Reynolds Number and Roughness Effects on Turbocompressor Performance: Numerical Calculations and Measurement Data Evaluation

2020 ◽  
Author(s):  
Fabian Dietmann ◽  
Michael Casey ◽  
Damian M. Vogt
Keyword(s):  
Reynolds Number ◽  
Measurement Data ◽  
Theoretical Models ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Roughness Effects ◽  
Flow Channels ◽  
Compressor Performance ◽  
Low Flow Coefficient

Abstract Further validation of an analytic method to calculate the influence of changes in Reynolds number, machine size and roughness on the performance of axial and radial turbocompressors is presented. The correlation uses a dissipation coefficient as a basis for scaling the losses with changes in relative roughness and Reynolds number. The original correlation from Dietmann and Casey [6] is based on experimental data and theoretical models. Evaluations of five numerically calculated compressor stages at different flow coefficients are presented to support the trends of the correlation. It is shown that the sensitivity of the compressor performance to Reynolds and roughness effects is highest for low flow coefficient radial stages and steadily decreases as the design flow coefficient of the stage and the hydraulic diameter of the flow channels increases.

On the Evaluation of Reynolds Number and Relative Surface Roughness Effects on Centrifugal Compressor Performance Based on Systematic Experimental Investigations

1984 ◽  
Vol 106 (2) ◽  
pp. 489-498 ◽  
Author(s):  
H. Simon ◽  
A. Bu¨lska¨mper
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Centrifugal Compressor ◽  
Performance Test ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Design Calculation ◽  
Roughness Effects ◽  
Number Range ◽  
Compressor Performance

This paper summarizes the results of systematic investigations into the Reynolds number effects. It is based on performance map measurements carried out on a compressor test rig which was constructed primarily for this purpose. The measurements were performed for stages with different flow coefficients (0.004 ≦ φ1 ≦ 0.05), with different gases (air, nitrogen, helium, freon) and in the inlet pressure range 0.2 bar ≦ p1 ≦ 40 bar. By analogy with the turbulent flow in technically rough pipes, semi-empirical correlations are derived concerning the effects of the Reynolds number and the relative surface roughness on the characteristic performance parameters (efficiency, flow coefficient, head coefficient, work coefficient). For the detailed design calculation of individual stages, provision is made for the different effects on the hydraulic flow losses and the disk friction losses. Simplified correlations are given for the conversion of characteristics measured during thermodynamic performance tests. The correlations are applied to various single and multistage compressors, and the results compared with measured performance characteristics in the Reynolds number range 6 × 103 ≦ Ret ≦ 1.1 × 107. The good correspondence obtained forms the basis for recommending the application of these simplified relationships for the improvement of centrifugal compressor performance test codes (e.g. ASME PTC-10 and ISO TC 118).

Analysis and Redesign of the Stationary Components for a Low Flow Coefficient Centrifugal Compressor Stage

2009 ◽  
Author(s):  
Zhiheng Wang ◽  
Guang Xi
Keyword(s):  
Centrifugal Compressor ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Meridional Plane ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Lower Stage ◽  
Wide Range ◽  
Low Flow Coefficient

A low flow coefficient centrifugal compressor stage is characterized by the small relative outlet width, and is often one of the latter stages in the multistage compressor. The low flow coefficient stage is known to give lower stage efficiency in comparison with the conventional stage, which still leaves much more space to be improved with modern tools such as CFD techniques. In the paper the flow in a CO2 centrifugal compressor stage with a low design flow coefficient of 0.008 is simulated based on the 3D viscous CFD codes. The analysis shows the impeller gives a favorable performance over a wide range of low flow coefficient, but the high losses exist in the stationary components and this incurs the poor performance of the whole stage. In this case, the diffuser, the return channel and the meridional plane are redesigned. The redesigned stage has distinct improvements on the performance and the flow structure.

scholarly journals РЕЗУЛЬТАТЫ УСОВЕРШЕНСТВОВАНИЯ СТУПЕНИ ВЫСОКОНАГРУЖЕННОЙ ТУРБИНЫ НИЗКОГО ДАВЛЕНИЯ

2019 ◽  
pp. 30-37
Author(s):  
Игорь Федорович Кравченко ◽  
Сергей Александрович Хомылев
Keyword(s):  
Flow Separation ◽  
Wedge Angle ◽  
Operating Conditions ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Energy Losses ◽  
Suction Surface ◽  
Experimental Development ◽  
Leading Edges

One of the characteristic features of high loaded low-pressure turbine (LPT) with a low flow coefficient is the high-level flow deflection in the blade rows, which have sufficiently thin and strongly curved cross-section profiles. Such profiles are very sensitive to off-design flow angles, especially to positive incidence. Therefore, the effectiveness of a high loaded LPT strongly depends on the working conditions. At the same time, for various reasons, in the process of research tests or operating the engine, the operating conditions may differ greatly from the design ones. Therefore, the creation of a robust LPT design is an actual task. The article considers the computational approbation of the method of increasing the resistance to large off-design angles of attack of vane and blade rows of the intermediate stage of a high loaded LPT of an experimental engine by changing the shape of the leading edges. The turbine was previously tested as part of a full-scale engine, where it was determined that the operating conditions of the LPT and its efficiency are significantly different from the calculated ones. Numerical (CFD) analysis of the flow showed that one of the reasons for the low efficiency is the large angles of attack on the vane and blade rows of the second stage, which lead to the flow separation and an increase of the energy losses coefficients at final. The modernization of the profiles was carried out by reducing the radius and a local increase of the leading edges wedge angle without changing the basic profiles. According to the calculation results, it was allowed to significantly improve the stream. The intensity of the flow deceleration behind the shock wave at the point of transition from the circumference of the edge to the suction surface was reduced, this made it possible to eliminate or reduce the intensity of the flow separation in the vane row and significantly reduce the energy losses coefficient. A more favorable flow was also achieved in the blade row, where a slight decrease in the losses coefficient was also obtained. As a result, the efficiency of the stage and the whole LPT was increased at the off-design operating conditions. This approach can be recommended both to increase the efficiency of the turbine at the experimental development, and when designing new turbines to increase their robustness.

scholarly journals Numerical characteristics of a centrifugal compressor with a low flow coefficient

2019 ◽  
Vol 140 ◽  
pp. 06010 ◽  
Author(s):  
Aleksey Yablokov ◽  
Ivan Yanin ◽  
Nikolay Sadovskyi ◽  
Yuri Kozhukhov ◽  
Minh Hai Nguyen
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Flow Coefficient ◽  
Ultrahigh Pressure ◽  
Low Flow ◽  
Classical Type ◽  
Numerical Characteristic ◽  
Wall Cell ◽  
Low Flow Coefficient ◽  
Near Wall

The study presents the simulation results of the viscid gas flow in low flow coefficient centrifugal compressor stages. The problem is solved in a stationary formulation using the Ansys CFX software package. The numerical simulation is carried out on three ultrahigh-pressure model stages; two stages have blades of the classical type impeller and one stage is of the bodily type. The value of the conditional flow coefficient is 0.0063 to 0.015. As part of the study, block-structured design meshes are used for all gas channel elements, with their total number being equaled as 13–15 million. During the calculations a numerical characteristic was validated with the results of tests carried out at the Department of Compressor, Vacuum and Refrigeration Engineering of Peter the Great St. Petersburg Polytechnic University. With an increase of inlet pressure as a result of a numerical study, it was found that for a given mathematical model the disk friction and leakage coefficient (1 + βfr + βlk) is overestimated. The analysis of flow in labyrinth seals has shown an increase of total temperature near the discs by 30–50 °С, nevertheless this fact did not influence gas parameters in the behind-the-rotor section. The calculation data obtained with finer design mesh (the first near-wall cell was 0.001 mm) is identical to those obtained with the first near-wall cell 0.01 mm mesh.

A New Appraisal of Reynolds Number Effects on Centrifugal Compressor Performance

1979 ◽  
Vol 101 (3) ◽  
pp. 384-392 ◽  
Author(s):  
F. J. Wiesner
Keyword(s):  
Reynolds Number ◽  
Centrifugal Compressor ◽  
Performance Test ◽  
Flow Coefficient ◽  
Performance Parameters ◽  
Empirical Methods ◽  
Reynolds Number Effects ◽  
Significant Performance ◽  
Compressor Performance ◽  
Overall Performance

This paper summarizes the results of an investigation into the effects of Reynolds number on the performance of centrifugal compressor stages, using a computer program for the detailed prediction of component and overall performance characteristics. This investigation included wide variation of stage geometries, speeds, and fluid conditions, resulting in diffuser inlet absolute Reynolds number variations over the range from 5 × 102 to 5 × 108. The computer results indicate that variations in Reynolds number and in relative roughness will produce variations in all significant performance parameters: the flow coefficient, the work coefficient, and the efficiency. Correlations of these results with various sources of test data on single and multistage centrifugal compressors produce very satisfactory comparisons. As a result of this study, improved empirical methods are recommended for making practical adjustments of compressor performance with variation in Reynolds number. These recommendations should be taken into account in the modernization of all centrifugal compressor performance test codes such as those formulated by ASME and ISO.

Numerical Investigation on the Labyrinth Seal Design for a Low Flow Coefficient Centrifugal Compressor

2010 ◽  
Author(s):  
Zhiheng Wang ◽  
Liqun Xu ◽  
Guang Xi
Keyword(s):  
Centrifugal Compressor ◽  
Labyrinth Seal ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Centrifugal Impeller ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Isentropic Efficiency ◽  
Low Flow Coefficient

The leakage flow across the shroud of a centrifugal compressor impeller has an important effect on the compressor’s performance, in particular, in the low flow coefficient compressor. This paper presents the three-dimensional CFD simulations and the Radial Basis Function (RBF) model to investigate the aerodynamic performance of the labyrinth seal as well as the low flow coefficient centrifugal impeller. The CFD simulations are performed on the computational domain consisting of the labyrinth seal and the impeller. The relationship between the leakage loss coefficient and the isentropic efficiency is indicated. With the application of the RBF model, the global sensitivity analysis to the seal geometric design parameters is carried out, and the geometry of the labyrinth seal is optimized. The leakage of the optimized labyrinth seal is reduced remarkably and the impeller’s isentropic efficiency improved by 2% in a wide operating range.

Effect of a Recirculation Device on the Performance of Transonic Mixed Flow Compressors

2014 ◽  
Author(s):  
Ryusuke Numakura ◽  
Hideaki Tamaki ◽  
Hamid Hazby ◽  
Michael Casey
Keyword(s):  
Measurement Data ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Suction Surface ◽  
Mixed Flow ◽  
Recirculation Flow ◽  
Stable Operating ◽  
Compressor Performance ◽  
The Stability ◽  
Stability Enhancement

Two transonic mixed flow compressors with an extremely high flow coefficient of ϕ = 0.25 and pressure ratios of 2.5 and 2.65 have been designed and tested. CFD simulations indicated that both impellers operate with a suction surface relative Mach number of above 1.5 at their design conditions. Both compressors achieved a narrow stable operating range when tested without recirculation devices. The effects of two different recirculation devices on the compressor performance maps were investigated both experimentally and numerically. The first type is a widely used recirculation device which consists of an upstream slot, bleed slot and an annular cavity which connects both slots. The other has vanes installed in the cavity which were designed to provide a recirculation flow with negative swirl at the impeller inlet. Measurement data demonstrated the effect of the recirculation devices on increasing the range of these two transonic mixed flow compressors and showed the superiority of the recirculation device with vanes. The effects of the recirculation devices on the impeller flow field at near surge conditions are studied using steady state 3D CFD calculations. Both measurements and simulations showed that the stability enhancement is partly caused by a steeper pressure rise characteristic.

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