Tip Clearance Effects in a Turbine Rotor: Part I—Pressure Field and Loss

2000 ◽  
Vol 123 (2) ◽  
pp. 296-304 ◽  
Author(s):  
Xinwen Xiao ◽  
Andrew A. McCarter ◽  
Budugur Lakshminarayana
Keyword(s):  
Total Pressure ◽  
Pressure Field ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Laser Doppler Velocimeter ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Passage Vortex

This paper presents an experimental investigation of the effects of the tip clearance flow in an axial turbine rotor. The effects investigated include the distribution and the development of the pressure, the loss, the velocity, and the turbulence fields. These flow fields were measured using the techniques of static pressure taps, rapid response pressure probes, rotating five-hole probes, and Laser Doppler Velocimeter. Part I of this paper covers the loss development through the passage, and the pressure distribution within the passage, on the blade surfaces, on the blade tip, and on the casing wall. Regions with both the lowest pressure and the highest loss indicate the inception and the trace of the tip leakage vortex. The suction effect of the vortex slightly increases the blade loading near the tip clearance region. The relative motion between the turbine blades and the casing wall results in a complicated pressure field in the tip region. The fluid near the casing wall experiences a considerable pressure difference across the tip. The highest total pressure drop and the highest total pressure loss were both observed in the region of the tip leakage vortex, where the loss is nearly twice as high as that near the passage vortex region. However, the passage vortex produces more losses than the tip leakage vortex in total. The development of the loss in turbine rotor is similar to that observed in cascades. Part II of this paper covers the velocity and the turbulence fields.

Tip Clearance Effects in a Turbine Rotor: Part I — Pressure Field and Loss

2000 ◽  
Author(s):  
Xinwen Xiao ◽  
Andrew A. McCarter ◽  
Budugur Lakshminarayana
Keyword(s):  
Total Pressure ◽  
Pressure Field ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Laser Doppler Velocimeter ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Passage Vortex

This paper presents an experimental investigation of the effects of the tip clearance flow in an axial turbine rotor. The effects investigated include the distribution and the development of the pressure, the loss, the velocity, and the turbulence fields. These flow fields were measured using the techniques of static pressure taps, rapid response pressure probes, rotating five-hole probes, and Laser Doppler Velocimeter. Part I of this paper covers the loss development through the passage, and the pressure distribution within the passage, on the blade surfaces, on the blade tip, and on the casing wall. Regions with both the lowest pressure and the highest loss indicate the inception and the trace of the tip leakage vortex. The suction effect of the vortex slightly increases the blade loading near the tip clearance region. The relative motion between the turbine blades and the casing wall results in a complicated pressure field in the tip region. The fluid near the casing wall experiences a considerable pressure difference across the tip. The highest total pressure drop and the highest total pressure loss were both observed in the region of the tip leakage vortex, where the loss is nearly twice as high as that near the passage vortex region. However, the passage vortex produces more losses than the tip leakage vortex in total. The development of the loss in turbine rotor is similar to that observed in cascades. Part II of this paper covers the velocity and the turbulence fields.

Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

2017 ◽  
Vol 231 (7) ◽  
pp. 676-685 ◽  
Author(s):  
Shaowen Chen ◽  
Zhihua Zhou ◽  
Qinghe Meng ◽  
Songtao Wang ◽  
Xun Zhou
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Static Pressure ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Side Gap

The effects of a novel winglet-cavity tip on the flow field and aerodynamic performance of a turbine blade with tip clearance have been investigated in a low-speed wind tunnel. A calibrated five-hole probe is used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization is used to show the endwall flow field structure. The distribution of endwall static pressure is measured particularly by using the special moveable endwall. The downstream results show that, compared with the flat tip and cavity tip, the winglet-cavity tip reduces aerodynamic loss in the region of tip leakage vortex and passage vortex effectively and gives a 8.5% reduction of total pressure losses at a tip clearance of τ/ H = 1.0%. Meanwhile, a more uniform flow angle is obtained with the winglet-cavity tip. Thus, the winglet-cavity tip provides better aerodynamic performance. It was found that more endwall flow enters the cavity from the front of suction side gap, combines with the flow entering the tip from the pressure side, and then separates upon the cavity. This reduces the loss of passage vortex. The endwall static pressure indicates that the winglet-cavity tip reduces the driving pressure difference and weakens the tip leakage flow. With the tip clearance increasing, the leakage flow is significantly enhanced. This strengthens the interaction between the tip leakage vortex and the passage vortex. With respect to the flat tip and cavity tip, the winglet-cavity tip obtains the lowest total pressure loss at all tested tip clearances.

Numerical Simulation of Tip Clearance Control in Axial Turbine Rotor: Part 2—Passive Control of Five Different Tip Platforms

2008 ◽  
Author(s):  
Wei Li ◽  
Wei-Yang Qiao ◽  
Kai-Fu Xu ◽  
Hua-Ling Luo
Keyword(s):  
Flow Control ◽  
Passive Control ◽  
Suction Side ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow

The tip leakage flow has significant effects on turbine in loss production, aerodynamic efficiency, etc. Then it’s important to minimize these effects for a better performance by adopting corresponding flow control. The active turbine tip clearance flow control with injection from the tip platform is given in Part-1 of this paper. This paper is Part-2 of the two-part papers focusing on the effect of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip (Partial SS Squealer), a double squealer tip (Double Side Squealer), a pressure side tip shelf with inclined squealer tip on a double squealer tip (Improved PS Squealer), a tip platform extension edge in pressure side (PS Extension) and in suction side (SS Extension) respectively. Combined with the turbine rotor and the numerical method mentioned in Part 1, the effects of passive turbine tip clearance flow controls on the tip clearance flow were sequentially simulated. The detailed tip clearance flow fields with different squealer rims were described with the streamline and the velocity vector in various planes parallel to the tip platform or normal to the tip leakage vortex core. Accordingly, the mechanisms of five passive controls were put in evidence; the effects of the passive controls on the turbine efficiency and the tip clearance flow field were highlighted. The results show that the secondary flow loss near the outer casing including the tip leakage flow and the casing boundary layer can be reduced in all the five passive control methods. Comparing the active control with the passive control, the effect brought by the active injection control on the tip leakage flow is evident. The turbine rotor efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine rotor efficiency, and it increased by 0.215%.

Inlet Condition Effects on the Tip Clearance Flow With Zonal Detached Eddy Simulation

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
William Riéra ◽  
Lionel Castillon ◽  
Julien Marty ◽  
Francis Leboeuf
Keyword(s):  
Guide Vane ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Inlet Guide Vane ◽  
Detached Eddy Simulation ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Inlet Condition ◽  
Clearance Flow

In the present study, the influence of the inlet condition on the tip clearance flow of an axial compressor is investigated. Two different zonal detached eddy simulations (ZDES) computations are carried out and compared to Reynolds-averaged Navier–Stokes (RANS) and unsteady RANS (URANS) computations as well as to experimental data. A rotating distortion map of the flow cartography is set as inlet condition for the first ZDES computation. An azimuthally averaged inlet condition is used for the second one and uncouples the rotor tip-leakage vortex flutter phenomenon, which stems from the arrival of the inlet guide vane wake from the behavior inherent to the rotor tip-leakage vortex. In the studied configuration, the inlet guide vane tip vortex reveals to lower the effects from double leakage on the rotor. The topology of the rotor tip-leakage vortex is described, and its development is analyzed.

Numerical Investigation of Relation Between Unsteady Behavior of Tip Leakage Vortex and Rotating Disturbance in a Transonic Axial Compressor Rotor

2008 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
H. Sasaki
Keyword(s):  
Vortex Breakdown ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Rotating Instability

The purpose of this study is to have a better understanding of the unsteady behavior of tip clearance flow at near-stall condition from a multi-passage simulation and to clarify the relation between such unsteadiness and rotating disturbance. This study is motivated by the following concern. A single passage simulation has revealed the occurrence of the tip leakage vortex breakdown at near-stall condition in a transonic axial compressor rotor, leading to the unsteadiness of the tip clearance flow field in the rotor passage. These unsteady flow phenomena were similar to those in the rotating instability, which is classified in one of the rotating disturbances. In other words it is possible that the tip leakage vortex breakdown produces a rotating disturbance such as the rotating instability. Three-dimensional unsteady RANS calculation was conducted to simulate the rotating disturbance in a transonic axial compressor rotor (NASA Rotor 37). The four-passage simulation was performed so as to capture a short length scale disturbance like the rotating instability and the spike-type stall inception. The simulation demonstrated that the unsteadiness of tip leakage vortex, which was derived from the vortex breakdown at near-stall condition, invoked the rotating disturbance in the rotor, which is similar to the rotating instability.

Vortex Dynamics and Mechanisms for Viscous Losses in the Tip-Clearance Flow

2005 ◽  
Author(s):  
Donghyun You ◽  
Meng Wang ◽  
Parviz Moin ◽  
Rajat Mittal
Keyword(s):  
Tip Clearance ◽  
Wall Region ◽  
Mean Flow ◽  
Mean Velocity ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Viscous Losses ◽  
Clearance Flow ◽  
End Wall

The tip-clearance flow in axial turbomachines is studied using large-eddy simulation with particular emphasis on understanding the underlying mechanisms for viscous losses in the end-wall region and the unsteady characteristics of the tip-leakage vortical structures. Systematic and detailed analysis of the mean flow field and turbulence statistics has been made in a linear cascade with a moving end-wall. The tip-leakage jet and tip-leakage vortex are found to produce significant mean velocity gradients, leading to the production of vorticity and turbulent kinetic energy. These are the major causes for viscous losses in the cascade end-wall region. An analysis of the energy spectra and space-time correlations of the velocity fluctuations suggests that the tip-leakage vortex is subject to a pitchwise low frequency wandering motion.

Tip Clearance Effects on Unsteady Behavior of the Tip Leakage Vortex and Stator/Rotor Interaction Tonal Noise

2012 ◽  
Author(s):  
Lei Zhao ◽  
Wei-Yang Qiao ◽  
Zhong-Qiang Mu ◽  
Ping-Ping Chen
Keyword(s):  
Noise Level ◽  
Tip Clearance ◽  
Tonal Noise ◽  
Blade Loading ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow ◽  
Matching Strategy ◽  
Unsteady Behavior

In turbomachinery the tip leakage vortex is an obvious periodic phenomenon associated with rotor blade, its interaction with stator wake will affect the tonal noise level and aerodynamic performance. This study assesses the effects of tip leakage vortex on the stator/rotor interaction tonal noise and its unsteady behavior by 3D unsteady numerical simulations and the Triple-Plane Pressure matching strategy. The fluctuation of blade loading distribution and the interaction of wake negative jet with tip clearance flow change the structure and position of tip leakage vortex and scrapping vortex periodically. From the time-average results, the incoming wakes reduced the strength of vortices. The result also shows that the tonal noise level of turbine stage is decreased with the enlargement of tip clearance.

Influence of tip clearance distribution on blade vibration of vaneless radial turbine

2021 ◽  
pp. 095440702110281
Author(s):  
Lei Pan ◽  
Mingyang Yang ◽  
Shouta Murae ◽  
Wataru Sato ◽  
Naoto Shimohara ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Vibration Response ◽  
Tip Clearance ◽  
Field Analysis ◽  
Pressure Amplitude ◽  
Suction Surface ◽  
Blade Vibration ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Radial Turbine

As vehicle turbochargers are developed toward higher performance and lower turbo lag, high cycle fatigue (HCF) of radial turbine blades is becoming increasingly common which greatly threatens the reliability of turbochargers. Tip leakage vortex is one of potential sources of blade excitation and it’s profoundly influenced by blade tip clearance. This paper studies the influence of tip clearance distribution on blade excitation of a vaneless radial turbine via experimentally validated one-way fluid-structure interaction (FSI) numerical method. The results suggest that blade vibration response is significantly influenced by tip clearance distribution in the meridional direction. Generalized energy method is proposed to determine the key factors for blade excitation. The results manifest that complex distributions of harmonic pressure amplitude on the blade dominate blade vibration response. Detailed flow field analysis is carried out to further investigate the mechanism of blade excitation. The results show that distributions of harmonic pressure amplitude on pressure surface (PS) and suction surface (SS) are both dominated by tip leakage vortex, whereas the roles that tip leakage vortex plays are quite different. Specifically, tip leakage vortex influences harmonic pressure amplitude on SS directly because of short distance between vortex core and SS, whereas it influences harmonic pressure amplitude on PS indirectly by interfering the evolution of passage vortex. This research can guide new designs for durable vaneless radial turbines without sacrificing aerodynamic performance.

Tip Clearance Flow Visualization of a Turbine Blade Cascade With Active and Passive Flow Control

2008 ◽  
Author(s):  
Daniel K. Van Ness ◽  
Thomas C. Corke ◽  
Scott C. Morris
Keyword(s):  
Flow Control ◽  
Flow Visualization ◽  
Total Pressure ◽  
Plasma Actuator ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Blade Cascade ◽  
Clearance Flow ◽  
Blade Tip

The secondary flow in the tip clearance region of a stationary linear low pressure turbine blade cascade was studied using two types of surface flow visualization and documented using wake pressure measurements in order to identify the potential means and impact of flow control to reduce losses associated with the tip clearance flow. An evaporating fluid mixture was used for flow visualization on the casing surface of the tip clearance. An oil ink-dot tracing method was used on the blade tip. These measurements illustrate the important features of the near-casing flow physics, including the size and chordwise extent of the blade tip separation bubble, separation lines on the casing, the flow direction on the blade tip and casing, the size and exit trajectory of the tip leakage and passage vortices, as well as the total pressure loss and secondary velocity vectors downstream of the blade. The flow was visualized in this way for a plain, flat tip, a tip mounted plasma actuator, and a partial suction side squealer tip. Both flow control devices were observed to affect the flow in the clearance. The plasma actuator was shown to improve the total pressure loss in the tip leakage vortex by as much as 9% from the loss over the plain tip blade. The tests were performed over a Reynolds numbers range between 5.3 × 104 and 1.04 × 105 at a fixed tip clearance of 2% of axial chord.

PIV Maps of Tip Leakage and Secondary Flow Fields on a Low Speed Turbine Blade Cascade With Moving Endwall

2005 ◽  
Author(s):  
P. Palafox ◽  
M. L. G. Oldfield ◽  
J. E. LaGraff ◽  
T. V. Jones
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Field Measurements ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Low Speed ◽  
Tip Leakage

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110 degrees and blade chord of 1.0 m. Data was obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0 × 105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle Image Velocimetry (PIV) was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip endwall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the under-tip flow near the endwall due to the moving wall is observed and the effect on the tip leakage vortex examined.

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