This thesis presents the results from measurements taken during the transient unstable operation of an axial-flow transonic core-compressor rotor. The measurements were taken to better understand the unstable flow physics of transonic rotors. The rotor, commonly referred to as Rotor 37, was designed by NASA Lewis to be the first stage of an advanced, eight-stage, core-compressor having a high pressure ratio (about 20:1), good efficiency and sufficient stall margin. The rotor was tested without the presence of a stator (or any of the following seven stages) at the NASA Lewis single-stage, high-speed, core-compressor test-rig. The measurements were obtained with a single circumferential, high-response, total pressure and total temperature probe. The measurements were taken immediately after the machine was ’tripped’ into unstable operation by slowly closing the downstream throttle valve. Measurements were obtained at several different span-wise locations and at two different operating speeds. The rotor was shown to exhibit many of the same characteristics typical of low-speed axial-flow machines. Both rotating stall cells and surge cycles were present during unstable operation. The surge cycles present immediately after the inception of unstable operation involved a large-extent single-cell type rotating stall that was present only during the first half of the surge cycles (the second half of these surge cycles involved operation in the stable operating region). However, as the unstable operation progressed (approximately three to five surge cycles later), surge cycles were present that contained a multiple-cell smaller-extent type rotating stall that existed throughout the entire surge cycle with no partial operation in the stable operating region. Thus, compressor system recovery from single-cell large-extent rotating stall (partial operation in stable operating range during the surge cycle) is more probable than recovery from multiple-cell small-extent rotating stall (no operation in stable operating range during the surge cycle). Rotor wheel speed was shown to be an important variable in influencing the form of unstable operation. Surge and rotating stall were shown to be coupled during the unstable operation. Furthermore, the surge/stall coupling was shown to be related more by pressure interactions than by temperature or efficiency interactions. Also, this high hub-tip ratio transonic rotor was shown to exhibit instantaneous stalling across the entire blade span (typical of low-speed, high hub-tip ratio machines). Attempts to fit the data to Greitzer’s one-dimensional lumped-parameter model are presented and the reasons for poor agreement are discussed. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/43616 |
| Date | 10 July 2009 |
| Creators | Osborne, Denver Jackson Jr. |
| Contributors | Mechanical Engineering |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | xiv, 113 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 27645832, LD5655.V855_1992.O836.pdf |
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