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Flow simulations with relevance to a centrifugal compressor and the eect of the inlet geometry
KTH, School of Engineering Sciences (SCI), Mechanics.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Turbocharging the internal combustion engine is one of the most effective ways to reduce the fuel consumption and fulll the green house gas emissions requierements. Nevertheless, this techinque has some limitations that need to be addressed in order to improve the turbocharger performance. The range of use of the compressor is restricted by the surgeline at low massow rates and the choke line at high massow rates. The compressor map gives valuable information of the compressor stable operating points. However, due to the space constraints in an engine compartiment, complex pipes are needed to integrate all the components correctly leading to a dierence in the compressor preformance from measurments to in-situ congurations. Computational Fluid Dynamics is a powerful tool to predict compressor maps in a shorter time and less laborious way compared to experimental measurements and obtaining data in the whole domain.The compressor map of a turbocharger compressor was calculated using a steady-state RANS approach and the Moving Reference Frames technique to handle the rotating parts of the machine, validating the method with experimental data. The  ow eld from near optimal e-ciency points to near surge was assessed identifying a strong swirling back ow at odesign conditions responsible for the e-ciency and pressure ratio drop.The eect of a 90º bent pipe upstream the compressor inlet was studied. Two counter-rotating vortices were observed to form after the bend and vanishing under the eect of the wheel rotation in evey case. It was shown that the  ow structures introduced by the bend can be benecialat near surge condition, mitigating the rotating back ow and improving the e-ciency and pressure ratio of the compressor at this particular case.

Place, publisher, year, edition, pages
2015. , 64 p.
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-194446OAI: diva2:1040617
Educational program
Master of Science in Engineering - Mechanical Engineering
Available from: 2016-10-28 Created: 2016-10-28 Last updated: 2016-10-28Bibliographically approved

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