Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotor Blade ◽  
Tip Clearance ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5%, and 2.5% of the blade span with a flat tip were investigated, respectively, and the uniform and nonuniform inlet temperature profiles were taken as the inlet boundary conditions. A new method for heat transfer coefficient calculation recommended by Maffulli and He has been adopted. By solving the unsteady compressible Reynolds-averaged Navier–Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on the blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. Because it is possible for heat transfer coefficient distributions to be greatly different from heat flux distributions, it becomes of great concern to combine both of them in consideration of hot streak migration. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2013 ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Stokes Equations ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5% and 2.5% of the blade span with a flat tip were investigated respectively, and the uniform and non-uniform inlet temperature profiles were taken as the inlet boundary conditions. By solving the unsteady compressible Reynolds-averaged Navier-Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Effects of Inlet Swirl on Hot Streak Migration Across Tip Clearance and Heat Transfer on Rotor Blade Tip

2015 ◽  
Author(s):  
Zhaofang Liu ◽  
Zhiduo Wang ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Heat Load ◽  
Leading Edge ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Inlet Swirl ◽  
Blade Tip ◽  
Hot Streak

This paper presents an investigation on the hot streak migration across tip clearance and heat transfer on blade tip in a high pressure (HP) gas turbine with different inlet swirl directions and clocking positions. The geometry is taken from the first stage of GE-E3 turbine engine. Two swirl directions (positive and negative) and two circumferential clocking positions (aligning with S1 nozzle leading edge and mid passage) for inlet hot streak and swirl have been employed and investigated, respectively. Two cases with only hot streak at different inlet circumferential positions are adopted as the baseline in this study. By solving the unsteady compressible Reynolds-averaged Navier-Stokes equations, the time dependent solutions were obtained. The results indicate that the influence of inlet swirl on pressure distribution focuses on the suction side. Positive swirl attracts more hot fluid to the upper endwall, when it aligns with nozzle stator leading edge. Because of the squeezing mechanism between positive swirl and leakage flow, the heat transfer on rotor blade tip is more uniform. While negative swirl increases tip leakage flow and the heat load at the first half on tip surface. In all cases with swirl, the heat load at the second half on blade tip is effectively reduced, which is good for cooling rotor blade tip. If the stator is cooled effectively, inlet positive swirl aligning with nozzle vane leading edge will be the best choice for protecting rotor blade tip. By comparing with the results of previous literature, it is concluded that whatever arrangement the blade rows locate, the swirl direction which is opposite to the leakage flow should be chosen for protecting not only blade surface but also blade tip when the inlet swirl exists.

The Effect of External Casing Impingement Cooling Manifold Standoff Distance on Casing Contraction for Thermal Control of Blade Tip Clearance

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Myeonggeun Choi ◽  
David R. H. Gillespie ◽  
Leo V. Lewis
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Control ◽  
Tip Clearance ◽  
Standoff Distance ◽  
Impingement Cooling ◽  
Assembly Tolerance ◽  
Blade Tip ◽  
Blade Tip Clearance

Thermal closure of the engine casing is widely used to minimize undesirable blade tip leakage flows thus improving jet engine performance. This may be achieved using an impingement cooling scheme on the external casing wall, provided by manifolds attached to the outside of the engine. The assembly tolerance of these components leads to variation in the standoff distance between the manifold and the casing, and its effects on casing contraction must be understood to allow build tolerance to be specified. For cooling arrangements with promising performance, the variation in closure with standoff distance of z/d = 1–6 were investigated through a mixture of extensive numerical modeling and experimental validation. A cooling manifold, typical of that adopted by several engine companies, incorporating three different arrays of short cooling holes (chosen from previous study by Choi et al. (2016, “The Relative Performance of External Casing Impingement Cooling Arrangements for Thermal Control of Blade Tip Clearance,” ASME J. Turbomach., 138(3), p. 031005.)) and thermal control dummy flanges were considered. Typical contractions of 0.5–2.2 mm are achieved from the 0.02–0.35 kg/s of the current casing cooling flows. The variation in heat transfer coefficient observed with standoff distance is much lower for the sparse array investigated compared to previous designs employing arrays typical of blade cooling configurations. The reason for this is explained through interrogation of the local flow field and resultant heat transfer coefficient. This implies that acceptable control of the circumferential uniformity of case cooling can be achieved with relatively large assembly tolerance of the manifold relative to the casing.

scholarly journals Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade

2000 ◽  
Author(s):  
Gm S. Azad ◽  
Je-Chin Han ◽  
Robert J. Boyle
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Static Pressure ◽  
Cavity Surface ◽  
Edge Region ◽  
Blade Tip ◽  
The Heat Transfer Coefficient

Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modern first stage gas turbine rotor blade with a blade tip profile of a GE-E3 aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1×106. A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. The heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1% case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.

scholarly journals Heat Transfer and Pressure Distributions on a Gas Turbine Blade Tip

2000 ◽  
Vol 122 (4) ◽  
pp. 717-724 ◽  
Author(s):  
Gm. S. Azad ◽  
Je-Chin Han ◽  
Shuye Teng ◽  
Robert J. Boyle
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbulence Intensity ◽  
Rotor Blade ◽  
Static Pressure ◽  
Pressure Distributions ◽  
Blade Tip

Heat transfer coefficient and static pressure distributions are experimentally investigated on a gas turbine blade tip in a five-bladed stationary linear cascade. The blade is a two-dimensional model of a first-stage gas turbine rotor blade with a blade tip profile of a GE-E3 aircraft gas turbine engine rotor blade. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and exit Reynolds number based on axial chord of 1.1×106. The middle 3-blade has a variable tip gap clearance. All measurements are made at three different tip gap clearances of about 1, 1.5, and 2.5 percent of the blade span. Heat transfer measurements are also made at two different turbulence intensity levels of 6.1 and 9.7 percent at the cascade inlet. Static pressure measurements are made in the midspan and the near-tip regions as well as on the shroud surface, opposite the blade tip surface. Detailed heat transfer coefficient distributions on the plane tip surface are measured using a transient liquid crystal technique. Results show various regions of high and low heat transfer coefficient on the tip surface. Tip clearance has a significant influence on local tip heat transfer coefficient distribution. Heat transfer coefficient also increases about 15–20 percent along the leakage flow path at higher turbulence intensity level of 9.7 over 6.1 percent. [S0889-504X(00)00404-9]

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

2003 ◽  
Author(s):  
Arun K. Saha ◽  
Sumanta Acharya ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Average Heat Transfer Coefficient ◽  
Tip Leakage Flow ◽  
Average Heat ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.

Heat Transfer Coefficient and Film-Cooling Effectiveness on a Gas Turbine Blade Tip

2002 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Film Cooling ◽  
Rotor Blade ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blade Tip

The detailed distributions of heat transfer coefficient and film cooling effectiveness on a gas turbine blade tip were measured using a hue detection based transient liquid crystal technique. Tests were performed on a five-bladed linear cascade with blow down facility. The blade was a 2-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The Reynolds number based on cascade exit velocity and axial chord length was 1.1 × 106 and the total turning angle of the blade was 97.7°. The overall pressure ratio was 1.32 and the inlet and exit Mach number were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. The blade model was equipped with a single row of film cooling holes at both the tip portion along the camber line and near the tip region of the pressure-side. All measurements were made at the three different tip gap clearances of 1%, 1.5%, and 2.5% of blade span and the three blowing ratios of 0.5, 1.0, and 2.0. Results showed that, in general, heat transfer coefficient and film effectiveness increased with increasing tip gap clearance. As blowing ratio increased, heat transfer coefficient decreased, while film effectiveness increased. Results also showed that adding pressure-side coolant injection would further decrease blade tip heat transfer coefficient but increase film effectiveness.

Effect of casing purge flow on heat transfer and cooling performance of blade squealer tip for a gas turbine stage

2021 ◽  
pp. 095765092110403
Author(s):  
Shijie Jiang ◽  
Zhigang Li ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Local Cooling ◽  
Cold Air ◽  
Blowing Ratio ◽  
Purge Flow ◽  
Blade Tip

The first stage of GE-E3 turbine is employed to investigate effect of casing purge flow upstream rotor blade tip. Three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations and standard k-ω model are solved to obtain tip heat transfer simulations. The results reveal that: heat transfer coefficient of blade tip surface can be significantly reduced when casing purge flow is set. Tip averaged heat transfer coefficient of cases with and without swirly velocity casing purge flow decrease 3.5% and 3.4% compared with the case without casing purge flow. Compared with case which blowing ratio equals to 0.5, it can be found that averaged tip heat transfer coefficient of cases which blowing ratio equals to 1.0 and 1.5 decrease 2.3% and 1.8%, respectively. Setting blowing ratio as 1.0 can best cool tip surface without wasting cold air resources. Increasing rotating speed can induce cold air entering tip trailing region and improve local cooling effect. Flow structure inside the tip clearance are also revealed and discussed.

Detailed Heat Transfer Coefficient Distributions on a Large-Scale Gas Turbine Blade Tip

2000 ◽  
Vol 123 (4) ◽  
pp. 803-809 ◽  
Author(s):  
Shuye Teng ◽  
Je-Chin Han ◽  
G. M. S. Azad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Wind Tunnel ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Large Scale ◽  
Tip Clearance ◽  
Low Speed ◽  
Blade Tip ◽  
Low Speed Wind Tunnel

Measurements of detailed heat transfer coefficient distributions on a turbine blade tip were performed in a large-scale, low-speed wind tunnel facility. Tests were made on a five-blade linear cascade. The low-speed wind tunnel is designed to accommodate the 107.49 deg turn of the blade cascade. The mainstream Reynolds number based on cascade exit velocity was 5.3×105. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 or 0.1. The central blade had a variable tip gap clearance. Measurements were made at three different tip gap clearances of about 1.1 percent, 2.1 percent, and 3 percent of the blade span. Static pressure distributions were measured in the blade mid-span and on the shroud surface. Detailed heat transfer coefficient distributions were measured on the blade tip surface using a transient liquid crystal technique. Results show that reduced tip clearance leads to reduced heat transfer coefficient over the blade tip surface. Results also show that reduced tip clearance tends to weaken the unsteady wake effect on blade tip heat transfer.

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