Optimization of a Diffuser With Splitter by Numerical Simulation

Drtina, Peter; Dalbert, Peter; Rütti, K.; Schachenmann, A.

doi:10.1115/93-gt-110

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…Increasing the number of blades is an imperative solution to improve flow guidance and reduce blade loading, but this increase leads to more friction loss and a larger blockage coefficient. So, there is the insistent needing for using splitter blades, which are shorter blades inserted between full-length blades, to reduce the friction and blockage effects, consequently reducing the separation process in impeller and diffuser and avoiding choking of the flow in the throat of radial impellers and diffusers and achieving high-pressure ratio [6].…”

Section: Introductionmentioning

confidence: 99%

CFD investigation of flow through a centrifugal compressor diffuser with splitter blades

et al. 2021

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The aerodynamic losses in centrifugal compressors are mainly associated with the separated flow on the suction sides of impeller and diffuser vanes. The overall performance of such compressors can be improved by adding splitter vanes. The present work examines the effect of varying the geometrical location of the splitter vanes in the diffuser on the overall performance of a high-speed centrifugal compressor stage of a small gas turbine. To increase the pressure recovery through the diffuser, two radial sets of vanes are used. The first set of vanes (diffuser-1) is equipped with splitter vanes, placed mid-distance between the main vanes, while the vanes of the second set (diffuser-2) are conventional vanes. Flow through the compressor was simulated using the ANSYS 19 workbench program. Flow characteristics and compressor performance were obtained and analyzed for different circumferential positions of the splitting vanes relative to the main vanes of diffuser-1. The study covered seven positions of the splitter vanes including the original design of the diffuser where the splitter vanes were located at mid-distance between the main vanes. The analysis shows that, at design conditions, selecting the position of the splitter vanes to be nearer to the pressure side of the main vanes improves the stage performance. In the present study, locating the splitters at 33% of the angular distance between the main vanes leads to the best performance, and a significant improvement in the overall stage performance is recorded. The pressure recovery coefficient is raised by about 17%, the pressure ratio is increased by about 1.13%, and the stage efficiency is increased by about 2.01%, compared to the original splitter position. Performance improvement is related to the suppression of the flow separation and the more uniformity of flow. On the contrary, further moving the splitter closer to the main blade, the pressure recovery coefficient is decreased by about 2% than the position of 33% of the angular distance, but still higher than the original position by about 15% and a limited improvement in the compressor performance is noticed. Moving the splitter far out the main blade annihilates the static pressure recovery of the diffuser by about 2:7% compared with the original position. So, for the investigated compressor, the best position of the splitter blade in the circumferential direction, which provides the best stage performance in our parametric analysis, is not necessary to be at the mid-angular distance between the diffuser’s main blades, but it is achieved by moving the splitter to about 33% of the angular distance where the diminished loss from the suppressed flow separation is more prevailing and the instigated friction losses from splitter surfaces are less critical.

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Section: Introductionmentioning

confidence: 99%

CFD investigation of flow through a centrifugal compressor diffuser with splitter blades

et al. 2021

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Investigation of an Inversely Designed Centrifugal Compressor Stage—Part I: Design and Numerical Verification

Zangeneh

Schleer

Plöger³

et al. 2004

Journal of Turbomachinery

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In this paper the three-dimensional inverse design code TURBOdesign-1 is applied to the design of the blade geometry of a centrifugal compressor impeller with splitter blades. In the design of conventional impellers the splitter blades normally have the same geometry as the full blades and are placed at mid-pitch location between the two full blades, which can usually result in a mismatch between the flow angle and blade angles at the splitter leading edge. In the inverse design method the splitter and full blade geometry is computed independently for a specified distribution of blade loading on the splitter and full blades. In this paper the basic design methodology is outlined and then the flow in the conventional and inverse designed impeller is compared in detail by using computational fluid dynamics (CFD) code TASCflow. The CFD results confirm that the inverse design impeller has a more uniform exit flow, better control of tip leakage flow and higher efficiency than the conventional impeller. The results also show that the shape of the trailing edge geometry has a very appreciable effect on the impeller Euler head and this must be accurately modeled in all CFD computations to ensure closer match between CFD and experimental results. Detailed measurements are presented in part II of the paper.

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Optimization of a Diffuser With Splitter by Numerical Simulation

Cited by 2 publications

References 11 publications

CFD investigation of flow through a centrifugal compressor diffuser with splitter blades

CFD investigation of flow through a centrifugal compressor diffuser with splitter blades

Investigation of an Inversely Designed Centrifugal Compressor Stage—Part I: Design and Numerical Verification

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