Mechanism of Circumferential Static Pressure Oscillation in a Centrifugal Compressor With Volute

2021 ◽  
Author(s):  
Ce Yang ◽  
Botai Su ◽  
Xin Shi ◽  
Hanzhi Zhang ◽  
Wenli Wang ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Pressure Gradient ◽  
Mass Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Oscillation Amplitude ◽  
Circumferential Direction ◽  
Pressure Amplitude ◽  
High Static Pressure ◽  
Circumferential Pressure

Abstract Under the action of an asymmetric volute structure, a non-uniform flow field is formed in the circumferential direction of the centrifugal compressor. During the throttling process of the compressor at different rotational speeds, the static pressure presents a double-peak distribution of two high static pressure strips, one of which is induced by the volute tongue. However, the formation mechanism of the other high static pressure strip remains unclear. In this regard, computations of the steady and unsteady flows in a centrifugal compressor with and without a volute are performed. The purpose of removing the volute is to simplify the boundary conditions at the diffuser exit, eliminate the circumferential pressure gradient distribution in the volute, and retain the circumferential local high static pressure region induced by the VT; thereafter, the circumferential static pressure distributions in the diffuser and impeller are observed. The results indicate that after eliminating the pressure gradient at the diffuser exit along the rotation direction, only local high static pressure boundary conditions can result in the formation of two high static pressure strips in the diffuser and impeller. The local high static pressure at the exit redistributes the mass flow rate at the impeller outlet, forming two regions with high airflow velocity in the diffuser; this leads to the appearance of two high static pressure strips in the circumferential direction. With the increase in the pressure amplitude of the high static pressure at the diffuser exit, the oscillation amplitude of the circumferential pressure is intensified, and the pressure peaks of the two high static pressure strips increase. However, the circumferential positions of the two static pressure peaks practically remain constant. At large mass flow rates, the pressure reduction along the circumferential direction at the diffuser exit preclude the formation of two circumferential high static pressure strips in the diffuser and impeller.

Effect of circumferential static pressure nonuniformity caused by volute on tip leakage flow in a centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5134-5149 ◽  
Author(s):  
Li Fu ◽  
Ce Yang ◽  
Wenrui Bao ◽  
Hanzhi Zhang ◽  
Changmao Yang ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Centrifugal Compressor ◽  
Vortex Core ◽  
Static Pressure ◽  
Circumferential Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
High Static Pressure

For a centrifugal compressor with volute, the flow field is circumferentially nonuniform because of the volute asymmetrical structure and leads to a circumferential difference in the tip leakage flow. In this work, the compressor performance and the casing wall static pressure distribution are measured, and the results are compared with the time-averaged results of the unsteady calculation to verify the reliability of the simulation. The results show a relationship between the tip leakage vortex trajectory and the high static pressure region in the diffuser, based on which a prediction model is established for the reverse propagation of pressure waves caused by a volute tongue. Influenced by the volute asymmetric structure, the trajectory, shape, and strength of the tip leakage vortex at different circumferential positions differs significantly. The tip leakage vortex trajectory affected by the high static pressure is more inclined to a circumferential direction because the tip leakage flow velocity flowing out of the suction surface is reduced, and the tip leakage flow with low velocity is subjected to the high-pressure gradient in a passage. Moreover, the tip leakage vortex breakdown in different passages differs significantly. A tip leakage vortex core more inclined towards the streamwise direction is more likely to break down than a tip leakage vortex core inclined towards the circumferential direction because of the larger reverse pressure gradient.

scholarly journals Experimental Investigation of the Circumferential Static Pressure Distortion in Centrifugal Compressor Stages

1997 ◽  
Author(s):  
D. Hagelstein ◽  
R. Van den Braembussche ◽  
R. Keiper ◽  
M. Rautenberg
Keyword(s):  
Cross Section ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Radial Force ◽  
Experimental Investigations ◽  
Constant Cross Section ◽  
Vaned Diffuser ◽  
Radial Compressor ◽  
Large Pressure ◽  
Circumferential Pressure

The flow in a centrifugal compressor stage is dominated by the geometry of the impeller, the diffuser and the exit collecting chamber. Asymmetries of the flow field in the annular space behind the impeller may create a circumferential pressure distortion, influencing the energy transfer by the impeller in a negative way, creating variable force on the impeller blades and a radial force on the shaft. Experimental investigations of the circumferential static pressure variations have been carried out on a large radial compressor test stand. Measurements with various impellers, diffusers and collecting chambers show the influence of geometrical modifications on the flow and compressor characteristics. It is shown how a concentric exit chamber results in a very large pressure distortion in the diffuser. Although the amplitude of this distortion is increasing towards the diffuser inlet, it has a negligible effect on the pressure distortion upstream of the impeller. It is further shown how the asymmetry of the flow in the diffuser can be reduced either by using a throttling ring at the diffuser exit, a vaned diffuser or by replacing the constant cross section collector by a volute with circumferentially increasing cross section.

Nonaxisymmetric Study of Tip Leakage Flow in a Centrifugal Compressor With a Volute During Stall Process

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Ce Yang ◽  
Botai Su ◽  
Li Fu ◽  
Hang Zhang
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Leading Edge ◽  
Work Capacity ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
High Static Pressure ◽  
Circumferential Nonuniformity

Abstract Tip leakage flow (TLF) patterns, which affect compressor performance, are closely related to compressor stability. To date, minimal attention has been given to circumferential nonuniformity of the TLF in a centrifugal compressor with a nonaxisymmetric volute structure. In this study, the circumferential difference of the TLF in a centrifugal compressor with a volute during the stall process is analyzed. The circumferential nonuniformity of tip leakage vortex (TLV) trajectories, loading distribution near the tip, and distance between the TLV core and the leading edge (LE) of splitter blades were also investigated. It is shown that in the circumferential direction, there are two peaks associated with the angle (α) between the TLV trajectory of the seven main blades and the axial direction. As the stall process progresses, the blade whose LE is affected by the high static pressure band (PP) induced by the volute tongue (VT) loses its work capacity first and the α difference between this blade and the other blades increases. In addition, the tip loading and TLF velocity of the blade whose LE is affected by the high static pressure band induced by the VT are at a minimum, and the flow loss in the tip clearance is higher. There is a phenomenon of the TLV breakdown. When the blade trailing edge (TE) is located in the low static pressure region, TLV streamlines appear as a significant turn at the breakdown point. However, the TLV streamlines at other circumferential positions do not exhibit this phenomenon.

Experimental Study of the Swirling Flow in the Internal Volute of a Centrifugal Compressor

1991 ◽  
Author(s):  
E. Ayder ◽  
R. Van Den Braembussche
Keyword(s):  
Flow Structure ◽  
Cross Section ◽  
Mass Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Swirling Flow ◽  
Rectangular Cross Section ◽  
High Mass ◽  
Radial Velocity Component ◽  
The Cross

A detailed study of the swirling flow in a rectangular volute of a centrifugal compressor is presented. The 3D flow field has been measured by means of a five hole probe at six different cross sections for three different operating points of the compressor. For high mass flow, the large radial velocity component at the diffuser exit creates a strong swirling flow with a forced vortex type of velocity distribution. The centrifugal force resulting from this motion is balanced by the increase of static pressure from the swirl center to the volute wall. Due to the effect of circumferential curvature a zone of high through flow velocity occurs next to the volute inner wall. Less swirl is generated for optimum mass flow resulting in smaller pressure gradients over the cross section. Low energy fluid accumulates near the inner wall of the cross section. For low mass flow, a large region of separated flow is observed and more uniform static pressure has been measured over the cross section. The effect of the tongue on the flow structure in the first and last cross section is also discussed. This study is the follow-up of previous studies described in ASME paper 89-GT-183 and 90-GT-49. The results obtained verify the previous studies and provide a better understanding of the flow structure inside internal volutes of rectangular cross section.

Circumferential Flow Differences in the Double-Sided Centrifugal Compressor With Non-Balanced Inlets

2016 ◽  
Author(s):  
Ce Yang ◽  
Yixiong Liu ◽  
Wangxia Wu ◽  
Lei Jing ◽  
Benjiang Wang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Axial Velocity ◽  
Static Pressure ◽  
Internal Flow ◽  
Circumferential Direction ◽  
Flow Structures ◽  
Blade Passage ◽  
Pressure Distributions ◽  
Inlet Conditions

A double-sided centrifugal compressor consists of two impellers whose inlets are non-balanced, with one side of the impeller connected to the straight duct, and the other connected to the bending duct. This leads to the differences in the inlet conditions of the double-sided impeller, resulting in the differences in the flow structures of the rear impeller along the circumferential direction. In this work, aiming at analyzing the flow structures of the rear impeller, diffuser and volute internal in three flow rate conditions, the internal flow field of the double-sided centrifugal compressor was calculated in a numerical method. It is found that the inlet bending duct results in significant inlet axial velocity difference of the rear impeller along circumferential direction. The axial velocity differences at high span positions become more obvious with the increase of the flow rate. Moreover, the jet-wake structures among the blade passage outlets are also various. At the high static pressure zones of the volute, corresponding blade passage wake regions increase and their sizes are also influenced by the inlet distortion. The circumferential distributions of the static pressure in the diffuser agree well with that in the volute. In the diffuser, the non-uniform degrees of the static pressure distributions are roughly the same at different radius positions and are weakening with the decrease of the flow rate.

scholarly journals The Centrifugal Compressor Inducer

1998 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
The State ◽  
Design Flow ◽  
Pressure Recovery ◽  
Centrifugal Compressors ◽  
High Static Pressure ◽  
Stable Flow ◽  
State Of Art

The function of the centrifugal compressor inducer is to provide wide flow margins from the design flow to the stall and choke flow limits, together with high static pressure recovery. At transonic conditions the inducer becomes the critical to impeller performance in that shock losses and blockage growth diminish stable flow range and may trigger near vertical stage characteristics. The paper covers the various types of inlet configurations upstream of the inducer, followed by a review of the state-of-art inducer design for centrifugal compressors, culminating with some research developments in transonic inducer blading characteristics.

Unsteady Aerodynamic Performance of a Centrifugal Compressor With Oscillating Downstream Static Pressure

2005 ◽  
Author(s):  
H. J. Eum ◽  
S. H. Kang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Method Of Characteristics ◽  
Static Pressure ◽  
Pressure Rise ◽  
Acoustic Resonance ◽  
Specific Frequency ◽  
D Model

In many applications, centrifugal compressors experience various kinds of downstream pressure disturbances which can lead to unstable operation even at the design operating condition. In this paper, 3-D numerical simulations have been carried out to understand the dynamic behaviors of the centrifugal compressor for the pulsation of downstream pressure disturbances and 1-D model using the method of characteristics has been developed to predict the behaviors more effectively. Static pressure disturbances with a frequency range from 25Hz to 1300 Hz and constant amplitude have been introduced at the diffuser exit. Static pressure rise and mass flow rate deviated from the quasi-steady characteristic as the frequency increased. The fluctuation of mass flow rate at the diffuser exit was amplified or attenuated depending on the disturbance frequency. The fluctuation was severely amplified at a specific frequency which seemed to be an acoustic resonance of the present compressor model including an inlet duct, a blade passage and a diffuser. The result of 1-D model showed good agreements with that of 3-D numerical simulation.

Stall inception induced by the volute tongue at centrifugal compressor inlet

2016 ◽  
Vol 231 (5) ◽  
pp. 931-940 ◽  
Author(s):  
Ce Yang ◽  
Yingjun Wang ◽  
Ding Tong ◽  
Changmao Yang ◽  
Yanzhao Li
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Static Pressure ◽  
Leading Edge ◽  
Initial Flow ◽  
Stall Inception ◽  
Pressure Area ◽  
Compressor Inlet ◽  
Pressure Peak ◽  
High Static Pressure

The stall and surge directly impact on the safety and reliability of compressors. The spike-type and modal-type stall inception exist in compressors. At present, few studies pay attention to the stall inception of centrifugal compressor, such as the formation reason for the stall inception and the action by the volute tongue on the stall precursor. This paper investigated the stall characteristics of a high-speed small-flow centrifugal compressor and illustrated the relationship between the volute tongue and the location of stall inception. In addition, the mechanism of stall inception was also clarified. Both the analysis of initial flow structures and the comparison of the frequency spectrum characteristics at different monitoring points show that the spike-type stall occurs at about 115° circumferential position in this centrifugal compressor. The nonaxisymmetric geometry structure of the volute leads to the uneven circumferential pressure distribution. The blockade effect of the volute tongue results in high static pressure area near the volute tongue. The disturbance caused by high static pressure adversely propagates into the diffuser, resulting in the static pressure peak value at different radii. As the pressure peaks adversely migrate to the impeller inlet and induce the leading edge spillover near the corresponding blade, the spike-type stall occurs. Therefore, the volute tongue both induces the stall inception and determines the circumferential position of the stall inception at the centrifugal compressor inlet.

Nonlinear dynamics of a shell encapsulated microbubble near solid boundary in an ultrasonic field

2020 ◽  
Vol 14 (3) ◽  
pp. 7235-7243
Author(s):  
N.M. Ali ◽  
F. Dzaharudin ◽  
E.A. Alias
Keyword(s):  
Oscillation Amplitude ◽  
Ultrasonic Field ◽  
Dynamical Behaviour ◽  
Ultrasound Contrast Agents ◽  
Chaotic Behaviour ◽  
Solid Boundary ◽  
Driving Frequency ◽  
Pressure Amplitude ◽  
Radial Expansion ◽  
Therapeutic Delivery

Microbubbles have the potential to be used for diagnostic imaging and therapeutic delivery. However, the transition from microbubbles currently being used as ultrasound contrast agents to achieve its’ potentials in the biomedical field requires more in depth understanding. Of particular importance is the influence of microbubble encapsulation of a microbubble near a vessel wall on the dynamical behaviour as it stabilizes the bubble. However, many bubble studies do not consider shell encapsulation in their studies. In this work, the dynamics of an encapsulated microbubble near a boundary was studied by numerically solving the governing equations for microbubble oscillation. In order to elucidate the effects of a boundary to the non-linear microbubble oscillation the separation distances between microbubble will be varied along with the acoustic driving. The complex nonlinear vibration response was studied in terms of bifurcation diagrams and the maximum radial expansion. It was found that the increase in distance between the boundary and the encapsulated bubble will increase the oscillation amplitude. When the value of pressure amplitude increased the single bubble is more likely to exhibit the chaotic behaviour and maximum radius also increase as the inter wall-bubble distance is gradually increased. While, with higher driving frequency the maximum radial expansion decreases and suppress the chaotic behaviour.

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