Unsteady Numerical Research Into the Impact of Bleeding on Axial Compressor Performance

2010 ◽  
Author(s):  
Bin Zhao ◽  
Shaobin Li ◽  
Qiushi Li ◽  
Sheng Zhou
Keyword(s):  
Axial Compressor ◽  
Stability Margin ◽  
Moving Mesh ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Aero Engine ◽  
Compressor Performance ◽  
Numerical Research ◽  
Overall Performance ◽  
The Impact

The cooling gas of turbine components in aero-engine is extracted from the compressor. Its flow rate is related to the temperature before turbine. The percentage is usually about 3–5% and sometimes up to 25% of the main flow. Very few of the current studies in this field touched on the influence of air bleeding on compressor performance. This paper takes the single stage and low speed axial compressor as the research object, develops a time-accurate numerical method on the compressor overall performance by using the moving mesh to simulate the function of compressor throttle plug. Combined with experimental results, compressor flow field with and without air bleeding are compared and analyzed to study the impact of bleeding on compressor performance. The results show that if a bleeding design can ease the blockage generated by the tip leakage flow and the backflow near the trailing edge, the stall will be effectively postponed and the compressor stability margin will be expanded.

Numerical Research on Effects of Shroud Contraction on Tip Leakage Flow and Overall Performance of Axial Compressors

2017 ◽  
Author(s):  
Yufan Zhang ◽  
Jiabin Li ◽  
Lucheng Ji
Keyword(s):  
Great Influence ◽  
Axial Compressor ◽  
Detailed Comparison ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Compressors ◽  
Tip Leakage ◽  
Numerical Research ◽  
Overall Performance ◽  
Inclined Angle

In the design of an axial compressor, many designers take advantage of this technology and employ contracted shroud. What is its impact on tip leakage flow and overall performance of the axial compressor? What is its mechanism? In this paper, the NASA Rotor67 is taken as a research case, and parameterized study is conducted to investigate the effects of shrouds with different inclined angles. The inclined angles range from 0° to 13°. Based on the above described plan, numerical simulations are conducted to the original rotor67 and its modified versions with inclined shroud. To remove factors that might interfere the results, original Rotor 67 and all the blades with modified shroud should be compared to their optimal design status. Adjoint optimization is used to give the optimum blade corresponding to each shroud with different blade inclined angles. Then adjoint optimization was used again to give the optimum meridional flowpath for all the cases with different shroud inclined angles. This provides a powerful tool to evaluate the accuracy of the aforementioned prediction. A detailed comparison is made between the original flowpath and the optimized ones. Numerical results are analyzed in detail between original Rotor67 and its modified versions. The results show that the shroud inclined angle has an effect on the overall performance of the blade. It will also redistribute the velocity triangles and the chordwise distribution of aero load in the tip region. Hence it exerts great influence on the tip leakage flow field in the meantime. Shroud with suitable inclined angles can suppress the developing of leakage vortex , and the best-inclined angle for rotor 67 is found to be roughly 11°.

Prediction of Tip Leakage Vortex Dynamics in an Axial Compressor Cascade Using RANS Analyses

2020 ◽  
Author(s):  
Martina Ricci ◽  
Roberto Pacciani ◽  
Michele Marconcini ◽  
Andrea Arnone
Keyword(s):  
Vortex Dynamics ◽  
Eddy Viscosity ◽  
Axial Compressor ◽  
Viscosity Model ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Eddy Viscosity Model ◽  
The Impact

Abstract The tip leakage flow in turbine and compressor blade rows is responsible for a relevant fraction of the total loss. It contributes to unsteadiness, and have an important impact on the operability range of compressor stages. Experimental investigations and, more recently, scale-resolving CFD approaches have helped in clarifying the flow mechanism determining the dynamics of the tip leakage vortex. Due to their continuing fundamental role in design verifications, it is important to establish whether RANS/URANS approaches are able to reproduce the effects of such a flow feature, in order to correctly drive the design of the next generation of turbomachinery. Base studies are needed in order to accomplish this goal. In the present work the tip leakage flow in axial compressor rotor blade cascade have been studied. The cascade was tested experimentally in Virginia Tech Low Speed Cascade Wind Tunnel in both stationary and moving endwall configurations. Numerical analyses were performed using the TRAF code, a state-of-the-art in-house-developed 3D RANS/URANS flow solver. The impact of the numerical framework was investigated selecting different advection schemes including a central scheme with artificial dissipation and a high-resolution upwind strategy. In addition, two turbulence models have been used, the Wilcox linear k–ω model and a non-linear eddy viscosity model (Realizable Quadratic Eddy Viscosity Model), which accounts for turbulence anisotropy. The numerical results are scrutinized using the available measurements. A detailed discussion of the vortex evolution inside the blade passage and downstream of the blade trailing edge is presented in terms of streamwise velocity, streamwise vorticity, and turbulent kinetic energy contours. The purpose is to identify guidelines for obtaining the best representation of the vortex dynamics, with the methodologies usually employed in routine design iterations and, at the same time, evidence their weak aspects that need further modelling efforts.

Numerical investigation of tip clearance size effect on the performance and tip leakage flow in a dual-stage counter-rotating axial compressor

2017 ◽  
Vol 231 (3) ◽  
pp. 474-484 ◽  
Author(s):  
Xiaochen Mao ◽  
Bo Liu
Keyword(s):  
Size Effect ◽  
Axial Compressor ◽  
Size Variation ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Remarkable Effect ◽  
Tip Leakage ◽  
Dual Stage ◽  
The Impact

Based on a validation of the numerical methods with an experiment, numerical simulations are carried out to study the effect of tip clearance size on the performance and tip leakage flow in a dual-stage counter-rotating axial compressor. The predicted results showed that the variation of the tip clearance size in rotor2 has a more significant impact on the overall performance and stall margin of the compressor. In addition, the impact of the tip clearance size effect is mainly on the rotor with the tip clearance size variation. The variation of the tip clearance size in rotor2 almost has no influence on the performance of rotor1, while the performance of rotor2 is increased about 1.37% at near-stall point when the tip clearance size of rotor1 is increased to 1.0 mm from 0.5 mm. At peak efficiency condition, the tip clearance size variation in rotor1 has remarkable influence on the tip leakage vortex intensity, onset point and trajectory in rotor1, but has little influence on those in rotor2. However, the tip clearance size variation in rotor2 has remarkable effect on those in both rotors. Different tip clearance size combination schemes can impact the stall-free characteristic in the counter-rotating axial compressor.

Some effects of non-axisymmetric tip clearance layout on axial compressor aerodynamics

2021 ◽  
pp. 095765092110470
Author(s):  
Haohao Zhang ◽  
Haowan Zhuang ◽  
Jinfang Teng ◽  
Mingmin Zhu ◽  
Xiaoqing Qiang
Keyword(s):  
Transient Flow ◽  
Axial Compressor ◽  
Flow Fields ◽  
Tip Clearance ◽  
Inlet Guide Vane ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Tip Leakage ◽  
Overall Performance

A steady and unsteady numerical research is carried out to explore some effects of a specific non-axisymmetric tip clearance layout on the overall performance and stability of an axial compressor stage. For a 4-stage low-speed research compressor (LSRC) in Shanghai Jiao Tong University (SJTU), one-eighth annulus of the inlet guide vane and the first stage rotor was modeled for this study. After the validation for the uniform tip clearance case, a specific non-axisymmetric tip clearance layout is chosen from several random cases generated by the Gaussian Probabilistic Density Function method. Unsteady time-averaged results at the near stall condition show that the chosen non-axisymmetric layout can improve the isentropic efficiency by 1.3% and extend the stall margin by 4%. Detailed analyses on flow fields are carried out to interpret the performance improvement. Due to the circumferential layout of clearance sizes, the inlet mass flow and incidence are redistributed in both the radial and circumferential directions. It leads to blade loading and tip leakage flow varying with the tip clearance size. The quantification of blockage manifests that the blockage arising from the tip leakage flow is significantly alleviated in the non-axisymmetric layout, which leads to improvements in overall performance and stall margin. Transient flow fields at the rotor tip are also analyzed at the near stall condition. For the non-axisymmetric layout, low-momentum regions originating from larger clearance sizes oscillate and develop downstream in one blade passage period.

Effect of Axial Short Slot Casing Treatment and its Center Deviation on Stability of a Transonic Axial Flow Compressor

2020 ◽  
Author(s):  
Sha Zhang ◽  
Wuli Chu ◽  
Jibo Yang
Keyword(s):  
Boundary Layer ◽  
Axial Compressor ◽  
Subsequent Development ◽  
Stability Margin ◽  
Axial Position ◽  
Central Position ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Casing Treatment ◽  
Tip Leakage

Abstract In order to increase the stability margin of axial compressor with low efficiency losses, this paper studies the influence of axial short slot casing treatment and its axial position on compressor performance. A transonic axial compressor rotor, NASA rotor37, is taken as the research object, and the solid wall case and three axial slot casing treatments with different axial positions are studied by numerical simulation. The results show that the configuration with a center deviation of 0 (CT _C) has the best effect, with a margin improvement of 7.6% and an efficiency reduction of 0.09%; the configuration with an upstream positioned axial slot (CT_L) is the second, with a margin improvement of 5.4% and an efficiency reduction of 0.28%; the configuration with a downstream positioned axial slot (CT_T) is the worst, with a margin improvement of 3.6% and an efficiency reduction of 0.3%. A shift of the slot in downstream direction is not effective because it only affects the extent of boundary layer separation and has little effect on the development of the tip leakage flow. The upstream positioned axial slot with unsatisfactory effect affects the tip leakage flow trajectory and weakens the radial vortex at the blade tip, but it cannot affect the subsequent development of the leakage vortex. The short slot casing treatment in the central position effectively inhibits the development of the vortex. At the same time, it affects the development of the boundary layer to some extent and ensures the lower efficiency reduction while obtaining better stability margin.

Effect of the Axial Casing Groove Geometry on the Production and Distribution of Reynolds Stresses in the Tip Region of an Axial Compressor Rotor

2021 ◽  
Author(s):  
Subhra Shankha Koley ◽  
Ayush Saraswat ◽  
Huang Chen ◽  
Joseph Katz
Keyword(s):  
Shear Layer ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Secondary Flows ◽  
Axial Component ◽  
Tip Leakage Flow ◽  
Production Rates ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
The Impact

Abstract Stereo PIV measurements performed in a refractive index matched facility examine the effect of axial casing grooves (ACGs) geometry on the turbulence in the tip region of an axial compressor rotor. The ACGs delay the onset of stall by entraining the Tip Leakage Vortex (TLV), and by causing periodic changes to incidence angle as their outflow impinges on the rotor blade. To decouple these effects, measurements have been performed using a series of grooves having similar inlets, but different outflow directions. The performance and flow structure associated with three grooves, namely a semi-circular ACG, as well as U and S shaped grooves have been presented in several recent papers. This paper focuses on the impact of passage flow-groove interactions on the distribution, evolution, and production rates of turbulent kinetic energy (TKE) and all the Reynolds stress components. The analysis is performed at flow rates corresponding to pre-stall conditions and best efficiency point (BEP) of the untreated end wall, and for different blade orientations relative to the groove. Interactions of the tip flow with the ACGs modifies the magnitude and spatial distribution of the highly anisotropic and inhomogeneous turbulence in the passage. Owing to TLV entrainment into the grooves, at low flowrate, the ACGs actually reduce the turbulence in the passage compared to that in the smooth endwall. However, the geometry -dependent tip flow-groove interactions introduce new elevated turbulence centers. In all cases, the TKE is high in the: (i) TLV center, (ii) corner vortex generated as the backward tip leakage flow separates at the downstream end of the groove, and (iii) shear layer connecting the TLV to the rotor blade suction side tip. The location of peaks and the dominant components vary among grooves. For example, the axial component is dominant for the semicircular ACG, and its peak is located in the shear layer. The radial component is the dominant contributor for the U and S grooves, and it peaks inside the grooves at different locations. The circumferential component peaks in the TLV for the U and semicircular ACG, but inside the S groove. The shear layers generated as the flows jet out from the upstream ends of the grooves also bring varying elevated turbulence. At BEP, interactions of the TLV with secondary flows generated by the U and semi-circular grooves, for which the outflow is oriented in the negative circumferential direction, generate high turbulence levels, which extend deep into the passage. In contrast, the interactions associated with the S grooves are limited, resulting in a substantially lower turbulence level. Many of the various trends can be readily explained by examining the corresponding spatial distributions of the turbulence production rates. Such understanding elucidates the different mechanisms involved and provides a unique database for modelling turbulence in the passage.

Study of the Standard k-ε Model for Tip Leakage Flow in an Axial Compressor Rotor

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Yanfei Gao ◽  
Yangwei Liu ◽  
Luyang Zhong ◽  
Jiexuan Hou ◽  
Lipeng Lu
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Axial Compressor ◽  
Leakage Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor

AbstractThe standard k-ε model (SKE) and the Reynolds stress model (RSM) are employed to predict the tip leakage flow (TLF) in a low-speed large-scale axial compressor rotor. Then, a new research method is adopted to “freeze” the turbulent kinetic energy and dissipation rate of the flow field derived from the RSM, and obtain the turbulent viscosity using the Boussinesq hypothesis. The Reynolds stresses and mean flow field computed on the basis of the frozen viscosity are compared with the results of the SKE and the RSM. The flow field in the tip region based on the frozen viscosity is more similar to the results of the RSM than those of the SKE, although certain differences can be observed. This finding indicates that the non-equilibrium turbulence transport nature plays an important role in predicting the TLF, as well as the turbulence anisotropy.

Compressor Performance and Operability in Swirl Distortion

2010 ◽  
Author(s):  
Yogi Sheoran ◽  
Bruce Bouldin ◽  
P. Murali Krishnan
Keyword(s):  
Gas Turbine ◽  
Complex Geometry ◽  
Full Range ◽  
Axial Compressor ◽  
Cfd Model ◽  
Generator System ◽  
Sliding Mesh ◽  
Wide Range ◽  
Compressor Performance ◽  
The Impact

Inlet swirl distortion has become a major area of concern in the gas turbine engine community. Gas turbine engines are increasingly installed with more complicated and tortuous inlet systems, like those found on embedded installations on Unmanned Aerial Vehicles (UAVs). These inlet systems can produce complex swirl patterns in addition to total pressure distortion. The effect of swirl distortion on engine or compressor performance and operability must be evaluated. The gas turbine community is developing methodologies to measure and characterize swirl distortion. There is a strong need to develop a database containing the impact of a range of swirl distortion patterns on a compressor performance and operability. A recent paper presented by the authors described a versatile swirl distortion generator system that produced a wide range of swirl distortion patterns of a prescribed strength, including bulk swirl, twin swirl and offset swirl. The design of these swirl generators greatly improved the understanding of the formation of swirl. The next step of this process is to understand the effect of swirl on compressor performance. A previously published paper by the authors used parallel compressor analysis to map out different speed lines that resulted from different types of swirl distortion. For the study described in this paper, a computational fluid dynamics (CFD) model is used to couple upstream swirl generator geometry to a single stage of an axial compressor in order to generate a family of compressor speed lines. The complex geometry of the analyzed swirl generators requires that the full 360° compressor be included in the CFD model. A full compressor can be modeled several ways in a CFD analysis, including sliding mesh and frozen rotor techniques. For a single operating condition, a study was conducted using both of these techniques to determine the best method given the large size of the CFD model and the number of data points that needed to be run to generate speed lines. This study compared the CFD results for the undistorted compressor at 100% speed to comparable test data. Results of this study indicated that the frozen rotor approach provided just as accurate results as the sliding mesh but with a greatly reduced cycle time. Once the CFD approach was calibrated, the same techniques were used to determine compressor performance and operability when a full range of swirl distortion patterns were generated by upstream swirl generators. The compressor speed line shift due to co-rotating and counter-rotating bulk swirl resulted in a predictable performance and operability shift. Of particular importance is the compressor performance and operability resulting from an exposure to a set of paired swirl distortions. The CFD generated speed lines follow similar trends to those produced by parallel compressor analysis.

Effect of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1—Framework of Technical Approach and Wake–Stator Blade Interactions

1999 ◽  
Vol 121 (3) ◽  
pp. 377-386 ◽  
Author(s):  
T. V. Valkov ◽  
C. S. Tan
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Tip Vortex ◽  
Technical Approach ◽  
Tip Vortices ◽  
Tip Leakage ◽  
Unsteady Interaction ◽  
Flow Approximation ◽  
Stator Blade ◽  
The Impact

In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stators with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-averaged performance of the stator. Detailed interrogation of the computed flow field showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically, there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated nontransitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.

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