High Temperature End Research Articles

Directed crystalline symmetry transformation of blue-phase liquid crystals by reverse electrostriction

Soft-matter-based photonic crystals like blue-phase liquid crystals (BPLC) have potential applications in wide-ranging photonic and bio-chemical systems. To date, however, there are limitations in the fabrication of large monocrystalline BPLCs. Traditional crystal-growth process involves the transition from a high-temperature disordered phase to an ordered (blue) phase and is generally slow (takes hours) with limited achievable lattice structures, and efforts to improve molecular alignment through post-crystallization field application typically prove ineffective. Here we report a systematic study on the molecular self-assembly dynamics of BPLC starting from a highly ordered phase in which all molecules are unidirectionally aligned by a strong electric field. We have discovered that, near the high-temperature end of the blue phase, if the applied field strength is then switched to an intermediate level or simply turned off, large-area monocrystalline BPLCs of various symmetries (tetragonal, orthorhombic, cubic) can be formed in minutes. Subsequent temperature tuning of the single crystal at a fixed applied field allows access to different lattice parameters and the formation of never-before-seen monoclinic structures. The formed crystals remain stable upon field removal. The diversity of stable monocrystalline BPLCs with widely tunable crystalline symmetries, band structures, and optical dispersions will significantly improve and expand their application potentials.

Tunable noninteracting free-energy density functionals for high-energy-density physics applications

In this work, we introduce the concept of a tunable noninteracting free-energy density functional and present two examples realized: (i) via a simple one-parameter convex combination of two existing functionals and (ii) via the construction of a generalized gradient approximation (GGA) enhancement factor that contains one free parameter and is designed to satisfy a set of incorporated constraints. Functional (i), constructed as a combination of the local Thomas–Fermi and a pseudopotential-adapted GGA for the noninteracting free-energy, has already demonstrated its practical usability for establishing the high temperature end of the equation of state of deuterium [Phys. Rev. B 104, 144104 (2021)] and CHON resin [Phys. Rev. E 106, 045207 (2022)] for inertial confinement fusion applications. Hugoniot calculations for liquid deuterium are given as another example of how the application of computationally efficient orbital-free density functional theory (OF-DFT) can be utilized with the employment of the developed functionals. Once the functionals have been tuned such that the OF-DFT Hugoniot calculation matches the Kohn–Sham solution at some low-temperature point, agreement with the reference Kohn–Sham results for the rest of the high temperature Hugoniot path is very good with relative errors for compression and pressure on the order of 2% or less.

Temperature-driven coupled transport of pollutants and suspended particles established by granular thermodynamics

The temperature-driven effects on pollutant transport are significant, including thermal diffusion of pollutants, thermal osmosis of solutions, thermal motion of suspended particles, and other deformation and transformation processes. The pollutant seepage field equation was derived based on granular thermodynamics, and the motion equation of suspended particles was derived from Newton's second law. A comprehensive coupled transport model for the two-phase flow of pollutants and suspended particles in saturated porous media was established, which can effectively consider the impact of temperature driving. The model accurately described the coupled transport process of pollutants and suspended particles under different temperatures and particle sizes during single-pulse injection. Furthermore, the application of this model in natural clay layers under varying temperature gradients was discussed. The results indicated that, for the same time, an increase in temperature at the high-temperature end led to a 36.5 % decrease in the peak concentration of pollutant transport. When the temperature difference was significant, thermal osmosis and thermal motion were the main mechanisms for the coupled transport of pollutants and suspended particles, with the diffusion mechanism induced by concentration and temperature gradients not dominating. Thermal diffusion positively drove the transport of pollutants, while thermal osmosis and thermal motion under temperature gradients had a reverse inhibitory effect on pollutant transport.

Effect of temperature on interface debonding behavior of graphene/graphene-oxide on cement-based composites

Temperature effect easily affect the adhesion of graphene/graphene oxide (GO) on the cement-based composites originating from the weaker non-covalent bonding at the interface, leading to weakening of the cementitious composite properties. In this study, the interfacial debonding behavior of graphene/GO and cement-based composites was investigated for low to high temperatures (250∼550 K) using controlled molecular dynamics simulations. The maximum tensile force and work of adhesion both decrease with increasing temperature, and the value of GO is 5∼6 times that of graphene. Especially at the high temperature end, GO is still difficult to peel off (Fmax: 7.93×103 pN, Wmax:2129.60 Kcal/mol). Meanwhile, the insights into the distribution and concentration of functional groups have shown that high concentrations and edge functional groups can improve interface adhesion. Energy decomposition demonstrated that, compared to the Coulomb effect of charge and the prestress of surface wrinkles, the van der Waals effect plays a major role in interface adhesion. Entropy analysis further reveals the high temperature sensitivity of graphene and the low sensitivity of GO due to edge functional groups. We believe that the insight into the temperature effect of interface debonding behavior at nanoscale can provide theoretical support for the effective temperature working conditions of graphene/graphene-oxide on cement-based composites.

Probing the electron trap-depth distribution in Sr4Al14O25:Eu2+,Dy3+

Sr4Al14O25:Eu2+,Dy3+ is a superluminous persistent luminescence phosphor. Owing to its intrinsic and extrinsic point defects, it tends to luminescence incessantly after excitation, in some cases doing so for as long as 20 h. We report analysis for the energy distribution of its electron traps. The study was done using thermoluminescence (TL) measured on a sample irradiated to 2 Gy at 20 °C. A glow curve measured at 1 °C/s shows two glow peaks at 64 °C (labelled as P1) and at 252 °C (P2). The variation of intensity of peak P1 as a function of heating rate is consistent with competing radiative and non-radiative recombination processes. When the heating rate is faster than 1 °C/s, non-radiative recombinations dominate and the luminescence efficiency drops sharply beyond 70 °C. The activation energy for thermal quenching is estimated to be 0.69±0.06 eV. Once corrected for thermal quenching, the glow curves show a secondary peak (P1A) on the high temperature end of P1. The so-called Tm-Tstop method shows that peaks P1 and P2 gradually shift towards high temperature with preheating temperature Tstop. Indeed, the peak position Tm of both peaks increases with irradiation temperature Tirr. Together, these results suggest that peaks P1 and P2 are each composed of closely spaced overlapping peaks. Analysis of the fractional area between a pair of glow curves measured from the sample irradiated at different temperatures (Tirr) shows that the trap distribution associated with peak P2 is Gaussian whereas that associated with peak P1 follows a non-Gaussian distribution. The activation energy of the electron traps responsible for P1 are estimated to be in the range 0.63–0.68 eV. On the other hand, the Gaussian distribution of trap energy levels responsible for peak P2 suggests that most of the traps have an activation energy of ∼1.58 eV.

Assessment of the Structural Integrity of a Laser Weld Joint of Inconel 718 and ASS 304L

For high-temperature industries operating at nearly 750 °C (advanced ultra-super critical boilers), dissimilar welding between Inconel alloys and austenitic stainless steel (ASS) are commonly adopted. The high-temperature resistive properties of Inconel and ASS alloys are highly qualified for high-temperature applications. In this experimental study, dissimilar autogenous laser beam welding (LBW) between Inconel 718 and ASS 304L is investigated. This paper explains the detailed study on the microstructural and mechanical behavior of the LBW dissimilar joint. The microstructural study indicates the presence of laves phases in the weld zone. Additionally, the weld zone shows heterogeneous microstructural formation, owing to the non-uniform welding heat in the different areas of the weld zone. The optical images show the presence of mixed dendrites, i.e., equiaxed, cellular, and columnar morphology, in the weld zone and in the fusion zones of either side. The energy-dispersive spectroscopy (EDS) results show the presence of segregated elements (Nb, Mo, Cr, and Ti) at the weld center. These segregated elements are the reason for the occurrence of the laves phases in the weld zone. The presence of Nb and Mo may form the laves phase (Fe, Ni, Cr)2 (Nb, Mo, Ti) along with Fe, Ni and Cr. The presence of an unmixed zone is observed in the HAZ of the Inconel 718, whereas the HAZ of the ASS 304L shows the presence of an unmixed zone (UZ) and a partially mixed zone (PMZ), as observed on the optical and SEM images. To obtain the mechanical properties of the laser weld, the tensile test, microhardness test, and impact test were measured at room temperature. The tensile specimens show a brittle failure at the ASS 304L side, which was initiated from the weld top, with average tensile stress of 658.225 MPa. The reason for the ASS 304L fracture is because of the presence of UZ and PMZ, and the lower hardness value of the ASS side. The UZ and PMZ lead to the fracture of the tensile specimen along the ASS 304L side’s HAZ. The measurement of microhardness carried out along the transverse length indicates an average microhardness of 214.4 HV, and the value is 202.9 HV along the weld depth. The mixed morphology of the microstructure promotes the variation in hardness in both directions. The hardness along the length shows a high hardness value in the weld zone and uniformly decreases along the base materials. The Charpy impact test of the weld zone shows the brittle fracture of the impact specimens. From the microstructural and mechanical results, the LBW dissimilar weld between Inconel 718 and ASS 304L is qualified for safe use in high-temperature end applications, such as AUSC power plants.

Persistent Cyanobacteria Blooms in Artificial Water Bodies-An Effect of Environmental Conditions or the Result of Anthropogenic Change.

Algal blooms are an emerging problem. The massive development of phytoplankton is driven partly by the anthropogenic eutrophication of aquatic ecosystems and the expansion of toxic cyanobacteria in planktonic communities in temperate climate zones by the continual increase in global temperature. Cyanobacterial harmful algal blooms (CyanoHABs) not only disturb the ecological balance of the ecosystem, but they also prevent the use of waterbodies by humans. This study examines the cause of an unusual, persistent bloom in a recreational, flow-through reservoir; the findings emphasize the role played by the river supplying the reservoir in the formation of its massive cyanobacterial bloom. Comprehensive ecosystem-based environmental studies were performed, including climate change investigation, hydrochemical analysis, and bio-assessment of the ecological state of the river/reservoir, together with monitoring the cyanobacteria content of phytoplankton. Our findings show that the persistent and dominant biomass of Microcystis was related to the N/P ratio, while the presence of Aphanizomenon and Dolichospermum was associated with the high-temperature end electric conductivity of water. Together with the increase in global temperature, the massive and persistent cyanobacterial bloom appears to be maintained by the inflow of biogenic compounds carried by the river and the high electric conductivity of water. Even at the beginning of the phenomenon, the reservoir water already contained cyanobacterial toxins, which excluded its recreational use for about half the year.

Study of the reduction of the onset temperature in a loop-tube-type thermoacoustic prime mover using conical phase adjuster.—Based study on the installation position and onset temperature of conical phase adjuster

In this report, we proposed the installation of a conical phase adjuster (CPA) in a thermoacoustic prime mover as a method for reducing the onset temperature and investigated the effect of the installation position of a CPA on the onset temperature using stability analysis. The onset temperature of CPA also was investigated experimentally by changing the installation position of CPA. As a result, when CPA was installed at 1000 mm from the high-temperature end of the stack, the onset temperature was 195 K lower than the onset temperature without CPA, that is, the installation of the CPA in a loop-tube-type thermoacoustic prime mover reduced the onset temperature by 29%. Comparing onset temperatures of the PA had installed in a system, CPA is considered to have the same effect as a PA because the onset temperature tendency of the CPA to reduce at the installation position agrees with that of the PA.

Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 ternary ceramics with temperature-insensitive and superior piezoelectric property

The development of ferroelectric ceramics with both large piezoelectric responses and broad service temperature range is still a key challenge for practical applications due to the so-called d33-TC trade-off. Here we report the strategy to utilize the synergistic contribution of morphotropic phase boundary and enhanced local structural heterogeneity, in which an excellent piezoelectric coefficient d33 of 680 pC/N and a high Curie temperature of 330 ℃ are simultaneously achieved in Sm modified 0.25PIN-0.325PZ-0.425PT ceramics. The underlying mechanism responsible for the high dielectric and piezoelectric properties is studied based on cryogenic dielectric measurement and Rayleigh analysis. Of particular interest is that, a high field-induced strain of 0.19% is achieved in 0.25PIN-0.32PZ-0.43PT at electric field of 20 kV/cm, corresponding to a piezoelectric d33 * of 945 pm/V, showing an excellent temperature stability with minimal variation of 7% up to 310 °C. This work demonstrates the introduction of high temperature end members and rare earth doping are conducive to ferroelectric solid solutions with desired broad usage temperature range and superior piezoelectric properties, which will greatly benefit high temperature actuator applications.

J-PLUS: Spectral evolution of white dwarfs by PDF analysis

Aims. We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), which provides 12 photometric optical passbands over 2176 deg2. Methods. We analyzed 5926 white dwarfs with r ≤ 19.5 mag in common between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We performed a Bayesian analysis by comparing the observed J-PLUS photometry with theoretical models of hydrogen- and helium-dominated atmospheres. We estimated the probability distribution functions for effective temperature (Teff), surface gravity, parallax, and composition; and the probability of having a H-dominated atmosphere (pH) for each source. We applied a prior in parallax, using Gaia EDR3 measurements as a reference, and derived a self-consistent prior for the atmospheric composition as a function of Teff. Results. We described the fraction of white dwarfs with a He-dominated atmosphere (fHe) with a linear function of the effective temperature at 5000 < Teff < 30 000 K. We find fHe = 0.24 ± 0.01 at Teff = 10 000 K, a change rate along the cooling sequence of 0.14 ± 0.02 per 10 kK, and a minimum He-dominated fraction of 0.08 ± 0.02 at the high-temperature end. We tested the obtained pH by comparison with spectroscopic classifications, finding that it is reliable. We estimated the mass distribution for the 351 sources with distance d < 100 pc, mass M > 0.45 M⊙, and Teff > 6000 K. The result for H-dominated white dwarfs agrees with previous studies, with a dominant M = 0.59 M⊙ peak and the presence of an excess at M ∼ 0.8 M⊙. This high-mass excess is absent in the He-dominated distribution, which presents a single peak. Conclusions. The J-PLUS optical data provide a reliable statistical classification of white dwarfs into H- and He-dominated atmospheres. We find a 21 ± 3% increase in the fraction of He-dominated white dwarfs from Teff = 20 000 K to Teff = 5000 K.

High-temperature monolithic SiGe thermoelectric device directly heated by catalytic combustion

There has been a strong demand for portable power sources of mobile devices, which can substitute conventional lithium-ion batteries. In this study, a thermoelectric power generation device integrated with a catalytic combustor was developed in order to overcome limitations of previously proposed combustion-based system, such as low temperature difference and large heat loss. Monolithic SiGe thermoelectric generators (TEGs) with operating temperatures higher than 1100 °C were prepared, and Pd catalyst layers supported by porous alumina films were formed on the high-temperature end of the SiGe TEG device for direct heating obtained by catalytic combustion while minimizing the heat loss. A power generation test bench was developed with three SiGe devices. By using a butane/air mixture, the highest temperature and temperature difference over 1100 °C and 800 °C, respectively, were achieved without deterioration of the power generation performance.

Modeling flow stress and grain size of GCr15 bearing steel at high-temperature deformation near end of solidification

Modeling flow stress and grain size of GCr15 bearing steel at high-temperature deformation near end of solidification

Experimental Study on Tribological Properties of Polymer-based Composite Nano-additives Suitable for Armored Vehicle Engine Lubricating Oil

Lubricating oil is known as "the blood to maintain the normal operation of machinery", and additives are an indispensable and important part of lubricating oil. In this paper, the Polymer-based Composite Nano-additive (PCNA) suitable for armored vehicle engine lubricating oil was developed, the physical and chemical properties of lubricating oil containing additives were carried out. The results showed that adding an appropriate amount (3 vol.%) of additives could improve the low-temperature fluidity of lubricating oil and improve the kinematic viscosity of lubricating oil without affecting the viscositytemperature characteristics of lubricating oil. The four-ball testing machine, high temperature end face testing machine and engine bench are used to measure the anti-friction lubrication effect and anti-wear ability improvement effect of the additive on lubricating oil. The experimental results show that the additive can effectively improve the antifriction, lubrication and anti-wear performance of lubricating oil. In addition, the addition of the additive can effectively improve the running state of the engine, and the engine noise is obviously reduced. Finally, the additives developed in this paper are compared with three common brand additives in the market by using the high temperature end face testing machine. The results show that the additive developed in this paper has certain advantages in improving the antifriction and lubrication effect of lubricating oil.

Research progress of large diamond single crystals under high pressure and high temperature

Diamond has a series of extreme characteristics superior to other materials, and also very wide application scope. The large diamond single crystal can play a role in its functional characteristics, which has become a research hotspot. In this paper, we introduce the principle and process of synthesizing large diamond single crystal by temperature gradient method (TGM) under high pressure and high temperature (HPHT), and summarizes the research status and research directions of different types of and additives-doped large diamond single crystals respectively. The principle of the temperature gradient method is that the carbon source, driven by the temperature gradient, diffuses from the high concentration region at the high temperature end to the low concentration region at the low temperature end, and diamonds are grown on the seed crystal. The growth rate of diamond crystal is controlled by adjusting the axial temperature gradient at synthesis cell, and the shape growth of Ib-type large diamond is controlled by the distribution in the V-shaped growth area. We introduce different kinds of diamond large single crystals from five aspects. Firstly, the Ia-type diamond large single crystal can be obtained by the annealing treatment of Ib-type diamond under HPHT. The conversion rate of C centre to A centre for nitrogen in diamond is improved by optimizing the conditions of HPHT. Secondly, the Ib-type larger diamond is studied very much in the following areas: the analysis of its surface characteristic, the control of inclusions and cracks, the precipitation mechanism and the elimination measures of regrown graphite and the mass production technology of multiseed method. Thirdly, IIa-type large diamond single crystal is introduced in which the nitrogen getter is selected due to the ability Al and Ti (Cu) to getter nitrogen, the catalyst is selected because of its effect on the nitrogen content in the diamond synthesized with Fe or Ni based catalyst, and the elimination method of microcrystalline graphite precipitation is presented by analyzing its mechanism. Fourthly, the boron elements exist in IIb-type diamond and have influence on the growth characteristics of synthetic diamond. Fifthly, introduced is the research status of diamond synthesized with B, N, S, P doping elements, in which its individual substance or their compound is used as a doping source or boron and other elements with small radius are used as co-doping agent. Then S or P with B co-doping is more conducive to the improvement of the performance of n-type diamond large single crystal semiconductor. Therefore, it is proposed that the large diamond single crystal need strengthening in mass production of IIa-type large diamond single crystal, superconducting characteristics of IIb-type large diamond single crystal, and doping of n-type semiconductors.

Low thermal budget lead zirconate titanate thick films integrated on Si for piezo-MEMS applications

Piezoelectric cantilevers made from ferroelectric thick films are commonly used as key components in many prototypical piezo-MEMS devices, including sensors, micro-actuators and piezoelectric energy harvesters. In this work, transverse piezoelectric performance of rapid thermal annealed Pb(Zr0.53Ti0.47)O3 (PZT) thick film (~1-2 μm) were characterized. These films were sputtered on LaNiO3 buffered Pt/Ti/SiO2/(100) Si substrates at 350 °C followed by a rapid thermal process (RTP) with different annealing time (30 s to 15 min) at the high temperature end (700 °C), and then patterned into rectangular prism-shaped cantilevers. Such a two-step process yields highly (001)-oriented perovskite PZT films with good overall electrical properties (ferroelectric, dielectric and piezoelectric) close to those of an epitaxial PZT film, yet on a much reduced thermal budget. With the elementary and chemical valence information from EDS and XPS analysis, an optimal annealing time was determined for the PZT thick film cantilevers to have both an outstanding piezoelectric performance (actuating, sensing or energy harvesting), and a good compatibility with the Si technology (a brief exposure to a high temperature). This study promotes the integration of large piezoelectricity into Si-based MEMS.

Multistep spin-crossover transitions induced by the interplay between short- and long-range interactions with frustration on a triangular lattice

We investigate the phase diagram of an elastic interaction model for spin crossover (SC) materials on a triangular lattice, in which the long-range (LR) interaction of elastic origin, antiferromagnetic-like nearest-neighbor (NN) interaction ${J}_{1}$, and ferromagnetic (F)-like next-NN interaction ${J}_{2}$ interplay nontrivially. We find that for relatively weak elastic interactions in the model, two critical lines with the three-state Potts universality and the Berezinskii-Kosterlitz-Thouless (BKT) phase line merge at the BKT high temperature end point at zero effective field $H=0$. In contrast, for relatively large elastic interactions, the two critical lines and the coexistence line between the ferrimagnetic (FR)-like phases merge at a critical end point at $H=0$. The phase diagrams are also characterized by tricritical points, at which F-like spinodal, FR-like spinodal, and critical lines merge, and the metastable regions of the F-like and FR-like phases expand for stronger elasticity. We also find that, in the model with only the NN interaction ${J}_{1}$, for relatively weak elastic interactions, the critical end point is located at a very low temperature, the disordered phase appears at low temperatures, and the metastable regions of the F-like and FR-like phases are very small. The SR interactions are relevant for the critical lines, while the spinodal lines are caused by the LR interaction of elastic origin, which is independent of the strength of elasticity. Making use of these phase diagrams with the different characteristics, we show a wide variety of SC transitions with one to four steps, in which a second-order (continuous), first-order (discontinuous), or BKT (continuous) transition can occur at each step.

Effects of solidification defects on nanoscale mechanical properties of rapid directionally solidified Al-Cu Alloy: A large scale molecular dynamics study

Directional solidification of Al-11 at % Cu is investigated by molecular dynamics (MD) simulations utilizing second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potential. The condition for directional solidification is produced by imposing dissimilar temperatures at the model boundaries along the [1 0 0] solidification direction to create a temperature gradient. During solidification, the solid-liquid front travels through the Al-Cu liquid along the [1 0 0] direction towards the high temperature end. At the initial stages of solidification, several solidification defects such as twins, stacking faults, and grain boundaries form. As directional solidification progresses, grains elongate along the solidification direction, and at the final stages of solidification no new defects or grain boundaries form. The elongated grain boundaries form a few layers with lamellar like structures along [1 0 0]. When the solidified polycrystalline is deformed in the [0 0 1] direction, glide of partial dislocations happen around the grain boundaries, whereas during elongation along [1 0 0] some defects from in the Al-Cu matrix. Since formation of defects requires more energy, the solidified samples show a higher tensile strength and strain when deformed along the [1 0 0] solidification direction.

The zone of incipient 40Ar* loss-monitoring 40Ar* degassing behavior in a contact metamorphic setting

The ⁴⁰Ar* retentivity behavior was studied in the contact metamorphic aureole of the Torres del Paine intrusion (51°S, Chile) and provides constraints on the closure temperature in contact metamorphic settings. The temperature conditions of the regional anchizonal to epizonal metamorphosed pelitic host rock and the contact metamorphic pelite were recorded by illite crystallinities (Kubler Index) and by Raman spectroscopy on carbonaceous matter. K/Ar age determinations were carried out on illite fine fractions (<0.2 and <2 µm). Differing reaction progresses are observed between organic matter and illite. Organic matter equilibrated with the ambient temperatures, whereas illite is lacking behind the contact metamorphic conditions evident by the absence or limited recrystallization progress. We propose two models to explain the degassing of ⁴⁰Ar* in the absence of recrystallization considering surface loss and volume diffusion as two main pathways. Incipient ⁴⁰Ar* loss appears at temperatures of about 248°C in the <0.2 µm and at 260°C in the <2 µm fraction. The high temperature end of ⁴⁰Ar* retentivity is derived by extrapolation yielding temperatures of 330°C for the <0.2 µm fraction and 345°C for the <2 µm fraction. Thus, the Zone of incipient ⁴⁰Ar* loss, called ZIAL, is constrained to between 248°C and 330°C for the <0.2 µm fraction and to between 260 and 345°C for the <2 µm fraction. The extrapolated values for the upper ZIAL limit are in good agreement with calculated bulk closure temperature values of 348°C (<2 µm) and 286°C (<0.2 µm) assuming ca. 10 kyrs of heating during the emplacement of the Torres del Paine intrusion.

The distillation curve and sooting propensity of a typical jet fuel

Real jet fuels are complex mixtures of many organic components, some of which are aromatic compounds. Towards the high-temperature end of the distillation curve, some of the fuel components are multi-ring compounds. A small amount of these high molecular weight species in the fuel could impact soot nucleation in practical engines especially when the fuel is injected as a spray. This work aims to highlight the variation of the sooting propensity of jet fuels as a function of distillate fractions and to examine the validity of a surrogate fuel in emulating soot production from real fuels. Particle size distribution functions and soot volume fractions are studied in a series of laminar premixed stretch-stabilized ethylene flames doped with Jet A, its various distillate fractions, and the 2nd generation MURI surrogate. Soot formation as a result of doping real jet fuel and its distillate fractions is also investigated in counterflow and coflow diffusion flames. The results show that the higher-boiling distillates mostly influence soot nucleation and produce substantially more soot in nucleation controlled flames than the light molecular fraction and jet fuel as received, while such an effect is seen to be small in flames where soot production is controlled by surface growth. The potential impact of distillate fractions on soot nucleation propensities is discussed.

Study on the setting position of a prime mover in the coaxial-type thermoacoustic cooling system: Comparison with the straight-tube-type thermoacoustic system

The influence of the setting position of a prime mover (PM) on the cooling ability of a coaxial thermacoustic system (coaxial-type) is experimentally investigated. The coaxial-type is a traveling-wave-type similar to the looped-tube thermoacoustic system (looped-tube-type). Then, the relationship between the setting positions of PM and a heat pump (HP) in the coaxial-type is examined and compared with that in the looped-tube-type. As a result, from distant PM and HP positions, the cooling ability decreases as PM and HP approach to their optimum positions in the looped-tube-type. The decrease in the cooling ability is accompanied by a temperature rise at the high-temperature end of PM. This increases the influences of acoustic streaming and the viscous boundary layer, and suppresses the enhancement of the cooling ability. Since the temperature rise of the PM high-temperature end, the coaxial-type shows a rather similar trend to the straight-tube thermoacoustic system.