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Numerical Prediction of the Pump jet Propulsor tip clearance vortex Cavitation in Uniform Flow

Journal of Shanghai Jiaotong university(Science) 2020年第3期25卷 352-364页

作者： LI Han PAN Guang HUANG Qiaogao SHI Yao Key Laboratory for Unmanned Underwater Vehicle School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072China

Previous studies show that the tip clearance loss limits the improvement of pumpjet propulsor (PJP) performance,and the tip clearance flow field is the most complicated part of PJP *** this work,the non-cavitation and cavitation hydrodynamic performances of PJP with a tip clearance size of 1 mm are obtained by using the detached-eddy simulation (DES).At constant oncoming velocity,cavitation first occurs on the duct and then disappears with the decrease of the advance *** rotor blade cavitation occurs at the low advance ratio and comprises tip clearance cavitation,tip leakage cavitation,and blade sheet *** the rotor region,the typical vortices include tip separation vortex,tip leakage vortex,trailing edge shedding vortex,and blade root horseshoe *** with the pressure distribution,both the Q and λ2 criteria give reliable results of vortex *** cavitation causes an expansion of tip leakage vortex in the circumferential direction and decreases the intensities of tip separation vortex in the whole tip clearance area and tip leakage vortex in the cavitation area,and enhances the strength of tip leakage vortex in the downstream non-cavitation area.

关键词： pump jet propulsor(PJP) hydrodynamics cavitation vortex tip clearance vortex

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Numerical Investigation of Active tip-clearance Control through tip Cooling Injection in an Axial Turbine Cascade

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Journal of Thermal Science 2009年第4期18卷 306-312页

作者： Maosheng Niu Shusheng Zang Institute of Turbomachinery School of Mechanical EngineeringShanghai JiaoTong UniversityShanghai 200240China Professor

This paper presents a numerical investigation of an active tip-clearance control method based on cooling injectionfrom the blade tip surface. It aims to study the influences of air injection on controlling tip clearance flow, withemphasis on the effects of the injection location on secondary flow and the potential thermal benefits from thecooling jet. The results show that injection location plays an important role in the redistribution of secondary flowwithin the cascade passage. Injection located much closer to the pressure-side comer performs better in reducingtip clearance massflow and its associated losses. However, it also intensifies tip passage vortex, due to less restraintderiving from the reduced tip clearance vortex. Lower plenum total pressure is required to inject equivalentamount of cooling air, but the heat transfer condition on the blade tip surface is a bit worse than that with injectionfrom the reattachment region. Thus the optimum location of air injection should be at the tip separation vortex region.

关键词： active tip-clearance control tip cooling injection injection location tip clearance vortex passagevortex secondary flow

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Experimental Investigations of the Three-DimensionalFlow in a Large Deflection Turbine Cascade with tip clearance

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Journal of Thermal Science 1998年第3期7卷 149-164页

作者： M.Govardhan S.S.S.R.K.Sastri V.S.Vishnubhotla ThermalurbomachinesLab DepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartment

Results obtained from an experbontal study of the threedimensional flow survey within and exit of a large defiection linear turbine cascade are presented for a tip clearance levels of 0.08, 1.5, 3.0 percent of chord and compared with the help of boundary layer probes and that within and exit of a blade passage was done with a miniaturised five hole probe. End wall and blade tip surface static pressures were also obtained, in addition to flow visualisation studies. A strong horse-shoe vortex forms in front of the leading edge for zero clearance whereas this vortex does not appear for 3 percent clearance indicating that for large clearance the pressure forces have dominating infiuence than the viscous forces. In addition to normally known clearance vortex, a small tip separation vortex was noticed on the blade tip surface inside the tip gap. Due to the area contraction caused by the tip separation vortex, the fluid movign towards the tip gap from the pressure side is accelerated. Downstream of the vortex, the endwall pressure increases due to flow mixing. Both vortices increase in size and strength along the chord. The miring is incomplete in the aft portion of the blade. The tip gap velocity profiles exhibit wak like characteristics especially at axial positions where the mixing is incomplete. The passage vortex in the present investigations did not diminish with increase in clearance. The discharge coefhcient and the total pressure loss coefficient within the tip gap show similar tendency with lower values near the leading and trailing edge regions.

关键词： turbine cascade tip clearance vortex tip separation vortex horse-shoe vor-tex total pressure loss coefficient discharge coefficient

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The tip Leakage Flow Structure of an Axial Fan with tip clearance

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Journal of Shanghai Jiaotong university(Science) 2003年第1期8卷 75-79页

作者：竺晓程杜朝辉林万来 Turbomachinery Lab. Shanghai Jiaotong Univ. Emerson Electric Corporation 10048 Industrial Blvd

Experiment and numerical simulation technique are used to investigate the tip leakage flow in an axial fan with tip clearance at the design condition. The flow field in the tip region of fan is measured using a PDA (Particle Dynamics Analysis) system. The flow is surveyed across the whole passage at fifteen axial locations (from the 100% axial chord in front of the leading edge to the 100% axial chord behind the trailing edge), mainly focusing on the outer 90% blade span. Both experiment measurement and numerical simulation indicates the leakage flow originated from the tip clearance along the chord rolls up into three dimensional spiral structure to form leakage flow vortex. The interaction of leakage flow and main flow will produce the low velocity zone, and block the flow. The leakage flow almost occupies the most part of flow passage behind the trailing edge.

关键词： particle dynamics analysis (PDA) tip clearance flow tip clearance vortex

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