The challenge to be able to predict the stability limit of high speed centrifugal compressors is particularly strategic during the preliminary design phase. Furthermore, to be able to predict the limit massflow rate with simplified numerical models (which does not require excessive computational resources) is very useful. In the literature several methods to predict the chocking condition are described, while there is a lack of contributions for the surge condition limit. The authors had published a criterion to predict the surge line valid for centrifugal compressors with vaned diffuser. The above criterion did not show sufficient accuracy when applied to centrifugal stages with vaneless diffuser. For this reason, in the first part of the paper an in-depth fluid dynamic analysis has been carried out in order to identify the main phenomena that can trig the instability in this kind of compressors. The analysis has shown that the rotational speed is a discriminating factor in the phenomenology. In this second part of the paper different criteria to predict the limit massflow rate for centrifugal compressors with vaneless diffuser are discussed. They have been based on fluid dynamic phenomena observed using some parameters extracted from the flow features that cause the operating limits. The criteria are based on selected parameters defined by the authors that can be obtained through simplified CFD models without the need for a complete 3D unsteady analysis. At low rotational speeds the critical flow angle criterion (a modified version of the Senoo criterion) and the recirculation zone criterion for the diffuser have been developed. A criterion based on the diffusion ratio has been selected for the impeller. At high rotational speeds a criterion based on the flow simulation inside the volute has been proposed. The above criteria have been applied to a set of centrifugal compressors for automotive turbocharging in order to highlight their accuracy in the prediction of the limit mass flow rate.


Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part II \u2014 The Development of Prediction Criteria

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

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.