The Use of Cascade Technology in Centrifugal Compressor Vaned Diffuser Design

1972 ◽  
Vol 94 (3) ◽  
pp. 187-192 ◽  
Author(s):  
R. C. Pampreen
Keyword(s):  
Centrifugal Compressor ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Circular Arc ◽  
Performance Results

This paper highlights some results from experience with use of cascade technology in the design of diffusers for centrifugal compressors. The designs consisted of conformally transformed tandem blade-rows using 65-Series and double-circular-arc vane sections. Performance results are presented and comparisons to conventional diffuser data are made.

scholarly journals Surge Margin Optimization of Centrifugal Compressors Using a New Objective Function Based on Local Flow Parameters

2019 ◽  
Vol 4 (4) ◽  
pp. 42
Author(s):  
Johannes Ratz ◽  
Sebastian Leichtfuß ◽  
Maximilian Beck ◽  
Heinz-Peter Schiffer ◽  
Friedrich Fröhlig
Keyword(s):  
Objective Function ◽  
Centrifugal Compressor ◽  
Computational Effort ◽  
Angle Distribution ◽  
Centrifugal Compressors ◽  
Local Flow ◽  
Vaned Diffuser ◽  
Flow Parameters ◽  
Surge Margin ◽  
Beta Angle

Currently, 3D-CFD design optimization of centrifugal compressors in terms of the surge margin is one major unresolved issue. On that account, this paper introduces a new kind of objective function. The objective function is based on local flow parameters present at the design point of the centrifugal compressor. A centrifugal compressor with a vaned diffuser is considered to demonstrate the performance of this approach. By means of a variation of the beta angle distribution of the impeller and diffuser blade, 73 design variations are generated, and several local flow parameters are evaluated. Finally, the most promising flow parameter is transferred into an objective function, and an optimization is carried out. It is shown that the new approach delivers similar results as a comparable optimization with a classic objective function using two operating points for surge margin estimation, but with less computational effort since no second operating point near the surge needs to be considered.

Improvement of the Flow Range of Transonic Centrifugal Compressors With a Low-Solidity Cascade Diffuser

2000 ◽  
Author(s):  
Hiroshi Hayami
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Ratio ◽  
Input Power ◽  
Velocity Of Sound ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Transonic Centrifugal Compressor ◽  
Series Of Experiments ◽  
Low Solidity Cascade Diffuser

If the pressure ratio of a typical single-stage centrifugal compressor is larger than four, the velocity relative to the impeller and to the diffuser exceeds the velocity of sound. The flow range of transonic centrifugal compressors with a vaned diffuser is usually very narrow. Low-solidity cascade diffusers with solidity 0.69 have been successfully applied as a part of the diffuser system of a transonic centrifugal compressor. On the basis of this type of diffuser, a series of experiments to broaden the operating range are discussed focusing on the control of the geometry of impeller and/or diffuser; one was to reduce the inducer blade turning upstream of the throat, and the other was to reduce the inlet passage width of diffuser. The milder inducer blade camber realized the improvement in flow range by 1.5 times to the original one. Regarding the diffuser inlet passage width contraction, the flow range was not broadened so much owing to the change in impeller characteristics, but the input power was reduced and then the high speed efficiency was much improved.

Numerical investigation of the diffuser throat length effect on a transonic centrifugal compressor

2021 ◽  
pp. 095440622110401
Author(s):  
Qingkuo Li ◽  
Yingjie Zhang ◽  
Yi Wang ◽  
Ge Han ◽  
Yanfeng Zhang ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
Flow Direction ◽  
Divergence Angle ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Stall Margin ◽  
Transonic Centrifugal Compressor ◽  
Fluid Pressurization ◽  
Large Flow

Vaned diffuser inlet flow uniform is challenging when the impeller is throttled to stall. In this study, we extend the stable operating range of the compressor by improving the uniform flow of the diffuser inlet. First, a numerical investigation of a transonic centrifugal compressor with a vaned diffuser is presented and compared against test data. Then, a new diffuser parameterization method is pro- posed, and the throat feature of a pipe diffuser is successfully applied to parameterized vane diffusers. The influence of the throat length and divergence angle of the diffuser on the performance of the centrifugal compressor is studied via steady and non-linear harmonic simulations. Throat length delays the time of fluid pressurization and accommodates large flow instabilities from upstream—this widens the stall margin but increases mixing loss. Divergence angle affects compressor performance. Stage peak efficiency increases by about 0.58% as the divergence angle increases from 3.79° to 5.79° but drops to about 2.46% as the divergence angle further increases from 5.79° to 11.79°. This is because the boundary layers in the diffuser channel thicken with increasing divergence angle; additionally, the fluid near the hub-pressure side first becomes unstable, then flow separation occurs along the flow direction, which results in a large flow loss. Detailed performance maps of centrifugal compressors with different throat lengths and divergence angles are given to provide a reference for designing transonic centrifugal compressors.

A Discussion of the Factors Affecting Surge in Centrifugal Compressors

1985 ◽  
Vol 107 (2) ◽  
pp. 499-506 ◽  
Author(s):  
R. L. Elder ◽  
M. E. Gill
Keyword(s):  
Mathematical Model ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Factors Affecting ◽  
Pressure Losses ◽  
Complex Mathematical Model ◽  
Good Agreement

The process of surge in a centrifugal compressor has been studied and found to be dependent on a number of complex and often interrelated factors. A major factor defining surge in high-speed, vaned diffuser designs appears to be the flow in the semivaneless space. By developing work initiated by others it has been possible to propose some explanation of previously presented apparently conflicting data. In addition, a more complex mathematical model capable of assessing additional factors is proposed. Using this model good agreement with experimental surge has been obtained. This model takes into consideration pressure losses in the impeller, diffuser, and collector, and by using this model it was possible to identify the stalling elements that are responsible for overall compressor instability.

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.

Backward Traveling Rotating Stall Waves in Centrifugal Compressors

2002 ◽  
Author(s):  
Z. S. Spakovsky
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
First Principles ◽  
Rotating Stall ◽  
Air Injection ◽  
System Stability ◽  
Centrifugal Compressors ◽  
Injection Scheme ◽  
Surge Margin ◽  
Low Order

Rotating stall waves that travel against the direction of rotor rotation are reported for the first time and a new, low-order analytical approach to model centrifugal compressor stability is introduced. The model is capable of dealing with unsteady radially swirling flows and the dynamic effects of impeller-diffuser component interaction as it occurs in centrifugal compression systems. A simple coupling criterion is developed from first principles to explain the interaction mechanism important for system stability. The model findings together with experimental data explain the mechanism for first-ever observed backward traveling rotating stall in centrifugal compressors with vaned diffusers. Based on the low-order model predictions, an air injection scheme between the impeller and the vaned diffuser is designed for the NASA Glenn CC3 high-speed centrifugal compressor. The steady air injection experiments show an increase of 25% in surge-margin with an injection mass flow of 0.5% of the compressor mass flow. In addition, it is experimentally demonstrated that this injection scheme is robust to impeller tip-clearance effects and that a reduced number of injectors can be applied for similar gains in surge-margin. The results presented in this paper firmly establish the connection between the experimentally observed dynamic phenomena in the NASA CC3 centrifugal compressor and a first principles based coupling criterion. In addition, guidelines are given for the design of centrifugal compressors with enhanced stability.

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.

Effects of Diffuser Vane Geometries on Compressor Performance and Noise Characteristics in a Centrifugal Compressor

2013 ◽  
Author(s):  
Yohei Morita ◽  
Nobumichi Fujisawa ◽  
Takashi Goto ◽  
Yutaka Ohta
Keyword(s):  
Centrifugal Compressor ◽  
Noise Level ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Numerical Techniques ◽  
Vaned Diffuser ◽  
Noise Characteristics ◽  
Edge Vortex ◽  
Compressor Performance

The effects of the diffuser vane geometries on the compressor performance and noise characteristics of a centrifugal compressor equipped with vaned diffusers were investigated by experiments and numerical techniques. Because we were focusing attention on the geometries of the diffuser vane’s leading edge, diffuser vanes with various leading edge geometries were installed in a vaned diffuser. A tapered diffuser vane with the tapered portion near the leading edge of the diffuser’s hub-side could remarkably reduce both the discrete frequency noise level and broadband noise level. In particular, a hub-side tapered diffuser vane with a taper on only the hub-side could suppress the development of the leading edge vortex (LEV) near the shroud side of the diffuser vane and effectively enhanced the compressor performance.

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.

The influence of the trailing edge angle of the micro centrifugal impeller on the performance of the centrifugal compressor

2021 ◽  
pp. 1-15
Author(s):  
Xu Yu-dong ◽  
Li Cong ◽  
Lv Qiong-ying ◽  
Zhang Xin-ming ◽  
Mu Guo-zhen
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Centrifugal Impeller ◽  
Centrifugal Compressors ◽  
Trailing Edge ◽  
Sweep Angle ◽  
Impeller Blade ◽  
Bending Angle ◽  
Edge Angle ◽  
Isentropic Efficiency

In order to study the effect of the trailing edge sweep angle of the centrifugal impeller on the aerodynamic performance of the centrifugal compressor, 6 groups of centrifugal impellers with different bending angles and 5 groups of different inclination angles were designed to achieve different impeller blade trailing edge angle. The computational fluid dynamics (CFD) method was used to simulate and analyze the flow field of centrifugal compressors with different blade shapes under design conditions. The research results show that for transonic micro centrifugal compressors, changing the blade trailing edge sweep angle can improve the compressor’s isentropic efficiency and pressure ratio. The pressure ratio of the compressor shows a trend of increasing first and then decreasing with the increase of the blade bending angle. When the blade bending angle is 45°, the pressure ratio of the centrifugal compressor reaches a maximum of 1.69, and the isentropic efficiency is 67.3%. But changing the inclination angle of the blade trailing edge has little effect on the isentropic efficiency and pressure ratio. The sweep angle of blade trailing edge is an effective method to improve its isentropic efficiency and pressure ratio. This analysis method provides a reference for the rational selection of the blade trailing edge angle, and provides a reference for the design of micro centrifugal compressors under high Reynolds numbers.

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