scholarly journals Flow Field Investigation in the Exit Region of a Radial Inflow Turbine Using LDV

1994 ◽  
Author(s):  
D. Muthuvel Murugan ◽  
Widen Tabakoff ◽  
Awatef Hamed
Keyword(s):  
Flow Field ◽  
Field Investigation ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Complex Flow ◽  
Tip Clearance Flow ◽  
Exit Region ◽  
Flow Investigation ◽  
Clearance Flow ◽  
Radial Inflow Turbine

Detailed flow investigation in the downstream region of a radial inflow turbine has been performed using a three component Laser Doppler Velocimetry. The flow velocities are measured in the exit region of the turbine at off-design operating conditions. The results are presented as contour and vector plots of mean velocities, flow angles and turbulent stresses. The measured parameters are correlated to the rotor blade rotation to observe any periodic nature of the flow. The measurements reveal a complex flow pattern near the tip region at the rotor exit due to the interaction of the tip clearance flow. The degree of swirl of the flow near the tip region at the rotor exit is observed to be high due to the gross under turning of the flow near the tip region. The effect of the rotor on the exit flow field is observed in the proximity of the rotor exit.

scholarly journals Flow and Fast Fourier Transform Analyses for Tip Clearance Effect in an Operating Kaplan Turbine

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 264 ◽  
Author(s):  
Hyoung-Ho Kim ◽  
Md Rakibuzzaman ◽  
Kyungwuk Kim ◽  
Sang-Ho Suh
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Kaplan Turbine ◽  
Turbine Performance ◽  
Wide Range ◽  
Clearance Flow ◽  
Fft Analysis

The Kaplan turbine is an axial propeller-type turbine that can simultaneously control guide vanes and runner blades, thus allowing its application in a wide range of operations. Here, turbine tip clearance plays a crucial role in turbine design and operation as high tip clearance flow can lead to a change in the flow pattern, resulting in a loss of efficiency and finally the breakdown of hydro turbines. This research investigates tip clearance flow characteristics and undertakes a transient fast Fourier transform (FFT) analysis of a Kaplan turbine. In this study, the computational fluid dynamics method was used to investigate the Kaplan turbine performance with tip clearance gaps at different operating conditions. Numerical performance was verified with experimental results. In particular, a parametric study was carried out including the different geometrical parameters such as tip clearance between stationary and rotating chambers. In addition, an FFT analysis was performed by monitoring dynamic pressure fluctuation on the rotor. Here, increases in tip clearance were shown to occur with decreases in efficiency owing to unsteady flow. With this study’s focus on analyzing the flow of the tip clearance and its effect on turbine performance as well as hydraulic efficiency, it aims to improve the understanding on the flow field in a Kaplan turbine.

scholarly journals An Experimental Study of Tip Clearance Flow in a Radial Inflow Turbine

1998 ◽  
Author(s):  
R. Dambach ◽  
H. P. Hodson ◽  
I. Huntsman
Keyword(s):  
Tip Clearance ◽  
Leakage Flow ◽  
Hot Wire ◽  
Tip Leakage Flow ◽  
Axial Turbine ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Radial Turbine ◽  
Clearance Flow ◽  
Radial Inflow Turbine

This paper describes an experimental investigation of tip clearance flow in a radial inflow turbine. Flow visualisation and static pressure measurements were performed. These were combined with hot-wire traverses into the tip gap. The experimental data indicates that the tip clearance flow in a radial turbine can be divided into three regions. The first region is located at the rotor inlet, where the influence of relative casing motion dominates the flow over the tip. The second region is located towards midchord, where the effect of relative casing motion is weakened. Finally a third region exists in the exducer, where the effect of relative casing motion becomes small and the leakage flow resembles the tip flow behaviour in an axial turbine. Integration of the velocity profiles showed that there is little tip leakage in the first part of the rotor because of the effect of scraping. It was found that the bulk of tip leakage flow in a radial turbine passes through the exducer. The mass flow rate, measured at four chordwise positions, was compared with a standard axial turbine tip leakage model. The result revealed the need for a model suited to radial turbines. The hot-wire measurements also indicated a higher tip gap loss in the exducer of the radial turbine. This explains why the stage efficiency of a radial inflow turbine is more affected by increasing the radial clearance than by increasing the axial clearance.

Experimental Investigations on Mixed Flow Impeller and Vane Diffuser Under Various Operating Conditions

2012 ◽  
Author(s):  
D. Ramesh Rajakumar ◽  
S. Ramamurthy ◽  
M. Govardhan
Keyword(s):  
Pressure Ratio ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Mixed Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Compressor ◽  
Vane Diffuser

Experimental Investigations are carried out to study the effect of tip clearance flow in a mixed flow compressor stage. Two configurations, namely; constant and variable clearance gaps between impeller and stationary shroud are considered. For the purpose of the present investigations, a mixed flow compressor stage is designed and fabricated. The flow investigations were carried out in a closed circuit compressor rig. Detailed steady and unsteady measurements were carried out for three clearance gaps, namely; 0.5 mm, 0.75 mm, 0.9 mm. From the experimental investigations it is shown that constant tip clearance configurations show better performance in terms of pressure ratio and efficiency compared to variable clearance configurations. For a given configuration the pressure ratio and efficiency of the stage decrease with increase in the tip gap without indicating any optimum value. Tip clearance flow has considerable effect on the flow through the diffuser and the unsteady flow gets amplified and carried away into the vane diffuser.

Physics of Tip Clearance Flow in Turbomachinery (Keynote Paper)

2002 ◽  
Author(s):  
Masahiro Inoue ◽  
Masato Furukawa
Keyword(s):  
Flow Field ◽  
Physical Interpretation ◽  
Vortex Core ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

In a recent advanced aerodynamic design of turbomachinery, the physical interpretation of three-dimensional flow field obtained by a numerical simulation is important for iterative modifications of the blade or impeller geometry. This paper describes an approach to the physical interpretation of the tip clearance flow in turbomachinery. First, typical flow phenomena of the tip clearance flow are outlined for axial and radial compressors, pumps and turbines to help comprehensive understanding of the tip clearance flow. Then, a vortex-core identification method which enables to extract the vortical structure from the complicated flow field is introduced, since elucidation of the vortical structure is essential to the physical interpretation of the tip clearance flow. By use of the vortex-core identification, some interesting phenomena of the tip clearance flows are interpreted, especially focussing on axial flow compressors.

Experimental Investigations of Tip Clearance Flow and its Influence on Secondary Flows in a 1-1/2 Stage Axial Turbine

2000 ◽  
Author(s):  
B. Stephan ◽  
H. E. Gallus ◽  
R. Niehuis
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Radial Clearance ◽  
Experimental Investigations ◽  
Axial Turbine ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

A multistage turbomachine has inherently unsteady flow fields due to the relative motion between rotor and stator airfoils, which lead to viscous and inviscid interactions between the blade rows. Additionally, the radial clearance between casing and rotor strongly influences the 3D flow field and the loss generation in turbomachines. The objective of the presented study is to investigate the effects of tip clearance on secondary flow phenomena and, in consequence, on the performance of a 1-1/2 stage axial turbine. The low aspect ratio of the blades and their prismatic design leads to a high degree of secondary flows and three-dimensionality. Extended measurements of the flow field behind each blade row with pneumatic and hotwire probes have been conducted for three different tip clearances. Experimental results reveal significant change of flow behavior and turbine performance with increasing tip clearance.

scholarly journals Flow Measurements and Flow Analysis in the Exit Region of a Radial Turbine

1997 ◽  
Vol 3 (2) ◽  
pp. 93-105 ◽  
Author(s):  
D. M. Murugan ◽  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Meridional Flow ◽  
Tip Clearance ◽  
Meridional Plane ◽  
Complex Flow ◽  
Flow Measurements ◽  
Tip Clearance Flow ◽  
Exit Region ◽  
Radial Turbine

Three-dimensional flow measurements using LDV system were obtained in the exit region of a radial inflow turbine at an off-design operating condition. The measurements reveal a complex flow pattern near the tip region at the rotor exit due to the interaction of the tip clearance flow. The effect of the rotor on the exit flow field is observed in the proximity of the rotor exit. Steady axisymmetric, compressible, turbulent flow computations with a two equation turbulence model were performed using the PARC code for the meridional flow in the radial turbine exit region. The computational results obtained in the meridional plane are compared with the experimental results, which are correlated to the rotor blade rotation in the exit region of the radial turbine.A version of this paper was presented at the 30th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Indianapolis, Indiana, Paper no. AIAA-94-3075.

Characteristics of Tip Clearance Flow Instability in a Transonic Compressor

2010 ◽  
Author(s):  
Chunill Hah ◽  
Melanie Voges ◽  
Martin Mueller ◽  
Heinz-Peter Schiffer
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Instability ◽  
Tip Clearance ◽  
Piv Measurements ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Clearance Vortex

In the present study, unsteady flow phenomena due to tip clearance flow instability in a modern transonic axial compressor rotor are studied in detail. First, unsteady flow characteristics due the oscillating tip clearance vortex measured with the particle image velocimetry (PIV) and casing-mounted unsteady pressure transducers are analyzed and compared to numerical results with a large eddy simulation (LES). Then, measured characteristic frequencies of the unsteady flow near stall operation are investigated. The overall purpose of the study is to advance the current understanding of the unsteady flow field near the blade tip in an axial transonic compressor rotor near the stall operating condition. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. The currently applied PIV measurements indicate that the flow near the tip region is unsteady even at the design condition. This self-induced unsteadiness increases significantly as the compressor operates toward the stall condition. PIV data show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The spectral analysis of measured end wall and blade surface pressure shows that there are two dominant frequencies near stall. One frequency is about 40–60% of the rotor rotation and the other dominant frequency is about 40–60% of the blade passing frequency (BPF). The first frequency represents the movement of a large blockage over several consecutive blade passages against the rotor rotation. The second frequency represents traditional tip flow instability, which has been widely observed in subsonic compressors. The LES simulations show that the second frequency is due to movement of the instability vortex.

Experimental Investigation on Tip Clearance Flow of Compressor Cascade With Blade Tip Winglet

2012 ◽  
Author(s):  
Shaobing Han ◽  
Jingjun Zhong ◽  
Huawei Lu ◽  
Xiaoxu Kan ◽  
Haiyang Gao
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Control Strategies ◽  
Suction Side ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip

This paper presents the results of experimental research of flow in an axial compressor cascade with different types of winglet on the blade tip, which consists of a suction-side winglet, pressure-side winglet and the combined winglet. The detailed tip leakage flow field with different winglet was described with total pressure loss coefficient, secondary streamline and axial vorticity on the cascade exit flow field. The mechanisms of the three passive control methods were illuminated. The result indicated that the tip clearance flow strengths could be reduced in all the three control strategies. The compressor aerodynamic performance could be improved via the addition of tip winglets. The suction-side winglet had the best effect on the cascade flow field, and the strength of leakage vortex and the associated mixture losses were reduced.

scholarly journals Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

1996 ◽  
Vol 118 (2) ◽  
pp. 218-229 ◽  
Author(s):  
K. L. Suder ◽  
M. L. Celestina
Keyword(s):  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Peak Efficiency ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Design Speed

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part-speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100 percent design speed and at near peak efficiency at 60 percent design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only five times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the end-wall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part-speed conditions is also discussed.

scholarly journals Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

1997 ◽  
Author(s):  
G. J. Skoch ◽  
P. S. Prahst ◽  
M. P. Wernet ◽  
J. R. Wood ◽  
A. J. Strazisar
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Vaneless Diffuser ◽  
Suction Surface ◽  
Tip Clearance Flow ◽  
Through Flow ◽  
Clearance Flow ◽  
Flow Velocities

A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

Sign in / Sign up

Export Citation Format

Share Document