Three-Dimensional Vaneless Diffuser Rotating Stall Numerical Study

2018 ◽  
Author(s):  
Filip Grapow ◽  
Grzegorz Liśkiewicz
Keyword(s):  
Mass Flow ◽  
High Efficiency ◽  
Numerical Study ◽  
Complex Structure ◽  
Sudden Change ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Frequency Change ◽  
Vaneless Diffuser ◽  
Growth Pressure

Abstract Centrifugal compressor efficiency is the key to increasing incomes from its operation. There are several flow instabilities which can negatively affect a compressor, one of them being the rotating stall, as it decreases efficiency and mass flow while it can also lead to a surge. Among others, this can occur in the vaneless diffuser. A thorough understanding of this phenomenon and the ability to model its behaviour can lead to a robust protection system assuring high efficiency even at lower mass flow rates. In this paper, the simulated flow was viscous and compressible. Much attention was devoted to providing boundary conditions that would not affect flow conditions at the diffuser outlet. The transient simulation was conducted in order to observe sequential stages of the VDRS onset and growth. Pressure signals from different points in the diffuser have been analysed with the CWT method in the purpose of detecting oscillations frequency change in time. Results have shown that the complex structure and time evolution of the VDRS indeed require the application of three-dimensional methods. As the mass flowrate was continuously decreased a sudden change in number of the rotating stall cells was observed together with an appearance of new strong peak of the pressure oscillation.

scholarly journals Flow-Induced Vibration on the Control Valve with a Different Concave Plug Shape Using FSI Simulation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Akram Zeid ◽  
Mohamed Shouman
Keyword(s):  
High Efficiency ◽  
Complex Structure ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
Control Valve ◽  
Low Noise ◽  
Flow Induced Vibration ◽  
Nonlinear Characteristics ◽  
Flow Phenomena

Control valves have always been recognised as being among the most crucial control equipment, commonly utilised in versatile engineering applications. Hence, the need has arisen to identify the flow characteristics inside the valve, together with the incurred vibration induced as a result of the flow passing through the valve. Thanks to the tangible and fast progress made in the field of the flow simulation and numerical techniques, it has become possible to better observe the behavior of the flow passing inside a valve with view to examining its performance. Hence, the paper at hand is mainly concerned with introducing the modeling and simulation of a control valve. On the contrary, the flow system in a control valve is marked by a complex structure and nonlinear characteristics. The reasons for those qualities could be attributed to its construction as well as the fluid flow phenomena associated with it. It is especially for the sake of investigating and observing the flow characteristics, pertaining to a control valve equipped with different concave plug shapes and different openings, that the three-dimensional FSI simulation is conducted. In addition, it would be possible to make use of the obtained results relating to the three-dimensional analysis to achieve low noise and high efficiency improvement. Furthermore, all results will be validated on experimental grounds.

scholarly journals The Effects of Diffuser Geometry on Rotating Stall Behavior

1988 ◽  
Author(s):  
M. V. Otugen ◽  
R. M. C. So ◽  
B. C. Hwang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Critical Mass ◽  
Rotating Stall ◽  
Radius Ratio ◽  
Impeller Speed ◽  
Vaneless Diffuser ◽  
Room Condition ◽  
Inlet Opening

Experiments were carried out in a model vaneless diffuser rig to investigate the rotating stall phenomenon and its relation to diffuser geometry. The experimental rig consisted of an actual impeller which was used to deliver the flow to the vaneless diffuser. Mass flow rate through the system could be adjusted by varying the rotational speed of the impeller at a fixed inlet opening or by changing the inlet opening at a fixed impeller speed. The flow exited to room condition. As such, the rig was designed to investigate the fluid mechanics of vaneless diffuser rotating stall only. Attention was focused on the effects of diffuser width and radius on rotating stall. Three diffuser widths and three outlet radii were examined. The width-to-inlet radius ratio varied between 0.09 and 0.142 while the outlet-to-inlet radius ratio varied between 1.5 and 2. Results showed that the critical mass flow rate for the onset of rotating stall decreases with decreasing diffuser width. The critical mass flow rate is affected also by the diffuser radius ratio; larger radius ratios resulted in smaller critical mass flow rates. The ratio of the speed of rotation of the stall cell to impeller speed is found to decrease with increasing number of stall cells. This relative speed also decreases with increasing diffuser radius ratio, but it is largely independent of the diffuser width.

Rotating Stall in a Radial Vaneless Diffuser

1964 ◽  
Vol 86 (4) ◽  
pp. 750-758 ◽  
Author(s):  
W. Jansen
Keyword(s):  
Velocity Distribution ◽  
Wave Speed ◽  
Free Stream ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Vaneless Diffuser ◽  
Dimensional Boundary ◽  
Side Walls ◽  
The Waves ◽  
Total Velocity

This paper is concerned with the theoretical and experimental aspects of unsteady flow in a radial vaneless diffuser. Specifically, the appearance of self-excited oscillations of large amplitude is investigated in great detail. The waves appear when the angle between the tangential and total velocity becomes very small. The predicted wave speed and perturbed velocity distribution versus radius agree quite well with the experimentally obtained values, however, an undeterminable constant appears in the equation which describes the disturbed velocity distribution. A stability criterion indicates that such pulsating flow can occur if and only if there is a region of radially inward flow. The hypothesis is proposed that the waves are a result of the interaction of the three-dimensional boundary layer near the side walls and the free stream. Unsteady flows of this type can be linked to unstable centrifugal pump, blower, or compressor operation.

Investigation of the Surge Phenomena in a Centrifugal Compressor Using Large Eddy Simulation

2013 ◽  
Author(s):  
Bernhard Semlitsch ◽  
V. Jyothishkumar ◽  
Mihai Mihaescu ◽  
Laszlo Fuchs ◽  
Ephraim J. Gutmark
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Operating Regime ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Structures ◽  
Compressor Wheel ◽  
Large Eddy

The flow through a ported shroud compressor of an automobile turbocharger is simulated using Large Eddy Simulations. Generally, the compressor is subjected to work within certain range of the mass-flow conditions. Reduction of the operation mass-flow below a certain minimum limit, leads to breakdown of the complete compressor operability. Flow reversal occurs in the compressor wheel, which results in amplification of velocity and pressure fluctuations. Consequentially, large vibratory stresses are induced into the blades under off-design condition and thereby affect the blade life duration detrimentally. The aim of this study is to understand the generation of flow-structures during extreme operable conditions (surge condition) in a centrifugal compressor. The investigation of the appearing flow-structures with the surge phenomenon is essential to explore new methods that improve the stability or the flow-operating regime of the compressor. The complete 360° compressor geometry is utilized in the computational simulations. Further, the transient sliding mesh technique is applied to account for an accurate prediction of the mesh motion and thus, the geometrical interaction between the impeller and the stationary diffuser. The numerical results are compared with available experimental measurements obtained under the same operating conditions (design and near-surge condition). The rotating stall instability is predicted using FFT data analysis. Furthermore, the numerical study captures the low frequency peak characterizing the global instability of the surge condition.

Passive Control of Rotating Stall in Vaneless Diffuser With Radial Grooves: Detailed Numerical Study

2009 ◽  
Author(s):  
Chuang Gao ◽  
Chuangang Gu ◽  
Tong Wang ◽  
Bo Yang
Keyword(s):  
Passive Control ◽  
Numerical Study ◽  
Design Procedure ◽  
Flow Distribution ◽  
Rotating Stall ◽  
Field Variation ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Diffuser Flow ◽  
Computational Fluid Dynamics Cfd

According to experiments described in the literature, radial grooves in vaneless diffuser walls are simple and powerful devices for suppressing rotating stall. To understand the mechanism behind the grooves and find some guidelines for diffuser designers, a detailed numerical study based on Computational Fluid Dynamics (CFD) was carried out. Not only the flow field variation caused by the grooves but also a simple model graphing the underlying nature was established. Also, the classic boundary layer integral method widely used in practical design procedure was adopted to calculate the diffuser flow distribution to verify the model. The CFD analysis indicated that the effectiveness of the grooves increases the flow angle thus delaying the diffuser wall flow reversals. The recommended placement of the grooves was in the region with reversed flow. Such locally fixed groove could effectively delay the stall without too much pressure loss. Also, a combined variable, representing the overall geometry of grooves was established and verified. The detailed study given in this paper gives guidelines for using grooves as a stall delay method.

A numerical study on the effects of design parameters on the acoustics noise of a high efficiency propeller

2018 ◽  
Vol 91 (1) ◽  
pp. 30-37 ◽  
Author(s):  
Yunpeng Ma ◽  
Na Guo
Keyword(s):  
Noise Reduction ◽  
High Efficiency ◽  
Numerical Study ◽  
Three Dimensional ◽  
Aerodynamic Noise ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Content Type ◽  
Simulation Based ◽  
S Model

PurposeA numerical study on the aerodynamic noise generation of a high efficiency propeller is carried out.Design/methodology/approachThree-dimensional numerical simulation based on Reynolds averaged N-S model is performed to obtain the aerodynamic performance of the propeller. Then, the result of the aerodynamic analysis is given as input of the acoustic calculation. The sound is calculated using the Farassat 1A which was derived from Ffowcs Williams–Hawkings equation and is compared with the measurements.FindingsMoreover, the fan is modified for noise reduction by changing its geometrical parameters such as span, chord length and torsion angle.Originality/valueThe variation trend of aerodynamic and acoustic are compared and discussed for different modification tasks. Some meaningful conclusions are drawn on the noise reduction of propeller.

Numerical Study on Three-Dimensional Wall Effects of Flat Micro Nozzle

2011 ◽  
Vol 339 ◽  
pp. 276-282
Author(s):  
Jun Jie Tong ◽  
Ji Wen Cen ◽  
Jin Liang Xu
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Two Dimensional ◽  
Wall Effects ◽  
Micro Nozzle

The FLUENT6.1 software is applied to simulate the supersonic flow in micro convergent-divergent nozzle which is fabricated from flat silicon wafers. The simulation is complemented by parallel computing steady 2-D and 3-D Navier-stokes equations to study the three-dimensional wall effects on temperature and velocity inside the micro nozzle. Also the performances of fluent mass coefficients and thrust force efficiencies are studied. It is observed by the study that three-dimensional wall effects are not negligible in flat micro nozzle. The velocity of fluid in three-dimensional nozzle is less than the corresponding velocity of fluid in two-dimensional nozzle significantly, while the temperature of fluid in three-dimensional nozzle is much higher than the corresponding temperature of fluid in two-dimensional nozzle. The mass flow rate and thrust at the exit of 2-D nozzle are greater than the corresponding mass flow rate and thrust at the exit of three-dimensional. With the throat Renaults being increased, the corresponding differences between two-dimensional numerical results and three-dimensional numerical results decreased accordingly. Two-dimensional numerical results can not correctly predict the actual mass flow rate and thrust at the exit of micro nozzle.

Optimization of Valve Block Shape Using CFD

2012 ◽  
Vol 190-191 ◽  
pp. 133-138 ◽  
Author(s):  
Qin Yang ◽  
Xian Zhou Wang ◽  
Ming Yue Liu ◽  
Jing Hu ◽  
Zhi Guo Zhang
Keyword(s):  
Fluid Flow ◽  
High Efficiency ◽  
Complex Geometry ◽  
Numerical Study ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Check Valve ◽  
Low Noise ◽  
Stop Valve ◽  
Valve Block

Stop valves are commonly used as fluid flow control equipments in many engineering applications. A numerical study of a three-dimensional, complex geometry, stop-check valve was performed for model validation and improved understanding of valve flow features. This paper has provided a numerical investigation of the fluid flow inside a stop valve, including the modeling and the simulation of the stop valves. According to the simulation result of original valve structure, two cone valve block shape with different gradient are presented to bring some optimization to the stop-valve. CFD simulations were conducted for different structure of the valve to verify the performance of the valve after redesign the internal flow structure. The simulation results show that the pressure drop vortex strength, maximum velocity and velocity nonuniformity of valve outlet had been reduced obviously. Furthermore, the results of the three-dimensional optimization analysis of valve shape can be used in the design of low noise and high efficiency valve for industry.

Numerical Study of Rotating Stall in a Vaneless Diffuser

2002 ◽  
Vol 2002.77 (0) ◽  
pp. _6-41_-_6-42_
Author(s):  
Mamoru ABE ◽  
Takeshi SANO ◽  
Tatsuhito Matsushima ◽  
Yoshiki YOSHIDA ◽  
Yoshinobu TSUJIMOTO
Keyword(s):  
Numerical Study ◽  
Rotating Stall ◽  
Vaneless Diffuser

scholarly journals Diamond step-index nanowaveguide to structure light efficiently in near and deep ultraviolet regimes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nasir Mahmood ◽  
Muhammad Qasim Mehmood ◽  
Farooq Ahmad Tahir
Keyword(s):  
Electromagnetic Waves ◽  
High Efficiency ◽  
Uv Light ◽  
Numerical Study ◽  
Three Dimensional ◽  
Building Blocks ◽  
Underlying Mechanism ◽  
Low Loss ◽  
Step Index ◽  
Deep Ultraviolet

Abstract Two-dimensional metamaterials, consisting of an array of ultrathin building blocks, offer a versatile and compact platform for tailoring the properties of the electromagnetic waves. Such flat metasurfaces provide a unique solution to circumvent the limitations imposed by their three-dimensional counterparts. Albeit several successful demonstrations of metasurfaces have been presented in the visible, infrared, and terahertz regimes, etc., there is hardly any demonstration for ultraviolet wavelengths due to the unavailability of the appropriate lossless materials. Here, we present diamond as an ultra-low loss material for the near and deep ultraviolet (UV) light and engineer diamond step-index nanowaveguides (DSINs) to achieve full control over the phase and amplitude of the incident wave. A comprehensive analytical solution of step-index nanowaveguides (supported by the numerical study) is provided to describe the underlying mechanism of such controlled wavefront shaping. Due to the ultra-low loss nature of diamond in near and deep UV regimes, our DSINs and metasurfaces designed (from them) exhibit a decent efficiency of ≈ 84% over the entire spectrum of interest. To verify this high efficiency and absolute control over wavefront, we have designed polarization-insensitive meta-holograms through optimized DSINs for operational wavelength λ = 250 nm.

Sign in / Sign up

Export Citation Format

Share Document