Endwall Flow/Loss Mechanisms in a Linear Turbine Cascade With Blade Tip Clearance

1989 ◽  
Vol 111 (3) ◽  
pp. 264-275 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Three Dimensional ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Flow Angle ◽  
Pressure Distributions ◽  
Flow Loss ◽  
Blade Tip ◽  
Flow Vectors ◽  
Blade Tip Clearance

This paper discusses the mechanisms of three-dimensional flows and of the associated losses occurring near the tip endwall region of a linear turbine cascade with tip clearance. The clearance gap sizes and the cascade incidences were chosen as the most important variables affecting the mechanisms. Flows close to the endwall and inside the clearance were surveyed in great detail using a micro five-hole pitot tube of 0.6 mm head size. The results gave very detailed information on the mechanisms, such as leakage flow vectors and pressure distributions throughout the clearance. Interaction of leakage flow with the endwall flow and their associated separation lines, effects of gap size and inlet flow angle on loss generation, and skewness of the three-dimensional endwall flows are also discussed.

scholarly journals Numerical Calculation of Flow for Cascade With Tip Clearance

1994 ◽  
Author(s):  
Shimpei Mizuki ◽  
Hoshio Tsujita
Keyword(s):  
Three Dimensional ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Governing Equations ◽  
Tensor Form ◽  
Pressure Surface ◽  
Rear Part ◽  
Blade Tip ◽  
Flow Through ◽  
Blade Tip Geometry

Three-dimensional incompressible turbulent flow within a linear turbine cascade with tip clearance is analyzed numerically. The governing equations involving the standard k-ε model are solved in the physical component tensor form with a boundary-fitted coordinate system. In the analysis, the blade tip geometry is treated accurately in order to predict the flow through the tip clearance in detail when the blades have large thicknesses. Although the number of grids employed in the present study is not enough because of the limitation of computer storage memory, the computed results show good agreements with the experimental results. Moreover, the results clearly exhibit the locus of minimum pressure on the rear part of the pressure surface at the blade tip.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotor Blade ◽  
Tip Clearance ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5%, and 2.5% of the blade span with a flat tip were investigated, respectively, and the uniform and nonuniform inlet temperature profiles were taken as the inlet boundary conditions. A new method for heat transfer coefficient calculation recommended by Maffulli and He has been adopted. By solving the unsteady compressible Reynolds-averaged Navier–Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on the blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. Because it is possible for heat transfer coefficient distributions to be greatly different from heat flux distributions, it becomes of great concern to combine both of them in consideration of hot streak migration. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Effect of Blade Tip Configuration on Tip Clearance Loss of a Centrifugal Impeller

1990 ◽  
Vol 112 (1) ◽  
pp. 14-18 ◽  
Author(s):  
M. Ishida ◽  
H. Ueki ◽  
Y. Senoo
Keyword(s):  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Meridional Plane ◽  
Leakage Flow ◽  
Clearance Ratio ◽  
Contraction Coefficient ◽  
Blade Tip ◽  
Flow Through ◽  
Annular Clearance ◽  
Blade Tip Clearance

According to the theory presented by the authors, the tip clearance loss of an un-shrouded centrifugal impeller mainly consists of two kinds of loss; one is the drag due to the leakage flow through the blade tip clearance and the other is the pressure loss to support the fluid in the thin annular clearance space between the shroud and the blade tip against the pressure gradient in the meridional plane without blades. The former is proportional to the leakage flow or the contraction coefficient of leakage flow. The authors have conducted performance tests using an impeller with 16 backward-leaning blades in three configurations of the blade tip: round edge, sharp square edge, and edge with an end-plate. The experimental tip clearance effects can be predicted by the theory assuming reasonable contraction coefficients. They are 0.91, 0.73, and 0.53 for the respective tip configurations. The impeller efficiency is improved by about 1.5 point by reducing the contraction coefficient from 0.91 to 0.53, providing that the tip clearance ratio at the exit of impeller is 0.1. More improvement is expected for an impeller with highly loaded blades where the leakage loss shares the major part of the tip clearance loss.

J051052 tudy on the Tip Leakage Flow in Linear Compressor Cascade : Effects of Blade Tip Clearance and Tip Velocity)

2011 ◽  
Vol 2011 (0) ◽  
pp. _J051052-1-_J051052-4
Author(s):  
Kazunari MATSUDA ◽  
Kenichi FUNAZAKI ◽  
Hideo TANIGUCHI ◽  
Hiromasa KATO ◽  
Masafumi KUMAGAI ◽  
...  
Keyword(s):  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip ◽  
Cascade Effects ◽  
Linear Compressor Cascade ◽  
Tip Velocity ◽  
Blade Tip Clearance

scholarly journals Numerical Investigations on the Blade Tip Clearance Excitation Forces in an Unshrouded Turbine

2020 ◽  
Vol 10 (4) ◽  
pp. 1532 ◽  
Author(s):  
Yang Pan ◽  
Qi Yuan ◽  
Gongge Huang ◽  
Jiawei Gu ◽  
Pu Li ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Geometrical Parameters ◽  
Deformation Method ◽  
Flow Angle ◽  
Rotordynamic Coefficients ◽  
Blade Tip ◽  
Positive Direct

The purpose of this study was to investigate the characteristics of the blade tip excitation forces represented as the rotordynamic coefficients (stiffness and damping coefficients) in an unshrouded turbine using the three-dimensional computational fluid dynamic (CFD) numerical method. The blade geometrical parameters were based on a SNECMA transonic experimental rig. The simulations were performed by solving the compressible Reynolds-averaged Navier–Stokes (RANS) equations. The multi-frequency elliptical whirling orbit model and an improved mesh deformation method based on the transient analysis were utilized. The effects of operating conditions on the rotordynamic coefficients and the unsteady flow were also found. The results show that the positive direct stiffness, which confirmed the direct force contribution in the tip excitation forces and the cross-coupling stiffness, were dependent on the whirling frequencies. Damping effects were shown to be negligible. The rotational speed, inlet flow angle, eccentric ratio (ER), and mean tip clearance had impacts on the stiffness, and some effects of these variables on the rotordynamic coefficients were found to be frequency dependent. Additionally, increasing the rotor eccentricity and the mean tip clearance led to the nonuniformity of the circumferential pressure distributions.

Experimental and Computational Investigation of the Tip Clearance Flow for an Axial Ventilation Fan

2003 ◽  
Author(s):  
Xiaocheng Zhu ◽  
Wanlai Lin ◽  
Zhaohui Du
Keyword(s):  
Numerical Simulation ◽  
Experimental Measurement ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip ◽  
Ventilation Fan

The tip leakage flow in an axial ventilation fan with various tip clearances is investigated by experimental measurement and numerical simulation. The characteristic of a ventilation fan is an extreme low-pressure difference, a large tip clearance with a low rotating speed. A three dimensional PDA (Particle Dynamics Analysis) system is used for the measurement of the velocity field in the tip clearance region. The flow field is surveyed across the whole passage at fifteen axial locations (from 100% axial chord in front of the leading edge to 100% axial chord behind the trailing edge), mainly focusing on areas close to the blade tip (from 90% of the blade span to the casing wall). Both experimental measurement and numerical simulation indicate that the leakage flow originating from the tip clearance along the chord rolls up into a three-dimensional spiral structure to form a leakage flow vortex. A low axial velocity zone shows up in the tip region, which leads to blockage of the main flow. There are under-turning zones near and in the blade tip region, and an overturning zone in a lower span region with a critical span-wise position of about 94%. A reverse flow appears at the suction side near the trailing edge. As the tip clearance increases, the tip leakage flow and the reverse flow become stronger and fully developed. In addition, the position of the first appearance of the tip leakage vortex moves further downstream in a direction parallel to the mid chord line.

Numerical analysis of the aerodynamic performance and excitation forces in a transonic turbine cascade with flat-tip and squealer-tip blades

2020 ◽  
Vol 234 (22) ◽  
pp. 4377-4389
Author(s):  
Yang Pan ◽  
Qi Yuan ◽  
Gongge Huang ◽  
Guangyu Zhu ◽  
Pu Li
Keyword(s):  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Turbine Efficiency ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Transonic Turbine ◽  
Excitation Force

The purpose of this paper is to numerically investigate the effect of blade tip clearance and its structure on the turbine aerodynamic performance and excitation force on blades in a transonic turbine cascade. Hence, circular cascades with flat-tip and squealer-tip blades and eight different tip clearances based on the SNECMA transonic turbine were established and the rotational effect was taking into consideration. The simulations were performed by solving the RANS equations and the SST turbulence model was used. The results show that tip clearance and tip structure have a significant influence on the turbine efficiency and excitation forces. Smaller tip clearance and squealer tip structure can reduce the tip leakage flow and leads to higher turbine efficiency. The tangential blade force varies nonlinearly with tip clearance since the leakage flow significantly changes the static pressure distributions on blade surfaces. Further, the excitation force factor was also calculated and illustrated.

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2013 ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Stokes Equations ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5% and 2.5% of the blade span with a flat tip were investigated respectively, and the uniform and non-uniform inlet temperature profiles were taken as the inlet boundary conditions. By solving the unsteady compressible Reynolds-averaged Navier-Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Sign in / Sign up

Export Citation Format

Share Document