Hot Component Research Articles

Optimization of the hole distribution of an effusively cooled surface facing non-uniform incoming temperature using deep learning approaches

External cooling technologies such as transpiration cooling and effusion cooling are ideal thermal protection strategies for hot section components. Conventional cooling structures were not capable to adaptively fit non-uniform incoming temperature loads due to the limit in modelling and designing tools. The present study established an optimization workflow to adjust the hole distribution of an effusively cooled porous plate. A Conditional Generative Adversarial Neural Network model was developed to model the high dimensional and non-linear mapping between the surface profile and the surface temperature of a series of effusively cooled plates. Computational Fluid Dynamics was utilized to provide data samples for the training of the model. With careful testing and validation of the trained model, the neural network model was integrated with Genetic Algorithms to search for optimal structures that can uniformly cool the plate to a proper temperature level. Results obtained from the modeling efforts indicated a good capability of the neural network model to reconstruct the cooling effectiveness distribution on the external surface of the porous plates. Integrated with this low cost machine learning model, the GA approach successfully identified several optimized structures which fit well with the thermal loads induced by non-uniform incoming gas temperate. Surface temperature variation of the porous plates was reduced by around 50% as compared to the structure with a regular hole array. These attempts of introducing deep learning to external cooling in the present study were successful and future work could further focus on generalization of the modelling and enhancement of the robustness of the optimization approach.

The outburst of the symbiotic star BX Monocerotis in 2019

New outburst of the object BX Mon occurred in the beginning of 2019. The uniqueness of this event lies in its coincidence with the periastron passage by the hot component. This happened for the first time in the history of observations of this object. Previous epochs the moment of periastron passage corresponded to the lower part of the ascending branch of the light curve. Photometric and spectroscopic observations of BX Mon were carried out in the Fesenkov Astrophysical Institute (Republic of Kazakhstan). BVRc magnitudes, absolute fluxes and the profiles of emission lines were obtained. The maximal values B = 9.m7 and V = 9.m3, obtained in the beginning of 2019, are close to those observed during the previous outburst (2003, February). A high level of brightness was maintained until the middle of April. The absolute fluxes in the emission lines Hβ and Hα, obtained during the current outburst, turned out to be significantly weaker compared to the results, obtained in the previous periastron passages. A possible reason of the anomalous decrease of the emission line fluxes is the destruction of the accretion disk - the source of ionizing radiation.

How to add massive neutrinos to your ΛCDM simulation – extending cosmology rescaling algorithms

ABSTRACT Providing accurate predictions for the spatial distribution of matter and luminous tracers in the presence of massive neutrinos is an important task, given the imminent arrival of highly accurate large-scale structure observations. In this work, we address this challenge by extending cosmology-rescaling algorithms to massive neutrino cosmologies. In this way, a ΛCDM simulation can be modified to provide non-linear structure formation predictions in the presence of a hot component of arbitrary mass, and, if desired, to include non-gravitational modifications to the clustering of matter on large scales. We test the accuracy of the method by comparing its predictions to a suite of simulations carried out explicitly including a neutrino component in its evolution equations. We find that, for neutrino masses in the range Mν ∈ [0.06, 0.3] eV the matter power spectrum is recovered to better than $1{{\ \rm per\ cent}}$ on all scales k < 2 h Mpc−1. Similarly, the halo mass function is predicted at a few per cent level over the range Mhalo ∈ [1012, 1015] h−1 M⊙, and so do also the multipoles of the galaxy two-point correlation function in redshift space over r ∈ [0.1, 200] h−1 Mpc. We provide parametric forms for the necessary transformations, as a function of Ωm and Ων for various target redshifts.

Measurements of radial profile of hydrogen and deuterium density in isotope mixture plasmas using bulk charge exchange spectroscopy.

A bulk charge exchange spectroscopy system has been applied to measure the radial profiles of the hydrogen (H) and deuterium (D) density ratio in the isotope mixture plasma in a large helical device. Charge exchange lines of Hα and Dα are fitted by 4 Gaussian of H and D cold components and H and D hot components with 5 parameters by combining the measurement of plasma toroidal rotation velocity with carbon charge exchange spectroscopy. The radial profiles of the relative density of hydrogen and deuterium ions are derived from H and D hot components measured and the beam density calculated from beam attenuation calculation. A proof-of-principle experiment is performed by the H pellet and the D pellet injections into the H-D mixture plasma.

On the relaxed states in the mixture of degenerate and non-degenerate hot plasmas of astrophysical objects

It is shown that a small contamination of a relativistically hot electron component can induce a new scale (for structure formation) to a system consisting of an ion-degenerate electron plasma. Mathematically expression of this additional scale length is the increase in the index of quasi-equilibrium Beltrami-Bernoulli states that have been invoked to model several astrophysical systems of interest. The two species of electrons, due to different origin of their relativistic effective masses, behave as two distinct components (each with its own conserved helicity) and add to the richness of the accessible quasi equilibrium states. Determined by the concrete parameters of the system, the new macro-scale lengths (much larger than the short intrinsic scale lengths (skin depths) and generally much shorter than the system size) open new pathways for energy transformations.

Accurate LBM appraising of pin-fins heat dissipation performance and entropy generation in enclosures as application to power electronic cooling

Purpose The purpose of this paper is to carry out an in-depth analysis of heat dissipation performance by natural convection phenomenon inside light-emitting diode (LED) lamps containing hot pin-fins because of its significant industrial applications. Design/methodology/approach The problem is assimilated to heat transfer inside air-filled rectangular cavity with various governing parameters appraised in ranges interesting engineering application and scientific research. The lattice Boltzmann method is used to predict the dynamic and thermal behaviors. Effects of monitoring parameters such as Rayleigh number Ra (103-106), fin length (0-0.25) and its position, pin-fins number (1-8), the tilting-angle (0-180°) and cavity aspect ratio Ar (0.25-4) are carried out. Findings The rising behaviors of the dynamic and thermal structures and heat transfer rate (Nu), the heatlines distribution and the irreversibility rate are appraised. It was found that the flow is constantly two contra-rotating symmetric cells. The heat transfer is almost doubled by increasing Ra. A lack of cooling performance was identified between Ar = 0.5 and 0.75. The inclination 45° is the most appropriate cooling case. At constant Ra, the maximum stream-function and the global entropy generation remain almost unchanged by increasing the pin number from 1 to 8 and the entropy generation is of thermal origin for low Ra, so that the fluid friction irreversibility becomes dominant for Ra larger than 105. Research limitations/implications Improvements may include three-dimensional complex geometries, accounting for thermal radiation, high unit power and turbulence modelling. Such factors effects will be conducted in the future. Practical implications The cooling performance/heat dissipation in LED lamps is a key manufacturing factors, which determines the lifetime of the electronic components. The best design and installation give the opportunity to increase further the product shelf-life. Originality/value Both cooling performance, irreversibility rate and enclosure configuration (aspect ratio and inclination) are taken into account. This cooling scheme will give a superior operating mode of the hot components in an era where energy harvesting, storage and consumption is met with considerable attention in the worldwide.

Short-term creep behavior of an additive manufactured non-weldable Nickel-base superalloy evaluated by slow strain rate testing

Additive manufacturing (AM) of high γ′ strengthened Nickel-base superalloys, such as IN738LC, is of high interest for applications in hot section components for gas turbines. The creep property acts as the critical indicator of component performance under load at elevated temperature. However, it has been widely suggested that the suitable service condition of AM processed IN738LC is not yet fully clear. In order to evaluate the short-term creep behavior, slow strain rate tensile (SSRT) tests were performed. IN738LC bars were built by laser powder-bed-fusion (L-PBF) and then subjected to hot isostatic pressing (HIP) followed by the standard two-step heat treatment. The samples were subjected to SSRT testing at 850 °C under strain rates of 1 × 10−5/s, 1 × 10−6/s, and 1 × 10−7/s. In this research, the underlying creep deformation mechanism of AM processed IN738LC is investigated using the serial sectioning technique, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM). On the creep mechanism of AM polycrystalline IN738LC, grain boundary sliding is predominant. However, due to the interlock feature of grain boundaries in AM processed IN738LC, the grain structure retains its integrity after deformation. The dislocation motion acts as the major accommodation process of grain boundary sliding. Dislocations bypass the γ′ precipitates by Orowan looping and wavy slip. The rearrangement of screw dislocations is responsible for the formation of subgrains within the grain interior. This research elucidates the short-creep behavior of AM processed IN738LC. It also shed new light on the creep deformation mechanism of additive manufactured γ′ strengthened polycrystalline Nickel-base superalloys.

Comparative Assessment of the Surface Integrity of AD730® and IN718 Superalloys in High-Speed Turning with a CBN Tool

Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys.

NuSTAR and XMM–Newton observations of SXP 59 during its 2017 giant outburst

ABSTRACT The Be X-ray pulsar (BeXRP) SXP 59 underwent a giant outburst in 2017 with a peak X-ray luminosity of 1.1 × 1038 erg s−1. We report on the X-ray behaviour of SXP 59 with the XMM–Newton and NuSTAR observations collected at the outburst peak, decay, and the low luminosity states. The pulse profiles are energy dependent, the pulse fraction increases with the photon energy and saturates at 65 per cent above 10 keV. It is difficult to constrain the change in the geometry of emitting region with the limited data. Nevertheless, because the pulse shape generally has a double-peaked profile at high luminosity and a single peak profile at low luminosity, we prefer the scenario that the source transited from the super-critical state to the sub-critical regime. This result would further imply that the neutron star (NS) in SXP 59 has a typical magnetic field. We confirm that the soft excess revealed below 2 keV is dominated by a cool thermal component. On the other hand, the NuSTAR spectra can be described as a combination of the non-thermal component from the accretion column, a hot blackbody emission, and an iron emission line. The temperature of the hot thermal component decreases with time, while its size remains constant (R ∼ 0.6 km). The existence of the hot blackbody at high luminosity cannot be explained with the present accretion theories for BeXRPs. It means that either more sophisticated spectral models are required to describe the X-ray spectra of luminous BeXRPs, or there is non-dipole magnetic field close to the NS surface.

Absolute properties of RU Cnc revisited: an active RS CVn-type eclipsing binary with red giant branch and main-sequence components

ABSTRACT We present observations and analysis of an RS CVn-type double-lined eclipsing binary system, RU Cnc. The system has been observed for over a century. High-quality long-cadence observations, newly obtained from the Kepler K2 C5 and C18 campaigns, and two radial velocity curves were combined and analysed simultaneously, assuming a multispot model. The masses, radii and luminosities of the component stars have been precisely obtained as $M_\textrm{c} = 1.386\pm 0.044\, \mathrm{M}_{\odot }$, $M_\textrm{h} = 1.437 \pm 0.046\, \mathrm{M}_{\odot }$, $R_\textrm{h} = 2.39\pm 0.07\, \mathrm{R}_{\odot }$, $R_\textrm{c} = 5.02 \pm 0.08\, \mathrm{R}_{\odot }$, $L_\textrm{h} = 11.4\pm 1.2\, \mathrm{L}_{\odot }$ and$L_\textrm{c} = 12.0 \pm 1.0\, \mathrm{L}_{\odot }$, with a separation of $a = 27.914 \pm 0.016\, \mathrm{R}_{\odot }$. The distance of the system is determined to be $380\pm 57\,$ pc, which is consistent with the Gaia Data Release 2 result. Long-term detailed period variation analysis of the system indicates a period decrease of 7.9 × 10−7 d yr–1. The results suggest that the cooler component is on the red giant branch (RGB) and the hotter component is still on the main sequence.

Growth Rates of the Electrostatic Waves in Radio Zebra Models

Abstract Zebras were observed not only in the solar radio emission but also in radio emissions of Jupiter and the Crab Nebula pulsar. In their models, growth rates of the electrostatic waves play an important role. Considering the plasma composed from the thermal background plasma and hot and rare component with the Dory–Guest–Harris distribution, we compute the growth rates γ and dispersion branches of the electrostatic waves in the ω − k ⊥ domain. We show complexity of the electrostatic wave branches in the upper-hybrid band. In order to compare the results, which we obtained using the kinetic theory and particle-in-cell (PIC) simulations, we define and compute the integrated growth rate Γ, where the “characteristic width” of dispersion branches was considered. We found a very good agreement between the integrated growth rates and those from PIC simulations. For maximal and minimal Γ we showed locations of dispersion branches in the ω − k ⊥ domain. We found that Γ has a maximum when the dispersion branches not only cross the region with high growth rates γ, but when the dispersion branches in this region are sufficiently long and wide. We also mentioned the effects of changes in the background plasma and hot component temperatures.

Dust Acoustic Solitary Waves in a Five Component Plasma-Application to Comets

We have studied the characteristics of the Dust Acoustic Solitary Wave (DASW) in a five component cometary plasma composed of two components of electrons (one hotter and one colder), hydrogen ions and a pair of oppositely charged dust particles (heavier ions). The Korteweg – deVries wave equation has been derived for the system and its solitary wave solution obtained. The dust acoustic solitary wave amplitude is almost a constant with varying temperatures of the hot electron component but decreases with increasing hydrogen ion densities. A comparison with a complementary nonlinear wave, the Dust Ion Acoustic Solitary Wave, has also been made. Keywords: Dust acoustic solitary wave, K dV equation, kappa distributed ions and electrons Cite this Article Neethu Theresa Willington, Sijo Sebastian, Chandu Venugopal. Dust Acoustic Solitary Waves in a Five Component Plasma-Application to Comets. Research & Reviews: Journal of Physics . 2019; 8(2): 44–51p.

Hot Corrosion Behavior and Mechanism of High-Velocity Arc-Sprayed Ni-Cr Alloy Coatings

High-temperature corrosion affects many components used in coal-fired power plants. A possible solution is the use of protective coatings. In this study, Ni-Cr alloy coatings with different Cr contents (30 at.%, 45 at.%, and 50 at.%) and Ni-Cr-Ti coatings were deposited on 20G boiler steels by high-velocity arc spraying. The hot corrosion behavior of the coatings was characterized in the aggressive environment of Na2SO4 + 30% K2SO4 molten salt under cyclic conditions at 750°C. x-Ray diffraction analysis, optical microscopy, and scanning electron microscopy were used to analyze the phase composition, microstructure, and corrosion products of the coatings. The corrosion kinetic curves of the coatings, established by thermogravimetry, conformed to the classic parabolic law, revealing that the Ni-Cr-Ti coatings exhibited better hot corrosion resistance than the Ni-45Cr or Ni-30Cr coatings. However, among the four tested coatings, the Ni-50Cr coating was found to offer the best protection with the lowest values of mass gain per area (2.9 mg/cm2) and parabolic rate constant (kp, 0.215 × 10−11 g2 cm−4 s−1). This can be explained by the formation of Cr2O3 and NiCr2O4. Therefore, such high-velocity arc-sprayed Ni-50Cr coatings could be used as protective layers for hot components in boiler tubes.

Disk origin of the Milky Way bulge: the necessity of the thick disk

In the Milky Way bulge, metal-rich stars form a strong bar and are more peanut-shaped than metal-poor stars. It has recently been claimed that this behavior is driven by the initial (i.e., before bar formation) in-plane radial velocity dispersion of these populations, rather than by their initial vertical random motions. This has led to the suggestion that a thick disk is not necessary to explain the characteristics of the Milky Way bulge. We discuss this issue again by analyzing two dissipationless N-body simulations of boxy or peanut-shaped bulges formed from composite stellar disks that consist of kinematically cold and hot stellar populations. These two models represent two extreme cases: one where all three components of the disk have a fixed vertical velocity dispersion and different in-plane radial dispersion, and another where they all have a fixed radial dispersion and different vertical random motions (thickness). This is intended to quantify the drivers of the main features that are observed in composite boxy or peanut-shaped bulges and their origin. We quantify the mapping into a boxy or peanut-shaped bulge of disk populations in these two cases, and we conclude that initial vertical random motions are as important as in-plane random motions in determining the relative contribution of cold- and hot-disk populations with height above the plane, the metallicity and age trends. Previous statements emphasizing the dominant role of in-plane motions in determining these trends are not confirmed. However, significant differences exist in the morphology and strength of the resulting boxy or peanut-shaped bulges. In particular, the model where disk populations initially have only different in-plane random motions, but similar thickness, results in a boxy or peanut-shaped bulge where all populations have a similar peanut shape, independent of their initial kinematics or metallicity. This is at odds with the trends observed in the Milky Way bulge. We discuss the reasons behind these differences, and also predict the signatures that these two extreme initial conditions would leave on the vertical age and metallicity gradients of disk stars outside the bulge region. As a consequence of this analysis, we conclude that given our current knowledge of the Milky Way bulge and of the properties of its main stellar components, a metal-poor, kinematically (radial and vertical) hot component, that is, a thick disk, is necessary in the Milky Way before bar formation. This supports the scenario that has been traced in previous works. Boxy or peanut-shaped bulges and their surrounding regions are fossil records of the conditions present at early times in disk galaxies, and by dissecting their stellar components by chemical compositions and/or age, it may be possible to reconstruct their early state.

Conjugate heat transfer modeling of a turbine vane endwall with thermal barrier coatings

ABSTRACTAdvanced cooling techniques involving internal enhanced heat transfer and external film cooling and thermal barrier coatings (TBCs) are employed for gas turbine hot components to reduce metal temperatures and to extend their lifetime. A deeper understanding of the interaction mechanism of these thermal protection methods and the conjugate thermal behaviours of the turbine parts provides valuable guideline for the design stage. In this study, a conjugate heat transfer model of a turbine vane endwall with internal impingement and external film cooling is constructed to document the effects of TBCs on the overall cooling effectiveness using numerical simulations. Experiments on the same model with no TBCs are performed to validate the computational methods. Round and crater holes due to the inclusion of TBCs are investigated as well to address how film-cooling configurations affect the aero-thermal performance of the endwall. Results show that the TBCs have a profound effect in reducing the endwall metal temperatures for both cases. The TBC thermal protection for the endwall is shown to be more significant than the effect of increasing coolant mass flow rate. Although the crater holes have better film cooling performance than the traditional round holes, a slight decrement of overall cooling effectiveness is found for the crater configuration due to more endwall metal surfaces directly exposed to external mainstream flows. Energy loss coefficients at the vane passage exit show a relevant negative impact of adding TBCs on the cascade aerodynamic performance, particularly for the round hole case.

AAV-mediated siRNA against TRPV1 reduces nociception in a rat model of bone cancer pain

ABSTRACTObjective: Bone cancer pain is characterized by moderate to severe ongoing pain that commonly requires the use of opiates. Transient receptor potential vanilloid subfamily member 1 (TRPV1), a new target of the analgesics, activated by heat, protons and capsaicin and the hot component of pepper. However, little is known of the anti-nociceptive effects of TRPV1 in cancer-induced bone pain. RNA interference (RNAi) has proven to be a powerful technique to study the function of genes by producing knock-down phenotypes. The aim of this study is to investigate the potential role of TRPV1 in rat model of bone cancer pain.Methods: Bone cancer pain animal model was created by tumor cell implantation (TCI). An AAV-mediated siRNA against TRPV1 was intrathecally delivered into the rats. Animal behaviors were measured using a set of mechanical or electronic von Frey apparatus and hot plate. mRNA and protein expression were examined by using qPCR and western blot methods.Results: Mechanical threshold and paw withdrawal latency in response to thermal stimulation were significantly elevated in rats with intrathecal administration of AAV-mediated siRNA against TRPV1. Moreover, class I histone deacetylases (HDACs), which plays a critical role in the neuro-inflammation response, and TNFα in the spinal cord were also significantly suppressed upon knockdown of TRPV1 by AAV-mediated siRNA against TRPV1 in rat spinal cord.Conclusions: Knockdown of TRPV1 effectively ameliorated mechanical allodynia and thermal hyperalgesia induced by TCI. Our data demonstrated that modulate the expression of TRPV1 in the spinal cord could be a potential therapeutic approach for bone cancer pain.

Evolution of Microstructure and Mechanical Characteristics in Rejuvenation of a Hot Gas Pass Component of a Gas Turbine by Heat Treatment and HIP

The evolution of microstructure and mechanical characteristics during the rejuvenation of a hot gas pass component of a gas turbine was investigated with an actual service-exposed bucket in a power plant. Heat treatment and hot isostatic pressing processes were conducted to rejuvenate a hot gas pass component of a F class gas turbine which had been operated for 101.15% of its expected lifetime. In the three step heat treatment, the specimens were exposed to 1210 ℃, 1120 ℃, and 845 ℃ for periods of 2 h, 2 h, and 24 h, respectively, with rapid cooling. Then, the specimens were exposed to conditions of 1200 ℃ and 100 MPa for 4 h to enhance their integrity. Analysis of the microstructure determined that after heat treatment the average size of γ' decreased around 60 μm, while the area fraction of γ' increased around 20% compared to before heat treatment. With respect to mechanical characteristics, the samples’ stress-rupture time, yield strength, and ultimate strength improved with heat treatment and hot isostatic pressing, while hardness did not show any meaningful variation. These phenomenological results suggest that heat treatment and hot isostatic pressing play a critical role in the rejuvenation of a hot gas pass component, and can provide an operating and maintenance strategy to enhance the economic feasibility of a combined cycle power plant. Key words: heat treatment, gas turbine blade, hot gas pass component, hot isostatic pressing

Detection of anti-correlation of hot and cold baryons in galaxy clusters

The largest clusters of galaxies in the Universe contain vast amounts of dark matter, plus baryonic matter in two principal phases, a majority hot gas component and a minority cold stellar phase comprising stars, compact objects, and low-temperature gas. Hydrodynamic simulations indicate that the highest-mass systems retain the cosmic fraction of baryons, a natural consequence of which is anti-correlation between the masses of hot gas and stars within dark matter halos of fixed total mass. We report observational detection of this anti-correlation based on 4 elements of a 9 × 9-element covariance matrix for nine cluster properties, measured from multi-wavelength observations of 41 clusters from the Local Cluster Substructure Survey. These clusters were selected using explicit and quantitative selection rules that were then encoded in our hierarchical Bayesian model. Our detection of anti-correlation is consistent with predictions from contemporary hydrodynamic cosmological simulations that were not tuned to reproduce this signal.

Study on the thermo-mechanical-metallurgical couple model of tailored hot stamping

ABSTRACTIn order to predict the microstructures and hardness evolution of tailored hot stamping (THS) component, a thermo-mechanical-metallurgical couple finite element model was established. In particular, the activation energies for ferrite and bainite in the model were optimised. THS experiment of U-shape component with segmented heating and cooling was also performed to compare the hardness distribution and phase change with numerical simulation. The results showed that the original model and the activation energy optimised model can both be used to predict the microstructures and hardness evolution for hot stamping components with full martensite. As for THS component, the effect of cooling path and deformation on the activation energies of phase transformation should be considered.

Saturation Properties of Whistler Wave Instability in a Plasma With Two Electron Components

AbstractSaturation properties of whistler wave instability driven by electron temperature anisotropy in a plasma with two electron components are investigated using particle‐in‐cell (PIC) simulations. Most of the previous self‐consistent PIC simulations or quasi‐linear theory used a single bi‐Maxwellian distribution of electrons, which might apply to solar wind or magnetosheath. In the inner magnetosphere, however, there is frequently a cold and dense electron component, coexisting with a hot electron component. In this work, we investigate the relation between temperature anisotropy (A) and parallel plasma beta (β‖) at saturation. Our results agree well with the previous conclusion obtained from linear theory in most cases. However, We show that the inverse relation breaks when β‖ is larger than certain value , beyond which A increases with increasing β‖. We also investigated the dependence of the saturation wave intensity on plasma beta and the initial linear growth rate and show that the saturation amplitude can be modeled as a function of the maximum initial linear growth rate even in a plasma with two electron components. Our results might be useful to couple the microscopic wave excitation process with macroscopic global energetic electron dynamics and to understand whistler wave excitation in the inner magnetosphere.