scholarly journals Design Method for Channel Diffusers of Centrifugal Compressors

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Mykola Kalinkevych ◽  
Andriy Skoryk
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Inverse Problem ◽  
High Pressure ◽  
Gas Dynamics ◽  
Design Method ◽  
Compressor Stage ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Gas Dynamic

The design method for channel diffusers of centrifugal compressors, which is based on the solving of the inverse problem of gas dynamics, is presented in the paper. The concept of the design is to provide high pressure recovery of the diffuser by assuming the preseparation condition of the boundary layer along one of the channel surfaces. The channel diffuser was designed with the use of developed method to replace the vaned diffuser of the centrifugal compressor model stage. The numerical simulation of the diffusers was implemented by means of CFD software. Obtained gas dynamic characteristics of the designed diffuser were compared to the base vaned diffuser of the compressor stage.

Pressure Recovery in Low Solidity Vaned Diffusers for Centrifugal Compressors

1997 ◽  
Author(s):  
Naresh K. Amineni ◽  
Abraham Engeda
Keyword(s):  
Comparative Study ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Performance Parameters ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Direct Bearing ◽  
Pressure Recovery Phenomenon

In the present investigation four low solidity vaned diffusers were experimentally tested downstream of the same impeller in an attempt to study the effect of solidity and vane number on the performance of the stage. In addition to these low solidity vaned diffusers, one vaneless and a conventional vaned diffuser were also tested for comparative study of the pressure recovery phenomenon in each of the three types of diffusers. It was found that the vane number and the solidity of the diffuser had direct bearing on the performance parameters of the compressor stage. The results also showed that the pressure recovery characteristics of the low solidity vaned diffusers was simillar to the conventional vaned diffuser.

Aerodynamic Investigation on a 3D-Vaned Diffuser Applied on a High Flow 3D Impeller

2012 ◽  
Author(s):  
H. Strohmeyer ◽  
A. Hildebrandt
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
High Flow ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
High Incidence ◽  
High Pressure Stage ◽  
Stage Efficiency ◽  
Ratio Reduction ◽  
Aerodynamic Investigation

This paper discusses the effect of a diffuser ratio reduction from r4/r2 = 1.55 to r4/r2 = 1.35 of a centrifugal compressor stage and an approach to retain the efficiency by applying a vaned diffuser. Initially, the diffuser ratio of a high flow, high pressure stage is decreased. Following, the stage having the smallest diffuser ratio is used to investigate the performance of a vaned diffuser, whose trailing edge is shifted into the U-turn. The discussion shows a possible improvement by the diffuser vane enlargement. The total stage efficiency of the diffuser ratio of r4/r2 = 1.55 can be retained as long as the separation due to high incidence of the vaned diffuser is low.

scholarly journals Active Flow Control in a Radial Vaned Diffuser for Surge Margin Improvement: A Multislot Suction Strategy

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Aurélien Marsan ◽  
Isabelle Trébinjac ◽  
Stéphane Moreau ◽  
Sylvain Coste
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Control Technique ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Boundary Layer Suction ◽  
Surge Margin ◽  
Active Flow

This work is the final step of a research project that aims at evaluating the possibility of delaying the surge of a centrifugal compressor stage using a boundary-layer suction technique. It is based on Reynolds-Averaged Navier-Stokes numerical simulations. Boundary-layer suction is applied within the radial vaned diffuser. Previous work has shown the necessity to take into account the unsteady behavior of the flow when designing the active flow control technique. In this paper, a multislot strategy is designed according to the characteristics of the unsteady pressure field. Its implementation results in a significant increase of the stable operating range predicted by the unsteady RANS numerical model. A hub-corner separation still exists further downstream in the diffuser passage but does not compromise the stability of the compressor stage.

scholarly journals MODELING OF GAS-DYNAMIC PROCESSES IN THE ELEMENTS OF IMPULSE EJECTOR

2021 ◽  
pp. 66-72
Author(s):  
G. O. Voropaiev ◽  
Ia. V. Zagumennyi ◽  
N. V. Rozumnyuk
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Flow Rate ◽  
Gas Flow ◽  
Dynamic Processes ◽  
Stable Operation ◽  
Operating Pressure ◽  
Gas Generator ◽  
Gas Dynamic ◽  
Ejector Nozzle

The paper presents the numerical results on gas-dynamic processes in various elements of the impulse ejector, including pre-chamber, supersonic nozzle and mixing chamber, to determine optimal geometric parameters providing the given flow rate characteristics. At an extra-high pressure of the ejecting gas (>100 bar) it is impossible to create a nozzle design with continuously changing cross-sectional area and limited nozzle length. So, it is necessary to place a pre-chamber between the gas generator and the ejector nozzle for throttling full gas pressure. In order to optimize the pre-chamber parameters in the ejector with discrete holes of the gas generator and the operating pressure in the range of 400÷1000 bar, a series of calculations were performed to determine the pre-chamber parameters, ensuring stable operation of the supersonic annular nozzle at the high pressure of 35÷45 bar and the flow rate of 0.5÷0.6 kg/s. 3D numerical simulation of the gas flow into the pre-chamber through the gas generator holes shows the degree of the flow pattern non-uniformity in the pre-chamber at the ejector nozzle inlet is quite low. This justifies the numerical simulation of gas flow in the ejector in axisymmetric formulation and allows restricting the number of the gas generator holes without inducing significant non-uniformity in the azimuthal direction.

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

2019 ◽  
Vol 16 (33) ◽  
pp. 728-735
Author(s):  
P. V. NIKITIN ◽  
L. N. RABINSKIY ◽  
O. V. TUSHAVINA
Keyword(s):  
Boundary Layer ◽  
Heat Exchange ◽  
Gas Dynamics ◽  
High Speed ◽  
Gas Flow ◽  
Classical Model ◽  
Particle Accelerator ◽  
Experimental Investigations ◽  
Axially Symmetric ◽  
Gas Dynamic

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%.

scholarly journals Numerical simulation of gas dynamic and physical-chemical processes in hypersonic flows past bodies

2017 ◽  
pp. 387-405
Author(s):  
К.Н. Волков ◽  
В.Н. Емельянов ◽  
А.Г. Карпенко
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Finite Difference ◽  
Gas Dynamics ◽  
Hypersonic Flows ◽  
Chemical Processes ◽  
Difference Schemes ◽  
Finite Difference Schemes ◽  
Gas Dynamic ◽  
Physical Chemical

Рассматриваются вопросы, связанные с численным моделированием газодинамических и физико-химических процессов, сопровождающих гиперзвуковое обтекание тел различной формы. Математическая модель включает в себя уравнения газовой динамики, записанные для реального газа, и уравнения химической кинетики, описывающие равновесные процессы в высокотемпературном воздухе. Для дискретизации основных расчетных соотношений применяется метод конечных объемов и различные разностные схемы для дискретизации конвективных потоков. Возможности разработанной вычислительной процедуры показываются на примере решения ряда задач физико-химической газовой динамики. Расчеты проводятся с использованием графических процессоров общего назначения. Обсуждается время счета, достигнутое при использовании различных разностных схем и подходов к описанию свойств высокотемпературного воздуха. Numerical simulation of gas dynamic and physical-chemical processes in hypersonic flows past bodies of various shapes is considered. The mathematical model includes the gas dynamics equations of real gases and the equations of chemical kinetics describing equilibrium processes in high-temperature air. The finite volume method and various finite difference schemes for the discretization of convective fluxes are used to discretize the governing equations. The capabilities of the numerical procedure are demonstrated by the solution of a number of problems in physical-chemical gas dynamics. The calculations are performed using general-purpose graphics processor units. The computational time achieved with the use of various finite difference schemes and the approaches to describe the properties of high-temperature air are discussed.

Application of Low Solidity Vaned Diffusers to Prevent Rotating Stall in Centrifugal Compressors: Experimental Investigation

2003 ◽  
Author(s):  
A. Cellai ◽  
M. De Lucia ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Stall Inception ◽  
And Performance

Rotating stall is a key problem in centrifugal compressors especially for high-pressure applications. Among the several solutions proposed to prevent this problem, low solidity vaned diffusers (LSDs) have been successfully applied. The aim of this research is to find an optimized LSD configuration in terms of stall inception and performance for the tested compressor. The influence of the vane leading and trailing edge radii, maintaining the same solidity and null deflection were investigated. The geometrical parameters of tested configurations were methodically chosen in order to achieve a design of experiment (DOE) analysis. In view of the above, a series of tests on five low solidity vaned diffuser configurations were carried out. Tests allowed determination of 2 different LSDs that showed the best behavior in terms of working range and performance. These LSDs were then compared with the standard and the reduced-width vaneless diffuser to better understand the best solution to the stall problem.

scholarly journals Turbine Disc-Rim Cooling Design Criteria for Modern Two Stage High Pressure Turbine Aero-Engines

1998 ◽  
Author(s):  
Alexander V. Mirzamoghadam
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Cover Plate ◽  
Design Criteria ◽  
Compressor Stage ◽  
Two Stage ◽  
Second Stage ◽  
Cavity Boundary ◽  
Aero Engines ◽  
Cooling Air

Modern aero-engines with two stage high pressure turbines (HPT) are attractive because they offer higher turbine polytropic efficiencies compared to the single stage. When considering the complexity associated with the secondary cooling airflow system, however, the two stage turbine is more vulnerable to excess air performance losses and requires more effort to optimize. This paper addresses the established design criteria with an emphasis on cooling air supply to the second stage turbine blades. The available cooling air is compressor delivery air fed to the front face of the rim via the first turbine stage, and lower pressure air from an earlier compressor stage is fed internally to the rear cavity. A comparison is made of the effectiveness of disc-rim cooling achieved with alternate forward and rear air feed systems to the rotor blades based on aerothermal analytical methods. Both front and rear cover-plate as well as disc feed holes are considered, and the applicable heat transfer correlation along with cavity boundary layer/mixing temperature assumptions are described. The 2-D axisymmetric finite element transient thermal model, for each design case, has been run with a square speed cycle and in this study, the aerothermal behavior at steady state maximum take-off condition is compared. Results indicate that low pressure compressor air in a cover-plate is thermally more effective than feed holes on the front or rear side of the disc, if pre-swirled compressor exit air from the first stage seals the second stage disc-rim. This is also valid if cavity boundary layer air from an earlier compressor stage sealing the rim (on either side) reaches a temperature as high as the area-weighted-mean (AWM) rim temperature due to contamination by hot gas ingestion. Although the front system offers a better overall cooling effectiveness, in comparing the front and rear feed hole concepts using cooling air from a compressor mid-stage, the rear feed hole is more effective in reducing the AWM temperature in the rotor bucket-groove, as well as the maximum rim temperatures of the second stage disc.

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