Particles Of Condensed Phase Research Articles

In-situ two-dimensional temperature measurements using x-ray fluorescence spectroscopy in laminar flames with high silica particle concentrations

X-ray fluorescence spectroscopy (XRF) was used to measure temperatures and study mixing, for the first time in silica particle synthesis flames. Hexamethyldisiloxane (HMDSO) and trimethylsilanol (TMSO) were the particle precursors. A multi-element diffusion burner was used to produce a flat methane flame, and the precursors, dilute in inert gas, were injected via a central jet. Krypton was the fluorescent medium at 3.2 % concentration by volume. Scans with Kr in the central flow and not in the main flow were made to assess the mixing effects between the central and main gas flows. When HMDSO or TMSO were added, a secondary diffusion flame formed between the jet and the main methane flame. The results revealed a dramatic change in the centerline temperature profile of the jet gases when HMDSO or TMSO were added. The main methane flame stoichiometry also affected the temperature profiles. The results show HMDSO and TMSO reactions are initiated in a low-temperature and low-oxygen concentration region of the jet where thermal decomposition is not expected to be significant. Reaction of the particle precursors is therefore attributed to radical transport from the main methane flame. In the current work, particle number densities of up to 270 g/m3 locally are estimated. Thus, the study also demonstrates the capability of the XRF technique for high spatial fidelity measurements in flames with high concentrations of condensed-phase particles, leveraging the attribute that the XRF signal is generally not impacted by condensed-phase interferences. The observations and data obtained in this study inform likely reaction pathways for this important class of siloxane compounds.

Improving Stratocumulus Cloud Amounts in a 200‐m Resolution Multi‐Scale Modeling Framework Through Tuning of Its Interior Physics

AbstractHigh‐Resolution Multi‐scale Modeling Frameworks (HR)—global climate models that embed separate, convection‐resolving models with high enough resolution to resolve boundary layer eddies—have exciting potential for investigating low cloud feedback dynamics due to reduced parameterization and ability for multidecadal throughput on modern computing hardware. However low clouds in past HR have suffered a stubborn problem of over‐entrainment due to an uncontrolled source of mixing across the marine subtropical inversion manifesting as stratocumulus dim biases in present‐day climate, limiting their scientific utility. We report new results showing that this over‐entrainment can be partly offset by using hyperviscosity and cloud droplet sedimentation. Hyperviscosity damps small‐scale momentum fluctuations associated with the formulation of the momentum solver of the embedded large eddy simulation. By considering the sedimentation process adjacent to default one‐moment microphysics in HR, condensed phase particles can be removed from the entrainment zone, which further reduces entrainment efficiency. The result is an HR that can produce more low clouds with a higher liquid water path and a reduced stratocumulus dim bias. Associated improvements in the explicitly simulated sub‐cloud eddy spectrum are observed. We report these sensitivities in multi‐week tests and then explore their operational potential alongside microphysical retuning in decadal simulations at operational 1.5° exterior resolution. The result is a new HR having desired improvements in the baseline present‐day low cloud climatology, and a reduced global mean bias and root mean squared error of absorbed shortwave radiation. We suggest it should be promising for examining low cloud feedbacks with minimal approximation.

Моделирование и расчет параметров процесса взаимодействия электромагнитной волны с единичной металлизированной частицей конденсированной фазы

At present, an important task is to determine the burning rate of energy condensed systems (ECS) with metal additives under non-stationary conditions. At the same time, a promising way to experimentally determine the law of the burning rate is the radio wave microwave method. However, the presence of a significant amount of condensed phase in the combustion products of metallized ECS complicates the tuning of the interference microwave diagnostic method. The article considers the interaction of an incident monochromatic electromagnetic wave with a single particle of the condensed phase in a closed volume without taking into account the influence of the result of the interaction of other particles with the incident wave. A mathematical model has been developed and scattering indicatrices have been obtained for various particle diameters in the range from 10 to 20 micrometers, generated radiation frequencies in the range of 9–15 GHz, and permittivities of condensed-phase particles in the range of 1.6–10. An analysis of the results of a numerical study demonstrates that an increase in the particle size leads to a sharp increase in the intensity of the scattered wave. Changing the frequency of the wave generated by the microwave generator is a priority method for amplifying the intensity of the scattered wave, which makes it possible to detect particles with smaller diameters up to several micrometers.

Effects of the Air Inlet Angle on the Combustion and Ablation Environment of a Hybrid Powder-Solid Ramjet

A hybrid powder-solid ramjet (HPSR) that combined the advantages of a solid rocket ramjet (SRJ) and a powder ramjet engine was investigated in this research. To improve the combustion efficiency and optimize the inner wall thermal protection of the afterburner, the effects of the air inlet angle on the combustion and wall ablation environment were studied. The standard k - ε model, the eddy-dissipation model (EDM), and the boron particle ignition and combustion model were adopted to simulate the two-phase flow in the afterburners with different air inlet angles (45°, 60°, 75°, and 90°). The results showed that the global flow field and the distribution of the vortexes in the afterburner that had a significant influence on the ablation environment of the inner wall and the combustion efficiency were determined by the impact effect and the squeezing effect of the ram air on the primary fuel gas, which was affected by the air inlet angle. As the air inlet angle increased, the total combustion efficiency of the four cases first increased and then decreased, reaching 80.38%, 81.64%, 84.34%, and 83.26% for angles of 45°, 60°, 75°, and 90°, respectively. At the same time, the inner wall ablation became more severe because both the erosion effect of the condensed phase particles and the gas-flow scouring effect were enhanced, and a large temperature gradient was generated on the inner wall. The study results can provide a reference for designing the air inlet angle of an HPSR.

Digital In-Line Holography of Condensed-Phase Particles in Solid Rocket Motor Plume

Condensed phase particles (CCPs) of plume flows in solid rocket motors (SRMs) are one of the major causes of smog and other signal characteristics, which leads to attenuation of weapons guidance system signals. In order to study the dynamic combustion characteristics of the exhaust plume in a high pressure solid rocket motor with highly-aluminized propellanta digital in-line holographic (DIH) measurement system was used for identification and analysis of CCPs of exhaust plume flows in a SRM under 10 MPa pressure. During the SRM firing, the plume particles characteristic in the field of 9–11.5 cm away from the non-expanding nozzle outlet plane was measured and analyzed. Further, in order to improve the efficiency and accuracy of particle identification, a target recognition method suitable for autonomous recognition of plume particles in a complex background from digital holographic images was established. About 12,400 individual particles from two thousand holographic images were recognized, and the 3D spatial information (number and volume probability density function) and mean diameters were obtained and analyzed. The results showed that digital in-line holography measurement technology with target recognition method established in this paper can be applied well to real-time measurement of the 3D dynamic characteristics of the plume particle field anywhere outside of the nozzle outlet of an SRM with highly aluminized propellants. By identifying each reconstructed particle, the 3D spatial distribution, CCPs size distribution and velocity in the measurement area can be obtained.

Observation of laser-assisted electron scattering in superfluid helium

Laser-assisted electron scattering (LAES), a light–matter interaction process that facilitates energy transfer between strong light fields and free electrons, has so far been observed only in gas phase. Here we report on the observation of LAES at condensed phase particle densities, for which we create nano-structured systems consisting of a single atom or molecule surrounded by a superfluid He shell of variable thickness (32–340 Å). We observe that free electrons, generated by femtosecond strong-field ionization of the core particle, can gain several tens of photon energies due to multiple LAES processes within the liquid He shell. Supported by Monte Carlo 3D LAES and elastic scattering simulations, these results provide the first insight into the interplay of LAES energy gain/loss and dissipative electron movement in a liquid. Condensed-phase LAES creates new possibilities for space-time studies of solids and for real-time tracing of free electrons in liquids.

Radiative properties of alumina/aluminum particles and influence on radiative heat transfer in solid rocket motor

The thermal radiation of micron-sized condensed phase particles plays a dominant role during the heat transfer process in aluminized Solid Rocket Motors (SRMs). Open research mainly focuses on the radiative properties of alumina particles while the study considering the presence of aluminum is lacking. In addition, the thermal radiation inside the SRM with consideration of the participating particles is seldom studied. In this work, the multiscale method of predicting the thermal environment inside SRMs is established from the particle radiation at microscale to the two-phase flow and heat transfer at macroscale. The effective gray radiative properties of individual particles (alumina, aluminum, and hybrid alumina/aluminum) and particles cloud are investigated with the Mie theory and approximate method. Then a numerical method for predicting the thermal environment inside SRMs with considering particle radiation is established and applied in a subscale motor. The convective and radiative heat flux distributions along inner wall of motor are obtained, and it is found that the heat transfer in the combustion chamber is dominated by thermal radiation and the radiative heat flux is essentially a constant of 5.6–6.8 MW/m2. The convective heat transfer plays a dominant role in the nozzle and the heat flux reaches the maximum value of 11.2 MW/m2 near the throat. As the combustion efficiency of aluminum drops, the radiative heat flux remains unchanged in most regions and increases slightly along the diverging section wall of the nozzle.

Comparative Studies on the Ablation/Erosion Mechanisms of Silicone Rubber Composites under Erosion of Different Particles by New Testing Method

Abstract The performance of solid rocket ramjets is affected by the ablation resistance of silicone rubber composites in the secondary combustion chamber. To investigate the ablation mechanisms of silicone rubber composites in multiphase flow environments, a new ablation testing methodology, in which particles can be added to the flame, is developed in this investigation. Boron oxide (B2O3) and alumina (Al2O3) particles were used to simulate condensed-phase particles. The experimental results show that because of the high hardness and melting point of Al2O3, the mechanical destruction of the Al2O3 particles was so intense that the surface of silicone rubber composite was completely destroyed, and the matrix was exposed to the surface. The surfaces of the B2O3 particles melted and evaporated in the flame, forming a liquid layer, similar to condensed-phase particles in the secondary combustion chamber of solid ramjet. After the ablation of silicone rubber under the erosion action of B2O3 particles, a char layer and pyrolysis layer were formed, similar to the scenario during the actual ablation of silicone rubber composites. The multiphase flow environment with B2O3 particles can truly reflect the ablative environment experienced by silicone rubber composites.

Effect of Condensed Phase Particles on the Electromagnetic Field Characteristics of Combustion Products in a Flow Path of a Liquid-Propellant Engine. The Results of Experimental Studies

This paper describes the experimental study of amplitude (with a frequency of up to 50 kHz) and integral characteristics of the self-magnetic field of high-temperature combustion products of hydrocarbon fuel, which flow out of the nozzle of a standard liquid-propellant engine (LPE) with simulation of the heat of a combustion chamber with injection of aluminum-magnesium alloy particles (c-phase) into the combustion chamber. It is determined that the amplitude of the magnetic field intensity generated by high-temperature (up to 3500 K) combustion products depends on the LPE operation modes and the presence of k phase particles in the particle flow. The magnetic field amplitude increases by 20% during the LPE burnout ≈0.2 s earlier than the pressure drop in the combustion chamber. The total volumetric electric charge generated by the combustion product flow with the c-phase is estimated.

A new method for studying the ablation/erosion properties of silicone rubber composites based on multi-phase flow

To evaluate the ablation/erosion resistance of the silicone rubber composites, a new method based on multi-phase flow produced by oxygen–kerosene ablation test device was put forward and a new kind of particle was applied in the test. The phase transition characteristics of B2O3 particles and Al2O3 particles in high-temperature flame jet were investigated and compared. On this basis, the ablation tests of silicone rubber composites under the erosion of particles were carried out. The results show that erosion of particles is an important factor in ablation. Compared with Al2O3 particle, B2O3 particle melts, evaporates and forms the liquid coating in the oxygen–kerosene flame jet, which can be used to simulate condensed phase particle in rocket engine. After the multi-phase flow ablation test ablation condition with B2O3 particles, the ablation rates are relatively small and reasonably, and a small ablation pit is formed on the surface of the silicone rubber composites. In the profile of ablated materials, a multi-layer structure with char layer, pyrolysis layer and matrix is formed. In the process of particle impact, the melting layer on the surface of B2O3 alleviates the impact force, thereby reducing the erosion of particles. The feasibility and scientificity of the new method based on multi-phase with B2O3 particles used for ablation resistance of silicone rubber composites investigation is validated.

Mathematical Simulation of the Heat and Mass Exchange in the Process of Convective-Radiant Heating of a Blunt-Nosed Body

A numerical analysis of the nonstationary heat and mass exchange in the heat-resistant composite material (a carbon-filled plastic), forming a cover of the conic part of a blunt-nosed body exposed repeatedly to a pulsed laser radiation, has been performed on the basis of the heat model of destruction of such a material. Different regimes of thermochemical destruction of the carbon-filled plastic due to the action of a moderate-intensity laser radiation on it under the conditions where the porous material of the spherical bluntness of the body is not melted were determined. It was established that the gaseous products of pyrolysis of the carbon material as well as its condensed-phase particles and vapor play a dominant role in the shielding of the surface of the conic part of the body from the laser radiation.

Effect of Condensed Phase Particles on the Characteristics of the Electromagnetic Field of Combustion Products in the Flow Duct of a Liquid-Propellant Engine. The Results of Experimental Studies

Effect of Condensed Phase Particles on the Characteristics of the Electromagnetic Field of Combustion Products in the Flow Duct of a Liquid-Propellant Engine. The Results of Experimental Studies

Исследование интенсивности взаимодействия частиц конденсированной фазы с элементами проточного тракта малоразмерного прямоточного воздушно-реактивного двигателя

Исследование интенсивности взаимодействия частиц конденсированной фазы с элементами проточного тракта малоразмерного прямоточного воздушно-реактивного двигателя

Flow of Combustion Products Containing Condensed-Phase Particles over a Recessed Vectorable Jet Nozzle

The flow of combustion products containing condensed-phase particles over the recessed vectorable nozzle of a solid-propellant rocket motor was investigated with the use of the Reynolds-averaged Navier–Stokes equations, equations of the k–e model of turbulence, and the Lagrange approach. The fields of flows of combustion products and the mechanical trajectories of condensed-phase particles in the charge channel, the prenozzle space, and the nozzle unit of this motor were calculated for different angles of swing of the nozzle. The formation of vortices in the gas flow in the neighborhood of the downstream cover of the nozzle and their influence on the movement of particles different in size were considered.

Параметрическое исследование взаимодействия частиц конденсированной фазы с высокоэнтальпийным потоком воздуха в прямоточной камере сгорания

Параметрическое исследование взаимодействия частиц конденсированной фазы с высокоэнтальпийным потоком воздуха в прямоточной камере сгорания

Morphological Variations of Explosive Residue Particles and Implications for Understanding Detonation Mechanisms.

The possibility of recovering undetonated explosive residues following detonation events is well-known; however, the morphology and chemical identity of these condensed phase postblast particles remains undetermined. An understanding of the postblast explosive particle morphology would provide vital information during forensic examinations, allowing rapid initial indication of the explosive material to be microscopically determined prior to any chemical analyses and thereby saving time and resources at the crucial stage of an investigation. In this study, condensed phase particles collected from around the detonations of aluminized ammonium nitrate and RDX-based explosive charges were collected in a novel manner utilizing SEM stubs. By incorporating the use of a focused ion beam during analysis, for the first time it is possible to determine that such particles have characteristic shapes, sizes, and internal structures depending on the explosive and the distance from the detonation at which the particles are recovered. Spheroidal particles (10-210 μm) with microsurface features recovered following inorganic charge detonations were dissimilar to the irregularly shaped particles (5-100 μm) recovered following organic charge firings. Confirmatory analysis to conclude that the particles were indeed explosive included HPLC-MS, Raman spectroscopy, and mega-electron volt-secondary ionization mass spectrometry. These results may impact not only forensic investigations but also the theoretical constructs that govern detonation theory by indicating the potential mechanisms by which these particles survive and how they vary between the different explosive types.

The distribution of excess charges in the diffusion flame of hydrocarbons

The paper discusses the experimental investigation results of the potentials distribution (probing) and the excess charges in diffusion flames of propane and polymers - PMMA (polymethyl methacrylate) and divinyl rubber. The study of the excess charges distribution was made by analysis of flame deformation in the presence of an external lateral electrostatic field. The existence and the accumulation of excess charges in the flame are generally explained on the basis of consideration of the interaction processes of condensed phase particles and charges (electrons) generated during combustion in the presence of a dusty plasma. However, this mechanism does not give the opportunity to consider the sign and magnitude of the excess charges distribution in the flame, depending on the products composition and the value of the oxidant excess. It is unclear how oppositely charged immiscible streams of flame are formed and coexist.

Control of dispersed-phase temperature in plasma flows by the spectral-brightness pyrometry method

In the present work, we propose a new method for measuring the distribution of temperature in the ensembles of condensed-phase particles in plasma spray flows. Interrelation between the spectral temperature of the particles and the distribution of camera brightness signal is revealed. The established inter-relation enables an in-situ calibration of measuring instruments using the objects under study. The spectral-brightness pyrometry method was approbated on a Plazer plasma-arc wire spraying facility at the Paton Institute of Electrical Welding (Ukrainian Academy of Sciences, Kiev) and on the Thermoplasma 50-1 powder spraying facility at the Institute of Theoretical and Applied Mechanics (Russian Academy of Sciences, Siberian Branch, Novosibirsk). The work was supported by the Russian Foundation for Basic Research (Grants Nos. 14-08-90428 and 15-48-00100).

Firmation of condensed combustion products in dust flames of metals: Coagulation stage

The coagulation dynamics of condensed products of vapor-phase or gas-phase combustion of gas mixtures of microdispersed metal particles in dust laminar flame considered taking into account the ionization of the combustion zone due to additives of electronegative and electropositive atoms and due to thermionic emission. The influence of the degree of ionization of a monodisperse coagulating aerosol and the charge of the particles on the coagulation rate constant is studied. It is shown that the rate of coagulation of the aerosol is most significantly affected by the Coulomb interaction of like-charged condensed-phase particles, which, under certain conditions, leads to an early stop of this stage in the condensation of combustion products. Ionization of the coagulating particles gives rise to a dependence of the size of primary particles of combustion products on the environmental parameters affecting their electric charge, and can be used for targeted control of the degree of dispersion of the combustion products.

Flow and motion of condensed-phase particles in the prenozzle space of solid-propellant rocket motors

Flow and motion of condensed-phase particles in the prenozzle space of solid-propellant rocket motors