Investigation of an Asymmetric Double Entry Centrifugal Compressor With Different Radial Impellers Matching for a Wide Operating Range

2015 ◽  
Author(s):  
Lei Jing ◽  
Ce Yang ◽  
Wangxia Wu ◽  
Shan Chen
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Mode Conversion ◽  
Critical Mass ◽  
Operating Mode ◽  
Operating Characteristics ◽  
Operating Range ◽  
Stable Operating ◽  
Parallel Mode ◽  
Power Capability

The work presented here investigates the impeller matching characteristics and widens the stable operating range of front and rear impellers for an asymmetric entry double sided centrifugal compressor. A numerical approach is employed to analyze the operating characteristics of front and rear impellers, and a strategy to widen the stable operating range of double sided compressor is presented. Firstly, the performance curves of a double sided centrifugal compressor are obtained by simulating the operation of the whole-stage compressor. The result shows that the compressor operating mode switches from parallel mode to single impeller mode automatically with the decrease of the mass flow. Thus, the stable operating range of the compressor is limited. Second, the simulation of a simplified double sided compressor is conducted to reveal the mechanism of the compressor operating mode conversion. It is found that the essential reason for the conversion of the compressor operating mode is the total pressure difference between the front and rear impeller inlets. A proper increase of the rear impeller radii is helpful for improving the impeller power capability, which enables the front and rear impeller to obtain a superior matching relationship in a wider operating range and widens the stable operating range of the compressor. Furthermore, by analyzing the respective performance characteristic curves in various calculation cases, there is a critical mass flow value between the front and rear impellers for compressors with the same flow capability. When one side impeller mass flow is below the critical value, with further decrease of the flow, the pressure ratio characteristic curve of this side rises and enters the stall zone gradually. Thus, the operating mode is converted from parallel mode to single mode. This result further explains the mechanism for extending the stable operating range of a double sided compressor in a wider scope.

Numerical Investigation of an Asymmetric Double Suction Centrifugal Compressor With Different Backswept Angle Matching for a Wide Operating Range

2017 ◽  
Author(s):  
Hanzhi Zhang ◽  
Dazhong Lao ◽  
Longyu Wei ◽  
Ce Yang ◽  
Mingxu Qi
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Flow Distribution ◽  
Operating Mode ◽  
Mode Transition ◽  
Distribution Characteristics ◽  
Operating Range ◽  
Stable Operating ◽  
Angle Difference ◽  
Matching Models

The work presented here investigates the characteristics of the different impeller backswept angle matchings for a wide stable operating range in an asymmetric double suction centrifugal compressor. The numerical simulation was employed to investigate the influence of different backswept angle matchings on the stable operating range. The aim is to propose a proper change of the backswept angle matching between two impeller sides to improve the impeller power capability and mass flow distribution, furthermore, to delay the operating mode transition and widen the stable operating range of the compressor. Firstly, the method to determine the optimum backswept angle matching obtained by the theory calculation. Then, three matching models were proposed and analyzed in detail. In three matching models, the backswept angle differences between the front and rear impeller side are 0°, 10° and 20°, respectively. The analysis mainly focused on the influence of the different backswept angle matchings on the compressor flow field characteristics and the mass flow distribution characteristics. The results show that the change of the impeller backswept angle matching can improve the mass flow distribution characteristics for two impeller sides and further reduce the stall mass flow rate of the double suction compressor. The model that the backswept angle difference is 10° can delay the operating mode transition and reduce the stall mass flow of the double suction compressor. The model that the backswept angle difference is 20° can also reduce the stall mass flow and finally enable the front impeller into the stall condition. Therefore, the proper change of the backswept angle matching can achieve the purpose of reducing the stall mass flow and widening the operating range for the double suction centrifugal compressor.

An Investigation of Centrifugal Compressor Stability Enhancement Using a Novel Vaned Diffuser Recirculation Technique

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Lee Galloway ◽  
Daniel Rusch ◽  
Stephen Spence ◽  
Klemens Vogel ◽  
René Hunziker ◽  
...  
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Vaned Diffuser ◽  
Casing Treatment ◽  
Operating Range ◽  
Stable Operating ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Casing Treatments

The main centrifugal compressor performance criteria are pressure ratio, efficiency, and wide flow range. The relative importance of these criteria, and therefore the optimum design balance, varies between different applications. Vaned diffusers are generally used for high-performance applications as they can achieve higher efficiencies and pressure ratios, but have a reduced operating range, in comparison to vaneless diffusers. Many impeller-based casing treatments have been developed to enlarge the operating range of centrifugal compressors over the last decades but there is much less information available in open literature for diffuser focused methods, and they are not widely adopted in commercial compressor stages. The development of aerodynamic instabilities at low mass flow rate operating conditions can lead to the onset of rotating stall or surge, limiting the stable operating range of the centrifugal compressor stage. More understanding of these aerodynamic instabilities has been established in recent years. Based on this additional knowledge, new casing treatments can be developed to prevent or suppress the development of these instabilities, thus increasing the compressor stability at low mass flow rates. This paper presents a novel vaned diffuser casing treatment that successfully increased the stable operating range at low mass flow rates and high pressure ratios. Detailed experimental measurements from a high pressure ratio turbocharger compressor stage combined with complementary CFD simulations were used to examine the effect of the new diffuser casing treatment on the compressor flow field and led to the improvement in overall compressor stability. A detailed description of how the new casing treatment operates is presented within the paper.

scholarly journals Stall Margin Improvement in a Centrifugal Compressor through Inducer Casing Treatment

2016 ◽  
Vol 2016 ◽  
pp. 1-19
Author(s):  
V. V. N. K. Satish Koyyalamudi ◽  
Quamber H. Nagpurwala
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Treatment Technique ◽  
Centrifugal Compressors ◽  
Stall Margin ◽  
Casing Treatment ◽  
Operating Range ◽  
Stable Operating ◽  
Stall Margin Improvement

The increasing trend of high stage pressure ratio with increased aerodynamic loading has led to reduction in stable operating range of centrifugal compressors with stall and surge initiating at relatively higher mass flow rates. The casing treatment technique of stall control is found to be effective in axial compressors, but very limited research work is published on the application of this technique in centrifugal compressors. Present research was aimed to investigate the effect of casing treatment on the performance and stall margin of a high speed, 4 : 1 pressure ratio centrifugal compressor through numerical simulations using ANSYS CFX software. Three casing treatment configurations were developed and incorporated in the shroud over the inducer of the impeller. The predicted performance of baseline compressor (without casing treatment) was in good agreement with published experimental data. The compressor with different inducer casing treatment geometries showed varying levels of stall margin improvement, up to a maximum of 18%. While the peak efficiency of the compressor with casing treatment dropped by 0.8%–1% compared to the baseline compressor, the choke mass flow rate was improved by 9.5%, thus enhancing the total stable operating range. The inlet configuration of the casing treatment was found to play an important role in stall margin improvement.

An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Lee Galloway ◽  
Stephen Spence ◽  
Sung In Kim ◽  
Daniel Rusch ◽  
Klemens Vogel ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Stall Inception ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Stable Operating ◽  
The Stability ◽  
Circumferential Pressure

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.

Design and Performance Analysis of a Supercritical CO2 Centrifugal Compressor With Variable Geometry

2021 ◽  
Author(s):  
Gang Fan ◽  
Kang Chen ◽  
Shaoxiong Zheng ◽  
Yang Du ◽  
Yiping Dai ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Optimization Design ◽  
High Efficiency ◽  
Superior Performance ◽  
Variable Geometry ◽  
Power Cycles ◽  
Operating Range ◽  
Stable Operating ◽  
And Performance ◽  
Geometry Method

Abstract The supercritical carbon dioxide (SCO2) Brayton cycle is one of the most promising power cycles due to its high efficiency, compactness and environmentally friendliness. The centrifugal compressor is a key component of small and medium SCO2 Brayton cycles, and its efficiency has a significant impact on the cycle efficiency. Since the required electric load of power cycles always fluctuates over the year, the SCO2 compressor will operate away from its design point and the narrow stable operating range of a compressor is always a restriction. In this paper, the variable-geometry method, which refers to the combination of a variable inlet-guide-vanes and variable diffuser vanes is proposed for the operating range extension of SCO2 compressors. A set of one-dimensional (1D) loss correlations has been found to accurately predict various losses of the SCO2 compressor components. Based on the 1D thermodynamic model, two programs with internal MATLAB codes coupled with the NIST REFPROP database have been developed for preliminary optimization design and off-design performance predictions of the variable geometry SCO2 compressor. The contributions from the variable-inlet prewhirl and variable diffuser vanes to the shifts of the surge line and choke line are discussed in this paper. The results show the variable-geometry SCO2 compressor has a superior performance at off-design conditions and a wider operating range.

Active Stabilization of Surge in an Axicentrifugal Turboshaft Engine

1999 ◽  
Vol 122 (3) ◽  
pp. 485-493 ◽  
Author(s):  
E. B. Nelson ◽  
J. D. Paduano ◽  
A. H. Epstein
Keyword(s):  
Mass Flow ◽  
Acoustic Mode ◽  
Open Loop ◽  
Control Law ◽  
Duct Acoustics ◽  
Operating Range ◽  
Stable Operating ◽  
Active Stabilization ◽  
Surge Control ◽  
Turboshaft Engine

Active stabilization of surge was implemented on an Allied Signal LTS-101 axicentrifugal gas producer, reducing the surging mass flow by 1 percent, for an operating range increase of 11 percent. Control was achieved using high-response sensors in the inlet and diffuser throat, coupled to actuators that injected air near the diffuser throat. System identification and modeling indicate that a classical surge-type eigenmode and an eigenmode associated with engine duct acoustics dominate the engine’s input–output properties. The surge eigenmode’s stability determines the open-loop surge mass flow. A robust linear controller with three inputs and one output stabilized this eigenmode without destabilizing the acoustic mode. The controller facilitated a 1 percent reduction in surging mass flow at 95 percent N1 corrected; this increases the engine’s choke to surge stable operating range by 11 percent. This paper elucidates the measured unsteady presurge behavior of the engine, and outlines a systematic procedure for surge control law development. [S0889-504X(00)01803-1]

Numerical Analysis of an Alternate Stall in a Radial Vaned Diffuser

2016 ◽  
Author(s):  
E. Benichou ◽  
I. Trébinjac
Keyword(s):  
Flow Pattern ◽  
Flow Structure ◽  
Channel Flow ◽  
Mass Flow ◽  
Computational Domain ◽  
Flow Rates ◽  
Operating Range ◽  
Stable Operating ◽  
Mass Flow Rates ◽  
Low Mass

The flow structure in the radial diffuser of a centrifugal compressor is analyzed from steady and unsteady Reynolds-Averaged Navier Stokes (RANS) simulations performed at one rotation speed for which two stable operating ranges separated by an unstable zone have been experimentally experienced. Below a given mass flow rate, close to the peak efficiency point, phase-lagged single-passage simulations do not converge properly anymore. A low frequency appears in the CFD, which cannot be associated with any physical phenomenon. The computational domain is then extended, so that several passages of both the impeller and the diffuser are taken into account. At intermediate mass flow rates, an unstable operating range exists and simulations cannot converge properly either. Nevertheless, if the compressor is further throttled, another stable operating range is obtained at low mass flow rates. The flow structure in that stable operating range is rather unusual: an internal periodicity emerges inside the radial diffuser, involving a two-channel flow pattern. This two-channel flow pattern is found to be stable and fixed in time. Moreover, the phase shift between two adjacent channel pairs happens to be constant. This indicates that a new space – time periodicity is established at low mass flow rates, which involves groups of two passages in the radial diffuser. It is confirmed thanks to a new phase-lagged simulation including one impeller passage and two diffuser passages which shows a good convergence and which gives the same results, both in terms of performance and flow physics.

Casing Treatment of Centrifugal Compressors

2015 ◽  
Author(s):  
Jisha Noushad ◽  
Anand Babu Dhamarla ◽  
Pavan Kumar
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Fluctuations ◽  
Centrifugal Compressors ◽  
Flow Rates ◽  
Casing Treatment ◽  
Operating Range ◽  
Mass Flow Rates ◽  
Ported Shroud

The operating range of any compressor is controlled by Surge and Choke. Surge occurs at lower mass flow rates with large pressure fluctuations and flow reversals, while choke occurs at higher mass flow rates when the flow rate reaches the limit which compressor can discharge. Ported shroud is a cost effective casing treatment that can greatly improve operating range of centrifugal compressors. By removing the stagnant and reverse flow from shroud wall boundary-layer region and recirculating it to impeller inlet, it has been demonstrated that larger range of operability can be achieved without much loss on compressor efficiency. This paper demonstrates the improvement of a centrifugal compressor operational range with ported shroud configuration. A series of CFD simulations were carried out with open source centrifugal compressor geometry (NASA HPCC 4:1) to create performance characteristics/speed-lines. The CFD methodology and practices were validated by comparing the results with the experimental data. Performance evaluation of ported shroud configuration is done with respect to solid shroud. Ported shroud compressor is proven to give higher choke mass flow and also a better surge margin compared to the Solid shroud model. The phenomena of in-flowing and out-flowing port have also been demonstrated. Emphasis was given to understand how ported shroud helps to achieve a better performance. A design optimization study has also been carried out in order to establish the optimum ported shroud configuration. Design parameter such as port location has been selected and the effect of this parameter on the performance of the compressor is studied using CFD. Optimum port geometry was proposed.

3D Multi-Disciplinary Inverse Design Based Optimization of a Centrifugal Compressor Impeller

2014 ◽  
Author(s):  
Mehrdad Zangeneh ◽  
Fred Mendonça ◽  
Youngwon Hahn ◽  
Jack Cofer
Keyword(s):  
Response Surface ◽  
Centrifugal Compressor ◽  
Inverse Design ◽  
Design Parameters ◽  
Operating Range ◽  
Multi Objective ◽  
Development Times ◽  
Stable Operating ◽  
Compressor Impeller ◽  
3D Fea

Design of centrifugal compressors in different applications from industrial to turbochargers to aeroengine is subject to difficult multi-disciplinary ( aerodynamics and mechanical) and multipoint/multi-objective requirements. These multi-disciplinary and multi-point requirements have to be met by iterations between aerodynamics and mechanical design, leading to long development times and bottlenecks in the design process. In this paper, for the first time, a commercially available solution, compatible with industrial development times, is presented for 3D multi-disciplinary and multi-point design optimisation of turbomachinery blades. The methodology combines 3D inverse design method, automatic optimizers, 3D CFD and 3D FEA codes. The key aspect of the approach is to parameterise the 3D geometry through the blade loading distribution used in 3D inverse design code TURBOdesign1, which results in ability to access large part of design space with very few design parameters. The Design of Experiments method is used to generate a number of geometries which are then analysed by 3D CFD code STAR-CCM+ and 3D FEA code Abaqus. Different performance parameters related to aerodynamics (efficiency, stable operating range etc) and structural integrity (maximum principal stress, etc) are then evaluated. The data is then used to create a response surface. The validity and accuracy of the response surface is evaluated by CFD and FEA and then once confirmed a Multi-objective Genetic Algorithm is run on the response surface to explore the trade-offs between different design parameters, such as peak efficiency, stable operating range and mechanical stress. In this paper the methodology is applied to the redesign of the well-known Eckardt centrifugal compressor impeller.

An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

2017 ◽  
Author(s):  
Lee Galloway ◽  
Stephen Spence ◽  
Sung In Kim ◽  
Daniel Rusch ◽  
Klemens Vogel ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Stall Inception ◽  
Centrifugal Compressor Stage ◽  
Operating Range ◽  
Stable Operating ◽  
The Stability ◽  
Circumferential Pressure

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser. Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilising mechanism of the porous throat diffuser. The non-uniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure non-uniformity at various locations through the compressor stage and diffuser sub-component analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser and the stability limit is mainly governed by this element.

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