자료유형  

 학위논문

Control Number  

0017164313

International Standard Book Number  

9798342140232

Dewey Decimal Classification Number  

330

Main Entry-Personal Name  

Shishodia, Adwiteey Raj.

Publication, Distribution, etc. (Imprint  

[S.l.] : Purdue University., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

109 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-04, Section: B.

General Note  

Advisor: Shih, Tom I.P.

Dissertation Note  

Thesis (Ph.D.)--Purdue University, 2024.

Summary, Etc.  

요약Gas turbines are widely used to provide propulsion, electrical-power, and mechanical power. Though tremendous advances have been made since Frank Whittle's patent of a turbojet in 1930 and Hans von Ohain's patent of the first operational turbojet in 1936, industry still has aggressive goals on improvements in efficiency and service life. One area where further advances are needed is better control of the flow across the gap between the blade tip and the shroud, referred to as tip-leakage flow (TLF). This is because TLF accounts for up to one-third of the aerodynamic losses in a turbine stage.In this study, hybrid LES-RANS based on IDDES and steady RANS based on the SST turbulence model were used to study the compressible flow in a 1.5-stage turbine with geometry and operating conditions that are relevant to power-generation gas turbines. The focus is on the flow in the tip-gap region that account for the flow features created by the upstream stator vanes, stator-rotor interactions, and downstream stator vanes. Results obtained reveal the flow structures about the tip-gap region and the flow mechanisms that create them. Results obtained also show where steady RANS with mixing plane could predict correctly when compared with results from IDDES that resolve the unsteadiness of the turbulence and the motion of the rotor blades passing the stator vanes. Turbulent statistics from the IDDES were generated to guide the development of better RANS models. Results were also obtained by using RANS to examine the effects of blade loading, where mass flow rate through the 1.5 stage turbine was varied with the rotor's rotational speed fixed at 3,600 RPM - the speed at which power-generation gas turbines operate in the U.S.Key findings are as follows: In the first-stage stator, horseshoe, passage, and corner vortices were found to be confined within 10 to 15% span from the hub and shroud, and both steady RANS and IDDES generated similar results. Steady RANS and IDDES, however, differed considerably in how they predicted the wake downstream of the vane's trailing edge. This coupled with the use of mixing plane, steady RANS was unable to account for effects of stator-rotor interactions and their effects on the tip-leakage flow. In the rotor, steady RANS predicted passage vortices that extended up to 50% span from the hub and 25% span from the shroud. The flow through the tip gap was found to induce a separation bubble on the blade tip and one large and two small vortical structures on the suction side of the blade and a vortical structure next to the shroud. These structures were found to grow along the axial chord of the blade. Steady RANS also predicted the large tip leakage vortex that contained the fluid from the tip-leakage flow to breakdown. IDDES did not predict the vortex breakdown because all of the coherent vortical structures identified including the separated region on the blade tip were unsteady and constantly shedding. As a result, IDDES predicted much smaller mean passage vortices - albeit the instantaneous structures were nearly as large as those predicted by steady RANS.

Subject Added Entry-Topical Term  

Aircraft.

Subject Added Entry-Topical Term  

Heat transfer.

Subject Added Entry-Topical Term  

Turbines.

Subject Added Entry-Topical Term  

Viscosity.

Subject Added Entry-Topical Term  

Scale models.

Subject Added Entry-Topical Term  

Turbulence models.

Subject Added Entry-Topical Term  

Vortices.

Subject Added Entry-Topical Term  

Fluid dynamics.

Subject Added Entry-Topical Term  

Pressure distribution.

Subject Added Entry-Topical Term  

Energy.

Subject Added Entry-Topical Term  

Gas turbines.

Subject Added Entry-Topical Term  

Reynolds number.

Subject Added Entry-Topical Term  

Geometry.

Subject Added Entry-Topical Term  

Hydraulics.

Subject Added Entry-Topical Term  

Shear stress.

Subject Added Entry-Topical Term  

Fluid mechanics.

Subject Added Entry-Topical Term  

Hydraulic engineering.

Subject Added Entry-Topical Term  

Thermodynamics.

Added Entry-Corporate Name  

Purdue University.

Host Item Entry  

Dissertations Abstracts International. 86-04B.

Electronic Location and Access  

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Control Number  

joongbu:657641