Unsteady Simulation and Analysis on Centrifugal Impeller With Self-Adaptive Casing Treatment

2013 ◽  
Author(s):  
Tong Wang ◽  
Wei Wang ◽  
Chuangang Gu
Keyword(s):  
Boundary Condition ◽  
Back Pressure ◽  
The Self ◽  
Centrifugal Impeller ◽  
Bypass Flow ◽  
Unstable Flow ◽  
Recirculation Flow ◽  
Casing Treatment ◽  
Pressure Boundary Condition ◽  
Self Adaptive

A self-adaptive casing treatment for unshrouded centrifugal compressor was proposed in our previous studies. It is a kind of passive control techniques. The experimental results proved that the stable working range of the compressor was extended greatly with the technique. As for the stability mechanism, there is no convinced explanation. Many researchers believe that the unsteady flow could be one of the key points. In the paper, steady and unsteady numerical simulations were carried out to get the performances of the centrifugal impeller by ANSYS CFX software. The numerical method was validated by comparing with the experimental results. It was found that there were two types of flow pattern in the bleeding-recirculation passages by the numerical simulation with the self-adaptive casing treatment. One was the recirculation flow at the smaller flowrate working conditions and the other was bypass flow at the larger flowrate working conditions. The pressure at the bleeding ports was more than that at the recirculation port at the smaller flowrate. It would result in the recirculation flow in the bleeding-recirculation passages. Otherwise, it would result in the bypass flow in the bleeding-recirculation passages. The numerical results of each bleeding-recirculation passage provided the variation of mass flowrate in it with the pressure difference. The relation of the pressure drop coefficient and Reynolds number based on the bleeding hole was fitted. It was different for the recirculation flow and bypass flow. It is helpful to decide the position of the bleeding ports during the centrifugal compressor design process. Moreover, an unsteady numerical simulation method with the increasing back pressure boundary condition was proposed to investigate the unsteady process approaching to the numerical stall point or unstable flow. The dynamic pressure data in impeller and diffuser were recorded. The amplitudes of the data were picked up to compare the time dependent process. The dynamic pressure at the inlet of diffuser fluctuated more strongly than those at the other positions while the back pressure was increased to the numerical stall point. The experimental data provided the similar phenomena. It suggested that the unstable flow tendency could be caught up by the unsteady simulation process with the increasing back pressure boundary condition. Furthermore, the time dependent flow fields at the blade tip region were compared on the conditions with and without the self-adaptive casing treatment. The effect of the self-adaptive casing treatment was proved by unsteady numerical method with the increasing back pressure boundary condition. The stability mechanism of the self-adaptive casing treatment was explained to some extent.

Suppression of Unstable Flow at Small Flow Rates in a Centrifugal Blower by Controlling Tip Leakage Flow and Reverse Flow

2005 ◽  
Vol 127 (1) ◽  
pp. 76-83 ◽  
Author(s):  
Mashiro Ishida ◽  
Taufan Surana ◽  
Hironobu Ueki ◽  
Daisaku Sakaguchi
Keyword(s):  
Reverse Flow ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Centrifugal Blower ◽  
Unstable Flow ◽  
Ring Groove ◽  
Recirculation Flow ◽  
Tip Leakage ◽  
Small Flow

The effects of the inlet recirculation arrangement on inducer stall and the diffuser width on diffuser stall in a high-specific-speed-type centrifugal impeller with inducer were analyzed by numerical simulation and also verified experimentally. It was found that the incipient unstable flow occurs due to a rolling-up vortex flow, resulting from an interaction between the tip leakage flow and the reverse flow accumulated at the pressure side immediately downstream of the inducer tip throat, in which a strong streamwise component of vorticity is included. By forming the inlet recirculation flow, the tip leakage vortex is effectively sucked into the suction ring groove, and the flow incidence is decreased simultaneously. The unstable flow range of the test blower was reduced significantly by about 45% without deteriorating the impeller characteristics by implementing optimally both the ring groove arrangement and the narrowed diffuser width.

Suppression of Unstable Flow at Small Flow Rates in a Centrifugal Blower by Controlling Tip Leakage Flow and Reverse Flow

2004 ◽  
Author(s):  
Masahiro Ishida ◽  
Taufan Surana ◽  
Hironobu Ueki ◽  
Daisaku Sakaguchi
Keyword(s):  
Reverse Flow ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Centrifugal Blower ◽  
Unstable Flow ◽  
Ring Groove ◽  
Recirculation Flow ◽  
Tip Leakage ◽  
Small Flow

The effects of the inlet recirculation arrangement on inducer stall and the diffuser width on diffuser stall in a high specific speed type centrifugal impeller with inducer were analyzed by a numerical simulation and also verified experimentally. It is found that the incipient unstable flow occurs due to a rolling-up vortex flow resulting from an interaction between the tip leakage flow and the reverse flow accumulated at the pressure side immediately downstream of the inducer tip throat in which a strong streamwise component of vorticity is included. By forming the inlet recirculation flow, the tip leakage vortex is effectively sucked into the suction ring groove, and the flow incidence is decreased simultaneously. The unstable flow range of the test blower was reduced significantly by about 45% without deteriorating the impeller characteristics by implementing optimally both the ring groove arrangement and the narrowed diffuser width.

Effect of Pre-Whirl on Unstable Flow Suppression in a Centrifugal Impeller With Ring Groove Arrangement

2006 ◽  
Author(s):  
Masahiro Ishida ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki
Keyword(s):  
Flow Rate ◽  
Guide Vane ◽  
Pressure Rise ◽  
Centrifugal Impeller ◽  
Unstable Flow ◽  
Ring Groove ◽  
Rate Range ◽  
Recirculation Flow ◽  
Setting Angle ◽  
Flow Rate Range

In order to obtain a wider operating range in a centrifugal impeller with inducer, the effect of the pre-whirl induced by the inlet recirculation flow on the flow incidence and the impeller characteristics were analyzed numerically and compared with the experimental results. In order to control the swirl intensity of the recirculation flow, guide vanes were installed circumferentially in the annular bypass of the ring groove arrangement, and the setting angle of the guide vane was changed. The fundamental concept for surge suppression is to achieve the flow incidence less than or close to the critical one. A too large-positive flow incidence can be reduced by increasing the recirculation flow rate determined by the pressure difference between the two ring groove positions, on the other hand, a higher pressure rise in the inducer can be obtained at the flow incidence close to the critical one by suppressing the pre-whirl induced by the recirculation flow. It is clearly shown that the better impeller characteristics and the large recirculation flow rate can be achieved by giving a suitable setting angle of the guide vane. The unstable flow rate range of the tested impeller was reduced by about 53% almost without deterioration of the impeller efficiency in the whole flow rate range.

A Study on the Influence of Hole’s Diameter With Holed Casing Treatment

2011 ◽  
Author(s):  
Wei Xu ◽  
Tong Wang ◽  
Chuangang Gu ◽  
Liang Ding
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Results ◽  
Radial Position ◽  
Bypass Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
Velocity Magnitude ◽  
Adaptive Effect ◽  
New Type ◽  
Self Adaptive

The holed casing treatment is a new type of casing treatment with self-adaptability for centrifugal compressor with unshrouded impellers. It is demonstrated experimentally and numerically that both of the stall margin and the choked margin of the compressor can be expanded by the treatment. Numerical results indicate that there is a reinjected flow in the holes when the compressor works at low flowrate conditions and a bypass flow at high flowrate conditions. Hole’s diameter is an important parameter for the holed casing treatment. Five cases of different diameter (1.0mm, 1.5mm, 2.0mm, 2.5mm and 3.0mm) were carried out to reveal its influence. Both the stall margin and efficiency are improving with increasing of the hole’s diameter in the cases of diameter below than 2.5mm. At diameter of 2.5mm, the stall margin increment and the efficiency of the compressor are the highest among all 5 cases. However, in the case of 3.0mm, the stable working range enhancing as well as the efficiency is weakened because the velocity magnitude of the reinjected flow decreases. Therefore a key principle of choosing the diameter and the radial position of the hole is presented in the paper to get the best self-adaptive effect: enhancing stable running range as much as possible and keeping higher efficiency.

Numerical Study on the Performance of a Centrifugal Impeller With Self-Adaptive Casing Treatment

2018 ◽  
Author(s):  
M. Q. Gong ◽  
H. S. Chen ◽  
Y. J. Xu ◽  
J. Q. Deng
Keyword(s):  
Flow Field ◽  
Turbulence Model ◽  
Numerical Study ◽  
Turbulence Models ◽  
Field Analysis ◽  
Centrifugal Impeller ◽  
Low Velocity ◽  
Casing Treatment ◽  
Sst Turbulence Model ◽  
Self Adaptive

The stall margin and choke margin of centrifugal compressor could be increased by using Self-Adaptive Casing Treatment (SACT). The previous numerical research mainly focuses on making parametric optimization rather than the selection of turbulence model and flow field analysis of the compressor with SACT. In this work, the 3D steady state simulations were carried out to obtain the performance and flow field of the Krain impeller with and without SACT by ANSYS-CFX. Four turbulence models including k-Epsilon turbulence model, RNG k-Epsilon turbulence model, Shear Stress Transport (SST) turbulence model and BSL Reynolds Stress (BSL) turbulence model were used to simulate the Krain impeller with a vaneless constant area diffuser. The numerical data were validated by the experimental data in reference. The results of this study showed that different turbulence models led to differences in performance predictions and flow field characteristics, and the overall performance and flow field features could be predicted more accurately by using SST turbulence model. The bypass flow and reinjected flow were respectively observed in the hole when the Krain impeller with SACT worked at large and small mass flow rate conditions. And the stable working range of the Krain impeller was expanded by using SACT. In addition, the development of the low-velocity fluid at the blade tip region was restrained with the application of SACT.

A New Type of Self-Adaptive Casing Treatment for a Centrifugal Compressor

2010 ◽  
Author(s):  
Tong Wang ◽  
Wei Xu ◽  
Chuangang Gu ◽  
Jun Xiao
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Centrifugal Impeller ◽  
Stable Operation ◽  
Stable Range ◽  
Stall Margin ◽  
Casing Treatment ◽  
Surge Margin ◽  
New Type ◽  
Self Adaptive

Enhancing compressor stall and surge margin is very important for the development of turbo compressors. Casing treatment is an effective method to expand the stall margin and thus the stable operation range but it generally comes with a drop in efficiency. A new type of casing treatment with self-adaptivity for an unshrouded centrifugal impeller is presented in this paper. The idea of the self-adaptive casing treatment is to automatically control the bleeding flow rate through a set of round holes on the stationary shroud casing. When stall is approached, the casing treatment system will redirect the low-momentum fluid to improve the flow in the impeller and to extend its stable range. However, the system will not bleed or bleed a little flow when the operating point is far from the stall point. This decreases the bleeding-recirculation loss and increases the efficiency compared to bleed-slot casing treatment used before. The experimental results show that the centrifugal compressor with the new casing treatment can extend stable range by about 20% while the efficiency over the whole operating range increases by 0.2 to 1.5%. The theoretical results using CFD analyses agree with the experimental ones in the tendency for both pressure ratio and efficiency. Moreover some possible reasons for further enhancing the stable range are suggested in the paper. Based on our experiences, there should be existed a proper combination of impeller rotating speed, position and numbers of bleed port and other parameters that will maximize both surge margin range and efficiency.

scholarly journals A Solution to Pressure Equation with Its Boundary Condition of Combining Tangential and Normal Pressure Relations

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1507
Author(s):  
Hui Xiao ◽  
Wei Liu
Keyword(s):  
Boundary Condition ◽  
Numerical Algorithm ◽  
Iteration Process ◽  
Normal Pressure ◽  
Constitutive Law ◽  
Navier Stokes ◽  
Numerical Verification ◽  
Pressure Equation ◽  
Navier Stokes Equation ◽  
Pressure Boundary Condition

Pressure is a physical quantity that is indispensable in the study of transport phenomena. Previous studies put forward a pressure constitutive law and constructed a partial differential equation on pressure to study the convection with or without heat and mass transfer. In this paper, a numerical algorithm was proposed to solve this pressure equation by coupling with the Navier-Stokes equation. To match the pressure equation, a method of dealing with pressure boundary condition was presented by combining the tangential and normal direction pressure relations, which should be updated dynamically in the iteration process. Then, a solution to this pressure equation was obtained to bridge the gap between the mathematical model and a practical numerical algorithm. Through numerical verification in a circular tube, it is found that the proposed boundary conditions are applicable. The results demonstrate that the present pressure equation well describes the transport characteristics of the fluid.

scholarly journals Decomposition of Vibration Signals into Deterministic and Nondeterministic Components and its Capabilities of Fault Detection and Identification

2009 ◽  
Vol 19 (2) ◽  
pp. 327-335 ◽  
Author(s):  
Tomasz Barszcz
Keyword(s):  
Fault Detection ◽  
Adaptive Filter ◽  
Complex Structure ◽  
Reference Signal ◽  
The Self ◽  
Noise Component ◽  
Vibration Signals ◽  
Detection And Identification ◽  
Fault Detection And Identification ◽  
Self Adaptive

Decomposition of Vibration Signals into Deterministic and Nondeterministic Components and its Capabilities of Fault Detection and IdentificationThe paper investigates the possibility of decomposing vibration signals into deterministic and nondeterministic parts, based on the Wold theorem. A short description of the theory of adaptive filters is presented. When an adaptive filter uses the delayed version of the input signal as the reference signal, it is possible to divide the signal into a deterministic (gear and shaft related) part and a nondeterministic (noise and rolling bearings) part. The idea of the self-adaptive filter (in the literature referred to as SANC or ALE) is presented and its most important features are discussed. The flowchart of the Matlab-based SANC algorithm is also presented. In practice, bearing fault signals are in fact nondeterministic components, due to a little jitter in their fundamental period. This phenomenon is illustrated using a simple example. The paper proposes a simulation of a signal containing deterministic and nondeterministic components. The self-adaptive filter is then applied—first to the simulated data. Next, the filter is applied to a real vibration signal from a wind turbine with an outer race fault. The necessity of resampling the real signal is discussed. The signal from an actual source has a more complex structure and contains a significant noise component, which requires additional demodulation of the decomposed signal. For both types of signals the proposed SANC filter shows a very good ability to decompose the signal.

Optimization of Inlet Ring Groove Arrangement for Suppression of Unstable Flow in a Centrifugal Impeller

2005 ◽  
Author(s):  
Masahiro Ishida ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki
Keyword(s):  
Flow Rate ◽  
The Other ◽  
Centrifugal Impeller ◽  
Shape Parameters ◽  
Unstable Flow ◽  
Ring Groove ◽  
Flow Rates ◽  
Small Flow ◽  
Specific Speed ◽  
Large Flow

An optimization of the inlet ring groove arrangement has been pursued in the present study for obtaining better impeller characteristics and a wider operation range at both small and large flow rates in a high specific speed type centrifugal impeller with inducer. The effects of the shape parameters with respect to the inlet ring groove on the impeller characteristic and the flow incidence were analyzed mainly based on numerical simulations, but also compared to the experimental results. At small flow rates, a significant improvement in the impeller characteristic is achieved due to reduction in the excessive-positive flow incidence by optimizing both location and width of the rear groove near the inducer tip throat. On the other hand, the impeller characteristic is improved at large flow rates by implementing the corner radius at the rear groove edge and by placing another front ring groove in the suction pipe. As a result, by the optimized configuration of the front and rear ring grooves, the unstable flow range of the test impeller can be reduced by about 50% without deterioration of the impeller characteristic even at the 125% flow rate.

An Impact of Self-Recirculation Casing Treatment (SRCT) Configurations on Impeller Stall Margin and the Flow Field

2012 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Angle ◽  
Stall Margin ◽  
Casing Treatment ◽  
Swirl Velocity ◽  
Inlet Swirl ◽  
Unsteady Simulation

The present paper describes an investigation of stall margin enhancement and a detailed analysis of the impeller flow field due to self-recirculation casing treatment (SRCT) configuration of a high-speed small-size centrifugal impeller. The influence of different SRCT configurations on the impeller flow field at near-stall condition has been analyzed, highlighting the improvement in stall flow ability. This paper also discusses the influence of the SRCT configurations on the inlet flow angle, inlet swirl velocity and loss distribution in the impeller passage to understand the mechanism of the SRCT configurations in enhancing the stall margin of the impeller. The variation of the bleed flow rate at different operating conditions is also presented in this paper. Finally, the time-averaged unsteady simulation results at near-stall point are presented and compared with steady-state solutions.

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