Home – Home – Jornals – Thermophysics and Aeromechanics 2006 number 1

The structure and principle of operation of a new wind tunnel AT-303 with adiabatic compression are described. Results of systematic investigations are presented in terms of velocity distributions both at the nozzle exit and in the region where the models are located. The velocity fields are obtained with the use of total pressure probes in the ranges of Mach numbers from 7.6 to 19.7 and Reynolds numbers per meter Re₁ = (0.25–3.64)^.10⁷.

The experimental approach is outlined for study of heat fluxes on the surface of a blunt body of revolution (with kinked generatrix) in a hypersonic gas flow. The main attention is paid to the effect of coolant injection flow rate on resulting heat flux at different Reynolds numbers and attack angles. The significant role of distributed gas blowing on a body surface for the heat flux distribution has been demonstrated.

We present the results of designing the contours of supersonic parts of the solid-propellant rocket motor (solid motor) nozzles with high expansion ratios with the aid of direct variational methods. A continual model is used for the motion of a two-phase polydispersed continuum with regard for processes of interaction both between the carrying gas and the particles suspended in it and between the particles of various fractions. The method of local variations is employed as a numerical method of searching for the extremum of a multivariate function. The computational results evidence a fair efficiency of the proposed approach for the optimization of such nozzles.

The development of a non-self-similar liquid-liquid jet of a non-Newtonian reactive liquid is considered within the framework of the boundary layer theory. The analytic expressions are obtained on the basis of the local similarity method for variation of integral parameters of jet flow along its axis, which agree fairly well with the numerical solution of a non-self-similar problem.

Large Eddy Simulation (LES) of turbulent free round jet submerged in water has been performed at Reynolds number Re = 25 000. LES results are compared against the PIV measurements data for the same flow configuration. The processes of the mixing layer formation in the jet initial region and its evolution downstream have been studied with the analysis of turbulent power spectra. The effect of the subgrid Smagorinsky model coefficient CS on the jet hydrodynamics has been studied.

A joint testing of the specialized (VP2/3) and universal (FLUENT) packages of applied programs of the hydrodynamic and thermophysical profile is carried out on the basis of the solution of a well-known problem of recirculation flow of a viscous incompressible fluid in a lid-driven square cavity. The Reynolds-averaged Navier ? Stokes equations are solved with the aid of implicit factored computational procedures. The adequacy of chosen one-, two- four-parametric semiempirical differential models of turbulence is analysed in detail.

Results of experimental investigations of the nonlinear stage of sinusoidal and varicose instability of a streaky structure, which leads to multiplication of streaky structures and origination of coherent structures (such as Λ-structures), are presented. Riblets suppress the intensity of streaky structures, stabilize the flow against the development of the secondary high-frequency instability of streaky structures, and, for this reason, delay spatial turbulization of the flow. The results of these investigations can be useful for understanding the flow structure in such situations and for possible controlling of the coherent structures aimed at flow stabilization.

The system of Dressler hydraulic equations is presented for description of 3D perturbations. Dressler’s idea about an absence of solution singularity was considered for investigation of tolerance of the 2D roll-waves for 2D and 3D perturbations; the spectra were plotted. The result on stability of stationary roll-waves of the soliton type was obtained.

Experimental data on heat transfer with intense evaporation in the falling films of liquid nitrogen were analysed. According to data generalization, heat transfer at evaporation becomes more intense under the pre-crisis modes at high heat fluxes for two studied boundary conditions on the heat-releasing surface: T_w ≈ const and q_w ≈ const. The relative contributions of conductive and convective components of heat transfer for different heat fluxes were estimated due to statistical treatment of the wave characteristics carried out by the capacitance probes for measurement of the local liquid film thickness. It was found out that heat transfer intensification is mainly caused by a drastic decrease in thermal resistance of the local zones with intensely evaporating residual layer between large waves. At that, the convective component of heat transfer related to wave perturbations on a free surface of a liquid film decreases significantly with a rise of heat fluxes. New data on pulsa-tions of the local temperature of the heat-releasing surface were obtained at different points along the flow with the modes of “dry spot” formation.

The models of heat and mass transfer in foam scrubbers and centrifugal-bubbling apparatuses developed previously by the authors are refined. This upgrade takes into account the Stefan flow at high humidity of the treated air.

The paper deals with a problem of using modern very large-scale integration circuits developed for space applications and penalized with a high heat power. The method was developed for integration of cooling elements into printed fiberglass boards for proper thermal operation mode. The approach efficiency was demonstrated with the example of a processor module created for the space project “Spectrum-X”.

Thermal conductivity of ozone-safe refrigerant C10M1 in liquid (303.9–342.4 K, 1.23–4.257 MPa) and gaseous (324–398.15 K; 0.672–2.107 MPa) states was studied by the methods of high-frequency thermal waves and coaxial cylinders. The estimated measurement errors for the temperature, pressure, and thermal conductivity are ±0.02 K, ±1.5 kPa, and ±1.5–2.5 %, correspondingly. Approximation dependencies for thermal conductivity were obtained over the studied range of temperatures and pressures as well as on the dew and bubble lines. It is shown that thermal conductivity in the liquid state is additive relative to mass concentrations of components.

The method of determining the true temperature of an opaque body via a heated thermal radiation spectrum recorded in spectral bands of particular width is considered. The accuracy of true temperature estimation versus a number of unknown parameters of a body emissivity model and quantity and the width of spectral bands as well are investigated by means of the "quasi-real" experiments. The solution for the polynomial emissivity model (example for platinum) is unstable even in the case of input data given with computer accuracy if the number of unknown parameters exceeds ten. It is shown that an essential increase in the accuracy of the body true temperature recovery can be achieved by processing the repeated experiments.

Structure and properties of aluminum coatings deposited onto steel substrates by the cold gas-dynamic spraying (CGS) method were examined. Aluminum CGS coatings fundamentally differ from their thermal counterparts as they enable the formation of heavy-duty layers of metal particles on substrates at temperatures below 500 K. A dense, low-porosity coating is found to form, tightly bound to the base metal. The adhesion strength is shown to weakly depend on the thickness of the sprayed coating due to the compressive stress present in the surface layer. A qualitative model for the coating formation process is proposed.

The measurements of the amplitude-phase characteristics of the electromagnetic field in a high-frequency jet discharge burning in air and argon have been performed. Experimentally obtained radial distributions of the radial component of the electric field gave the base to determine the value of the wave number of an electromagnetic wave which propagates in the HF jet discharge plasma. The axial distribution of the radial component of the electric field has been calculated from the model of a jet discharge channel formed as a finite-length electric line.

Basing on computational results a possibility is proposed for realizing an arc discharge at coaxial cathodes. Such a discharge can be used at a relatively high current, which will enable an increase in its thermal effect on the article to be processed.

The approach was developed for creation of high-speed mathematical models of cogeneration turbines; these models are the tools for fast optimization of operation modes of large-scale cogeneration heating plants. The approach was developed for identification of mathematical models of steam turbines via measuring its parameters. The example of parameters identification is presented for steam turbine T-100/120-130. The optimization computations of operation modes for a cogeneration heating plant were the basic ones for plotting equivalent energy characteristics at a given consumer heat load.