We report on modifications to the widely used astrophysical code, FLASH (Fryxell, Olson et al. 2000) that enable accurate simulations of chemically reacting flows with heat addition. The enhancements to FLASH include the implementation of extensive Hydrogen-air and Methaneair chemistry through multiple, detailed mechanisms (Smooke 1991; Katta and Roquemore 1995; Mueller, Kim et al. 1999; Billet 2005), accomplished by building on the existing infrastructure of nuclear reaction network solvers. The chemical reaction network is represented as a system of coupled ODEs, that are then solved either through the Kaps-Rentrop (Rosenbrok) method(Kaps and Rentrop 1979) or the Bader-Deuflhard method (Bader and
For the application of waste heat recovery (WHR), supercritical CO2 (S-CO2) Brayton power cycles offer significant suitable advantages such as compactness, low capital cost, and applicability to a broad range of heat source temperatures. The current study is focused on thermodynamic modeling and optimization of recuperated (RC) and recuperated recompression (RRC) configurations of S-CO2 Brayton cycles for exhaust heat recovery from a next generation heavy duty simple cycle gas turbine using genetic algorithm (GA). This nongradient based algorithm yields a simultaneous optimization of key S-CO2 Brayton cycle decision variables such as turbine inlet temperature, pinch point temperature difference, compressor pressure ratio, and mass flow rate of CO2. The main goal of the optimization is to maximize power out of the exhaust stream which makes it single objective optimization. The optimization is based on thermodynamic analysis with suitable practical assumptions which can be varied according to the need of user. The optimal cycle design points are presented for both RC and RRC configurations and comparison of net power output is established for WHR. For the chosen exhaust gas mass flow rate, RRC cycle yields more power output than RC cycle. The main conclusion drawn from the current study is that the choice of best cycle for WHR actually depends heavily on mass flow rate of the exhaust gas. Further, the economic analysis of the more power producing RRC cycle is performed and cost comparison between the optimized RRC cycle and steam Rankine bottoming cycle is presented.
An experimental investigation of detailed flow and heat transfer in a narrow impingement channel was studied; the channel included 15 inline jets in a single row with a jet-to-target wall distance of 3 jet diameters. The spanwise length of the channel was 4 jet diameters, and a streamwise jet spacing of 5 jet diameters was considered for the current study. Both the flow physics and heat transfer tests were run at an average jet Reynolds number of 30,000. Temperature sensitive paint was used to study heat transfer at the target wall. Along with other parameters, jet-to-jet interaction in a narrow row impingement channel plays a significant role on heat transfer distribution at the side and target walls as the self-induced jet cross flow tends to bend the downstream jets. The present work shows detailed information of flow physics using Particle Image Velocimetry (PIV). PIV measurements were taken at planes normal to the target wall along the jet centerline for several jets. The flow field and heat transfer data was compared between the experiment and CFD in order to understand the relationship between flow characteristics and heat transfer. The experimental data gathered from PIV can be used as benchmark data for validating the current state of the art RANS turbulence models as well as for Large Eddy Simulation (LES).
The present study aims to understand the flow, turbulence, and heat transfer in a single row narrow impingement channel for gas turbine heat transfer applications. Since the advent of several advanced manufacturing techniques, narrow wall cooling schemes have become more practical. In this study, the Reynolds number based on jet diameter was ≃15,000, with the jet plate having fixed jet hole diameters and hole spacing. The height of the channel is three times the impingement jet diameter. The channel width is four times the jet diameter of the impingement hole. The dynamics of flow and heat transfer in a single row narrow impingement channel are experimentally and numerically investigated. Particle image velocimetry (PIV) was used to reveal the detailed information of flow phenomena. PIV measurements were taken at a plane normal to the target wall along the jet centerline. The mean velocity field and the turbulent statistics generated from the mean flow field were analyzed. The experimental data from the PIV reveal that the flow is highly anisotropic in a narrow impingement channel. To support experimental data, wall-modeled large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) simulations (shear stress transport k–ω, ν2−f, and Reynolds stress model (RSM)) were performed in the same channel geometry. Mean velocities calculated from the RANS and LES were compared with the PIV data. Turbulent kinetic energy budgets were calculated from the experiment, and were compared with the LES and RSM model, highlighting the major shortcomings of RANS models to predict correct heat transfer behavior for the impingement problem. Temperature-sensitive paint (TSP) was also used to experimentally obtain a local heat transfer distribution at the target and the side walls. An attempt was made to connect the complex aerodynamic flow behavior with the results obtained from heat transfer, indicating heat transfer is a manifestation of flow phenomena. The accuracy of LES in predicting the mean flow field, turbulent statistics, and heat transfer is shown in the current work as it is validated against the experimental data through PIV and TSP.
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