Matching Items (33)
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- All Subjects: Mechanical Engineering
- All Subjects: Mechanics
- Creators: Chen, Kangping
Description
Modern gas turbines operate at high mainstream gas temperatures and pressures, which requires high durability materials. A method of preventing these hot gases from leaking into the turbine cavities is essential for improved reliability and cost reduction. Utilizing bleed-off air from the compressor to cool internal components has been a common solution, but at the cost of decreasing turbine performance. The present work thoroughly describes the complex flow field between the mainstream gas and a single rotor-stator disk cavity, and mechanisms of mainstream gas ingestion. A combined approach of experimental measurement and numerical simulation are performed on the flow in a single-stage model gas turbine. Mainstream gas ingestion into the cavity is further reduced by utilizing two axially overlapping seal rings, one on the rotor disk and the other on the stator wall. Secondary purge air is injected into the rotor-stator cavity pre-swirled through the stator radially inboard of the two seal rings. Flow field predictions from the simulations are compared against experimental measurements of static pressure, velocity, and tracer gas concentration acquired in a nearly identical model configuration. Operational conditions were performed with a main airflow Reynolds number of 7.86e4 and a rotor disk speed of 3000rpm. Additionally the rotational Reynolds number was 8.74e5 with a purge air nondimensional flow rate cw=4806. The simulation models a 1/14 rotationally periodic sector of the turbine rig, consisting of four rotor blades and four stator vanes. Gambit was used to generate the three-dimensional unstructured grids ranging from 10 to 20 million cells. Effects of turbulence were modeled using the single-equation Spalart-Allmaras as well as the realizable k-epsilon models. Computations were performed using FLUENT for both a simplified steady-state and subsequent time-dependent formulation. Simulation results show larger scale structures across the entire sector angle inside the cavity and certain unsteady mainstream ingestion mechanisms are realized from the tracer gas. Simulated velocity distributions were scrutinized against Particle Image Velocimetry plots in the rotor-stator cavity and are in reasonable agreement with all of the measurements.
ContributorsDunn, Dennis Martin (Author) / Squires, Kyle D (Thesis advisor) / Roy, Ramendra P (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2010
Description
In this dissertation, two types of passive air freshener products from Henkel, the wick-based air freshener and gel-based air freshener, are studied for their wicking mechanisms and evaporation performances.The fibrous pad of the wick-based air freshener is a porous medium that absorbs fragrance by capillary force and releases the fragrance into the ambient air. To investigate the wicking process, a two-dimensional multiphase flow numerical model using COMSOL Multiphysics is built. Saturation and liquid pressure inside the pad are solved. Comparison between the simulation results and experiments shows that evaporation occurs simultaneously with the wicking process. The evaporation performance on the surface of the wicking pad is analyzed based on the kinetic theory, from which the mass flow rate of molecules passing the interface of each pore of the porous medium is obtained. A 3D model coupling the evaporation model and dynamic wicking on the evaporation pad is built to simulate the entire performance of the air freshener to the environment for a long period of time. Diffusion and natural convection effects are included in the simulation. The simulation results match well with the experiments for both the air fresheners placed in a chamber and in the absent of a chamber, the latter of which is subject to indoor airflow.
The gel-based air freshener can be constructed as a porous medium in which the solid network of particles spans the volume of the fragrance liquid. To predict the evaporation performance of the gel, two approaches are tested for gel samples in hemispheric shape. The first approach is the sessile drop model commonly used for the drying process of a pure liquid droplet. It can be used to estimate the weight loss rate and time duration of the evaporation. Another approach is to simulate the concentration profile outside the gel and estimate the evaporation rate from the surface of the gel using the kinetic theory. The evaporation area is updated based on the change of pore size. A 3D simulation using the same analysis is further applied to the cylindrical gel sample. The simulation results match the experimental data well.
ContributorsYuan, Jing (Author) / Chen, Kangping (Thesis advisor) / Herrmann, Marcus (Committee member) / Huang, Huei-Ping (Committee member) / Wang, Liping (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2021
Description
This research aims to develop a single-phase immersion cooling system for CPU (Central Processing Unit) processors. To achieve this, a heat pipe with a
dielectric liquid is designed to be used to cool the CPU, relying only on natural
convection. A Tesla valve phenomenon is used to achieve the one-directional,
recirculating system. A comparative study was conducted between two different
single-phase dielectric fluids Mineral Oil and FC 3283 (Fluorocarbon), utilizing
natural convection and Boussinesq correlations. ANSYS Fluent was used to conduct
CFD (Computational Fluid Dynamics) analysis, demonstrating natural convection
and recirculating flow in the heating direction. A comparison was made between the
traditional cooling method of air and the developed immersion cooling system, with
the results indicating that the system is capable of reducing the operating
temperature of the CPU by 40 to 50 degrees Celsius, depending on the power
consumption. The results of the experiment conducted showed that a processor cooled
by Mineral oil would operate at 56 degrees Celsius, while a processor cooled by FC
3283 would operate at 47 degrees Celsius. By comparison, a processor cooled by the
traditional air-cooled system would operate between 80 and 100 degrees Celsius.
These results demonstrate that the Mineral oil and FC 3283 cooling systems are
significantly more efficient than the traditional air-cooled system. This could prove to
be a valuable asset in the development of more efficient cooling systems. Further
research is necessary to evaluate the longevity, cost-effectiveness, and benefits of
these systems in comparison to traditional air cooling
ContributorsGajjar, Kathan Malaybhai (Author) / Huang, Huei Ping (Thesis advisor) / Chen, Kangping (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2023