Department News
Prediction and Control of Tip-Leakage Flow in a Turbomachinery Cascade
Seminar Date
2005-09-23
Author
임아주
Date
2005-09-22
Views
1877
1. 제 목 : Prediction and Control of Tip-Leakage Flow in a Turbomachinery Cascade
2. 연 사 : Dr. Donghyun You
Turbulence Simulations
Stanford Center for Turbulence Research and
Center for Integrated University
3. 일 시 : 2005년 9월 23일(금) 오후 4시
4. 장 소 : 301동 1409-1호 세미나실
5. 내 용 : In liquid handling systems like pumps and ducted propulsors, low pressure events in the vicinity and downstream of the rotor tip gap can induce tip-leakage cavitation which leads to noise, vibration, performance loss, and erosions of blade and casing wall.
In order to analyze the dynamics of the tip-clearance flow and determine the underlying mechanism for the low pressure events, a large-eddy simulation (LES) solver which combines an immersed-boundary method with a generalized curvilinear structured grid has been employed.
Systematic and detailed analysis of the mean flow field and turbulence statistics shows that the tip-leakage jet and tip-leakage vortex produce significant mean velocity gradients, leading to the production of vorticity and turbulent kinetic energy. Analyses of the energy spectra and space-time correlations of the velocity fluctuations suggest that the tip-leakage vortex is subject to pitchwise wandering motion.
The largest pressure drop and most intense pressure fluctuations due to the formation of the tip-leakage vortex are found at the location where the strongest portion of the tip-leakage vortex is found.
The present analysis indicates that the mechanism for the generation of the vorticity and turbulent kinetic energy is mostly unchanged by the tip-gap size variation.
However, larger tip-gap sizes are found to be more inductive to tip-leakage cavitation judged by the levels of negative mean pressure and pressure fluctuations. To suppress the tip-leakage vortex and the associated detrimental effects, the use of a grooved casing wall has been explored.
Compared to the uncontrolled tip-leakage vortex, the controlled one shows reduced vorticity magnitude and pressure fluctuations.
This is achieved without compromising the compressor performance.
6. 문 의 : 기계항공공학부 최 해 천 교수 (☏ 880-8361)
2. 연 사 : Dr. Donghyun You
Turbulence Simulations
Stanford Center for Turbulence Research and
Center for Integrated University
3. 일 시 : 2005년 9월 23일(금) 오후 4시
4. 장 소 : 301동 1409-1호 세미나실
5. 내 용 : In liquid handling systems like pumps and ducted propulsors, low pressure events in the vicinity and downstream of the rotor tip gap can induce tip-leakage cavitation which leads to noise, vibration, performance loss, and erosions of blade and casing wall.
In order to analyze the dynamics of the tip-clearance flow and determine the underlying mechanism for the low pressure events, a large-eddy simulation (LES) solver which combines an immersed-boundary method with a generalized curvilinear structured grid has been employed.
Systematic and detailed analysis of the mean flow field and turbulence statistics shows that the tip-leakage jet and tip-leakage vortex produce significant mean velocity gradients, leading to the production of vorticity and turbulent kinetic energy. Analyses of the energy spectra and space-time correlations of the velocity fluctuations suggest that the tip-leakage vortex is subject to pitchwise wandering motion.
The largest pressure drop and most intense pressure fluctuations due to the formation of the tip-leakage vortex are found at the location where the strongest portion of the tip-leakage vortex is found.
The present analysis indicates that the mechanism for the generation of the vorticity and turbulent kinetic energy is mostly unchanged by the tip-gap size variation.
However, larger tip-gap sizes are found to be more inductive to tip-leakage cavitation judged by the levels of negative mean pressure and pressure fluctuations. To suppress the tip-leakage vortex and the associated detrimental effects, the use of a grooved casing wall has been explored.
Compared to the uncontrolled tip-leakage vortex, the controlled one shows reduced vorticity magnitude and pressure fluctuations.
This is achieved without compromising the compressor performance.
6. 문 의 : 기계항공공학부 최 해 천 교수 (☏ 880-8361)
