Design Procedure of Centrifugal Compressors
Nazih Bayomi2014
Sign up for access to the world's latest research
checkGet notified about relevant papers
checkSave papers to use in your research
checkJoin the discussion with peers
checkTrack your impact
Abstract
his paper investigates the development of a preliminary design method for centrifugal compressors. The design process starts with the aerodynamic analysis of the preliminary design and its reliance on empirical rules limiting the main design parameters. The procedure is applied to compressors for pressure ratios of 1.5, 3 and 5 as an example for developing an initial non-dimensional skeleton design. The skeleton diagrams are presented for different exit blade angles ranging from 0° to-60°. The design procedure was carried out for three cases: without prewhirl and with high positive prewhirl of 15° and 30°. Design considerations of mechanical stress for the impeller and minimum inlet relative Mach number are taken into consideration. Diffusion factor limitations have also been considered. Selected design parameters according to economical considerations have been presented for each pressure ratio.
Key takeaways
- A simple method for designing the blade geometry of a centrifugal compressor impeller was presented by Wang et al.
- The third term includes the ratio of the flow velocity in the radial direction, C r2 and the impeller speed, U 2 , known as the flow coefficient j and the exit blade angle β ∞2 .
- Application of the continuity condition at impeller inlet leads to the non-dimensional mass flowrate at impeller inlet (see Whitfield and Baines [24]), as
- Relations between the non-dimensional impeller speed, M u2 , and inlet relative Mach number, M 1rel , for different blade angles and different radius ratios r 1s /r 2 ranging from 0.4 to 0.9 are computed using equation 11for the different pressure ratios.
- At a pressure ratio of 3, a backsweep angle of 40° with a prewhirl of 30° is recommended for impeller design for the non-dimensional mass flowrate, θ of up to 0.1.
Related papers
DESIGN AND NUMERICAL ANALYSIS OF A CENTRIFUGAL COMPRESSOR.
2020
Centrifugal compressors are used widely in various range of aero-engine applications both small and medium-sized. And its performance affects the working state of the engine. So in this thesis I am going to briefly explain how the performance affects the working state using three different solutions. The first is the normal numerical solution using compal, in this solution, working conditions were added to get performance curves which I will discuss later in this thesis. The second solution is the blade to blade solution and the third solution is the computational fluid dynamics (CFD) solution. Computational Fluid Dynamics is usually used in centrifugal compressor design. Computational fluid dynamics provides extensive optimization chances for the compressor design instead of designing the centrifugal compressor. The design process is still an important part of the compressor developments. The wide range of design subjects represents a very not so easy design world for centrifugal compressor designers. So, a few basic information for centrifugal design is still quite important. The impeller is the most useful part of the centrifugal stage. Designing a very efficiency centrifugal impeller with a wide operation range can ensure overall design success. With these three solution how briefly explain how they affect the working state of the centrifugal compressor. Keywords: Centrifugal compressor; Mass flow; Pressure ratio; CFD; Overall performance. Blade to Blade; Compal solution.
A Review on Centrifugal Compressor Design Methods
The use of turbochargers has increased in response to strengthened automotive exhaust emission and fuel consumption regulations for global environmental protection. Most centrifugal compressors are required to operate over a broad range of flow rates and to provide a high pressure ratio with high efficiency. The internal flow of a centrifugal compressor is very problematic with 3-dimensional and unsteady flow phenomena, and the analysis of flow phenomena and expansion of the operational range are difficult problems. Review is done for gathering the efficient method for designing and analyzing the centrifugal compressor. In order to meet these demands the application of variable geometry techniques is often considered and applied.
Some Aerodynamic Considerations in the Design of Centrifugal Compressor Impellers
Abstract: A simple one dimensional approach to determine the size of the centrifugal impeller for maximum through flow has been indicated. This design procedure does not mean that the centrifugal impeller could be finally decided on the results obtained from this article. It must be borne in mind that this only deals with some aspects of the design and in itself is not a complete one by which the impeller could have its final shape and size. The major idea of introducing this paper is to highlight the importance of some of the parameters that go towards influencing the design of the centrifugal impeller.
Simulation-based Design Optimization of Centrifugal Compressor, Using Computational Fluid Dynamics Methods
Academia Letters, 2021
It has always been important to study the development and improvement of turbomachines' design, owing to their numerous uses and high energy consumption. Accordingly, optimizing turbomachine performance is crucial for sustainable development. The design of impellers significantly affects the performance of centrifugal compressors .
Aerodynamic and geometric optimization for the design of centrifugal compressors
International Journal of Heat and Fluid Flow, 1985
Maximizing efficiency is the main goal in centrifugal compressor design. Thus a computer code has been developed to optimize geometric and fluid dynamic variables with respect to several design constraints. Computations are performed with an adiabatic one-dimensional approach using state-of-the-art loss and slip correlations. The optimization takes into account mechanical stress limits. Results with different loss and slip correlations are compared with the available experimental data. Changes in optimum efficiency and specific speed due to variations of mass flow rate and pressure ratio are also presented and discussed together with the trends of the optimum geometric features.
Optimization of a Centrifugal Compressor Using the Design of Experiment Technique
Applied Sciences, 2019
Centrifugal compressor performance is affected by many parameters, optimization of which can lead to superior designs. Recognizing the most important parameters affecting performance helps to reduce the optimization process cost. Of the compressor components, the impeller plays the most important role in compressor performance, hence the design parameters affecting this component were considered. A turbocharger centrifugal compressor with vaneless diffuser was studied and the parameters investigated included meridional geometry, rotor blade angle distribution and start location of the main blades and splitters. The diffuser shape was captured as part of the meridional geometry. Applying a novel approach to the problem, full factorial analysis was used to investigate the most effective parameters. The Response Surface Method was then implemented to construct the surrogate models and to recognize the best points over a design space created as based on the Box-Behnken methodology. The ...
AERODYNAMIC AND THERMAL DESIGN OF CENTRIFUGAL COMPRESSOR FOR SMALL SCALE IN NON-DIMEMSIONAL FORM
In the present study, a 3D numerical simulation of a non-dimensional design of impeller, diffuser and volute design of centrifugal compressor in dimensional form is carried out by using the commercial code of ANSYS R15.0. The fully 3D, Compressible and Steady flow analysis of the fluid (air) flow were solved in CFX solver. A SST k-v turbulent model was used for a simulation of the on-design performance of the single speed centrifugal compressor. By using this specific design results show that De-Haller number, non-dimensional mass flow rate, non-dimensional ratio of axial length to exit diameter, divergence angle of Diffuser, area ratio from diffuser outlet to volute outlet obtained in order to 0.7, 0.092, 0.33, 7.29 and 0.65 respectively. Also, found that All Mach number are below 1 so there are no shock formations. The mass flow rate is less than chocking mass flow rate at the throat of impeller and diffuser so there is no choking of flow In order to verify the present numerical simulations, the model results were validated with the analytical method gives the good agreement but not exactly due to design losses were neglected.
Effect of impeller geometry on performance characteristics of centrifugal compressor
2019
Centrifugal Compressors play an essential role in oil, gas and petrochemical industries. Their extensive usage is due to their smooth operation and high reliability compared to other other compressor types. One of the main characteristics of these turbomachines is their performance curve, which is an important criterion for selecting the appropriate compressor for a desired working condition. In the presented article, the effect of impeller’s geometry on performance curve and other compressors characteristics is numerically investigated. The 3D CFD code is used to achieve the performance curves that are dedicated to each geometrical configuration. The results indicate that some of the selected geometrical parameters have a significant effect on performance curve margins. Increasing the shroud angle moves the surge point to the higher flow coefficients, while the pressure ratio remains constant and increasing the blade’s trailing edge angle, leads to increase in pressure ratio.
NUMERICAL SOLUTIONS FOR PERFORMANCE PREDICTION OF CENTRIFUGAL COMPRESSOR
An attempt is made in the present study to investigate the superior turbulence model for simulating three dimensional flows in centrifugal compressor. The strong channelled curvature and intensive rotations prevalent in centrifugal compressor resulting high swirling and secondary flow nictitates choosing appropriate turbulence model for accurate performance predictions. The various turbulence models offered in FLUENT viz Spalart Allmaras (curvature correction), Transition SST (curvature correction), Scaled Adaptive Simulations (Curvature correction with compressibility effect), Reynolds stress model (compressibility effect) were investigated presently for Eckardt Impeller. Reynolds stress model though involves higher computational time was found to be the superior model. It is essential to investigate the onset of surge and choke for completely understanding the performance of a centrifugal compressor. Choking phenomena was observed when the speed reached 16000 rpm with relative Mach number reaching unity in the impeller region. The maximum flow rate at 16000 rpm was 0.4 kg/s per blade and remained constant then 16500 rpm. Surging was founded to initiate when the back pressure has to reach 1.8 bar resulting in zero discharge.
Numerical characteristics of a centrifugal compressor with a low flow coefficient
E3S Web of Conferences, 2019
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 + ...
Related papers
Numerical Simulation of a Centrifugal Compressor
In this paper, the tip clearance effects on flow field of a low speed centrifugal compressor without and with partial shroud (PS) fitted on to the rotor blade tip at three values of tip clearance, viz. = 2.2%, 5.1% and 7.9% of rotor blade height at the exit at three flow coefficients, namely, = 0.18, 0.28, and 0.34, was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using ANSYS CFX 15.0. The centrifugal compressor in aerodynamic requirement is that edge velocities along the impeller channel passage surfaces like hub, shroud, pressure and suction surfaces vary smoothly without sudden decelerations, which cause flow separation leading to losses. Using the periodic boundaries and defined flow conditions at inflow / exit flow and blade rotations, the turbulent viscous flow between blade channels are computed. The efficiency related parameters using average quantities, besides flow pattern in terms of velocities, streamlines and pressure distribution on blade surfaces are graphically interpreted. An attempt is also made to study the influence of pressure loads on structural deformations in the chosen blade profile. This paper highlights aero-mechanical features of centrifugal impeller obtained from several numerical simulations, which are expected to provide a sound basis for further investigations.
An Investigation on the Performance Characteristics of a Centrifugal Compressor
The design and off-design performance characteristics of single stage centrifugal compressor consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are considered. Non dimensional performance curves derived from experimental and numerical results are presented and compared. The numerical results are found to match very closely with the experimented data near the design point and deviation is observed at the both side of the designed operating point. Non-uniform pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow operating conditions. Total pressure, static pressure and velocity distributions at design and off design operation obtained from the CFD results are analysed and presented here.
Experimental Validation of the Aerodynamic Performance of an Innovative Counter-Rotating Centrifugal Compressor
Energies, 2021
Turbomachinery with double counter-rotating impellers offers more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more publications concerning axial type turbomachines are available than centrifugal ones. This work deals with a design and experimental performance analysis, applied to two counter-rotating impellers of a centrifugal compressor “CRCC”. CRCC was designed with a specifically developed tool based on mean-line approach coupled with optimization algorithms and a stream-curvature through-flow method to satisfy the design criteria. This paper presents an experimental validation of the CRCC design tool and its performances against the baseline “SR”, composed of one centrifugal impeller and a volute for which experimental data are available. CRCC numeric simulations are also validated by experimental data. For a fair comparison between CRCC and SR, the same volut...
An Analysis Method for Estimating the Impeller Performance Characteristics of a Centrifugal Compressor
유체기계 연구개발 발표회 논문집, 2015
The prediction and design of the aerodynamic performance of a compressor are crucial requirements to properly evaluate the aerodynamic performance and characteristics during preliminary design of a centrifugal compressor because it is not clear to figure out the internal flow property of a compressor including complicated three dimensional turbulent flow. In this study the industrial centrifugal compressor was calculated for variations of mass flow and blade Mach number with 2 cases of different number of diffuser vanes. One of the major cause of the impeller loss is the pressure drop when the operating mass flow rate closes to choking flow coefficient. Momentum transfer and loss characteristics of the impeller are important to understand impeller characteristics. The method was suggested to estimate the impeller performance characteristics.
Parametric Study on Impeller Exit Blade Width Variation on Centrifugal Compressor Performance
2017
The work addresses an imperious issue of enhancing centrifugal flow compressor performance by modifying the impeller blade design. Recent advancements have reported in enhancement of centrifugal compressor performance by the impeller with extended shroud by 10%. Present work extends to explore the significance geometric and design parametric variation of varying exit blade width and its implications on the compressor performance. Numerical simulations were carried out for the selected cases of extended shroud by 10% along with the width at exit blade width increased by 5% and 10%. The numerical predictions were validated with the compressor theory and matched reasonably well. Results indicates higher static pressure rise with reduced losses and increased efficiency with exit blade width variation. The stagnation pressure distribution increases at exit of diffuser due to rotating vaneless diffuser. The presence of rotating vaneless diffuser yields smooth entry flow profiles, thereby ...
Investigation of a centrifugal compressor and study of the area ratio and TIP clearance effects on performance
Journal of Thermal Science, 2008
In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically.
CFX ANALYSIS OF AN IMPELLER BLADE DESIGN OF CENTRIFUGAL COMPRESSOR
IRJET, 2022
Turbochargers are devices that increase the output power of an internal combustion engine by forcing extra compressed air into the combustion chamber. An accurate and sustainable design of the turbocharger will improve the efficiency of our combustion engine. The most important part of the centrifugal compressor used to compress air is the impeller. Radial impellers have wide range of applications in turbochargers. The aim of this project is to design an impeller blade with the optimum back swept angle so that it can work efficiently. The study is to design and optimize an impeller blade using CFX analysis in Ansys software. The back swept angle will be changed and iterations will be taken until an optimum angle is found. The output data obtained from the analysis will be analyzed and parameters such as pressure ratio, Mach number and flow rate will be considered. Thus, an efficient blade design will help in improving the air flow distribution in the impeller and will in turn increase the overall efficiency of the turbocharger.
Khaled M. S. Eldalil "Experimental Study of Centrifugal Compressor Characteristics with Slotted Impeller blades
The flow in centrifugal compressors is characterized by its stable margin at all speeds of rotation. In this study an experimental measurements are carried out by using slots in the impeller blades at a shroud distance of 30 % from the exit of the blade. It is found that the stable margin is increased due to minimizing the boundary layer growth near the exit part of the blade at off and design speeds, and hence increasing the stable margin in two directions, the first by decreasing the minimum flow rate and surge margin and the second by increasing the maximum mass flow rate. It was found that the surge margin is decreased by 24% and the maximum flow rate is increased by 16.5% and hence, the total stable margin is increased by 60 %. The deriving power of the compressor is decreased due to decreasing the impeller losses. It was found that the losses are decreased from 30-35 % to about 2-3 % at medium speeds. The pressure ratio is not increased at all speeds but the efficiency is incr...
Numerical Analysis of Blade Geometry Generation Techniques for Centrifugal Compressors
Process Industries, 2006
It is a known fact that machined impellers result in improved compressor performance compared to cast impellers of the same design. The performance improvements can be attributed to better surface finish, more accurate geometric definition (tighter dimensional tolerances), well defined edges, and the lack of blade tip fillet on shrouded impellers. In addition, it has been observed through experimental investigations that the construction method of the impellers has an impact on performance. For flank-milled machined impellers, a hub and shroud blade profile is connected by pre-determined straight-line-elements (SLE) - which would correspond to a tool path - to generate the blade surface according to the design intent of the compressor engineer. For cast impellers, the method of connecting hub and shroud blade profile points leads to an arbitrary surface definition and is dependent upon a designer's interpretation of blade profile data and/or the solid model, as well as the CAD s...
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.