Abstract
This work investigates loss model sets based on empirical loss correlations for subsonic centrifugal compressors. These loss models in combination with off-design performance prediction algorithms make up an essential tool in predicting off-design behaviour of turbomachines. This is important since turbomachines rarely work under design conditions. This study employs an off-design performance prediction algorithm based on an iterative process from Galvas. Modelling of ten different loss mechanisms and physical phenomena is involved in this approach and is thoroughly described in this work. Geometries of two subsonic compressors were reconstructed and used in the evaluation of individual loss correlations in order to obtain a suitable loss model. Results of these variations are compared to experimental data. In addition, 4608 loss model sets were created by taking all possible combinations of individual loss estimations from which three promising candidates were selected for further investigation. Finally, off-design performance of both centrifugal compressors was computed. These results were compared to experimental data and to other loss model sets from literature. The newly composed loss model set No. 2137 approximates experimental data over a 21.2% better in relative error than the recent Zhang set and nearly a 36.7% better than the outdated Oh’s set. Therefore, set No. 2137 may contribute to higher precision of centrifugal turbomachines’ off-design predictions in the upcoming research.
Highlights
Compressors are machines serving to deliver compressed air
Off-design performance prediction of a centrifugal compressor is presented in this paper
Results of previously discussed methodology and empirical correlations for individual loss mechanisms in the centrifugal compressor in comparison with experimental data by Eckardt [20,21] are presented. Eckardt performed these experiments on a test rig where the centrifugal compressor was driven by a DC-motor with a maximum power input of about 1500 kW
Summary
Compressors are machines serving to deliver compressed air. Compressed air is useful in various industrial applications e.g., gas transportation, protective atmosphere of food, wastewater treatment [1] or combustion engines, where compressed air enhances power output through turbocharging. The general idea is to have the airflow both coming and exiting in the axial direction Their compression ratio per stage is lower and is often designed as multistage, i.e., with multiple rows of rotor and stator blades according to [3]. Aungier provided a comprehensive mean streamline aerodynamic performance prediction procedure for centrifugal compressor stages in [12], where many empirical loss correlations were presented and tested on various compressor geometries. Eckardt’s subsonic compressors published in [20] were chosen as test geometries for this paper; shock loss is excluded Performance parameters of these compressors are evaluated in a vaneless diffuser configuration as in [21], vaned diffuser loss mechanisms and correlations are excluded
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