The Influence of Suction-Side Winglet on Tip Leakage Flow in Compressor Cascade

2011 ◽  
Author(s):  
Jingjun Zhong ◽  
Shaobing Han ◽  
Peng Sun
Keyword(s):  
Numerical Study ◽  
Flow Behavior ◽  
Velocity Ratio ◽  
Suction Side ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Cascade Flow ◽  
Highly Loaded

The effect of tip winglet on the aerodynamic performance of compressor cascade are mainly determined by the location of the tip winglet, the tip winglet geometry, the size of tip clearance, and the aerodynamic parameters of the cascade. In this paper, an extensive numerical study which includes three aspects has been carried out to investigate the effects of these influencing factors in a highly-loaded compressor cascade in order to give the guidance for the application of tip winglet to control the tip leakage in modern highly-loaded compressor. Firstly, the numerical method is validated by comparing the numerical results with available measured data. Results show that the numerical procedure is valid and accurate. Then, the cascade flow fields are interrogate to identify the physical mechanism of how suction-side winglet improve the cascade flow behavior. It is found that a significant tip leakage mass flow rate and aerodynamic loss reduction is possible by using proper tip winglet located near the suction side corner of the blade tip. Finally, an optimum width of the suction-side tip winglet is obtained by comparing the compressor performance with different clearances and incidences. The use of the suction-side winglet can reduce the pressure difference between the pressure and the suction sides of the blade and tip leakage velocity ratio. And the winglet also can compact the tip leakage vortex structure, which is benefit to decrease the loss of the tip secondary flow mixing with the primary flow.

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 Study of the Effect of Honeycomb Tip on Tip Leakage Flow in Turbine Cascade

2016 ◽  
Author(s):  
Yunfeng Fu ◽  
Fu Chen ◽  
Cong Chen ◽  
Yanping Song
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Honeycomb Seal ◽  
Leakage Flow Rate ◽  
Highly Loaded

A novel leakage flow control strategy with honeycomb seal applied on the tip of the rotor blades in a highly-loaded turbine cascade is proposed. The numerical method is used to study the tip leakage flow in a highly-loaded turbine cascades with flat tip and with honeycomb seal structure, the mechanism of honeycomb tip on inhibiting leakage flow is analyzed, the influence of various relative gap heights is also been investigated. The discussions of the action of the honeycomb-tip structure in reducing leakage flow and improving the turbine efficiency provide the according for control methods of tip leakage flow. Through the comparative study among three different tip structures of honeycomb tip, honeycomb casing and flat tip, the results show that both honeycomb tip and honeycomb casing inhibit the leakage flow effectively, but honeycomb tip has positive effect on reducing the flow loss in cascade. For the cascade with honeycomb tip, on one hand, the vortices rolled up in the regular hexagon honeycomb cavities dissipate the energy of the tip leakage flow, and the range of influence of the vortices is nearly one third of the tip clearance height. On the other hand, the radial jets caused by the honeycomb obstruct the tip leakage flow like a “pneumatic fence”, resulting in weaker leakage flow and less leakage flow rate. Besides, the honeycomb tip reduces the scale of the leakage vortex, thus the leakage loss also decreases. Compared with the flat tip cascade at the clearance height of 1%H, the honeycomb tip cascade with the same clearance height obtains decrease of the leakage flow rate and leakage flow speed in circumference by 10.16% and 20%. As a result, the leakage vortex in honeycomb tip cascade is undermined, the loss is reduced by nearly 4.43%. Considering the abradable property of the honeycomb seal that can protect the blade tips from damage, the cascade with honeycomb tip structure can obtain a smaller clearance height and achieve better sealing effect. Compared to cascade with the flat tip at the clearance height of 2%H, the amount of leakage flow using inlet flow in the honeycomb tip cascades decreases by 17.33%, 36.63% and 54.79% at the clearance heights of 2%H, 1.5%H and 1%H, the losses related to the leakage flow is reduced by nearly 5.71%, 14.33% and 25.24%, respectively.

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.

scholarly journals Tip Leakage Flow in Linear Compressor Cascade

1993 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Design Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Linear Compressor ◽  
Tip Leakage ◽  
Flow Mixing ◽  
Internal Loss ◽  
Linear Compressor Cascade

Tip leakage flow in a linear compressor cascade of NACA 65-1810 profiles is investigated, for tip clearance levels of 1.0, 2.0 and 3.25 percent of chord at design and off-design flow conditions. Data, velocity and pressures, are collected from three transverse sections inside tip clearance and sixteen sections within flow passage. Tip separation vortex influence is identified from the data. Leakage flow mixing is clearly present inside the clearance and has a significant influence on the internal loss.

scholarly journals Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines

1998 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson ◽  
David L. Rigby
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
Tip Clearance ◽  
Flow Conditions ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip ◽  
Axial Turbines ◽  
Gap Height ◽  
Stage Efficiency

Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E3 first stage turbine, which represents a modern gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.

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 Study on Tip Clearance Effect on Performance of a Centrifugal Compressor

2002 ◽  
Author(s):  
Hark-Jin Eum ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Specific Work ◽  
Tip Leakage Flow ◽  
Viscous Effects ◽  
Tip Leakage ◽  
Performance Reduction ◽  
Viscous Loss

Effects of tip clearance on through flows and performance of a centrifugal compressor impeller with six different tip clearances were numerically studied using CFX-TASCflow. The flow structures inside the impeller of a centrifugal compressor were visualized observing streamlines starting the leading edge of blade tips. The calculated results at the impeller exit were circumferential averaged for quantitative discussion. Flow, pressure and entropy contours at the impeller exit were largely influenced by the tip leakage flow. Tip clearance effect on the performance was decomposed into inviscid and viscous components using one-dimensional relations expressed in terms of the specific work reduction and the additional entropy generation. Both inviscid and viscous effects affected performance to similar extent, while efficiency drop was mainly influenced by viscous loss of the tip leakage flow. Performance reduction and efficiency drop due to tip clearance was proportional to the ratio of tip clearance to blade height. A simple model suggested in the present study predicts performance and efficiency drop quite successfully.

Effect of Endwall Motion on Blade Tip Heat Transfer

2003 ◽  
Vol 125 (2) ◽  
pp. 267-273 ◽  
Author(s):  
V. Srinivasan ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Gradients ◽  
Tip Leakage Flow ◽  
Blade Loading ◽  
Linear Cascade ◽  
Tip Leakage ◽  
Blade Tip ◽  
Wind Tunnel Data

Local mass transfer measurements were conducted on the tip of a turbine blade in a five-blade linear cascade with a blade-centered configuration. The tip clearance levels ranged from 0.6 to 6.9% of blade chord. The effect of relative motion between the casing and the blade tip was simulated using a moving endwall made of neoprene mounted on the top of the wind tunnel. Data were obtained for a single Reynolds number of 2.7×105 based on cascade exit velocity and blade chord. Pressure measurements indicate that the effect of endwall motion on blade loading at a clearance of 0.6% of blade chord is to reduce the pressure gradients driving the tip leakage flow. With the introduction of endwall motion, there is a reduction of about 9% in mass transfer levels at a clearance of 0.6% of chord. This is presumably due to the tip leakage vortex coming closer to the suction side of the blade and ‘blocking the flow,’ leading to reduced tip gap velocities and hence lower mass transfer.

Effect of Various Trench Designs on Axial Compressor Blade Tip Aerodynamics

2019 ◽  
Author(s):  
Ashwin Ashok ◽  
Patur Ananth Vijay Sidhartha ◽  
Shine Sivadasan
Keyword(s):  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Leakage Vortex ◽  
Stall Margin ◽  
Casing Treatment ◽  
Tip Leakage

Abstract Tip clearance of axial compressor blades allows leakage of the flow, generates significant losses and reduces the compressor efficiency. The present paper aims to discuss the axial compressor tip aerodynamics for various configurations of tip gap with trench. The various configurations are obtained by varying the clearance, trench depth, step geometry and casing contouring. In this paper the axial compressor aerodynamics for various configurations of tip gap with trench have been studied. The leakage flow structure, vorticity features and entropy generations are analyzed using RANS based CFD. The linear compressor cascade comprises of NACA 651810 blade with clearance height varied from 0.5% to 2% blade span. Trail of the tip leakage vortex and the horseshoe vortex on the blade suction side are clearly seen for the geometries with and without casing treatments near the stalling point. Since the trench side walls are similar to forward/backing steps, a step vortex is observed near the leading edge as well as trailing edge of the blade and is not seen for the geometry without the casing treatment. Even though the size of the tip leakage vortex seams to be reduces by providing a trench to the casing wall over the blade, the presence of additional vortices like the step vortex leads to comparatively higher flow losses. An increase in overall total pressure loss due to the application of casing treatment is observed. However an increase in stall margin for the geometries with casing is noted.

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