scholarly journals Investigation on the Flow Field Entropy Structure of Non-Synchronous Blade Vibration in an Axial Turbocompressor

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1372
Author(s):  
Mingming Zhang ◽  
Anping Hou
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Guide Vane ◽  
Leading Edge ◽  
Inlet Guide Vane ◽  
Tip Leakage Flow ◽  
Good Correspondence ◽  
Blade Vibration ◽  
Tip Leakage ◽  
Spiral Vortex

In order to explore the inducing factors and mechanism of the non-synchronous vibration, the flow field structure and its formation mechanism in the non-synchronous vibration state of a high speed turbocompressor are discussed in this paper, based on the fluid–structure interaction method. The predicted frequencies fBV (4.4EO), fAR (9.6EO) in the field have a good correspondence with the experimental data, which verify the reliability and accuracy of the numerical method. The results indicate that, under a deviation in the adjustment of inlet guide vane (IGV), the disturbances of pressure in the tip diffuse upstream and downstream, and maintain the corresponding relationship with the non-synchronous vibration frequency of the blade. An instability flow that developed at the tip region of 90% span emerged due to interactions among the incoming main flow, the axial separation backflow, and the tip leakage vortices. The separation vortices in the blade passage mixed up with the tip leakage flow reverse at the trailing edge of blade tip, presenting a spiral vortex structure which flows upstream to the leading edge of the adjacent blade. The disturbances of the spiral vortexes emerge to rotate at 54.5% of the rotor speed in the same rotating direction as a modal oscillation. The blade vibration in the turbocompressor is found to be related to the unsteadiness of the tip flow. The large pressure oscillation caused by the movement of the spiral vortex is regarded as the one of the main drivers for the non-synchronous vibration for the present turbocompressor, besides the deviation in the adjustment of IGV.

Influence of different blade numbers on the performance of “saddle zone” in a mixed flow pump

2021 ◽  
pp. 095765092110460
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi ◽  
Fei Tian ◽  
Shuo Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Leading Edge ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Flow Angle ◽  
Tip Leakage ◽  
Vorticity Transport ◽  
Flow Pump

In order to study the effect of different numbers of impeller blades on the performance of mixed-flow pump “saddle zone”, the external characteristic test and numerical simulation of mixed-flow pumps with three different impeller blade numbers were carried out. Based on high-precision numerical prediction, the internal flow field and tip leakage flow field of mixed flow pump under design conditions and stall conditions are investigated. By studying the vorticity transport in the stall flow field, the specific location of the high loss area inside the mixed flow pump impeller with different numbers of blades is located. The research results show that the increase in the number of impeller blades improve the pump head and efficiency under design conditions. Compared to the 4-blade impeller, the head and efficiency of the 5-blade impeller are increased by 5.4% and 21.9% respectively. However, the increase in the number of blades also leads to the widening of the “saddle area” of the mixed-flow pump, which leads to the early occurrence of stall and increases the instability of the mixed-flow pump. As the mixed-flow pump enters the stall condition, the inlet of the mixed-flow pump has a spiral swirl structure near the end wall for different blade numbers, but the depth and range of the swirling flow are different due to the change in the number of blades. At the same time, the change in the number of blades also makes the flow angle at 75% span change significantly, but the flow angle at 95% span is not much different because the tip leakage flow recirculates at the leading edge. Through the analysis of the vorticity transport results in the impeller with different numbers of blades, it is found that the reasons for the increase in the values of the vorticity transport in the stall condition are mainly impacted by the swirl flow at the impeller inlet, the tip leakage flow at the leading edge and the increased unsteady flow structures.

The Influence of Tip Clearance Momentum Flux on Stall Inception in a High-Speed Axial Compressor

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Joshua D. Cameron ◽  
Matthew A. Bennington ◽  
Mark H. Ross ◽  
Scott C. Morris ◽  
Juan Du ◽  
...  
Keyword(s):  
Momentum Flux ◽  
High Speed ◽  
Axial Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Axial Position ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage

Experimental and numerical studies were conducted to investigate tip-leakage flow and its relationship to stall in a transonic axial compressor. The computational fluid dynamics (CFD) results were used to identify the existence of an interface between the approach flow and the tip-leakage flow. The experiments used a surface-streaking visualization method to identify the time-averaged location of this interface as a line of zero axial shear stress at the casing. The axial position of this line, denoted xzs, moved upstream with decreasing flow coefficient in both the experiments and computations. The line was consistently located at the rotor leading edge plane at the stalling flow coefficient, regardless of inflow boundary condition. These results were successfully modeled using a control volume approach that balanced the reverse axial momentum flux of the tip-leakage flow with the momentum flux of the approach fluid. Nonuniform tip clearance measurements demonstrated that movement of the interface upstream of the rotor leading edge plane leads to the generation of short length scale rotating disturbances. Therefore, stall was interpreted as a critical point in the momentum flux balance of the approach flow and the reverse axial momentum flux of the tip-leakage flow.

scholarly journals Vortex Dynamics Analysis of Internal Flow Field of Mixed-Flow Pump under Alford Effect

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3575
Author(s):  
Shuo Li ◽  
Wei Li ◽  
Leilei Ji ◽  
Weidong Shi ◽  
Ramesh K. Agarwal
Keyword(s):  
Flow Field ◽  
Vortex Core ◽  
Guide Vane ◽  
Internal Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Tip Leakage ◽  
L1 And L2 ◽  
The Impact ◽  
Flow Pump

A multi-region dynamic slip method was established to study the internal flow characteristics of the mixed-flow pump under the Alford effect. The ANSYS Fluent software and the standard k-ε two-equation model were used to numerically predict the mixed-flow pump’s external characteristics and analyze the forces on the impeller and guide vane internal vortex structure and non-uniform tip gap of the mixed-flow pump at different eccentric distances. The research results show that the external characteristic results of the numerical calculation are consistent with the experimental measurement. The head error of the design flow operating point is about 5%, and the efficiency error is no more than 3%, indicating the high accuracy of numerical calculation. Eccentricity has a significant influence on the flow field in the tip area of the mixed-flow pump impeller, the distribution of vortex core in the impeller presents obvious asymmetry, the strength and distribution area of the vortex core in the small gap area of the tip increase obviously, which aggravates the flow instability and increases the energy loss. With the increase of eccentricity, the strength and number of vortex core structures in the guide vane also increase significantly, and obvious flow separation occurs near the inlet of the guide vane suction surface on the eccentric side of the impeller. The circumferential distribution of L1 and L2 values represents the friction pressure gap in the eccentric state, and the eccentricity has a more noticeable effect on L1 and L2 values at the small gap; With the increase of eccentricity, the values of vorticity moment components L1 and L2 increase, and the Alford moment on the impeller increases. The leading-edge region of the blade is the main part affected by the unstable torque of the flow field. With the increase of eccentricity, the impact degree of tip leakage flow deepens, and the change of the tip surface pressure is the most obvious. The impact area of tip leakage flow is mainly concentrated in the first half of the impeller channel, which has an impact on the blade inlet flow field but has little impact on the blade outlet flow field.

Unsteady Three-Dimensional Flow Phenomena Due to Breakdown of Tip Leakage Vortex in a Transonic Axial Compressor Rotor

2004 ◽  
Author(s):  
K. Yamada ◽  
M. Furukawa ◽  
T. Nakano ◽  
M. Inoue ◽  
K. Funazaki
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Vortex Breakdown ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Compressor Rotor

Unsteady three-dimensional flow fields in a transonic axial compressor rotor (NASA Rotor 37) have been investigated by unsteady Reynolds-averaged Navier-Stokes simulations. The simulations show that the breakdown of the tip leakage vortex occurs in the compressor rotor because of the interaction of the vortex with the shock wave. At near-peak efficiency condition small bubble-type breakdown of the tip leakage vortex happens periodically and causes the loading of the adjacent blade to fluctuate periodically near the leading edge. Since the blade loading near the leading edge is closely linked to the swirl intensity of the tip leakage vortex, the periodic fluctuation of the blade loading leads to the periodic breakdown of the tip leakage vortex, resulting in self-sustained flow oscillation in the tip leakage flow field. However, the tip leakage vortex breakdown is so weak and small that it is not observed in the time-averaged flow field at near-peak efficiency condition. On the other hand, spiral-type breakdown of the tip leakage vortex is caused by the interaction between the vortex and the shock wave at near-stall operating condition. The vortex breakdown is found continuously since the swirl intensity of tip leakage vortex keeps strong at near-stall condition. The spiral-type vortex breakdown has the nature of self-sustained flow oscillation and gives rise to the large fluctuation of the tip leakage flow field, in terms of shock wave location, blockage near the rotor tip and three-dimensional separation structure on the suction surface. It is found that the breakdown of the tip leakage vortex leads to the unsteady flow phenomena near the rotor tip, accompanying large blockage effect in the transonic compressor rotor at the near-stall condition.

Improvement in the stability of a turbocharger centrifugal compressor by tip leakage control

2016 ◽  
Vol 231 (5) ◽  
pp. 700-714 ◽  
Author(s):  
Saeed Mirzaee ◽  
Xinqian Zheng ◽  
Yun Lin
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Dominant Factor ◽  
Tip Leakage Flow ◽  
Jet Injection ◽  
Tip Leakage ◽  
Air Jet ◽  
Stable Flow

The occurrence of surge or stall in a centrifugal compressor and the role of the tip clearance flow in the instability in the centrifugal compressor are investigated in this study. A computational method is used to study the flow field in the centrifugal compressor in order to gain a better understanding of the surge or stall mechanism. It is found that, near surge or stall conditions, the tip leakage flow at the leading edge deflects more upstream; as the deflection increases, a more severe spillage occurs which finally leads to instability of the compressor. A ring air jet injection is used to eliminate the instabilities and to extend the stable flow range of the compressor. Using an air jet injection, the stable flow range of the compressor was successfully increased with minimal decrease in the efficiency of the compressor. The effects of different injection parameters such as the mass flow, the yaw angle, the injection angle, the slot width and the slot distance on the compressor flow field are studied, and an optimum design for the air jet injection is developed. Further investigation of the compressor with the optimum injection configuration shows that, near surge or stall conditions, the tip leakage at the leading edge is still under control, manifesting a much smaller spillage than does the Dresser–Rand Datum compressor without an air injection. The dominant factor for the instability of the compressor with an injection is found to be the leading-edge separation rather than the tip leakage.

Rotating Instabilities Versus Rotating Stall in a High-Speed Centrifugal Compressor

2018 ◽  
Author(s):  
Julissa Grondin ◽  
Isabelle Trébinjac ◽  
Nicolas Rochuon
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Leading Edge ◽  
Propagation Speed ◽  
Rotating Stall ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Unsteady Rans ◽  
Measured Speed ◽  
The Subject

The subject of the paper is a high speed unshrouded centrifugal compressor in which rotating instabilities have been measured near the stage stall point. The impeller is studied numerically by means of unsteady RANS simulations, and the results are compared to experimental measurements. Instead of rotating instabilities, the numerical results directly capture a rotating stall pattern in which a tornado-like separation vortex is shed due to a separation at the impeller leading edge, and propagates around the circumference. The vortex has one end attached to the casing and the other end attached to the pressure side of the blade. Its propagation speed is within 10% from the measured speed of the rotating instabilities. Because of the high pressure gradient the tip leakage flow crosses the impeller front and thus convects the vortex in front of the adjacent blade. The spillage of the vortex in the adjacent channel convects radial and azimuthal vorticity onto the next blade. This triggers the inception of a new vortex, and induces the propagation of the rotating stall cells.

Evaluating Splitter Blade Designs to Avoid Impeller Failure in a High-Speed Unshrouded Centrifugal Compressor

2019 ◽  
Author(s):  
Alex Curtin ◽  
Reid A. Berdanier ◽  
Robert F. Kunz ◽  
Michael L. Jonson
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Guide Vane ◽  
Leading Edge ◽  
Cfd Modeling ◽  
Inlet Guide Vane ◽  
Cfd Model ◽  
Blade Flutter ◽  
Unsteady Loading ◽  
Type Of Failure

Abstract This study investigates splitter blade failures experienced during testing of an unshrouded transonic centrifugal compressor. Specifically, when the impeller was deeply throttled using an upstream inlet guide vane to introduce significant pre-swirl, the splitter blades exhibited cracking near the root of the leading edge. The observed failures are of particular interest because the impeller does not exhibit a mode shape typical of this type of failure corresponding to either the upstream IGV or downstream diffuser vane count, nor the anticipated surge frequencies. Accordingly, modal analysis and CFD modeling were performed leading to an understanding of the failure mechanism, and a successful splitter blade cut-back solution was implemented. Specifically, excitation sources developed from a CFD model of the IGV and impeller were used in a blade flutter calculation, in order to determine the aerodynamic damping and unsteady loading on the blade. The CFD model indicates that shockwaves arise near the splitter leading edge for this off-design condition. Due to interactions with the high incidence/separated boundary layer, these shockwaves exhibit streamwise unsteadiness, thereby leading to the observed failure mechanisms. It was determined that by cutting back the splitter blade at the leading edge, the failure could be avoided while minimally affecting the overall stage performance.

Visualizations of Flow Structures in the Rotor Passage of an Axial Compressor at the Onset of Stall

2016 ◽  
Author(s):  
Huang Chen ◽  
Yuanchao Li ◽  
David Tan ◽  
Joseph Katz
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Flow Structures ◽  
Tip Leakage Flow ◽  
High Speed Imaging ◽  
Vortical Structures ◽  
Tip Leakage

Flow visualizations and stereoscopic PIV (SPIV) measurements are carried out to study the flow phenomena developing in the rotor passage of an axial compressor at the onset of stall. Experiments have been performed in the JHU optically index-matched facility, using acrylic blades and liquid that have the same optical refractive index. The blade geometries are based on the first one and a half stages of the Low Speed Axial Compressor (LSAC) facility at NASA Glenn. The SPIV measurements provide detailed snapshots and ensemble statistics on the flow in a series of meridional planes. Data recorded in closely spaced planes enable us to obtain ensemble averaged 3D vorticity distributions. High speed imaging of cavitation, performed at low pressure, is used to qualitatively visualize the vortical structures within the rotor passage. The observations are performed just above and at stall conditions. At pre-stall condition, shortly after it rolled up, the tip leakage vortex (TLV) breaks up into widely distributed intermittent vortical structures. In particular, interaction of the backward tip leakage flow with the nearly opposite direction main passage flow under (radially inward) it results in periodic generation of large scale vortices that extend upstream, from the suction side (SS) of one blade to the pressure side (PS) or even near the leading edge of the next blade. When these structures penetrate to the next passage, they trigger formation of a similar phenomenon there, initiating a process that sustains itself. Once they form, these vortices rotate with the blade, indicating little through flow in the tip region. The 3D velocity and vorticity distributions confirm the presence of these large flow structures at the transition between the high circumferential velocity region below the TLV center and the main flow deeper in the passage. Further reduction in flow rate into the stall range caused a rapid increase in the number and scale of these vortices, demonstrating that their formation and proliferation plays a key role in the onset of stall.

Experimental and Numerical Examinations of a Transonic Compressor-Stage With Casing Treatment

2013 ◽  
Author(s):  
D. Schönweitz ◽  
M. Voges ◽  
G. Goinis ◽  
G. Enders ◽  
E. Johann
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Guide Vane ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Tip Leakage Vortex ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Transonic Compressor

The flow in the blade tip vicinity of the transonic first stage of a multi-stage axial flow compressor with variable inlet guide vane (IGV) and casing treatment (CT) above the rotor is investigated experimentally and numerically with focus on the effects of the CT on flow structures and compressor performance. For the experimental part of this study, conventional performance instrumentation is used to estimate the operating condition of the compressor. Radial distributions of total temperature and total pressure are taken at the leading edges of the stators for comparison with simulations as well as for adjusting the operating conditions of the compressor. The velocity field in the rear part of the first-rotor is determined with Particle Image Velocimetry (PIV) at 90% and 96% radial height using two periscope light sheet probes. The employed PIV setup allows a spatial resolution of 0.7 mm × 0.7mm and thus a similar resolution as the spatial discretization in the simulation. For the numerical part of the study, time-accurate simulations are conducted for the same operating conditions as during experiments. Additional simulations of the same configuration with smooth casing are conducted in order to estimate the effect of the CT on the flow. The examination of PIV measurements and corresponding simulations exposes complex vortical structures originating from the interaction of the rotor bow shock with the IGV trailing edge, CT, IGV wake and the tip leakage vortex. The associated induced velocities together with the general passage flow form a complex flow field with significantly altered blockage compared to a common flow field in the tip vicinity. Position and trajectory of the tip leakage vortex are deduced from interactions between tip leakage vortex and IGV wake / CT. The detailed comparison of the tip region of simulations with and without CT shows that the CT influences pressure rise and flow parameters in a wide radial range due to a radial redistribution of the flow. Correspondingly, a rotor with CT can achieve an increased total pressure rise compared to a rotor with smooth casing, with only minor effects on the efficiency.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

Sign in / Sign up

Export Citation Format

Share Document