ACTA AERONAUTICAET ASTRONAUTICA SINICA >
Influence of tip clearance on flow characteristics of a supersonic expander
Received date: 2014-11-27
Revised date: 2015-10-12
Online published: 2015-10-21
Supported by
Specialized Research Fund for the Doctoral Program of Higher Education of China(20132125120006);The Fundamental Research Funds for the Central Universities(3132014319);Supported by Program for Liaoning Innovative Research Team in University(LT2015004)
A clearance exists between strake wall and casing, which will certainly influence internal flow field and overall performance of a supersonic expander. To obtain the flow details of tip clearance flow in a supersonic expander, the three-dimensional Reynolds-averaged Navier-Stokes equations and the k-ε turbulent model are adopted in this paper to simulate numerically the tip clearance flow of a supersonic expander. It has been found that oblique shock wave at the outlet of the expansion passage leads to the fact that static pressure of the suction surface is higher than the pressure surface, parts of the leakage fluid near the trailing edge passes the clearance and reflows to the pressure surface. Because of the tip clearance, static pressures of the suction surface at the location of inlet and near the lower end wall increase, while the pressure at the pressure surface near the leading edge decreases. Compared with the same location of the strake wall, increasing the tip clearance height by 1% throat height, load coefficient of the strake wall of supersonic expander drops by as much as 2.6%. The loss of end wall and oblique shock wave reduces, but the tip leakage loss is produced, increasing the overall flow loss of the three-dimensional flow passage, and the efficiency of the supersonic expander drops, which decreases by up to 8.8% in this paper. The horseshoe vortex, the leakage vortex, and the interaction between them constitute the main vortex system of the tip area. The airflow near the leading edge through the clearance flow to the suction surface and the leakage fluid around the trailing edge across the gap back to the pressure surface is the main form of movement within the clearance.
Key words： supersonic expander; strake wall; tip clearance; expansion waves; leakage vortex
HUANG Zhenyu , ZHONG Jingjun , YANG Ling , HAN Ji'ang . Influence of tip clearance on flow characteristics of a supersonic expander[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2016 , 37(2) : 555 -567 . DOI: 10.7527/S1000-6893.2015.0269
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