Core Region Research Articles

Aberrant functional connectivity of the salience network in adult patients with tic disorders: a resting-state fMRI study.

Tic disorders (TD) are characterized by the presence of motor and/or vocal tics. Common neurophysiological frameworks suggest dysregulations of the cortico-striatal-thalamo-cortical (CSTC) brain circuit that controls movement execution. Besides the common tics, there are other "non-tic" symptoms that are primarily related to sensory perception, sensorimotor integration, attention, and social cognition. The existence of these symptoms, the sensory tic triggers and the modifying effect of attention and cognitive control mechanisms on tics may indicate the salience network's involvement in the neurophysiology of TD. Resting-state functional MRI measurements were performed in 26 participants with TD and 25 healthy controls. The group differences in resting-state functional connectivity patterns were measured based on seed-to-voxel connectivity analyses. Compared to healthy controls, patients with TD exhibited altered connectivity between the core regions of the salience network (insula, ACC and TPJ) and sensory, associative, and motor-related cortices. Furthermore, connectivity changes were observed in relation to the severity of tics in the TD group. The salience network, particularly the insula, is likely to be an important site of dysregulation in TD. Our results provide evidence for large-scale neural deviations in TD beyond the CSTC pathologies. These findings may be relevant for developing treatment targets.Significance statement Tic disorders (TD) are associated with a variety of symptoms beyond typical motor and vocal tics that affect sensory perception, attention, and social cognition. The presence of such non-tic symptoms suggests the potential involvement of the salience network in the pathophysiology of TD. While previous studies have predominantly focused on the cortico-striato-thalamo-cortical (CSTC) circuitry, which is known to underlie tic generation and expression, we conducted resting-state fMRI to investigate the functional connectivity of the salience network in TD. Notably, we observed impaired connectivity of the salience network with relations to the tic symptom severity. Our research provided important evidence that the pathophysiology of TD involves the salience network, which is highly relevant for developing treatment strategies.

Orbital angular momentum modes in dielectrically chiral-core fibers

Abstract In this paper, we investigate a dielectrically chiral-core fiber for the generation of orbital angular momentum (OAM) modes. We observe that the presence of chirality induces a modal index split between the same order OAM modes with opposite topological charges and arbitrary phase front rotation directions, which are originally degenerate in achiral fibers. This split indicates the existence of circular birefringence (CB) associated with a dielectric chirality. The modal cutoff splits result in a single polarization property without the possibility of coupling between the same order modes that correspond to a single +l or -l OAM mode guiding. However, neither of the two fundamental modes guided in the chiral fiber exhibits a cutoff, despite having different modal indices due to chirality. Upon fraction of modal power cutoff, the high-order modes in the core region display different cutoff fractions of modal power between the same order modes, while the fundamental mode has no cutoff fraction of modal power. Owing to the CB and different fractions of modal power in the core for different handed OAM modes, dielectrically chiral fibers have potential applications in chiral sensing, circular polarization-dependent OAM mode filters, and new kind of OAM mode generators.

Composite cores of monopoles and Alice rings in spin-2 Bose-Einstein condensates

We show that energy relaxation causes a point defect in the uniaxial-nematic phase of a spin-2 Bose-Einstein condensate to deform into a spin-Alice ring that exhibits a composite core structure with distinct topology at short and long distances from the singular line. An outer biaxial-nematic core exhibits a spin half-quantum vortex structure with a uniaxial-nematic inner core. By numerical simulation, we demonstrate a dynamical oscillation between the spin-Alice ring and a split-core hedgehog configuration via the appearance of ferromagnetic rings with associated vorticity inside an extended core region. We further show that a similar dynamics is exhibited by a spin-Alice ring surrounding a spin-vortex line resulting from the relaxation of a monopole situated on a spin-vortex line in the biaxial-nematic phase. In the cyclic phase, similar states are shown instead to form extended phase-mixing cores containing rings with fractional mass circulation or cores whose spatial shape reflects the order-parameter symmetry of a cyclic inner core, depending on the initial configuration. Published by the American Physical Society 2024

Structural and dynamic insights into the activation of the μ-opioid receptor by an allosteric modulator

G-protein-coupled receptors (GPCRs) play pivotal roles in various physiological processes. These receptors are activated to different extents by diverse orthosteric ligands and allosteric modulators. However, the mechanisms underlying these variations in signaling activity by allosteric modulators remain largely elusive. Here, we determine the three-dimensional structure of the μ-opioid receptor (MOR), a class A GPCR, in complex with the Gi protein and an allosteric modulator, BMS-986122, using cryogenic electron microscopy. Our results reveal that BMS-986122 binding induces changes in the map densities corresponding to R1673.50 and Y2545.58, key residues in the structural motifs conserved among class A GPCRs. Nuclear magnetic resonance analyses of MOR in the absence of the Gi protein reveal that BMS-986122 binding enhances the formation of the interaction between R1673.50 and Y2545.58, thus stabilizing the fully-activated conformation, where the intracellular half of TM6 is outward-shifted to allow for interaction with the Gi protein. These findings illuminate that allosteric modulators like BMS-986122 can potentiate receptor activation through alterations in the conformational dynamics in the core region of GPCRs. Together, our results demonstrate the regulatory mechanisms of GPCRs, providing insights into the rational development of therapeutics targeting GPCRs.

Early-phase core degradation interpretation by interaction between fuel cladding and fuel components in Fukushima Daiichi nuclear power plant Unit 2

ABSTRACT The early phase of the core degradation at the Fukushima Daiichi Nuclear Power Station Unit 2 was investigated in terms of a fuel-component degradation by materials interaction by carrying out the accident analysis, evaluation of chemical conditions and experimental works. First, the accident scenario was evaluated to specify a target period (from 18:40 to 22:40 on NaN Invalid Date NaN), and then the temperature and H2/H2O pressure ratio in the core region during this period were calculated based on plant parameters. Subsequently, semi-integral experiments were performed using the mocked-up fuel components of a boiling water reactor (BWR). Furthermore, separate-effects tests using Ni-alloy/Zircaloy4 were also performed to understand the phenomenon observed in the semi-integral experiments, where the Ni-Zr reaction occurred even with the oxide layer on the Zr-based alloy. Consequently, it was estimated that the Zr-Ni eutectic melting reaction above 1100°C under steam-starved conditions resulted in a fuel failure at 19:08, melting of spacer locations at 19:37, and upper-tie-plate at 21:26. The first and second degradations could have caused the release of radioactive elements or particles leading to the neutron detection at 21:00 in front of the main gate, and the third degradation could have resulted in the separation of the upper-tie-plate.

Gradients of properties increase the morphing and stiffening performance of bioinspired synthetic fin rays

Abstract State-of-the-art morphing materials are either very compliant to achieve large shape changes (flexible metamaterials, compliant mechanisms, hydrogels), or very stiff but with infinitesimal changes in shape that require large actuation forces (metallic or composite panels with piezoelectric actuation). Morphing efficiency and structural stiffness are therefore mutually exclusive properties in current engineering morphing materials, which limits the range of their applicability. Interestingly, natural fish fins do not contain muscles, yet they can morph to large amplitudes with minimal muscular actuation forces from the base while producing large hydrodynamic forces without collapsing. This sophisticated mechanical response has already inspired several synthetic fin rays with various applications. However, most “synthetic” fin rays have only considered uniform properties and structures along the rays while in natural fin rays, gradients of properties are prominent. In this study, we designed, modeled, fabricated and tested synthetic fin rays with bioinspired gradients of properties. The rays were composed of two hemitrichs made of a stiff polymer, joined by a much softer core region made of elastomeric ligaments. Using combinations of experiments and nonlinear mechanical models, we found that gradients in both the core region and hemitrichs can increase the morphing and stiffening response of individual rays. Introducing a positive gradient of ligament density in the core region (the density of ligament increases towards the tip of the ray) decreased the actuation force required for morphing and increased overall flexural stiffness. Introducing a gradient of property in the hemitrichs, by tapering them, produced morphing deformations that were distributed over long distances along the length of the ray. These new insights on the interplay between material architecture and properties in nonlinear regimes of deformation can improve the designs of morphing structures that combine high morphing efficiency and high stiffness from external forces, with potential applications in aerospace or robotics.

Suppression of equilibrium magnetic islands by density profile effect in quasi-axisymmetric stellarator plasmas

In a quasi-axisymmetric stellarator, a significant bootstrap current will result in the generation of low-order rational surfaces and three-dimensional (3D) magnetic islands. In this paper, the influence of plasma density profiles on the equilibrium magnetic islands for the Chinese first quasi-axisymmetric stellarator (CFQS) is investigated using the HINT code. It is found that the flattening of the core plasma density profile leads to a significant suppression of magnetic islands. When the peaking factor of plasma density is 1.19, complete suppression of magnetic islands occurs while maintaining excellent integrity of the magnetic surface even with the volume-averaged plasma beta <β> increase up to 2%. On the other hand, during the transition of a plasma density profile from flat to hollow, there is a reversal in the core bootstrap current, resulting in reduction of rotational transform values to pass through the rational surface. Hence, formation of magnetic islands in the core region. Therefore, effective inhibition of CFQS’s magnetic islands can be achieved by appropriately controlling density profiles through methods like gas injection.

Drifting towards multidimensional collaborative innovation: the co-evolution of collaboration networks and policy in China’s nuclear power industry

Purpose Nuclear power is a stable and reliable energy source that can improve energy structure while reducing carbon emissions, which is of great significance for environmental protection and combating climate change. As a unique industry, it is facing rare development opportunities in China and has broad market prospects. However, the characteristics of technical difficulty, loose organizational structure and uneven regional distribution limit the expansion of the nuclear power industry. This paper aims to a better understanding of the accumulation process for innovation capability from the perspective of network evolution and provides policy guidance for the market development of the nuclear power industry (NPI). Design/methodology/approach Methodologically, social network analysis is used to explore the co-evolution of multidimensional collaboration networks. First, the development and policy evolution of the NPI is introduced to divide the evolution periods. Then, the authors identify and analyze the core organizations, technologies and regions that promote nuclear power patent collaboration. Furthermore, three levels of collaboration networks based on organizations, technologies and regions are constructed to analyze the coevolution of patent networks in China’s NPI. Findings The results show that nuclear power enterprises always play the foremost role in the organizational collaboration network (OCN), and the dominance of foreign enterprises is replaced by Chinese state-owned enterprises in the third period. The technology hotspot has shifted from nuclear power plant construction to the control system. The regional collaboration network was initially formed in the coastal areas and gradually moved inland, with Guangdong and Beijing becoming the two cores of the network. The scale of three collaboration networks is still expanding but the speed has slowed down. Originality/value In response to the pain points of the NPI, this research focuses on multidimensional collaborative innovation, investigates the dynamic evolution process of collaborative innovation networks in China’s NPI and links policy evolution with network evolution creatively. The ultimate result not only helps nuclear power enterprises integrate innovative resources in complex environments but also promotes industrial upgrading and market development.

Continuous Theta-Burst Stimulation on the Left Posterior Inferior Frontal Gyrus Perturbs Complex Syntactic Processing Stability in Mandarin Chinese

Abstract The structure of human language is inherently hierarchical. The left posterior inferior frontal gyrus (LpIFG) is proposed to be a core region for constructing syntactic hierarchies. However, it remains unclear whether LpIFG plays a causal role in syntactic processing in Mandarin Chinese and whether its contribution depends on syntactic complexity, working memory, or both. We addressed these questions by applying inhibitory continuous theta-burst stimulation (cTBS) over LpIFG. Thirty-two participants processed sentences containing embedded relative clauses (i.e., complex syntactic processing), syntactically simpler coordinated sentences (i.e., simple syntactic processing), and non-hierarchical word lists (i.e., word list processing) after receiving real or sham cTBS. We found that cTBS significantly increased the coefficient of variation, a representative index of processing stability, in complex syntactic processing (esp., when subject relative clause was embedded) but not in the other two conditions. No significant changes in d′ and reaction time were detected in these conditions. The findings suggest that (a) inhibitory effect of cTBS on the LpIFG might be prominent in perturbing the complex syntactic processing stability but subtle in altering the processing quality; and (b) the causal role of the LpIFG seems to be specific for syntactic processing rather than working memory capacity, further evidencing their separability in LpIFG. Collectively, these results support the notion of the LpIFG as a core region for complex syntactic processing across languages.

Microglia and macrophages in glioblastoma: landscapes and treatment directions.

Glioblastoma is the most common primary malignant tumour of the central nervous system and remains uniformly and rapidly fatal. The tumour-associated macrophage (TAM) compartment comprises brain-resident microglia and bone marrow-derived macrophages (BMDMs) recruited from the periphery. Immune-suppressive and tumour-supportive TAM cell states predominate in glioblastoma, and immunotherapies, which have achieved striking success in other solid tumourshave consistently failed to improve survival in this 'immune-cold' niche context. Hypoxic and necrotic regions in the tumour core are found to enrich, especially in anti-inflammatory and immune-suppressive TAM cell states. Microglia predominate at the invasive tumour margin and express pro-inflammatory and interferon TAM cell signatures. Depletion of TAMs, or repolarisation towards a pro-inflammatory state, are appealing therapeutic strategies and will depend on effective understanding and classification of TAM cell ontogeny and state based on new single-cell and spatial multi-omic in situ profiling. Here, we explore the application of these datasets to expand and refine TAM characterisation, to inform improved modelling approaches, and ultimately underpin the effective manipulation of function.

DEM-CFD Simulation Analysis of Heat Transfer Characteristics for Hydrogen Flow in Randomly Packed Beds

In this study, three randomly packed beds with varying tube-to-particle diameter ratios (D/d) are constructed using the discrete element method (DEM) and simulated via CFD under low pore Reynolds numbers (Rep &lt; 100). An innovation of this research lies in the application of hydrogen in randomly packed beds, coupled with the consideration of its temperature-dependent thermal properties. The axial analysis of the heat transfer characteristics shows that PB−5 and PB−6 achieve thermal equilibrium 44% and 58% faster than PB−4, respectively, demonstrating enhanced heat transfer efficiency. However, at higher flow rates (0.8 m/s), the large-sized fluid channels in PB−6 severely impact the heat transfer efficiency, slightly reducing it compared to PB−5. Additionally, this study introduces a localized segmentation method for calculating the axial local Nusselt number, showing that the axial local Nusselt number (Nu) not only exhibits an inverse relationship with the axial porosity distribution, but also matches its amplitude fluctuations. The wall effect significantly impacts the flow and temperature distribution in the packed bed, causing notable velocity and temperature oscillations in the near-wall region. In the near-wall region, the average temperature is lower than in the core region, and the axial temperature profile exhibits more intense oscillations. These findings may provide insights into the use of hydrogen in randomly packed beds, which are vital for enhancing industrial applications such as hydrogen storage and utilization.

Changes in Mesoscale Convective System Precipitation Structures in Response to a Warming Climate

AbstractMesoscale convective systems (MCSs) are crucial components of the hydrological cycle and often produce flash floods. Given their impact, it is important to understand how they will change under a warming climate. This study uses a satellite‐ and radar‐based MCS tracking algorithm on convection‐permitting climate model simulations and examines changes in MCS properties and precipitation structures between historical and future simulations. An underestimation in MCS total precipitation is evident in historical simulation compared to observations, due to model's depiction of MCS precipitation area and summertime occurrence frequency. Under pseudo‐global warming, increases in MCS frequency and total warm season precipitation are observed, most notably in the southern U.S. The precipitation intensity and precipitating area generated by future MCSs also rises and results in an increase in precipitation volume. MCS precipitation structures are further classified into convective core and stratiform regions to understand how change in these structures contributes to future rainfall changes. In a warmer climate, the stratiform region demonstrates minimal change in size, but increases in mean precipitation rate and mean maximum precipitation rate by 15% and 29% are noted, respectively. A more robust future response is observed in the convective core region, with its size, mean precipitation rate and mean maximum precipitation rate increasing significantly by 24%, 37% and 42%, respectively. Finally, by examining the environmental properties of MCS initial condition, future intensification of convective rain may be attributed to a combined effect of substantial increases in atmospheric instability and moisture availability.

Turbulence-induced droplet grouping and augmented rain formation in cumulus clouds

This paper provides the first observational analysis of how droplet separation is impacted by the flinging action of microscale vortices in turbulent clouds over a select radii range and how they vary over cloud cores and along the peripheral edges. It is premised that this mechanism initiates droplet separation within a cloud volume soon after condensational growth, largely in the cloud core, and operates until the cloud droplet radii exceed 20–30 µm when this effect fades rapidly. New observations are presented showing how microscale vortices also impact the settling rates of droplets over a critical size range (6–18 µm) causing them to sediment faster than in still air affecting swept volumes and thereby impacting the rain initiation and formation. Large-scale atmospheric models ignore these microscale effects linked to rapid droplet growth during the early stages of cloud conversion. Previous studies on droplet spatial organization along the cloud edges and inside the deep core have shown that homogeneous Poisson statistics, indicative of the presence of a vigorous in-cloud mixing process at small scales obtained, in contrast to an inhomogeneous distribution along the edges. In this paper, it is established that this marked core region, homogeneity can be linked to microscale vortical activity which flings cloud droplets in the range of 6–18 µm outward. The typical radius of the droplet trajectories or the droplet flung radii around the vortices correlates with the interparticle distance strongly. The correlation starts to diminish as one proceeds from the central core to the cloud fringes because of the added entrainment of cloud-free air. These first results imply that droplet growth in the core is first augmented with this small-scale interaction prior to other more large-scale processes involving entrainment mixing. This first study, combining these amplified velocities are included in a Weather Research and Forecasting- LES case study. Not only are significant differences observed in the cloud morphology when compared to a baseline case, but the ‘enhanced’ case also shows early commencement of rainfall along with intense precipitation activity compared to the ‘standard’ baseline case. It is also shown that the modelled equilibrium raindrop spectrum agrees better with observations when the enhanced droplet sedimentation rates mediated by microscale vortices are included in the calculations compared to the case where only still-air terminal velocities are used.

Assessment of CMIP6 GCMs’ Simulation of Southwest Monsoon Rainfall over Indian Monsoon Core Region

Assessment of CMIP6 GCMs’ Simulation of Southwest Monsoon Rainfall over Indian Monsoon Core Region

FgPfn participates in vegetative growth, sexual reproduction, pathogenicity, and fungicides sensitivity via affecting both microtubules and actin in the filamentous fungus Fusarium graminearum.

Fusarium head blight (FHB), caused by Fusarium graminearum species complexes (FGSG), is an epidemic disease in wheat and poses a serious threat to wheat production and security worldwide. Profilins are a class of actin-binding proteins that participate in actin depolymerization. However, the roles of profilins in plant fungal pathogens remain largely unexplored. Here, we identified FgPfn, a homolog to profilins in F. graminearum, and the deletion of FgPfn resulted in severe defects in mycelial growth, conidia production, and pathogenicity, accompanied by marked disruptions in toxisomes formation and deoxynivalenol (DON) transport, while sexual development was aborted. Additionally, FgPfn interacted with Fgα1 and Fgβ2, the significant components of microtubules. The organization of microtubules in the ΔFgPfn was strongly inhibited under the treatment of 0.4 μg/mL carbendazim, a well-known group of tubulin interferers, resulting in increased sensitivity to carbendazim. Moreover, FgPfn interacted with both myosin-5 (FgMyo5) and actin (FgAct), the targets of the fungicide phenamacril, and these interactions were reduced after phenamacril treatment. The deletion of FgPfn disrupted the normal organization of FgMyo5 and FgAct cytoskeleton, weakened the interaction between FgMyo5 and FgAct, and resulting in increased sensitivity to phenamacril. The core region of the interaction between FgPfn and FgAct was investigated, revealing that the integrity of both proteins was necessary for their interaction. Furthermore, mutations in R72, R77, R86, G91, I101, A112, G113, and D124 caused the non-interaction between FgPfn and FgAct. The R86K, I101E, and D124E mutants in FgPfn resulted in severe defects in actin organization, development, and pathogenicity. Taken together, this study revealed the role of FgPfn-dependent cytoskeleton in development, DON production and transport, fungicides sensitivity in F. graminearum.

Functionalizing DNA Origami by Triplex-Directed Site-Specific Photo-Cross-Linking.

Here, we present a cross-linking approach to covalently functionalize and stabilize DNA origami structures in a one-pot reaction. Our strategy involves adding nucleotide sequences to adjacent staple strands, so that, upon assembly of the origami structure, the extensions form short hairpin duplexes targetable by psoralen-labeled triplex-forming oligonucleotides bearing other functional groups (pso-TFOs). Subsequent irradiation with UVA light generates psoralen adducts with one or both hairpin staples leading to site-specific attachment of the pso-TFO (and attached group) to the origami with ca. 80% efficiency. Bis-adduct formation between strands in proximal hairpins further tethers the TFO to the structure and generates "superstaples" that improve the structural integrity of the functionalized complex. We show that directing cross-linking to regions outside of the origami core dramatically reduces sensitivity of the structures to thermal denaturation and disassembly by T7 RNA polymerase. We also show that the underlying duplex regions of the origami core are digested by DNase I and thus remain accessible to read-out by DNA-binding proteins. Our strategy is scalable and cost-effective, as it works with existing DNA origami structures, does not require scaffold redesign, and can be achieved with just one psoralen-modified oligonucleotide.

Discovery of Borosin Catalytic Strategies and Function through Bioinformatic Profiling.

Borosins are ribosomally synthesized and post-translationally modified peptides (RiPPs) containing backbone α-N-methylations. These modifications confer favorable pharmacokinetic properties including increased membrane permeability and resistance to proteolytic degradation. Previous studies have biochemically and bioinformatically explored several borosins, revealing (1) numerous domain architectures and (2) diverse core regions lacking conserved sequence elements. Due to these characteristics, large-scale computational identification of borosin biosynthetic genes remains challenging and often requires additional, time-intensive manual inspection. This work builds upon previous findings and updates the genome-mining tool RODEO to automatically evaluate borosin biosynthetic gene clusters (BGCs) and identify putative precursor peptides. Using the new RODEO module, we provide an updated analysis of borosin BGCs identified in the NCBI database. From our data set, we bioinformatically predict and experimentally characterize a new fused borosin domain architecture, in which the modified natural product core is encoded N-terminal to the methyltransferase domain. Additionally, we demonstrate that a borosin precursor peptide is a native substrate of shewasin A, a reported aspartyl peptidase with no previously identified substrates. Shewasin A requires post-translational modification of the leader peptide for proteolytic maturation, a feature not previously observed in RiPPs. Overall, this work provides a user-friendly and open-access tool for the analysis of borosin BGCs and we demonstrate its utility to uncover additional biosynthetic strategies within the borosin class of RiPPs.

Transport study on development of fuels and ash density profiles in start-up phase of JA DEMO using TASK code

This study has investigated the effect of particle transport of fuel ions (deuterium (D) and tritium (T)) and helium ash (He) as well as their heat transport on the nuclear fusion output in a DEMO reactor. The result was assessed and possible start-up scenarios for DEMO was discussed. In the study, the integrated tokamak modeling code, TASK/TR is used, and for turbulent transport model, the current diffusive ballooning mode (CDBM) has been utilized to investigate the hydrogen isotope effect on the fusion power output. Also, the effect of He build up has been discussed by introducing the mass-dependent enhancement of He transport. The result has suggested that efficient fueling of D and T to the core region of burning plasma with internal transport barrier is difficult without anomalous inward pinch, and helium build up is significant when only neoclassical and CDBM type of turbulent transport is considered for particle transport.

Non-monotonic thermal conductivity modulation in colloidal quantum dot superlattices via ligand engineering

Colloidal quantum dots (QDs), which consist of inorganic cores surrounded by soft organic ligands, can self-assemble into superlattices exhibiting long-range order. Their tunability, in terms of size, shape, and ligand properties, makes them promising for applications in solar cells, photodetectors, and light-emitting diodes. However, the complex interplay between ligand stiffness, QDs cores-ligands coupling strength, and its impact on QDs' morphology and thermal properties is not well understood. This work employs molecular dynamics simulations to investigate the possibility of modulating the thermal conductivity of QDs superlattices via ligand engineering. It is found that the structural stability of QDs superlattices depends significantly on the interaction strength between the QDs cores and ligands. At lower interaction strengths, the instability manifests itself in a random fusion of the QDs cores, while at intermediate strengths a stable simple cubic lattice structure is maintained. Conversely, higher interaction strengths lead to amorphization in the surface regions of QDs core. We observed a nonlinear trend in the thermal conductivity with varying QD-ligand interaction strengths due to competing factors: fusion of QDs cores at lower interaction strengths and increased crosslinking interaction among ligands at higher interaction strengths. The influence of ligand stiffness on thermal conductivity was found to be minimal. This study provides a deep insight into the role of ligand stiffness and interaction strength on structural dynamics and thermal transport in QDs superlattice and demonstrates the feasibility of engineering thermal transport in QDs superlattice via ligand engineering.

Study on flow atomization characteristics and structure optimization of swirl nozzle for biodiesel

In this paper, the influence of external conditions and structural parameters on the characteristics of a nozzle flow field is studied, and orthogonal tests have been used to optimize the nozzle structure. The results show that the inlet pressure, nozzle aperture, nozzle outlet aspect ratio, vortex chamber height, and screw core height affect the pressure and velocity distributions of the flow field inside the nozzle. With increasing axial distance, the pressure in the inlet area remains unchanged; however, the pressure gradually decreases inside the screw core region and vortex chamber. Meanwhile, the velocity in the nozzle drainage basin first increases and then decreases. With increasing radial distance, the pressure in the nozzle drainage basin gradually increases, whereas the velocity increases first and then decreases. The velocity contour plot and vector diagram of the nozzle outlet section elucidate the influence of structural parameters on the flow field characteristics inside the nozzle. The nozzle length-to-diameter ratio has the greatest effect on the Sauter mean diameter (SMD). Besides, biodiesel atomization is sequentially affected by the vortex chamber height, screw core height, and nozzle aperture. The best atomization performance of biodiesel is observed at a nozzle aperture of 0.8mm, nozzle outlet length-to-diameter ratio of 0, vortex chamber height of 5mm, and screw core height of 4mm. Compared to the original nozzle, the optimized nozzle increases the atomization cone angle of biodiesel by 30.9% and reduces the SMD by 45.3%.