO hearts. It appears that UFM1 modification constraints pathological cardiac remodeling by maintaining ER homeostasis. Taken together, our data show that Ufmylation is a critical post-translational modification that regulates cardiac homeostasis.

Abstract 14766: Acute Impact of Transapical Ventricular Reshaping Device on Dilated Left Ventricle With Functional Mitral Regurgitation in Swine Model

Introduction: Functional mitral regurgitation (FMR) after myocardial infarction (MI) exacerbates morbidity and mortality. Correcting FMR plays a critical role in mitigating or reversing ventricular remodeling in MI patients with FMR. However, the COAPT trial demonstrated that FMR correction yields favorable results in smaller left ventricles (LVs) but not in severely dilated LVs. In this study, we evaluated the efficacy of a transapical device in MI swine model with FMR, which can perform papillary muscle approximation (PMA) and simultaneous reduction of LV volume. Methods: Yorkshire pig (n=15) were used in this study. MI was induced by percutaneous occlusion of the left circumflex artery, which caused LV dilatation and FMR by 3 months. The device was implanted through the LV apex to achieve PMA and LV reshaping until FMR was eliminated (Figure A). The immediate effects of the device implantation on the mitral valve and the LV were assessed using echocardiography and pressure-volume loops. Results: The device implantation decreased inter-papillary muscle distance from 24.5±3.8mm to 16.7±3.8mm (p<0.0001), and significantly reduced FMR. Coaptation length significantly increased from 3.4±0.7mm to 5.5±1.2mm (p<0.0001). End-diastolic volume decreased from 153±48ml to 117±33ml, a 23.5% reduction (p=0.0004). The end-systolic pressure-volume relationship and preload adjusted dP/dt max significantly increased after the device implant, indicating an improvement of LV contractility. There were no differences observed in Tau and end-diastolic pressure-volume relationship, depicting minimal acute impact on diastolic ventricular function after device implantation (Figure B and C). Conclusions: This transapical reshaping device effectively corrects FMR in very enlarged LVs, but also reduces systolic chamber wall stress by reducing the LV volume. An acute improvement in LV systolic function was observed, potentially indicating a therapeutic effect.

Numerical simulation of fatigue crack growth in an engine heat shield

In order to prevent the body from overheating, a corresponding thermal protection device is usually designed on the inner wall of the combustion chamber. The working environment of this thermal protection device is very harsh, and it needs to withstand internal and external pressure loads and thermal radiation loads of the combustion chamber, especially at the connection between the cylinder and the support parts, the force is harsher. In order to avoid engine damage, causing unnecessary losses. In this article, the thermal–mechanical coupling analysis of the heat shield is carried out by finite element method to analyze the thermal stress and mechanical stress. According to the finite element simulation results, the initial cracks are inserted, respectively, at the stress concentration. Using linear elastic fracture mechanics and Forman–Newman–de Koning models, the crack growth lifetimes of cracks at different locations were calculated. The results of the study show that comparing the initial cracks at different locations, the cracks on the side near the edge of the heat shield have the largest reduction in crack growth life of 64.4% and the critical crack length of 52.0%. The linear superposition of thermal and mechanical stresses under different working conditions has different degrees of nonlinear effects on the crack growth life and critical crack length. The research work in this article can provide a basis for the evaluation of fatigue crack growth life of heat shield and can also provide a reference for engine maintenance.

Kinetic simulation of ion thruster plume neutralization in a vacuum chamber

The electrical environment of a ground vacuum testing chamber creates facility effects for gridded ion thrusters. For example, it is well known that the plume from the thruster generates current paths that are very different from what occurs in space, and the neutralization of this plume is also different. For reasons such as this, it is important to clarify how the experimental testing environment affects plasma flows, but understanding this effect solely through ground experiments is difficult. To that end, this study utilizes particle-in-cell and direct simulation Monte Carlo methods to simulate xenon beam ions and electrons emitted from a neutralizer. First, we compare simulations conducted within the chamber to those conducted in space, demonstrating that grounded chamber walls increase the electric potential and electron temperature. Next, we investigate the impact of the neutralizer’s position and the background pressure on the plume in the vacuum chamber. We find that as the neutralizer position moves closer to the location of maximum potential, more electrons are extracted, resulting in increased neutralization of the plume. We also observe that high background pressure generates slow charge-exchange ions, creating ion sheaths on the side walls that alter ion current paths. Finally, we discuss how the potential at the thruster and neutralizer exits affects the plume. The relative potential of the neutralizer to the vacuum chamber wall is observed to significantly influence the behavior of the electrons, thereby altering the degree of plume neutralization. These findings are shown to be consistent with experimental results in the literature and demonstrate the promise of high-performance simulation.

Magnetic field properties in non-axisymmetric divertors

Stellarator power plants require a plan for the removal of the particles and the heat that are exhausted across the plasma edge. Unless a flowing liquid metal can be used to carry the helium exhaust to places where it can be removed from the plasma chamber, the particle exhaust must be magnetically diverted into pumping chambers. Studies are required to determine how magnetic features relate to the required divertor properties, how these magnetic features can be produced, and how they can be controlled. General studies are clarified and simplified by the use of the magnetic field line Hamiltonian ψp(ψ,θ,φ) and a vector x→(ψ,θ,φ) that gives the point in space associated with each point in the (ψ,θ,φ) canonical coordinates, a flux and two angles. The non-resonant Fourier terms in ψp can be removed by a canonical transformation, so only resonant Fourier terms can determine the field line properties in the plasma edge and divertor. This paper discusses the important divertor properties and explains how ψp(ψ,θ,φ) and x→(ψ,θ,φ) can be obtained numerically in a special form for any stellarator magnetic field, B→(x→). This form holds between an arbitrary magnetic surface and the chamber walls with the non-resonant terms eliminated. Studies based on variations in the terms in such derived field-line Hamiltonians can determine what magnetic features are mathematically possible and how they could be produced and controlled by the external magnetic field coils.

Research on the deposition and properties characterization of novel conductive getter films on the inner wall of accelerator vacuum chamber

The new generation diffraction-limited storage ring has small vacuum chamber apertures, resulting in a distributed vacuum problem. Depositing a Ti-Zr-V NEG film layer on the inner face of vacuum chambers is an ideal solution for resolving the non-uniform vacuum distribution problem. However, Ti-Zr-V NEG coatings on the surface of the vacuum chamber increase its surface resistivity, which can intensify the wakefield impedance effect. This article proposes adding conductive Ag to the Ti-Zr-V NEG film. A novel Ti-Zr-V-Ag NEG film not only has good vacuum performance, but also has good conductivity. Ti-Zr-V-Ag NEG film is successfully prepared by magnetron sputtering. The activation kinetic processes and surface resistivity of Ti-Zr-V-Ag and Ti-Zr-V NEG films are detected in detail, and comparative research on the activation behavior and surface resistivity of Ti-Zr-V-Ag films deposited with various sputtering pressures is investigated. The results show that adding pure metallic silver to the Ti-Zr-V film effectively decreases the DC resistivity of the NEG films, and this reduction can be further enhanced by reducing the sputtering pressure. The activation kinetics behavior of the Ti-Zr-V-Ag film shows minor degradation compared with that of the Ti-Zr-V film.

On matching a microwave radiation with the plasma of an electron cyclotron resonance discharge

This article proposes a scheme for matching microwave radiation with a magnetized plasma of an electron cyclotron resonance (ECR) discharge in an open magnetic trap, using the effect of depolarization—the transformation of the ordinary wave into the extraordinary one upon reflection from the metal walls of a plasma chamber. An analysis of the efficiency of such a transformation is carried out, and it is shown that for grazing (less than 15° with metal surface) angles of incidence; it is possible to achieve an efficiency exceeding 90%.

Deep Learning–Enabled Assessment of Left Heart Structure and Function Predicts Cardiovascular Outcomes

BackgroundDeep learning interpretation of echocardiographic images may facilitate automated assessment of cardiac structure and function. ObjectivesWe developed a deep learning model to interpret echocardiograms and examined the association of deep learning–derived echocardiographic measures with incident outcomes. MethodsWe trained and validated a 3-dimensional convolutional neural network model for echocardiographic view classification and quantification of left atrial dimension, left ventricular wall thickness, chamber diameter, and ejection fraction. The training sample comprised 64,028 echocardiograms (n = 27,135) from a retrospective multi-institutional ambulatory cardiology electronic health record sample. Validation was performed in a separate longitudinal primary care sample and an external health care system data set. Cox models evaluated the association of model-derived left heart measures with incident outcomes. ResultsDeep learning discriminated echocardiographic views (area under the receiver operating curve >0.97 for parasternal long axis, apical 4-chamber, and apical 2-chamber views vs human expert annotation) and quantified standard left heart measures (R2 range = 0.53 to 0.91 vs study report values). Model performance was similar in 2 external validation samples. Model-derived left heart measures predicted incident heart failure, atrial fibrillation, myocardial infarction, and death. A 1-SD lower model-left ventricular ejection fraction was associated with 43% greater risk of heart failure (HR: 1.43; 95% CI: 1.23-1.66) and 17% greater risk of death (HR: 1.17; 95% CI: 1.06-1.30). Similar results were observed for other model-derived left heart measures. ConclusionsDeep learning echocardiographic interpretation accurately quantified standard measures of left heart structure and function, which in turn were associated with future clinical outcomes. Deep learning may enable automated echocardiogram interpretation and disease prediction at scale.

Разработка и верификация имитационной модели процесса теплопередачи через оконный блок с теплоотражающими экранами

Window units account for the largest specific heat losses. The use of movable heat-reflecting screens and photovoltaic solar panels is of particular interest among the existing technologies to improve the thermal protection of windows. Despite the large number of scientific papers on this issue, which consider experimental laboratory studies and numerical simulation of heat transfer processes through window units, there is no data on the influence of the edge zones of a double-glazed window, as well as the areas of interface of the window profile and the light opening on the thermal processes that occur in these energy-saving units with screens. Vertical replacing of specific heat fluxes and temperature on the inner surface of the window unit strongly influences the correctness of determining the value of the minimum allowable temperature of the indoor air. Thus, the development and verification of models of the heat transfer process through a window unit with screens is an urgent task in the context of an indoor microclimate creation. Simulation numerical modeling is performed using the finite element method based on the fundamental laws of heat transfer. The authors have used the results of experimental studies of windows with heat-reflecting screens carried out in a certified climatic chamber. The authors have developed a two-dimensional simulation model of heat transfer through a window unit with heat-reflecting screens located in the partition wall of the climate chamber. The distribution of temperatures, air flow velocities, and reduced total thermal resistance along the height of a translucent structures has been studied. The adequacy of the proposed simulation model is confirmed by comparison with the results of the experiment in a certified laboratory, as well as data obtained by other authors and regulatory documentation. The use of heat-reflecting screens in the window unit increases the resistance to heat transfer by 1,6–3,7 times depending on their number. A significant decrease in temperature in the edge zones of the double-glazed window is revealed. The use of the developed simulation model makes it possible to determine the application of heat-reflecting screens in windows for intermittent heating systems including the case of using pre-drying air technology for humid, wet, or normal operation modes of industrial premises.

Oxygen consumption of sexually mature adult, first‐feeding larval, and yearling Pacific Lampreys

AbstractObjectiveThe Pacific Lamprey Entosphenus tridentatus is considered a first food of Native American tribes, such as the Confederated Tribes of the Umatilla Indian Reservation. Populations of this imperiled species have declined such that harvest for traditional use is limited. As a result, propagation and culture of Pacific Lampreys have been initiated to supply animals for restoration and recovery efforts. These efforts require transport and periodic holding of both adults and larvae under static (no‐flow) conditions. Hence, guidelines for ensuring an adequate oxygen supply are needed for all life stages of this species.MethodsWe measured oxygen consumption rates of mature adults, first‐feeding larvae, and yearlings under static conditions at 12–15°C. In addition, we recorded indicators of stress during hypoxia for adults and estimated routine respiration rates during and after larval feeding.ResultAdults exhibited surprisingly high metabolic rates when at rest in static chambers. At 12°C, a single adult typically reduced dissolved oxygen levels in 10 L to <2 mg/L in just 90 min (oxygen consumption rates of 100–200 mg/kg/h). Adults often started to climb the walls of open chambers when dissolved oxygen levels approached 2 mg/L, allowing them to raise their branchiopores into air. Larvae remained quiescent, even when oxygen levels dropped below 1 mg/L, and costs of feeding increased routine respiration by 22–56%.ConclusionBased on these observations, we recommend that adult Pacific Lampreys always be transported in aerated containers and with access to air at the top of the tank. Although larvae exhibited hypoxia tolerance, care should be taken to ensure adequate oxygen availability, particularly during and immediately after feeding.

Experimental and numerical study on the process of removing kerosene residues in rocket engine chamber

This article conducts experimental and numerical research on the process of removing residual kerosene from the wall of the rocket engine chamber after test run, and proposes a cleaning method of high-pressure nitrogen blowing and low-pressure suction intermittent cycle. The research idea is to simulate the concentration changes of residual kerosene liquid and steam during the removal process using CFD method to analyze the mass transfer mechanism during the process, and to verify the accuracy of the numerical model through experiments. It can be concluded that the intermittent cycle cleaning method proposed in this article can efficiently remove residual kerosene from the wall of the rocket engine chamber. By using this cleaning method for 120 min, the maximum cleaning efficiency reaches 97.86%. At the same time, it was found that the high-pressure nitrogen blowing effect was the most obvious during the cleaning process, and switching between high and low pressure during the circulation process was beneficial for the removal of residual kerosene.

Growth of graphene nanowalls in low-temperature plasma: Experimental insight in initial growth and importance of wall conditioning

Plasma-enabled growth of vertically aligned graphene nanowalls (CNWs) and the influence of plasma parameters are widely investigated to produce high-quality CNWs. The initial growthsteps of CNWs and the impact of the plasma chamber condition still need to be explored. This work investigatesthe initial growth steps of CNWs and the influence of plasma chamber conditions using advanced spectroscopic and microscopic techniques. The changes in substrate surfaces and CNW growth were studied in two steps: pre-treatment and plasma deposition. Angle-resolved NEXAFS observations on the samples produced during both stages suggest that growth starts horizontallyon the substrate and changes to vertical in one critical moment. Also, we observed that CNW growth occurs not only at the deposition stage but also during the pre-treatment stage, indicating the influence of the chamber wall during the growth. Switching from horizontal to vertical orientation could be explained by the surface energy disbalance during the initial growth stages. The pre-treatment and conditioning of the chamber control the oxygen presence and provide a higher amount of carbon precursor for a fast, stable and controllable growth process. These results will direct the future possibilities of upscaling plasma systems for large-scale growth of CNWs for commercial applications by considering the influence of plasma and chamber conditions.

Study on combustion stability and flame development of ammonia/n-heptane dual fuel using multiple optical diagnostics and chemical kinetic analyses

Ammonia is considered as one of the most potential clean energy due to its carbon-free structure, which ensures the extensive decrease in global CO2 emissions. However, it has difficulty in using ammonia as a single fuel in actual apparatus due to the low reactivity and slow laminar flame speed. The dual fuel combustion of ammonia and high reactivity fuel is a potential solution, which is expected to address the issues raised by ammonia. Nevertheless, the investigations on the influence of boundary conditions on combustion stability and related mechanisms in dual fuel approach of ammonia and high reactivity fuel are still scarce at present. Therefore, in current study, n-heptane was used as the direct-injected fuel, and the investigations on combustion stability and relevant mechanisms of ammonia/n-heptane dual fuel approach were conducted by using optical diagnostics and chemical kinetic analyses. Results indicate that in n-heptane-only combustion, the premixed blue flames are found in the initial combustion stage. The auto-ignition sites dominated by orange chemiluminescence are generated near the combustion chamber wall in ammonia/n-heptane dual fuel combustion and then the flames develop towards the combustion chamber center. The addition of ammonia inhibits the combustion of n-heptane. The ammonia/n-heptane dual fuel combustion is more sensitive to the change of intake temperature compared with n-heptane-only combustion. The increase of directed-injection pressure from 300 bar to 600 bar and compression ratio from 11 to 14.5 favors the flame development speed. The increase of compression ratio is an effective mode to improve the ammonia/n-heptane dual fuel combustion stability compared with increasing intake temperature and modulating directed-injection strategies. The chemical kinetic analyses indicate that the ignition delay of dual fuel combustion of ammonia and n-heptane is more sensitive to the variations of ambient temperature compared with ambient pressure. Consequently, the changes of ambient temperature on the dual fuel combustion stability of ammonia and n-heptane play a dominant role. In a word, the dual fuel combustion stability of ammonia and n-heptane can be achieved through the collaborative optimization of multiple boundary conditions to reduce the dependence on single factor.

Nontrivial Impact of Relative Humidity on Organic New Particle Formation from Ozonolysis of cis-3-Hexenyl Acetate

The impact of relative humidity (RH) on organic new particle formation (NPF) from the ozonolysis of biogenic volatile organic compounds (BVOCs) remains an area of active debate. Previous reports provide contradictory results, indicating both the depression and enhancement of NPF under conditions of high RH. Herein, we report on the impact of RH on NPF from the dark ozonolysis of cis-3-hexenyl acetate (CHA), a green-leaf volatile (GLV) emitted by vegetation. We show that RH inhibits NPF by this BVOC, essentially shutting it down at RH levels > 1%. While the mechanism for the inhibition of NPF remains unclear, we demonstrate that it is likely not due to increased losses of CHA to the humid chamber walls. New oxidation products dominant under humid conditions are proposed that, based on estimated vapor pressures (VPs), should enhance NPF; however, it is possible that the vapor phase concentration of these low-volatility products is not sufficient to initiate NPF. Furthermore, the reaction of C3-excited state Criegee intermediates (CIs) with water may lead to the formation of small carboxylic acids that do not contribute to NPF. This hypothesis is supported by experiments with quaternary O3 + CHA + α-pinene + RH systems, which showed decreases in total α-pinene-derived NPF at ~0% RH and subsequent recovery at elevated RH.

Tritium removal from JET-ILW after T and D–T experimental campaigns

After the second Deuterium–Tritium Campaign (DTE2) in the JET tokamak with the ITER-Like Wall (ILW) and full tritium campaigns that preceded and followed after the DTE2, a sequence of fuel recovery methods was applied to promote tritium removal from wall components. The sequence started with several days of baking of the main chamber walls at 240 °C and at 320 °C. Subsequently, baking was superimposed with Ion-Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) cleaning cycles in deuterium. Diverted plasma operation in deuterium with different strike point configurations, including a Raised Inner Strike Point (RISP) configuration, and with different plasma heating—Ion Cyclotron Resonance Frequency (ICRF) and Neutral Beam Injection (NBI)—concluded the cleaning sequence. Tritium content in plasma and in the pumped gas was monitored throughout the experiment. The applied fuel recovery methods allowed reducing the residual tritium content in deuterium NBI-heated plasmas to about 0.1% as deduced from neutron rate measurements. This value is well below the requirement of 1% set by the maximum 14 MeV fusion neutron budget allocated in the ensuing deuterium plasma campaign. The quantified tritium removal over the course of the experiment was 13.4±0.7×1022 atoms or 0.67±0.03 g with ∼58% attributed to baking, ∼12.5% to ICWC, ∼26% to GDC, and ∼3.5% to first low power RISP plasmas. The experimentally estimated amount of removed tritium is in good agreement with long-term tritium accounting by the JET tritium reprocessing plant, in which the unaccounted amount was reduced by 0.71 g after the cleaning experiment.