Principal Investigator: S. Ekkad and S. Acharya
This award is to support an investigation of the fundamental issues pertaining to blade tip aerodynamics and heat transfer, and to provide guidance to the gas turbine industry for improved blade-tip cooling strategies that will aid in improving blade life and reduce maintenance requirements for gas turbine engines. This is a GOALI proposal submitted jointly by Louisiana State University and General Electric Company. General Electric will be primarily responsible for the technology transfer and in testing, using industry-standard procedures, of improved designs and concepts resulting from the proposed research at LSU.
The experimental study will be conducted on a five blade linear cascade with high-pressure compressed air flow facility capable of providing engine representative flow conditions. An engine typical PT,rel,inlet/PS,exit will be simulated to ensure real pressure-driven leakage flow across the tip from pressure surface to suction surface. A 2-D turbine blade cascade will be used for this study. A typical clearance gap will be set for the middle blade of the five-blade cascade. Relative motion of blade with the shroud will be simulated with a moving belt acting as the shroud. Velocity and pressure measurements will be obtained on the pressure and suction surface and the shroud and tip regions. Detailed mass/heat transfer measurements will be obtained on the pressure surface, the suction surface and the tip region using the Naphthalene sublimation technique. Two blade tip designs, plain and squealer, will be studied. Tip film cooling designs for experimental testing will be developed based on numerical simulations and existing industry designs. The numerical study will involve a combination of Reynolds-Averaged-Navier-Stokes (RANS) calculations with suitable turbulence models, and Direct Numerical Simulation (DNS). The RANS calculations will be used to perform analysis for different blade-tip and tip-cooling configurations under realistic engine conditions in order to determine the most promising concepts. These promising concepts will then be investigated in detail in the experimental study. The DNS calculations will be performed at lower Reynolds numbers with the intent of understanding the underlying flow physics, and to evaluate and improve the turbulence models being used in the RANS procedure. The latter is necessary in order to strengthen the RANS based assessment of blade-tip and tip-cooling configurations.