Gas-dynamic Characteristics Research Articles

Complex approach to aerodynamic design of inlet ducts with submerged vortex-free air intakes

The paper shows the possibility of improving gas-dynamic characteristics of a submerged air intake and presents a technology of developing design solutions according to the principle of conformity to the flow lines. The gas-dynamic principle of shaping is provided by means of computer-aided integrated technologies of design and application of numerical visualization methods as design tools. The revealed regularity of the working process of the external streamline of the preceding airframe surfaces unambiguously defines the fundamental design distinctions of the conformal air intake in the form of the converging side edges on the stream and determines its advantages over the analogs.

Surface electromagnetic actuator in rarefied hypersonic flow

Hypersonic flow past the surface with sharp edge is investigated. This surface forms an obtuse angle therefore the shock wave generated by the leading edge interacts with the surface. The effect of influence of the surface direct current discharge and a transverse magnetic field on the gas dynamic characteristics is investigated. To solve this problem a numerical simulation is used. The calculation model includes the set of the Navier – Stokes and energy conservation equations, as well as equations of electrodynamics in the ambipolar approximation, and the Poisson equation.Results of numerical modelling the gas dynamics and electrodynamics of gas discharge with magnetic field show the change in the structure of the shock-wave interaction with surface far from location of the gas discharge. It is shown that the low-current glow discharge can be used as an electromagnetic actuator in hypersonic flows.

Physico-mathematical modeling methods for the pressure distribution determination in the gas-dynamic bearing gap of the ball gyroscope

The considering problem in the article connects with solution methods of the specific questions in gas-dynamic lubrication theory. The comparative analysis of analytical and numerical methods for the calculating gas-dynamic bearing characteristics is provided. The main applying aspects of them for the solving of specific gas lubrication theory points are presented. This research is carried out for the investigated gap bearing geometry for the designed ball gyroscope construction. The main mathematical equation and results of developed numerical simulation for the pressure distribution determination are shown.

Gas dynamic characteristics of glow discharge chamber for functional coating deposition.

In article shown conditions of glow discharge existence at low pressures. Described possibility of organizing glow discharge at very low pressures due to the supersonic gas flow in a limited area of the discharge chamber. Procedure of supersonic flow regime calculating in vacuum chamber for coating deposition shown.

ВЛИЯНИЕ ПЫЛЕВОЙ ЭРОЗИИ НА ГАЗОДИНАМИЧЕСКИЕ ХАРАКТЕРИСТИКИ ОСЕВОГО КОМПРЕССОРА ГТД

The results of flow simulation of an axial multi-stage compressor of a gas turbine engine are presented. The relation between the main gas-dynamic characteristics of the compressor and operating time in dusty atmosphere are established. The estimation of the maximum operating time of the engine in terms of loss of the gas-dynamic stability of the compressor is performed.

Approximate method for estimating plasma ionization characteristics based on numerical simulation of the dynamics of a plasma bunch with a high specific energy in the upper ionosphere

The spatiotemporal pattern for the development of a plasma cloud formed in the ionosphere and the main cloud gas-dynamic characteristics have been obtained from 3D calculations of the explosion-type plasmodynamic flows previously performed by us. An approximate method for estimating the plasma temperature and ionization degree with the introduction of the effective adiabatic index has been proposed based on these results.

PARALLEL COMPUTATIONS IN STUDIES OF DEPENDENCE OF GAS DYNAMIC PARAMETERS OF UPWARD SWIRLING FLOW OF GAS ON BLOWING VELOCITY

The rectangular parallelepiped explicit difference schemes for the numerical solution of the complete built system of Navier-Stokes equations. These solutions describe the three-dimensional flow of a compressible viscous heat-conducting gas in a rising swirling flows, provided the forces of gravity and Coriolis. This assumes constancy of the coefficient of viscosity and thermal conductivity. The initial conditions are the features that are the exact analytical solution of the complete Navier-Stokes equations. Propose specific boundary conditions under which the upward flow of gas is modeled by blowing through the square hole in the upper surface of the computational domain. A variant of parallelization algorithm for calculating gas dynamic and energy characteristics. The results of calculations of gasdynamic parameters dependency on the speed of the vertical blowing by the time the flow of a steady state flow.

Influence of counterpressure on gas dynamic characteristics of the outlet straightener of low pressure compressor in heterogeneous flow

Influence of counterpressure on gas dynamic characteristics of the outlet straightener of low pressure compressor in heterogeneous flow

Theoretical Analysis of Changing Gas Dynamic Characteristics of the Dust Filter with a Short Diffuser While in Operation

The results of the experimental and numerical studies of the dust filter with a short diffuser at various size of a filter element clogging are given in the paper. The connection between the value of the filter clogging and the growth of hydraulic losses in a flowing part of the filter is found, the emergence of this effect from the point of view of redistribution of velocities and vortex formation of a stream is proved. Satisfactory agreement between the calculated and the experimental results is obtained.

Gasdynamic characteristics of compressor cascades with special profiling of blade rows

The results of studying gasdynamic characteristics in respect to deviation angles and optimal incidence angles of compressor cascades with special profiling of blade rows that were obtained in the process of balancing calculations using the parameters measured in the clearances between blade rows of the stages of several multistage compressors are given.

Modernization of exhaust hood of low-pressure cylinder of a cogeneration turbine T-250/300-23.5

An option of modernization of an exhaust hood for a low-pressure cylinder of a T-250/300-23.5 series turbine is presented in order to increase its effectiveness in a wide regimes range. An influence of a number of design decisions on gas-dynamic and energy characteristics of an exhaust compartment is considered. The investigation is carried out by the numerical simulation of a viscous wet steam flow through the exhaust compartment consisting of a last stage and an exhaust hood. A comparison of the calculated and experimental data is presented.

Combined Cycle Gas Turbine (CCGT) with Freon Steam Turbine

The article considers the prospect of a combined-cycle plant with freon as the working fluid of the steam turbine. Methodical approach to the study of such plants is expounded. For the option, CCGT with gas turbine M701G2 and use of freon R134a results of calculations of technical and economic efficiency, gas-dynamic characteristics, design-layout parameters are shown. The effectiveness of investments has been assessed.

Transient Gas Turbine Performance Diagnostics Through Nonlinear Adaptation of Compressor and Turbine Maps

Gas turbines are faced with new challenges of increasing flexibility in their operation while reducing their life cycle costs, leading to new research priorities and challenges. One of these challenges involves the establishment of high fidelity, accurate, and computationally efficient engine performance simulation, diagnosis, and prognosis schemes, which will be able to handle and address the gas turbine's ever-growing flexible and dynamic operational characteristics. Predicting accurately the performance of gas turbines depends on detailed understanding of the engine components behavior that is captured by component performance maps. The limited availability of these maps due to their proprietary nature has been commonly managed by adapting default generic maps in order to match the targeted off-design or engine degraded measurements. Although these approaches might be suitable in small range of operating conditions, further investigation is required to assess the capabilities of such methods for use in gas turbine diagnosis under dynamic transient conditions. The diversification of energy portfolio and introduction of distributed generation in electrical energy production have created need for such studies. The reason is not only the fluctuation in energy demand but also more importantly the fact that renewable energy sources, which work with conventional fossil fuel based sources, supply the grid with varying power that depend, for example, on solar irradiation. In this paper, modeling methods for the compressor and turbine maps are presented for improving the accuracy and fidelity of the engine performance prediction and diagnosis. The proposed component map fitting methods simultaneously determine the best set of equations for matching the compressor and the turbine map data. The coefficients that determine the shape of the component map curves have been analyzed and tuned through a nonlinear multi-objective optimization scheme in order to meet the targeted set of engine measurements. The proposed component map modeling methods are developed in the object oriented matlab/simulink environment and integrated with a dynamic gas turbine engine model. The accuracy of the methods is evaluated for predicting multiple component degradations of an engine at transient operating conditions. The proposed adaptive diagnostics method has the capability to generalize current gas turbine performance prediction approaches and to improve performance-based diagnostic techniques.

Density, porous structure, and gas-dynamic characteristics of finely grained graphites (a review)

The results of the statistical processing of data on the determination of the apparent (ρa) and pycnometric (ρp) densities and the accessible (open) porosity (Pa) of samples cut out in parallel (||) and perpendicularly (⊥) to the axis of extrusion of the workpieces of fine-grained graphites (>90% of coke filler particles of size ρa|| by 1.2% (0.019 g/cm3) and Pa⊥ < Pa|| by 3.3% (0.9% in the absolute value) or by 1.3% (0.024 g/cm3) and (0.92%), respectively, for the same graphite with high-temperature pitch. The capabilities of mercury porosimetry in the study of the porous structure of graphites and other carbon materials are demonstrated.

ACCOUNTING INFLUENCE OF CENTRIFUGAL FORCE IN THE NUMERICAL MODELING OF RISING SWIRLED GAS FLOW

In work the consistent inclusion of centrifugal force in the numerical calculations of three-dimensional gas-dynamic characteristics of the unsteady flow of compressible viscous heat-conducting gas in an upward swirling flow caused by the vertical cold blowing. Provides detailed conversion of the complete system of Navier-Stokes equations associated with consistent view of the centrifugal force. Results of thermodynamic calculations and comparisons, speed and power characteristics of emerging upward swirling flows. There was a slight influence of the centrifugal force on the basic parameters of the gas-dynamic study of complex flows of gas.

Numerical Analysis of Gasdynamic Characteristics of Vortex Ring

In the framework of the research the authors have solved the problem of formation and dynamics of the vortex ring. Intensive turbulent vortex rings produced by piston generators have been considered. The research has been carried out on the basis of numerical simulations in fluid dynamics program ANSYS CFX using the high-performance computing system. We have obtained the dynamic and geometrical characteristics of the vortex ring on the basis of numerical experiments. The results are in agreement with self-similar law of vortex ring dynamics and experimental results. The authors have analyzed the influence of piston velocity on the vortex ring properties. The structure of the generated vortex ring has been found to be stable, which is important for experimental studies of acoustic properties of this object.

Flow structure formed due to interaction of a supersonic jet with a porous obstacle

Results of studying impingement of a supersonic underexpanded air jet onto a finite-thickness porous metal obstacle whose frontal plane is normal to the jet axis and whose side surface is impermeable for the gas flow are reported. The case of a non-porous obstacle of the same diameter is considered for determining the effect of porosity on gas-dynamic characteristics of jet–obstacle interaction.

Regularities of Physical Processes in Hybrid Solid-Propellant Rocket Engines

Safety and economy of delivery of a payload into its intended orbit necessitate the continued improvement of engine design for rocket boosters. A possible compromise in the requirements implied by this need is connected with the use in space systems of hybrid solid-propellant engines (HSPEs) working with liquid or gaseous oxidizers. Physical notions about the processes taking place during combustion of propellants and about heat and mass exchange were generalized in the review in [1], which, however, lacks a methodical basis for an analysis of interior-ballistic and gasdynamic processes in hybrid engines covering the entire time of their functioning. This brings us to the fact that a number of aspects of the processes taking place in hybrid solid-propellant rocket engines have received very little attention. Therefore, the goal of the present paper is to model key features of the physical processes taking place in hybrid solid-propellant rocket engines. Since the working process of an HSFE includes various periods of operation (substantially non-steady-state launch-and-ignition, depressurization, and an extended period of quasi-steady-state burning), the most optimal model within the framework of a unified approach is precisely the non-steady-state model. For the quasi-steady-state case, modeling of non-steady-state processes is the basis of one of the most effective methods for solving interior ballistics problems – the so-called relaxation method [2]. Typical schemes of hybrid engines are shown in Fig. 1. The basic equations for calculating the working parameters of an HSPE are formulated for the scheme of the solution domain presented in Fig. 2. The dynamics of the gas-dynamic characteristics is investigated in three subdomains of average parameters (oxidizer tank and head and prenozzle volumes of the combustion chamber), and also in the subdomain of a one-dimensional description of flow in the burning fuel channel. We consider a mechanical mixture of gases with arbitrary number of components, these being the oxidizer, the combustion products of the flammable components, possibly a multicomponent grain of fuel, and products of the gasification of thermal-insulation materials. The mathematical model is formulated on the basis of assumptions [2, 3] in which the conservation laws are augmented by two specially constructed equations for calculating the variation of the thermodynamic parameters of the mixture (the gas constant R and the isobaric specific heat Cp), and also two equations for calculating the viscosity of the gas mixture μ. In addition, an equation for the mass fraction of oxidizer C is added, which together with the viscosity coefficient of the mixture is needed to concretize the right-hand sides of the equations – to calculate the burning rate, the friction density ffr, and the heat loss density q. The mathematical model takes account of the physical character of the combustion process in the HSPE – the dependence of the rate of gasification of the solid propellant on the mass flux density of the oxidizer blowing the combustion surface. The balance relations for the mass of the gas were constructed taking into account the expenditure

Gasdynamic characteristics of outlet straightener of gte low pressure compressor at underexpunded angles of flow inlet

The main hydrodynamic characteristics of the outlet straightener (OS) between LPC and HPC of the GTE have been discussed. OS is a stationary cage of the strait radial profiles which has the functions of the barring set and the guide grid simultaneously. From the hydrodynamics point of view OS should produce the homogeneous outlet flow with the least possible resistance. The main hydrodynamic characteristics of OS may change when the parameters of the outlet flow deviate from the calculated ones which is caused by the GTE operation in transient modes and as well as the heterogeneity of the velocity field at the outlet of the LPC [1] . The aim of the research is to receive a data about the variations of the main hydrodynamic characteristics of the OS as a result of deviation of the inlet flow angle in order to have the possibility to make the highly-efficient straightener and to estimate the efficiency of the gas turbine engine in general. The hydrodynamic characteristics of the OS were numerically investigated using the FLOW VISION fundamentals. The segment of the fully dimensional OS of the stationary gas turbine engine was used as a calculation object. It had two neighboring blades passage with strait radial blade between them. The axis x,y,z of the right angle coordinate system were coincided with circumferential, radial and axial directions, respectively. The calculations were provided by using the datum- model of the FLOW VISION turbulent flow - “ weakly-compressible liquid “ which is based on the standard “k-e model of turbulence”. The obtained results of the numerical calculation reflect the common tendency of debasement of almost all the hydrodynamic characteristics of OS such as the total pressure recovery coefficient, coefficient of the full hydrodynamic losses, condition of the velocity field at the exit and others when the angle of inlet flow slightly increases. They can be useful for the estimation of the reduction of efficiency the gas turbine engine in general.

A Design Experiment of the Gas Flow in the Stages of Centrifugal Compressors Using the Bundled Software ANSYS CFX and Taking into Consideration the Real Properties of the Compressed Medium

This scientific paper gives numerical simulation data for the natural gas flow in the high pressure centrifugal compressor stage for the two different models of the working medium (ideal gas model and real gas model Soave – Redlich – Kwong). Calculated data and available experimental data were compared and the graphic comparison of obtained integral gas-dynamic characteristics was given. The real gas model provided the data that are more or less similar to experimental data, which speaks in favor of its use in comparison with the ideal gas model. It should be noted that at this stage of the experiment the simulation was carried out not taking into consideration the gas flow in the side chambers between the stator and the rotor elements of the compressor, whose influence on the characteristics of the high pressure compressor is especially high.