Sumanta Acharya - US grants

This experimental and analytical investigation considers the potential heat transfer enhancement from resonant excitation of the shear-layer instability in a ribbed duct flow. The specific interest is in the degree of excitation-induced enhancement for various flow and geometrical conditions resulting from external acoustic source excitation. The timewise evolution of the local wall heat transfer will be measured and linked to the instantaneous flow behavior. The complementary numerical study will assess the modeling capabilities and extend the experimental parameter range. The enhancement of heat transfer is important in many applications including electronics cooling and heat exchanger design. This research addresses heat transfer augmentation through the coupling of an external excitation and flow instability. The enhancement by flow instability has been documented so that the new part of this research is the use of external excitation. There is a potential for significant enhancement by this technique.

ABSTRACT


Proposal Number: CTS 9907773

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.

A multidisciplinary graduate program of education, research and training in Multi-Scale Computations of Fluid Dynamics (CFD) at Louisiana State University (LSU) will be undertaken in interdisciplinary partnership between the various CFD groups and the Center for Computation and Technology at LSU, and outreach partners at Southern University, Louisiana Tech University, and LSU Eye Center. All schools are tightly connected by a 40 Gbit optical network and tied to the National LambdaRail. The intellectual merit and purpose of this program is to provide doctoral students with enhanced multidisciplinary education and training that will integrate all elements critical in solving critical CFD projects of the future: distributed collaborations connected by optical networks, high performance and grid computing techniques, CFD as a fundamental discipline, and numerous fluid dynamical application areas where Louisiana has unique research strengths. Braoder impacts of the project relate to application areas that span the spectrum of flow scales (from microns to kilometers) and include biological/biomedical flows, estuarine/oceanic flows, reservoir flows, and astrophysical flows. IGERT research and education will occur at the disciplinary interfaces, with faculty mentors from two or more disciplines, and a focus on enabling large-scale parallel computing of flow systems that resolve scales and their dynamics that were previously not possible. IGERT students will complete a program of study that includes an original interdisciplinary research problem for their dissertations, and a mix of interdisciplinary fluid dynamics, computational science and CFD courses that are team-taught and cross-listed across the various departments. IGERT is an NSF-wide program intended to meet the challenges of educating U.S. Ph.D. scientists and engineers with the interdisciplinary background, deep knowledge in a chosen discipline, and the technical, professional, and personal skills needed for the career demands of the future. The program is intended to catalyze a cultural change in graduate education by establishing innovative new models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries.