Details of Shrouded Stator HUB Cavity Flow in a Multi-Stage Axial Compressor Part 2: Leakage Flow Characteristics in Stator Wells

Present Part ◽

Compressor Performance ◽

The Impact ◽

Shed Light ◽

Abstract In the first part of the paper, the influence of the hub leakage flow on compressor performance and its interactions with the primary flow were investigated. While the impact of hub leakage flow on the primary passage is readily available in the open literature, details inside the cavity geometry are scarce due to the difficulties in instrumenting that region for an experiment or modeling the full cavity geometry. To shed light on this topic, the flow physics in the stator cavity inlet and outlet wells were investigated in the present part of the paper to understand the flow path of the leakage fluid and windage heating within the cavity using a coupled CFD model with inclusion of the stator cavity wells for the Purdue 3-Stage (P3S) Axial Compressor, which is representative of the rear stages of a high-pressure-compressor in core engines.

Details of Shrouded Stator Hub Cavity Flow in a Multi-Stage Axial Compressor Part 2: Leakage Flow Characteristics in Stator Wells

10.1115/gt2021-60115 ◽

2021 ◽

Author(s):

Nitya Kamdar ◽

Fangyuan Lou ◽

Nicole L. Key

Keyword(s):

Flow Characteristics ◽

Axial Compressor ◽

Cavity Flow ◽

Flow Path ◽

Circumferential Velocity ◽

Leakage Flow ◽

Labyrinth Seals ◽

Multi Stage ◽

Abstract The flow in shrouded stator cavities can be quite complex with axial, radial, and circumferential variations. As the leakage flow recirculates and is re-injected into the main flow path upstream of the stator, it deteriorates the near-hub flow field and, thus, degrades the overall aerodynamic performance of the compressor. In addition, the windage heating in the cavity can raise thermal-mechanical concerns. Fully understanding the details of the shrouded-hub cavity flow in a multi-stage environment can enable better hub cavity designs. In the first part of the paper, the influence of the hub leakage flow on compressor performance and its interactions with the primary flow were investigated. While the impact of hub leakage flow on the primary passage is readily available in the open literature, details inside the cavity geometry are scarce due to the difficulties in instrumenting that region for an experiment or modeling the full cavity geometry. To shed light on this topic, the flow physics in the stator cavity inlet and outlet wells are investigated in the present paper using a coupled CFD model with inclusion of the stator cavity wells for the Purdue 3-Stage (P3S) Axial Compressor, which is representative of the rear stages of a high-pressure-compressor in core engines. At the inlet cavity, the presence of at least one pair of vortices influences the trajectory of the cavity leakage flow. The amount of leakage flow also determines the size of the vortical structures, with larger clearances creating a smaller vortex and vice versa. After passing through the labyrinth seals, the leakage flow travels along the stator landing first and then transitions to the rotor drum. In general, a flow path closer to the rotor drum achieves higher circumferential velocity but also exhibits significant temperature rise. A rise in circumferential velocity directly corresponds to a rise in temperature. In addition, the windage heating increases with increasing seal clearance. Furthermore, the inlet well contributes the most to overall windage, nearly 50% of the total windage heating, while the labyrinth seals and outlet well account for very little.

A Navier-Stokes Analysis of the Effect of Tip Clearance on Compressor Stall Margin

Volume 1: Turbomachinery ◽

10.1115/95-gt-190 ◽

1995 ◽

Cited By ~ 2

Author(s):

Robert P. Dring ◽

William D. Sprout ◽

Harris D. Weingold

Keyword(s):

Three Dimensional ◽

Axial Compressor ◽

Tip Clearance ◽

Navier Stokes ◽

Stall Margin ◽

Multi Stage ◽

Practical Tool ◽

The Impact ◽

A three-dimensional Navier-Stokes calculation was used to analyze the impact of rotor tip clearance on the stall margin of a multi-stage axial compressor. This paper presents a summary of: (1) a study of the sensitivity of the results to grid refinement, (2) an assessment of the calculation’s ability to predict stall margin when the stalling row was the first rotor in a multi-stage rig environment, (3) an analysis of the impact of including the effects of the downstream stator through body force effects on the upstream rotor, and (4) the ability of the calculation to predict the impact of tip clearance on stall margin through a calculation of the rear seven airfoil rows of an eleven stage high pressure compressor rig. The result of these studies was that a practical tool is available which can predict stall margin, and the impact of tip clearance, with reasonable accuracy.

Details of Shrouded Stator Hub Cavity Flow in a Multi-Stage Axial Compressor Part 1: Interactions With the Primary Flow

10.1115/gt2021-60103 ◽

2021 ◽

Author(s):

Nitya Kamdar ◽

Fangyuan Lou ◽

Nicole L. Key

Keyword(s):

Axial Compressor ◽

Cavity Flow ◽

Leakage Flow ◽

Clearance Ratio ◽

Primary Flow ◽

Flow Parameters ◽

Multi Stage ◽

Flow Interactions ◽

Compressor Performance ◽

Abstract The flow in shrouded stator cavities can be quite complex with axial, radial, and circumferential variations. As the leakage flow recirculates and is re-injected into the main flow path upstream of the stator, it deteriorates the near-hub flow field and, thus, degrades the overall aerodynamic performance of the compressor. In addition, the windage heating in the cavity can raise thermal-mechanical concerns. Fully understanding the details of the shrouded-hub cavity flow in a multi-stage environment can enable better hub cavity designs. Since the majority of the open literature presents limited details about the structure of compressor cavity flows in the stator wells and how the cavity wells affect the leakage flow, there is a lack of wholistic knowledge of how these flow parameters are interdependent. To shed light on this topic, a coupled CFD model with inclusion of the stator cavity wells for the Purdue 3-Stage (P3S) Axial Compressor Research Facility using the PAX100 configuration was developed and validated against experimental data. Such a model not only quantifies the impact of cavity leakage flow on compressor performance, but it also provides the capability to investigate the flow structure details including the path of the fluid into and out of the cavity. With the model in place, in this part 1 paper, the influence of the hub leakage flow on compressor performance and its interactions with the primary flow were investigated by varying the clearance ratio of a single stator. The understanding of the primary-hub-leakage flow interactions can offer insights leading to better designs of hub cavities.

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

The Impact of Bleeding on Compressor Stator Corner Separation

10.1115/ajk2011-22001 ◽

2011 ◽

Cited By ~ 2

Author(s):

Bin Zhao ◽

Shaobin Li ◽

Qiushi Li ◽

Sheng Zhou

Keyword(s):

Radial Flow ◽

Single Stage ◽

Corner Separation ◽

Transonic Compressor ◽

Compressor Performance ◽

The Impact ◽

Large Flow ◽

Compressor Efficiency ◽

Bleed air from the high pressure compressor has taken up 3–5% in the air system. However, there are not many studies on the compressor performance after bleeding. By analyzing a low-speed single-stage compressor and a transonic single-stage compressor, this paper presents several plans with different bleeding rates on the casing near stator corner, in order to study the influence of bleeding rates on the compressor stator corner separation. The results showed that for the stators of subsonic compressor with large flow separation in the corner, there is an optimum value in the stator casing bleed air amount. The flow field is better at resisting the radial flow caused by bleed air in the transonic compressor stator. The more the bleeding rates of the stator, the more the compressor efficiency improves.

Numerical Simulation of Particulates in Multi-Stage Axial Compressors

Volume 2A: Turbomachinery ◽

10.1115/gt2016-57917 ◽

2016 ◽

Cited By ~ 1

Author(s):

Swati Saxena ◽

Giridhar Jothiprasad ◽

Corey Bourassa ◽

Byron Pritchard

Keyword(s):

High Pressure ◽

Axial Compressor ◽

Airborne Particulate Matter ◽

Spherical Particles ◽

Qualitative Comparison ◽

Multi Stage ◽

Sand Erosion ◽

Multi Phase ◽

Aircraft engines ingest airborne particulate matter, such as sand, dirt, and volcanic ash, into their core. The ingested particulate is transported by the secondary flow circuits via compressor bleeds to the high pressure turbine and may deposit resulting in turbine fouling and loss of cooling effectiveness. Prior publications focused on particulate deposition and sand erosion patterns in a single stage of a compressor or turbine. The current work addresses the migration of ingested particulate through the high pressure compressor and bleed systems. This paper describes a 3D CFD methodology for tracking particles along a multi-stage axial compressor and presents particulate ingestion analysis for a high pressure compressor section. The commercial CFD multi-phase solver ANSYS CFX R has been used for flow and particulate simulations. Particle diameters of 20, 40, and 60 microns are analyzed. Particle trajectories and radial particulate profiles are compared for these particle diameters. The analysis demonstrates how the compressor centrifuges the particles radially towards the compressor case as they travel through the compressor; the larger diameter particles being more significantly affected. Non-spherical particles experience more drag as compared to spherical particles and hence a qualitative comparison between spherical and non-spherical particles is shown.

An Experimental Investigation of a Tandem Stator Flow Characteristic in a Low Speed Axial Research Compressor

Volume 2A: Turbomachinery ◽

10.1115/gt2014-26104 ◽

2014 ◽

Cited By ~ 3

Author(s):

Alrik Tesch ◽

Martin Lange ◽

Konrad Vogeler ◽

Jens Ortmanns ◽

Erik Johann ◽

...

Keyword(s):

Swirling Flow ◽

Guide Vane ◽

Axial Compressor ◽

Low Speed ◽

Oil Flow ◽

Compressor Performance ◽

Operating Points ◽

Insight Into ◽

A major goal in axial compressor development is to increase the efficiency and to reduce the weight of the module. In order to do so the power density has to be increased by raising the work per stage. Higher capability to do work can be achieved by increasing the circumferential velocity component of the fluid. Tandem stators might offer the ability to turn high swirling flow with lower losses compared to a single blade stator. In terms of higher aerodynamic loading the use of tandem vanes can be a key feature to allow the design of highly efficient and compact compressor modules. This paper presents the design and experimental validation of a single stage low speed axial compressor with a tandem outlet guide vane, representative for a modern jet engine high pressure compressor. Additionally to the overall compressor performance the 3D flow field of the tandem stator has been measured with a five hole probe at different operating points. The results will be discussed in comparison with numerical results. Furthermore, oil flow pictures are used to get a deeper insight into flow conditions inside the vane passage and to validate the numerically predicted secondary flow structures.

Investigation into Noise Frequency Spectrum Characteristics Corresponding to Blade Nonsynchronous Vibration in Multi-Stage Axial Compressor

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.2-3.870 ◽

2011 ◽

Vol 2-3 ◽

pp. 870-875

Author(s):

Yun Dong Sha ◽

Feng Tong Zhao ◽

Jia Han

Keyword(s):

Unsteady Flow ◽

Rotor Blade ◽

Axial Compressor ◽

Sound Field ◽

High Amplitude ◽

Flow Phenomenon ◽

Multi Stage ◽

Rotating Instability ◽

Unsteady flow phenomenon occurs in a multi-stage axial compressor. The unsteady flow not only has significant influence on the performance of compressor and the stability of flow, but also can be an excitation source inducing Nonsynchronous vibration (NSV) of rotor blade. NSV is an aeroelastic phenomenon where the rotor blades vibrate at nonintegral multiples of the shaft rotational frequencies in operating regimes where classical ﬂutter is not known to occur. Recently, more and more scholars pay attention to Rotating instabilities (RIs) as one of the unsteady flow phenomenon. RIs have been observed in axial ﬂow fans and centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This research aims at revealing the relationships among the unsteady flow behaviors, characteristics of inner sound field and propagation, the vibration of rotor blade in multi-stage axial compressor. The noise in compressor and the vibration of rotor blade have been measured on a high pressure compressor rig testing. The transducer system is connected to the interior casing wall through the acoustic waveguide pipes. The noise is measured by 1/4 inch condenser microphones in different operating of the compressor. The time-domain wave of noise acquired at different work status of the compressor is transformed into frequency spectrum by Fast Fourier Transform (FFT) to investigate characteristics of sound field in multi-stage axial compressor. And the emphasis is focused on the frequency characteristics of the noise corresponding to blade nonsynchronous vibration. It is found that the vibration amplitude of the rotor blade suddenly increases in a pre-arranged structure adjustment and specific rotating speed, and noise signal with special frequency structures appears simultaneously. High amplitude levels of blade vibration have occurred on the first rotor of a multi-stage high pressure compressor. The frequencies are not in resonance with harmonics of the rotor speed. The frequency analysis show that the noise has a special frequency structures with combination of the appeared characteristic frequency and the blade pass frequency of rotor blade (BPF). Because the similarities between the frequency combination and the specific frequency structure of the fluctuating pressure when the rotating instability (RI) appears in the axial compressor have been identified, the acting mechanism of rotating instability may exist in this compressor, i.e. the vibrational excitation to the rotor blade may be aerodynamically caused and associated with a rotating flow instability in the compressor.

Flow Characteristics of Tip Clearance in Axial Compressor

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.741.504 ◽

2015 ◽

Vol 741 ◽

pp. 504-508

Author(s):

Yong Lei Qu ◽

Bo Wan ◽

Xiao Meng Pei

Keyword(s):

Flow Characteristics ◽

Axial Compressor ◽

Axial Flow ◽

Internal Flow ◽

Tip Clearance ◽

Leakage Flow ◽

Compressor Rotor ◽

Overall Performance ◽

Flow Compressor ◽

Tip clearance of compressor rotor blade is introduced for avoiding friction collision between the moving blade and the casing. Because of the existence of the pressure difference between pressure surfaces and the suction surfaces of the blade, the blending of the leakage flow with the mainstream causes losses, which affects internal flow field and overall performance of the compressor. In this article, numerical analysis software is used to study the multi-condition performance of a six and a half axial flow compressor, for analyzing the impact of leakage flow patterns on compressor.

Axial Compressor Mean-Line Analysis: Choking Modelling and Fully-Coupled Integration in Engine Performance Simulations

International Journal of Turbomachinery Propulsion and Power ◽

10.3390/ijtpp6010004 ◽

2021 ◽

Vol 6 (1) ◽

pp. 4

Author(s):

Ioannis Kolias ◽

Alexios Alexiou ◽

Nikolaos Aretakis ◽

Konstantinos Mathioudakis

Keyword(s):

Axial Compressor ◽

Engine Performance ◽

Engine Model ◽

Multi Stage ◽

Transient Simulations ◽

Full Knowledge ◽

Compressor Performance ◽

First Time ◽

Performance Calculation ◽

Fully Coupled

A mean-line compressor performance calculation method is presented that covers the entire operating range, including the choked region of the map. It can be directly integrated into overall engine performance models, as it is developed in the same simulation environment. The code materializing the model can inherit the same interfaces, fluid models, and solvers, as the engine cycle model, allowing consistent, transparent, and robust simulations. In order to deal with convergence problems when the compressor operates close to or within the choked operation region, an approach to model choking conditions at blade row and overall compressor level is proposed. The choked portion of the compressor characteristics map is thus numerically established, allowing full knowledge and handling of inter-stage flow conditions. Such choking modelling capabilities are illustrated, for the first time in the open literature, for the case of multi-stage compressors. Integration capabilities of the 1D code within an overall engine model are demonstrated through steady state and transient simulations of a contemporary turbofan layout. Advantages offered by this approach are discussed, while comparison of using alternative approaches for representing compressor performance in overall engine models is discussed.

Compressor Performance and Operability in Swirl Distortion

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22777 ◽

2010 ◽

Cited By ~ 1

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 ◽

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.