Primary Design of Vaneless Diffusers of Centrifugal Compressor Stages by the Universal Modeling Method

2021 ◽  
pp. 39-52
Author(s):  
O.A. Solovyeva ◽  
K.V. Soldatova ◽  
Y.B. Galerkin ◽  
A.F. Rekstin
Keyword(s):  
Continuous Flow ◽  
Design Method ◽  
Modeling Method ◽  
Inlet Section ◽  
Relative Width ◽  
Design Practice ◽  
Main Section ◽  
Flow Angle ◽  
Gas Dynamic ◽  
Vaneless Diffusers

Vaneless diffusers of industrial centrifugal compressors most often consist of a tapered inlet section and a parallel-walled main section. The study proposes to choose such a width of the main section, at which the flow in the diffuser remains unseparated at the surge limit. To implement the primary design method, an empirical formula was obtained to determine the minimum continuous flow angle depending on the relative width of the diffuser. The primary design of eighteen stages was completed, covering a practically important range of parameters. The corresponding gas-dynamic characteristics were calculated by the universal modeling method, the dimensions and angles of the flow were analyzed. The proposed primary design method is integrated into the universal modeling method and is used in design practice.

CFD-model of Vaneless Diffuser of Centrifugal Compressor

2021 ◽  
pp. 109-130
Author(s):  
О.А. Solovyeva ◽  
А.А. Drozdov ◽  
E.Yu. Popova ◽  
K.V. Soldatova
Keyword(s):  
Mathematical Model ◽  
Centrifugal Compressor ◽  
Dynamic Characteristics ◽  
Modeling Method ◽  
Relative Width ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Flow Parameters ◽  
Gas Dynamic ◽  
Vaneless Diffusers

The centrifugal compressor design involves the use of approximate engineering techniques based on mathematical modeling. One of such techniques is the universal modeling method, which proves to be practically applicable. Having generalized a series of CFD calculations, we used a mathematical model in the latest version of the compressor model to calculate flow parameters in vaneless diffusers. The diffuser model was identified based on the results of experimental studies of average-flow model stages carried out at SPbPU. The model is also used to calculate Clark low-flow centrifugal compressor stages with narrow diffusers with a relative width in the range of 0.5--2.0 %. For these stages, the developed mathematical model showed insufficient efficiency, since the dimensions of the diffusers go beyond the limits of its applicability. To solve this problem, we calculated a series of vaneless diffusers with a relative width in the range of 0.6--1.2 % in the ANSYS CFX software package. Relying on the results of CFD calculations, we plotted the gas dynamic characteristics of the loss coefficients and changes in the flow angle depending on the flow angle at the inlet to the vaneless diffuser. To process the calculated data, the method of regression analysis was applied, with the help of which a system of algebraic equations was developed that connects geometric, gas-dynamic parameters and similarity criteria. The obtained equations are included in a new mathematical model of the universal modeling method for calculating the flow parameters of vaneless diffusers. Comparison of the calculated gas-dynamic characteristics according to the new model with experimental data showed the average error of modeling the calculated (maximum) efficiency equal to 1.08 %

Simulating Characteristics of Vaneless Diffusers Using Neural Networks

2020 ◽  
pp. 29-42
Author(s):  
Y.B. Galerkin ◽  
A.G. Nikiforov ◽  
O.A. Solovyeva ◽  
E.Y. Popova
Keyword(s):  
Neural Networks ◽  
Mathematical Models ◽  
Dynamic Characteristics ◽  
Flow Direction ◽  
Similarity Criteria ◽  
Relative Width ◽  
Flow Angle ◽  
Gas Dynamic ◽  
Vaneless Diffusers ◽  
Two Parameters

To calculate flow parameters of a vaneless diffuser of the centrifugal compressor stage, it is sufficient to determine the loss coefficient and the flow direction at the outlet. The paper presents the results of modeling the characteristics of these two parameters using neural networks and CFD methods. To obtain mathematical models, ANSYS calculation data was used for vaneless diffusers with a relative width of 0.014–0.1, relative outlet diameter of 1.4–2.0, inlet flow angle of 10–90° and velocity coefficient of 0.39–0.82, with the Reynolds number being in the range of 87 500–1 030 000. A comparison with the theory showed the regularity of gas-dynamic characteristics, and comparison with well-known experiments showed the correspondence of the flow structure. In order to improve the accuracy of simulation using neural networks, various recommendations on the preparation and processing of the initial data were collected and tested: identification of conflict examples and outliers, data normalization, improving the quality of the neural network training under the insufficient amount of sampling, etc. The application of the aforementioned recommendations significantly improved the accuracy of simulation. A simulation experiment based on neural models for studying the influence of dimensions, diffuser shape and similarity criteria on the diffuser gas dynamic characteristics made it possible to verify physical adequacy of the mathematical models, obtain new data on energy conversion processes and produce a set of recommendations on the optimal design of vaneless diffusers.

scholarly journals Mathematical model of centrifugal compressor vaneless diffuser based on CFD calculations

2020 ◽  
Vol 178 ◽  
pp. 01014
Author(s):  
Olga Solovyeva ◽  
Aleksandr Drozdov
Keyword(s):  
Mathematical Model ◽  
Centrifugal Compressor ◽  
Similarity Criteria ◽  
Relative Width ◽  
Inlet Flow ◽  
Flow Angle ◽  
Gas Dynamic ◽  
Modelling Method ◽  
Vaneless Diffusers ◽  
The Mathematical Model

The approximate engineering techniques based on mathematical modelling are used in centrifugal compressor design. One of such methods is the well-proven Universal Modelling Method, developed in the scientific and research laboratory “Gas dynamics of turbo machines”, SPbPU. In the modern version of the compressor model, vaneless diffusers mathematical model was applied based on a generalization of the CFD calculations. The mathematical model can be used for vaneless diffusers with a relative width in the range of 1.4 – 10.0%, with a radial length up to 2.0, in the range of inlet flow angles 10 to 90 degrees, the inlet velocity coefficient in the range of 0.39 – 0.82, Reynolds number varying from 87 500 to 1 030 000. The model was also used for calculating low-flow-rate model stages with narrow diffusers with diffusers’ relative width in the range of 0.5 – 2.0%. The mathematical model showed lesser accuracy. To widen the model applicability, new series of CFD-calculations were executed. A series of vaneless diffusers was designed with relative width in the range of 0.6 – 1.2%, The gas-dynamic characteristics of loss coefficients and outlet flow angle versus inlet flow angle of diffuser were calculated. Regression analysis was used to process the calculated data. System of algebraic equations linking geometric, gas-dynamic parameters and similarity criteria was developed. The obtained equations are included in a new mathematical model of the Universal Modelling Method.

Selecting the Dimensions of the Vaneless Diffuser of a Centrifugal Compressor Stage at the Primary Design Phase

2019 ◽  
pp. 43-57
Author(s):  
Y.B. Galerkin ◽  
A.F. Rekstin ◽  
O.A. Solovyeva
Keyword(s):  
Centrifugal Compressor ◽  
Design Method ◽  
Modeling Method ◽  
Design Flow ◽  
Optimal Size ◽  
Outer Diameter ◽  
Relative Width ◽  
Vaneless Diffuser ◽  
Radial Length ◽  
Vaneless Diffusers

The advances in the primary design method of centrifugal compressors of the Universal Modeling Method have led to the need to analyze and revise the recommendations for the optimal size and configuration selection of vaneless diffusers of centrifugal compressor stages. The results of CFD calculations of a family of vaneless diffusers with different relative width, radial length, velocity coefficients and flow angles at the inlet are used to develop new recommendations. The choice of the optimal width of the vaneless diffuser is based on ensuring a non-separable flow in it at the boundary of the surge. The optimal value of the relative radial length of the diffuser is in the range of 1.65–2.0. Considering the above, a formula for selecting the vaneless diffuser outer diameter is proposed depending on the design flow rate coefficient. The developed primary design method of vaneless diffusers is included in the software programs of the Universal Modeling Method and is used in design and research practice.

Factored axial compressive resistance of schifflerized angles

1991 ◽  
Vol 18 (6) ◽  
pp. 926-932 ◽  
Author(s):  
Seshu Madhava Rao Adluri ◽  
Murty K. S. Madugula
Keyword(s):  
Key Words ◽  
Design Method ◽  
Design Criteria ◽  
Design Practice ◽  
Buckling Mode ◽  
Flexural Buckling ◽  
Mode Of Failure ◽  
Current Design ◽  
Similarities And Differences ◽  
Compressive Resistance

The concept of schifflerization of 90° equal-leg angle is presented and its application in triangular-base latticed steel towers is explained. The similarities and differences between schifflerized angles and regular 90° angles are discussed. The current design practice for schifflerized angles is reviewed and its limitation is highlighted. A design method which includes the effect of the torsional-flexural buckling mode of failure is proposed. For ready use of designers, the factored axial compressive resistances of schifflerized angles are tabulated for both the present and proposed design methods. Key words: buckling, compressive resistance, design criteria, schifflerized angles, stability, standards, steel, struts, towers, guyed towers.

Inverse Design of 3D Multi-Stage Transonic Fans at Dual Operating Points

2013 ◽  
Author(s):  
James H. Page ◽  
Paul Hield ◽  
Paul G. Tucker
Keyword(s):  
Design Method ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Inverse Design ◽  
Flow Angle ◽  
Trade Offs ◽  
Multi Stage ◽  
Full Speed ◽  
Computational Fluid Dynamics Cfd ◽  
Operating Points

Semi-inverse design is the automatic re-cambering of an aerofoil, during a computational fluid dynamics (CFD) calculation, in order to achieve a target lift distribution while maintaining thickness, hence “semi-inverse”. In this design method, the streamwise distribution of curvature is replaced by a stream-wise distribution of lift. The authors have developed an inverse design code based on the method of Hield (2008) which can rapidly design three-dimensional fan blades in a multi-stage environment. The algorithm uses an inner loop to design to radially varying target lift distributions, an outer loop to achieve radial distributions of stage pressure ratio and exit flow angle, and a choked nozzle to set design mass flow. The code is easily wrapped around any CFD solver. In this paper, we describe a novel algorithm for designing simultaneously for specified performance at full speed and peak efficiency at part speed, without trade-offs between the targets at each of the two operating points. We also introduce a novel adaptive target lift distribution which automatically develops discontinuous changes of calculated magnitude, based on the passage shock, eliminating erroneous lift demands in the shock vicinity and maintaining a smooth aerofoil.

scholarly journals A New Method for Impeller Inlet Design of Supercritical CO2 Centrifugal Compressors in Brayton Cycles

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5049
Author(s):  
Xiaojian Li ◽  
Yijia Zhao ◽  
Huadong Yao ◽  
Ming Zhao ◽  
Zhengxian Liu
Keyword(s):  
Design Method ◽  
Operating Conditions ◽  
Low Flow ◽  
Working Fluid ◽  
Centrifugal Compressors ◽  
Flow Angle ◽  
Real Gas ◽  
Total Condition ◽  
Swallowing Capacity ◽  
Cycle Efficiency

Supercritical Carbon Dioxide (SCO2) is considered as a potential working fluid in next generation power and energy systems. The SCO2 Brayton cycle is advantaged with higher cycle efficiency, smaller compression work, and more compact layout, as compared with traditional cycles. When the inlet total condition of the compressor approaches the critical point of the working fluid, the cycle efficiency is further enhanced. However, the flow acceleration near the impeller inducer causes the fluid to enter two-phase region, which may lead to additional aerodynamic losses and flow instability. In this study, a new impeller inlet design method is proposed to achieve a better balance among the cycle efficiency, compressor compactness, and inducer condensation. This approach couples a concept of the maximum swallowing capacity of real gas and a new principle for condensation design. Firstly, the mass flow function of real gas centrifugal compressors is analytically expressed by non-dimensional parameters. An optimal inlet flow angle is derived to achieve the maximum swallowing capacity under a certain inlet relative Mach number, which leads to the minimum energy loss and a more compact geometry for the compressor. Secondly, a new condensation design principle is developed by proposing a novel concept of the two-zone inlet total condition for SCO2 compressors. In this new principle, the acceptable acceleration margin (AAM) is derived as a criterion to limit the impeller inlet condensation. The present inlet design method is validated in the design and simulation of a low-flow-coefficient compressor stage based on the real gas model. The mechanisms of flow accelerations in the impeller inducer, which form low-pressure regions and further produce condensation, are analyzed and clarified under different operating conditions. It is found that the proposed method is efficient to limit the condensation in the impeller inducer, keep the compactness of the compressor, and maintain a high cycle efficiency.

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