Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part II — Influence of Diffuser Geometry on Stage Performance

2002 ◽  
Author(s):  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
M. De Lucia ◽  
L. Baldassarre
Keyword(s):  
Experimental Tests ◽  
Rotating Stall ◽  
Geometric Parameters ◽  
Flow Coefficient ◽  
Low Flow ◽  
Main Task ◽  
Stage Performance ◽  
The Impact ◽  
Prediction Criteria

Extensive research on centrifugal compressors has been planned. The main task of the research is to improve present prediction criteria coming from the literature with particular attention to low flow coefficient impellers (low width to radius ratios) where they are no more valid. Very little data has been published for this kind of stages, especially for the last stage configuration (with discharge volute). Many experimental tests have been planned to investigate different configurations. A simulated stage with a backward channel upstream, a 2D impeller with a vaneless diffuser and a constant cross section volute downstream constitute the basic configuration. Several diffuser types with different widths, pinch shapes and diffusion ratios were tested. The effect of geometric parameters on stage stability has been discussed inside part I of the present work; the purpose of this part of the work is to illustrate the effect of the same geometric parameters on stage performance and to quantify the impact of stability improvements on stage losses.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part I — Influence of Diffuser Geometry on Stall Inception

2002 ◽  
Author(s):  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
M. De Lucia ◽  
L. Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Experimental Tests ◽  
Rotating Stall ◽  
Main Task ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Stall Inception ◽  
Last Stage ◽  
Prediction Criteria

Extensive research on centrifugal compressors has been planned to define diffuser stall limits for a group of stages characterized by low blade-outlet-width-to-impeller-radius-ratio. Very little data is available on this centrifugal compressor family, especially for the last stage configuration. In addition, the most important stall diffuser prediction criteria barely cover this machine type. Many experimental tests have been planned to investigate several geometry variations. A simulated stage with a backward channel upstream, a 2D impeller with a vaneless diffuser and a constant cross section volute downstream constitute the basic geometry. Several diffuser geometries with different widths, pinch shapes, diffusion ratios were tested. Test results and conclusions are shown in the paper in terms of critical diffuser inlet flow angles, flow coefficients at stall inception and stage working ranges. The main task of the present work is to increase the knowledge and the amount of available data to characterize rotating stall phenomena, in particular for very narrow stages.

CFD Applications to Industrial Centrifugal Compressor Design

2002 ◽  
Author(s):  
Andrea Arnone ◽  
Duccio Bonaiuti ◽  
Paolo Boncinelli ◽  
Mirco Ermini ◽  
Alberto Milani ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Experimental Tests ◽  
Computational Procedure ◽  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Geometrical Parameters ◽  
Future Design ◽  
Numerical Predictions ◽  
The Impact

The aerodynamic redesign of an industrial transonic centrifugal impeller by means of CFD techniques is presented here. The computational procedure was validated by comparing numerical predictions of efficiency and work input coefficient to data from experimental tests on two different typologies of impellers: a low flow coefficient subsonic radial impeller and a high flow coefficient one. Three–dimensional, fully viscous computations were used to investigate the transonic impeller aerodynamic performance in terms of both the characteristic curves and details of the flow structure, suggesting possible improvements in the design. In order to standardize the redesign process of 3D impellers, a number of geometrical parameters, capable of describing the main features of the geometry, were identified. The original configuration was modified by varying the values of such parameters, and the impact of changes was assessed by means of 3D computations. As a result, the designer would be able to recognize which parameters have greater influence, and understand the physical effect of each change. This made it possible to establish some design rules to be exploited in future design processes.

scholarly journals On-Body Characterization of Planar Differential Antennas for Multiple, Wide, and Narrow Bands

2016 ◽  
Vol 2016 ◽  
pp. 1-9
Author(s):  
Luigi Vallozzi ◽  
Domenico Pepe ◽  
Thijs Castel ◽  
Hendrik Rogier ◽  
Domenico Zito
Keyword(s):  
Human Body ◽  
Ad Hoc ◽  
Low Cost ◽  
Experimental Tests ◽  
Body Measurements ◽  
Antenna Performance ◽  
Sensing Applications ◽  
The Impact ◽  
Narrow Bands

This paper reports the results of the on-body experimental tests of a set of four planar differential antennas, originated by design variations of radiating elements with the same shape and characterized by the potential for covering wide and narrow bands. All the antenna designs have been implemented on low-cost FR4 substrate and characterized experimentally through on-body measurements. The results show the impact of the proximity to the human body on antenna performance and the opportunities in terms of potential coverage of wide and narrow bands for future ad hoc designs and implementations through wearable substrates targeting on-body and off-body communication and sensing applications.

scholarly journals Numerical Investigation on the Optimum Thermal Design of the Shape and Geometric Parameters of Microchannel Heat Exchangers with Cavities

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 721
Author(s):  
Haiwang Li ◽  
Yujia Li ◽  
Binghuan Huang ◽  
Tiantong Xu
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Flow Resistance ◽  
Stokes Equations ◽  
Geometric Parameters ◽  
Thermal Design ◽  
Low Flow ◽  
High Heat Transfer ◽  
The Impact

Due to the large surface-area-to-volume ratio, microchannel heat exchangers have a higher heat transfer rate compared with traditional scale heat exchangers. In this study, the optimum microchannel cavity with high heat transfer and low flow resistance is designed to further improve microchannel exchangers’ thermal performance. A three-dimensional laminar flow model, consisting of Navier–Stokes equations and an energy conservation equation is solved and the conjugate heat transfer between the silicon basement and deionized water is taken into consideration. The impact of the shape, aspect ratio, size and spacing of the cavity on the thermal performance of microchannel exchangers are numerically investigated, respectively. The results indicated that the cavity on the sidewall can enhance heat transfer and reduce flow resistance simultaneously, and cavities with a relatively small expansion angle and streamlined edge could enhance thermal performance the most. Based on the conclusions, a new cavity shape is proposed, and the simulation results verify its excellent thermal performance as expected. Furthermore, investigation is performed to figure out the optimum design of the new cavity and the optimal geometric parameters of the cavity under different flow conditions have been obtained in principle for microchannel exchangers’ design.

The Characteristics of Rotating Instabilities in Low Pressure Steam Turbines at Low Volume Flow Operation

2015 ◽  
Author(s):  
Roland Sigg ◽  
Timothy Rice
Keyword(s):  
Renewable Energy Sources ◽  
Low Pressure ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Low Flow ◽  
Small Scale ◽  
Steam Turbines ◽  
Original Design ◽  
Low Load

For flexible operation steam turbines may operate occasionally at low load. Operation away from the original design regime looks set to be an increasing trend mainly due to the presence of intermittently available renewable energy sources in the grid. This paper sets out an approach for considering low flow effects on turbine designs. At low load operating conditions rotating instabilities (RIS) can occur in the rear stages of LP steam turbines. The instabilities are comparable in many ways to rotating stall in compressors. Ideally the turbine blade natural frequencies should be designed to avoid the frequencies generated by the RIS system. The characteristics of RIS systems were experimentally investigated to understand the dependency with both flow coefficient and exhaust configuration. Correlations have been developed to characterize the dynamic pressure amplitudes and the fractional speed of the RIS moving around the wheel. The presented correlation based method is shown calibrated for a specific blade design. Two different test rigs provide the basis for the work presented. A low pressure model steam turbine provided detailed information for key blade/exhaust combinations. A simplified small scale air turbine was used to provide additional input for the behavior with alternative exhaust back wall position. Observations of the characteristic RIS behavior from model turbine tests are set in context with observed changes in the flow field.

Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1995 ◽  
Vol 117 (4) ◽  
pp. 585-592 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncˇl
Keyword(s):  
Development Program ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Disk Friction ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development program for centrifugal compressors are presented. Six-stage configurations with low flow coefficient were tested. The stages had channel width parameter b2/D2 = 0.01 and 0.03. For each value of the width parameter, three different impellers with inlet hub to outlet diameter ratio do/D2 = 0.3, 0.4, and 0.5 were designed. Test rig, instrumentation, and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing, and disk friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with deswirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

scholarly journals Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1994 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncl
Keyword(s):  
Rotating Stall ◽  
Development Programme ◽  
Diameter Ratio ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development programme for centrifugal compressors are presented. Six stage configurations with low flow coefficient were tested. The stages had channel width parameter bo/D2=0.01 and 0.03. For each value of the width parameter three different impellers with inlet hub to outlet diameter ratio do/D2=0.3, 0.4 and 0.5 were designed. Test rig, instrumentation and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing and disc friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with de-swirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

Efficiency improvement of regenerative pump using blade profile modification: Experimental study

2018 ◽  
Vol 233 (3) ◽  
pp. 448-455 ◽  
Author(s):  
J Nejad ◽  
A Riasi ◽  
A Nourbakhsh
Keyword(s):  
Experimental Study ◽  
Experimental Tests ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Impeller Blade ◽  
Profile Modification ◽  
Compact Size ◽  
Curved Blade ◽  
Regenerative Flow

Regenerative flow pump is a kind of turbomachine with the ability to generate high heads at relatively low flow rates. Despite having low hydraulic efficiency, regenerative pumps have found many applications in industries due to their simplicity, compact size, low manufacturing costs, and low specific speed. In this paper, an experimental study has been carried out to investigate the influence of impeller blade change on the performance of regenerative pump. To this end, the straight radial blades were changed to curved blades with the same inlet/outlet angles. Three forward curved blade impellers as well as straight radial blade impeller were designed and manufactured. Since the regenerative pump comply with the affinity laws, the results of experimental tests were expressed in nondimensional coefficients. The results showed that by increasing the blade angle to 10°, the efficiency increased and at higher blade angles of 30° and 50°, the efficiency decreased for all flow conditions. The best angle was obtained about 15° by curve fitting to the experimental data at the design flow coefficient.

scholarly journals Mathematical Modeling and Characteristic Analysis of the Vertical Stiffness for Railway Vehicle Air Spring System

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Liufeng Xu
Keyword(s):  
Experimental Tests ◽  
Geometric Parameters ◽  
Railway Vehicle ◽  
Characteristic Analysis ◽  
Air Spring ◽  
Vertical Stiffness ◽  
Stiffness Model ◽  
Spring System ◽  
Stiffness Characteristics ◽  
The Impact

Establishing a correct and reliable vertical stiffness model has an important significance on reproducing the characteristics of an air spring system. In this paper, a dynamic vertical stiffness model is developed based on thermodynamics and fluid dynamics, and geometric parameters are identified by an approximate analytical method. Meanwhile, experimental tests are performed to verify the accuracy and reliability of the proposed model. Furthermore, the impact of geometric parameters on the vertical stiffness characteristics is discussed through a sensitivity analysis. The conclusions show that the dynamic vertical stiffness model can well characterize the dynamic characteristics of the air spring system, which provides a theoretical basis for the optimal design of air spring parameters and the study of mechanical properties.

Numerical Investigation of Effects of Different Hub Tip Diameter Ratios on Aerodynamic Performance of Single Shaft Multistage Centrifugal Compression Systems

2012 ◽  
Author(s):  
Thomas Ceyrowsky ◽  
Andre Hildebrandt
Keyword(s):  
Characteristic Curve ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Stage ◽  
Daily Routine ◽  
Stage Design ◽  
Design Point ◽  
Thermodynamic Behaviour ◽  
The Impact

Regarding industrial centrifugal compressors in single shaft design, different configurations with e.g. varying numbers of stages or diverse circumferential speeds, necessitate different shaft diameters. Thus the application of impellers with different hub/tip ratios (dh/d2) is daily routine in industrial practice. Increasing hub/tip ratio leads to higher radii and therefore higher relative speeds, to a reduction in the impeller’s meridional length and hence more rapid diffusion, and to a sharper bending from axial to radial direction. In this paper the impact of hub/tip ratio on stage performance is investigated for three different centrifugal compressor stages, by steady state CFD-calculations. The hub/tip ratio is varied between 0.325 < dh/d2 < 0.45. The relation between design stage flow coefficient and hub/tip ratio is also analysed, both at design and off-design. Thermodynamic behaviour is assessed by 1D-data and also by the investigation of secondary flow features. The current analysis shows, that hub/tip ratio’s influence on characteristics is strongly dependent on the particular stage’s design flow coefficient and circumferential Mach-Number. Increasing a high flow stage’s hub/tip ratio is shown to decrease peak efficiency as well, as to limit the operating range. On the contrary, in case of a low flow stage, design point efficiency is hardly affected, but the characteristic curve is tilted around design point, by applying a different hub/tip ratio. However severity of hub/tip ratio’s impact on thermodynamic behaviour shows to decrease together with stage design flow coefficient.

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