Lighthill's analogy applied to a automotive turbocharger compressor

2021 ◽  
Vol 263 (6) ◽  
pp. 307-313
Author(s):  
Clemens Freidhager ◽  
Martin Heinisch ◽  
Andreas Renz ◽  
Stefan Schoder ◽  
Manfred Kaltenbacher
Keyword(s):  
High Resolution ◽  
Fundamental Importance ◽  
Outlet Section ◽  
Source Terms ◽  
Test Rig ◽  
Turbulent Structures ◽  
Cfd Simulations ◽  
Interpolation Algorithms ◽  
Simulation Results ◽  
Pressure Propagation

Computing transient CFD simulations of turbocharger compressors is computationally very demanding. It is of fundamental importance to resolve turbulent structures at the location of their generation and to establish a fine enough grid to allow propagation of the resolved structures. This results in high-resolution grids, existing of more than 20 million cells. Applying Lighthill's analogy, it is possible to only resolve turbulent structures at their location of generation and compute the pressure propagation by using an additional, not that demanding, acoustic grid. This allows using coarser CFD grids in the inlet and outlet section. For transferring Lighthill's source terms from the CFD to the acoustic grid, advanced interpolation algorithms are used. The simulation results are validated by measurements of a cold gas test rig are considered.

CFD Assessment of Rotordynamic Coefficients in Labyrinth Seals

2014 ◽  
Author(s):  
Sai S. Sreedharan ◽  
Giuseppe Vannini ◽  
Hiteshkumar Mistry
Keyword(s):  
High Speed ◽  
Test Results ◽  
Active Magnetic Bearings ◽  
Test Rig ◽  
Labyrinth Seals ◽  
Cfd Simulations ◽  
Flow Solver ◽  
Rotordynamic Coefficients ◽  
Pressure Test ◽  
Dynamic Seal

Seals used in high speed centrifugal compressors are prone to generate rotordynamic (RD) instabilities. To further understand their influence, a CFD based approach is developed. The objective of the current study is to numerically investigate and characterize the RD coefficients, representative of the dynamic seal forces. Experiments were carried out at high pressure test rig (up to 200 bar seal inlet pressure) which runs at 10000 RPM and has a high pre-swirl (about 0.9) along the same direction of rotor rotation. The rotor shaft in the experiment was instrumented with active magnetic bearings (AMBs) to linearly excite the rotor at three different frequencies: 28 Hz, 70 Hz and 126 Hz. Each frequency is characterized by amplitude of vibration and a phase. CFD simulations were carried out using commercial flow solver, using similar boundary conditions as that of experiments. The paper describes details of CFD model and its comparison against experiments. Numerical results show reasonable agreement of RD coefficients with test results. This job has to be considered as a first approach to CFD methodology applied to annular seals for the authors.

On the Influence of a Hubside Exducer Cavity and Bleed Air in a Close-Coupled Centrifugal Compressor Stage

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Peter Kaluza ◽  
Christian Landgraf ◽  
Philipp Schwarz ◽  
Peter Jeschke ◽  
Caitlin Smythe
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Field ◽  
State Of The Art ◽  
Test Rig ◽  
Cfd Simulations ◽  
Trailing Edge ◽  
Loss Mechanism ◽  
Aero Engine ◽  
Computational Fluid Dynamics Cfd ◽  
Stage Efficiency

In aero-engine applications, centrifugal compressors are often close-coupled with their respective diffusers to increase efficiency at the expense of a reduced operating range. The aim of this paper is to show that state-of-the art steady-state computational fluid dynamics (CFD) simulations can model a hubside cavity between an impeller and a close-coupled diffuser and to enhance the understanding of how the cavity affects performance. The investigated cavity is located at the impeller trailing edge, and bleed air is extracted through it. Due to geometrical limitations, the mixing plane is located in the cavity region. Therefore, the previous analyses used only a cut (“simple”) model of the cavity. With the new, “full” cavity model, the region inside the cavity right after the impeller trailing edge is not neglected anymore. The numerical setup is validated using the experimental data gathered on a state-of-the art centrifugal compressor test-rig. For the total pressure field in front of the diffuser throat, a clear improvement is achieved. The results presented reveal a drop in stage efficiency by 0.5%-points caused by a new loss mechanism at the impeller trailing edge. On the hubside, the fundamentally different interaction of the cavity with the coreflow increases the losses in the downstream components resulting in the mentioned stage efficiency drop. Finally, varying bleed air extraction is investigated with both cavity models. Only the full cavity (FC) model captures the changes measured in the experiment.

scholarly journals Predicting ocean waves along the US east coast during energetic winter storms: sensitivity to whitecapping parameterizations

Ocean Science ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 691-715 ◽  
Author(s):  
Mohammad Nabi Allahdadi ◽  
Ruoying He ◽  
Vincent S. Neary
Keyword(s):  
East Coast ◽  
Ocean Waves ◽  
Source Terms ◽  
Frequency Spectra ◽  
Winter Storms ◽  
Wave Parameters ◽  
The Us ◽  
Wind Input ◽  
Simulation Results ◽  
Us East Coast

Abstract. The performance of two methods for quantifying whitecapping dissipation incorporated in the Simulating Waves Nearshore (SWAN) wave model is evaluated for waves generated along and off the US east coast under energetic winter storms with a predominantly westerly wind. Parameterizing the whitecapping effect can be done using the Komen-type schemes, which are based on mean spectral parameters, or the saturation-based (SB) approach of van der Westhuysen (2007), which is based on local wave parameters and the saturation level concept of the wave spectrum (we use “Komen” and “Westhuysen” to denote these two approaches). Observations of wave parameters and frequency spectra at four National Data Buoy Center (NDBC) buoys are used to evaluate simulation results. Model–data comparisons show that when using the default parameters in SWAN, both Komen and Westhuysen methods underestimate wave height. Simulations of mean wave period using the Komen method agree with observations, but those using the Westhuysen method are substantially lower. Examination of source terms shows that the Westhuysen method underestimates the total energy transferred into the wave action equations, especially in the lower frequency bands that contain higher spectral energy. Several causes for this underestimation are identified. The primary reason is the difference between the wave growth conditions along the east coast during winter storms and the conditions used for the original whitecapping formula calibration. In addition, some deficiencies in simulation results are caused along the coast by the “slanting fetch” effect that adds low-frequency components to the 2-D wave spectra. These components cannot be simulated partly or entirely by available source terms (wind input, whitecapping, and quadruplet) in models and their interaction. Further, the effect of boundary layer instability that is not considered in the Komen and Westhuysen whitecapping wind input formulas may cause additional underestimation.

Computer Simulation of a Test Rig to Model Sloshing in Spin-Stabilized Satellites

1992 ◽  
Vol 114 (4) ◽  
pp. 689-698 ◽  
Author(s):  
D. R. Flugrad ◽  
L. A. Obermaier
Keyword(s):  
Model Simulation ◽  
Test Rig ◽  
Dynamic Motion ◽  
Experimental Project ◽  
Rotating Structure ◽  
Simulation Results ◽  
Parameter Values ◽  
The Mathematical Model ◽  
Two Degree Of Freedom ◽  
Good Agreement

Certain communications satellites carry liquid stores on board for station tending and attitude adjustment. However, sloshing of the liquid can cause an undesirable nutational motion of the spin-stabilized vehicle. In previous work a test rig was designed, built and instrumented to study the interaction between the rotating structure and liquid. To augment that experimental project, a computer model of the test rig has been developed to simulate the dynamic motion of the system for various parameter values. The sloshing liquid was replaced by a two degree-of-freedom pendulum in the mathematical model. Simulation results were compared with those from a general multibody dynamics program and with experimental measurements of the test rig motion to demonstrate the mathematical model’s validity. Good agreement was achieved in both instances.

Complex Angle Measuring Method of Passive-Radar-Seeker

2011 ◽  
Vol 55-57 ◽  
pp. 272-275 ◽  
Author(s):  
Chun Na Zhao ◽  
Chang Di Shi ◽  
Yu Zhao ◽  
Yi Liu
Keyword(s):  
High Resolution ◽  
Measuring Method ◽  
Spatial Spectrum ◽  
Passive Radar ◽  
Spectrum Estimation ◽  
Angle Measuring ◽  
Simulation Results ◽  
Spatial Spectrum Estimation

To overcome the shortcomings of the traditional passive-radar-seeker(PRS) for anti-decoy, a complex angle measuring method is proposed in this letter. The complex angle measuring method consists of monopulse angle and spatial spectrum estimation, two angle-measuring units. PRS can get the angle high-resolution features through the complex angle measuring method. So it is possible that PRS confronts decoy. Finally, the simulation results verify the feasibility and anti-decoy capacity of the complex angle-measuring method.

Joints flexibility effect on the dynamic performance of robots

Robotica ◽  
2014 ◽  
Vol 33 (7) ◽  
pp. 1424-1445 ◽  
Author(s):  
Mohamed H. Zaher ◽  
Said M. Megahed
Keyword(s):  
Dynamic Performance ◽  
Robot Arm ◽  
Test Rig ◽  
Final Model ◽  
Trajectory Error ◽  
The Third ◽  
Inertial Parameters ◽  
Joint Damping ◽  
Flexibility Effect ◽  
Simulation Results

SUMMARYThis paper studies the effect of joint flexibility on the dynamic performance of a serial spatial robot arm of rigid links. Three models are developed in this paper. The first and the third models are developed using the multibody dynamics approach, while the second using the classical robotics approach. A numerical algorithm and an experimental test-rig are developed to test the final model. The links' inertial parameters are estimated numerically. Empirical formulae with assumption models are used to estimate the flexibility coefficients. The simulation results show that the joint damping is a major source of inaccuracies, causing trajectory error without a proper feedback controller.

High-resolution x-ray topography of dislocations in 4H-SiC epilayers

2007 ◽  
Vol 22 (4) ◽  
pp. 845-849 ◽  
Author(s):  
Isaho Kamata ◽  
Hidekazu Tsuchida ◽  
William M. Vetter ◽  
Michael Dudley
Keyword(s):  
Computer Simulation ◽  
High Resolution ◽  
Edge Dislocation ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Topographic Features ◽  
Different Shapes ◽  
Vector Direction ◽  
Simulation Results

Synchrotron x-ray topography with a high-resolution setup using 1128 reflection was carried out on 4H-SiC epilayers. Four different shapes of threading-edge dislocation according to Burgers vector direction were observed. The four types of threading-edge dislocation images were calculated by computer simulation, and the experimental results correlated well with the simulation results. The detailed topographic features generated by plural screw dislocations and basal plane dislocations were also investigated.

Detailed Study of an Efficient Small Diameter Automotive Engine Cooling Fan System

2003 ◽  
Author(s):  
S. Moreau ◽  
F. Bakir
Keyword(s):  
Small Diameter ◽  
Rapid Prototype ◽  
Efficiency Improvement ◽  
Test Rig ◽  
Cfd Simulations ◽  
Automotive Engine ◽  
Engine Cooling ◽  
Cooling Fan ◽  
Radial Equilibrium

This paper deals with stator efficiency improvement meant for automotive engine cooling fan systems. A new rapid prototype of a long stator designed for a small diameter Valeo rotor (320 mm) has been manufactured and tested on a recently designed Valeo-LEMFI test rig. The following points are presented: • Overall performances of the 320 mm rotor alone. • Overall performances of the 320 mm rotor combined with the new long stator vanes: this study confirms the gain of efficiency foreseen previously with the simplified radial equilibrium code VENTAX. • Steady velocities measured 41 mm downstream of the stage configuration: These measurements obtained by using a 5-hole probe show high deflection carried out by the stators with long chord lengths. Comparisons with preliminary CFD simulations are also shown for both the overall performances and the local velocities.

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