Effect of Leakage Flows on the Performance of a Family of Inline Centrifugal Compressors

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Hamid Hazby ◽  
Michael Casey ◽  
Luboš Březina
Keyword(s):  
Flow Coefficient ◽  
Leakage Flows ◽  
Geometrical Features ◽  
Work Input ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Work ◽  
The Impact ◽  
Compressor Efficiency ◽  
Stage Efficiency ◽  
Good Agreement

The impact of the hub and shroud leakage flows on the compressor efficiency has been investigated for four compressor stages with flow coefficients of 0.017, 0.0265, 0.063, and 0.118 belonging to a family of centrifugal compressor stages, designed for process compressor applications. A very good agreement was observed between the measured and predicted performance when the detailed geometrical features were included in the calculations. The computational fluid dynamics (CFD) calculations indicated that addition of leakage cavities and leakage flows resulted in about 3% drop in stage polytropic efficiency for the highest flow coefficient stage. The detrimental effect of leakages increased to about 8% for the lowest flow coefficient stage investigated here. The increase in the compressor work input due to the disc windage and the leakage recirculation was estimated from the CFD calculations and compared with values obtained using 1D methods, showing a very good agreement between the two. The impact of parasitic losses on compressor efficiency has been investigated and the contribution of various loss sources to the stage efficiency is discussed.

Optimizing a Suction Channel to Improve Performance of a Centrifugal Compressor Stage

2010 ◽  
Author(s):  
Manabu Yagi ◽  
Takanori Shibata ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Masanori Tanaka ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Dominant Design ◽  
Improvement Effect ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Flow ◽  
Stage Efficiency

Design parameters for a suction channel of process centrifugal compressors were investigated, and an optimizing method to improve efficiency by using the new design parameters was proposed. Both pressure loss and circumferential flow distortion in the suction channel were evaluated by using computational fluid dynamics (CFD). The main dimensions, which had a large influence on pressure loss and circumferential flow distortion, were identified by using design of experiments (DOE). Next, the passage sectional area ratios Ac/Ae, Ae/As, and Ac/As were found to be the dominant design parameters for the pressure loss and circumferential flow distortion, where Ac, Ae and As are passage sectional areas for the casing upstream side, casing entrance and impeller eye, respectively. Then the shape of the suction channel was optimized using Ac/Ae, Ae/As, and Ac/As. Finally, to evaluate the improvement effect of optimizing the values of Ac/Ae, Ae/As, and Ac/As on compressor stage performance, a base suction channel and an optimized type of suction channel were manufactured and tested. The design suction flow coefficient was 0.1 and the peripheral Mach number was 0.78. Test results showed that the optimized suction channel achieved 3.8% higher stage efficiency than the base one while maintaining the overall operating range from surge to choke. The method for optimizing suction channels by using the three described design parameters was concluded to be very effective for improving the stage efficiency.

Characterizing the Influence of Impeller Exit Recirculation on Centrifugal Compressor Work Input

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Charles Stuart ◽  
Stephen Spence ◽  
Dietmar Filsinger ◽  
Andre Starke ◽  
Sung In Kim
Keyword(s):  
Performance Prediction ◽  
Pressure Rise ◽  
Flow Region ◽  
Single Equation ◽  
Flow Coefficient ◽  
Physical Treatment ◽  
Recirculating Flow ◽  
Work Input ◽  
Stage Performance ◽  
The Impact

Impeller recirculation is a loss which has long been considered in one-dimensional (1D) modeling; however, the full extent of its impact on stage performance has not been analyzed. Recirculation has traditionally been considered purely as a parasitic (or external) loss, i.e., one which absorbs work but does not contribute to total pressure rise across the stage. Having extensively analyzed the impact of recirculation on the impeller exit flow field, it was possible to show that it has far-reaching consequences beyond that of increasing total temperature. The overall aim of this package of work is to apply a much more physical treatment to the impact of impeller exit recirculation (and the aerodynamic blockage associated with it) and hence realize an improvement in the 1D stage performance prediction of a number of turbocharger centrifugal compressors. The factors influencing the presence and extent of this recirculation are numerous, requiring detailed investigations to successfully understand its sources and to characterize its extent. A combination of validated three-dimensional computational fluid dynamics (CFD) data and gas stand test data for six automotive turbocharger compressor stages was employed to achieve this aim. In order to capture the variation of the blockage presented to the flow with both geometry and operating condition, an approach involving the impeller outlet to inlet area ratio and a novel flow coefficient term were employed. The resulting data permitted the generation of a single equation to represent the impeller exit blockage levels for the entire operating map of all the six compressor stages under investigation. With an understanding of the extent of the region of recirculating flow realized and the key drivers leading to its creation identified, it was necessary to comprehend how the resulting blockage influenced compressor performance. Consideration was given to the impact on impeller work input through modification of the impeller exit velocity triangle, incorporating the introduction of the concept of an “aerodynamic meanline” to account for the reduction in the size of the active flow region due to the presence of blockage. The sensitivity of the stage to this change was then related back to the level of backsweep applied to the impeller. As a result of this analysis, the improvement in the 1D performance prediction of the six compressor stages is demonstrated. In addition, a number of design recommendations are presented to ensure that the detrimental effects associated with the presence of impeller exit recirculation can be minimized.

scholarly journals Novel high-pressure turbine purge control features for increased stage efficiency

2017 ◽  
Vol 1 ◽  
pp. 68MK5V ◽  
Author(s):  
Rainer Schädler ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Gregor Schmid ◽  
Tilmann auf dem Kampe ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Gas Turbines ◽  
High Pressure Turbine ◽  
Axial Turbine ◽  
Seal Design ◽  
Geometrical Features ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

AbstractRim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.

Characterising the Influence of Impeller Exit Recirculation on Centrifugal Compressor Work Input

2017 ◽  
Author(s):  
Charles Stuart ◽  
Stephen Spence ◽  
Dietmar Filsinger ◽  
Andre Starke ◽  
Sung In Kim
Keyword(s):  
Performance Prediction ◽  
Pressure Rise ◽  
Flow Region ◽  
Single Equation ◽  
Flow Coefficient ◽  
Physical Treatment ◽  
Recirculating Flow ◽  
Work Input ◽  
Stage Performance ◽  
The Impact

Impeller recirculation is a loss which has long been considered in 1 D modelling, however the full extent of its impact on stage performance has not been analysed. Recirculation has traditionally been considered purely as a parasitic (or external) loss, i.e. one which absorbs work but does not contribute to total pressure rise across the stage. Having extensively analysed the impact of recirculation on the impeller exit flow field, it was possible to show that it has far reaching consequences beyond that of increasing total temperature. The overall aim of this package of work was to apply a much more physical treatment to the impact of impeller exit recirculation (and the aerodynamic blockage associated with it), and hence realise an improvement in the 1 D stage performance prediction of a number of turbocharger centrifugal compressors. The factors influencing the presence and extent of this recirculation are numerous, requiring detailed investigations to successfully understand its sources and to characterise its extent. A combination of validated 3 D Computational Fluid Dynamics (CFD) data and gas stand test data for six automotive turbocharger compressor stages was employed to achieve this aim. In order to capture the variation of the blockage presented to the flow with both geometry and operating condition, an approach involving the impeller outlet to inlet area ratio and a novel flow coefficient term were employed. The resulting data permitted the generation of a single equation to represent the impeller exit blockage levels for the entire operating map of all six compressor stages under investigation. With an understanding of the extent of the region of recirculating flow realised, and the key drivers leading to its creation identified, it was necessary to comprehend how the resulting blockage influenced compressor performance. Consideration was given to the impact on impeller work input through modification of the impeller exit velocity triangle, incorporating the introduction of the concept of an “aerodynamic meanline” to account for the reduction in the size of the active flow region due to the presence of blockage. The sensitivity of the stage to this change was then related back to the level of backsweep applied to the impeller. As a result of this analysis, the improvement in the 1 D performance prediction of the six compressor stages is demonstrated. In addition, a number of design recommendations are presented to ensure that the detrimental effects associated with the presence of impeller exit recirculation can be minimised.

scholarly journals Numerical Investigation on Flow Field Distribution of Eccentric Compressors Based on Steady and Unsteady CFD Methods

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6081
Author(s):  
Chao Jiang ◽  
Jun Hu ◽  
Jiayu Wang ◽  
Longteng Cong
Keyword(s):  
Flow Field ◽  
Field Distribution ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Characteristic Line ◽  
Axial Compressors ◽  
Ansys Cfx ◽  
Engine Compressor ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The tip clearance has an important effect on the performance of an engine compressor. While the impact of tip clearance on a concentric compressor has been widely explored in previous research, the flow field distribution of an eccentric compressor has only been minimally explored. Both the steady and unsteady computational fluid dynamics (CFD) methods have been widely used in the studies of concentric axial-compressors, and they have similar simulation results in terms of flow field. However, they have been rarely applied to axial-compressors with non-uniform tip clearance to investigate their flow field. In this paper, ANSYS CFX is used as CFD software, and both steady and unsteady CFD methods are applied to study a single rotor of ROTOR67 to investigate the compressor characteristic line and flow field under different eccentricity conditions. The results show that non-uniform tip clearance creates a non-uniform flow field at the inlet and tip regions over the whole operating range. The circumferential position where the flow coefficient and the axial velocity are the smallest occurs at a position close to the maximum tip clearance and is located on the side deviating toward the direction of rotation of the rotor. Compared with steady CFD, unsteady CFD has better predictive capability for the flow field distribution in axial compressors with non-uniform tip clearance.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

scholarly journals Measuring Hydrometeors Using a Precipitation Microphysical Characteristics Sensor: Sampling Effect of Different Bin Sizes on Drop Size Distribution Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xichuan Liu ◽  
Taichang Gao ◽  
Yuntao Hu ◽  
Xiaojian Shu
Keyword(s):  
Drop Size ◽  
Rain Rate ◽  
Monte Carlo Model ◽  
Rain Gauge ◽  
Sampling Schemes ◽  
Distribution Parameters ◽  
Optimum Sampling ◽  
Simulation Results ◽  
The Impact ◽  
Good Agreement

In order to improve the measurement of precipitation microphysical characteristics sensor (PMCS), the sampling process of raindrops by PMCS based on a particle-by-particle Monte-Carlo model was simulated to discuss the effect of different bin sizes on DSD measurement, and the optimum sampling bin sizes for PMCS were proposed based on the simulation results. The simulation results of five sampling schemes of bin sizes in four rain-rate categories show that the raw capture DSD has a significant fluctuation variation influenced by the capture probability, whereas the appropriate sampling bin size and width can reduce the impact of variation of raindrop number on DSD shape. A field measurement of a PMCS, an OTT PARSIVEL disdrometer, and a tipping bucket rain Gauge shows that the rain-rate and rainfall accumulations have good consistencies between PMCS, OTT, and Gauge; the DSD obtained by PMCS and OTT has a good agreement; the probability of N0, μ, and Λ shows that there is a good agreement between the Gamma parameters of PMCS and OTT; the fitted μ-Λ and Z-R relationship measured by PMCS is close to that measured by OTT, which validates the performance of PMCS on rain-rate, rainfall accumulation, and DSD related parameters.

scholarly journals Waterfall Algorithm as a tool of investigation the geometrical features of granular porous media

2021 ◽  
Author(s):  
Wojciech Sobieski
Keyword(s):  
Particle Size ◽  
Porous Media ◽  
Lattice Boltzmann ◽  
Granular Media ◽  
Density Ratio ◽  
Geometrical Features ◽  
Granular Porous Media ◽  
Collision Density ◽  
Boltzmann Method ◽  
The Impact

AbstractThe paper describes the so-called Waterfall Algorithm, which may be used to calculate a set of parameters characterising the spatial structure of granular porous media, such as shift ratio, collision density ratio, consolidation ratio, path length and minimum tortuosity. The study is performed for 1800 different two-dimensional random pore structures. In each geometry, 100 individual paths are calculated. The impact of porosity and the particle size on the above-mentioned parameters is investigated. It was stated in the paper, that the minimum tortuosity calculated by the Waterfall Algorithm cannot be used directly as a representative tortuosity of pore channels in the Kozeny or the Carman meaning. However, it may be used indirect by making the assumption that a unambiguous relationship between the representative tortuosity and the minimum tortuosity exists. It was also stated, that the new parameters defined in the present study are sensitive on the porosity and the particle size and may be therefore applied as indicators of the geometry structure of granular media. The Waterfall Algorithm is compared with other methods of determining the tortuosity: A-Star Algorithm, Path Searching Algorithm, Random Walk technique, Path Tracking Method and the methodology of calculating the hydraulic tortuosity based on the Lattice Boltzmann Method. A very short calculation time is the main advantage of the Waterfall Algorithm, what meant, that it may be applied in a very large granular porous media.

scholarly journals The Problem of Accounting for Heat Exchange between the Flow and the Flow Part Surfaces When Modeling a Viscous Flow in Low-Flow Stages of a Centrifugal Compressor

2020 ◽  
Vol 10 (24) ◽  
pp. 9138
Author(s):  
Sergey Kartashov ◽  
Yuri Kozhukhov ◽  
Vycheslav Ivanov ◽  
Aleksei Danilishin ◽  
Aleksey Yablokov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Centrifugal Compressor ◽  
Calculation Model ◽  
Flow Coefficient ◽  
Low Flow ◽  
Relative Width ◽  
Adiabatic Wall ◽  
Flow Part ◽  
Computational Fluid Dynamics Cfd

In this paper, we review the problem of accounting for heat exchange between the flow and the flow part surfaces when creating a calculation model for modeling the workflow process of low-flow stages of a centrifugal compressor using computational fluid dynamics (CFD). The objective selected for this study was a low-flow intermediate type stage with the conditional flow coefficient Փ = 0.008 and the relative width at the impeller exit b2/D2 = 0.0133. We show that, in the case of modeling with widespread adiabatic wall simplification, the calculated temperature in the gaps between the impeller and the stator elements is significantly overestimated. Modeling of the working process in the flow part was carried out with a coupled heat exchanger, as well as with simplified accounting for heat transfer by setting the temperatures of the walls. The gas-dynamic characteristics of the stage were compared with the experimental data, the heat transfer influence on the disks friction coefficient was estimated, and the temperature distributions in the gaps between disks and in the flow part of the stage were analyzed. It is shown that the main principle when modeling the flow in low-flow stage is to ensure correct temperature distribution in the gaps.

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