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Experimental investigation of upstream installation effects on the turbocharger compressor map
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).ORCID iD: 0000-0002-4937-8915
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).ORCID iD: 0000-0001-9483-7992
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).ORCID iD: 0000-0001-7330-6965
2016 (English)In: The 12th International Conference on Turbochargers and Turbocharging, London, UK, 17-18 May, 2016, 2016Conference paper, Published paper (Refereed)
Abstract [en]

This paper experimentally investigates the effects of an upstream bended pipe on the compressor speedline slopes and surge line. Different orientation angles for the incoming bended pipe relative to the compressor scroll are investigated. The tests were carried out on a cold gas stand on a passenger car sized turbocharger. A bended pipe upstream of the compressor leads to an increase of the surge margin. This effect does not depend on the orientation of the bend. Comparisons with a straight inlet with artificially generated pressure losses indicate that the increase in operating range is an effect of the pressure losses generated in the bend.

Place, publisher, year, edition, pages
2016.
Keyword [en]
Turbochargers, Centrifugal Compressors, Compressor Surge
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-191296ISBN: 978-0-9572374-7-6 (print)OAI: oai:DiVA.org:kth-191296DiVA: diva2:955877
Conference
The 12th International Conference on Turbochargers and Turbocharging, London, UK, 17-18 May, 2016
Note

QC 20160829

Available from: 2016-08-26 Created: 2016-08-26 Last updated: 2017-05-08Bibliographically approved
In thesis
1. On Stability and Surge in Turbocharger Compressors
Open this publication in new window or tab >>On Stability and Surge in Turbocharger Compressors
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Turbochargers are used on many automotive internal combustion engines to increase power density. The broad operating range of the engine also requires a wide range of the turbocharger compressor. At low mass flows, however, turbo compressor operation becomes unstable and eventually enters surge. Surge is characterized by large oscillations in mass flow and pressure. Due to the associated noise, control problems, and possibility of mechanical component damage, this has to be avoided.

Different indicators exist to classify compressor operation as stable or unstable on a gas stand. They are based on pressure oscillations, speed oscillations, or inlet temperature increase. In this thesis, a new stability indicator is proposed based on the Hurst exponent of the pressure signal. The Hurst exponent is a number between zero and one that describes what kind of long-term correlations are present in a time series.

Data from three cold gas stand experiments are analyzed using this criterion. Results show that the Hurst exponent of the compressor outlet pressure signal has good characteristics. Stable operation is being indicated by values larger than 0.5. As compressor operation moves towards the surge line, the Hurst exponent decreases towards zero. An additional distinction between the long-term correlations of small and large amplitude fluctuations by means of higher order Hurst exponents can be used as an early warning indicator.

Further tests using compressor housing accelerometers show that the Hurst exponent is not a good choice for real-time surge detection on the engine. Reasons are the long required sampling time compared to competing methods, and the fact that other periodically repeating oscillations lead to Hurst exponents close to zero independent of compressor operation.

Abstract [sv]

Turboladdare används ofta på förbränningsmotorer för att öka motorns effekttäthet. Motorns breda driftområde ställer krav på ett brett driftområde för turboladdarens kompressor. Vid låga massflöden blir kompressordriften dock mindre stabil, och surge kan uppträda. Surge innebär stora oscillationer i tryck och massflöde genom kompressorn. På grund av oljud, reglerproblem och risken för mekaniska skador vill man undvika surge.

Det finns indikatorer för att bedöma kompressorns stabilitet på ett gas stand. Indikatorerna är baserade på tryckoscillationer, varvtalsoscillationer, eller temperaturökning i gasen i kompressorinloppet. I denna avhandling presenteras en ny indikator baserad på Hurst-exponenten, beräknad på trycksignalen. Hurst-exponenten är ett tal mellan noll och ett som beskriver vilka typer av långtidskorrelationer det finns i signalen.

Mätningar från tre gas-stand-experiment har analyserats på detta sätt. Analyserna visar att Hurst-exponenten baserad på kompressorutloppstrycket fungerar bra som som surgeindikator. Stabil drift av kompressorn indikeras av att Hurst-exponenten är större än 0.5. När kompressordriftpunkten närmar sig surgelinjen faller Hurst-exponenten mot noll. En distinktion mellan oscillationer med små och stora amplituder kan används för att få en tidig varning.

Analyser av vibrationsmätningar på kompressorhuset vid motorapplikation visar att Hurst-exponenten inte är lämplig som realtidsindikator på en motor. Detta kommer sig dels av att data behöver samlas in under en längre tid än med andra tänkbara indikatorer, dels av att andra periodiska oscillationer i signalen kopplade till motorns naturliga beteende leder till Hurst-exponenter nära noll även vid stabil kompressordrift.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2017. 109 p.
Series
TRITA-MMK, ISSN 1400-1179
Keyword
Turbocharger, Radial Compressor, Stability, Surge, Hurst exponent, Fractals
National Category
Mechanical Engineering
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-206737 (URN)978-91-7729-378-1 (ISBN)
Public defence
2017-06-02, D1, Lindstedtsvägen 17, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
CCGEx - Compressor off-Design
Note

QC 20170510

Available from: 2017-05-10 Created: 2017-05-08 Last updated: 2017-05-10Bibliographically approved

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Kerres, BertrandMihaescu, Mihai

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