Steady-state numerical simulations are an essential instrument during the design process of radial compressors for automotive turbochargers in an industrial environment. Although this method is state-of-the-art, the natural unsteadiness of the compressor flow especially close to stall and surge is suppressed by this kind of simulation.Unsteady numerical simulations of the whole compressor geometry are necessary to find unstable flow structures leading to surge. Since numerical costs and thus the time needed for unsteady simulations correlate with the size of the numerical setup, it is not possible for industrial applications to investigate unsteady operation conditions of a centrifugal compressor. On account of this fact, it would be beneficial to reduce the model and include only the most decisive components which are responsible for the significant flow phenomena within the impeller. Especially the occurrence of local instabilities leading to unstable flow conditions in the whole compressor are of note. To evaluate the transient results of the reduced model and transferring them into reality, it is necessary to know the fundamental, phenomenological differences between reduced and complete compressor model in the performance map. These differences can be identified using steady state simulation.The objective of this research paper is the investigation of the CFD simulation capabilities of a reduced radial-compressor model for steady-state operation conditions used as a robust basis for further transient analysis. Thus the results of the different model setups are compared according to several flow phenomena and limits imposed by the reduction of the numerical model shown. Simulations for both models with variation in rotational speed and air mass flow rate are performed. Experimental data is used to validate the results of the complete numerical model. The setup of the reduced model, consisting of inducer, one blade segment of the compressor wheel and the vaneless diffuser, is validated with the results of a complete model. The numerical results are conducted by a CFD analysis using the steady-state RANS approach. The numerical convergence of the steady state simulations can be much larger than the experimental operating range, particular considering low mass flow rates. Numerical convergence of the steady-state simulation below the surge margin is possible. Due to the periodicity of the reduced model, flow phenomena caused by unperiodic circumferential geometry of the volute, can not be investigated. It is therefore essential to analyze the complete stable simulation range with the steady state approach before execute URANS simulation.The complete model, in conjunction with its validation by experimental data, serves as the starting point for this research paper. The procedure and a detailed comparison of complete model results and experimental analysis, are presented in the first part of the paper by Dielenschneider et al.

On the Challenge of Determining the Surge Limit of Turbocharger Compressors: Part 2 – Capabilities of a Geometrically Reduced Numerical Model

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.