Design of Turbine Cascade with Leakage Flow System

2021 ◽  
Vol 24 (5) ◽  
pp. 44-48
Author(s):  
Dunam Hong ◽  
Myungho Kim ◽  
Seungjin Song
Keyword(s):  
Flow System ◽  
Leakage Flow ◽  
Turbine Cascade

Effect of leakage flow on the endwall cooling performance in high subsonic turbine cascade

2021 ◽  
Vol 170 ◽  
pp. 107140
Author(s):  
Hongyu Gao ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Leakage Flow ◽  
Turbine Cascade ◽  
Cooling Performance ◽  
Endwall Cooling

Experimental and Numerical Study of Honeycomb Tip on Suppressing Tip Leakage Flow in Turbine Cascade

2017 ◽  
Author(s):  
Yunfeng Fu ◽  
Fu Chen ◽  
Huaping Liu ◽  
Yanping Song
Keyword(s):  
Numerical Study ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Exit Section ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Physical Processes ◽  
Tip Leakage ◽  
Gap Height ◽  
Positive Effect

In this paper, the effect of a novel honeycomb tip on suppressing tip leakage flow in a highly-loaded turbine cascade has been experimentally and numerically studied. The research focuses on the mechanisms of honeycomb tip on suppressing tip leakage flow and affecting the secondary flow in the cascade, as well as the influences of different clearance heights on leakage flow characteristics. In addition, two kinds of local honeycomb tip structures are pro-posed to explore the positive effect on suppressing leakage flow in simpler tip honeycomb structures. Based on the experimental and numerical results, the physical processes of tip leakage flow and its interaction with main flow are analyzed, the following conclusions can be obtained. Honeycomb tip rolls up a number of small vortices and radial jets in regular hexagonal honeycomb cavities, increasing the flow resistance in the clearance and reducing the velocity of leakage flow. As a result, the structure of honeycomb tip not only suppresses the leakage flow effectively, but also has positive effect on reducing the associated losses in cascade by reducing the strength of leakage vortex. Compare to the flat tip cascade at 1%H gap height, the relative leakage flow in honeycomb tip cascade reduces from 3.05% to 2.73%, and the loss at exit section is also decreased by 10.63%. With the increase of the gap height, the tip leakage flow and loss have variations of direct proportion with it, but their growth rates in the honeycomb tip cascade are smaller. Consider the abradable property of the honeycomb seal, a smaller gap height is allowed in the cascade with honeycomb tip, and that means honeycomb tip has better effect on suppressing leakage flow. Two various local honeycomb tip structures has also been discussed. It shows that local raised honeycomb tip has better suppressing leakage flow effect than honeycomb tip, while local concave honeycomb tip has no more effect than honeycomb tip. Compare to flat tip cascade, the leakage flow in honeycomb tip cascade, local concave tip cascade and local raised honeycomb tip cascade decrease by nearly 17.33%, 15.51% and 30.86% respectively, the losses at exit section is reduced by 13.38%, 12% and 28.17% respectively.

Aerodynamic Interaction Between Incoming Vortex and Tip Leakage Flow in a Turbine Cascade

2018 ◽  
Author(s):  
Kai Zhou ◽  
Chao Zhou
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Computational Domain ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Swirl Generator ◽  
Swirling Vortex

In turbines, secondary vortices and tip leakage vortices develop and interact with each other. In order to understand the flow physics of vortices interaction, the effects of incoming vortex on the downstream tip leakage flow are investigated in terms of the aerodynamic performance in a turbine cascade. Experimental, numerical and analytical methods are used. In the experiment, a swirl generator was used upstream near the casing to generate the incoming vortex, which interacted with the tip leakage vortex in the turbine cascade. The swirl generator was located at ten different pitchwise locations to simulate the quasi-steady effects. In the numerical study, a Rankine-like vortex was defined at the inlet of the computational domain to simulate the incoming swirling vortex. Incoming vortices with opposite directions were investigated. The vorticity of the positive incoming swirling vortex has a large vector in the same direction as that of the tip leakage vortex. In the case of the positive incoming swirling vortex, the vortex mixes with the tip leakage vortex to form one vortex near the tip as it transports downstream. The vortices interaction reduces the vorticity of the flow near the tip, as well as the loss by making up for the streamwise momentum within the tip leakage vortex core. In contrast, the negative incoming swirling vortex has little effects on the tip leakage vortex and the loss. As the negative incoming swirling vortex transports downstream, it is separated from the tip leakage vortex and forms two vortices. A triple-vortices-interaction kinetic analytical model and one-dimensional mixing model are proposed to explain the mechanism of vortex interaction on the aerodynamic performance.

Experimental and Numerical Study of Honeycomb Tip on Suppressing Tip Leakage Flow in Turbine Cascade

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Yunfeng Fu ◽  
Fu Chen ◽  
Huaping Liu ◽  
Yanping Song
Keyword(s):  
Numerical Study ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Honeycomb Seal ◽  
Clearance Flow ◽  
Flow Part ◽  
Gap Height ◽  
Locally Convex

In this paper, the effect of a novel honeycomb tip on suppressing tip leakage flow in turbine cascade has been experimentally and numerically studied. Compared to the flat tip cascade with 1%H blade height, the relative leakage flow in honeycomb tip cascade reduces from 3.05% to 2.73%, and the loss also decreases by 8.24%. For honeycomb tip, a number of small vortices are rolled up in the regular hexagonal honeycomb cavities to dissipate the kinetic energy of the clearance flow, and the fluid flowing into and out the cavities create aerodynamic interceptions to the upper clearance flow. As a result, the flow resistance in the clearance increased and the velocity of leakage flow reduced. As the gap height increases, the tip leakage flow and loss changes proportionally, but the growth rate in the honeycomb tip cascade is smaller. Considering its wear resistance of the honeycomb seal, a smaller gap height is allowed in the cascade with honeycomb tip, and that means honeycomb tip has better effect on suppressing leakage flow. Part honeycomb tip structure also retains the effect of suppressing leakage flow. It shows that locally convex honeycomb tip has better suppressing leakage flow effect than the whole honeycomb tip, but locally concave honeycomb tip is slightly less effective.

Tip Leakage Flow Reduction of a Linear Turbine Cascade Using String-Type DBD Plasma Actuators

2018 ◽  
Author(s):  
Takayuki Matsunuma ◽  
Takehiko Segawa
Keyword(s):  
Reynolds Number ◽  
Plasma Actuators ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Dbd Plasma ◽  
Tip Leakage ◽  
String Type ◽  
Displacement Thickness ◽  
Blade Tip

Tip leakage flow through the small gap between the blade tip of a turbine and the casing endwall reduces the aerodynamic performance. String-type dielectric barrier discharge (DBD) plasma actuators made of silicone printed-circuit board were used for the active control of the tip leakage flow of a linear turbine cascade. Sinusoidal voltage excitation with amplitude varying from 4 kV to 6 kV (peak-to-peak voltage: 8 kVp-p to 12 kVp-p) and fixed frequency of 10 kHz was applied to the plasma actuators. The two-dimensional velocity field in the blade passage was estimated by particle image velocimetry (PIV) under the very low Reynolds number conditions of Re = 7.1 × 103 and 1.42 × 104. The tip leakage flow was reduced by the flow control using plasma actuators. The high turbulence intensity region caused by the tip leakage flow was also reduced. For the quantitative comparisons, the displacement thickness of the absolute velocity distributions was examined. By the flow control of the plasma actuators, the displacement thickness at tip-side gradually decreased as the input voltage increased. Although three types of plasma actuators were used, with thin, thick, and flat electrodes and different ratios of discharge area, the differences in their effect were negligible. The reason for these very small differences in effect is the wide spread of the plasma discharge from the encapsulated electrode in the plasma actuator to the exposed electrode of the blade tip. At the relatively high Reynolds number condition of Re = 1.42 × 104, the effect of the plasma actuator was smaller than that at the lower Reynolds number condition of Re = 7.1 × 103.

Study on Leakage Loss Control Method of Circumferential Bending Clearance

2019 ◽  
Author(s):  
Shuai Jiang ◽  
Fu Chen ◽  
Jianyang Yu ◽  
Shaowen Chen ◽  
Yanping Song
Keyword(s):  
Control Method ◽  
Incidence Angle ◽  
Leading Edge ◽  
Blocking Effect ◽  
Field Analysis ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Control Effect ◽  
Tip Leakage

Abstract The concept of circumferential bending clearance based on Gauss Bimodal Function is proposed to suppress tip leakage flow (TLF) in a highly-loaded turbine cascade. In this method, a new vortex (BV) can be induced to mix with TLV in the middle of tip region and block the development of tip leakage vortex (TLV). Since the blocking effect divides the TLV into two parts, the tip leakage rate and loss of TLF can be reduced significantly. In order to reveal the mechanisms of blocking effect on leakage flow and its influencing factors, the research numerically investigates the effects of environmental conditions on the TLF development in a turbine cascade. The flow field analysis of the optimal bending clearance is in the first place, and then the effects of clearance heights (δ) and incidence angles (α) on the TLF characteristic and loss are investigated respectively. Results indicate that the blocking effect has a close relationship with the TLF characteristic, which can be divided into the BV migration, TLV-2 location and blocking loss. The nearer distance to the leading edge (LE) and farther distance to the suction side (SS) of BV means a less loss of TLF in bending clearance cases. The further distance away from blade tip and SS of TLV-2 means a larger-scale vortex with more loss. The additional loss in blocking region expands constantly with the increase of clearance height and incidence angle. The bending clearance has limited control effect on TLF with the variation of clearance height, especially the loss increases in Case 2%H. However, it has a strong adaptability with the change of incidence angle, the relative total pressure loss drops up to 16% in Case −5°.

An Innovative Passive Tip-Leakage Control Method for Axial Turbines: Linear Cascade Wind Tunnel Results

2008 ◽  
Author(s):  
Markus Hamik ◽  
Reinhard Willinger
Keyword(s):  
Wind Tunnel ◽  
Turbine Blade ◽  
Working Fluid ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip ◽  
Tip Injection ◽  
Tip Desensitization

Depending on the blade aspect ratio, tip-leakage losses can contribute up to one third of the total losses in an axial turbine blade row. In unshrouded turbine blade rows, the radial gaps allow working fluid to pass from the pressure to the suction sides. This tip-leakage flow does not contribute to the work output of the turbine stage. Therefore, any technique which tends to reduce tip-leakage losses has the objective to decrease the flow through the tip gaps. A frequently used method of reducing the tip-leakage flow is the modification of the blade tip geometry by so-called squealers or winglets. Since this method decreases the sensitivity of tip-leakage losses on tip gap width, it is called tip desensitization. This paper presents a new method for tip desensitization: the passive blade tip injection. A low speed cascade wind tunnel is used for experimental investigations. Geometry of the turbine cascade is the up-scale of the tip section of a gas turbine rotor row. Three different gap widths in the range from 0.85% to 2.50% chord length are used. Total pressure, static pressure and flow angles are obtained by traversing a pneumatic five-hole probe about 0.3 axial chord lengths downstream of the turbine cascade. For investigations of the tip injection effect, a single blade of the cascade is modified by an injection channel. Based on experimental results, it is shown that the passive tip injection method decreases tip-leakage losses. At small tip gaps, this reduction can be rather significant. Finally, the positive influence of blade tip injection on tip-leakage losses is described by an analytical model based on the discharge coefficient.

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