Vol 55, No 2 (2017)

We observed the rotational spectral lines of the He*₂ excimer within the range of 910–930 nm in the corona discharge in normal liquid He at the temperature of 4.2 K and the pressure of 1 atm. The spectral range is filled with the rotational lines of the C¹Σ_g⁺ ⇒ A¹Σ_u⁺ singlet and the c³Σ_g⁺ ⇒ a³Σ_u⁺ triplet transitions. These transitions end at the rotational levels of the lowest metastable terms, A¹Σ_u⁺ and a³Σ_u⁺ of the He*₂ excimer. Then, the population of the rotational levels with the K' number of the upper C¹Σ_g⁺ and c³Σ_g⁺ terms (the quantity of the molecules with the rotational moment of K' in the excited molecule ensemble in the discharge) is proportional to the intensity of the rotational lines marked K' of the C¹Σ_g⁺ ⇒ A¹Σ_u⁺ singlet and the c³Σ_g⁺ ⇒ a³Σ_u⁺ triplet. The populations might be calculated according to the experimental intensities of the rotational spectral lines. The emitting corona plasma in the liquid He is nonequilibrium and the rotational level populations do not correspond to the Boltzmann distribution. The efficient rotational temperature exceeds the liquid He temperature, 4.2 K.

We investigate the mechanisms of formation and death of negative ions in aluminum-water plasma, their role in kinetics of its ionization and recombination, and influence on plasma parameters. Negative ions, in contrast to the positive, do not in fact participate in the heterogeneous processes and require, to enhance their influence on the plasma parameters, first, high electron temperatures (~1.5 eV and higher) and, second, low n_e and [Al] concentrations: in this way, they make a great contribution to the H₂O dissociation at the expense of the electron energy (2–8 electrons per a molecule). We show that, even in the most favorable conditions at low H and O concentrations within the experimental temperature range, T_e = 0.6–1 eV, the negative ions do not, in fact, influence the Al concentration and, in the operation reactor zone, the other parameters, except for the microparticle concentration. We reveal the source, important for the spectral diagnostics of the atomic emission, of recombination populating of the excited Al levels. The main negative ion (OH^–) is established. We have concluded the impossibility of its use in order to optimize the operation of the aluminum-water plasma-chemical reactor.

The equations of state for benzene, tetradecane, and their deuterated counterparts are derived on the basis of the original method of constructing the wide-range equations of state for hydrocarbon liquids in an analytical form. The equations describe gas and liquid phases at intensive gas-dynamic processes with consideration of evaporation and condensation and include dissociation and ionization processes associated with super-high pressures and temperatures.

Critical analysis of experimental and theoretical data on the structure and vibrational frequencies of GeO₂, Ge₂O₂, and Ge₃O₃ molecules is performed. The values of molecular constants are chosen, and thermodynamic functions in the rigid rotator–harmonic oscillator approximation are calculated in temperature interval Т = 298.15–3000 K. The values obtained are introduced into the data base of the IVTANTERMO program complex.

The thermal transformation of the pyrolysis–condensation–rankinite synthesis process at a normal pressure is considered in detail. Rankinite pyrolysis is performed with a step-by-step increase in enthalpy (TERRA software system). Rankinite pyrolysis components condense on a surface with temperature Т = 298.15 K. Condensate components are equivalent to pyrolysis components. Wollastonite and limestone can precipitate upon condensation to form a mineral deposit. Synthesis is performed by mixing the condensate components. The components and heat of chemical reactions, the enthalpy, the temperature, and the heat content are determined. It is shown that the decomposition of rankinite (Т_dec = 2598.36 K), wollastonite (Т_dec = 3662.7 K), and limestone (Т_dec = 3680–3810 K) occurs in the process of synthesis and pyrolysis at a constant temperature. The complete pyrolysis–condensation–synthesis process picture typical for various compounds is given.

The influence of the melt thermal conductivity Λ_m on the formation of temperature fields upon heating and melting of a plane aluminum oxide layer by CO₂ laser radiation with a flux density q from 200 to 3000 W/cm² is investigated using a rigorous model of transient combined radiative and conductive energy transfer. The maximum heating time is 100 s. Parameter Λ_m varies from 1.5 to 3 W/(m K). Absorption coefficient k_l for the laser radiation is assumed to be 1000 cm^–1. The formation of a two-phase region,which exists for a short time, has been observed in the initial melting stage at a depth less than the penetration depth of the heating laser radiation. Maxima of the heated-surface temperature and melt thickness (not coinciding in time) are found at q < 600 W/cm². The melt thickness and its value at the maximum depend only slightly on q, while parameter Λ_m significantly affects the melt thickness at the maximum and during the entire heating process. It is shown that similar temperature profiles are established in the solid phase at different Λ_m values while approaching the quasi-steady state due to large values of the melt absorption coefficient in the wavelength range that is most energetically important for radiative transfer. The melt thermal conductivity affects only slightly the temperature of the “cold” surface that is opposite the melt.

A numerical investigation of the boundary layer on a permeable wall in a supersonic gas flow is performed using a differential turbulence model. Temperature recovery factors are obtained for a series of Prandtl numbers and gas suction or injection in a wide range of the permeability factor from critical injection to asymptotic suction. With the example of air injection into a supersonic air flow, two methods for determining the temperature of a heat-insulated permeable wall are considered. The first is to solve the problem with a boundary condition of zero heat flux to the wall. The second is similar to an experimental method when the temperature of the gas injected at a section along the plate length becomes equal to the wall temperature. The heat-insulated wall temperatures and temperature recovery factors obtained by these two methods for injection below the critical one are close to each other. In case of critical injection, these two methods yield different results.

The results of measurements of the temperature field in a hydrogen-oxygen flame by means of broadband coherent anti-Stokes Raman spectroscopy are presented. The measurements were performed at pressures up to 1.7 MPa and temperatures ~3000 K with the spatial resolution of ~0.04 × 0.04 × 2.5 mm³. The duration of a single measurement was 10 ns and the sampling rate was 10 Hz. The error of the temperature determination was ~4% for the single-shot measurements and ∼0.15% for the measurements of the average values during 100 s under quasi-stationary burning conditions.

Flow of gas mixture around and inside a scale model of hypersonic vehicle is simulated with use of the FlowVision software. The model is placed in a wind tunnel. All the solid surfaces present in the experiments are taken into account in the calculations. Calculation results are compared with experimental data obtained in two runs: without burning hydrogen in the combustion chamber (cold run) and with burning hydrogen (hot run). The computational grids are built automatically with use of different adaptation options available in FlowVision. The agreement of numerical results with experimental data is good.

Computational and theoretical works devoted to studying the generation and dynamics of air tornado-like vortices are reviewed. Currently developed approaches to mathematical modeling of the main characteristics of vertical atmospheric vortices are presented.

Experimental results are presented on transition of a streamer shape multichannel discharge into a multichannel spark discharge. We present current–voltage characteristics of a multichannel streamer discharge at atmospheric and reduced pressures as well as temperature distribution between a plate-like copper electrode and technical water.

The impact of a shield made of granulated material on attenuation of a shock wave multiply reflected from walls is investigated during an explosion inside a closed volume. We performed experiments in a shock tube with a short high-pressure chamber. A low-pressure chamber was filled with air at atmospheric pressure. The flat blast wave with the reducing pressure profile was created. We discovered the dependence of the pressure reduction at a reflected wave front on a distance between the protecting shield and a closed end of the shock tube.