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- Genre: Masters Thesis
Description
Modern day gas turbine designers face the problem of hot mainstream gas ingestion into rotor-stator disk cavities. To counter this ingestion, seals are installed on the rotor and stator disk rims and purge air, bled off from the compressor, is injected into the cavities. It is desirable to reduce the supply of purge air as this decreases the net power output as well as efficiency of the gas turbine. Since the purge air influences the disk cavity flow field and effectively the amount of ingestion, the aim of this work was to study the cavity velocity field experimentally using Particle Image Velocimetry (PIV). Experiments were carried out in a model single-stage axial flow turbine set-up that featured blades as well as vanes, with purge air supplied at the hub of the rotor-stator disk cavity. Along with the rotor and stator rim seals, an inner labyrinth seal was provided which split the disk cavity into a rim cavity and an inner cavity. First, static gage pressure distribution was measured to ensure that nominally steady flow conditions had been achieved. The PIV experiments were then performed to map the velocity field on the radial-tangential plane within the rim cavity at four axial locations. Instantaneous velocity maps obtained by PIV were analyzed sector-by-sector to understand the rim cavity flow field. It was observed that the tangential velocity dominated the cavity flow at low purge air flow rate, its dominance decreasing with increase in the purge air flow rate. Radially inboard of the rim cavity, negative radial velocity near the stator surface and positive radial velocity near the rotor surface indicated the presence of a recirculation region in the cavity whose radial extent increased with increase in the purge air flow rate. Qualitative flow streamline patterns are plotted within the rim cavity for different experimental conditions by combining the PIV map information with ingestion measurements within the cavity as reported in Thiagarajan (2013).
ContributorsPathak, Parag (Author) / Roy, Ramendra P (Thesis advisor) / Calhoun, Ronald (Committee member) / Lee, Taewoo (Committee member) / Arizona State University (Publisher)
Created2013
Description
American Primitive is a composition written for wind ensemble with an instrumentation of flute, oboe, clarinet, bass clarinet, alto, tenor, and baritone saxophones, trumpet, horn, trombone, euphonium, tuba, piano, and percussion. The piece is approximately twelve minutes in duration and was written September - December 2013. American Primitive is absolute music (i.e. it does not follow a specific narrative) comprising blocks of distinct, contrasting gestures which bookend a central region of delicate textural layering and minimal gestural contrast. Though three gestures (a descending interval followed by a smaller ascending interval, a dynamic swell, and a chordal "chop") were consciously employed throughout, it is the first gesture of the three that creates a sense of unification and overall coherence to the work. Additionally, the work challenges listeners' expectations of traditional wind ensemble music by featuring the trumpet as a quasi-soloist whose material is predominately inspired by transcriptions of jazz solos. This jazz-inspired material is at times mimicked and further developed by the ensemble, also often in a soloistic manner while the trumpet maintains its role throughout. This interplay of dialogue between the "soloists" and the "ensemble" further skews listeners' conceptions of traditional wind ensemble music by featuring almost every instrument in the ensemble. Though the term "American Primitive" is usually associated with the "naïve art" movement, it bears no association to the music presented in this work. Instead, the term refers to the author's own compositional attitudes, education, and aesthetic interests.
ContributorsJandreau, Joshua (Composer) / Rockmaker, Jody D (Thesis advisor) / Rogers, Rodney I (Committee member) / Demars, James R (Committee member) / Arizona State University (Publisher)
Created2014
Description
Phantom Sun is a ten-minute piece in three sections, and is composed for flute, clarinet in b-flat, violin, cello, and percussion. The three-part structure for this work is a representation of the atmospheric phenomenon after which the composition is named. A phantom sun, also called a parhelion or sundog, is a weather-related phenomenon caused by the horizontal refraction of sunlight in the upper atmosphere. This refraction creates the illusion of three suns above the horizon, and is often accompanied by a bright halo called the circumzenithal arc. The halo is caused by light bending at 22° as it passes through hexagonal ice crystals. Consequently, the numbers six and 22 are important figures, and have been encoded into this piece in various ways.
The first section, marked “With concentrated intensity,” is characterized by the juxtaposition of tonal ambiguity and tonal affirmation, as well as the use of polymetric counterpoint (often 7/8 against 4/4 or 7/8 against 3/4). The middle section, marked “Crystalline,” provides contrast in its use of unmetered sections and independent tempos. The refraction of light is represented in this movement by a 22-note row based on a hexachord (B-flat, F, C, G, A, E) introduced in measure 164 of the first section. The third section, marked “With frenetic energy,” begins without pause on an arresting entrance of the drums playing an additive rhythmic pattern. This pattern (5+7+9+1) amounts to 22 eighth-note pulses and informs much of the motivic and structural considerations for the remainder of the piece.
The first section, marked “With concentrated intensity,” is characterized by the juxtaposition of tonal ambiguity and tonal affirmation, as well as the use of polymetric counterpoint (often 7/8 against 4/4 or 7/8 against 3/4). The middle section, marked “Crystalline,” provides contrast in its use of unmetered sections and independent tempos. The refraction of light is represented in this movement by a 22-note row based on a hexachord (B-flat, F, C, G, A, E) introduced in measure 164 of the first section. The third section, marked “With frenetic energy,” begins without pause on an arresting entrance of the drums playing an additive rhythmic pattern. This pattern (5+7+9+1) amounts to 22 eighth-note pulses and informs much of the motivic and structural considerations for the remainder of the piece.
ContributorsMitton, Stephen LeRoy (Author) / DeMars, James (Thesis advisor) / Norton, Kay (Committee member) / Rogers, Rodney (Committee member) / Arizona State University (Publisher)
Created2017
Description
A major concern in the operation of present-day gas turbine engines is the ingestion of hot mainstream gas into rotor-stator disk cavities of the high-pressure turbine stages. Although the engines require high gas temperature at turbine entry for good performance efficiency, the ingested gas shortens the lives of the cavity internals, particularly that of the rotor disks. Steps such as installing seals at the disk rims and injecting purge (secondary) air bled from the compressor discharge into the cavities are implemented to reduce the gas ingestion. Although there are advantages to the above-mentioned steps, the performance of a gas turbine engine is diminished by the purge air bleed-off. This then requires that the cavity sealing function be achieved with as low a purge air supply rate as possible. This, in turn, renders imperative an in-depth understanding of the pressure and velocity fields in the main gas path and within the disk cavities. In this work, experiments were carried out in a model 1.5-stage (stator-rotor-stator) axial air turbine to study the ingestion of main air into the aft, rotor-stator, disk cavity. The cavity featured rotor and stator rim seals with radial clearance and axial overlap and an inner labyrinth seal. First, time-average static pressure distribution was measured in the main gas path upstream and downstream of the rotor as well as in the cavity to ensure that a nominally steady run condition had been achieved. Main gas ingestion was determined by measuring the concentration distribution of tracer gas (CO2) in the cavity. To map the cavity fluid velocity field, particle image velocimetry was employed. Results are reported for two main air flow rates, two rotor speeds, and four purge air flow rates.
ContributorsJunnarkar, Nihal (Author) / Roy, Ramendra P (Thesis advisor) / Mignolet, Marc (Committee member) / Lee, Taewoo (Committee member) / Arizona State University (Publisher)
Created2010
Description
The subject of this thesis is concerned with the amount of cooling air assigned to seal high pressure turbine rim cavities which is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disc life. Excessive purge air, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disc cavity were performed at Arizona State University. The turbine rig has 22 vanes and 28 blades, while the rim cavity is composed of a single-tooth rim lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the rim cavity between the lab seal and the overlap. The data from the experiments were compared to an 360-degree unsteady RANS (URANS) CFD simulations. Although not able to match the time-averaged test data satisfactorily, the CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. To interrogate the validity of URANS simulations in capturing complex rotating flow physics, the scope of this work also included to validating the CFD tool by comparing its predictions against experimental LDV data in a closed rotor-stator cavity. The enclosed cavity has a stationary shroud, a rotating hub, and mass flow does not enter or exit the system. A full 360 degree numerical simulation was performed comparing Fluent LES, with URANS turbulence models. Results from these investigations point to URANS state of art under-predicting closed cavity tangential velocity by 32% to 43%, and open rim cavity effectiveness by 50% compared to test data. The goal of this thesis is to assess the validity of URANS turbulence models in more complex rotating flows, compare accuracy with LES simulations, suggest CFD settings to better simulate turbine stage mainstream/disc cavity interaction with ingestion, and recommend experimentation techniques.
ContributorsKanjiyani, Shezan (Author) / Lee, Taewoo (Thesis advisor) / Mirzamoghadam, Alexander (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2016
Description
A New Home is a multi-movement musical composition written for a chamber orchestra of flute, oboe, clarinet in B-flat, bassoon, horn in F, trumpet in C, trombone, bass trombone, percussion (1), pianoforte, and strings. The duration of the entire piece is approximately fourteen minutes (movement 1: four minutes; mvt. 2: four minutes and thirty seconds; mvt. 3: five minutes and thirty seconds). As an exercise in compositional experimentation, some of the musical techniques explored throughout the piece are harmonic planing or parallelism, ostinati, modality, chromatic dissonance, thematic transformation, mixed meter, and syncopation, as well as issues of orchestral blend, balance, and color.
The first movement, ironically titled “Don’t Panic,” highlights my initial anxieties on experimentation by creating hectic textures. The movement is structured around two main alternating sections of chromatic, chordal dissonance with more modal, melodic syncopation in addition to a developmental section, but a sense of rhythmic groove is prominent throughout. The second movement, “Still Here,” is a darker, more sensitive music as it explores various settings of its main thematic material interspersed with march-like episodes and a related secondary theme. The themes are organized around a diatonic scale that omits one pitch to comprise a six-note scale. The third movement, “Change of State,” recalls the modality and rhythmic liveliness of the first movement, and it bears a thematic relationship to the second movement. Much of the material also revolves around scales and mediant relationships to comprise an opening theme, a groove section, and an ethereal, glassy texture which ends the movement. Essentially, the piece closes with a calmer music in contrast to the brute force that opened the piece.
The first movement, ironically titled “Don’t Panic,” highlights my initial anxieties on experimentation by creating hectic textures. The movement is structured around two main alternating sections of chromatic, chordal dissonance with more modal, melodic syncopation in addition to a developmental section, but a sense of rhythmic groove is prominent throughout. The second movement, “Still Here,” is a darker, more sensitive music as it explores various settings of its main thematic material interspersed with march-like episodes and a related secondary theme. The themes are organized around a diatonic scale that omits one pitch to comprise a six-note scale. The third movement, “Change of State,” recalls the modality and rhythmic liveliness of the first movement, and it bears a thematic relationship to the second movement. Much of the material also revolves around scales and mediant relationships to comprise an opening theme, a groove section, and an ethereal, glassy texture which ends the movement. Essentially, the piece closes with a calmer music in contrast to the brute force that opened the piece.
ContributorsJones, Zachary William (Author) / Rogers, Rodney (Thesis advisor) / Feisst, Sabine (Committee member) / Rockmaker, Jody (Committee member) / Arizona State University (Publisher)
Created2016