Periodic Unsteady Kinematics of Hub Flows in a Shrouded Multistage Compressor

2021 ◽  
Author(s):  
Jaehyoung Lee ◽  
Sungkyung Lim ◽  
Sungryong Lee ◽  
Hyoun-Woo Shin ◽  
Seung Jin Song
Keyword(s):  
Axial Compressor ◽  
Suction Side ◽  
Labyrinth Seal ◽  
Streamwise Vorticity ◽  
Time Data ◽  
Rotor Wake ◽  
Radial Migration ◽  
Pressure Surface ◽  
Multistage Compressor ◽  
First Time

Abstract Periodic unsteady flow kinematics in a shrouded multistage low-speed axial compressor has been measured for the first time. Data have been acquired at the inlet and exit of a shrouded 3rd- stage stator with a particular focus on the hub flows. The newly found features of the hub flow in a shrouded multistage compressor are different from those at the midspan or in unshrouded (i.e., cantilevered) compressors. First, the merging of the 2nd-stage stator and 3rd-stage rotor wakes causes positive radial migration near the rotor wake pressure surface at the hub of the 3rd-stage stator inlet. Second, the low-momentum labyrinth seal leakage flow of the 3rd-stage stator merges with the 3rd-stage rotor wake to create streamwise vorticity at the 3rd-stage stator inlet hub. Third, contrary to unshrouded stators, suction side hub corner separation in the shrouded 3rd-stage stator reduces rotor wake stretching. Thus, velocity disturbances are attenuated less, and amplitudes of periodic fluctuations in flow angles are larger at the 3rd-stage stator exit hub than at midspan. The positive radial migration of the rotor wake hub flow and wake stretching reduction are expected to decrease efficiency, whereas streamwise vorticity generation is expected to increase efficiency.

Periodic Unsteady Kinematics of Hub Flows in a Shrouded Multistage Compressor

2021 ◽  
Author(s):  
Jaehyoung Lee ◽  
Sungkyung Lim ◽  
Hyoun-Woo Shin ◽  
Sungryong Lee ◽  
Seung Jin Song
Keyword(s):  
Axial Compressor ◽  
Suction Side ◽  
Labyrinth Seal ◽  
Streamwise Vorticity ◽  
Time Data ◽  
Rotor Wake ◽  
Radial Migration ◽  
Pressure Surface ◽  
Multistage Compressor ◽  
First Time

Abstract Periodic unsteady flow kinematics in a shrouded multistage low-speed axial compressor has been measured for the first time. Data have been acquired at the inlet and exit of a shrouded 3rd-stage stator with a particular focus on the hub flows. The newly found features of the hub flow in a shrouded multistage compressor are different from those at the midspan or in unshrouded (i.e., cantilevered) compressors. First, the merging of the 2nd-stage stator and 3rd-stage rotor wakes causes positive radial migration near the rotor wake pressure surface at the hub of the 3rd-stage stator inlet. Second, the low-momentum labyrinth seal leakage flow of the 3rd-stage stator merges with the 3rd-stage rotor wake to create streamwise vorticity at the 3rd-stage stator inlet hub. Third, contrary to unshrouded stators, suction side hub corner separation in the shrouded 3rd-stage stator reduces rotor wake stretching. Thus, velocity disturbances are attenuated less, and amplitudes of periodic fluctuations in flow angles are larger at the 3rd-stage stator exit hub than at midspan. The positive radial migration of the rotor wake hub flow and wake stretching reduction are expected to decrease efficiency, whereas streamwise vorticity generation is expected to increase efficiency.

Experimental Characterization of the Evolution of Global Flow Structure in the Passage of an Axial Compressor

2021 ◽  
Author(s):  
Ayush Saraswat ◽  
Subhra Shankha Koley ◽  
Joseph Katz
Keyword(s):  
Flow Structure ◽  
Rotor Blade ◽  
Incidence Angle ◽  
Substantial Reduction ◽  
Axial Compressor ◽  
Suction Side ◽  
Rotor Wake ◽  
Tip Leakage ◽  
Blade Tip

Abstract Ongoing experiments conducted in a one-and-half stages axial compressor installed in the JHU refractive index-matched facility investigate the evolution of flow structure across blade rows. After previously focusing only on the rotor tip region, the present stereo-PIV (SPIV) measurements are performed in a series of axial planes covering an entire passage across the machine, including upstream of the IGV, IGV-rotor gap, rotor-stator gap, and downstream of the stator. The measurements are performed at flow rates corresponding to pre-stall condition and best efficiency point (BEP). Data are acquired for various rotor-blade orientations relative to the IGV and stator blades. The results show that at BEP, the wakes of IGV and rotor are much more distinct and the wake signatures of one row persists downstream of the next, e.g., the flow downstream of the stator is strongly affected by the rotor orientation. In contrast, under pre-stall conditions, the rotor orientation has minimal effect on the flow structure downstream of the stator. However, the wakes of the stator blades, where the axial momentum is low, are now wider. For both conditions, the flow downstream of the rotor is characterized by two regions of axial momentum deficit in addition to the rotor wake. A deficit on the pressure side of the rotor wake tip is associated with the tip leakage vortex (TLV) of the previous rotor blade, and is much broader at pre-stall condition. A deficit on the suction side of the rotor wake near the hub appears to be associated with the hub vortex generated by the neighboring blade, and is broader at BEP. At pre-stall, while the axial momentum upstream of the rotor decreases over the entire tip region, it is particularly evident near the rotor blade tip, where the instantaneous axial velocity becomes intermittently negative. Downstream of the rotor, there is a substantial reduction in mean axial momentum in the upper half of the passage, concurrently with an increase in the circumferential velocity. Consequently, the incidence angle upstream of the stator increases in certain regions by up to 30 degrees. These observations suggest that while the onset of the stall originates from the rotor tip flow, one must examine its impact on the flow structure in the stator passage as well.

A numerical study on the unsteady effect of axial spacing on the performance in a contra-rotating axial compressor

2016 ◽  
Vol 231 (14) ◽  
pp. 2598-2609 ◽  
Author(s):  
Xiaochen Mao ◽  
Bo Liu
Keyword(s):  
Aerodynamic Force ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Maximum Amplitude ◽  
Local Maximum ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Surface ◽  
Unsteady Effects

Unsteady numerical simulations are conducted to investigate the unsteady effects of axial spacing on the performance of a contra-rotating axial compressor. The results show that the stage efficiency is dominant by unsteady effects between two rotors at lower axial gap ranges. As the axial spacing is increased, the variation of aerodynamic force is different for the two rotors. As a whole, the oscillation on the pressure surface is much stronger than that on the suction side in rotor1. For rotor2, however, the local maximum amplitude is just located at the blade leading edge, especially near the tip region. Additionally, the maximum amplitude of the pressure fluctuations generally decreases with an increase of axial spacing. The dominating frequency is different for monitors located at different positions and varies with the increasing of axial gaps. As the axial gap is increased, the potential effects decay in the process of propagating. Meanwhile, the incoming wakes are mixed out more sufficiently which would reduce the fluctuations at leading edge of rotor2. Therefore, a proper axial spacing should be chosen in the design process of a contra-rotating axial compressor considering both the performance and structure.

A Passive Flow Control to Mitigate the Corner Separation in an Axial Compressor by a Slotted Rotor Blade

2019 ◽  
Author(s):  
Sungho Yoon ◽  
Rao Ajay ◽  
Venkata Chaluvadi ◽  
Vittorio Michelassi ◽  
Ramakrishna Mallina
Keyword(s):  
Flow Control ◽  
Rotor Blade ◽  
Substantial Reduction ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Suction Side ◽  
Pressure Side ◽  
Stall Margin ◽  
Radial Migration ◽  
Corner Separation

Abstract The operability of the axial compressor is generally limited by endwall flows; either at the casing mainly due to the tip leakage flows or at the hub mainly due to three-dimensional corner separations. Therefore, it is crucial to improve flows near the endwalls to enhance the operability of the compressor. Based on a last-stage with cantilevered stator vanes, a small endwall slot was introduced to a rotor blade to mitigate the hub corner separation and maximize the aerodynamic operating range of axial compressors by natural aspiration. The developed flow control technology is numerically analyzed based on the in-house High-Speed Research Compressor (HSRC) which, in turn, represents the rear stage of a modern compressor. This compressor was predicted to stall due to hub corner separation on a rotor blade based on multistage CFD analysis. A small spanwise endwall slot, connecting the pressure side and the suction side of a compressor rotor blade, was introduced near the hub to provide the by-pass flows from the pressure side to the suction side (see Figure 1). This naturally-aspirated jet significantly reduced the three-dimensional corner separation which generally occurs where the suction side meets the hub. The substantial reduction of the three-dimensional corner separation, in turn, improved the aerodynamic stall margin of the compressor. The benefit is accomplished because the low momentum region near the hub was energized due to the naturally-aspirated jet through the endwall slot and the radial migration of the low momentum flow on the suction side was significantly reduced. A systematic parametric study was conducted to better understand the flow details and optimize the flow control without sacrificing aerodynamic efficiency. It was discovered that a very small slot, smaller than 10% of span, located near the endwall, was sufficient to have a more than 6% improvement of the stall margin with a negligible efficiency penalty (less than 0.1%). The naturally-aspirated flow through the small slot eliminates the source of the corner separation at the hub platform by strengthening the flow near the hub. This, in turn, reduces the overall aerodynamic blockage by decreasing the radial migration of the low momentum flow over a third of the span. Finally, evaluations of the mechanical strength and structural dynamics of slotted rotor blades, as well as the aerodynamic impact in a multi-stage environment were conducted and its results were discussed.

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

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.

scholarly journals Homopiperazine (Hexahydro-1,4-diazepine)

Molbank ◽  
10.3390/m1200 ◽  
2021 ◽  
Vol 2021 (2) ◽  
pp. M1200
Author(s):  
R. Alan Aitken ◽  
Dheirya K. Sonecha ◽  
Alexandra M. Z. Slawin
Keyword(s):  
13C Nmr ◽  
Title Compound ◽  
Coupling Constants ◽  
15N Nmr ◽  
Time Data ◽  
Nmr Spectrum ◽  
X Ray ◽  
First Time

The X-ray structure of the title compound has been determined for the first time. Data on its 1H–13C-NMR coupling constants and 15N-NMR spectrum are also given.

scholarly journals Deservingness for "Family 500 +" Benefit in Poland: Qualitative Study of Internet Debates

2021 ◽  
Author(s):  
Piotr Michoń
Keyword(s):  
Future Research ◽  
Online Forums ◽  
Time Data ◽  
Social Surveys ◽  
Cash Benefit ◽  
Internet Forums ◽  
Welfare Attitudes ◽  
New Criterion ◽  
First Time ◽  
The Relationship

AbstractThe need for qualitative research of deservingness perception is strongly emphasised in the literature. This article studies the perception of deservingness for a "Family 500 +"—cash benefit in Poland. For the first time, data from online forums was used in the studies of deservingness and welfare attitudes. It allowed to avoid numerous limitations associated with social surveys. The qualitative analysis showed how participants of Internet debates perceive the criteria of deservingness: control, attitude, reciprocity, identity, need, and what are the relations between the criteria. The impurity of all deservingness criteria was indicated and a new criterion “adequacy” was proposed. Moreover due to the fact that the study concerned a concrete, non-abstract family cash benefit addressed the relationship between the perceived deservingness of children and their parents was pointed out. The vast majority of posts on Internet forums referred to deservingness of parents, not children. This is particularly evident in relation to the criteria of control and reciprocity. Presenting the hypothesis of jealousy and scapegoat strategy, the article also shows the direction of future research on deservingness.

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 Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

1998 ◽  
Vol 120 (4) ◽  
pp. 705-713 ◽  
Author(s):  
S. T. Hsu ◽  
A. M. Wo
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Forced Response ◽  
Suction Surface ◽  
Blade Loading ◽  
Beneficial Use ◽  
Unsteady Loading ◽  
Vortical Disturbance ◽  
First Time

This paper demonstrates reduction of stator unsteady loading due to forced response in a large-scale, low-speed, rotor/stator/rotor axial compressor rig by clocking the downstream rotor. Data from the rotor/stator configuration showed that the stator response due to the upstream vortical disturbance reaches a maximum when the wake impinges against the suction surface immediately downstream of the leading edge. Results from the stator/rotor configuration revealed that the stator response due to the downstream potential disturbance reaches a minimum with a slight time delay after the rotor sweeps pass the stator trailing edge. For the rotor/stator/rotor configuration, with Gap1 = 10 percent chord and Gap2 = 30 percent chord, results showed a 60 percent reduction in the stator force amplitude by clocking the downstream rotor so that the time occurrence of the maximum force due to the upstream vortical disturbance coincides with that of the minimum force due to the downstream potential disturbance. This is the first time, the authors believe, that beneficial use of flow unsteadiness is definitively demonstrated to reduce the blade unsteady loading.

Intensifiers on Tyneside

2010 ◽  
Vol 31 (3) ◽  
pp. 252-287 ◽  
Author(s):  
Katie Barnfield ◽  
Isabelle Buchstaller
Keyword(s):  
Real Time ◽  
Longitudinal Analysis ◽  
Developmental Trajectories ◽  
Time Data ◽  
Longitudinal Changes ◽  
Real Time Data ◽  
Quantitative Development ◽  
First Time

We report on longitudinal changes in the system of intensification in an innovative corpus that spans five decades of dialectal speech. Our analyses allow us — for the first time in a British context — to trace the quantitative development in the variable across four generations. Longitudinal analysis across real and apparent time determines the effect of extralinguistic and intralinguistic variables on intensification in Tyneside and tests to what extent real time data corroborates trends reported from previous apparent time analyses. Long-term competition within the variable manifests itself in distinctive developmental trajectories: expansion — both proportionally within the variable as well as across adjectival categories — tends to follow one of three types of patterns, exemplified, respectively, by really, so and dead. Variant retraction, however, follows only one schema. Importantly, numerical decline in the system does not necessarily go hand in hand with a reduction in breadth of application.

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