Experimental And Numerical Investigations Of Tip Leakage Flow In Turbine Cascade

A gas turbine has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between. Chemical energy is transformed into thermal energy of the gas stream in the combustor. And the energy given up to the turbine is transformed into mechanical energy and electrical energy. Gas turbine is widely used in all fields of basic economic, especially in the Industrial transportation fields like airline, ships, power generation, petrochemical industry, natural gas transportation and railway transportation in developed countries.This paper use Dalian Maritime University of subsonic plane blade of a belt around the test bench with leaves of the blade tip clearance flow of the test and measurement, mainly in plane blade trailing edge different exit section export total pressure, flow Angle and the export of velocity distribution test and measurement. At the same time, through the44static pressure hole in blade surface, we got the distribution of static pressure on blade surface at the middle section and close to the top of the section. Finally using CFX, combined with three-d numerical calculation method, reveals the physical quantities and flow details like distribution of the clearance internal flow field, the speed at import and export of clearance, and clearance flow which test is difficult to measure.Through the analysis of the test results of the aerodynamic performance of the turbine cascade in conditions that it has different tip clearance sizes with or without shroud, when it exists the tip clearance, we find that the working medium flows from the pressure side to the suction side with the function of different pressure between the pressure side and the suction side, then it forms into clearance vortex, with effect of the negative pressure gradient in the tangential wise. With the tip clearance vortex developing gradually downstream, the influence gradatim expands and the strength reduces. And with the interaction between clearance vortex and passage vortex interaction, the loss is increasing. Along with the increase of the tip clearance height, the working medium across the tip clearance increases rapidly, that causes the clearance vortex impact range is increased substantially in the pitch and radial wise. And strength is greatly enhanced, it causes that top passage vortex is forced to move towards the middle span. with the increase of the tip clearance height, the clearance flow loss also performs linear growth trend. Because the role of shroud, the high loss area which caused by tip leakage vortex is disappearance, and a high loss area appears near the top of the shroud along the pitch-wise. With the increase of the height of the gap, the tip leakage increases. When at the gap height of0.5%blade height,1%blade height, the increase of leakage is slow, along with the increase of the gap height, the leakage of1.5%blade height increased suddenly, the loss is much higher than0.5%and1%blade height.With and without shroud, when the angle of attack I=-10°, the flow loss is minimum. With the increase of the angle of attack, the flow loss will increase, but the magnitude of the increasing is different, the case without shroud is more acute.