Huitao Yang

Film-Cooling Effectiveness on Squealer Cavity and Rim Walls of Gas-Turbine Blade Tip

Effects of shaped holes on the tip pressure side, coolant jet impingement on the pressure side squealer rim from tip holes, and varying blowing ratios for a squealer blade tip were examined on film-cooling effectiveness. The film-cooling effectiveness distributions were measured on the blade tip, near tip pressure side, and the inner pressure side rim wall using pressure-sensitive-paint technique. Air and nitrogen gas were used as the film-cooling gases, and the oxygen concentration distribution for each case was measured. The film-cooling effectiveness information was obtained from the difference of the oxygen concentration between air and nitrogen gas cases by applying the mass-transfer analogy. The internal coolant-supply passages of the squealer tipped blade were modeled similar to those in the GE-E3 rotor blade with two separate serpentine loops supplying coolant to the film-cooling holes. A row of compound angled cylindrical film-cooling holes was arranged along the camber line on the tip and another row of compound angled shaped film-cooling holes was arranged along the span of the pressure side just below the tip. The average blowing ratio of the cooling gas was controlled to be 0.5,1.0, and 2.0. Tests were conducted in a five-bladed linear cascade in a blowdown facility with a tip gap clearance of 1.5%, The freestream Reynolds number, based on the axial chord length and the exit velocity, was 1.48 x 10 6 , and the inlet and the exit Mach number were 0.23 and 0.65, respectively. Turbulence intensity level at the cascade inlet was 9.7%. Numerical predictions were also performed using Fluent to simulate the experiment at the same inlet flow conditions. Predictions for film cooling are presented. Results show a good correlation between experimental and predicted data. The shape and location of the film-cooling holes along with varying blowing ratios can have significant effects on film-cooling performance.

Film-Cooling Effectiveness on Squealer Rim Walls and Squealer Cavity Floor of a Gas Turbine Blade Tip Using Pressure Sensitive Paint

Effects of shaped holes on the tip pressure side, coolant jet impingement on the pressure side squealer rim from tip holes and varying blowing ratios for a squealer blade tip were examined on film-cooling effectiveness. The film-cooling effectiveness distributions were measured on the blade tip, near tip pressure side and the inner pressure side rim wall using Pressure Sensitive Paint technique. Air and nitrogen gas were used as the film cooling gases and the oxygen concentration distribution for each case was measured. The film cooling effectiveness information was obtained from the difference of the oxygen concentration between air and nitrogen gas cases by applying the mass transfer analogy. The internal coolant-supply passages of the squealer tipped blade were modeled similar to those in the GE-E3 rotor blade with two separate serpentine loops supplying coolant to the film cooling holes. A row of compound angled cylindrical film cooling holes was arranged along the camber line on the tip and another row of compound angled shaped film cooling holes was arranged along the span of the pressure side just below the tip. The average blowing ratio of the cooling gas was controlled to be 0.5, 1.0 and 2.0. Tests were conducted in a five-bladed linear cascade in a blow down facility with a tip gap clearance of 1.5%. The free stream Reynolds number, based on the axial chord length and the exit velocity, was 1,138,000 and the inlet and the exit Mach number were 0.25 and 0.6, respectively. Turbulence intensity level at the cascade inlet was 9.7%. Numerical predictions were also performed using Fluent to simulate the experiment at the same inlet flow conditions. Predictions for film cooling are presented. Results show a good correlation between experimental and predicted data. The shape and location of the film cooling holes along with varying blowing ratios can have significant effects on film-cooling performance.Copyright

Film-Cooling Prediction on Turbine Blade Tip with Various Film Hole Configurations

Different film hole arrangements on the plane and squealer tips of a turbine blade are investigated using a Reynolds stress turbulence model and nonequilibrium wall function. The three film hole configurations considered are 1) the camber arrangement, where the film-cooling holes are located on the mid-camber line of the tips; 2) the upstream arrangement, where the film holes are located upstream of the tip leakage flow and high heat transfer region; and 3) the two-rows arrangement, which is a combination of the camber and upstream arrangements. Calculations were performed first for the nonrotating cases under low inlet/outlet pressure ratio conditions with three different blowing ratios. The predicted heat transfer coefficients are in good agreement with the experimental data, but the film-cooling effectiveness is somewhat overpredicted downstream of the film holes. Simulations were then performed for the nonrotating and rotating camber line film hole configuration under high inlet/outlet pressure ratio conditions, which are close to engine conditions. It is found that the rotation decreases the plane tip film-cooling effectiveness but only slightly affects the squealer tip film cooling. However, the rotation significantly increases heat transfer coefficient on the shrouds.

Turbine Rotor with Various Tip Configurations Flow and Heat Transfer Prediction

A numerical study is performed to simulate the leakage flow and heat transfer on a flat tip, a double squealer tip, and a single suction-side squealer tip of a scaled up General Electric-E 3 blade. The simulations for a nonrotating blade at a pressure ratio of 1.2 are in reasonable agreement with the experimental data on the blade tip and suction side, but the heat transfer coefficients were overpredicted on the pressure side. Numerical simulations were then performed for nonrotating and rotating blades under high-temperature, high-pressure ratio, and high Mach number conditions to investigate the blade tip leakage flow and heat transfer characteristics under more realistic engine operating conditions

Numerical Study of a Rotating Blade Platform With Film Cooling From Cavity Purge Flow in a 1-1/2 Turbine Stage

Numerical simulations were performed to predict the effect of cavity purge flow on the rotating blade platform in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. Simulations were carried out with a sliding mesh for the rotor under three rotating speeds (2000, 2550 and 3000 rpm) and three purge-to-mainstream mass flow ratios (0.5%, 1% and 1.5%) to investigate the effects of rotating speed and coolant purging rate on the rotating blade platform film cooling. The adiabatic film cooling effectiveness was evaluated using the adiabatic wall temperatures with and without coolant purging to examine the true effect of coolant protection. The film cooling effectiveness increases with increasing coolant purging flow ratio from 0.5% to 1.5% of mainstream. Higher rotating speed also enhances film cooling effectiveness for the range of rotating speed considered. The predicted laterally averaged adiabatic film cooling effectiveness is in good agreement with the corresponding experiment data except for the platform leading edge region. However, the detailed effectiveness distribution on the platform is not well predicted by this study. In addition, the detailed instantaneous film cooling effectiveness and the associated heat transfer coefficients for four different time phases are also reported.Copyright

Film-Cooling Prediction on Rotor Blade Leading Edge in 1-1/2 Turbine Stage

Numerical simulations have been performed to predict the film-cooling effectiveness and the associated heat transfer coefficient on the leading edge of a rotating blade in a 1-1/2 turbine stage. The Reynolds stress turbulence model together with the nonequilibrium wall function is employed in the simulation. A sliding grid is used for the rotor domain, and an interface technique is employed to exchange the information between stator and rotor domains. Simulations are carried out for both the design and the off-design conditions to investigate the effects of the stator-rotor interaction on the film-cooling characteristics. The unsteady characteristics of the heat transfer coefficient and film-cooling effectiveness at various rotating speeds are also investigated. With increasing rotating speed, the tilt stagnation line on the leading edge of a rotor moves from the pressure side to the suction side, and the instantaneous coolant streamlines shift from the suction side to the pressure side. This trend is supported by the experimental results. In addition, the detailed instantaneous heat transfer coefficient and film-cooling effectiveness at various time phases, as well as different rotating speeds, are also reported.

Numerical Prediction of Film Cooling and Heat Transfer on the Leading Edge of a Rotating Blade With Two Rows Holes in a 1-1/2 Turbine Stage at Design and Off Design Conditions

Numerical simulations were performed to predict the film cooling effectiveness and the associated heat transfer coefficient on the leading edge of a rotating blade in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. Simulations were performed for both the design and off-design conditions to investigate the effects of blade rotation on the leading edge film cooling effectiveness and heat transfer coefficient distributions. It was found that the tilt stagnation line on the leading edge of rotor moves from the pressure side to the suction side, and the instantaneous coolant streamlines shift from the suction side to the pressure side with increasing rotating speed. This trend was supported by the experimental results. The result also showed that the heat transfer coefficient increases, but film cooling effectiveness decreases with increasing rotating speed. In addition, the unsteady characteristics of the film cooling and heat transfer at different time phases, as well as different rotating speeds, were also reported.Copyright

Flow And Heat Transfer Prediction On Turbine Rotor With Various Tip Configurations

Calculations were performed first for a stationary blade at a pressure ratio of 1.2 and compared with the available experimental data. The predicted heat transfer coefficients are in reasonable agreement with the experimental data on the blade tip and suction side, but the heat transfer coefficients were overpredicted on the pressure side. Numerical simulations were then performed for stationary and rotating blades under high temperature, high pressure ratio, and high Mach number conditions to investigate the blade tip heat transfer characteristics under more realistic engine operating conditions. A systematic comparison of various tip configurations were made to facilitate a more detailed understanding of the leakage flow structures around the blade tip. The simulation results show that the heat transfer coefficient decreases with increasing squealer cavity depth, but the shallow squealer cavity is the most effective configuration to reduce the heat load in the bl ade tip region. In general, rotation produced a somewhat stronger tip leakage flow and a slight increase of the area averaged Stanton number on the blade tip region.

Numerical Prediction of Film Cooling and Heat Transfer on the Leading Edge of a Rotating Blade in a 1-1/2 Turbine Stage

In modern gas turbines, the blade leading edge region is one area that experiences high heat transfer due to the stagnation flow. Many cooling techniques have been applied to blades, so they can withstand these high heat loads; one of the common methods in cooling turbine blades is to apply film cooling. In the present study, numerical simulations were performed to predict the film cooling effectiveness and heat transfer coefficient on the leading edge of a rotating blade in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. In addition, the unsteady characteristics of the film cooling and heat transfer at different time phases during a passing period were also investigated.Copyright