scholarly journals A Practical Compressor Casing Treatment

1997 ◽  
Author(s):  
Syed Khalid
Keyword(s):  
Suction Side ◽  
Velocity Variation ◽  
Cell Orientation ◽  
Stall Margin ◽  
Exit Velocity ◽  
Casing Treatment ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Inclination Angles ◽  
Side Flow

A three stage compressor test incorporating casing inserts comprised of compound angled honeycomb cells demonstrated up to 10% higher stall margin than circumferential grooves casing treatment. This is attributed to effective tip flow energization resulting from the unsteady flow induced in and out of the cells as the blade tip sweeps by the cell openings. The rationale for selecting the cell inclination angles both relative to the normal and the tangential directions is discussed. The design intent of the cell orientation is to induce a high cell exit velocity as well as to impart a degree of flow alignment to the injected jets. A first order calculation of cell exit velocity variation based on the cell pressure/volume dynamics is indicative of unsteady blowing which is theorized to effectively mix the tip suction side flow and to enhance the tip flow streamwise momentum. This theory is partially substantiated by the presented compressor test results showing improved radial total pressure profiles, stage characteristics, and stall margin. Since a few unhealthy stages of a multi-stage compressor could make it stall prone, casing treatment of those weak stages could dramatically increase stall margin with negligible impact on overall adiabatic efficiency. In addition to the aerodynamic effectiveness, the mechanical suitability of this casing treatment to multistage compressors, based on its demonstrated abradability and packageability, is discussed.

scholarly journals Axial Flow Compressor Stability Enhancement: Circumferential T-Shape Grooves Performance Investigation

Aerospace ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 12
Author(s):  
Marco Porro ◽  
Richard Jefferson-Loveday ◽  
Ernesto Benini
Keyword(s):  
Vortex Breakdown ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Suction Side ◽  
Treatment Technique ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stall Margin Improvement

This work focuses its attention on possibilities to enhance the stability of an axial compressor using a casing treatment technique. Circumferential grooves machined into the case are considered and their performances evaluated using three-dimensional steady state computational simulations. The effects of rectangular and new T-shape grooves on NASA Rotor 37 performances are investigated, resolving in detail the flow field near the blade tip in order to understand the stall inception delay mechanism produced by the casing treatment. First, a validation of the computational model was carried out analysing a smooth wall case without grooves. The comparisons of the total pressure ratio, total temperature ratio and adiabatic efficiency profiles with experimental data highlighted the accuracy and validity of the model. Then, the results for a rectangular groove chosen as the baseline case demonstrated that the groove interacts with the tip leakage flow, weakening the vortex breakdown and reducing the separation at the blade suction side. These effects delay stall inception, improving compressor stability. New T-shape grooves were designed keeping the volume as a constant parameter and their performances were evaluated in terms of stall margin improvement and efficiency variation. All the configurations showed a common efficiency loss near the peak condition and some of them revealed a stall margin improvement with respect to the baseline. Due to their reduced depth, these new configurations are interesting because they enable the use of a thinner light-weight compressor case as is desirable in aerospace applications.

Effect of Various Trench Designs on Axial Compressor Blade Tip Aerodynamics

2019 ◽  
Author(s):  
Ashwin Ashok ◽  
Patur Ananth Vijay Sidhartha ◽  
Shine Sivadasan
Keyword(s):  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Leakage Vortex ◽  
Stall Margin ◽  
Casing Treatment ◽  
Tip Leakage

Abstract Tip clearance of axial compressor blades allows leakage of the flow, generates significant losses and reduces the compressor efficiency. The present paper aims to discuss the axial compressor tip aerodynamics for various configurations of tip gap with trench. The various configurations are obtained by varying the clearance, trench depth, step geometry and casing contouring. In this paper the axial compressor aerodynamics for various configurations of tip gap with trench have been studied. The leakage flow structure, vorticity features and entropy generations are analyzed using RANS based CFD. The linear compressor cascade comprises of NACA 651810 blade with clearance height varied from 0.5% to 2% blade span. Trail of the tip leakage vortex and the horseshoe vortex on the blade suction side are clearly seen for the geometries with and without casing treatments near the stalling point. Since the trench side walls are similar to forward/backing steps, a step vortex is observed near the leading edge as well as trailing edge of the blade and is not seen for the geometry without the casing treatment. Even though the size of the tip leakage vortex seams to be reduces by providing a trench to the casing wall over the blade, the presence of additional vortices like the step vortex leads to comparatively higher flow losses. An increase in overall total pressure loss due to the application of casing treatment is observed. However an increase in stall margin for the geometries with casing is noted.

Squealer Tip Treatment Design for Axial Compressors

2020 ◽  
Author(s):  
Giuseppe Bruni ◽  
James Taylor ◽  
Senthil Krishnababu ◽  
Robert Miller ◽  
Roger Wells
Keyword(s):  
Thickness Distribution ◽  
Axial Compressor ◽  
Leading Edge ◽  
Experimental Tests ◽  
Suction Side ◽  
Rotor Blades ◽  
Superior Performance ◽  
Stall Margin ◽  
Wall Flows ◽  
Multi Stage

Abstract End-wall flows are amongst the main sources of losses in the rear stages of a typical multi-stage axial compressor. Reducing the tip leakage losses in the rotor blades and vanes can provide an increased efficiency and stall margin of a given axial compressor stage. One approach is to use squealer tips, which are traditionally designed to minimize the effect of tip rubbing. However, squealers can also provide a significant performance benefit, when designed considering aerodynamics from the beginning, as shown in this paper. A CFD based methodology, in which the blade or vane thickness distribution is varied in a controlled manner was developed. This design methodology was used to create different types of squealer tip geometry for a representative stage in a low speed compressor rig. Three different tip concepts were designed, based on a Suction Side Squealer, on a Pressure Side Squealer and on the combination of the two being merged between the leading edge and trailing edge, this new design is called the SuPr Tip. Subsequent experimental tests carried out agreed with the predicted relative ranking of the different squealer designs and on the superior performance of the SuPr tip design over the others, thus validating the methodology and the design process.

A Study of Performance and Flow Mechanism of a Slot-Groove Hybrid Casing Treatment in a Low-Speed Compressor

2015 ◽  
Author(s):  
Juan Du ◽  
Fan Li ◽  
Jichao Li ◽  
Ning Ma ◽  
Feng Lin ◽  
...  
Keyword(s):  
Axial Compressor ◽  
Suction Side ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Low Speed ◽  
High Entropy ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Flow Loss ◽  
The Difference

A “slot-groove” hybrid casing treatment (CT) is proposed elicited from the recent research on the role of axial location for stall margin improvement (SMI). This combination is expected to display the advantages of both slots and grooves while minimizing their disadvantages. A comparative study is conducted among the “slot-groove”, traditional circumferential groove CT (called the “full-groove” CT) and axial skewed slot CT (known as the “full-slot” CT) to evaluate performance and to explore the stability enhancement and efficiency loss mechanisms of the “slot-groove” CT in a low-speed axial compressor. Results of the combination of laboratory tests and computational fluid dynamics (CFD) data demonstrate that the performance level of the hybrid CT lies in between those two traditional CTs. Simulation results indicate that the difference in the SMIs generated by CTs is closely related to their influences on the vortex trajectory of tip leakage. The stronger and tighter the vortex is, the more the vortex trajectory is inclined toward the blade suction side. Consequently, the interface between tip leakage flow and incoming main flow is pushed downstream and stability is enhanced. The flow loss induced by CTs is explored based on the entropy contours, and the high entropy in the “slot-groove” treated casing produces more efficiency decrease than the “full-groove” CT. Incorporating the “full-slot” CT not only increases entropy generation in the axial skewed slots but also induces considerable flow loss in the blade passage near the casing, thus reducing efficiency most significantly.

Aerodynamic Redesign of a 5-Stage Axial Compressor by Re-Stagger and Bow

2015 ◽  
Author(s):  
Tao Ning ◽  
Chun-wei Gu ◽  
Xiao-tang Li ◽  
Tai-qiu Liu ◽  
Yao-bing Xiao
Keyword(s):  
Axial Compressor ◽  
Aerodynamic Optimization ◽  
Stall Margin ◽  
High Loss ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Scale Test ◽  
Overall Performance ◽  
Operating Points

The paper is a preliminary methodology research of the aerodynamic redesign of a 5-stage axial compressor by re-stagger and bow with multistage CFD methods, with the purpose of developing the next upgrade version of this type of compressor. Prior to aerodynamic redesign, the validation study is carried out for overall performance, casing static pressure and spanwise total pressure profiles based on full-scale test data, proving that the multistage CFD applied is a relatively reliable tool for the analysis of the follow-up redesigning. Furthermore, at the near stall point, aerodynamic analysis demonstrates that significant separation exits in the last stator, which leads to the aerodynamic redesign focused on the last stator. To explore the potential of aerodynamic improvement, it is focused on the aerodynamic redesign by re-stagger and bow. Multi-stage CFD methods are applied in the whole redesign process. Two steps of redesigning are applied for aerodynamic optimization. Upgrade 1 by re-stagger is used to adjust the operating points to more reasonable region, which contributes about 9 percent stall margin increase. Based on upgrade 1, an unconventional asymmetric bow configure is employed in upgrade 2 to reduce the high loss region dominated by mainstream. The redesigning exploitation by re-stagger and bow in this research produces a total 16% increase in stall margin.

Accurate Simulation of the Four Modes of Post-Die Extrudate Shape Distortion

2021 ◽  
Vol 36 (1) ◽  
pp. 69-78
Author(s):  
M. Gupta
Keyword(s):  
Layer Structure ◽  
Die Design ◽  
Velocity Variation ◽  
Shape Distortion ◽  
Exit Velocity ◽  
Extrusion Die ◽  
Combined Flow ◽  
Extruded Product ◽  
Simulation Results ◽  
Extrudate Distortion

Abstract A combined flow, thermal and structural analysis is employed to simulate post-die extrudate distortion in different profile dies. All four factors which can cause extrudate distortion, namely, nonuniform exit velocity distribution, extrudate shrinkage, extrudate draw down, and deformed shape of the calibrator or sizer profile, are simulated. To analyze the effect of exit velocity variation on extrudate distortion, the parameterized geometry of a simple profile die is optimized using an extrusion die optimization software. The simulation results presented for a bi-layer profile die successfully demonstrate how gradually changing profile shape in successive calibrators/sizers can be used to simplify the die design for extrusion of complex profiles. The predicted extrudate shape and layer structure for the bi-layer die are found to accurately match with those in the extruded product.

Numerical Investigation on the Effect of Vortex Generator on Axial Compressor Performance

2014 ◽  
Author(s):  
Ruchika Agarwal ◽  
Anand Dhamarla ◽  
Sridharan R. Narayanan ◽  
Shraman N. Goswami ◽  
Balamurugan Srinivasan
Keyword(s):  
Cross Flow ◽  
Axial Compressor ◽  
Vortex Generator ◽  
Side Surface ◽  
Suction Side ◽  
Test Case ◽  
Stall Margin ◽  
Layer Flow ◽  
Flow Effects ◽  
End Wall

The performance of the compressor blade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as corner flow separation between the wall and the blade. The present work is focused on the studying the effects of Vortex Generator (VG) on NASA Rotor 37 test case using Computational Fluid Dynamics (CFD). VG helps in controlling the inception of the stall by generating vortices and energizes the low momentum boundary layer flow which enhances the rotor performance. Three design configuration namely, Counter-rotating, Co-rotating and Plow configuration VG are selected based on the improved aerodynamic performance discussed in reference [1]. These VG are located at 90% span and 42% chord on suction side surface of the blade. Among the three configurations, the first configuration has greater impact on the end wall cross flow and flow deflection which resulted in enhanced numerical stall margin of 5.4% from baseline. The reasons for this numerical stall margin improvement are discussed in detail.

scholarly journals Effects of Endwall Suction and Blowing on Compressor Stability Enhancement

1989 ◽  
Author(s):  
N. K. W. Lee ◽  
E. M. Greitzer
Keyword(s):  
Flow Injection ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Primary Objective ◽  
Stall Margin ◽  
Casing Treatment ◽  
Blade Row ◽  
Stall Margin Improvement ◽  
Stability Enhancement ◽  
Suction And Blowing

An experimental investigation was carried out to examine the effects on stall margin of flow injection into, and flow removal out of, the endwall region of an axial compressor blade row. A primary objective of the investigation was clarification of the mechanism by which casing treatment (which involves both removal and injection) suppresses stall in turbomachines. To simulate the relative motion between blade and treatment, the injection and removal took place through a slotted hub rotating beneath a cantilevered stator row. Overall performance data and detailed (time-averaged) flowfield measurements were obtained. Flow injection and removal both increased the stalling pressure rise, but neither was as effective as the wall treatment. Removal of high blockage flow is thus not the sole reason for the observed stall margin improvement in casing or hub treatment, as injection can also contribute significantly to stall suppression. The results also indicate that the increase in stall pressure rise with injection is linked to the streamwise momentum of the injected flow, and it is suggested that this should be the focus of further studies.

Investigation of Recirculating Casing Treatment for Low-Pressure Ratio Mixed-Flow Micro-Compressor

2020 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Pressure Ratio ◽  
Numerical Approach ◽  
Efficiency Loss ◽  
Stall Margin ◽  
Design Point ◽  
Casing Treatment ◽  
Final Design ◽  
Upstream Flow ◽  
Total Pressure Ratio ◽  
Good Agreement

Abstract This paper investigates the recirculating casing treatment (RCT) of a low total pressure ratio micro-compressor to achieve stall margin enhancement while minimizing the design point efficiency penalty. Three RCT injection and extraction configurations are studied, including combined slot-duct, ducts only, and slot only. The numerical approach is validated with a tested micro-compressor using RCT. A very good agreement is achieved between the predicted speedlines and the measured results. To minimize the design point efficiency loss, it is observed that the optimal location of extraction and injection is where the recirculated flow rate can be minimized at the design point. To maximize stall margin, extraction location should favor minimizing the tip blockage such as at the location where the tip flow separation of the baseline blade is fully developed. In addition, the slot configuration that generates pre-swirl to the upstream flow is beneficial to improve stall margin due to reduced incidence. The highest stall margin enhancement achieved is 9.49% with the slot geometry that has the extraction at the 62%C chordwise location, but has a design point efficiency loss of 1.9%. Overall, a small efficiency penalty of 0.6% at the design point is achieved for the final design with the stall margin increased by 6.2%.

Use of Horizontal Drift-Flux Models For Simulating Wellbore Flow in SAGD Operations

2021 ◽  
Author(s):  
Mohammad Heidari ◽  
Christopher Istchenko ◽  
William Bailey ◽  
Terry Stone
Keyword(s):  
Flux Flow ◽  
Pressure Drops ◽  
Steam Assisted Gravity Drainage ◽  
Drift Flux ◽  
Pressure Profiles ◽  
Well Model ◽  
Inclination Angles ◽  
Operation Pressure ◽  
Reservoir Simulator ◽  
High Degree

Abstract The paper examines new horizontal drift-flux correlations for their ability to accurately model phase flow rates and pressure drops in horizontal and undulating wells that are part of a Steam-Assisted Gravity Drainage (SAGD) field operation. Pressure profiles within each well correlate to the overall performance of the pair. SAGD is a low-pressure process that is sensitive to reservoir heterogeneity and other factors, hence accurate simulation of in situ wellbore pressures is critical for both mitigating uneven steam chamber evolution and optimizing wellbore design and operation. Recently published horizontal drift-flux correlations have been implemented in a commercial thermal reservoir simulator with a multi-segment well model. Valid for horizontally drilled wells with undulations, they complement previously reported drift-flux models developed for vertical and inclined wells down to approximately 5 degrees from horizontal. The formulation of these correlations has a high degree of nonlinearity. These models are tested in simulations of SAGD field operations. First, an overview of drift-flux models is discussed. This differentiates those based on vertical flow with gravity segregation to those that model horizontal flow with stratified and slug flow regimes. Second, the most recent and significant drift-flux correlation by Bailey et al. (2018, and hereafter referred to as Bailey-Tang-Stone) was robustly designed to be used in the well model of a reservoir simulator, can handle all inclination angles and was optimized to experimental data from the largest available databases to date. This and earlier drift-flux models are reviewed as to their strengths and weaknesses. Third, governing equations and implementation details are given of the Bailey-Tang-Stone model. Fourth, six case studies are presented that illustrate homogeneous and drift-flux flow model differences for various well scenarios.

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