Numerical Investigations of Flow and Film Cooling with Endwall Contouring and Blade Tip Ejection under Rotating Turbine Conditions

An effort is made to numerically study the impact of rotating turbine conditions on the aerodynamic performance, film cooling effectiveness and heat transfer with the application of the endwall contouring and blade tip ejection. For this purpose, the three-stage HP turbine research facility at the Turbomachinery Performance and Flow Research Laboratory (TPFL), Texas A&M University, was newly designed and equipped. Using the geometry of this three-stage research turbine rig, comprehensive numerical simulations are performed to systematically study the impact of the rotation from the perspectives of both aerodynamics and heat transfer.

Introducing endwall contouring has become a promising means to reduce the secondary flow losses. Thus TPFL developed a physics-based method which enables researchers and engineers to design endwall contours for any arbitrary blade types regardless of the blade loading, degree of reaction, stage load and flow coefficients. Using this approach, TPFL designed the new endwall contouring which was implemented on the platform of both the first-stage and second-stage rotors. The rotation impacts on the aerodynamics performance due to the endwall contouring were numerically studied using four different rotational speeds namely, 2000 rpm, 2400 rpm, 2600 rpm and 3000 rpm. Meanwhile, the influence on film cooling effectiveness and heat transfer caused by the endwall contouring was investigated for the first-stage rotor. Different purge-to-mainstream mass flow ratios of MFR = 0.5%, 1.0% and 1.5% were taken into account at the design rotational speed of 3000rpm. The effect of rotational speed (2400rpm, 2550rpm and 3000rpm) was investigated at typical MFR=1.0%.

To investigate the flow characteristics and film cooling at high pressure turbine blade tips, four different rotor-blade tip configurations are designed and studied at TPFL: the plane and squealer tips with tip hole cooling and the plane and squealer tips with pressure-side-edge compound angle hole cooling. Seven perpendicular holes that are evenly distributed along the camber line are used for the tip hole cooling, whilst eight compound-angle holes for the pressure-side-edge cooling. The coolant was ejected through the cooling holes with low, medium and high global blowing ratios at 3000 rpm to study the impact of the blowing ratio on both the cooling effectiveness and heat transfer. Effects of rotation on the cooling effectiveness and heat transfer were calculated at the rotational speeds of 2000rpm, 2550 rpm, and 3000 rpm.