Effective internal and external cooling of airfoils is key to maintaining component life for efficient gas turbines. Cooling designs have spanned the range from simple internal convective channels to more advanced double-walls with shaped film-cooling holes. This paper describes the development of an internal and external cooling concept for a state-of-the-art cooled turbine blade. These cooling concepts are based on a review of literature and patents, as well as, interactions with academic and industry turbine cooling experts. The cooling configuration selected and described in this paper is referred to as the “baseline” design, since this design will simultaneously be tested with other more advanced blade cooling designs in a rotating turbine test facility using a “rainbow turbine wheel” configuration. For the baseline design, the leading edge is cooled by internal jet impingement and showerhead film cooling. The midchord region of the blade contains a three-pass serpentine passage with internal discrete V-shaped trip strips to enhance the internal heat transfer coefficient (HTC). The film cooling along the midchord of the blade uses multiple rows of shaped diffusion holes. The trailing edge is internally cooled using jet impingement and externally film cooled through partitioned cuts on the pressure side of the blade.

A computational study based on unsteady Reynolds-averaged Navier–Stokes that resolves the gas–liquid interface was performed to examine the unsteady multiphase flow in a liquid-ring pump as a function of its inlet pressure (10, 40, and 80 kPa) and its impeller's rotational speed (1150, 1450, and 1750 rpm). Results obtained show the shape of the liquid ring to play a critical role in creating the expansion ratio needed to draw air into the pump and the compression ratio needed to expel air out of the pump. The dominant processes that determine the shape of the liquid ring was found to be the centrifugal force from rotation, the acceleration and deceleration due to the difference in pressure at the pump's inlet and outlet, and the eccentricity of the impeller relative to the pump's housing. Results are presented to show how the rotational speed of the impeller and the pressure at the pump's inlet affect the nature of the multiphase flow in the pump as well as the pump's effectiveness in creating a vacuum. The effects of heat transfer on the gas phase during the compression and expansion processes were found to be approximated well by polytropic processes. This computational study was validated by comparing computed with measured volumetric flowrates ingested through the suction port and the torque exerted on the pump's impeller.

Cooling of turbine components that come in contact with the hot gases strongly affects the turbine's efficiency and service life. Designing effective and efficient cooling configurations requires detailed understanding on how geometry and operating conditions affect the way coolant cools the turbine materials. Experimental measurements that can reveal such information are difficult and costly to obtain because gas turbines operate at high temperatures (up to 2000 K), high pressures (30+ bar), and the dimensions of many key features in the cooling configurations are small (millimeters or smaller). This paper presents a method that enables experiments to be conducted at near room temperatures, near atmospheric pressures, and using scaled-up geometries to reveal the temperature and heat-flux distributions within turbine materials as if the experiments were conducted under engine operating conditions. The method is demonstrated by performing conjugate computational fluid dynamics (CFD) analyses on two test problems. Both problems involve a thermal barrier coating (TBC)-coated flat plate exposed to a hot-gas environment on one side and coolant flow on the other. In one problem, the heat transfer on the coolant side is enhanced by inclined ribs. In the other, it is enhanced by an array of pin fins. This conjugate CFD study is based on 3D steady Reynolds-averaged Navier–Stokes (RANS) closed by the shear-stress-transport turbulence model for the fluid phase and the Fourier law for the solid phase. Results obtained show that, of the dimensionless parameters that are important to this problem, it is the Biot number that dominates. This study also shows that for two geometrically similar configurations, if the Biot number distributions on the corresponding hot-gas and coolant sides are nearly matched, then the magnitude and contours of the nondimensional temperature and heat-flux distributions in the material will be nearly the same for the two configurations—even though the operating temperatures and pressures differ considerably. Thus, experimental measurements of temperature and heat-flux distributions within turbine materials that are obtained under “laboratory” conditions could be scaled up to provide meaningful results under “engine” relevant conditions.

Computational fluid dynamics (CFD) has been unable to reliably predict aeration and drag torque in clutches. In this study, a CFD method was developed to reliably predict the onset of aeration and drag torque as a function of the clutch's rotational speed. This study showed that though the oil and air behave as if they are incompressible at steady-state, the formulation must account for the compressible nature of the gas and the unsteady processes that occur before reaching steady-state. This study also showed that the dynamic nature of the contact angle between the oil and the stationary disk must be accounted for to predict drag torque and aeration as a function of rotational speed, and a model of the dynamic-contact angle was developed.

Counter-rotating vortices, formed by the interaction of film-cooling jets and the hot gas flow, adversely affect the performance of conventional film-cooling designs. Downstream vortex generators have been shown to improve cooling effectiveness by mitigating the effects of the counter-rotating vortices and by deflecting the cooling jet laterally. In this study, computational and experimental methods were used to examine how cylindrical film-cooling holes (D = 3.2 mm, L/D = 6, p/D = 3, α = 30 deg) with and without downstream vortex generators perform when the coolant supply channel is perpendicular to the direction of the hot gas. For this study, the hot gas had a temperature of 650 K and an average Mach number of 0.23. The hot-gas-to-coolant temperature ratio was 1.9, and two blowing ratios (0.75 and 1.0) were studied. Results from the computational fluid dynamics study show how crossflow affects the interaction between the film-cooling jet and hot gas flow with and without downstream vortex generators. The experimental measurements were based on infrared thermography in a conjugate heat transfer environment. Results were obtained for film-cooling performance in terms of overall effectiveness, film effectiveness, and local heat transfer coefficients. The downstream vortex generators can increase the laterally averaged effectiveness by a factor of 1.5 relative to cylindrical holes, but this higher performance is restricted to low crossflow velocities and higher blowing ratios.

Downstream vortex generators that involve a pair of rectangular plates arranged in an open V-shape placed just downstream of each film-cooling hole were shown to create flow and vortical structures that entrain lifted film-cooling flow back to the surface and increase its lateral spreading on the surface (GT2020–14317). In this study, computations and measurements were performed to examine the flow mechanisms this vortex generator induces to improve film-cooling effectiveness of a flat plate with the cooling flow emanating from one row of inclined holes. Parameters studied include blowing ratio (BR = 0.75 and 1.0) and temperature ratio (TR = 1.07 and 1.9). The computational study is based on steady Reynolds-averaged Navier–Stokes (RANS) closed by the shear-stress transport (SST) turbulence model with and without conjugate analysis. The experimental study was conducted by using a conjugate heat transfer test rig with a plenum, where cooling flow is introduced. Measurements made include velocity and temperature profiles upstream and downstream of the film-cooling holes as well as the temperature at several locations on the hot and cold sides of the film-cooled flat plate. The computational study was validated by comparing computed results with those from measurements at BR = 0.75 and 1.0 and TR = 1.9. Computational and experimental results are presented to show the effects of BR and TR on the flow structures and how those structures improve the effectiveness of film cooling with and without the downstream vortex generators and with and without conjugate heat transfer.