An experimenrtal study of a strong swirling flow structure

• Main Authors: Ching-Jun Lee, 李青峻
• Other Authors: Horn-Jiunn Sheen
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/36460203828740419837

碩士 === 國立臺灣大學 === 應用力學研究所 === 87 === This study experimentally investigates the flow structure of the combustion chamber of a gas turbine with an axial-type swirl generator. The experiment uses laser Doppler anemometer (LDA) to measure the velocity of the flow. Flow visualization technique with seeding particles and a CCD camera was applied to investigate the flow patterns in various flow conditions. First, we use LDA to measure the velocity profiles at the jet exit in order to obtain the swirl number. The swirl number is found to be varied with the Reynolds number when Re is below 2500. When the Reynolds number is over 2500, the swirl number becomes a constant. The second part of this study, we investigate the different flow phenomena of the annular swirling jet flow. Various flow patterns are observed based on the Reynolds number and the swirl number. In the pre-penetration regime, an inverse-triangle zone behind the center body is found and a long recirculation zone can be observed. Flow branch, due to that the centrifugal force is larger than the radial pressure gradient, make the cross-section of the flow to stretch in the radial direction. In the transition regime, the horizontal cross-section flow pattern can be divided into two different types, S type and  type. Each type can transform to another one and the multiply of their rotation frequencies is one. The swirling jet flow expansion angle will vary with the Reynolds number. By adding a nozzle at the jet exit can reduce the expansion angle and has a pronounced effect in flame combustion, mixing rate and flow stability. With a confined boundary, the annular swirling jet induces a corner recirculation zone which induces the precession of the swirling jet flow.