Effects of Inlet Temperature Uniformity and Nonuniformity on the Tip Leakage Flow and Rotor Blade Tip and Casing Heat Transfer Characteristics

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Md. Hamidur Rahman ◽  
Sung In Kim ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Turbine Inlet Temperature ◽  
Turbine Engine ◽  
Tip Leakage ◽  
Turbine Inlet ◽  
Blade Tip

High thermal load appears at the blade tip and casing of a gas turbine engine. It becomes a significant design challenge to protect the turbine materials from this severe situation. As a result of geometric complexity and experimental limitations, computational fluid dynamics tools have been used to predict blade tip leakage flow aerodynamics and heat transfer at typical engine operating conditions. In this paper, the effect of turbine inlet temperature on the tip leakage flow structure and heat transfer has been studied numerically. Uniform low (444 K) and high (800 K) inlet temperatures and nonuniform (parabolic) temperature profiles have been considered at a fixed rotor rotation speed (9500 rpm). The results showed that the change of flow properties at a higher inlet temperature yields significant variations in the leakage flow aerodynamics and heat transfer relative to the lower inlet temperature condition. Aerodynamic behavior of the tip leakage flow varies significantly with the distortion of turbine inlet temperature. For more realistic inlet condition, the velocity range is insignificant at all time instants. At a high inlet temperature, reverse secondary flow is strongly opposed by the tip leakage flow and the heat transfer fluctuations are reduced greatly.

Effect of Turbine Inlet Temperature on Blade Tip Leakage Flow and Heat Transfer

2009 ◽  
Author(s):  
Sung In Kim ◽  
Md Hamidur Rahman ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Turbine Inlet Temperature ◽  
Maximum Heat ◽  
Tip Leakage ◽  
Turbine Inlet ◽  
Blade Tip

One of the most critical gas turbine engine components, rotor blade tip and casing, are exposed to high thermal load. It becomes a significant design challenge to protect the turbine materials from this severe situation. As a result of geometric complexity and experimental limitations, Computational Fluid Dynamics (CFD) tools have been used to predict blade tip leakage flow aerodynamics and heat transfer at typical engine operating conditions. In this paper, the effect of turbine inlet temperature on the tip leakage flow structure and heat transfer has been studied numerically. Uniform low (LTIT: 444 K) and high (HTIT: 800 K) turbine inlet temperature have been considered. The results showed the higher turbine inlet temperature yields the higher velocity and temperature variations in the leakage flow aerodynamics and heat transfer. For a given turbine geometry and on-design operating conditions, the turbine power output can be increased by 1.48 times, when the turbine inlet temperature increases 1.80 times. Whereas the averaged heat fluxes on the casing and the blade tip become 2.71 and 2.82 times larger, respectively. Therefore, about 2.8 times larger cooling capacity is required to keep the same turbine material temperature. Furthermore, the maximum heat flux on the blade tip of high turbine inlet temperature case reaches up to 3.348 times larger than that of LTIT case. The effect of the interaction of stator and rotor on heat transfer features is also explored using unsteady simulations.

Tip Leakage Flow and Heat Transfer Characteristics on Rotor Casing and Blade Tip in an Axial Gas Turbine Engine: Steady Analysis

2008 ◽  
Author(s):  
Md Hamidur Rahman ◽  
Sung In Kim ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Heat Transfer Characteristics ◽  
Turbine Engine ◽  
Tip Leakage ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Blade Tip

Steady simulations have been performed to investigate tip leakage flow and heat transfer characteristics on the casing and rotor blade tip in a single stage turbine engine. A turbine stage of stator and rotor was modeled with a pressure ratio of 3.2. The predicted isentropic Mach number and adiabatic wall temperature on the casing showed good agreement with available experimental data. The effects of tip clearance height and rotor rotational speed on the blade tip and casing heat transfer characteristics are mainly considered. It is observed that the tip leakage flow structure is highly dependent on the height of the tip gap as well as speeds of the rotor blade. In all cases, flow separates just around the corner of the pressure side of the blade tip. The region of recirculating flow increases with the increase of the clearance height. Then the flow reattaches on the tip surface near the suction side beyond the flow separation. This flow reattachment enhances surface heat transfer. The leakage flow interaction with the reverse cross flow, induced by relative casing motion, is found to have significant effect on the blade tip and casing heat transfer distribution. Critical region of high heat transfer on the casing exists near the blade tip leading edge and along the pressure side edge at all clearance height. Whereas, at high speed rotation, it tends to move towards the trailing edge due to the change of inflow angle.

Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

2008 ◽  
Author(s):  
Dianliang Yang ◽  
Xiaobing Yu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Relative Motion ◽  
Turbulence Models ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blade Height ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Rotation ◽  
Blade Tip

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.

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.

scholarly journals TIP LEAKAGE FLOW AND HEAT TRANSFER ON TURBINE STAGE TIP AND CASING: EFFECT OF UNSTEADY STATOR–ROTOR INTERACTIONS

2014 ◽  
Vol 11 (04) ◽  
pp. 1350058 ◽  
Author(s):  
MD HAMIDUR RAHMAN ◽  
SUNG IN KIM ◽  
IBRAHIM HASSAN
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Structures ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Tip

Unsteady simulations were performed to investigate time dependent behaviors of the leakage flow structures and heat transfer on the rotor blade tip and casing in a single stage gas turbine engine. This paper mainly illustrates the unsteady nature of the leakage flow and heat transfer, particularly, that caused by the stator–rotor interactions. In order to obtain time-accurate results, the effects of varying the number of time steps, sub iterations, and the number of vane passing periods was firstly examined. The effect of tip clearance height and rotor speeds was also examined. The results showed periodic patterns of the tip leakage flow and heat transfer rate distribution for each vane passing. The relative position of the vane and vane trailing edge shock with respect to time alters the flow conditions in the rotor domain, and results in significant variations in the tip leakage flow structures and heat transfer rate distributions. It is observed that the trailing edge shock phenomenon results in a critical heat transfer region on the blade tip and casing. Consequently, the turbine blade tip and casing are subjected to large fluctuations of Nusselt number (about Nu = 2000 to 6000 and about Nu = 1000 to 10000, respectively) at a high frequency (coinciding with the rotor speed).

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.

Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Dianliang Yang ◽  
Xiaobing Yu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Relative Motion ◽  
Turbulence Models ◽  
Groove Depth ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Tip ◽  
Richardson Extrapolation Method

Numerical analysis was applied to investigate the effect of rotation on the blade tip leakage flow and heat transfer. Flows around both flat and squealer tips at the first stage rotor blade of GE E3 high-pressure turbine were studied. The tip gap and squealer groove depth were specified as 1% and 2% of the blade height, respectively. The heat transfer coefficient on the tip surface was obtained by using different turbulence models and compared with the experimental data. The grid independence study was also carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: (1) the blade domain is rotating and the shroud is stationary; (2) the blade domain is stationary and the shroud is rotating; and (3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force, and the Coriolis force can be investigated, respectively. By comparing the results of the three cases discussed, it is concluded that the main effect of the rotation on the tip leakage flow and heat transfer resulted from the relative motion of the shroud, especially for the squealer tip blade.

The Influence of Rotating Speed on Film Cooling Characteristics on GE-E3 Blade Tip With Different Tip Configurations

2009 ◽  
Author(s):  
D. H. Zhang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Rotating Speed ◽  
Tip Leakage ◽  
Blowing Ratio ◽  
Blade Tip ◽  
Cooling Air

The film cooling phenomenon of flat tip (with or without a trench) and squealer tip on GE-E3 blade in rotating state was numerically studied. The effect of tip configuration, rotating speed and blowing ratio on the blade tip flow and cooling performance was revealed. It was found that the squealer tip and the flat tip with trenched hole have comparability in configuration: both have a cavity at the end of the film hole. So the coolant momentum and the tip leakage flow velocity in the cavity are decreased, which contributes to the improvement of the cooling effect. Because of the bigger cavity of the squealer tip than that of the flat tip with trenched hole, the cooling air and the leakage flow mix adequately in the cavity, the squealer tip can get the highest cooling effectiveness and the lowest heat transfer coefficient value both in stationary and rotating state, and the flat tip with trenched hole follows. With the increase of rotating speed, for all the three configurations, the area-averaged cooling effectiveness decreases and the area-averaged heat transfer coefficient increases. At the same time, the tip leakage flow entraps the cooling air moving toward the leading edge. And with the increase of the blowing ratio, for all the configurations, the area-averaged cooling effectiveness increases while the area-averaged heat transfer coefficients decreases.

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