Jack Raul Zausner

RANS Evaluations of Internal Cooling Passage Geometries: Ribbed Passages and a 180 Degree Bend

A comprehensive study and assessment of RANS based turbulence models is performed on internal cooling duct passages of turbine blades. Conjugate computational heat transfer studies of 90 and 45 degree turbulated ducts are performed and compared to experimental data from the Von Karmon Institute. Spatially resolved Nusselt number distributions are computed using CFX in conjunction with several RANS based turbulence models. In addition, similar computational studies of a 180 degree turnaround bend are performed and compared to experimental data from Arizona State University. In that experiment, area averaged Nusselt numbers are provided at different locations throughout a 180 degree turn around bend. For both analyses, the experimental data sets are carefully chosen as the original authors/experimentalists clearly identified the geometry and boundary conditions such that there was no ambiguity for CFD analysis. For the 90 degree turbulator orientation, it was found that most two equation models largely under predicted heat transfer levels. For the 45 degree turbulator configuration, it was found that a new SST based turbulence formulation, provided by CFX, adequately matched the experimental data. For the 180 degree turnaround bend, Nusselt numbers were well predicted by this new formulation. For all geometries analyzed, resorting to a particular higher moment closure model inside of CFX provided no extra benefit in terms of accuracy.© 2007 ASME

Thermodynamic Analysis of CO2 Capture Cycles Using Pre-Combustion Decarbonization and Membrane Technologies

Over the past 5–10 years, interest has increased significantly in CO2 free power generation cycles. This study focuses on precombustion decarbonization cycles that reform syngas, separating the CO2 using a membrane, and then burning hydrogen-rich fuel in a gas turbine. The syngas reforming section is comprised of 1) Auto-thermal reformer (ATR) used for syngas production 2) water gas shift reactor (WGSR) to shift CO into CO2 3) CO2 -separation membrane and 4) combustion with hydrogen rich fuel. Overall performance shows an efficiency loss of 8.4% and 10.6% compared to the baseline cycle for the high and low temperature CO2 membrane cycles examined. The operating temperatures of the membranes are limited by the exothermic CO shift reaction favoring lower temperatures. Furthermore, a chemical exergy analysis of the reformers in the decarbonization system is undertaken to understand the impact of fuel reforming.Copyright

Design of a Highly Offset Pipe-to-Annular Flow Inlet

Conceptual design and CFD analysis of an inlet to a compressor is undertaken. In this design the inlet transitions pipe flow to annular flow and provides for a mechanical device to be mounted in centerline and in front of the compressor. The solution to this constraint along with the constraints of uniform outlet flow and low weight, size, and total pressure drop consists of: a highly offset transition region, where pipe flow is transitioned into annular flow, and a nozzle region, with the goal of delivering uniform flow to the compressor at minimal pressure drop. The design approach consists of utilizing CFD to guide the overall shape of the inlet toward desirable regions of the design space, then examining specific parameters and optimizing these to meet the constraints. A final analytical inlet design, optimized in the regions of interest, is selected for experimental work.Copyright