scholarly journals Influence of a rotating nozzle diaphragm on the characteristics of axial low-consumption turbines

2021 ◽  
pp. 86-89
Author(s):  
С.В. Чехранов ◽  
Р.Р. Симашов
Keyword(s):  
Experimental Studies ◽  
Point Of View ◽  
Working Fluid ◽  
Running Wheel ◽  
Flow Angle ◽  
Wide Range ◽  
Axial Turbines ◽  
External Loads ◽  
Large Flow ◽  
Low Consumption

Экспериментально исследуются различные компоновки турбинных ступеней с целью обеспечения многорежимности у осевых малорасходных турбин. Определено, что под многорежимностью понимается способность турбины поддерживать величину КПД неизменной, или с небольшими изменениями в достаточно широком диапазоне изменения внешних нагрузок. С новой точки зрения обращено внимание на то, что наиболее выраженными свойствами многорежимности обладают турбины в состав которых входит вращающийся сопловой аппарат. В этой связи рассмотрены авторские результаты экспериментальных исследований биротативных турбин с большим углом поворота потока и двух-ступенчатых осевых турбин с частичным облопачиванием рабочего колеса. Выявлено, у исследованных биротативных турбин свойство многорежимности проявляется при степени парциальности, близкой к единице и регулируется путем изменения соотношения частот вращения соплового аппарата и рабочего колеса. А у одновальных турбин с частичным облопачиванием рабочего колеса свойство многорежимности проявляется в широком диапазоне изменения степени расширения в турбине также при полном подводе рабочего тела. Various arrangements of turbine stages are experimentally investigated in order to ensure multiplicity of operating levels for axial low-consumption turbines. It has been determined that multiplicity is understood as the ability of a turbine to maintain the efficiency value unchanged, or with small changes in a fairly wide range of external loads. From a new point of view, attention is drawn to the fact that the most marked properties of operating levels multiplicity are relevant to the turbines which include a rotating nozzle diaphragm. In this regard, the author's results of experimental studies of birotative turbines with a large flow angle and two-stage axial turbines with partial blading of the running wheel are considered. It was revealed that in the investigated birotative turbines the property of multiplicity is manifested at a degree of partiality close to 1 and is regulated by changing the ratio of the rotation frequencies of the nozzle diaphragm and the running wheel. And in single-shaft turbines with partial blading of the running wheel, the multiplicity property is manifested in a wide range of changes in the degree of expansion in the turbine, also with full supply of the working fluid.

Experimental Studies of Leading Edge Contouring Influence on Secondary Losses in Transonic Turbines

2012 ◽  
Author(s):  
Ranjan Saha ◽  
Jens Fridh ◽  
Torsten Fransson ◽  
Boris I. Mamaev ◽  
Mats Annerfeldt
Keyword(s):  
Gas Turbine ◽  
Guide Vane ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Leading Edge ◽  
Secondary Flows ◽  
Noticeable Effect ◽  
Flow Angle ◽  
Wide Range ◽  
Contour Plots

An experimental study of the hub leading edge contouring using fillets is performed in an annular sector cascade to observe the influence of secondary flows and aerodynamic losses. The investigated vane is a three dimensional gas turbine guide vane (geometrically similar) with a mid-span aspect ratio of 0.46. The measurements are carried out on the leading edge fillet and baseline cases using pneumatic probes. Significant precautions have been taken to increase the accuracy of the measurements. The investigations are performed for a wide range of operating exit Mach numbers from 0.5 to 0.9 at a design inlet flow angle of 90°. Data presented include the loading, fields of total pressures, exit flow angles, radial flow angles, as well as profile and secondary losses. The vane has a small profile loss of approximately 2.5% and secondary loss of about 1.1%. Contour plots of vorticity distributions and velocity vectors indicate there is a small influence of the vortex-structure in endwall regions when the leading edge fillet is used. Compared to the baseline case the loss for the filleted case is lower up to 13% of span and higher from 13% to 20% of the span for a reference condition with Mach no. of 0.9. For the filleted case, there is a small increase of turning up to 15% of the span and then a small decrease up to 35% of the span. Hence, there are no significant influences on the losses and turning for the filleted case. Results lead to the conclusion that one cannot expect a noticeable effect of leading edge contouring on the aerodynamic efficiency for the investigated 1st stage vane of a modern gas turbine.

Optimization of the process of reproducing units of mass and volume of liquid in a stream, mass and volumetric flow rates of liquid for calibration units with weighing devices

2020 ◽  
pp. 60-64
Author(s):  
R. A. Korneev ◽  
A. R. Tukhvatullin ◽  
V. A. Fafurin ◽  
R. R. Nigmatullin ◽  
A. V. Shchelchkov
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Storage Tank ◽  
Experimental Studies ◽  
Working Fluid ◽  
Time Interval ◽  
Flow Rates ◽  
Wide Range ◽  
Flow Switch

The publication presents an experimental method for estimating the minimum time interval for filling a storage tank with a working fluid with a fixed geometry of the nozzle of the flow switch of the calibration plant when playing units of mass and volume of fluid in the flow, mass and volumetric flow rates of the fluid. Experimental studies were performed in a wide range of mass flow rate 11,10–83,26 kg/s (40–300 t/h) with repeated static weighing of the working fluid. The flow switch is made with a fixed geometry of the flow part of the nozzle exit, which is typical for a large number of calibration units in use in our country with weighing devices. The graphical dependences of the mass flow rate on the time of filling the storage capacity obtained from the research results are the basis for optimizing the process of reproducing units of mass and volume of liquid in the flow, mass and volumetric flow rates of the liquid for calibration plants with weighing devices. These graphical dependencies made it possible to formulate recommendations on the reasonable choice of the minimum interval for filling the storage tank with working fluid in the studied range of mass flow rate. Optimization has been tested and can be extended to calibration units with weighing devices from various manufacturers with individual design and operating parameters.

scholarly journals ANALYSIS OF THE CONDITIONS OF OCCURRENCE AND SUPPRESSION OF LATERAL VIBRATIONS IN MICROWAVE POWER FETS

2020 ◽  
Vol 258 (3) ◽  
pp. 4-21
Author(s):  
V. L. Aronov ◽  
E. M. Savchenko ◽  
D. M. Moseykin ◽  
A. D. Pershin ◽  
D. G. Drozdov
Keyword(s):  
Experimental Studies ◽  
Element Model ◽  
Excitation Power ◽  
Point Of View ◽  
Operating Conditions ◽  
Stability Factor ◽  
Lateral Instability ◽  
Wide Range ◽  
Amplifier Stage ◽  
The Stability

Lateral instability is inherent in power transistors structures, consisting of several simple transistors connected in parallel. The large number of transistor elements complicates the analysis of such instability. The introduction of suppressing resistors makes it possible to prevent the occurrence of lateral oscillations, however there are no unambiguous criteria for achieving stability this way. The matter is further complicated by the fact that transistor exhibits nonlinear operation in a typical amplifier stage, and the operating conditions in many cases correspond to a relatively wide range of frequencies. In this paper, we present an analysis of lateral instability of a power amplifier stage, created on a basis of modern GaN field-effect transistor (FET). We had designed all dies and circuits for this FET. The main feature of the analysis is that we carried it out in the time domain, which made possible to estimate the stability of the stage not only under the excitation power pulse, but also after the end of the pulse. Our approach makes it possible to assess the stability of the amplifier between the excitation pulses, which is very important from the operational point of view. We calculated the estimates of operational stability and stability factor using a simplified transistor model, with the multi-element model reduced to a two-element model. Nevertheless, the results of the estimates retain their significance in real conditions, when the introduction of suppressing resistors creates a significant margin of stability, including the actual operating frequency band of the stage. To date, the data we have obtained after the manufacture of the samples only partially confirms the calculated estimates, due to the complexity of managing the experimental studies. However, there are no recorded results, which deny our estimates for the model.

Theoretical Estimation of Minimum and Maximum Allowable Rotational Speed of Supercritical CO2 Inward Flow Radial Turbine

2021 ◽  
Author(s):  
Syed J. Hoque ◽  
Pramod Kumar
Keyword(s):  
Mach Number ◽  
Rotational Speed ◽  
Supercritical Co2 ◽  
Theoretical Models ◽  
Point Of View ◽  
Working Fluid ◽  
Flow Angle ◽  
Velocity Triangle ◽  
Operating Constraints ◽  
Radial Turbines

Abstract Supercritical CO2 inward flow radial turbines necessitate high operating speeds due to the high density of sCO2, especially in sub-MW scale power generation where rotational speeds can be in the range of 50k to 150k rpm. Although designing the turbine at these high rotational speeds is reasonable from the aerodynamic efficiency point of view but generally not practical to operate. A theoretical framework based on 1-D meanline analysis is built to evaluate the minimum and maximum rotational speed limits corresponding to a set of boundary conditions and operating constraints. The results show that minimum allowable speed depends on the inlet velocity triangle (IVT) and is constrained by inlet Mach number, inlet blade height, and inlet flow angle. On the other hand, maximum allowable speed depends on the outlet velocity triangle (OVT) and is constrained by outlet relative Mach number, outlet hub radius, and blade speed. The theoretical models are demonstrated from kilowatt to megawatt power levels, and the results are compared with commercial software and Balje’s Ns-Ds diagram. Although this study is highlighted in the context of supercritical CO2 as the working fluid, in principle, the same models are equally valid for any working fluid.

scholarly journals Heat Transfer in Evaporator of Thermal Sink in Presence of Subcooled Boiling Section

2021 ◽  
Vol 39 (2) ◽  
pp. 375-382
Author(s):  
Gennadiy A. Gorbenko ◽  
Pavlo G. Gakal ◽  
Rustem Yu. Turna ◽  
Artem M. Hodunov ◽  
Edem R. Reshytov
Keyword(s):  
Heat Transfer ◽  
Experimental Studies ◽  
Thermal Control ◽  
Working Fluid ◽  
Average Temperature ◽  
Thermal Control System ◽  
Wide Range ◽  
Ground Conditions ◽  
Longitudinal Thermal Conductivity ◽  
Spacecraft Thermal Control

The paper proposes a model of heat transfer in the evaporator of the spacecraft thermal control system. The model allows to calculate the average temperature of the evaporator wall and to build a "boiling curve" in a wide range of thermal loads. Adequacy of the model is confirmed by experimental studies on an aluminum thermal sink with high longitudinal thermal conductivity in the range of parameters typical for the thermal control systems of spacecrafts. Ammonia is used as a working fluid. The model might be recommended for use in zero gravity and normal ground conditions.

DEPENDENCE OF THE RAIL MFL TESTING DATA ON THE SPEED ACCORDING TO THE RESULTS OF COMPUTER SIMULATION AND EXPERIMENT

2020 ◽  
pp. 24-33
Author(s):  
A. G. Antipov ◽  
A. A. Markov
Keyword(s):  
Computer Simulation ◽  
Magnetic Flux ◽  
Eddy Currents ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Point Of View ◽  
Magnetic Sensors ◽  
Destructive Testing ◽  
Wide Range ◽  
Flux Leakage

Research of magnetic flux leakage signals of rail non-destructive testing in a wide range of scanning speeds is carried out. The results of three-dimensional computer simulation show significant changes in the distribution of the magnetic field in the depth of the rail at high motion speeds of the magnetizer. The appearance of low magnetization zones in the places most distant from the surface of the rail due to the influence of eddy currents is predicted. It is concluded that to detect defects that lie deep under the surface of the rail, magnetic sensors should be shifted towards the rear pole. The simulation results are in correct agreement with the results of experimental studies carried out on railway tracks at testing speeds up to 60 km/h. The effect of the formation at high scanning speeds of a tail magnetic flux behind the rear pole of the magnetizer is considered. Registration of this flux leakage data is promising from the point of view of detecting deep-seated defects, as well as separating signals from surface and internal flaws at high inspection speeds.

scholarly journals Development of Powered Support Hydraulic Legs with Improved Performance

2019 ◽  
Vol 105 ◽  
pp. 03025 ◽  
Author(s):  
Gennady Buyalich ◽  
Maxim Byakov ◽  
Konstantin Buyalich ◽  
Egor Shtenin
Keyword(s):  
Working Conditions ◽  
Working Fluid ◽  
Technical Solution ◽  
Lip Seal ◽  
Element Simulation ◽  
Wide Range ◽  
Powered Support ◽  
Improved Performance ◽  
External Loads ◽  
Sealing Gap

The paper gives a description of the technical solution for the design of a hydraulic leg piston for mechanized roof supports. This technical solution allows the sealing gap to remain almost constant in a wide range of pressures of the working fluid, while significantly improving the working conditions of the lip seal on the piston. This technical solution consists in the fact that, on the side of the piston cavity of the hydraulic leg, the piston contains a sleeve with a seal located on it, which under the action of the pressure of the working fluid deforms in the radial direction, compensating for an increase in the diameter of the working cylinder. In this case, the described technical solution is not subject to inertia and is able to work with static and with dynamic external loads on a hydraulic leg. The results of a comparative finite-element simulation of the stress-strain state of a hydraulic leg at the junction of the piston and the working cylinder are given for the 360 mm dia hydraulic leg of Glinik support with serial and proposed pistons. It is shown that with the proposed piston, when the pressure of the working fluid in the piston cavity is 62 MPa, the change in the radial sealing gap is less than 20 times compared with the serial design.

scholarly journals Determination of the Idle Mode of the Stage of Axial Turbine during Operation at Partial Loads

2020 ◽  
Vol 65 (1) ◽  
pp. 103-109
Author(s):  
Aleksandr Shubenko ◽  
Vladimir Goloshchapov ◽  
Daria Senetska ◽  
Oleksandr Senetskyi
Keyword(s):  
Experimental Studies ◽  
Rotor Blades ◽  
Working Fluid ◽  
Idle Mode ◽  
One Dimensional ◽  
Operating Modes ◽  
Wide Range ◽  
The One ◽  
Partial Loads

On the basis of the one-dimensional theory of calculating the operation of steam turbine stages the method for determining the idle mode, the initial data for which are the geometric characteristics of the blade rows is proposed. Formulas have been obtained that make it possible to calculate the efficiency in the proximity of Rotor Blades (RB) at operating modes from nominal to the idle mode, depending on the flow rate of the stage and taking into account the use of kinetic energy with the runaway velocity and losses arising at off-design angles of flow on the Rotor Blade (RB). The results of possible computational studies and their comparison for an incompressible working fluid with the results of experimental studies showed the good possibilities of the proposed method for determining the idle mode in a wide range of the characteristics of stages.

Colorimetric research of self-luminous objects in software and hardware environments by the method of multidimensional scales implementation

2020 ◽  
pp. 43-50
Author(s):  
Yauheniya N. Saukova
Keyword(s):  
Metrological Traceability ◽  
Point Of View ◽  
Intermediate Precision ◽  
Technical Vision ◽  
Wide Range ◽  
Chromaticity Coordinates ◽  
Unity Of Measurements ◽  
Software And Hardware ◽  
Luminous Objects ◽  
Reference Samples

It is shown that the issues of metrological traceability for extended self-luminous objects with a wide range of brightness have not yet been resolved, since the rank scales of embedded systems are used for processing digital images. For such scales, there is no “fixed” unit, which does not allow you to get reliable results and ensure the unity of measurements. An experiment is described to evaluate the accuracy of determining the intensity (coordinates) of the color of self-luminous objects. In terms of repeatability and intermediate precision compared to the reference measurement method, the color and chromaticity coordinates of self-luminous objects (reference samples) were determined by their multiple digital registration using technical vision systems. The possibilities of the developed methodology for colorimetric studies in hardware and software environments from the point of view of constructing a multidimensional conditional scale are determined.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

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