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.

Numerical Investigation of Tip Clearance Flow in an Axial Compressor Cascade

2014 ◽  
Vol 599-601 ◽  
pp. 368-371
Author(s):  
Zhi Hui Xu ◽  
He Bin Lv ◽  
Ru Bin Zhao
Keyword(s):  
Computational Simulation ◽  
Suction Side ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow ◽  
Blade Tip

Using blade tip winglet to control the tip leakage flow has been concerned in the field of turbomachinery. Computational simulation was conducted to investigate the phenomenological features of tip clearance flow. The simulation results show that suction-side winglet can reduce leakage flow intensity. The tip winglet can also decrease tip leakage mass flow and weaken tip leakage flow mixing with the mainstream and therefore reduce the total pressure loss at the blade tip.

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%.

Method for Non-Dimensional Tip Leakage Flow Characterization in Radial Turbines

2018 ◽  
Author(s):  
José Ramón Serrano ◽  
Roberto Navarro ◽  
Luis Miguel García-Cuevas ◽  
Lukas Benjamin Inhestern
Keyword(s):  
Suction Side ◽  
Tip Clearance ◽  
Navier Stokes ◽  
The Novel ◽  
Tip Leakage Flow ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Wide Range ◽  
Clearance Flow

Tip leakage loss characterization and modeling plays an important role in small size radial turbine research. The momentum of the flow passing through the tip gap is highly related with the tip leakage losses. The ratio of fluid momentum driven by the pressure gradient between suction side and pressure side and the fluid momentum caused by the shroud friction has been widely used to analyze and to compare different sized tip clearances. However, the commonly used number for building this momentum ratio lacks some variables, as the blade tip geometry data and the viscosity of the used fluid. To allow the comparison between different sized turbocharger turbine tip gaps, work has been put into finding a consistent characterization of radial tip clearance flow. Therefore, a non-dimensional number has been derived from the Navier Stokes Equation. This number can be calculated like the original ratio over the chord length. Using the results of wide range CFD data, the novel tip leakage number has been compared with the traditional and widely used ratio. Furthermore, the novel tip leakage number can be separated into three different non-dimensional factors. First, a factor dependent on the radial dimensions of the tip gap has been found. Second, a factor defined by the viscosity, the blade loading, and the tip width has been identified. Finally, a factor that defines the coupling between both flow phenomena. These factors can further be used to filter the tip gap flow, obtained by CFD, with the influence of friction driven and pressure driven momentum flow.

Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage

2010 ◽  
Author(s):  
Hongwei Ma ◽  
Jun Zhang ◽  
Jinghui Zhang ◽  
Zhou Yuan
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
High Loss ◽  
Static Pressure Distribution ◽  
Blade Tip

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade respectively with two tip clearance configurations, including flat tip and grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower spanwise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0° and 5° with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.

Effects of Tip Clearance on Unsteady Flow Characteristics in an Axial Turbine Stage

2009 ◽  
Author(s):  
Hao Sun ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Suction Side ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The clearance between the rotor blade tip and casing wall in turbomachinery passages induces leakage flow loss and thus degrades aerodynamic performance of the machine. The flow field in turbomachinery is significantly influenced by the rotor blade tip clearance size. To investigate the effects of tip clearance size on the rotor-stator interaction, the turbine stage profile from Matsunuma’s experimental tests was adopted, and the unsteady flow fields with two tip clearance sizes of 0.67% and 2.00% of blade span was numerical simulated based on Harmonic method using NUMECA software. By comparing with the domain scaling method, the accuracy of the harmonic method was verified. The interaction mechanism between the stator wake and the leakage flow was investigated. It is found that the recirculation induced by the stator wake is separated by a significant “interaction line” from the flow field close to the suction side in the clearance region. The trend of the pressure fluctuation is contrary on both sides of the line. When the stator wakes pass by the suction side, the pressure field fluctuates and the intensity of the tip leakage flow varies. With the clearance size increasing, the “interaction line” is more far away from the suction side and the intensity of tip leakage flow also fluctuates more strongly.

Numerical Simulation of Tip Clearance Flow Control in Axial Turbine Rotor: Part 1—Active Flow Control Injection From Turbine Blade Tip

2008 ◽  
Author(s):  
Wei Li ◽  
Wei-Yang Qiao ◽  
Kai-Fu Xu ◽  
Hua-Ling Luo
Keyword(s):  
Flow Control ◽  
Turbine Blade ◽  
Stokes Equations ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Injection Hole ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Part ◽  
Blade Tip

Reducing loss and increasing efficiency are always pursued in the designing of the turbine, and flow control is an efficient solution to minimize the tip clearance loss. Recently it aroused much attention in the field of the turbine tip clearance flow. Part-1 of this paper aims to numerically investigate the effect of active turbine clearance flow control by injection from a turbine blade tip on the tip clearance flow. Part-2 of this paper focus on the passive turbine tip clearance flow control. A density-correction based, 3D Reynolds-averaged Navier-Stokes equations CFD code with Reynolds Stress Model, which was proved to be validated, was adopted. The variable specific heat was considered. The effects of injection on the tip clearance flow were simulated in two tip clearance heights, and each height corresponds to five injection hole locations and five injection mass flow rates. Accordingly, the mechanisms of active injection control were put in evidence; the effects of the injection on the turbine efficiency which includes the effect of the jet and the tip clearance flow were highlighted; and the tip clearance flow structure was analyzed topologically. If the tip leakage flow corresponding to the injection location is subsonic, this injection can increase the efficiency, such as the first and the second jet. The combined jet could increase the efficiency by 0.35% for the case of loose tip clearance and by 0.3% for the case of tight tip clearance. The number of saddle points was equal to that of nodes near the injection hole, which could satisfy the singularity point total number law.

Investigation of the Tip Clearance Flow in a Compressor Cascade Using a Novel Laser Measurement Technique With High Temporal Resolution

2011 ◽  
Author(s):  
Andreas Fischer ◽  
Lars Bu¨ttner ◽  
Ju¨rgen Czarske ◽  
Marcel Gottschall ◽  
Ronald Mailach ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Measurement Technique ◽  
Tip Clearance ◽  
High Temporal Resolution ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Flow Measurements ◽  
Tip Clearance Flow ◽  
Array Measurements ◽  
Clearance Flow

The understanding of the tip clearance flow in axial compressors is a key issue for developing new compressors with enhanced efficiency and reduced noise for instance. However, necessary flow measurements in the blade tip region and within the tip clearance are challenging due to the small gap width. The application of a novel optical measurement technique named Doppler global velocimetry with laser frequency modulation is presented, which provides velocity field measurements of all three velocity components non-intrusively in the tip clearance flow of a linear cascade at near stall conditions. These array measurements have a high temporal resolution enabling turbulence analysis such as the evaluation of velocity standard deviations and turbulence spectra up to several kilohertz. Conventional pneumatic and hot-wire measurements in planes at the inlet and the outlet as well as on the blade surface were taken to complete the flow pattern and validate the data of the Doppler global velocimetry. Wake measurements identified a strong flow separation in the rear suction side dominating the transient character of the cascade flow. Towards the endwall this high loss region is reduced by the clearance flow and the resulting vortex, which is obviously not affected by the profile separation and the pulsating blockage frequency. Inside the blade passage and the tip clearance the Doppler global velocimetry measurements allowed a spatial assignment of the origin of the tip leakage flow and the downstream developing vortex. In addition, the tip clearance vortex could be resolved and identified successfully as the most dominant turbulence generating effect in the near endwall region at this high loading operating point of the blading.

The Flow Field in the Tip Clearance Region of an Axial Compressor Rotor

1999 ◽  
Author(s):  
Toshiyuki Arima ◽  
Masatoshi Shirotori ◽  
Yoshihiro Yamaguchi
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Grid Topology ◽  
Clearance Flow ◽  
Inflow Condition ◽  
Blade Tip ◽  
Single Block

A three-dimensional, Reynolds-averaged, compressible Navier-Stokes analysis (using a multi-block grid with the grid embedded in the tip-clearance space) has been developed to study the tip-clearance flow of an axial compressor rotor. A low-Reynolds number k-ε model have been used to reproduce the effects of turbulence. In order to assess the effect of the tip-clearance-grid treatment on prediction for the tip-clearance flow, calculations using a single-block grid (pinched grid topology) and multi-block grid (embedded grid topology) have been performed to calculate the flow field of NASA Rotor 37. The results are compared with experimental data. It has been found that both the single-block and multi-block approaches give a good agreement with the experimental data regarding the overall performance map of the rotor. For the prediction of the spanwise distributions of averaged aerodynamic properties downstream of the rotor, however, the orderly grid over the blade tip associated with the embedded grid has produced accurate predictions particularly from 40% to 80% span. In order to investigate the tip-clearance flow for different operating conditions, calculations have been performed for conditions at 100% (transonic inflow condition) and 60% (subsonic inflow condition) of the design point speed. Computed limiting streamlines at the blade tip surface and particle traces released from the tip-clearance have been used to study the tip-clearance flow. At the 100% speed, both separation and reattachment lines have been observed and a separation bubble occurs. At the 60% speed, the separation line shifts to the blade pressure side and the reattachment line can be partly observed near the leading edge of the blade tip surface. In order to investigate the interaction of the leakage vortex from the tip clearance with the main flow, the computed secondary flows on the cross-flow sections have been analyzed at the 100% and the 60% speeds. At the 100% speed, the vortex core apparently increases in size, as it moves downstream. At 60% speed, the second vortex, first reported by Suder and Celestina in 1994, is barely observable. Furthermore, the trajectory of vortex core identified using a semi-analytical method has also been used to study the vortex motion in the flow field near the blade tip.

A Correlation of Leakage Vortex Cavitation in Axial-Flow Pumps

1994 ◽  
Vol 116 (3) ◽  
pp. 551-557 ◽  
Author(s):  
K. J. Farrell ◽  
M. L. Billet
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Suction Side ◽  
Tip Clearance ◽  
Vortical Flow ◽  
Data Sets ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
High Reynolds

Tip clearance flow in turbomachinery can lead to losses in efficiency and stall margin. In liquid handling turbomachinery, the vortical flow field, formed from the interaction of the leakage flow with the through-flow, is subject to cavitation. Furthermore, this flow field is complex and not well understood. A correlation of variables which predict the vortex minimum pressure has been formulated. Measurements of the important variables for this correlation have been made on a high Reynolds number (3 × 106) axial-flow test rig. The correlation has been applied to the measured data and other data sets from the literature with good agreement. An optimum tip clearance has been theoretically identified as experiments have shown. Observations of cavitation indicate a second vortex originating along the suction side trailing edge.

Investigation of the Tip Clearance Flow in a Compressor Cascade Using a Novel Laser Measurement Technique With High Temporal Resolution

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Andreas Fischer ◽  
Lars Büttner ◽  
Jürgen Czarske ◽  
Marcel Gottschall ◽  
Konrad Vogeler ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Measurement Technique ◽  
Tip Clearance ◽  
High Temporal Resolution ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Flow Measurements ◽  
Tip Clearance Flow ◽  
Array Measurements ◽  
Clearance Flow

The understanding of the tip clearance flow in axial compressors is a key issue for developing new compressors with enhanced efficiency and reduced noise for instance. However, necessary flow measurements in the blade tip region and within the tip clearance are challenging due to the small gap width. The application of a novel optical measurement technique named Doppler global velocimetry with laser frequency modulation is presented, which provides velocity field measurements of all three velocity components nonintrusively in the tip clearance flow of a linear cascade at near stall conditions. These array measurements have a high temporal resolution enabling turbulence analysis such as the evaluation of velocity standard deviations and turbulence spectra up to several kilohertz. Conventional pneumatic and hot-wire measurements in planes at the inlet and the outlet as well as on the blade surface were taken to complete the flow pattern and validate the data of the Doppler global velocimetry. Wake measurements identified a strong flow separation in the rear suction side dominating the transient character of the cascade flow. Towards the endwall this high loss region is reduced by the clearance flow and the resulting vortex, which is obviously not affected by the profile separation and the pulsating blockage frequency. Inside the blade passage and the tip clearance the Doppler global velocimetry measurements allowed a spatial assignment of the origin of the tip leakage flow and the downstream developing vortex. In addition, the tip clearance vortex could be resolved and identified successfully as the most dominant turbulence generating effect in the near endwall region at this high loading operating point of the blading.

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