Numerical validation and back-pressure effect on internal compression flows of typical supersonic inlet

2015 ◽  
Vol 119 (1215) ◽  
pp. 631-645 ◽  
Author(s):  
F. Ding ◽  
C.-B. Shen ◽  
W. Huang ◽  
J. Liu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Wave Pattern ◽  
Back Pressure ◽  
Freestream Turbulence ◽  
Supersonic Inlet

AbstractA numerical study was conducted to analyse the performance of different turbulence models and different turbulence intensities and turbulence length scales specified for the boundary condition of the inflow to the internal compression flow field of a typical supersonic inlet. The effect of the back-pressure ratio on the properties of the flow field was also investigated. Computational results obtained by the commercial software FLUENT, which is used to solve the full two-dimensional Reynolds-averaged Navier-Stokes equations, were validated through both graphical and quantitative comparisons with previously published experimental data. The two-equation models that were considered in this study are the RNGk-ε, realisablek-ε, standardk-ε, and SSTk-ω turbulence models. The RNGk-ε model had the best performance among the four models and predicted good wall pressure distributions. The best agreement between the predicted results and experimental data was obtained when either the default values of the freestream turbulence intensity and length scale in the FLUENT solver were used, or the empirical formula was used to calculate the two parameters of the freestream turbulence properties. The shock wave pattern varied between the oblique mode and the fully developed normal mode with increasing back-pressure ratio, and the unstart phenomenon occurred when the back-pressure ratio was sufficiently high.

Flow Analysis of a High Flowrate Centrifugal Compressor Stage and Comparison With Test Rig Data

2016 ◽  
Author(s):  
Anton Weber ◽  
Christian Morsbach ◽  
Edmund Kügeler ◽  
Christoph Rube ◽  
Matthias Wedeking
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Test Rig ◽  
Total Pressure Ratio

The flow field inside a single-stage centrifugal compressor characterized by a high flowrate of Φ = 0.15 and a design total pressure ratio of approximately 1.4 is analysed numerically. The stage geometry consists of a radially oriented inlet duct with uniform inflow without swirl, a 90 deg inlet bend in front of the impeller, the shrouded impeller itself followed by a large radial vaneless diffuser, a 180 deg U-turn, a radially oriented turning vane, a subsequent 90 deg bend, and as the last item a long axial exit duct. The impeller blades have large fillets at hub and tip and thick blunt trailing edges. Due to the rotating shroud, a labyrinth seal is placed above the impeller with 5 seal tips. The complete leakage region is also included in the CFD analysis. The blade numbers for the impeller and vane are 15 and 14, respectively. The test rig has recently been built at the Institute of Propulsion and Turbomachinery at RWTH Aachen University (Germany). The first part of the CFD work presented was carried out before the first experimental data were available. Using the k-ω turbulence model of Wilcox (1988), a number of principal steady RANS calculations were performed to investigate the following: Impact of near wall grid resolution and turbulence model wall boundary condition treatment, impact of impeller fillets, and the influence of leakage flow. This part is completed by a comparison of steady RANS simulations with the time-mean results of unsteady RANS analyses of one blade passage. For the calculations presented in the second part, experimental data are available at the inflow and outflow planes. At these planes overall mean values were deduced. Additionally, 3- and 5-hole probe data are available at spanwise traverse planes located at the zenith of the U-turn and in the exit plane. For part two a finer grid with y+ values of approximately unity for all solid walls was used. In addition to the Wilcox k-ω model and the Menter SST k-ω model, two higher level turbulence models — the explicit algebraic Reynolds stress model Hellsten EARSM k-ω and the differential Reynolds stress model SSG/LRR-ω — have been tested and compared with the experiments. The agreement in terms of overall performance (total pressure ratio, isentropic efficiency) is satisfactory for all turbulence models used, but there are some differences: the k-ω model is shown to be the most stable one towards stall. On the other hand, it is shown that details of the flow field in terms of the two spanwise traverses can be better represented by the more advanced turbulence models. All CFD simulations have been performed at 100% shaft speed.

scholarly journals Performance Assessment of Reynolds Stress and Eddy Viscosity Models on a Transitional DCA Compressor Blade

Aerospace ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 102
Author(s):  
Zinon Vlahostergios
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Performance Assessment ◽  
Reynolds Stress ◽  
Eddy Viscosity ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Compressor Blade ◽  
Boundary Layer Transition ◽  
Transitional Flow

In the current work a detailed investigation and a performance assessment of two eddy viscosity and two Reynolds stress turbulence models for modelling the transitional flow on a double circular arc (DCA) compressor blade is presented. The investigation is focused on the comparison of the obtained computational results with available experimental data for a specific DCA compressor blade cascade which can be found in the European Research Community on Flow, Turbulence and Combustion (ERCOFTAC) experimental database. The examined flow field is very challenging for the performance assessment of the turbulence models. The blade inlet angle departs +5° from the compressor blade design conditions resulting in a complex flow field having large regions of boundary layer transition both on the suction and pressure sides of the blade with the presence of an unsteady wake. The presented results include velocity and turbulence intensity distributions along the pressure, the suction sides, and the wake region of the blade. From the comparison with the available experimental data, it is evident that in order to accurately compute such complex velocity and turbulence fields that are met in aero engine components (compressors and turbines), it is obligatory to use more advanced turbulence models with the Unsteady Reynolds Averaged Navier Stokes Equations (URANS) adoption, or other simulation and hybrid methodologies which require unsteady calculations.

scholarly journals Numerical Study of the Internal Flow Field of a Centrifugal Impeller

1994 ◽  
Author(s):  
Mou-jin Zhang ◽  
Chuan-gang Gu ◽  
Yong-miao Miao
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
High Reynolds

The complex three-dimensional flow field in a centrifugal impeller with low speed is studied in this paper. Coupled with high–Reynolds–number k–ε turbulence model, the fully three–dimensional Reynolds averaged Navier–Stokes equations are solved. The Semi–Implicit Method for Pressure–Linked Equations (SIMPLE) algorithm is used. And the non–staggered grid arrangement is also used. The computed results are compared with the available experimental data. The comparison shows good agreement.

scholarly journals Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Fangyuan Lou ◽  
John Charles Fabian ◽  
Nicole Leanne Key
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Pressure Measurements ◽  
High Loss ◽  
Supersonic Inlet ◽  
Mach Numbers ◽  
Inlet Conditions

This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc) from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.

A Numerical Study of the Hydrodynamics of Reversing Flows Around a Cylinder

1994 ◽  
Vol 116 (4) ◽  
pp. 202-208 ◽  
Author(s):  
K. Nakajima ◽  
Y. Kallinderis ◽  
I. Sibetheros ◽  
R. W. Miksad ◽  
K. Lambrakos
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Stokes Equations ◽  
Numerical Study ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Random Behavior ◽  
Marching Scheme

A numerical study of the nonlinear and random behavior of flow-induced forces on offshore structures and experimental verification of the results are presented. The numerical study is based on a finite-element method for the unsteady incompressible Navier-Stokes equations in two dimensions. The momentum equations combined with a pressure correction equation are solved employing fourth-order artificial dissipation with a nonstaggered grid, instead of the more commonly used staggered meshes. The solution is advanced in time with a combined explicit and implicit marching scheme. Emphasis is placed on study of reversing flows around a cylinder. Comparisons with experimental data evaluate accuracy and robustness of the method.

Numerical Study on Electrokinetic Interaction Between a Pair of Cylindrical Colloidal Particles

2009 ◽  
Author(s):  
Dolfred Vijay Fernandes ◽  
Sangmo Kang ◽  
Yong Kweon Suh
Keyword(s):  
Flow Field ◽  
Electric Field ◽  
Colloidal Particles ◽  
Stokes Equations ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Interaction Force ◽  
Surface Element ◽  
Immersed Boundary ◽  
Interaction Forces

Electrophoresis is the motion of dispersed particles relative to a fluid under the influence of an electric field. Presently this phenomenon of electrokinetics is widely used in biotechnology for the separation of proteins, sequencing of polypeptide chains etc. The separation efficiency of these biomolecules is affected by their aggregation. Thus it is important to study the interaction forces between the molecules. In this study we calculate the electrophoretic motion of a pair of colloidal particles under axial electric field. The hydrodynamic and electric double layer (EDL) interaction forces are calculated numerically. The EDL interaction force is calculated from electric field distribution around the particle using Maxwell stress tensor and the hydrodynamic force is calculated from the flow field obtained from the solution of Stokes equations. The continuous forcing approach of immersed boundary method is used to obtain flow field around the moving particles. The EDL distribution around the particles is obtained by solving Poisson-Nernst-Planck (PNP) equations on a hybrid grid system. The EDL interaction force calculated from numerical solution is compared with the one obtained from surface element integration (SEI) method.

scholarly journals Numerical study on the hydrodynamic performance of the semi-spade rudder and propeller

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882310 ◽  
Author(s):  
Xiao Yang ◽  
Yong Yin ◽  
Jing-Jing Lian
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Turbulence Models ◽  
Suction Side ◽  
Hydrodynamic Performance ◽  
Computational Grids ◽  
Hydrodynamic Characteristics ◽  
Thrust Coefficient ◽  
Ship Maneuverability ◽  
Thrust And Torque

The semi-spade rudder and KP458 propeller of the KVLCC2 (KRISO very large crude carrier) model tanker are adopted by ITTC maneuvering technical committee in the comparative study of ship maneuverability. The incompressible viscous flow around semi-spade rudder and KP458 propeller is investigated using Reynolds-averaged Navier–Stokes equations, the computational grids are generated using ICEM software, and finite volume method is employed to discretize the governing equations. Combined with turbulence model, the hydrodynamic performance of semi-spade rudder is analyzed at different rudder angles, and the result provides a reference for the estimation of the hydrodynamic characteristics of semi-spade rudder. The multi-reference framework method is employed to carry out the numerical simulation of the flow field around the propeller. The thrust and torque of propeller under different turbulence models are calculated in the simulation. The thrust coefficient curve, torque coefficient curve, and efficiency curve are present. The pressure distributions of the pressure side and suction side of propeller blades are studied at different advance coefficient. Based on the study of the hydrodynamic performance of the semi-spade rudder and propeller, the propeller–rudder interaction is simulated and analyzed at different advance coefficient.

Effects of Pressure Ratio and Rotational Speed on Leakage Flow and Cavity Pressure in the Staggered Labyrinth Seal

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Xin Yan ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Rotational Speed ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Flow Coefficient ◽  
Leakage Flow ◽  
Cavity Pressure ◽  
Cavity Structure

Effects of pressure ratio and rotational speed on the leakage flow and cavity pressure characteristics of the rotating staggered labyrinth seal were investigated by means of experimental measurements and numerical simulations. The rotating seal test rig with turbine flowmeter and pressure measuring instruments was utilized to investigate the leakage flow of the staggered labyrinth seal at eight pressure ratios and five rotational speeds. The repeatability of the experimental data was demonstrated by three times measurements at different pressure ratios and fixed rotational speed. The three-dimensional Reynolds-averaged Navier–Stokes equations and standard k-ε turbulent model were also applied to study the leakage flow characteristics of the staggered labyrinth seal at the experimental conditions. The validation of the numerical approach was verified through comparison of the experimental data. The detailed flow field in the staggered labyrinth seal was illustrated according to the numerical simulations. The experimental and numerical results show that the leakage flow coefficient increases with increasing pressure ratio at the fixed rotational speed and is more sensitive to the smaller pressure ratio. The influence of rotational speed on the leakage flow coefficient is not obvious in the present rotational speed limitations. The cavity pressure coefficient in the staggered labyrinth seal decreases and is significantly influenced by the cavity structure along the flow direction.

Numerical Study on the Effect of a Volute on Surge Phenomena in a Centrifugal Compressor

2016 ◽  
Author(s):  
S. H. Jeon ◽  
D. H. Hwang ◽  
J. H. Park ◽  
C. H. Kim ◽  
J. H. Baek ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Stokes Equations ◽  
Flow Instability ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Unstable Flow ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Blade Passing Frequency

Numerical investigation of the effect of the volute on stall flow phenomenon is presented by solving three-dimensional Reynolds-averaged compressible Navier-Stokes equations. Two different configurations of a centrifugal compressor were used to compare their performance: One is an original centrifugal compressor which is composed of impeller, splitter, vaned diffuser and a volute and the other is the one without a volute. Steady calculations were performed to predict aerodynamic performance in terms of the pressure ratio, efficiency and mass flow rate. The results show that the operating range of the compressor with a volute is narrower than that of the compressor without a volute. This can be interpreted that flow instability is strongly influenced by the tongue of a volute which is highly asymmetric. Unsteady calculations were also performed with a time-step size of 38μs corresponding to a pitch angle of 5 degrees at the given rotational speed. The flow characteristics for two configurations are analyzed and compared at various instantaneous times showing unsteady dynamic features. Based on the unsteady flow simulation, fast Fourier transform at several discrete points in semi-vaneless space was performed at peak efficiency and near surge point in order to illustrate the unstable flow physics in both configurations. It is found that the blade passing frequency is dominant, indicating that diffuser passages have a periodicity of 40 degrees due to the rotational blades. Besides blade passing frequency, there were several noticeable frequencies which affect the instability of the whole system. Those frequencies in both configurations are compared and analyzed in various aspects.

Computational Analysis of a Inverted Double-Element Airfoil in Ground Effect

2006 ◽  
Vol 128 (6) ◽  
pp. 1172-1180 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Near Field ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Navier Stokes ◽  
Main Element ◽  
Ride Height ◽  
Navier Stokes Equations

The flow around an inverted double-element airfoil in ground effect was studied numerically, by solving the Reynolds averaged Navier-Stokes equations. The predictive capabilities of six turbulence models with regards to the surface pressures, wake flow field, and sectional forces were quantified. The realizable k−ε model was found to offer improved predictions of the surface pressures and wake flow field. A number of ride heights were investigated, covering various force regions. The surface pressures, sectional forces, and wake flow field were all modeled accurately and offered improvements over previous numerical investigations. The sectional forces indicated that the main element generated the majority of the downforce, whereas the flap generated the majority of the drag. The near field and far field wake development was investigated and suggestions concerning reduction of the wake thickness were offered. The main element wake was found to greatly contribute to the overall wake thickness with the contribution increasing as the ride height decreased.

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