An Experimental Examination of Cantilevered and Shrouded Stators in a Multistage Axial Compressor

1998 ◽  
Author(s):  
M. Swoboda ◽  
P. C. Ivey ◽  
U. Wenger ◽  
V. Gümmer
Keyword(s):  
Large Scale ◽  
Flow Analysis ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Stall Margin ◽  
Controlled Diffusion ◽  
Radial Profiles ◽  
Through Flow

This paper presents experimental investigations on a large-scale low-speed compressor facility with four repeating stages equipped with CDA-profiles (Controlled Diffusion Airfoils). Two different builds were investigated. Both builds used identical rotors, but had stators configured either in cantilevered or in shrouded form. Traverse measurements of total pressure and flow angle at six axial locations (IGV, two rotor and three stator exit planes) were performed between 1% and 99% annulus height and across two blade pitches. Circumferentially mass-averaged radial profiles were used in a through-flow code for reconstruction analysis of the measurements. In addition to the traverse measurements surface static pressures on stage 3 rotor and stator were measured. The effect of the “free-end” configuration on an embedded stage of this multistage compressor is described and compared to the shrouded configuration. The objective of this study was to investigate the differences of these two configurations and especially the effects caused by the hub clearance vortex in the cantilevered case. The entire set of measurements and through-flow analysis was performed at two operating points of the compressor i.e. at peak efficiency and near stall condition. Thus also the effects of the hub clearance vortex which influences the stall margin of the compressor are described. The analysis of the results shows slightly higher pressure rise coefficients for shrouded stators, but slightly higher stall margin in the cantilevered case. This is due to a stabilizing effect of the hub clearance vortex (cleans up separation on hub) in the cantilevered configuration because its direction is opposite to the secondary flow in the passage.

Design and Test of a Novel Highly-Loaded Compressor

2019 ◽  
Author(s):  
Chengwu Yang ◽  
Ge Han ◽  
Shengfeng Zhao ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
...  
Keyword(s):  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Flow Angle ◽  
Stall Margin ◽  
High Pressure Ratio ◽  
Numerical Predictions ◽  
Highly Loaded

Abstract The blades of rear stages in small size core compressors are reduced to shorter than 20 mm or even less due to overall high pressure ratio. The growing of tip clearance-to-blade height ratio of the rear stages enhance the leakage flow and increase the possibility of a strong clearance sensitivity, thus limiting the compressor efficiency and stability. A new concept of compressor, namely diffuser passage compressor (DP), for small size core compressors was introduced. The design aims at making the compressors robust to tip clearance leakage flow by reducing pressure difference between pressure and suction surfaces. To validate the concept, the second stage of a two-stage highly loaded axial compressor was designed with DP rotor according to a diffuser map. The diffuser passage stage has the same inlet condition and loading as the conventional compressor (CNV) stage, of which the work coefficient is around 0.37. The predicted performance and flow field of the DP were compared with the conventional axial compressor in detail. The rig testing was supplemented with the numerical predictions. Results reveal that the throttle characteristic of DP indicates higher pressure rise and the loss reduction in tip clearance is mainly responsible for the performance improvement. For the compressor with DP, the pressure and flow angle are more uniform on exit plane. What’s more, the rotor with diffused passage reveals more robust than the conventional rotor at double clearance gap. Furthermore, the experimental data indicate that DP presents higher pressure rise at design and part speeds. At design speed, the stall margin was extended by 7.25%. Moreover, peak adiabatic efficiency of DP is also higher than that of CNV by about 0.7%.

Automated Blade Optimization and 3D CFD Analysis for an Axial Multistage GT Compressor Redesign

2006 ◽  
Author(s):  
Lars Moberg ◽  
Gianfranco Guidati ◽  
Sasha Savic
Keyword(s):  
Flow Analysis ◽  
Optimization Methods ◽  
Design System ◽  
Cfd Analysis ◽  
Controlled Diffusion ◽  
Repetitive Tasks ◽  
Blade Optimization ◽  
Through Flow ◽  
Compressor Design ◽  
Linux Cluster

This paper focuses on (1) the basic compressor layout based on meridional through flow analysis and (2) the re-design of blades and vanes using sophisticated automated design optimization methods. All tools and processes are integrated into a consistent Compressor Design System, which runs on a powerful Linux cluster. This design system allows designing, analyzing and documenting blade design in mostly automated way. This frees the engineer from repetitive tasks and allows him to concentrate on a physical understanding and improvement of the compressor. The tools and methods are illustrated on the basis of an actual ALSTOM compressor. The main objectives of this upgrade are a modest increase in mass flow and an efficiency improvement. The latter is to be achieved through the replacement of NACA blades by modern Controlled Diffusion Airfoils (CDA). Results are presented including a CFD analysis of the front stages of the baseline and upgrade compressor.

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.

Performance of Strongly Bowed Stators in a Four-Stage High-Speed Compressor

2004 ◽  
Vol 126 (3) ◽  
pp. 333-338 ◽  
Author(s):  
Axel Fischer ◽  
Walter Riess ◽  
Joerg R. Seume
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Controlled Diffusion ◽  
Stage 4 ◽  
The University

The FVV sponsored project “Bow Blading” (cf. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in a four-stage high-speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e., between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.

Experimental Investigation of the Diffuser Vane Clearance Effect in a Centrifugal Compressor Stage With Adjustable Diffuser Geometry: Part II—Detailed Flow Analysis

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Stefan Ubben ◽  
Reinhard Niehuis
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Stall Margin ◽  
Diffuser Flow ◽  
Radial Gap ◽  
The Impact ◽  
Vane Angle

Adjustable diffuser vanes offer an attractive design option for centrifugal compressors applied in industrial applications. However, the knowledge about the impact on compressor performance of a diffuser vane clearance between vane and diffuser wall is still not satisfying. This two-part paper summarizes results of experimental investigations performed with an industrial-like centrifugal compressor. Particular attention was directed toward the influence of the diffuser clearance on the operating behavior of the entire stage, the pressure recovery in the diffuser, and on the diffuser flow by a systematic variation of the parameters diffuser clearance height, diffuser vane angle, radial gap between impeller exit and diffuser inlet, and rotor speed. In Part I it was shown that an one-sided diffuser clearance is able to contribute to an increase in flow range, stall margin, pressure ratio, and efficiency. In order to reveal the relevant flow phenomena, in Part II the results of detailed measurements of the pressure distribution at diffuser exit and particle image velocimetry (PIV) measurements inside the diffuser channel performed at three clearance configurations and three diffuser angles at a fixed radial gap are discussed. It was found that, for defined diffuser configurations, the clearance flow amplifies the diffuser throat vortex capable to reduce the loading of the highly loaded vane pressure side and to support a more homogenous diffuser flow. It turned out that the co-action of the geometry parameter diffuser vane angle and diffuser clearance height is of particular importance. The experimental results are published as an open computational fluid dynamics (CFD) testcase “Radiver 2.”

Investigation of Tip Clearance Phenomena in an Axial Compressor Cascade Using Euler and Navier–Stokes Procedures

1993 ◽  
Vol 115 (3) ◽  
pp. 453-467 ◽  
Author(s):  
R. F. Kunz ◽  
B. Lakshminarayana ◽  
A. H. Basson
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Numerical Procedure ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Flow Angle ◽  
Physical Phenomena

Three-dimensional Euler and full Navier–Stokes computational procedures have been utilized to simulate the flow field in an axial compressor cascade with tip clearance. An embedded H-grid topology was utilized to resolve the flow physics in the tip gap region. The numerical procedure employed is a finite difference Runge-Kutta scheme. Available measurements of blade static pressure distributions along the blade span, dynamic pressure and flow angle in the cascade outlet region, and spanwise distributions of blade normal force coefficient and circumferentially averaged flow angle are used for comparison. Several parameters that were varied in the experimental investigations were also varied in the computational studies. Specifically, measurements were taken and computations were performed on the configuration with and without: tip clearance, the presence of an endwall, inlet endwall total pressure profiles and simulated relative casing rotation. Additionally, both Euler and Navier–Stokes computations were performed to investigate the relative performance of these approaches in reconciling the physical phenomena considered. Results indicate that the Navier–Stokes procedure, which utilizes a low Reynolds number k–ε model, captures a variety of important physical phenomena associated with tip clearance flows with good accuracy. These include tip vortex strength and trajectory, blade loading near the tip, the interaction of the tip clearance flow with passage secondary flow, and the effects of relative endwall motion. The Euler computation provides good but somewhat diminished accuracy in resolution of some of these clearance phenomena. It is concluded that the level of modeling embodied in the present approach is sufficient to extract much of the tip region flow field information useful to designers of turbomachinery.

Modeling of Axial Compressor with Large Tip Clearances

2021 ◽  
pp. 1-27
Author(s):  
Simon Evans ◽  
Junsok Yi ◽  
Sean Nolan ◽  
Liselle Joseph ◽  
Michael Ni ◽  
...  
Keyword(s):  
Technology Development ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Core Size ◽  
Tip Leakage Flow ◽  
Axial Compressors ◽  
Tip Leakage ◽  
Mesh Topology ◽  
Radial Profiles ◽  
Predictive Design

Abstract In the drive for lower fuel consumption, engine designs for the next generation of single-aisle aircraft will require core sizes below 3 lb/s and OPRs above 50. Traditionally, these core sizes are the domain of centrifugal compressors, but materials limit OPR in these machines. An all-axial HPC at this core size, however, comes with limitations associated with the small blade spans at the back of the HPC, as clearances, fillets and leading edges do not scale with the core size. The result is a substantial efficiency penalty, driven primarily by the tip leakage flow produced by the larger clearance-to-span ratio. To enable small-core, high-OPR, all-axial compressors, mitigating technologies need to be developed and implemented to reduce this penalty. For this technology development to be successful, it is imperative that predictive design tools accurately model the overall flow physics and trends of the technologies developed. In this paper we describe an effort to determine whether different modeling standards are required for large clearance-to-span ratios, and if so, identify criteria for an appropriate solver and/or mesh. Multiple models are run and results compared with data collected in the NASA-GRC Low-Speed Axial Compressor. These comparisons show that steady RANS solvers can predict the pressure-rise characteristic to an acceptable level of accuracy, if careful attention is paid to mesh topology in the tip region. However, unsteady tools are necessary to accurately capture radial profiles of blockage and total pressure.

Performance of Strongly Bowed Stators in a 4-Stage High Speed Compressor

2003 ◽  
Author(s):  
Axel Fischer ◽  
Walter Riess ◽  
Joerg R. Seume
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Controlled Diffusion ◽  
Stage 4 ◽  
The University

The FVV-sponsored-Project “Bow Blading” (c.f. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in an 4-stage high speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e. between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.

Time Resolved Experimental Investigations of an Axial Compressor With Casing Treatment

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
R. Emmrich ◽  
H. Hönen ◽  
R. Niehuis
Keyword(s):  
Physical Phenomenon ◽  
Flow Analysis ◽  
Axial Compressor ◽  
Suction Side ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Pressure Probe ◽  
Time Resolved ◽  
Casing Treatment ◽  
Compressor Rotor

A casing treatment with axial and radial skewed slots ending in a plenum chamber has experimentally been investigated at a highly subsonic axial compressor stage. The aim was to investigate the physical phenomenon of this treatment family that is responsible for the stabilization of the blade passage flow and the drop in efficiency mostly observed. The experimentally gained performance results of this configuration showed an extension of the operating range by approximately 50%, while the efficiency for design conditions is reduced by 1.4%. Apart from this, operating points at part load conditions have been observed nearly without any loss in efficiency. The detailed flow analysis is performed by means of results from a 3D pneumatic probe with temperature sensor and a dynamic total pressure probe. The focus of the investigations is on the incidence flow to the compressor rotor, the tip clearance vortex flow in combination with the wall stall separation region and the blade stall due to suction side separation. The casing treatment configuration is investigated with a special interest in detecting those effects which have an impact on the stability and the compressor overall efficiency, including the interaction of the rotor and the stator flow fields.

An Experimental Study of Stall Suppression and Associated Changes to the Flow Structures in the Tip Region of an Axial Low Speed Fan Rotor by Axial Casing Grooves

2017 ◽  
Author(s):  
Huang Chen ◽  
Yuanchao Li ◽  
Subhra Shankha Koley ◽  
Nick Doeller ◽  
Joseph Katz
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Pressure Rise ◽  
Leading Edge ◽  
Suction Side ◽  
Rotating Stall ◽  
Flow Structures ◽  
Flow Angle ◽  
Low Speed ◽  
Flow Characterization

The effects of axial casing grooves on the performance and flow structures in the tip region of an axial low speed fan rotor have been studied experimentally in the JHU refractive index-matched liquid facility. The four-per-passage semicircular grooves are skewed by 45° in the positive circumferential direction, and have a diameter of 65% of the rotor blade axial chord length. A third of the groove overlaps with the blade front, and the rest extends upstream. These grooves have a dramatic effect on the machine performance, reducing the stall flow rate by 40% compared to the same machine with a smooth endwall. However, they reduce the pressure rise at high flow rates. The flow characterization consists of qualitative visualizations of vortical structures using cavitation, as well as stereo-PIV (SPIV) measurements in several meridional and (z,θ) planes covering the tip region and interior of the casing grooves. The experiments are performed at a flow rate corresponding to pre-stall conditions for the untreated machine. They show that the flow into the downstream sides of the grooves and the outflow from their upstream sides vary periodically. The inflow peaks when the downstream end is aligned with the pressure side (PS) of the blade, and decreases, but does not vanish, when this end is located near the suction side (SS). These periodic variations have three primary effects: First, substantial fractions of the leakage flow and the tip leakage vortex (TLV) are entrained periodically into the groove. Consequently, in contrast to the untreated flow, The TLV remnants remain confined to the vicinity of the entrance to the groove, and the TLV strength diminishes starting from the mid-chord. Second, the grooves prevent the formation of large scale backflow vortices (BFVs), which are associated with the TLV, propagate from one blade passage to the next, and play a key role in the onset of rotating stall in the untreated fan. Third, the flow exiting from the grooves causes periodic variations of about 10° in the relative flow angle around the blade leading edge, presumably affecting the blade loading. The distributions of turbulent kinetic energy provide statistical evidence that in contrast to the untreated casing, very little turbulence originating from a previous TLV, including the BFVs, propagates from the PS to the SS of the blade. Hence, the TLV-related turbulence remain confined to the entrance to groove. Elevated, but lower turbulence is also generated as the outflow from the groove jets into the passage.

Sign in / Sign up

Export Citation Format

Share Document