scholarly journals Hydraulics of smoothly streamlined Venturi channels of critical depth

2019 ◽  
Vol 91 ◽  
pp. 07021
Author(s):  
Andrey Zuikov ◽  
Tatiana Suehtina
Keyword(s):  
Functional Relationship ◽  
Rate Coefficient ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Coefficient Distribution ◽  
Flow Rate Coefficient ◽  
Arbitrary Section ◽  
Venturi Flume ◽  
Empirical Coefficients ◽  
Engineering Hydrology

The article relates to the field of hydraulics and engineering hydrology and is devoted to a study of fluid flow in a non-flooded Venturi channel. The purpose of the work is improvement of methods for calculating profiles and hydraulic characteristics of a Venturi flumes used for measurement of water flow rates in open channels and rivers. Research methods are analytical with experimental verification. A functional relationship is obtained between the Froude number in an arbitrary section of the Venturi channel and its width normalized by the width of the critical section. It is established that within a rectilinear gorge portion of a Venturi channel, the flow is unstable, which is related to the proximity of its parameters to the critical ones. The method of optimization of a profile of a Venturi channel with a dividing cross-section in a gorge that does not contain empirical coefficients is considered. It is shown that the proposed method allows determining all main geometric parameters and hydraulic characteristics of the Venturi flume, including its flow rate coefficient, distribution of depths and flow velocities along the length of a flume with a relative error of ±1%.

EXPERIMENTAL STUDY OF BAR FORMATION IN SAND BED CHANNEL

2016 ◽  
Vol 78 (5-3) ◽  
Author(s):  
Duratul Ain Tholibon ◽  
Junaidah Ariffin ◽  
Jazuri Abdullah ◽  
Juliana Idrus
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Experimental Work ◽  
Large Scale ◽  
Sediment Supply ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Physical Mechanisms ◽  
Bed Slope ◽  
Bar Formation

A large number of studies both theoretical and experimental have been devoted to understand the physical mechanisms underlying the bar formation. This can be investigated by carrying out an experimental work in an erodible sand bed channel using a large-scale physical river model. The study included the various hydraulic characteristics with steady flow rates and sediment supply. An experimental work consists of four matrices of flow rate and channel width with other variables namely grains size and bed slope were kept constant. Details of bar profile development that generated using Surfer, a software used for 3D elevation plots are included.

scholarly journals The simulation of gas-dynamic characteristics of centrifugal compressors in turbo-expander units

2019 ◽  
Vol 124 ◽  
pp. 01008 ◽  
Author(s):  
A. Rekstin ◽  
V. Semenovskiy ◽  
K. Soldatova ◽  
Y. Galerkin ◽  
K. Sokolov
Keyword(s):  
Dynamic Characteristics ◽  
Rate Coefficient ◽  
Technical Specification ◽  
Design Parameters ◽  
Centrifugal Compressors ◽  
Gas Dynamic ◽  
Flow Rate Coefficient ◽  
Delivery Pressure ◽  
Turbo Expander ◽  
Total Capacity

Prof. Y. Galerkin and his team have developed and completed designs of 19 single-stage centrifugal compressors for turbo-expander packaged units applying Universal Modeling Method for the company “Turbokholod JSC” since 2005. The most powerful compressor is 6500 kW. The highest delivery pressure is 12 MPa. One hundred fifteen turbo-expander packaged units with total capacity 400 000 kW were manufactured, installed and were in operation in December 2018. The gas-dynamic characteristics of compressors comply with technical specification when operated within given range of initial temperatures and initial and final pressures up to 16 combinations for some compressors. The dimensionless characteristics of the compressor stages vary within the range of design parameters: flow rate coefficient 0.0278-0.0697, loading factor 0.43-0.71. The simulation of gas-dynamic characteristics of one of the designed compressors by the newest version of mathematical model is presented as an example, demonstrating the simulation features and effectiveness.

Effects of aeroelasticity on the performance of hypersonic inlet

2017 ◽  
Vol 232 (11) ◽  
pp. 2108-2121 ◽  
Author(s):  
Kun Ye ◽  
Zhengyin Ye ◽  
Qing Zhang ◽  
Zhan Qu
Keyword(s):  
Rate Coefficient ◽  
Pressure Rise ◽  
Dynamics Simulation ◽  
Performance Parameters ◽  
Recovery Coefficient ◽  
Hypersonic Inlet ◽  
Flow Rate Coefficient ◽  
Generalized Displacements ◽  
Computational Structural Dynamics ◽  
Pressure Recovery Coefficient

Effects of the aeroelasticity on the performance of the hypersonic inlet have been investigated numerically in this study. The aeroelasticity has been simulated using the coupled computational fluid dynamics/computational structural dynamics method, which is solved by the in-house code. The unsteady Reynolds-averaged Navier–Stokes equations have been solved in the computational fluid dynamics simulation, and the modal method has been adopted in the computational structural dynamics simulation. Two cases have been utilized to validate the numerical method. Finally, the aeroelasticity has been simulated for inlet plate with different thicknesses. The effects of aeroelasticity on performance parameters and flow structure have been discussed in detail. The results show that the generalized displacements present the “beat” phenomenon in the time domain. The power spectral density of the generalized displacements implies that the aeroelastic instability is mainly caused by the coupling between the fourth- and fifth-order modes. The time-average flow rate coefficient and pressure rise ratio increase relative to the initial value, while the total pressure recovery coefficient decreases. The fluctuation amplitude of the flow rate coefficient is small, while that of the total pressure recovery coefficient and pressure rise ratio are relatively large. Besides, the phases of the three performance parameters are greatly different. Furthermore, the aeroelasticity has significant effect on the shock wave structure especially at the exit of the inlet.

scholarly journals Stator elements optimization of centrifugal compressor intermediate type stage by CFD methods

2020 ◽  
Vol 178 ◽  
pp. 01020 ◽  
Author(s):  
Lyubov Marenina ◽  
Yuri Galerkin ◽  
Alexandr Drozdov
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rate Coefficient ◽  
Optimization Problems ◽  
Flow Path ◽  
Loss Coefficient ◽  
Radius Of Curvature ◽  
Intermediate Type ◽  
Flow Rate Coefficient ◽  
Return Channel

Optimal gas-dynamic design is a complex and time-consuming process. Modern CFD methods help in solving optimization problems and reliably calculating characteristics of stator elements of centrifugal compressor stages. To carry out such calculations, it is necessary to create a parametrized model, which facilitates automation of the process of changing the flow path geometry, rebuilding its dimensions and the computational grid. Using the Direct Optimization program of the ANSYS software package, we have optimized the flow path of the stator elements of a centrifugal compressor intermediate type stage consisting of a vaneless diffuser and a return channel. In this paper, the MOGA (Multi-Objective Genetic Algorithm) optimization method was used. The object of the study was stator elements of one of the model stages designed by the Problem Laboratory of Compressor Engineering, SPbPU. The goal was to achieve the minimum value of the loss coefficient of stator elements when changing 5 geometric parameters: the number of vanes, the inlet vane angle, the height of the vane at the inlet to the return channel vane cascade, the radius of curvature of the leading edge and the thickness of the vane profile. For the best variants based on the results of optimization, the characteristics of the loss coefficient depending on the flow rate coefficient were calculated, their characteristics were compared with the initial variant of the stator elements. The best variant in the design mode has a loss coefficient 4.4% lower than the reference model. With a flow rate coefficient of 1.63 times greater than the calculated one, the optimized variant’s loss coefficient is 33% less.

scholarly journals Hydraulic characteristic of collagen

2016 ◽  
Vol 33 (No. 5) ◽  
pp. 479-485 ◽  
Author(s):  
R. Žitný ◽  
A. Landfeld ◽  
J. Skočilas ◽  
J. Stancl ◽  
V. Flegl ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Limited Range ◽  
Hydraulic Characteristic ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Transient Flows ◽  
Wide Range ◽  
On Line ◽  
Collagenous Material

Hydraulic characteristic of collagen. Czech J. Food Sci., 33: 479–485. The hysteresis of a hydraulic characteristic while pumping an aqueous solution of collagen through a pipe at gradually increasing and decreasing flow rates (hysteresis means that the pressure drop curve during increased flow rate is above the pressure drop during decreasing flow rate) was observed. The problem was initiated by industry and by demand for an on-line recording of rheological properties of collagenous material used for extrusion of collagen casings. The Herschel-Bulkley rheological model was capable to describe rheograms in a wide range of deformation rates; however it was not able to describe and explain the hysteresis. As a possible reason thixotropic properties were identified and the hydraulic characteristic was calculated using a thixotropic generalisation of the Herschel-Bulkley model. The developed 1D numerical model can be applied for on-line modelling of transient flows of incompressible thixotropic food materials (startup flow) and at a limited range of flow rates it is also capable to describe the hysteresis of hydraulic characteristics.

Centrifugal Compressor Stage Design Principles Checking

2015 ◽  
Author(s):  
Y. Galerkin ◽  
A. Drozdov
Keyword(s):  
Optimal Design ◽  
Flow Rate ◽  
Gas Dynamics ◽  
Rate Coefficient ◽  
Computer Programs ◽  
Design Flow ◽  
Flow Coefficient ◽  
Inlet Velocity ◽  
Flow Rate Coefficient ◽  
Performance Curves

Laboratory “Gas dynamics of turbo machines” (LGDTM) has quite effective optimal design computer programs based on theoretic analysis and experimental data. The authors do not share an opinion that 3D impellers are superior in any case. A lot of designed compressors are provided with traditional 2D impellers with cylindrical blades disposed in a radial part of an impeller. The industrial partner tested recently 1:2 scale model of a single stage 32 MWt pipeline compressor. The flow path design is based on the medium specific speed 2D impeller. Good general scheme of the industrial partner, no constrains and profound design optimization have led to maximum efficiency 90% and to excellent performance in a whole. But if a design flow rate coefficient exceeds 0,070 … 0,08 application of 3D impeller is inevitable. Meridian configuration and blade cascade shape of 3D impellers are much more complicated in comparison with 2D impellers. LGDTM has no at its disposal complete information on physical or numerical tests of 3D impeller candidates with different design solutions. Modern trend to apply CFD calculation for investigations to fill the gap seems to be most logical. But the authors’ own experience and published data show that CFD modeling of 3D impeller performance curves is not satisfactory. As a rule calculated performances are shifted to bigger flow rates and work coefficient is 6–9% higher. But the positive moment is that the efficiency at the design flow coefficient is predicted quite accurately. It opens a way to compare stage’s candidates at the design regimes efficiency at the design flow coefficient. The initial design of the stage 3D impeller + vaneless diffuser + return channel with flow rate coefficient 0,105 and loading factor 0,56 is based on general principles of LGDTM: inlet velocity minimization, mean velocity deceleration control, Q-3-D non-viscid velocity diagrams with non-incidence inlet and minimal load at leading edges. CFD calculation has demonstrated necessity to apply a diffuser with tampered initial part, and better shape of the tampered part was defined. The better shape of the crossover was defined by CFD calculations too. The impeller candidates with gas dynamic and geometry principle of blade design, with different degree of flow deceleration, different axial dimension and different exit blade angles were compared. The new 6th version of the optimal design computer programs (Universal modeling was widely presented at the conferences in Japan, Germany, Great Britain, etc.) is tuned on high flow rate stages with 3D impellers. Validation calculations demonstrated good level of performance curves modeling. The program was applied to study series of candidates with different dimensions in meridian plane. As these dimensions influence mean blade load each parameter was studied with different number of blades. Main results are: axial elongation of an impeller does not lead to efficiency grow, optimal leading edge position is at about 25% of meridian distance from an impeller inlet, optimal inlet diameter is 8,5% less that the diameter corresponding to minimal peripheral inlet velocity. The last conclusion is of particular interest and needs additional proof. The comparison of 94 impellers candidates has led to the stage efficiency increase on about 1.5%. The results have verified general principles of design applied in the laboratory “Gas dynamics of turbo machines” and pointed out on some improvements of design principles.

Heat Transfer and Hydraulic Characteristics of Cooling Water in a Flat Plate Heat Sink for High Heat Flux IGBT

2016 ◽  
Author(s):  
Chang-Nian Chen ◽  
Ji-Tian Han ◽  
Wei-Ping Gong ◽  
Tien-Chien Jen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flat Plate ◽  
Heat Sink ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Plate Heat

High heat flux is very dangerous for electronic heat transfer, such as IGBT (Insulated Gate Bipolar Transistor) cooling. In order to explore and master the heat transfer and hydraulic characteristics for IGBT cooling, experiments have been carried out to study the situation mentioned above in a flat plate heat sink, which was designed for high heat flux IGBT cooling. The geometrical parameters of the test section are as follows: outline dimension 229 mm × 124 mm × 30 mm; flow channels of 229 mm × 3 mm × 4 mm in total of 20. The experiments performed at atmospheric pressure and with inlet temperatures of 25–35°C, heat fluxes of 3.5–18.9 kW/m2. The influence of temperatures, heat fluxes on IGBT surface temperature and the cooling effect of the liquid cold plate have been investigated under a range of flow rates of 280–2300 kg/m2s. It was found that the heat transfer enhancement was very obvious using this kind of small sized channel for IGBT cooling, which was tens of times of the effect than air cooling or triple of the effect than that in normal sized channels. And the heat transfer enhancement increases with increasing heat fluxes and flow rates, while it decreases with increasing inlet temperatures. Most of the experimental results show good cooling effect as expected. However, it is dangerous for the cooling system under high heat fluxes when the system starts or stops suddenly, when the Respond Time (RT) is less than 5 seconds to cut off heated power. Also, the cooling performance is bad when the heat fluxes increased greatly, which is considered as abnormal situation in operating. The effect on IGBT surface temperature of heat flux is more obvious when the average Nusselt Number is smaller. For hydraulic characteristics observed, it was found that the flow friction increased with flow rates increasing, but the pressure drops of heated flow channels ahead were slightly larger than those back, especially under large flow rates conditions. That is because the temperatures of flow heated in channels ahead are lower than those back, which causes the fluid viscosity to be higher. At last, this paper suggested a series of method for enhancing heat transfer in flat plate heat sink, and also gave some ways to avoid heat transfer dangerous situations for IGBT cooling, which can provide a basis for thermodynamic and hydraulic calculation of flat plate heat sink design and lectotype.

scholarly journals Flow Characteristics of the Nozzle Blade Cascade in the Mode of the Joint Operation with the Radial Diffuser

2021 ◽  
pp. 5-11
Author(s):  
Alexander Lapuzin ◽  
Valery Subotovich ◽  
Yuriy Yudin ◽  
Svetlana Naumenko ◽  
Ivan Malymon
Keyword(s):  
Reynolds Number ◽  
Flow Rate ◽  
Rate Coefficient ◽  
Measurement Data ◽  
Flow Characteristics ◽  
Flow Coefficient ◽  
Blade Cascade ◽  
Flow Rate Coefficient ◽  
Wide Range ◽  
Nozzle Blade

The obtained research data are given for the nozzle cascade used by a small-size gas turbine of an average fanning in combination with the radial diffuser. Aerodynamic characteristics of the nozzle blade cascade were determined in a wide range of a change in the Reynolds number varying from 4∙105 to 106 and the reduced velocity varying in the range of 0.4 to 1.13. The flow rate coefficient of the nozzle cascade was derived for all modes using the integral methods and the drainages behind the cascade. The kinetic energy loss coefficient and the flow angles were calculated using the measurement data of flow parameters in three control modes that were obtained due to the use of orientable pneumometric probes. When the expansion degree of the convergent –divergent annular duct behind the cascade is equal to 1.43 the flow in the narrow section of this duct is “enlocked” in the mode when the reduced velocity behind the cascade is equal to 1.127. At such velocity the Reynolds number 106 is self-similar for the flow rate coefficient. At lower values of Reynolds number, the decrease of it is accompanied by an intensive decrease in the flow rate coefficient for all the values of the reduced velocity. For the Reynolds number lower than 7∙105 an increase in the velocity results in a decreased flow rate coefficient. When this number exceeds 8∙105 an increase in the velocity results in an increase of the flow coefficient up to the moment when the flow is “enlocked” in the nozzle cascade.

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