The defining characteristic of centrifugal compressors is that head is determined by the volume flow through the unit. Development of a design method for centrifugal compressors by kangsoo im this dissertation is the development of a centrifugal compressor design and analysis code that can be used to inexpensively design and analyze the performance of a centrifugal compressor. Impellerdiffuser interaction in a centrifugal compressor journal. Numerical investigation of impellervaned diffuser interaction in a. Although centrifugal compressors are sometimes called radial compressors, most of the flow exiting a centrifugal impeller does not travel in a radial direction. Particle image velocimetry characterization of highspeed. Empirical design considerations for industrial centrifugal. Impellerdiffuser interaction in centrifugal pca engineers compressor stage with a vaned diffuser at high pressure ratio using different techniques to model the rotorstator interaction. One cause of these instabilities is the rotating stall occurring in vaneless diffuser. In the new model, the interaction between the impeller and the diffuser vane is focused on. The unsteady phenomenon abounds in centrifugal compressors and significantly affects the compressor performance.
Today, the centrifugal compressors are used for variety of applications in oil and gas industry thus, they are considered as one of the fundamental component. This paper reports several cfd analyses of a centrifugal compressor stage with a vaned diffuser at high pressure ratio using different techniques to model the rotorstator interaction. Request pdf impellerdiffuser interaction in centrifugal compressors this paper reports several cfd analyses of a centrifugal compressor stage with a. The impeller pulls the working fluid in axially from the inlet. The radial gap between the impeller and diffuser typically varies between about 5 and 15% of the impeller tip radius which is only a small fraction of the chord of the two blade rows. Flow analysis in centrifugal compressor vaneless diffusers 353 diffuser walls as shown by mean velocities at s 8. Numerical and experimental investigation of flow mechanism. Numerical investigation of the performance and flow behaviour. However unsteady impellerdiffuserinteractions are believed to have a strong influence on the flow both in the impeller and the diffuser of centrifugal compressor stages. Special emphasis is placed on impeller and diffuser interaction and design as a result of recent investigations. Centrifugal compressor introduction free download as powerpoint presentation. In centrifugal compressors, these flow passages can either be the impeller inlet, or the inlet to diffuser vanes. The radial gap ratio and its effects on the performance of lowpressure ratio centrifugal compressors has been investigated thoroughly. Operation of centrifugal compressors in choke conditions.
Many research works have been undertaken using experimental and numerical methods on the impellerdiffuser interactive phenomenon. Effect of impellerdiffuser radial gap ratio in a centrifugal. Both operation near the surge limit and in choke leads to flow conditions that are severely different from the flow conditions at the compressors design point. Time dependent simulations are used to characterize the unsteady impeller blade loading due to imipellerdiffuser interaction in centrifugal compressor stages. Centrifugal compressors are similar in many ways to other turbomachinery and are compared and contrasted as follows.
Numerical investigation of the performance and flow. This manual does not for designing centrifugal compressor and those parts. May 23, 2012 a numerical study of the unsteady interaction effects on diffuser performance in a centrifugal compressor 23 september 20 journal of turbomachinery, vol. A compressor is a device that transfers energy to a gaseous fluid for the purpose of raising the pressure of the fluid. Scaling of impeller response to impellerdiffuser interactions in centrifugal compressors research and teaching output of the mit community. Scaling of impeller response to impellerdiffuser interactions in centrifugal compressors. Generation mechanisms of rotating stall and surge in. Centrifugal compressors are often equipped with vaned diffusers of both the low and high solidity type. Experimental investigation of impellerdiffuser interaction in a centrifugal compressor csme forum 2006, calgary. The portion 38 of the working fluid passing over the vane is injected into.
The interaction between impeller and diffuser is considered to have strong influence on the flow in centrifugal compressors. Passage wake was no longer discernible, although boundary layer on shroud surface remained thicker than that on hub. In their work, they used the tt method which leads to the reduction of the computational effort by a factor of 5. Forced response of a centrifugal compressor stage due to the. Suction throttling discharge throttling adjustable inlet guide vanes speed variation bearings. This paper provides some empirical information for designing industrial centrifugal compressors with a focus on the impeller. Stage single passage impellerdiffuser, full volute frozen rotor full 360 degrees. In order to study the influence of vaned diffuser meridional outlet section with a different width ratio of the modified centrifugal compressor.
Design of a singlestage centrifugal compressor and numerical. The radial gap ratio between the impeller and the diffuser vanes plays an important role in the. Characterization of this type of impellerdiffuser interaction is not only important from a hcf losses characterized by considerably larger entropy production at the impeller 6, and thus affecting the stage ef. Downstream of the impeller in the flow path, it is the diffuser s responsibility to convert the kinetic energy high velocity of the gas into pressure by gradually slowing diffusing the gas velocity. Cfd analysis of impeller diffuser interaction in a centrifugal compressor with twisted vaned diffuser springerlink. A recent innovation is to include examples of actual design practice. The impact of unsteady impeller diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a timeaveraged change in impeller loss, blockage and slip. It is found from the literature that the effect of radial gap between impeller and diffuser on the interaction and on the performance of the fan has not been the focus of attention. A diffuser 30 for a centrifugal compressor 60 having a flow slot 34 formed between the leading edge portion 36 of a diffuser vane 32 and an adjoining diffuser wall 70 for the passage of working fluid 67 over the vane from the pressure side 40 to the suction side 42 of the vane.
Centrifugal compressors are similar to axial compressors in that they are rotating airfoilbased compressors. Moreover, the performance of the centrifugal compressor was dependent on. In the case of an axialinlet centrifugal compressor typical of integrally geared units, an appropriate length of pipe serves to smooth. Unsteady flow in a turbocharger centrifugal compressor value paper authors. Impellerdiffuser interaction in centrifugal compressors aiaa arc. Downstream of the impeller in the flow path, it is the diffusers responsibility to convert the kinetic energy high velocity of the gas into pressure by gradually slowing diffusing the gas velocity.
The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. Experimental flow data recorded on a low speed centrifugal compressor rig are compared with theoretical predictions of the diffuser field. Numerical investigation of the performance and flow behaviour of centrifugal compressors. Experimental investigation of diffuser hub injection to improve centrifugal compressor stability gary j. Omar content applications design features casing barrel and internals rotor and impellers sealing and sealing gas system lube oil system and bearing.
Impellervaned diffuser interaction in a centrifugal. Request pdf impellerdiffuser interaction in centrifugal compressors. Forced response of a centrifugal compressor stage due to the impellerdiffuser interaction. Threedimensional blade profiles, diffuser flow angles, crossover bend curvature, area ratio, and return channel vane shapes are optimized for each impeller stage to. In literature, riblets have been extensively tested, although the physical mechanisms are not fully understood, it is definitely sure that riblets with proper. Designing a highly efficiency impeller with a wide operation range can ensure overall stage design success. Flow analysis in centrifugal compressor vaneless diffusers. Jun 29, 2018 the defining characteristic of centrifugal compressors is that head is determined by the volume flow through the unit. As surge can occur during acceleration of the compressor speed, it is of major concern to develop controllers. Numerical study on the effect of interaction vaned diffuser with impeller on the performance of a modified centrifugal compressor volume 30 issue 2 l. The effect of impellerdiffuser interactions on diffuser.
A study of diffuserrotor interaction in a centrifugal. There are two key components to a centrifugal compressor. A study has been conducted, using an unsteady threedimensional reynoldsaveraged navierstokes simulation, to define the effect of impeller diffuser interaction on the performance of a centrifugal compressor stage. A short history of diffusers for centrifugal machines, authorjapikse, year2018. Numerical analysis of radiver test case in the present work, a numerical analysis of the radiver test case was carried. Moreover, the geometry is often asymmetric due to the volute shape. Experimental investigations on the rotor stator interaction for centrifugal compressors were performed by gallier et al. As centrifugal compressors find a huge number of applications in industry and in aeroengines, the detailed analysis and comprehension of the impeller vaned diffuser interaction is of interest to improve the efficiency and the operating range. Cfd analysis of impellerdiffuser interaction in a centrifugal compressor with twisted vaned diffuser springerlink.
Therefore, a stateoftheart industrial design compressor from a turbocharging application has been integrated into the highspeed centrifugal compressor facility rigi, located at eth zurich. Centrifugal compressors overview gas compressor turbine. The compressor is equipped with a ported shroud, which is supported by four asymmetrically arranged ribs. Centrifugal compressor stages for a wide range of applications comprise an impeller closely coupled to a vaned diffuser. Numerical study on the effect of interaction vaned diffuser. In these cases, the complexity of the unsteady pressure field increases due to the presence of an additional blade row the vaned diffuser. Research on a centrifugal compressor of variable geometry. Pdf effects of radial gap ratio between impeller and. Since compressors are variable speed machines, it is of interest to investigate the in. Ozturk et aleffect of impeller diffuser radial gap ratio in a centrifugal pump diffuser, these oscillations are progressively reduced due to divergence and absorption. Rather, the flow travels to a large extent in a tangential direction.
Effects of impellerdiffuser interaction on centrifugal compressor. However, the knowledge about this influence is still not satisfying. Characterization of unsteady loading due to impeller. Effect of vaned diffuser on a modified turbocharger. In the case of an axialinlet centrifugal compressor typical of integrally geared units, an appropriate length of pipe serves to smooth the flow of gas into the eye of the first impeller. Particle image velocity investigation of a high speed.
A study has been conducted, using an unsteady threedimensional reynoldsaveraged navierstokes simulation, to define the effect of impellerdiffuser interaction on the performance of a centrifugal compressor stage. The effect of impellerdiffuser interactions on diffuser performance in a centrifugal compressor 7 october 2016 engineering applications of computational fluid mechanics, vol. A conventional steady stage calculation with a mixingplane type interface between the rotor and stator was used as a baseline. Single stage centrifugal compressors elliott group. The impact of unsteady impellerdiffuser interaction, primarily through the impeller tip clearance flow, is reflected through a timeaveraged change in impeller loss, blockage and slip. Numerical study on the effect of interaction vaned. Results for four diffuser geometries are presented covering variation of the blade number, stagger angle, and radial separation of the rotor and diffuser. Influence of number of impeller and diffuser blades on the pressure recovery of centrifugal fan madhwesh n1. Ozturk et aleffect of impellerdiffuser radial gap ratio in a centrifugal pump diffuser, these oscillations are progressively reduced due to divergence and absorption. In most cases the highly unsteady flow field be tween the impeller exit region and the diffuser throat has a dominating influence on efficiency, operating perform. The general aspect of stage matching between front and rear blocks in a multistage axial compressor, which was pretty well described in most of turbomachinery or gas turbine engine textbooks, has been frequently quoted in matching between the impeller and the vaned diffuser of a centrifugal compressor by some group of people. Impellerdiffuser interaction in centrifugal compressors chris robinson pca engineers limited lincoln, uk michael casey pca engineers limited, lincoln, uk and itsm, university of stuttgart brad hutchinson ansys, inc.
Impellerdiffuser interaction in centrifugal compressors request. Unlike the axial compressors, the flow leaves the centrifugal impeller radially due to the centrifugal and coriolis forces within the impeller. Experimental investigation of impeller diffuser interaction in a centrifugal compressor csme forum 2006, calgary rita patel, eric savory, robert martinuzzi. The impeller is the key part of the centrifugal stage. However, the knowledge about this influence is still not.
At present, offdesign centrifugal compressor suffers from great instabilities, such as rotating stall and surge, which lead to work failure, strong pressure fluctuations, and violent vibrations of the entire system. Centrifugal compressor surge and speed control control. Impellerdiffuser interaction in a centrifugal compressor. Impeller diffuser interaction in centrifugal compressors chris robinson pca engineers limited lincoln, uk michael casey pca engineers limited, lincoln, uk and itsm, university of stuttgart brad hutchinson ansys, inc. The excitation source of the impeller blades is the unsteady fluidstructure interaction originating from the vaned diffusers potential field effect. Pdf impeller volute and diffuser interaction semantic. Time dependent simulations are used to characterize the unsteady impeller blade loading due to imipeller diffuser interaction in centrifugal compressor stages. Elliott single stage centrifugal compressors operate in a wide range of conditions due to the standardized impeller design and the vaneless diffuser.
The interaction between impeller and vaned diffuser is far more difficult to model than configurations with vaneless diffuser 1,2. Effects of radial gap ratio between impeller and vaned. Manual purpose to be used for selection, application into the system, power and cooling water estimation. As a result, the relative motion between impeller and volute generates an unstableness which affects not only the overall pump performance, but is also responsible for pressure fluctuations. During that time it has been continuously revised to reflect the latest understanding and best practices, including examples of actual design practice. Cfd analysis on the effect of radial gap on impeller. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between the compressor impeller along the vaned diffuser. Pdf impeller volute and diffuser interaction semantic scholar. Mechanism of stall and surge in a centrifugal compressor with. The investigated centrifugal compressor is presented in fig. Design of a singlestage centrifugal compressor and.
Similarities to axial compressor cutaway showing an axicentrifugal compressor gas turbine. As a result, different stagger angles can influence the stage. Diffusers can be vaneless, vaned or an alternating combination. Impellerdiffuser interaction in centrifugal compressors. The effect of variation of diffuser radius ratio on the performance of a centrifugal compressor stage with vaneless diffuser vld, low solidity vaned diffuser lsvd, and twisted vaned diffuser. Pdf on sep 1, 2007, aishwarjya gogoi and others published effect of impellerdiffuser interaction on centrifugal compressor. A numerical study of the unsteady interaction effects on diffuser performance in a centrifugal compressor 23 september 20 journal of turbomachinery, vol.
The capability of simulations are assessed by comparing results against unsteady pressure and velocity measurements in the vaneless space. The next key component to the simple centrifugal compressor is the diffuser. This paper reports several cfd analyses of a centrifugal compressor stage with a vaned diffuser at high pressure ratio using different techniques to model the. In order to assess the flow through centrifugal compressor components, we have to introduce the concept of velocity triangles kurz, 2004, brun and kurz, 2000. This paper reports several cfd analyses of a centrifugal compressor stage with a vaned diffuser at high pressure ratio using different techniques to model the rotor. Waterloo, on, canada abstract this paper reports several cfd analyses of a centrifugal. Thus, pressure fluctuations in after the impeller, diffuser and between impeller and diffuser are effective based on performance and efficiency. Less information is available on the interaction in high speed air compressors. A numerical study that was made in a threedimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an automotive turbo charger. Characterization of unsteady loading due to impellerdiffuser. Axial velocity from hub to shroud is evidence of continuing levelling in two boundary layer flow rates. Models describing this interaction were developed in 8 and 12 for axial compressors, and in 10 and 15 a preliminary version of this paper for centrifugal compressors. Experimental investigation of impellerdiffuser interaction. Compressor impeller and matched stationary flowpath components are developed using computational fluid dynamics cfd analyses and other current design tools.
Mechanism of stall and surge in a centrifugal compressor. Scaling of impeller response to impellerdiffuser interactions. Centrifugal compressor wikimili, the best wikipedia reader. They noted that nonuniform flow at the exit of the centrifugal impeller mixes. The theoretical model was improved by spakovszky, 10 which can be used on centrifugal compressors. Forced response of a centrifugal compressor stage due to the impellerdiffuser interaction edward j. Pdf impellerdiffuser interaction in centrifugal compressors. Forced response of a centrifugal compressor stage due to. The interaction between impeller and diffuser is considered to have strong influence on the flow in highly loaded centrifugal compressors. Army research laboratory glenn research center cleveland, ohio 445 abstract results from a series of experiments to investigate whether centrifugal compressor stability could be. However, it ignores some detailed flow structures in the impeller, such as leakage flow, and is usually not used in the case of centrifugal compressors. May 23, 2012 the effect of impellerdiffuser interactions on diffuser performance in a centrifugal compressor 7 october 2016 engineering applications of computational fluid mechanics, vol. Advances and breakthroughs in diffusers for compressors and pumps.
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