Experimental Investigation of the Rotor-Stator Interactions Within a High-Speed, Multi-Stage, Axial Compressor: Part 2 — Modal Analysis of the Interactions

2004 ◽  
Author(s):  
David Arnaud ◽  
Xavier Ottavy ◽  
Andre´ Vouillarmet
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Axial Compressor ◽  
Rotating Speed ◽  
Spatial Harmonics ◽  
Multi Stage ◽  
Time Period ◽  
Original Measurement ◽  
Measured Flow ◽  
Almost All

The second part of this paper deals with the analysis of the 2D LDA measurements carried out within the high-speed multistage axial compressor CREATE. First the interactions correlations are quantified using the deterministic stresses introduced by Adamczyk. Secondly, a modal decomposition shows that the interactions are characterized by the presence of spatial harmonics (spinning lobes) given by a linear combination of the blades numbers. An original measurement of the rotating speed of the spinning lobes has been carried out allowing to identify almost all the spinning lobes in the first inter row region resulting from the R1-S1 interactions. For the first stage, where the influence of the downstream rows is low, the measured flow field is well reproduced by the model of Tyler and Sofrin. Spatial DFT of the flow field calculated for each time of the compressor time period show that there is a pulsation of the spatial harmonics with the period associated to the minimum elapsed time to recover the same relative positions of the rotor and stator rows.

Evaluation of a Flow Measurement Probe Influence on the Flow Field in High Speed Axial Compressors

2021 ◽  
Author(s):  
Ryosuke Seki ◽  
Satoshi Yamashita ◽  
Ryosuke Mito
Keyword(s):  
Flow Field ◽  
Approximation Method ◽  
High Speed ◽  
Static Pressure ◽  
Axial Compressor ◽  
Pressure Change ◽  
Operating Point ◽  
Blade Row ◽  
Probe Insertion ◽  
Probe Geometry

Abstract The aerodynamic effects of a probe for stage performance evaluation in a high-speed axial compressor are investigated. Regarding the probe measurement accuracy and its aerodynamic effects, the upstream/downstream effects on the probe and probe insertion effects are studied by using an unsteady computational fluid dynamics (CFD) analysis and by verifying in two types of multistage high-speed axial compressor measurements. The probe traverse measurements were conducted at the stator inlet and outlet in each case to evaluate blade row performance quantitatively and its flow field. In the past study, the simple approximation method was carried out which considered only the interference of the probe effect based on the reduction of the mass flow by the probe blockage for the compressor performance, but it did not agree well with the measured results. In order to correctly and quantitatively grasp the mechanism of the flow field when the probe is inserted, the unsteady calculation including the probe geometry was carried out in the present study. Unsteady calculation was performed with a probe inserted completely between the rotor and stator of a 4-stage axial compressor. Since the probe blockage and potential flow field, which mean the pressure change region induced by the probe, change the operating point of the upstream rotor and increase the work of the rotor. Compared the measurement result with probe to a kiel probe setting in the stator leading edge, the total pressure was increased about 2,000Pa at the probe tip. In addition, the developed wake by the probe interferes with the downstream stator row and locally changes the static pressure at the stator exit. To evaluate the probe insertion effect, unsteady calculations with probe at three different immersion heights at the stator downstream in an 8-stage axial compressor are performed. The static pressure value of the probe tip was increased about 3,000Pa in the hub region compared to tip region, this increase corresponds to the measurement trend. On the other hand, the measured wall static pressure showed that there is no drastic change in the radial direction. In addition, when the probe is inserted from the tip to hub region in the measurement, the blockage induced by the probe was increased. As a result, operating point of the stator was locally changed, and the rise of static pressure of the stator increased when the stator incidence changed. These typical results show that unsteady simulations including probe geometry can accurately evaluate the aerodynamic effects of probes in the high-speed axial compressor. Therefore, since the probe will pinpointed and strong affects the practically local flow field in all rotor upstream passage and stator downstream, as for the probe measurement, it is important to pay attention to design the probe diameter, the distance from the blade row, and its relative position to the downstream stator. From the above investigations, a newly simple approximation method which includes the effect of the pressure change evaluation by the probe is proposed, and it is verified in the 4-stage compressor case as an example. In this method, the effects of the distance between the rotor trailing edge (T.E.) and the probe are considered by the theory of the incompressible two-dimensional potential flow. The probe blockage decreases the mass flow rate and changes the operating point of the compressor. The verification results conducted in real compressor indicate that the correct blockage approximation enables designer to estimate aerodynamic effects of the probe correctly.

Characteristics of Stable Rotating Stall Cells in an Axial Compressor

2017 ◽  
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Axial Compressor ◽  
Field Measurements ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Stable Operation ◽  
Double Phase

Flow field measurements of a high-speed axial compressor are presented during pre-stall and post-stall conditions. The paper provides an analysis of measurements from a circumferential array of unsteady shroud static pressure sensors during stall cell development. At low-speed, the stall cell approached a stable size in approximately two rotor revolutions. At higher speeds, the stall cell developed within a short amount of time after stall inception, but then fluctuated in circumferential extent as the compressor transiently approached a stable post-stall operating point. The size of the stall cell was found to be related to the annulus average flow coefficient. A discussion of Phase-Locked Average (PLA) statistics on flow field measurements during stable operation is also included. In conditions where rotating stall is present, flow field measurements can be Double Phase-Locked Averaged (DPLA) using a once-per-revolution (1/Rev) pulse and the period of the stall cell. The DPLA method provides greater detail and understanding into the structure of the stall cell. DPLA data indicated that a stalled compressor annulus can be considered to contained three main regions: over-pressurized passages, stalled passages, and recovering passages. Within the over-pressured region, rotor passages exhibited increased blade loading and pressure ratio compared to pre-stall values.

scholarly journals Numerical simulation of the non-uniform flow in a full-annulus multi-stage axial compressor with the harmonic balance method

2020 ◽  
Vol 12 (3) ◽  
pp. 168781401989721 ◽  
Author(s):  
Haiou Sun ◽  
Meng Wang ◽  
Zhongyi Wang ◽  
Song Wang ◽  
Franco Magagnato
Keyword(s):  
Flow Field ◽  
Harmonic Balance ◽  
Axial Compressor ◽  
Harmonic Balance Method ◽  
Internal Flow ◽  
Uniform Flow ◽  
Experimental Results ◽  
Balance Method ◽  
Operating Characteristics ◽  
Multi Stage

To improve the understanding of unsteady flow in modern advanced axial compressor, unsteady simulations on full-annulus multi-stage axial compressor are carried out with the harmonic balance method. Since the internal flow in turbomachinery is naturally periodic, the harmonic balance method can be used to reduce the computational cost. In order to verify the accuracy of the harmonic balance method, the numerical results are first compared with the experimental results. The results show that the internal flow field and the operating characteristics of the multi-stage axial compressor obtained by the harmonic balance method coincide with the experimental results with the relative error in the range of 3%. Through the analysis of the internal flow field of the axial compressor, it can be found that the airflow in the clearance of adjacent blade rows gradually changes from axisymmetric to non-axisymmetric and then returns to almost completely axisymmetric distribution before the downstream blade inlet, with only a slight non-axisymmetric distribution, which can be ignored. Moreover, the slight non-axisymmetric distribution will continue to accumulate with the development of the flow and, finally, form a distinct circumferential non-uniform flow field in latter stages, which may be the reason why the traditional single-passage numerical method will cause certain errors in multi-stage axial compressor simulations.

Experimental Investigation of Aspiration in a Multi-Stage High-Speed Axial-Compressor

2016 ◽  
Author(s):  
Jan Siemann ◽  
Ingolf Krenz ◽  
Joerg R. Seume
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Reference Configuration ◽  
Corner Separation ◽  
Part Load ◽  
Total Pressure Ratio ◽  
Isentropic Efficiency

Reducing the fuel consumption is a main objective in the development of modern aircraft engines. Focusing on aircraft for mid-range flight distances, a significant potential to increase the engines overall efficiency at off-design conditions exists in reducing secondary flow losses of the compressor. For this purpose, Active Flow Control (AFC) by aspiration or injection of fluid at near wall regions is a promising approach. To experimentally investigate the aerodynamic benefits of AFC by aspiration, a 4½-stage high-speed axial-compressor at the Leibniz Universitaet Hannover was equipped with one AFC stator row. The numerical design of the AFC-stator showed significant hub corner separations in the first and second stator for the reference configuration at the 80% part-load speed-line near stall. Through the application of aspiration at the first stator, the numerical simulations predict the complete suppression of the corner separation not only in the first, but also in the second stator. This leads to a relative increase in overall isentropic efficiency of 1.47% and in overall total pressure ratio of 4.16% compared to the reference configuration. To put aspiration into practice, the high-speed axial-compressor was then equipped with a secondary air system and the AFC stator row in the first stage. All experiments with AFC were performed for a relative aspiration mass flow of less than 0.5% of the main flow. Besides the part-load speed-lines of 55% and 80%, the flow field downstream of each blade row was measured at the AFC design point. Experimental results are in good agreement with the numerical predictions. The use of AFC leads to an increase in operating range at the 55% part-load speed-line of at least 19%, whereas at the 80% part-load speed-line no extension of operating range occurs. Both speed-lines, however, do show a gain in total pressure ratio and isentropic efficiency for the AFC configuration compared to the reference configuration. Compared to the AFC design point, the isentropic efficiency ηis rises by 1.45%, whereas the total pressure ratio Πtot increases by 1.47%. The analysis of local flow field data shows that the hub corner separation in the first stator is reduced by aspiration, whereas in the second stator the hub corner separation slightly increases. The application of AFC in the first stage further changes the stage loading in all downstream stages. While the first and third stage become unloaded by application of AFC, the loading in terms of the De-Haller number increases in the second and especially in the fourth stage. Furthermore, in the reference as well as in the AFC configuration, the fourth stator performs significantly better than predicted by numerical results.

Numerical Simulation of the Flow Field in a High Speed Multistage Compressor: Study of the Time Discretization Sensitivity

2015 ◽  
Author(s):  
Johannes Schreiber ◽  
Xavier Ottavy ◽  
Ghislaine Ngo Boum ◽  
Stéphane Aubert ◽  
Frédéric Sicot
Keyword(s):  
Flow Field ◽  
High Speed ◽  
State Of The Art ◽  
Axial Compressor ◽  
Time Discretization ◽  
Test Rig ◽  
Unsteady Rans ◽  
Multistage Compressor ◽  
Temporal Periodicity ◽  
Specific Contribution

The following numerical investigations are performed in the frame of a research project that aims at a better understanding of the flow unsteadiness that develops in a multistage high-speed axial compressor. First, the paper presents a new version of the 3.5 stages high-speed axial compressor CREATE (Compresseur de Recherche pour l’Etude des effets Aérodynamiques et TEchnologiques), which has been designed by Snecma and is based at the LMFA (Laboratory for Fluid Mechanics and Acoustics) on a 2MW test rig. This paper is based on numerical results obtained with 3D steady and unsteady RANS computations using the CREATE configuration. The unsteady RANS simulations are carried out over the whole spatial and temporal periodicity of the compressor. The main numerical setup has been fixed according to the state of the art. Second, the effect of three different time discretizations on the flow field in CREATE is discussed. The global performance of the compressor is not significantly affected. However the change in the time discretization impacts the structure of the flow at specific locations. The main focus of this study lies on the transport of flow structures and the analysis of their interactions. A double modal decomposition method, which highlights the specific contribution of the interactions on the overall flow field, is applied for the study of the highly complex and unsteady flow field. It allows identifying which interactions are more sensitive to the change in the time discretization.

Experimental Investigation of the Rotor-Stator Interactions Within a High Speed, Multi-Stage, Axial Compressor: Part 1 — Experimental Facilities and Results

2004 ◽  
Author(s):  
David Arnaud ◽  
Xavier Ottavy ◽  
Andre´ Vouillarmet
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Measurement Accuracy ◽  
Axial Compressor ◽  
Frame Of Reference ◽  
Rotating Frame ◽  
Blade Height ◽  
Laser Anemometry ◽  
Multi Stage ◽  
Experimental Facilities

This paper relates to laser anemometry measurements (LDA) conducted in a high speed, three-stage, axial compressor. Particular attention has been paid to the estimation of the measurement accuracy. Three different synchronization procedures have been implemented in order to enhance the exactness of the location in the rotating frame for each situation. Small flat windows mainly provide the optical accesses. But, large curved glasses could also be used, the optical distortions resulting from the surface curvature being corrected with the help of an optical assembly developed for the L2F technique and extended to the LDA technique. Furthermore, in order to avoid interpolation processes when changing the frame of reference, the spatial and time discretizations have been defined in accordance with the numbers of rotor and stator blades. The presented measurements have been performed, at 50% blade height, in the first three inter row sections, the azimuthal exploration covering machine periodicity.

Flow Field Measurement in Multi-stage Axial Compressor Stator by Using Multi-hole Pneumatic Probes

2017 ◽  
Vol 34 (1) ◽  
Author(s):  
Wang Zhiqiang ◽  
Lu Bo ◽  
Zhang Chenkai ◽  
Hu Jun
Keyword(s):  
Flow Field ◽  
Field Measurement ◽  
Large Scale ◽  
Axial Compressor ◽  
Internal Flow ◽  
Field Measurements ◽  
Blade Passage ◽  
Multi Stage ◽  
Stator Blade ◽  
Flow Field Measurement

AbstractIn order to realize the stator’s internal flow field measurement of the multi-stage axial compressor, many different lengths of L-type five-hole probes and one four-hole probe have been designed. The detailed 3D (three-dimensional) flow fields in the stator blade passage of original and modified large scale compressors have been measured with the probes traversed by a probe traverse mechanism. The objective of the study is to assess the measurement method of adopting multi-hole pneumatic probes to achieve the flow field of stator vane passage. Results clearly demonstrate the flow field characteristics of stator blade passage in original and modified compressors. Furthermore, the reliability of adopted multi-hole pneumatic probes is validated. Therefore, it is proved that the probe traverse mechanism drives the L-type five-hole probe or other probe method can be applied to internal flow field measurements for the stator of large scale multi-stage compressors.

Simulation and Experimental Investigation on Micro Electrochemical Milling of Micro Pattern Structures with High-Speed Helix Electrode

2019 ◽  
Vol 12 (2) ◽  
pp. 146-157
Author(s):  
Huanghai Kong ◽  
Yong Liu ◽  
Kan Wang ◽  
Yong Jiang ◽  
Xiangming Zhu
Keyword(s):  
Flow Field ◽  
High Speed ◽  
High Efficiency ◽  
Surface Profile ◽  
Machining Efficiency ◽  
Rotating Speed ◽  
Pattern Structures ◽  
Micro Pattern ◽  
Electrochemical Milling ◽  
Profile Change

Background: It is always difficult to fabricate micro parts in complicated machines. As one of the most promising micro machining methods, micro electrochemical milling based on the principle of anode electrochemical dissolution is useful for the fabrication of micro structures in hard metal material with advantages irrespective of the material hardness and strength along with no residual stress or heat treatment being observed on the surface of the workpiece. Objective: The purpose of this paper is to propose a method of micro pattern structures machining by using high-speed helix electrode in micro electrochemical milling, and reveal the relationship of rotating speed of helix electrode and machining efficiency. Methods: This paper presents a micro electrochemical milling technique for fabricating micro pattern structures with high efficiency. Firstly, a mathematical model of gap electric field under the condition of ultra short pulse power supply is established, and the surface profile change of workpiece in micro electrochemical milling is simulated by COMSOL Multiphysics. Secondly, the gap flow field of the machining under the conditions of different rotating speed of helix electrode is analyzed by simulation. Finally, a set of experiments are carried out to discuss the influence of the rotating speed on maximum feed rate. Results: The surface profile change of workpiece in micro electrochemical milling is predicted by simulation. The graphs of gas-liquid distribution and velocity vector of the flow field in the machining are obtained. A series of micro pattern structures with a groove width of 150μm are machined successfully. Conclusion: By using high-speed helix electrode, the electrolyte circulation can be promoted and machining efficiency of micro electrochemical milling can be improved obviously. The experiment results demonstrate that the micro electrochemical milling with high-speed helix electrode is an efficient method to fabricate micro pattern structures. In this article, various patents have been discussed.

Sign in / Sign up

Export Citation Format

Share Document