ITAM SB RAS Research Articles

INVESTIGATION OF THE CYLINDRICAL RESONATING CAVITY EFFECT ON A JET’S NEAR ACOUSTIC FIELD IN THE TWO-CHANNEL SYSTEM

Numerical gas flow modeling in the two-channel resonance system path of ITAM SB RAS is carried out. Numerical simulation of a nonstationary acoustic-convective flow was carried out using the Ansys Fluent software package in a three-dimensional formulation. As a result of the simulation, the gas-dynamic characteristics of the flow in the system central part, where a supersonic under-expanded jet is formed, are obtained. The analysis of pressure distributions in the first barrel of the jet near field, as well as inside its structure under the conditions of a two-channel system, is carried out. Six points in the near field of the jet were selected for the study. Taking into account the unsteadiness of the flow in the resonant system path, the studied points record the fluctuations of the formed flow and the change in the jet structure. The spectral composition is estimated near and inside the jet undisturbed by the resonator and a comparison with the spectrum of the resonant system is presented. The possibility of influencing the jet structure and acoustic characteristics near the jet using a resonator is shown.

COMPARISON OF PHYSICAL CHARACTERISTICS OF HIGHLY POROUS MATERIALS DURING THEIR ACOUSTIC AND TRADITIONAL DRYING

A comparison was made of drying fine-porous silica gel grains in an acoustic-convective dryer of the ITAM SB RAS with convective drying in an air atmosphere at normal pressure and with a residual pressure of the furnace working chamber p = 10 -3 MPa. Changes in the morphology, structure, specific surface area, total pore volume and mechanical properties of the original, moistened and dried silica gel grains were recorded. It is shown that when the acoustic-convective drying mode used in the work occurs, intensive extraction of moisture from the sample occurs, which is accompanied by dehydration of the grain fragments of grains are observed, macrodefects in the form of chips are found on the surface of the grains, main cracks are present in the structure of the material, the specific surface area decreases to 200 m2/g, a decrease in the total pore volume to 0:26 m3/g, or the absence of pores smaller than 100 nm, the mechanical strength of silica gel decreases to 96.25%.

EXPERIMENTAL STUDY OF GAS DYNAMIC FLOW PARAMETERS IN THE ACDI CHANNEL WITH A DEEP CYLINDRICAL RESONATOR IN THE PRESENCE AND WITHOUT THE STUDIED SAMPLE

This study is aimed at the experimental research of gas dynamic flow parameters in the acoustic-convective drying system (ACDS) duct of the ITAM SB RAS. During the experiment, the flow temperature is recorded in the resonating cavity end vicinity and at the cylindrical resonator surface. Two variants of gas-dynamic flow in the waveguide are considered when the sample is installed in the ACDS working part path and when it is not present. As a result of experimental studies, it was revealed that when the test sample is placed in the ACDS path, the signal recorded without the sample changes at the input to the working part; the signal turns 180 degrees relative to the origin point, while the frequency response and temperature of the working flow do not change. The dynamics of changes in gas temperature near the end of the resonating cavity when placing the sample in the ACDS working part was obtained. The maximum gas temperature in the resonating cavity, which is achieved in the presence of an obstacle in the ACDS path, has been determined. Registration of temperature with surface thermocouples showed that the resonator can be conditionally divided into two areas: 1) near the blind resonator end, where the effect of placing the sample in the ACDS is observed; 2) near the open resonator edge, where there is no influence.

Study of the structure of turbulent underexpanded supersonic jets by laser transillumination

The paper analyzes the spatial distribution of the average air density in a supersonic jet based on the results of laser transillumination. The algorithm to retrieve the average air density from transverse (to the jet axis) deviations of the transilluminating wavefront was tested in experiments on the Vertical jet setup of ITAM SB RAS. The results of retrieval are compared with the known literature data of contact measurements and with results of numerical simulation. The good sensitivity of local wavefront tilts to oscillations in the air density at frequencies of discrete acoustic tones has been demonstrated. This opens up the possibility of experimental study of the spatial structure of air density inhomogeneities in the jet channel.

Experimental Investigation of the Structure of Disturbances from Two Pulsed Sources in the Flat-Plate Supersonic Boundary Layer

The work is devoted to the development of a new experimental method for entering controlled disturbances with a given frequency-wave structure into a supersonic boundary layer. Experimental data on the formation of disturbances from two pulsed sources (pulsed glow discharge) in the laminar flat-plate boundary layer at the Mach number equal to 2 are given. The experiments were carried out in the T-325 wind tunnel of ITAM SB RAS. The localized sources were spaced out at the same distance from the leading edge of the plate at 6 mm from each other spanwise. Flow pulsations were measured using a hot-wire probe of constant temperature anemometer, the signal was recorded synchronously with ignition of the discharges. This made it possible to distinguish the pulsations from the discharges against the background of random uncontrolled “natural” pulsations of the boundary layer. The spatial-temporal and frequency-wave structure of the generated disturbances from a single or two discharges, operating synchronously or with a time delay, are analyzed. It is found that the maximum difference in the structure of disturbances from one and two sources is observed in the central region, while at the side boundaries of the disturbances, the pulsations are close in all considered cases. In the wave spectra of disturbances from two discharges, nodes and antinodes are formed. Their position is determined by the distance between the sources and the time delay in their operation.

Experimental Investigation of the Structure of Disturbances from Two Pulsed Sources in the Flat-Plate Supersonic Boundary Layer

The work is devoted to the development of a new experimental method for entering controlled disturbances with a given frequency-wave structure into a supersonic boundary layer. Experimental data on the formation of disturbances from two pulsed sources (pulsed glow discharge) in the laminar flat-plate boundary layer at the Mach number equal to 2 are given. The experiments were carried out in the T-325 wind tunnel of ITAM SB RAS. The localized sources were spaced out at the same distance from the leading edge of the plate at 6 mm from each other spanwise. Flow pulsations were measured using a hot-wire probe of constant temperature anemometer, the signal was recorded synchronously with ignition of the discharges. This made it possible to distinguish the pulsations from the discharges against the background of random uncontrolled “natural” pulsations of the boundary layer. The spatial-temporal and frequency-wave structure of the generated disturbances from a single or two discharges, operating synchronously or with a time delay, are analyzed. It is found that the maximum difference in the structure of disturbances from one and two sources is observed in the central region, while at the side boundaries of the disturbances, the pulsations are close in all considered cases. In the wave spectra of disturbances from two discharges, nodes and antinodes are formed. Their position is determined by the distance between the sources and the time delay in their operation.

Experimental study of effect of a pair of weak shock waves on laminar-turbulent transition in the boundary layer of flat plate at Mach number 2

An experimental study of the effect of longitudinal vortices generated by weak shock waves on the laminar-turbulent transition in the boundary layer of a flat plate at a Mach number 2 is conducted. To amplify the effect of the longitudinal vortices generation, a model with leading edge blunting radius of 0,5 mm was used. The disturbance intensity was measured with a constant temperature hotwire anemometer and a single-wire sensor. To change the Reynolds numbers in the flow, the method of varying the pressure in the pretest section of a supersonic wind tunnel was used. According to the experimental conditions, the level of mass flow perturbations in the test section T325 of ITAM SB RAS did not exceed 0,1 % of the mean flow in the frequency range from 0,2 to 50 kHz. In this work, it is obtained for the first time that stationary streamwise vortices that arise in the boundary layer of a flat plate because of the action of a pair of weak shock waves on its leading edge lead to an early laminar-turbulent transition at different Reynolds numbers. In the case of a homogeneous boundary layer, the transition is achieved at Rex≈ 3,1 × 106, and in measurements in the region of vortices from shock waves at Rex≈ 1,5 × 106and Rex≈ 2 × 106.

Formation of highly concentrated heterogeneous flows during plasma deposition of powder materials

Most industrial installations for plasma spraying of powder materials are equipped by nozzles with local (radial) powder input into the thermal plasma jet generated by the plasma torch. Such a local input of the sprayed material significantly perturbs the flow of the plasma jet, and causes dispersion of temperature and velocity of the particles of the sprayed powder materials. This work presents study of high-temperature heterogeneous flows generated by the electric arc plasma torch PNK - 50 with an annular (circular) input unit of powder materials with their gas-dynamic focusing developed at ITAM SB RAS. The performed experiments proved that the annular injection of a powder material guarantees the stable formation of a highly concentrated flow of thermal plasma with particles of sprayed powder materials. The comparative analysis clearly showed the advantages of annular powder input unit with its gas-dynamic focusing. In contrast to local point injection, axisymmetric annular injection practically does not disturb the jet of thermal plasma and, thus, significantly increases the efficiency of interphase exchange.

Laser breakdown model in the absorption mode behind a light supported detonation wave

The light supported detonation wave (LSDW) propagation with the laser radiation absorption in a narrow layer behind wave’s front is considered in the paper alternatively to the volumetric energy source model usually used for the energy deposition simulation [1-7]. The next laser plasma flow features were revealed in [8] by methods of numerical simulation:1) laser plasma forms high-speed jet flow behind the LSDW front along the light beam propagation direction,2) jet parameters are close to an isentropic flow mode at significant distances from the LSDW front, therefor can be determined with a good approximation using the unsteady pressure solution for the point explosion model with a kinematic x-t transformation. These features allow one to determine the plasma momentum value (in the direction of a laser beam) of the optical breakdown as an additional factor of effect on gas flow, first indicated in [9]. For an argon flow, we used a comparative analysis of the results of numerical simulations obtained both accounting the absorbed energy only and the breakdown plasma momentum additionally acquired at the absorption of radiation behind the LSDW front.The experimental results of an optical discharge plasma in a subsonic argon flow are also presented. Pulse-periodic radiation with a frequency of 40 kHz and average power of 1.6 kW (peak power more than 30 kW) was generated by CO2-laser created in ITAM SB RAS. In order to obtain the LSDW mode by increasing a length of the breakdown plasma a focusing system f / d ≈ 9 was applied. A high-speed video camera with the exposure time of 1.0 μs, and the shooting speed of 200,000 frames / sec was used to record process. It has been established that the plasma dynamics has two successive stages: from the initial high-speed (of the order of 1 μs) propagation of the optical discharge to the subsequent lower-velocity gas-dynamic stage.

Influence of the relative momentum flux ratio on the mixing of hydrogen jets in an M=4 crossflow

The paper presents the results of numerical simulation of the 3D flows in a plane channel with the abrupt expansion. Sonic hydrogen jets are supplied from two circle orifices located opposite each other on the channel walls before the backward-facing step. The numerical simulations are carried out under the conditions of experiments performed at the hot-shot wind tunnel IT-302M ITAM SB RAS for the following flow parameters: Mach number at the entrance of the channel M = 3.84, the total temperature T0 = 1715 K, and the total pressure P0 = 6.5 MPa. Calculations were performed with a change in the jet supply pressure from 0.4 to 3.6 MPa, which ensures the variation in the jet-to-crossflow momentum flux ratio in the range of J = 0.7 ÷ 6. Mathematical modeling was performed in ANSYS Fluent based on the Reynolds-Averaged Navier-Stokes equations supplemented by the k-ω SST turbulence model. A comparison of the calculated and experimental data on the flow structure, as well as the static pressure distributions on the walls, indicates a satisfactory agreement. The calculated results made it possible to obtain a clearer understanding of the 3D flow structure in the channel and reveal the influence of the injection pressure on the level of mixing.

Comparison of Two Higher Accuracy Unstructured Scale-Resolving Approaches Applied to Dual-Stream Nozzle Jet Simulation

Dual-stream nozzle jet computations conducted using different numerical algorithms developed at Zhukovsky Central Aerohydrodynamic Institute (TsAGI) and Keldysh Institute of Applied Mathematics, Russian Academy of Sciences (KIAM RAS) are presented. The scale-resolving approaches of the DES family based on higher accuracy numerical methods are applied. The flow considered is studied experimentally at Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences (ITAM SB RAS). The jet is axisymmetric up to the effect of the supporting pylons, cold, subsonic at the inner nozzle exit, and supersonic at the outer nozzle exit. The computational data are compared with the experiment and with each other.

The correlation of the pulsations of flow in the settling chamber with the pulsations of supersonic flow

The relationship of the pulsations of flow in the settling chamber with the pulsations of supersonic flow in the test section of the T-325 wind tunnel of ITAM SB RAS was investigated. Experimental data on the correlation between flow pulsations in different sections of wind tunnel and efficiency of turbulence reducing system were obtained. The system of three-channel hot-wire measurements in subsonic and supersonic flows was tested.

Influence of sound-absorbing coatings on the development of disturbances in a flowing mixture of vibrationally excited gases

In the present paper, we study the development of disturbances on a solid (continuous) plate and on a plate covered with a sound-absorbing coating, both installed at an angle of attack in a hypersonic flow (M∞ = 8.44) of a vibrationally excited mixture of carbon dioxide with nitrogen. The rms fluctuations of pressure were measured on the surface of the plates in a short-duration IT-302M wind tunnel of ITAM SB RAS. The numerical simulation was performed on the basis of solving the two-dimensional unsteady Navier-Stokes equations and a two-temperature model of relaxation flows. In modeling a real porous coating, a skeletal model was used. The model is formed by square elements arranged in staggered order with a distance between elements equal to the diameter of the pores in the sound-absorbing material used in the experiment. Data on the dynamics of the disturbance development on the solid plate and on the plate with the sound-absorbing coating under different conditions of the incident flow are reported. The effect of various parameters of the sound-absorbing coating (depth, length, and location on the plate) was studied. It is shown that the sound-absorbing coating significantly (up to 50 %) suppresses the intensity of pressure fluctuations on the plate surface as compared with the solid surface. A good agreement between the calculated and experimental data on the pressure pulsations on the surface of the plates is demonstrated.

Программный комплекс для моделирования процесса впуска газа в произвольный набор приемных емкостей

The paper presents a software package for modeling the dynamic processes of the working gas passing through an arbitrary set of tanks connected by an arbitrary set of pipelines Calculations were carried out for various combinations of tank joints, including modeling complex aerodynamic installations of ITAM SB RAS.

Исследование пульсаций потока в форкамере и их связи с пульсациями сверхзвукового потока

Experimental study of the influence of flow pulsation in settling chamber on the supersonic free stream disturbances was carried out. Data on the pulsations in the settling chamber and the efficiency of deturbulization system as well as the correlation of pulsations of the flow of settling chamber and flow pulsations in test section of T-325 supersonic wind tunnel of ITAM SB RAS were obtained.

Influence of blunt-cone tip temperature on the laminar-turbulent transition in hypersonic boundary layers

In the present paper, we report on the results of a combined experimetal and numerical study of the laminar-turbulent transition at Mach number 5.95 in the boundary layers of 7-deg cones with a small nose-tip bluntness radius (down to 1.5 mm). The tip temperature of the model was varied in the range from 90 to 440 K. It was confirmed that the small nose-tip bluntness substantially shifts the position of the transition in downstream direction. This effect was also retained in testing the models with local heating/cooling of the cone tip. It is shown that for the experimental conditions implemented in the Transit-M wind tunnel, ITAM SB RAS, the local heating of blunt cone tips exerts almost no influence on the position of the transition. The local cooling of the cone tip with R = 1.5 mm leads to a shift of the transition position in upstream direction.

Testing of solid fuel ramjet with measurement of thrust characteristics in aerodynamic facilities

A design of an axisymmetric solid fuel ramjet consisting of a multi wedges nose air intake, solid fuel gas gene-rator, combustion chamber, and a nozzle, was developed. According to this design, a ramjet model for tests in the ground wind-tunnel facilities was fabricated. Experiments with solid fuel combustion were carried out in the Transit-M and T-313 wind tunnels, ITAM SB RAS, at air-flow Mach numbers М = 2.5−5.0. High values of the internal and net excess thrust were obtained.

Evolution of disturbances in the shock layer on a flat plate in the flow of a mixture of vibrationally excited gases

The results of the numerical and experimental investigations of the evolution of the disturbances in a hypersonic shock layer on a flat plate streamlined by a flow of the mixture of vibrationally excited gases are presented. The experimental study was conducted in the hot-shot high-enthalpy wind tunnel IT-302 of the ITAM SB RAS. The numerical simulation was carried out with the aid of the ANSYS Fluent package using the solution of the unsteady two-dimensional Navier−Stokes equations with the incorporation of the user-created modules and enabling the consideration of the vibrational non-equilibrium of the carbon dioxide molecules within the framework of the model of the two-temperature aerodynamics. It was obtained that an increase in the carbon dioxide concentration in the mixture with air leads to a reduction of the intensity of pressure disturbances on the surface. The efficiency (up to 20 %) of the method of sound absorbing coatings in the vibrationally excited flows of the mixture of the carbon dioxide and air has been shown.

Analysis and optimization of gas-thermal spray process in terms of condensed phase velocity and temperature

The paper presents the experimental results for velocity and tempertaure disibutions of the condensed phase in a plasma jet from the plasmatorch PNK-50 (design from ITAM SB RAS, Novosibirsk). The plasma jet is used at different operational modes for thermal spraying of nickel alloy powder PR-NKh16SR3. The measurements for average velocity (230–280 m/s) and temperature (2290–2410 K) of sprayed particles were matched to data on microhardness (630–710 HV) and porosity (1.7–13.5 %) of samples. Results were transferred into coating properties maps plotted in coordinates “arc current vs. torch offset” and “particle velocity vs. particle temperature”. Experiments demonstrated the change in parameters of condensed phase in the jet after performimg of maintenance job for the plasmatorch. We propose the method for adjusting the operational parameters of thermal spraying equipment using optical methods of control for particle velocity and particle temperature. The exemplary apparatus function of the plasmatorch was plotted; an approach is proposed for optimization and transfer of spraying technology of coatings with specified properties between equipment from different manufacturers, different class and power.

Equipment and technologies of air-plasma spraying of functional coatings

This article presents a short description of the DC plasma torch PNK-50 structural features (ITAM SB RAS, Novosibirsk) used for spraying of functional coatings with powder materials as well as gives the results of thermophysical and technological studies of spraying regimes. We present preliminary results of the plasma torch supersonic modification development and the results of industrial approbation of the plasma torch and of multi-purposes functional coatings deposition processes.