Thermophysics and Aeromechanics最新文献

The paper describes an experimental study of the influence of multiple cyclic pressure loading on the service life and sorption performance of a composite sorbent whose granules consist of selectively permeable (to helium) microspheres as a filler and pseudoboehmite as a porous binder. A test bench is specially designed and fabricated for the study, which makes it possible to model various operation regimes of gas-separation plants in the pressure range up to 10 MPa. Cyclic tests of pressure loading of the granulated composite sorbent are performed, and the sorption capacity of the sorbent with respect to helium is measured. It is found that the composite sorbent retains its integrity and sorption performance under cyclic loading of 1000 cycles and more at pressures up to 10 MPa.

Using an isothermal drop calorimeter, the enthalpy increment of the Na₁₅Pb₄ and Na₅₀Pb₅₀ alloys was measured and the heat capacity was determined in the temperature range of 420–1075 K, including the solid and liquid states. It has been established that the values of the heat capacity of melts significantly exceed the calculations of this value according to the laws for an ideal solution, and this difference decreases with increasing temperature. The obtained results confirm the currently existing ideas that various complexes with a partially ionic character of the interatomic interaction are formed in the melts of alkali metals with lead systems.

This work examines the transition from kinetic to diffusion combustion using optical diagnostic methods. Experimental data were obtained on the temperature fields, composition and velocity of gas near the leading edge of a hydrogen flame flowing from a 2×20 mm slit into the air. The distribution of the rate of combustion product formation, the intensity of heat release and pressure was obtained using the method of balances in equations of energy, momentum, and mass transfer. It is shown that during the transition to diffusion combustion, heat release along the flame length decreases more slowly than the rate of water formation.

Rarefied gas flow into a vacuum through short linearly diverging and converging channels has been examined with the direct simulation Monte Carlo method. Solution to the problem has been suggested using complete geometric setup with quite large areas on inlet and outlet of a model channel in examined geometry. A mass flow rate through the channel and flow field both inside the channel and upstream and downstream have been calculated in a wide range of gas rarefaction. These calculation results are comparable to corresponding data for the channel with constant cross section. A strong impact of channel geometry and gas rarefaction has been proved.

Using an ultrasonic interferometer in the temperature range from 293 to 393 K at pressures from 0.13 to 1.5–2.8 MPa, the speed of sound (U) was measured in helium-xenon gas mixtures with a helium content of 60.34; 71.72 and 85.32 at. %. The measurement errors of temperature, pressure, and speed of sound were ±20 mK, ±4 kPa, and ± (0.15–0.30) %, respectively. By approximating the experimental data for each composition, equations were obtained to describe changes of the speed of sound as a function of pressure and temperature over the entire measurement range. The existing reference and experimental data on the speed of sound in inert gases and He-Xe mixtures were analyzed. A method for calculating U of mixtures with a helium content above 71.7 at. % He to a temperature of 1500 K and a pressure of up to 7 MPa was developed.

Reflections of hydraulic jumps on shallow water are studied. Theoretical criteria of the transition between the regular and Mach reflections are derived, and it is shown that there is a domain of angles of incidence where both types of reflection are possible. Numerical simulations reveal a hysteresis of this transition, which is consistent with theoretical predictions. It is shown that the hysteresis can be obtained by smoothly varying either the angle of the wedge generating the hydraulic jump or the freestream Froude number.

The paper presents the results of experimental study for rising a cluster of monodispersed gas bubbles in viscous liquid with/without surfactant for the Reynolds number in the range Re = 0.01–1. The influence of the surfactant type on the dynamics of bubble cluster rising has been analyzed. The qualitative pattern of monodispersed bubble cluster rising was defined as a function of initial void fraction in the range C_V = 0.001–0.04. New experimental data were obtained on velocity and drag coefficient for a compact cluster made of monodispersed bubbles rising in a liquid with/without surfactant (both for contact and contactless type of bubble rising).

The paper considers the aerodynamics of flow around a cubic model building. Experimental and simulation data were compared for the flow problems with different scales. Geometry parameters for the models can be varied from 0.025 to 6 m, while the range of Reynolds number for considered data is from 10⁴ to 10⁶. The scalability of the modeling is confirmed, which is beneficial for validity of laboratory aerodynamic experiments.

Experimental study was performed for the dynamics of vapor bubble rising in the annular channel at subatmospheric pressure. The gas bubble is formed during boiling of superheated degassed liquid in an annular channel restricted by two glass tubes with the diameters of 25 and 16 mm. It was demonstrated that the dynamics of vapor cavity while rising the vapor bubble in the annular channel demonstrates a qualitative difference from the dynamics for an ascending gas bubble. The behavior is similar to a Taylor vapor bubble behavior in a round tube with a small diameter. One of typical features of vapor cavity behavior in an annular channel is the possibility of vapor cavity decay after the bubble collapse during the pulsation flow mode.

The paper presents the results of a numerical study of gas dynamics and integral parameters of the flow at the channel entrance located behind a conical or plane shock wave. The freestream Mach number range is M = 2–4 and the range of the angles of the compression surfaces of the wedge and cone is δ= 10–90°. Data on the flow structure at the channel entrance, mass-averaged Mach numbers, total pressure loss coefficient, and flow rate coefficients are obtained. A comparative analysis of these parameters is performed, and the advantages and drawbacks of the channel entrance positions in various types of the flow are noted.