An Unsteady Numerical Investigation on the Hysteresis Stall Loop of a Counter-Rotating Compressor

2011 ◽  
Author(s):  
Zhuoqi Wang ◽  
Wei Yuan ◽  
Qiushi Li ◽  
Yajun Lu
Keyword(s):  
Numerical Simulation ◽  
Recovery Process ◽  
Characteristic Line ◽  
Rotor Speed ◽  
Stall Inception ◽  
Rotating Speed ◽  
Flow Phenomena ◽  
Stall Cells ◽  
Unsteady Numerical Simulation ◽  
Good Agreement

For investigating the flow phenomena in the stall process, a full annular unsteady numerical simulation has been carried out on a low speed counter-rotating compressor. The numerical results are in good agreement with experimental results. According to the CFD results, the stall inception was found in the tip region of the front rotor. The rotating speed of stall cells in the front rotor are about 41% of the rotor speed and the direction is the same with the rotor rotating direction. The stall cells occupies about 20% of the blade span away from the casing wall when the compressor is in deep stall. The flow phenomena is well captured which explained why the compressor characteristic line appears as a hysteresis loop in the stall inception-recovery process.

Experimental Investigation on the Stall Inception of a Counter-Rotating Compressor

2012 ◽  
Author(s):  
Zhuoqi Wang ◽  
Wei Yuan ◽  
Qiushi Li ◽  
Yajun Lu
Keyword(s):  
Pressure Sensors ◽  
Leading Edge ◽  
Rotor Speed ◽  
Post Processing ◽  
Dynamic Experiment ◽  
Stall Inception ◽  
Rotating Speed ◽  
Flow Phenomena ◽  
Blade Tip ◽  
Response Pressure

For investigating the flow phenomena in the stall process of a counter-rotating compressor (CRC), static and dynamic experiment have been carried out on a low speed counter-rotating compressor. Seven high response pressure sensors were mounted at the leading edge of rotor 1(R1) and rotor 2(R2) as well as at the outlet of R2 blade tip and root. Wavelet analysis and FFT transform was introduced to the post processing progress. According to the experimental results, the stall inception was found in the tip region of the second rotor. The rotating speed of stall cell in the compressor is about 35% of the rotor speed.

3D Unsteady Computation of Stall Inception in Axial Compressors

2010 ◽  
Author(s):  
Baofeng Tu ◽  
Jun Hu ◽  
Yong Zhao
Keyword(s):  
Numerical Simulation ◽  
Euler Equations ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Computational Domain ◽  
Stall Inception ◽  
Axial Compressors ◽  
Stall Cells ◽  
Unsteady Numerical Simulation ◽  
Aero Engines

Rotating stall is one of the unsteady phenomena in multistage axial compressors that will damage both of performance and service life of aero engines. Stall inception is a dynamic process including appearance of pre-stall disturbance, evolvement of disturbances into stall cells, and development of stall cells. The main purpose in researching stall inception is to reveal the origins of disturbances and stall cells, investigate the effects of aerodynamic design variations on stall inception, and find the effective ways to prevent engines from turning into rotating stall or surge. Numerical simulation is an economic, reliable and rapid tool to study stall inception. As stall inception is three-dimensional and unsteady, numerical simulation should be capable of describing these aspects. In this paper, a three dimensional unsteady computational model based on the three-dimensional unsteady Euler equations and the three dimensional multi actuator-disks model has been developed. The computational domain can be divided into two kinds. One is blade-free regions, which consist of upstream duct, the axial gaps among blade rows, and downstream duct. The other one is blade rows. The flows in blade-free regions considered inviscid, unsteady, and can be resolved using three-dimensional unsteady Euler equations. The blade rows are replaced by multi actuator-disks with different total-to-static characteristics. By added the correlation functions of inlet and outlet flow angles, we can compute the flow field by combining the Euler equations and the multi actuator-disks model. A two-stage low-speed compressor in NUAA has been investigated, and the predicted results indicates that the second stage comes out stall cell first, and the full developed stall cell rotates at about 40.4% rotor speed, which coincides with the experimental data.

About the Numerical Simulation of Rotating Stall Mechanisms in Axial Compressors

2006 ◽  
Author(s):  
N. Gourdain ◽  
S. Burguburu ◽  
G. J. Michon ◽  
N. Ouayahya ◽  
F. Leboeuf ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stall Inception ◽  
Axial Compressors ◽  
Time Frequency ◽  
Flow Phenomena ◽  
Temporal Modes ◽  
Inception Point

This paper deals with the first instability which occurs in compressors, close to the maximum of pressure rise, called rotating stall. A numerical simulation of these flow phenomena is performed and a comparison with experimental data is made. The configuration used for the simulation is an axial single-stage and low speed compressor (compressor CME2, LEMFI). The whole stage is modeled with a full 3D approach and tip clearance is taken into account. The numerical simulation shows that at least two different mechanisms are involved in the stall inception. The first one leads to a rotating stall with 10 cells and the second one leads to a configuration with only 3 cells. Unsteady signals from the computation are analyzed thanks to a time-frequency spectral analysis. An original model is proposed, in order to predict the spatial and the temporal modes which are the results of the interaction between stall cells and the compressor stage. A comparison with measurements shows that the computed stall inception point corresponds to the experimental limit of stability. The performance of the compressor during rotating stall is also well predicted by the simulation.

Effects of Fan Speed on Rotating Stall Inception and Recovery

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Minsuk Choi ◽  
Mehdi Vahdati ◽  
Mehmet Imregun
Keyword(s):  
Aspect Ratio ◽  
Flow Rate ◽  
Reverse Flow ◽  
Recovery Process ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Implicit Time ◽  
Stall Inception ◽  
Stall Cells ◽  
Fan Speed

An implicit, time-accurate 3D compressible Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate rotating stall inception and recovery, the so-called rotating stall hysteresis, in the case of a modern fan geometry. In the first instance, rotating stall was simulated for 70%, 80%, and 90% fan speeds using a whole-annulus fan model with a variable-area nozzle downstream. As the fan speed is increased, the stall cells also increase in size but their number decreases. One large stall cell is predicted to rotate along the annulus at 80% and 90% speeds, while there are three smaller cells at 70% speed. In all cases, the reverse flow is confined to the near-tip region and the rotating stall does not develop into a full-span stall because of the fan blade’s high-aspect ratio. To simulate stall recovery, the nozzle area was increased gradually at 70% and 90% speeds and the flow was seen to recover from rotating stall to reach an unstalled operating condition. The recovery process was found to be affected by the fan speed. At 70% speed, the large disturbances decay first to form almost symmetric stall cells. Thereafter, the stall cells shrink into smaller ones as the mass flow rate increases further. At 90% fan speed, a single stall cell rotates along the annulus, the disappearance of which results in recovery. An attempt has been made to explain the dependence of the stall inception and recovery patterns on the fan speed.

Effects of Fan Speed on Rotating Stall Inception and Recovery

2010 ◽  
Author(s):  
Minsuk Choi ◽  
Mehdi Vahdati ◽  
Mehmet Imregun
Keyword(s):  
Aspect Ratio ◽  
Flow Rate ◽  
High Aspect Ratio ◽  
Reverse Flow ◽  
Recovery Process ◽  
Rotating Stall ◽  
Implicit Time ◽  
Stall Inception ◽  
Stall Cells ◽  
Fan Speed

An implicit, time-accurate 3D compressible RANS solver is used to simulate rotating stall inception and recovery, the so-called rotating stall hysteresis, in a modern fan geometry. In the first instance, rotating stall was simulated for 70%, 80% and 90% fan speeds using a whole-annulus fan model with a variable-area nozzle downstream. As the fan speed is increased, the stall cell also increases in size but the number of stall cells decreases. One large stall cell is predicted to rotate along the annulus at 80% and 90% speeds, while there are three smaller cells at 70% speed. In all cases, the reverse flow is confined to the near-tip region and the rotating stall does not develop into a full-span stall because of the fan blade’s high-aspect ratio. To simulate stall recovery, the nozzle area was increased gradually at 70% and 90% speeds and the flow was seen to recover from rotating stall to reach an unstalled operating condition. The recovery process was found to be affected by the fan speed. At 70% speed, the large disturbances decay first to form almost symmetric stall cells. Thereafter, the stall cells shrink into smaller ones as the mass flow rate decreases further. At 90% fan speed, a single stall cell rotates along the annulus, the disappearance of which results in recovery. An attempt has been made to explain the dependence of the stall inception and recovery patterns on the fan speed.

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

Field Observation and Simulation of Sediment Resuspension in a Shallow Lake

1988 ◽  
Vol 20 (6-7) ◽  
pp. 263-270 ◽  
Author(s):  
K. Otsubo ◽  
K. Muraoka
Keyword(s):  
Numerical Simulation ◽  
Shallow Lake ◽  
Water Wave ◽  
Field Data ◽  
Sediment Resuspension ◽  
Field Research ◽  
Lake Kasumigaura ◽  
Bed Erosion ◽  
Current Water ◽  
Good Agreement

The dispersion and resuspension of sediments in Takahamairi Bay basin of Lake Kasumigaura were studied by means of field research and numerical simulation. The field data on wind direction and velocity, lake current, water wave, and turbidity were shown. Based on these results, we discuss how precipitated sediments were resuspended in this shallow lake. To predict the turbidity and the depth of bed erosion, a simulation model was established for this lake. The calculated turbidity showed good agreement with the field data. According to the simulated results, the turbidity reaches 200 ppm, and the bed is eroded several millimeters deep when the wind velocity exceeds 12 m/s in the lake.

scholarly journals Numerical Simulation of the Aerosol Particle Motion in Granular Filters with Solid and Porous Granules

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 268
Author(s):  
Olga V. Soloveva ◽  
Sergei A. Solovev ◽  
Ruzil R. Yafizov
Keyword(s):  
Numerical Simulation ◽  
Aerosol Particle ◽  
Particle Deposition ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Hydrodynamic Resistance ◽  
Hydrodynamic Properties ◽  
Granular Filters ◽  
Limiting Value ◽  
Good Agreement

In this work, a study was carried out to compare the filtering and hydrodynamic properties of granular filters with solid spherical granules and spherical granules with modifications in the form of micropores. We used the discrete element method (DEM) to construct the geometry of the filters. Models of granular filters with spherical granules with diameters of 3, 4, and 5 mm, and with porosity values of 0.439, 0.466, and 0.477, respectively, were created. The results of the numerical simulation are in good agreement with the experimental data of other authors. We created models of granular filters containing micropores with different porosity values (0.158–0.366) in order to study the micropores’ effect on the aerosol motion. The study showed that micropores contribute to a decrease in hydrodynamic resistance and an increase in particle deposition efficiency. There is also a maximum limiting value of the granule microporosity for a given aerosol particle diameter when a further increase in microporosity leads to a decrease in the deposition efficiency.

Unsteady Numerical Simulation of Shock Systems in Vaneless Counter-Rotating Turbine

2005 ◽  
Author(s):  
Huishe Wang ◽  
Qingjun Zhao ◽  
Xiaolu Zhao ◽  
Jianzhong Xu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Nozzle Design ◽  
Suction Surface ◽  
Rotor Wake ◽  
Wake Interaction ◽  
Unsteady Numerical Simulation ◽  
Almost All

A detailed unsteady numerical simulation has been carried out to investigate the shock systems in the high pressure (HP) turbine rotor and unsteady shock-wake interaction between coupled blade rows in a 1+1/2 counter-rotating turbine (VCRT). For the VCRT HP rotor, due to the convergent-divergent nozzle design, along almost all the span, fishtail shock systems appear after the trailing edge, where the pitch averaged relative Mach number is exceeding the value of 1.4 and up to 1.5 approximately (except the both endwalls). A group of pressure waves create from the suction surface after about 60% axial chord in the VCRT HP rotor, and those waves interact with the inner-extending shock (IES). IES first impinges on the next HP rotor suction surface and its echo wave is strong enough and cannot be neglected, then the echo wave interacts with the HP rotor wake. Strongly influenced by the HP rotor wake and LP rotor, the HP rotor outer-extending shock (OES) varies periodically when moving from one LP rotor leading edge to the next. In VCRT, the relative Mach numbers in front of IES and OES are not equal, and in front of IES, the maximum relative Mach number is more than 2.0, but in front of OES, the maximum relative Mach number is less than 1.9. Moreover, behind IES and OES, the flow is supersonic. Though the shocks are intensified in VCRT, the loss resulted in by the shocks is acceptable, and the HP rotor using convergent-divergent nozzle design can obtain major benefits.

Turbulent dispersion in a non-homogeneous field

1999 ◽  
Vol 392 ◽  
pp. 45-71 ◽  
Author(s):  
ILIAS ILIOPOULOS ◽  
THOMAS J. HANRATTY
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Stochastic Model ◽  
Point Source ◽  
Time Scales ◽  
Langevin Equation ◽  
Turbulent Dispersion ◽  
Homogeneous Field ◽  
Fully Developed Flow ◽  
Good Agreement

Dispersion of fluid particles in non-homogeneous turbulence was studied for fully developed flow in a channel. A point source at a distance of 40 wall units from the wall is considered. Data obtained by carrying out experiments in a direct numerical simulation (DNS) are used to test a stochastic model which utilized a modified Langevin equation. All of the parameters, with the exception of the time scales, are obtained from Eulerian statistics. Good agreement is obtained by making simple assumptions about the spatial variation of the time scales.

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