Investigation Of Gas Dynamics Research Articles

FORMATION OF THE SUPERSONIC HETEROGENEOUS STREAMS IN THE GASDYNAMIC ACCELERATORS WITH GREAT ELONGATION

The present article describes results of the experimental and theoretical investigation of gas dynamics and heat exchange in the course of a supersonic flow of the gas-powder mixture within the axially symmetric gas-dynamic accelerators, which have small critical cross-sections (dcritical from 1 to 3 mm) and substantial elongation (L/dcritical from 70 to 200). The necessity of performance of such investigations was determined by two aspects. The first is the development of the innovative technologies with the purpose of formation of the heat-resistant coatings and other coatings with various functions and necessary properties (formation of such coatings with the help of supersonic heterogeneous streams). The second is the creation of the supersonic heterogeneous streams, which are required for the development of experimental investigations of processes of the erosive and corrosive wear of structural components of the high-speed air vehicles, which conduct flights in atmospheric anomalies (rain clouded sky and dust-in-air conditions). This study describes the entire cycle of the experimental investigations, which were performed with the purpose of construction of the more reliable mathematical model of flow of the nonisentropic heterogeneous streams in the gas-dynamic accelerators with great elongation. The viscous gas flow parameters were calculated using the classical model of a flat boundary layer. The value of the characteristics of the carrier gas flow, the dispersion of particles and their material for accelerating particles in a heterogeneous flow were found out. The study showed that the design of gasdynamic micro accelerators must be carried out taking into account the increase in the thickness of the boundary layer along the walls of the particle accelerator. In addition, this article presents a more detailed description of gas dynamics of flow and heat exchange of the heterogeneous mixtures within supersonic gasdynamic accelerators with mass concentration of the powder particles ("К-phase") in the stream up to 15%.

Heat transfer simulation of unsteady swirling flow in a vortex tube

Effectiveness of not-adiabatic vortex tube application in the cooling systems of gas turbine blades depends on characteristics of swirling flows formed in the energy separation chamber. An analysis of the flow structure in the vortex tube channels has shown a presence of a complex three-dimensional spiral vortex, formed under relatively high turbulence intensity and vortex core precession. This indicates the presence of a significant unsteady flow in the energy separation chamber of the vortex tube that has a great influence on convective heat transfer of the swirling flow to the inner surface of tube. The paper contains the results of investigation of gas dynamics and heat transfer in the vortex tube taking into account the flow unsteadiness.

Numerical investigation of gas dynamics in the pyro actuator found in the mechanism for unfolding aerodynamic surfaces

The article presents a mathematical model of a pyro actuator found in the mechanism for unfolding aerodynamic surfaces of aircraft, which includes a collector system. The mathematical model proposed takes into account linked gas dynamic processes in the internal pyro actuator chambers and the dynamics of its mechanical traveller. We supply results of numerically investigating the main parameters of working body flow, obtained by using the ANSYS software package.

Thermal and gas dynamic investigations at Lastarria volcano, Northern Chile. The influence of precipitation and atmospheric pressure on the fumarole temperature and the gas velocity

Fumaroles are hydrothermal manifestations commonly associated with active volcanoes. The dynamics of fumaroles are affected by interactions with internal and external factors, however, hazardous access and corrosive gases have so far limited successful case studies. In this study we report and discuss the results of continuous thermal monitoring carried out on three high temperature (>250°C) fumaroles at the Lastarria volcano Chile, together with simultaneously measured meteorological parameters from December 2013 to March 2016. In addition, the dynamic pressure and the CO2 concentration were recorded in a fourth vent. The investigated sites are located in the largest and most dominant fumarole field which developed in a fracture system on the north-west flank of the volcanic edifice.We detect external factors controlling the fumarole temperature and the dynamic gas pressure, for a better understanding of changes in these parameters and, consequently, to improve the evaluation of volcanic and hydrothermal activity.Selected fumaroles showed a continuous decrease in temperature, or remained unbiased from this trend showing that the influence of external effects on outlet temperature is strongly site dependent. But generally, significant decreases in all vent temperatures can be observed in response to intensive precipitation. Diurnal variations occur only in the coolest fourth fumarole, where gas temperature, gas pressure and CO2 concentration are inversely correlated with atmospheric pressure. Small barometric pressure reductions account for an increase in mass flow subsequently resulting in a higher temperature and CO2 concentration.The temperatures and thermodynamic properties of the fumarolic gas and infiltrated precipitation water were used to calculate the amount of discharging gas from the investigated field with about 67×106m3 per day which is equivalent to 3545tons.

Borehole tool for studies in coalbed degasification wells

The paper presents a downhole tool designed for gas-dynamic research to be carried out in coalbed methane drainage holes. Structurally, the tool has a twin-packer design. The tool allows hydraulic fracturing, gas-dynamic investigations using indicator diagrams and pressure drop and recovery curves, and local destressing of coal.

Application of stereolithography prototypes for gas dynamic tests

Planning any pilot study brings up the question of producing test specimens. These are quite often rather complex, consisting of several individual parts put together. Test specimens are very expensive and take long time to produce using traditional technologies of production because of high accuracy required of them and absence of quantity production. Dynamically developing additive technologies (rapid prototyping) make it possible to produce plastic and metal parts of any form using a uniform technology. Therein the complexity of the part shape practically does not increase the manufacturing complexity and the need for equipment is absent or minimal. Laser stereolithography (SLA – Stereolithography Laser Additive) is one of the earliest and most precise technologies of 3D-printing. The paper presents the experience of using a prototyping machine on the basis of laser stereolithography for the production of experimental specimens for gas-dynamic investigations. On the basis of synthesis of this experience, basic requirements for similar experimental specimens are formulated: durability, rigidity and hardness, impermeability for gas or liquid, resistance to working fluid diffusion, resistance to chemically aggressive fluids (including fuels, oils). Comparison of different technologies of prototyping shows that stereolithographic models meet all listed requirements better than others.

Application of stereolithography prototypes for gas dynamic tests

Planning any pilot study brings up the question of producing test specimens. These are quite often rather complex, consisting of several individual parts put together. Test specimens are very expensive and take long time to produce using traditional technologies of production because of high accuracy required of them and absence of quantity production. Dynamically developing additive technologies (rapid prototyping) make it possible to produce plastic and metal parts of any form using a uniform technology. Therein the complexity of the part shape practically does not increase the manufacturing complexity and the need for equipment is absent or minimal. Laser stereolithography (SLA – Stereolithography Laser Additive) is one of the earliest and most precise technologies of 3D-printing. The paper presents the experience of using a prototyping machine on the basis of laser stereolithography for the production of experimental specimens for gas-dynamic investigations. On the basis of synthesis of this experience, basic requirements for similar experimental specimens are formulated: durability, rigidity and hardness, impermeability for gas or liquid, resistance to working fluid diffusion, resistance to chemically aggressive fluids (including fuels, oils). Comparison of different technologies of prototyping shows that stereolithographic models meet all listed requirements better than others.

Numerical investigation of gas dynamics in nozzles of small-dimensioned gas generators and flowing out jets

The paper presents the statement of the problem of numerical simulation of gas dynamics of nozzles and jets of small-dimensioned gas generators of supersonic flows based on boundary layer and Navier-Stokes equations and the results of solving it. The results of the numerical studies of gas dynamics of nozzles and jets for standard small-dimensioned gas generators with a thrust 6 N and 12 N are given. Significant potential of increasing specific impulse by optimizing the contour of supersonic nozzles of small-dimensioned gas generators are exhibited. The process of shock wave formation in the supersonic part of the nozzle of a standard smalldimensioned gas generator is numerically investigated. Significant impact of shock waves on the gas dynamics of vacuum jets is illustrated.

A laser interferometry instrumental complex for recording the velocity of moving surfaces in explosive experiments

The instrumental complex described is intended for recording the velocity of motion of the surface of a sample under study exposed to impact-explosion loading in gas-dynamic investigations of properties of structural materials. The velocity is determined from the Doppler wavelength shift of reflected radiation of the probing laser measured by the interferometry method. A solid-state laser with a pulse duration of >50 μs, an average power of at least 50 W, and a system for controlling the resonator quality factor, which ensures radiation stabilization for maintaining an almost rectangular pulse shape, is used as the probing-radiation source.

A test bench for gas-dynamic investigations of exhaust diffusers and hoods of turbines

This article is concerned with methodological principles of experimental investigation of gasdynamics of exhaust diffusers and exhaust paths of turbines. The design of an experimental “stage—diffuser” aerodynamic test bench and the experimental technique used are presented. Coordinate-spacing devices used for traversing three-dimensional flow in components of the flow path of a model and the scheme of a measurement technique are described.

Gas dynamic investigation ofrotating gas accretion

Abstract Gas dynamic features of slowly rotating axially symmetric gas accretion on to a gravitating centre are investigated. The process of flow restructuring is studied as the angular velocity of accreting matter approaches the Keplerian angular velocity. For spherically symmetric accretion the conditions are found of the existance of a steady-state state supersonic solution for various extertnal boundary conditions. A numerical study is performed on the basis of the Lax-Friedrichs-type second-order numerical scheme with an implicit approximation of the term in the Euler equations.

On possible signatures of heavy neutrino balls in active galactic nuclei

After the discovery of quasars, theories of active galactic nuclei (AGN) were constructed which focused on the investigation of gas dynamics in the gravitational potential of a black hole. In this paper we study the influence of a possible dark matter neutrino ball on the accretion process in AGN, and investigate possible observable signatures of such a ball which is supported by degeneracy pressure. We find that, if such balls exist in the vicinity of AGN, they will cause a bump in the IR region of the emitted spectrum which is, in fact, observed for several AGN. We also find that, if the bump corresponding to ∼ 1000 K in the spectrum of the typical radio-loud quasar 3C 273 is due to a neutrino ball, then our model implies a mass of the black hole of 108 M⊙, a ball mass of 4 × 109 M⊙ and, in turn, a neutrino of mass 3 keV/c2.

Investigation of gasdynamics of a model with combustion in a shock tunnel

Investigation of gasdynamics of a model with combustion in a shock tunnel

Numerical Gas-Dynamic Investigation of the Whimper Model for the Formation of Planetary Nebulae

The suggestion that the shells of planetary nebulae may be formed at the interface between two stellar winds of different velocity (“Not with a bang, but a whimper”) (Kwok, Purton and FitzGerald, 1978, Astrophys. J. 219, L 125) is investigated using the ‘beam scheme’ (Sanders and Prendergast, 1974, Astrophys. J. 188, 489) adapted to a system with spherical symmetry. Initial conditions include the remnant wind from the red giant phase and a highspeed wind from the hot nucleus ( (two tests), v = 103km s−1). The collision began at a radial distance of 200 AU. A third test at 50 AU indicated that the end result was insensitive to the details of the transition from one mass-loss mechanism to the other.

Investigation of gasdynamics of a vapor stream in heat pipes under turbulent conditions

Results are presented of an experimental investigation of the gasdynamics of a turbulent vapor stream in heat pipes, during simultaneous operation of the evaporation section, the adiabatic section, and the condensation section.

1304. Vacuum installation for gas-dynamic investigations: LA Vasil'ev et al, Soviet Patent, class F 04 b, 37/08 and G 01 m, 9/00, No. 377,546, claimed 19/10/70, published 17/4/73 ( in Russian)

Research indicates that active control concepts have promise in mitigating numerous adverse phenomena associated with the aeromechanics of lifting surfaces. These techniques are being applied to delay stall of fixed wing aircraft, as well as to eliminate or mitigate vibratory loads, blade–vortex interaction, and dynamic stall of the flow about rotorcraft and wind turbine blades. These phenomena are nonlinear and unsteady for dynamic systems, which add yet another layer of complexity on the physics of the flow. While a plethora of different active control techniques is being explored, the use of trailing edge flaps appears to be one of the more viable and cost-effective concepts. Static multi-element airfoils and wings have been analyzed computationally, but little exists on the ability to model these when the airfoil and flap are dynamic. The costs associated with modeling the gap between the airfoil and flap have led to approximations where the flap is modeled only as a morphed tip of the airfoil (no gap). Using a hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy-Simulation turbulence technique, an oscillating flapped airfoil has been studied to determine the influence of modeling the gap on the performance and acoustic signature of the airfoil. Results are compared with the experimental data to confirm the validity of the computational approach. Both attached and separated (dynamic stall) oscillating flows are examined. The physics within the gap are found to be important for the airfoil performance when stall is encountered, as well as when acoustic signatures are required.

Generalized Analysis of Shearing Interferometers as Applied for Gas Dynamic Studies

Shearing interferometers are classified as instruments in which interference is produced between rays that are sheared in the test object by a small lateral distance. When applied to gas dynamic investigations these interferometers respond to changes of the gradient of the gas density in the test field. A generalized first-order analysis is described that applies to all arrangements of such shearing interferometers and emphasizes the application for the study of compressible gas flows.

Laser Interferometer for High Sensitivity Measurements on Transient Phase Objects

A He-Ne laser beam is sent through a common path differential interferometer and the interference signal is detected by a p-i-n photodiode. Weak phase objects can be examined because optical path changes can be resolved to 0.1 A with a time resolution of about 20 ns. Examples for different gas-dynamic investigations show good results and demonstrate the wide field of application for this type of laser interferometer.

Some data obtained with an experimental MHD-power plant

In the report a brief account is given of a large experimental complex MHD-power plant for open-cycle operation with combustion products of natural gas. The main distinguishing feature of such a plant in comparison with existing ones consists in the fact that with its help it is possible to investigate not only the MHD-generator itself but also other complicated components of MHD-power plants as well as to investigate the operation of major components of the MHD-power plant. Presumably the question as to the prospective application of open-cycle MHD-power plants for large-scale power generation can be answered only after the solution of complicated research and engineering problems associated with the development of a large-scale commercial pilot plant. Another distinguishing feature of the described plant lies in the fact that it is intended for a long-period service. The report gives main parameters of the plant, describes the technological scheme and its major components: the combustion chamber, the MHD-channel, the magnet system, facilities for injection and recovery of ionizing seeding, high-temperature air preheaters, end heat-exchanger systems, current inverting systems, etc. Also the report gives a summary of the obtained experimental results. The MHD-generator output power amounted to 30 kW. The comparison of the results on thermal and gasdynamic investigation carried out in the MHD-channel with theoretical calculations made on a refined one-dimensional flow model showed that they agree After the investigations carried out on the described plant conditions were obtained not only for further wide-scale magnetohydrodynamic thermophysical and electrophysical investigations of MHD-power plants but also for the continuation of the work for investigating a simultaneous operation of the MHD-generator with other components of the plant as well as for developing more rational designs of the components and conditions for their operation.