A Numerical Study on the Effect of Inter-Stage Water Injection in an Opposed-Setting-Two-Stage Centrifugal Compressor

2020 ◽  
Author(s):  
Ming Ni ◽  
Shaojuan Geng ◽  
Zuojun Wei ◽  
Xiaohua Gan
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Water Injection ◽  
Two Stage ◽  
Stall Margin ◽  
Injection Parameter ◽  
Insufficient Time ◽  
The Stability ◽  
The Right

Abstract Inter-stage water injection is currently a common method to reduce the compression work. In this paper, we evaluate the effect of this approach on an opposed-setting-two-stage centrifugal compressor which is designed for a small gas turbine numerically. The Eulerian-Lagrangian method is adopted to calculate the continuous flow field and discrete particle terms with the k-ε turbulence model. 6 water injection conditions are conducted to compare with the dry air condition. The performance curve shift to the right-up side, i.e. higher total pressure ratio, higher efficiency and larger choking mass flow. However, the larger the performance improvement gained by inter-stage injection, the worse the stability will be. Under the micro injection ratio (about 0.1%), the stall margin of the compressor is improved. Additionally, with a proper injection parameter, the loading in the diffuser can be reduced and promise a wider stall margin. Nevertheless, there still exists droplets at the outlet of the high-pressure diffuser because of the insufficient time for evaporation.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

Effect of Vaned Diffuser on a Modified Turbocharger Centrifugal Compressor Performance

2014 ◽  
Vol 663 ◽  
pp. 347-353
Author(s):  
Layth H. Jawad ◽  
Shahrir Abdullah ◽  
Zulkifli R. ◽  
Wan Mohd Faizal Wan Mahmood
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Width Ratio ◽  
Outlet Section ◽  
Suction Surface ◽  
Vaned Diffuser ◽  
Minimum Width

A numerical study that was made in a three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an automotive turbo charger. In order to study the influence of vaned diffuser meridional outlet section with a different width ratio of the modified centrifugal compressor. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between the compressor impeller along the vaned diffuser. The aerodynamic characteristics were compared under different meridional width ratio. In addition, the velocity vectors in diffuser flow passages, and the secondary flow in cross-section near the outlet of diffuser were analysed in detail under different meridional width ratio. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken using commercial software so-called ANSYS CFX, to predict numerically the performance charachteristics. The results were generated from CFD and were analysed for better understanding of the fluid flow through centrifugal compressor stage and as a result of the minimum width ratio the flow in diffuser passage tends to be uniformity. Moreover, the backflow and vortex near the pressure surface disappear, and the vortex and detachment near the suction surface decrease. Conclusively, it was observed that the efficiency was increased and both the total pressure ratio and static pressure for minimum width ratio are increased.

A Study of Influences of Inlet Total Pressure Distortions On Clearance Flow in an Axial Compressor

2021 ◽  
Author(s):  
Guoming Zhu ◽  
Xiaolan Liu ◽  
Bo Yang ◽  
Moru Song
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Stall Margin ◽  
Flow Cells ◽  
Static Pressure Distribution ◽  
Speed Flow ◽  
Clearance Flow ◽  
The Stability

Abstract The rotating distortion generated by upstream wakes or low speed flow cells is a kind of phenomenon in the inlet of middle and rear stages of an axial compressor. Highly complex inflow can obviously affect the performance and the stability of these stages, and is needed to be considered during compressor design. In this paper, a series of unsteady computational fluid dynamics (CFD) simulations is conducted based on a model of an 1-1/2 stage axial compressor to investigate the effects of the distorted inflows near the casing on the compressor performance and the clearance flow. Detailed analysis of the flow field has been performed and interesting results are concluded. The distortions, such as total pressure distortion in circumferential and radial directions, can block the tip region so that the separation loss and the mixing loss in this area are increased, and the efficiency and the total pressure ratio are dropped correspondingly. Besides, the distortions can change the static pressure distribution near the leading edge of the rotor, and make the clearance flow spill out of the rotor edge more easily under near stall condition, especially in the cases with co-rotating distortions. This phenomenon can be used to explain why the stall margin is deteriorated with nonuniform inflows.

scholarly journals On the Importance of the Influence of both Velocity and Aspect Ratios on the Occurrence of Bifurcation Phenomena within a Two-Sided Lid-Driven Enclosure

2015 ◽  
Vol 55 ◽  
pp. 160-172
Author(s):  
Fayçal Hammami ◽  
Nader Ben Cheikh ◽  
Brahim Ben Beya
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Numerical Results ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Left Wall ◽  
Driven Cavity ◽  
Aspect Ratios ◽  
The Stability ◽  
The Right

This paper deals with the numerical study of bifurcations in a two-sided lid driven cavity flow. The flow is generated by moving the upper wall to the right while moving the left wall downwards. Numerical simulations are performed by solving the unsteady two dimensional Navier-Stokes equations using the finite volume method and multigrid acceleration. In this problem, the ratio of the height to the width of the cavity are ranged from H/L = 0.25 to 1.5. The code for this cavity is presented using rectangular cavity with the grids 144 × 36, 144 × 72, 144 × 104, 144 × 136, 144 × 176 and 144 × 216. Numerous comparisons with the results available in the literature are given. Very good agreements are found between current numerical results and published numerical results. Various velocity ratios ranged in 0.01≤ α ≤ 0.99 at a fixed aspect ratios (A = 0.5, 0.75, 1.25 and 1.5) were considered. It is observed that the transition to the unsteady regime follows the classical scheme of a Hopf bifurcation. The stability analysis depending on the aspect ratio, velocity ratios α and the Reynolds number when transition phenomenon occurs is considered in this paper.

Forward Swept Rotor Studies in Multistage Fans With Inlet Distortion

2002 ◽  
Author(s):  
A. R. Wadia ◽  
P. N. Szucs ◽  
D. W. Crall ◽  
D. C. Rabe
Keyword(s):  
Pressure Ratio ◽  
Flow Distortion ◽  
Two Stage ◽  
Good Efficiency ◽  
Guide Vanes ◽  
Stall Margin ◽  
High Pressure Ratio ◽  
Inlet Distortion ◽  
Inlet Guide Vanes ◽  
Current Production

Previous experimental and analytical studies conducted to compare the performance of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep with respect to aerodynamic performance and stability to multistage configurations. The experimental investigation compares, on a back-to-back test basis, two builds of an advanced good efficiency, high pressure ratio, two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained an already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two stage fan’s sensitivity with inlet distortion.

Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)

2019 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Compressor Inlet

Abstract The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work. For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted. The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.

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 Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute

2011 ◽  
Author(s):  
Mingyang Yang ◽  
Ricardo Martinez-Botas ◽  
Yangjun Zhang ◽  
Xinqian Zheng ◽  
Takahiro Bamba ◽  
...  
Keyword(s):  
High Pressure ◽  
Numerical Method ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Flow Distortion ◽  
Casing Treatment ◽  
High Pressure Ratio ◽  
The Stability

Large feasible operation range is a challenge for high pressure ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing-Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high pressure ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S pressure ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device.

Numerical Study on the Effect of a Volute on Surge Phenomena in a Centrifugal Compressor

2016 ◽  
Author(s):  
S. H. Jeon ◽  
D. H. Hwang ◽  
J. H. Park ◽  
C. H. Kim ◽  
J. H. Baek ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Stokes Equations ◽  
Flow Instability ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Unstable Flow ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Blade Passing Frequency

Numerical investigation of the effect of the volute on stall flow phenomenon is presented by solving three-dimensional Reynolds-averaged compressible Navier-Stokes equations. Two different configurations of a centrifugal compressor were used to compare their performance: One is an original centrifugal compressor which is composed of impeller, splitter, vaned diffuser and a volute and the other is the one without a volute. Steady calculations were performed to predict aerodynamic performance in terms of the pressure ratio, efficiency and mass flow rate. The results show that the operating range of the compressor with a volute is narrower than that of the compressor without a volute. This can be interpreted that flow instability is strongly influenced by the tongue of a volute which is highly asymmetric. Unsteady calculations were also performed with a time-step size of 38μs corresponding to a pitch angle of 5 degrees at the given rotational speed. The flow characteristics for two configurations are analyzed and compared at various instantaneous times showing unsteady dynamic features. Based on the unsteady flow simulation, fast Fourier transform at several discrete points in semi-vaneless space was performed at peak efficiency and near surge point in order to illustrate the unstable flow physics in both configurations. It is found that the blade passing frequency is dominant, indicating that diffuser passages have a periodicity of 40 degrees due to the rotational blades. Besides blade passing frequency, there were several noticeable frequencies which affect the instability of the whole system. Those frequencies in both configurations are compared and analyzed in various aspects.

A CFD Analysis of the Effects of Two-Phase Flow in a Two-Stage Centrifugal Compressor

2015 ◽  
Author(s):  
Chaitanya V. Halbe ◽  
Walter F. O’Brien ◽  
William T. Cousins ◽  
Vishnu Sishtla
Keyword(s):  
Centrifugal Compressor ◽  
Two Phase Flow ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Power Input ◽  
Phase Flow ◽  
Two Stage ◽  
Two Phase ◽  
Droplet Dynamics ◽  
Compressor Performance

The performance of a compressor is known to be affected by the ingestion of liquid droplets. Heat, mass and momentum transfer as well as the droplet dynamics are some of the important mechanisms that govern the two-phase flow. This paper presents numerical investigations of three-dimensional two-phase flow in a two-stage centrifugal compressor, incorporating the effects of the above mentioned mechanisms. The results of the two-phase flow simulations are compared with the simulation involving only the gaseous phase. The implications for the compressor performance, viz. the pressure ratio, the power input and the efficiency are discussed. The role played by the droplet-wall interactions on the rate of vaporization, and on the compressor performance is also highlighted.

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