Slot Angle Research Articles

Experimental observation of heat flux mitigation during divertor detachment in the DIII-D small angle slot divertor

Abstract Employing an array of surface eroding thermocouples (SETCs), the heat flux measured at the outer strike point of the DIII-D Small Angle Slot (SAS) divertor was found to be reduced by ~50% when the plasma reached the detachment regime compared to the attached state. Reduction in heat flux of similar magnitude has been found in both toroidal field directions (obtained by ramping up the plasma density) but with different characteristics: With the ion B × ∇B drift direction toward the SAS divertor, the heat flux measured by the SETCs first increased as plasma density increased, which may due to reduction in energy losses in the upstream and hence increase in the power flow into the divertor, and then began to roll over concurrent with a reduction in ion saturation current density on nearby Langmuir probes. In contrast, with the ion B × ∇B drift directed away from the SAS, the heat flux began at a higher value but decreases monotonically with increasing plasma density. This leads to lower heat flux in this BT direction at up to 20% lower line-averaged density. These significant differences in the onset of detachment in opposing BT directions are believed to be largely determined by the impacts of E × B drifts. Because ITER’s divertor must be operated with some degree of plasma detachment to radiate most of the power arriving in the scrape-off-layer, it is crucial to further understand the impact of magnetic drifts on plasma detachment behavior in a tight divertor geometry.

Effects of soot deposition and slot erosion on the mist film-cooling of a flat plate in the presence of upstream ramp

In the present work, the numerical analysis is conducted on the film cooling of a flat plate with the air and mist injection from a slot. The effect of soot deposition and erosion of the cooling slot has been investigated in the presence of an upstream ramp. Simulations are performed at blowing ratios, M = 1, 1.5 and 2 with the slot angles, θ = 30°, 45° and 60°. The effect of presence of upstream ramp is studied by varying ramp angles from α = 5° to 15°. The numerical study is carried out on Eulerian-Eulerian framework. Thermal phase change model based on the evaporation and condensation is used to account heat and mass transfer. It is found that the film cooling effectiveness is better for the mist injection as compared to the air injection. Soot deposition on the cooling slot has a significant influence on the film cooling effectiveness. The soot deposition is not always adversely affecting the film cooling effectiveness. Moreover, the film cooling effectiveness decreases for the eroded slot for all the investigated slot angles and ramp angles for mist injection. An increment in the film cooling effectiveness is observed for 0 < x/2w < 15 in the presence of the upstream ramp; thereafter film cooling decreases as compared to the case without the upstream ramp. The optimum slot angle to inject the mist is found to be θ = 45°.

Film Cooling over Eroded Plates for the Injection of Air–Water Mist Coolant

A computational analysis was carried out on the film cooling technique over the surfaces of eroded plates. The air–water mist coolant was injected through the slotted hole. A flat plate was patterned with various erosions. The loading fraction, f = 4–16%, and blowing ratio, M = 1–1.6, were simulated to understand their influence on the mist film cooling effectiveness. The coolant injection angle or the inclined angle of the secondary slot was kept at α = 35°. It can be observed that the increasing loading fraction raises the film cooling performance. Likewise, a higher blowing ratio can provide a better film cooling over the target surface. Again, it is found that the presence of erosion increases the cooling effectiveness at the particular surface of erosion. Simultaneously, a decrease in the effectiveness can also be noticed at the adjacent flat surfaces. Additionally, the erosions at the further downstream are more effective over the eroded surface compared to the upstream erosions. Considering the size of erosion as a crucial parameter, it was investigated for three different depth sizes. An increment in the mist film cooling performance is observed for the higher depth erosion.

Numerical Investigation of the Influence of Axial Overlap of Blade Angle Slots on an Axial Flow Compressor Stability

Numerical Investigation of the Influence of Axial Overlap of Blade Angle Slots on an Axial Flow Compressor Stability

Manipulation of E×B drifts in a slot divertor with advanced shaping to optimize detachment

SOLPS-ITER edge code analysis including drifts shows that optimization of divertor target shaping in a small angle slot (SAS) can strongly influence E× B drift particle fluxes, potentially improving divertor detachment for both toroidal field directions. This is enabled by directing recycling neutrals toward the separatrix from both the common flux region (CFR) and the private flux region (PFR) walls of the slot with a V-shape target in the slot (SAS-V), leading to two separate reinforcing effects, each individually involving positive feed-back: (a) increase of neutral recycling at the PFR wall of the slot due to—and causing—strong radial E× B ion flux from the CFR to the PFR; (b) decrease of E× B loss of ions out of the outer divertor into the inner divertor via the PFR due to reduction of the radial gradient of electron temperature at the outer target caused by the increased particle retention in the outer divertor. This circumvents the general problem for divertor operation with ion B ×∇B toward the X-point: E× B loss of particles from the outer divertor CFR plasma tends to keep it hot and attached. This work identifies a strong interaction between divertor geometry and drifts, a potentially important effect for optimizing advanced divertors for power exhaust in fusion reactors.

Research and test of key components of the squirrel-cage bullet shell counter

In order to solve the problem of counting when the bullet shells is recovered, a kind of squirrel-cage bullet shells counters is designed. Through theoretical analysis and test, The angle of the bullet slot of the squirrel cage shell counter is 31.3 ° and the rotation speed of the cartridge mechanism is 10 R / min. The squirrel cage shell counter has the advantages of simple structure, few components, 3D printing technology, greatly reducing the weight and power consumption. The whole machine test results show that: The counting efficiency of the slot type bullet shell counter is 87.4 pieces / minute, and the counting accuracy is 99.8%. The counting efficiency and precision of the slot type bullet shell counter can meet the design requirements of the army. This research not only provides a practical shell counting tool for the military, but also provides a reference for the innovation, research and optimization design of other similar mechanical equipment.

Modification of Drafting Zone of Jute Flyer Spinning Frame to Improve the Jute Yarn Quality

Being concerned with the growth and sustainability of the jute industry of Bangladesh, the machinery modifications deserves higher priority. In this work, it is desired to perform a modification of the apron draft spinning frame to improve the jute yarn quality. However, the existing drawing pressing roller (Diameter=70 mm &amp; Durometer hardness = 96 in Shore A Scale) of the drafting zone of the apron draft jute spinning frame has been replaced by a comparatively softer rubber coated top roller (diameter= 40 mm &amp; Durometer hardness = 85 in Shore A Scale). Besides, an extra slotted roller (Diamter= 26 mm &amp; Durometer hardness = 74 in Shore A Scale) has also been nipped with bottom drawing roller and positioned parallel to the modified top roller. Three types of modifications have been designed by varying slot angles (i.e., 45°, 60°, and 75°) of slotted roller attached with the modified top roller. Finally, jute yarn counts of 6.5, 8, and 10 lbs/spyndle have been produced for both existing and modified frames. Results reveal that the modified spinning frame with all three types of slotted roller produced better results regarding the yarn hairiness compared to the existing frame irrespective of yarn fineness. Yarn hairiness values in modified frame with 60° slotted roller have been decreased maximum by 28.1%, 35.85%, and 32.92% compared to that of the existing system for 6.5, 8, and 10 lbs/spyndle respectively. Yarn strength results have been improved with the modified system as well. Lastly, it is seen that ends down rate in modified spinning frames have been reduced noticeably irrespective of yarn fineness.

Study on the model of semi-open-end twist in compact spinning with lattice apron

The twist mechanism of the fiber strand in the condensing zone in compact spinning is complex. This paper proposes a dynamic model to evaluate the additional twist of the fiber strands. Based on the flow simulation in the condensing zone, the fiber trajectory in the suction slot was simulated and obtained. Several spinning parameters such as suction slot angle, suction slot width, negative pressure, and shape of suction slot, were varied to show their effects on the additional twist. The simulation results indicated that by increasing the suction slot angle from 5° to 10° the additional twist increased significantly. Higher negative pressure also leads to an increase in the additional twist. The suction slot width has a greater effect on the fiber trajectory than on the additional twist. An arc-shape suction slot increased the additional twist compared with a linear-shape one. An experimental test conducted revealed a precise agreement with the simulation results.

Electromagnetic-thermal behaviors of bulk superconductor with cuboid slot under moving magnetic field

We established a 3D coupled model to study the electromagnetic-thermal behaviors of a levitation system containing a bulk high-temperature superconductor (HTS) with a cuboid slot under the nonuniform magnetic field due to the movement of a permanent magnet (PM), analysing the influences of the geometrical parameters of the slot and inclination angle on the electromagnetic-thermal behaviors, giving the dynamic distribution of the global electromagnetic force density in the HTS. The results show that the longer the length of the slot, the smaller the levitation force, and the greater the loss. As its length takes up 7/10 of the HTS diameter, the loss is 4 times that of the HTS without damage. Due to the homodromous induced current appearing near the slot, the maximum guidance force increases with the length. The levitation force decreases with the increase of the slot depth. Its curve near the maximum becomes blunt and the loss increases significantly. As the depth is 3/5-4/5 of the HTS height, the loss is 300–400 times of that without damage. The guidance force and loss increase with the depth. As the inclination angle rises, the levitation and guidance force both drop. At 30 °, their maximums decrease by 70 % and 90 %, respectively. The lateral stability of the system thus becomes poorer, indicating the inclination angle is one of the important factors for instability. As the PM moves vertically, the guidance force density symmetrically distributes near the both wide sides of the slot. Its side faces with the wide sides will bear the shear force, resulting in that the slot has the tendency to tear along these faces. As the PM reciprocates laterally, the slot is subjected to the lateral shear force, proportional to the displacement.

Critical velocity of active air jet required to enhance free opening rectangular exhaust hood

Using a radial active air jet ejected from the slot surrounding a circular exhaust hood opening can increase the air speed generated by the hood as well as achieve a larger capacity to exhaust pollutants. Critical parameters of the Aaberg hood have been identified to ensure the positive effect of the active jet. This paper proposed a novel type of enhanced exhaust hood using the rectangular opening in place of the circular one in Aaberg hood to meet the needs of different shape and size of exhaust hood. To understand the performance of this kind of exhaust hood and to determine the critical velocity of the active air jet, the flow characteristics and the centerline velocity are investigated by changing the exhaust rate, hood size, jet angle, jet velocity and jet slot width via experimental and numerical methods. Results show that the critical jet velocity exists between two working modes of the novel exhaust hood, one is the ineffective mode with the short-circuit jet, and the other is jet-enhanced mode with the developed radial jet. The near-wall circulation along the hood opening perimeter is not attributed to the existence of the jet. The suggested equation which error is proven to be within 12.5% for the critical velocity presented in this paper is simple in structure, and will help to facilitate the choice of the energy-efficient exhaust hood design in residential and industrial buildings to save energy that would be wasted on increasing the exhaust rate.

Torque Performance Improvement for Slotted Limited-Angle Torque Motors by Combined SMA Application and GA Optimization

Due to stator magnetic saturation and inherent cogging torque, the slotted limited angle torque motor (LATM) performs large torque ripple within its operation range, resulting in vibration noise and complex control problem. The novelty of this article is to not only first to apply 1J22 soft magnetic alloy (SMA) in the LATM but also to propose a multiobjective optimization method to improve the torque performances including torque ripple, cogging torque, and output torque, based on genetic algorithm (GA). First, 1J22 SMA is applied to the LATM to reduce the torque ripple caused by magnetic field saturation. Then, through the sensitivity analysis, weight coefficients of the related parameters of stator tooth for the optimization process are obtained. Besides, in order to optimize torque performances, the multiobjective optimization process is carried out and the GA is used to obtain the desired objective. Finally, the finite-element analysis (FEA) is used to validate the optimization design.

Research on Torque Ripple Suppression of the Slotted Limited Angle Torque Motor

This article presents the theoretical analysis and numerical modeling of various cogging torque suppression methods of the slotted limited angle torque motor (LATM). The relationship between the cogging torque, the output characteristics, and the structure parameters of new methods is revealed by derived equations and finite-element analysis (FEA), which provides a theoretical basis for the optimization of the slotted LATM. The effectiveness of the best suppression method is verified by the prototype experiment. In addition, a method to predict torque distortion caused by armature reaction is proposed and it is verified by the finite-element simulation and prototype experiment.

High precision strike point control to support experiments in the DIII-D small angle slot divertor

Improvements in strike point control enabled tests with the new small angle slot (SAS) divertor installed at DIII-D with precision as tight as ±1 mm, barring brief perturbations from ELMs. Aside from being narrower than previous baffle structures in DIII-D, simulations indicate that performance of the SAS divertor should be very sensitive to strike point position, making the improved strike point control essential for experiments with the SAS divertor. Improved control entails regulating more divertor geometry target locations than before and setting higher gain on the strike point target. This is achieved by tasking more poloidal field (PF) shaping coils with divertor topology control, fine tuning of the coil configuration and algorithm gains, and adding regulation of the power supply common rail. The result is that although more variables are controlled, precision is better: high frequency jitter in the strike point position is lower on average compared to related discharges with standard divertor shape control.

Study on SHGC Calculation and Measurement of Window Installed with Shading Device

The Solar Heat Gain Coefficient (SHGC) is one of the energy loss factors in buildings, which affects a cooling load significantly. A variety of shading devices and high-performance windows have already been developed and applied to a large number of buildings to reduce a cooling load. However, performance evaluation on these shading devices and high-performance windows has depended on calculation via mathematical models and simulations. These evaluation methods have limits when reflecting heat characteristics of the ever-increasing complexity and development of window systems accurately in a realistic way. Thus, it is critically necessary to verify performance evaluation results through actual measure. The purpose of this paper is to measure the SHGC of various types of windows and shading devices and to analyze the difference between the calculated value and the measured value. The experimental result is as follows. SHGC of venetian blind is lower than SHGC of roll screen and Triple shade. The higher the glass SHGC was, the higher the SHGC reduction rate was under the same condition. The larger the slot angle was, the greater the SHGC performance improved. The analysis result on measured and calculated values showed that a mean different ratio was 4.86 %, which was matched within 5 % of the deviation rate. However, the different ratio tended to increase as the complexity of structures and types of windows increased.

Improved core-edge compatibility using impurity seeding in the small angle slot (SAS) divertor at DIII-D

Impurity seeding studies in the small angle slot (SAS) divertor at DIII-D have revealed a strong relationship between the detachment onset and pedestal characteristics with both target geometry and impurity species. N2 seeding in the slot has led to the first simultaneous observation of detachment on the entire suite of boundary diagnostics viewing the SAS without degradation of core confinement. SOLPS-ITER simulations with D+C+N, full cross field drifts, and n–n collisions activated are performed for the first time in DIII-D to interpret the behavior. This highlights a strong effect of divertor configuration and plasma drifts on the recycling source distribution with significant consequences on plasma flows. Flow reversal is found for both main ions and impurities affecting strongly the impurity transport and providing an explanation for the observed dependence on the strike point location of the detachment onset and impurity leakage found in the experiments. Matched discharges with either nitrogen or neon injection show that while nitrogen does not significantly affect the pedestal, neon leads to increased pedestal pressure gradients and improved pedestal stability. Little nitrogen penetrates in the core, but a significant amount of neon is found in the pedestal consistent with the different ionization potentials of the two impurities. This work demonstrates that neutral and impurity distributions in the divertor can be controlled through variations in strike point locations in a fixed baffle structure. Divertor geometry combined with impurity seeding enables mitigated divertor heat flux balancing core contamination, thus leading to enhanced divertor dissipation and improved core-edge compatibility, which are essential for ITER and for future fusion reactors.

Effect of Slot Area Ratio and Slot Angle on Swirl Cooling in a Gas Turbine Blade Leading Edge

This paper numerically simulated a swirl cooling system to study the influences of the slot area ratio and slot angle on the flow field and heat transfer performance. Numerical simulations were performed for different coolant inlet to outlet slot area ratios (1, 2, 3, and 4) and slot angles (60°, 75°, 90°, and 105°) at different Reynolds numbers. Results indicate that large-scale vortices and small circular or oval vortices are generated in the cooling channel at different slot area ratios and slot angles. At identical Reynolds numbers, the cooling system achieved 30% and 23% increases in global Nusselt number and thermal performance factor, respectively, when the slot area ratio increased from 1 to 4. Although the system obtained only a 7.5% increase in global Nusselt number, it achieved a 29.8% increase in thermal performance factor when the slot angle increased from 60° to 105° at fixed Reynolds number. The applied cooling system is recommended for the internal swirl cooling of a gas turbine blade leading edge at optimum values of design parameters at a slot area ratio of 4 and slot angle 105° at high Reynolds number.

Volumetric Changes in Morse Taper Connections After Implant Placement in Dense Bone. In-Vitro Study.

The stability of the implant–abutment interface is crucial for the maintenance of the implant index integrity. Several factors are capable of inducing deformation in implant–abutment connection, such as the actual insertion of the implant into the bone. This study aimed to evaluate the deformations produced in the connection after the insertion of the implant. Ten implants with two different implant carriers (Type A: carrier attached to platform and Type B: carrier attached inside the index-connection) were placed in artificial Type II bone, and volumetric changes were evaluated for different connection features with a 3D digital microscope. ANOVA (analysis of variance), Wilcoxon, and Tukey HSD post-test were used for statistical comparisons. Type A implants presented deformation at the platform level (inner slot angles and slot width), but no volumetric changes were observed inside the connection. Type B implants presented deformation in three parameters inside the connection (outer channel length, coronal step width, and coronal step length). Within the limitations of this study, we can conclude that more deformation is expected at the internal connection when the implant carrier engages this area. The engagement area should be as far away as possible from the index connection.

Evaluation of the impact of divertor closure on high-Z material transport and leakage in small angle slot divertor with toroidal tungsten rings in DIII-D

Predictive modeling of the closed Small Angle Slot (SAS) divertor with toroidal tungsten (W) rings in different poloidal locations is conducted to evaluate the impact of divertor closure on high-Z impurity sourcing and transport. These simulations utilize the DIVIMP code for W erosion, transport and deposition/redeposition, with background plasma solutions provided by SOLPS5.1. It is found that the level of W leakage is mostly determined by the divertor plasma conditions, the location of the W source and redeposition processes. High density plasmas in the SAS slot result in shorter ionization mean free paths than in the far-target region, resulting in higher redeposition rate. The induced friction force dominates in the near-target region, driving W impurities downstream towards the target surface. As a result, a W source at the strike point in the SAS divertor demonstrates lower net erosion and divertor leakage, despite higher gross erosion, compared to W sources in the far-target region.

Preliminary Design of an All-Ceramic Discrete-Structure Particle Heating Receiver

Abstract Discrete structure particle heating receivers (DS-PHR), as used in concentrated solar power (CSP) systems, employ suitable discrete porous structures to intermittently halt the falling particles to control the speed and increase the residence time of falling particulates, thereby increasing the temperature rise of particulates exiting the DS-PHR. Previous designs of DS-PHRs have considered both porous foam structures, which have mass flux limits, and metal wire meshes, which are effective but have temperature and other functional limitations. This paper recounts recent studies at Georgia Tech and King Saud University that have investigated the use of ceramic tiles made porous by discrete slot-shaped passages in place of previous metal wire meshes. Currently, for experimental use, the slot-like passages are cut into the tiles by water jet, but operational units are expected to be formed into shape and fired by more economical conventional ceramic techniques. Benefits of ceramic and other refractory materials include higher temperature and heat flux limits at a reasonable cost. The tiles are expected to be installed in chevron configuration, which have been shown by experience to be especially effective, and these so-called ceramic chevrons have been shown to deliver adequate mass flux densities while still removing most of the kinetic energy from the particles. In addition, the thickness of the tile allows the incorporation of angled slots capable of redirecting the particle flow, adding a method to control particle mixing by purposefully directing the particulate streams. These enhanced slots are typically arranged with adequate spacing to allow for increased penetration of concentrated light into the depth of the falling bed of particles and may be angled to redirect hot particles toward the back plane of the DS-PHR. Both of these features should help minimize depthwise temperature variation. The testing reported here will focus on the degree of velocity and flow control that can be achieved by proper design of these ceramic chevrons as well as demonstrate the effectiveness of different designs on light penetration. Prior to this research, the effectiveness of ceramic obstructions might have been properly doubted because of the very high coefficient of restitution (COR) for the impact of ceramic particles on ceramic solids. In reality, it will be shown that a layer of particulates will form on a chevron, which effectively dissipates the kinetic energy of the impacting particles. Overall, this paper will report improvements in DS-PHR designs that can withstand high temperatures and fluxes, achieve additional control of particle flow, enhance particle mixing, and allow deeper penetration of light into the depth of the falling bed.

Context-Based Parking Slot Detection With a Realistic Dataset

The autonomous parking of vehicles requires the ability to accurately locate an available parking slot in the vicinity of a vehicle. Since parking slots have a variety of shapes and colors, may be occluded by obstacles, or look different due to surroundings such as lighting, accurately locating them can be a challenging task. In this paper, we propose a context-based parking slot detection method inspired by the process of a human driver finding a parking slot. Our method consists of two deep network modules: a parking context recognizer and parking slot detector . The parking context recognizer identifies the parking environment (type, angle, and availability of a parking slot), whereas the parking slot detector locates the exact position of a parking slot by multiple type-based fine-tuned detectors with rotated anchor boxes and a rotated non-maximal suppression. In addition, we release a realistic parking slot dataset, which comprises 22817 images of parking slots having various attributes and external conditions. We also propose a new evaluation metric for parking slot detection, reflecting whether a vehicle can be parked within the detected parking slot. Through comparison and ablation study in experiments, we demonstrate that our method outperformed the previous deep-learning-based methods, along with having a short operation time. The source codes and the dataset are available at https://github.com/dohoseok/context-based-parking-slot-detect/ .