Thermophysics and Aeromechanics最新文献

The spatial evolution of the flow structure formed by the movement of a submillimeter pulsed arc discharge in a magnetic field near a flat dielectric surface was studied in detail using optical methods (Schlieren method and PIV tomography). Due to good controllability of the dynamic and electrical characteristics of the discharge with high precision synchronization of the equipment, a high degree of detail of the flow pattern on small scales was achieved. The formation of a transversely located toroidal vortex propagating in the direction of the generated electromagnetic force is shown. The formation of a secondary flow in the tail of the jet was detected, which can be explained by the ejection of the surrounding gas into the region of reduced density.

The experimental results on thermal destruction processes during pyrolysis and the degree of fragmentation caused by pulsed aerodynamic impact on a demonstration sample (DS) simulating a separable structural element of the Soyuz-2 launch vehicle at the launch site have been obtained. A polymer based on aramid fibers and epoxy binder is used as the structural material of the DS. The process of pyrolysis and subsequent thermal destruction occur due to heating the DS with an electric heater. A pulsed aerodynamic impact takes place in a vacuum chamber due to a gas-dynamic blow of compressed air with an assessment of the fragmentation degree. An experimental program and a corresponding test rig with the metrological support have been developed. Based on the obtained results, a further direction of research on thermal destruction and aerodynamic fragmentation of DS has been mapped out.

A system of multipoint diagnostics for pressure pulsations was used in experiments. The data is compared with the results of high-speed flow visualization for the case of a cloud cavitation flow past a smooth hydrofoil in a slit channel. It was shown that the shock mechanism is significant for development of the attached cavity. The main mechanism for detachment and shedding of a cavity is a re-entrant flow.

Method of differential scanning calorimetry was applied for measuring the specific isobaric heat capacity of yttria fully stabilized zirconia (15 wt. %), which is widely used in production of high-temperature structural ceramics. New reliable experimental results were obtained on the specific heat capacity in the temperature range of 300–1270 K of a solid state with the uncertainty of 2–4 %. A table of reference data for specific heat capacity of the ceramics is presented. The experimental data are compared with available reference data. The study found that for a wide range of temperature and Y₂O₃ concentration, the heat capacity of YSZ solid ceramics can be accurately evaluated using the Neumann–Kopp rule and also by the average atomic weight of the compound.

The analysis of the efficiency of turbulent boundary-layer control on low-speed airfoils using mass transfer through a permeable wall is presented. Particular attention is paid to the consideration of the physical properties of the wall flow in the presence of positive (from the wall) and negative (to the wall) mass transfer and the aerodynemic characteristics of airfoils under conditions of distributed or localized action of mass transfer of varying intensity on the boundary layer.

The flow pattern and integral flow parameters in confusors implementing different methods of a supersonic flow compression are numerically investigated. Model configurations are considered, consisting of a tapering inlet section and a constant cross section, in which different types of flows take place: two-dimensional, axisymmetric, or three-dimensional flow. The flow is completely turbulent and computations are based on Navier–Stokes equations and the k-ω SST turbulence model. The flow in the confusor is assumed to be supersonic everywhere, the range of freestream Mach numbers is M_in = 2–4.5.

The paper presents characteristics of coherent structures that develop in the shock wave / boundary layer interaction zone. Experiments were performed on a flat plate for two states of the oncoming boundary layer: laminar and turbulent. The shock wave was generated by a wedge-type body placed ahead the plate. The data are obtained from hot-wire anemometry technique. Flow structures in a boundary layer were studied using the analysis of coherence spectra. It was demonstrated that the transversal size of coherent patterns varies insignificantly in the interaction zone between shock waves and boundary layer.

The paper presents the experimental results on the distribution of the outer wall and coolant temperatures in a simplified model of the peripheral region of a fuel assembly (FA) consisting of two parallel cells. The experimental setup was equipped with three fuel element simulators with a diameter of 10 mm and a length of 500 mm. The power of each fuel element simulator was up to 2000 W (4 kW/m). During operation, the fuel elements were connected to the power source in turn, which allowed determination of the features of temperature distribution in the model with non-uniform energy release. A movable thermocouple and an IR camera were used for measurements. The data obtained for a water coolant and a lead-bismuth alloy are compared. It is shown that the main patterns of temperature distribution are generally similar for different coolants.

A device that allows obtaining a highly rarefied flow of microdroplets for their subsequent use in various fields of technology or scientific research is considered. The created setup allows microdroplet obtaining in a periodic mode. The oscillation period is about 30 seconds. With the help of gas flow pulsations, relatively small drops are filtered, which gives a more uniform droplet size distribution.

A mathematic model developed for describing the methane pyrolisis processes in a low-size plasmatron setup. Calculations are compared with experimental results on pyrolisis products composition. The factors promoting the yield of useful products are estimated. If the exit reactor temperature is increased to 1500–2000 K, this reduces the ethylene yield and increases the soot content with a minor increase in the hydrogen yield.