Effects of Pressure-Side Winglet at an Elevation of Tip Surface on the Tip-Leakage Flow and Aerodynamic Loss Downstream of a Turbine Blade Equipped with Pressure-Side Squealer Tip

2016 ◽  
Vol 40 (10) ◽  
pp. 645-651
Author(s):  
Joo Hong Cheon ◽  
Sang Woo Lee
Keyword(s):  
Turbine Blade ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Aerodynamic Loss ◽  
Tip Leakage

An Investigation on Aerodynamics Loss Mechanism of Squealer Tips of a High Pressure Turbine Blade Using URANS

2016 ◽  
Author(s):  
Jin-sol Jung ◽  
Okey Kwon ◽  
Changmin Son
Keyword(s):  
High Pressure ◽  
Turbine Blade ◽  
Wall Thickness ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
High Pressure Turbine ◽  
Loss Mechanism ◽  
Tip Leakage

The flow leaking over the tip of a high pressure turbine blade generates significant aerodynamic losses as it mixes with the mainstream flow. This study investigates the effect of blade tip geometries on turbine performance with both steady RANS and unsteady URANS analyses. Five different squealer geometries for a high pressure turbine blade have been examined: squealer on pressure side, squealer on suction side, cavity squealer, cavity squealer with pressure side cutback, and cavity squealer with suction side cutback. With the case of the cavity squealer, three different squealer wall thickness are investigated for the wall thickness (w) of 1x, 2x and 4x of the tip gap (G). The unsteady flow analyses using CFX have been conducted to investigate unsteady characteristics of the tip leakage flow and its influence on turbine performances. Through the comparison between URANS analyses, detailed vortex and wake structures are identified and studied at different fidelities. It is found that the over tip leakage flow loss is affected by the tip suction side geometry rather than that of the pressure side geometry. The unsteady results have contributed to resolve the fundamentals of vortex structures and aerodynamic loss mechanisms in a high pressure turbine stage.

Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage

2003 ◽  
Author(s):  
Cengiz Camci ◽  
Debashis Dey ◽  
Levent Kavurmacioglu
Keyword(s):  
Total Pressure ◽  
Axial Flow ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Edge Zone ◽  
Tip Leakage ◽  
Partial Length

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

Effect of Turbine Blade Tip Cooling Configuration on Tip Leakage Flow and Heat Transfer

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Sergen Sakaoglu ◽  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

Abstract The pressure difference between suction and pressure sides of a turbine blade leads to tip leakage flow, which adversely affects the first-stage high-pressure (HP) turbine blade tip aerodynamics. In modern gas turbines, HP turbine blade tips are exposed to extreme thermal conditions requiring cooling. If the coolant jet directed into the blade tip gap cannot counter the leakage flow, it will simply add up to the pressure losses due to leakage. Therefore, the compromise between the aerodynamic loss and the gain in tip-cooling effectiveness must be optimized. In this paper, the effect of tip-cooling configuration on the turbine blade tip is investigated numerically from both aerodynamics and thermal aspects to determine the optimum configuration. Computations are performed using the tip cross section of GE-E3 HP turbine first-stage blade for squealer and flat tips, where the number, location, and diameter of holes are varied. The study presents a discussion on the overall loss coefficient, total pressure loss across the tip clearance, and variation in heat transfer on the blade tip. Increasing the coolant mass flow rate using more holes or by increasing the hole diameter results in a decrease in the area-averaged Nusselt number on the tip floor. Both aerodynamic and thermal response of squealer tips to the implementation of cooling holes is superior to their flat counterparts. Among the studied configurations, the squealer tip with a larger number of cooling holes located toward the pressure side is highlighted to have the best cooling performance.

Behavior of Tip Leakage Flow in an Axial Flow Compressor Rotor

2006 ◽  
Author(s):  
Yanhui Wu ◽  
Wuli Chu ◽  
Xingen Lu ◽  
Junqiang Zhu
Keyword(s):  
Boundary Layer ◽  
Vortex Breakdown ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Flow Compressor

The current paper reports on investigations with an aim to advance the understanding of the flow field near the casing of a small-scale high-speed axial flow compressor rotor. Steady three dimensional viscous flow calculations are applied to obtain flow fields at various operating conditions. To demonstrate the validity of the computation, the numerical results are first compared with available measured data. Then, the numerically obtained flow fields are analyzed to identify the behavior of tip leakage flow, and the mechanism of blockage generation arising from flow interactions between the tip clearance flow, the blade/casing wall boundary layers, and non-uniform main flow. The current investigation indicates that the “breakdown” of the tip leakage vortex occurs inside the rotor passage at the near stall condition. The vortex “breakdown” results in the low-energy fluid accumulating on the casing wall spreads out remarkably, which causes a sudden growth of the casing wall boundary layer having a large blockage effect. A low-velocity region develops along the tip clearance vortex at the near stall condition due to the vortex “breakdown”. As the mass flow rate is further decreased, this area builds up rapidly and moves upstream. This area prevents incoming flow from passing through the pressure side of the passage and forces the tip leakage flow to spill into the adjacent blade passage from the pressure side at the leading edge. It is found that the tip leakage flow exerts little influence on the development of the blade suction surface boundary layer even at the near stall condition.

Aerodynamic Investigation of the Tip Leakage Flow for Blades With Different Tip Squealer Geometries at Transonic Conditions

2009 ◽  
Author(s):  
Toma´sˇ Hofer ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Suction Side ◽  
Loss Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Gap Flow ◽  
Tip Gap Flow

Modern high pressure turbines operate at high velocity and high temperature conditions. The gap existing above a turbine rotor blade is responsible for an undesirable tip leakage flow. It is a source of high aerodynamic losses and high heat transfer rates. A better understanding of the tip flow behaviour is needed to provide a more efficient cooling design in this region. The objective of this paper is to investigate the tip leakage flow for a blade with two different squealer tips and film-cooling applied on the pressure side and through tip dust holes in a non-rotating, linear cascade arrangement. The experiments were performed in the VKI Light Piston Compression Tube facility, CT-2. The tip gap flow was investigated by oil flow visualisations and by wall static and total pressure measurements. Two geometries were tested — a full squealer and a partial suction side squealer. The measurements were performed in the blade tip region, including the squealer rim and on the corresponding end-wall for engine representative values of outlet Reynolds and Mach numbers. The main flow structures in the cavity were put in evidence. Positive influence of the coolant on the tip gap flow and on the aerodynamic losses was found for the full squealer tip case: increasing the coolant mass-flow increased the tip gap flow resistance. The flow through the clearance therefore slows down, the tip gap mass-flow and the heat transfer respectively decreases. No such effect of cooling was found in the case of the partial suction side squealer geometry. The absence of a pressure side squealer rim resulted in a totally different tip gap flow topology, indifferent to cooling. The influence of cooling on the overall mass-weighted thermodynamic loss coefficient, which takes into account the different energies of the mainstream and coolant flows was found marginal for both geometries. Finally the overall loss coefficient was found to be higher for the partial suction side squealer tip than for the full squealer tip.

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.

Effect of Turbine Blade Tip Cooling Configuration on Tip Leakage Flow and Heat Transfer

2019 ◽  
Author(s):  
Sergen Sakaoglu ◽  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

Abstract The pressure difference between suction and pressure sides of a turbine blade leads to the so-called phenomenon, the tip leakage flow, which most adversely affects the first-stage high-pressure (HP) turbine blade tip aerodynamics. In modern gas turbines, HP turbine blade tips are also exposed to extreme thermal conditions requiring the use of tip cooling. If the coolant jet directed into the blade tip gap cannot counter the leakage flow, it will simply add up to the pressure losses due to this leakage flow. Therefore, it is necessary to handle the design of tip cooling in such a way that the compromise between the aerodynamic loss and the gain in the tip cooling effectiveness is optimized. In this paper, the effect of tip cooling configuration on the turbine blade tip is investigated numerically both from the aerodynamics and thermal aspects in order to determine the optimum tip cooling configuration. The studies are carried out using the tip cross-section of General Electric E3 (Energy Efficient Engine) HP turbine first-stage blade for two different tip geometries, squealer tip and flat tip, where the number, location, and diameter of the cooling holes are varied. The study presents a discussion on the overall loss coefficient, the total pressure loss across the tip clearance, and the variation of heat transfer on the blade tip. The aerodynamic and heat transfer results are compared with the experimental data from literature. It is observed that increasing the coolant mass flow rate by using more holes or by increasing the hole diameter results in a decrease in the area-averaged Nusselt number on the tip floor, as expected. The findings show that both aerodynamic and thermal response of the squealer tips to the implementation of cooling holes is superior to their flat counterparts. Among the studied configurations, the squealer tip with larger number of cooling holes located towards the pressure side is highlighted as the configuration having the best cooling performance.

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