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Title: Improved meanline modelling of centrifugal compressors for automotive turbochargers
Author: Harley, Peter Xavier Leon
ISNI:       0000 0004 5372 1493
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2014
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This work presents a method to improve the prediction accuracy of a meanline modelling approach for automotive turbocharger style centrifugal compressors. This has been achieved using a novel active flow zone theory which has been combined with an existing single zone meanllne modelling technique and an existing collection of loss models. The work begins by identifying the weaknesses in the existing meanline modelling techniques available in open literature before identifying single zone modelling as being the most suitable platform for further impeller modelling improvements. During the development of the meanline modelling technique three turbocharger compressor datasets were provided by IHI Charging Systems International for analysis. The various loss model collections available in open literature were then benchmarked and a particular set of loss models was identified as being the most robust and providing the best performance prediction accuracy for the compressors of interest. With all of tile mean line modelling techniques and loss model collections assessed accuracy was always lost toward surge and at high tip speeds. The test data always showed a flattening of the pressure ratio characteristic curve for a fixed speed toward surge to an extent that the pressure ratio effectively remains constant. It was hypothesised that impeller inlet recirculation was driving this performance toward surge and therefore this was investigated using a single passage 3D CFD model. Using the data collected from the CFD simulations for the compressors it was shown that the scale of the impeller inlet recirculation varies predictably across a range of operating conditions and compressors, for this reason a correlation was developed to represent this. The variation of the inlet flow conditions were Investigated in the same fashion and it was discovered that they too varied predictably; correlations were developed at the impeller inlet for the size of the recirculating zone, the active flow total temperature, and the active flow circumferential component of velocity. Based on the data collected from the CFD a novel concept for impeller work input was suggested whereby the active flow zone is the only part of the Impeller contributing to pressure rise; this is the basis for the novel mean line modelling technique which is described in this document. The new method was shown to provide improved performance prediction accuracy toward surge as targeted, All of the modelling techniques were then bencl1marked further using two additional compressors provided by the industrial sponsor, Detailed inter-stage pressure measurements are presented at the impeller leading and trailing edge and the weaknesses in all of the modelling methods used are exposed with the aim of inspiring future work,
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available