Aerodynamic analysis of nonuniform trailing edge blowing

2018 ◽  
Vol 91 (1) ◽  
pp. 134-144
Author(s):  
Dong Liang ◽  
Wenjie Wang ◽  
Peter J. Thomas
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Base Flow ◽  
Trailing Edge ◽  
Axial Thrust ◽  
Content Type ◽  
Low Speed ◽  
Rotor Stator Interaction ◽  
Aerodynamic Parameters ◽  
Total Pressure Ratio

Purpose Numerical and experimental results for different oncoming base-flow conditions indicate that nonuniform trailing edge blowing (NTEB) can expand the performance range of compressors and reduce the thrust on the rotor, while the efficiency of the compressor can be improved by more than 2 per cent. Design/methodology/approach Relevant aerodynamic parameters, such as total pressure, ratio of efficiency and axial thrust, are calculated and analyzed under conditions with and without NTEB. Measurements are performed downstream of two adjacent stator blades, at seven equidistantly spaced reference locations. The experimental measurement of the interstage flow field used a dynamic four-hole probe with phase lock technique. Findings An axial low-speed single-stage compressor was established with flow field measurement system and nonuniform blowing system. NTEB was studied by means of numerical simulations and experiments, and it is found that the efficiency of the tested compressor can be improved by more than 2 per cent. Originality/value Unlike most of the previous research studies which mainly focused on the rotor/stator interaction and trailing edge uniform blowing, the research results summarized in the current paper on the stator/rotor interaction used inlet guide vanes for steady and unsteady calculations. An active control of the interstage flow field in a low-speed compressor was used to widen the working range and improve the performance of the compressor.

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.

Flow Analysis of a High Flowrate Centrifugal Compressor Stage and Comparison With Test Rig Data

2016 ◽  
Author(s):  
Anton Weber ◽  
Christian Morsbach ◽  
Edmund Kügeler ◽  
Christoph Rube ◽  
Matthias Wedeking
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Test Rig ◽  
Total Pressure Ratio

The flow field inside a single-stage centrifugal compressor characterized by a high flowrate of Φ = 0.15 and a design total pressure ratio of approximately 1.4 is analysed numerically. The stage geometry consists of a radially oriented inlet duct with uniform inflow without swirl, a 90 deg inlet bend in front of the impeller, the shrouded impeller itself followed by a large radial vaneless diffuser, a 180 deg U-turn, a radially oriented turning vane, a subsequent 90 deg bend, and as the last item a long axial exit duct. The impeller blades have large fillets at hub and tip and thick blunt trailing edges. Due to the rotating shroud, a labyrinth seal is placed above the impeller with 5 seal tips. The complete leakage region is also included in the CFD analysis. The blade numbers for the impeller and vane are 15 and 14, respectively. The test rig has recently been built at the Institute of Propulsion and Turbomachinery at RWTH Aachen University (Germany). The first part of the CFD work presented was carried out before the first experimental data were available. Using the k-ω turbulence model of Wilcox (1988), a number of principal steady RANS calculations were performed to investigate the following: Impact of near wall grid resolution and turbulence model wall boundary condition treatment, impact of impeller fillets, and the influence of leakage flow. This part is completed by a comparison of steady RANS simulations with the time-mean results of unsteady RANS analyses of one blade passage. For the calculations presented in the second part, experimental data are available at the inflow and outflow planes. At these planes overall mean values were deduced. Additionally, 3- and 5-hole probe data are available at spanwise traverse planes located at the zenith of the U-turn and in the exit plane. For part two a finer grid with y+ values of approximately unity for all solid walls was used. In addition to the Wilcox k-ω model and the Menter SST k-ω model, two higher level turbulence models — the explicit algebraic Reynolds stress model Hellsten EARSM k-ω and the differential Reynolds stress model SSG/LRR-ω — have been tested and compared with the experiments. The agreement in terms of overall performance (total pressure ratio, isentropic efficiency) is satisfactory for all turbulence models used, but there are some differences: the k-ω model is shown to be the most stable one towards stall. On the other hand, it is shown that details of the flow field in terms of the two spanwise traverses can be better represented by the more advanced turbulence models. All CFD simulations have been performed at 100% shaft speed.

Flow Field Structures of the Impeller Backside Cavity and Its Influences on the Centrifugal Compressor

2009 ◽  
Author(s):  
Zhigang Sun ◽  
Chunqing Tan ◽  
Dongyang Zhang
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Leakage Flow ◽  
Coupled Flow ◽  
Axial Thrust ◽  
Aerodynamic Performances ◽  
Shaft Power

The impeller backside cavity is one of the unique features of the centrifugal compressors, it can affect the aerodynamic performances of a centrifugal compressor in many ways. This paper presents the researches on the coupled flow fields between a centrifugal compressor main flow passage and its impeller backside cavity. The flow field structures and features of the impeller backside cavity are presented for different leakage flow patterns, and its influences on the flow field details, axial thrust, shaft power, pressure ratio and efficiency of the centrifugal compressor have been studied. Some general conclusions are drawn for different centrifugal compressor operating conditions and impeller backside cavity leakage flow patterns.

Experimental and numerical study of mixing characteristics of a rectangular lobed mixer in supersonic flow

2015 ◽  
Vol 119 (1216) ◽  
pp. 701-725 ◽  
Author(s):  
J.-H. Feng ◽  
C.-B. Shen ◽  
Q.-C. Wang ◽  
J. Lei
Keyword(s):  
Total Pressure ◽  
Large Scale ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Interfacial Area ◽  
Small Scale ◽  
Trailing Edge ◽  
Turbulence Structures ◽  
Scale Turbulence ◽  
Total Pressure Ratio

AbstractA combined experimental and computational study on a rectangular lobed mixer is performed. A series of simulations based on a steady Reynolds-averaged Navier-Stokes Simulation (RANS) are conducted to analyse the mixing mechanisms of large-scale streamwise structure shed by the trailing edge of lobed mixer, with emphasis being placed on the effect of turbulence modeling and inflow conditions. The simulations are validated in respect of velocity and scalar distribution against the data obtained through Particle Image Velocimetry (PIV) and Nanoparticle-based Planar Laser Scattering (NPLS) technique. The computational results predicted by the SSTk–ω turbulence model show better agreement with the experimental data. But the small-scale turbulence structures are not captured accurately by these turbulence models. The convoluted shear layer shed from trailing edge is stretched and rotated by the large-scale streamwise vortices, forming an unstable ‘pinching-off’ structure, which increases the interfacial area. And at the interface of two streams, a large number of small-scale turbulence structures are formed, which contribute a lot to the mixing enhancement along with the increased interfacial area. The streamwise vorticity decays more rapidly with the decrease of velocity ratio and total pressure ratio of two streams. The scalar thickness which reflects the mixing rate of two streams increases with the decreasing velocity ratio and total pressure ratio.

An Investigation of the IGV/Rotor Interaction in a Low Speed Axial Compressor Using DPIV

2006 ◽  
Author(s):  
Zhiqiang Gong ◽  
Zhiping Li ◽  
Maoyi Li ◽  
Yajun Lu
Keyword(s):  
Flow Field ◽  
Rotor Blade ◽  
Flow Instability ◽  
Dynamic Pressure ◽  
Axial Compressor ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Low Speed ◽  
Wide Range ◽  
Rotor Stator Interaction

IGV/rotor interaction phenomenon in axial compressors is important, because different matching states of IGV and rotor can result in significant differences in performance of the compressors. An experimental investigation of IGV/rotor interaction is performed on a one stage low speed axial compressor. The performance of the compressor is measured with the number of IGV varied within a wide range. Different IGV results in very different performance of the compressor, and the performance does not change with the number of IGV monotonously. Flow field around a rotor blade is measured using 2D Digital Particle Image Velocimetry (DPIV) and dynamic pressure probes, without IGV and with the IGV which brings the largest stall margin to the compressor. Comparison of flow fields reveals that the IGV wakes change the flow field around the rotor blade significantly. The wake of the rotor blade is weakened and its structure is changed. The rotor exit total pressure is elevated throughout the entire span. The tip leakage flow is suppressed, so relevant blockage is reduced and consequently the stable operating range of the compressor is extended. The relatively high turbulence intensity and periodic changes in flow velocity and direction brought by IGV wakes to the rotor may account for some of the observed changes in the flow field structure and the compressor performance. The flow instability and receptivity theory must be included to explain all the experimental results, and to utilize the rotor/stator interaction phenomena during the compressors design process.

The Experiment Research on the Performance of Low Speed Axial-Compressor by External Acoustic Excitation

2004 ◽  
Author(s):  
Zhi-Ping Li ◽  
Zhi-Qiang Gong ◽  
Yan Liu ◽  
Ya-Jun Lu
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Pressure Ratio ◽  
Excitation Frequency ◽  
Axial Compressor ◽  
Excitation Amplitude ◽  
Separated Flows ◽  
Stall Margin ◽  
Low Speed ◽  
Acoustic Excitations

This paper investigates the control of large-scale separated flows inside a low-speed axial-compressor by using external acoustic excitations. Experiment studies on the characteristics of flow field and the performance of compressors under external unsteady acoustic excitations are carried out in a low speed axial-compressor. The results indicate that the excitation frequency and excitation amplitude are of key importance for controlling large-scale separated flows. When the unsteady excitation is of the most effective frequency with proper amplitude, the large-scale separated flow is controlled effectively and the flow field becomes more regular near the compressor’s stall margin. At the same time, the performances of the compressor are enhanced: the efficiency is increased by about 1∼2%, the pressure ratio is increased by 2∼3% and the stall margin of the compressor is broadened remarkably too.

Numerical Investigations on Aerodynamic Design Criteria for Low Speed Mixed Flow Compressor

2021 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Cone Angle ◽  
Tip Clearance ◽  
Working Fluid ◽  
Mixed Flow ◽  
Low Speed ◽  
Flow Compressor

Abstract A surge in the small jet engine market due to aero-propulsion purposes generates a requirement to develop compact and robust high-performance compressors. Mixed flow compressors can provide a comparatively higher pressure ratio compared to axial compressors and have less frontal area than centrifugal compressors. Rapid progress in manufacturing and computational capabilities has resulted in the successful design of mixed flow compressors in recent decades. In the present study, the mixed flow compressor was designed to operate at 3,000 rpm with a small total-to-total pressure ratio of 1.03 and a mass flow rate = 1.98 kg/s to carry at low-speed testing for university-level research. Meanline design for the compressor with air as working fluid was done. The blade geometry was developed using commercial Ansys® Bladegen module. The flow domain mesh was generated by the TurboGrid module. Ansys CFX was used as a solver and post-processing tool for the present numerical study. The present work describes the detailed design procedure, overall performance, and flow field features of a low-speed mixed-flow compressor with the special requirement of axial flow exit. The parametric analysis was carried out on splitter blade placement, wrap angle (10°, 20°, 30°, and 50°), and exit cone angle (30°, 40°, 50°, 60°, and 65°), at constant tip clearance and keeping the other parameters constant to observe their effect on performance and flow structure. The use of splitter blades smoothen the flow structure along both stream-wise and span-wise direction, which minimizes flow the separation issue and thereby helping in extending the overall operating range. Comparing the flow field characteristic and performance of each parametric variable, the optimum range of design values is exhibited. The numerical observation and analysis done on parametric variations in this paper can be used for the design of such a future low-speed mixed flow compressor for different performance expectations and installation requirements.

Single Passage Detached Eddy Simulation of a Centrifugal Compressor Stage Using the Time Transformation Method

2015 ◽  
Author(s):  
Jason A. Bourgeois ◽  
Jason C. Nichols ◽  
Guilherme H. Watson ◽  
Robert J. Martinuzzi
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Compressor Stage ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Single Passage ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Total Pressure Ratio

A subsonic rear stage centrifugal compressor (designed as the last compressor stage of an aero-engine following a multi-stage axial compressor) was simulated as a single passage using Detached Eddy Simulation (DES) and circumferential time-inclination to enforce periodic boundary conditions according to the machine rotor-stator pitch ratio. The transient averaged statistics obtained with DES are compared to those of a standard steady mixing plane SST RANS simulation, an unsteady circumferential time-inclination SST URANS simulation and two-component non-intrusive Laser Doppler Velocimetry (LDV) measurements conducted in a centrifugal compressor test rig. The LDV and DES were carried out at the design point of the compressor. Significant discrepancies were found particularly in the unloading at the trailing edge of the impeller and the balancing of the diffusion throughout the stage, however the overall stage performance predictions were strikingly similar between the various turbulence modelling methods indicating that they are not particularly sensitive to the observed aerodynamic differences. The discrepancies observed do affect the ratio of loading between the impeller and diffuser, and could become exaggerated particularly at off-design conditions when components are not as well matched. At design, the DES showed a 1.6% lower total-to-total pressure ratio in the impeller compared to RANS (1.4% compared to URANS), and 0.9% lower in stage total-to-total pressure ratio (0.2% compared to URANS). Trailing edge base pressure distributions show a larger deficit in the RANS wake in comparison to the DES, and pressure distributions show strong blade-to-blade variations in the steady RANS results in the near-trailing edge region, whereas the averaged DES results show a much faster diffusion of the blade-to-blade and spanwise gradients which was found to be in agreement with LDV velocity field measurements. The higher diffusion in the DES is due to higher Reynolds stresses predicted in this area compared to standard RANS.

scholarly journals Observations of the Growth and Decay of Stall Cells during Stall and Surge in an Axial Compressor

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Leading Edge ◽  
Cell Development ◽  
Rotating Stall ◽  
Trailing Edge ◽  
Stall Inception ◽  
Compressor Rotor

This research investigated unsteady events such as stall inception, stall-cell development, and surge. Stall is characterized by a decrease in overall pressure rise and nonaxisymmetric throughflow. Compressor stall can lead to surge which is characterized by quasi-axisymmetric fluctuations in mass flow and pressure. Unsteady measurements of the flow field around the compressor rotor are examined. During the stall inception process, initial disturbances were found within the rotor passage near the tip region. As the stall cell develops, blade lift and pressure ratio decrease within the stall cell and increase ahead of the stall cell. The stall inception event, stall-cell development, and stall recovery event were found to be nearly identical for stable rotating stall and surge cases. As the stall cell grows, the leading edge of the cell will rotate at a higher rate than the trailing edge in the rotor frame. The opposite occurs during stall recovery. The trailing edge of the stall cell will rotate at the approximate speed as the fully developed stall cell, while the leading edge decreases in rotational speed in the rotor frame.

scholarly journals Experimental and Numerical Analysis of the Impeller Backside Cavity in a Centrifugal Compressor for CAES

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 420
Author(s):  
Zhihua Lin ◽  
Zhitao Zuo ◽  
Wei Li ◽  
Jianting Sun ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Axial Thrust ◽  
Rotating Speed ◽  
Aerodynamic Performances ◽  
Shaft Power ◽  
Aerodynamic Parameters ◽  
Coupling Characteristics

Relying on a closed test rig of a high-power intercooling centrifugal compressor for compressed air energy storage (CAES), this study measured the static pressure and static temperature at different radii on the static wall of the impeller backside cavity (IBC) under variable rotating speeds. Simultaneously, the coupled computations of all mainstream domains with IBC or not were used for comparative analysis of the aerodynamic performances of the compressor and the internal flow field in IBC. The results show that IBC has a significant impact on coupling characteristics including pressure ratio, efficiency, torque, shaft power, and axial thrust of the centrifugal compressor. The gradients of radial static pressure and static temperature in IBC both increase with the decrease of mainstream flow or the increase of rotating speed, whose distributions are different under variable rotating speeds due to the change of the aerodynamic parameters of mainstream.

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