Aerothermodynamics and operation of turbine system under unsteady pulsating flow

An assessment of a turbine system operating under highly pulsating flow environment typically found in vehicular turbochargers is made to: identify the key operating parameters, enable the formulation of a reduced order model, delineate the sources of loss and suggest strategies for performance improvement. The turbine system consists of a scroll-volute followed by a turbine wheel and then a diffuser. The assessment includes calculating unsteady three-dimensional flow in the turbine system followed by in-depth interrogation complemented with flow modeling. The key findings are (1) The flow mechanisms behind the turbine wheel performance, the diffuser loss and the wastegate port loss appear locally quasi-steady such that we can characterize the performance of the components based on a series of steady calculations subjected to varying inlet conditions reflecting the inlet flow pulsation; (2) the operation of scroll-volute and the diffuser pressure recovery can be adequately determined using a quasi-one-dimensional unsteady flow model; (3) A significant fraction of the loss that is not from skin frictions occurs downstream of turbine wheel exit (18%pts out of 34%pts in Peak Torque and 20%pts out of 56%pts in Turbo Initial Transient based on cycle loss debit); (4) The condition of maximum power extraction on unsteady pulsating environment can be approximated with a simple modeling of volute storage effect. A physically consistent definition of ideal power that elucidates the role of unsteadiness in an unsteady turbine system is derived; it informs one on what the extractable power is compared to what it could be for an ideal system. Finally the findings are used to define the required attributes of methodology for estimating efficiency with a specified uncertainty bandwidth.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2015

Author dc:creator

• Lee, Jinwook, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Choon S. Tan and Borislav T. Sirakov.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/98692

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/98692