Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session E35: Compressible Reacting Flows and Rocket Combustion |
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Chair: Venkat Raman, University of Texas at Austin Room: 2001A |
Sunday, November 23, 2014 4:45PM - 4:58PM |
E35.00001: Assessment of chemistry models for compressible reacting flows Simon Lapointe, Guillaume Blanquart Recent technological advances in propulsion and power devices and renewed interest in the development of next generation supersonic and hypersonic vehicles have increased the need for detailed understanding of turbulence-combustion interactions in compressible reacting flows. In numerical simulations of such flows, accurate modeling of the fuel chemistry is a critical component of capturing the relevant physics. Various chemical models are currently being used in reacting flow simulations. However, the differences between these models and their impacts on the fluid dynamics in the context of compressible flows are not well understood. In the present work, a numerical code is developed to solve the fully coupled compressible conservation equations for reacting flows. The finite volume code is based on the theoretical and numerical framework developed by Oefelein (Prog. Aero. Sci. 42 (2006) 2-37) and employs an all-Mach-number formulation with dual time-stepping and preconditioning. The numerical approach is tested on turbulent premixed flames at high Karlovitz numbers. Different chemical models of varying complexity and computational cost are used and their effects are compared. [Preview Abstract] |
Sunday, November 23, 2014 4:58PM - 5:11PM |
E35.00002: ABSTRACT WITHDRAWN |
Sunday, November 23, 2014 5:11PM - 5:24PM |
E35.00003: Numerical Simulations of a Reacting Sonic Jet in a Supersonic Cross-flow Nitesh Attal, Praveen Ramaprabhu Interaction of a jet with a background cross-flow is a situation common to many engineering systems, including combustors in SCRAMJETS, gas turbines etc. Such an interaction enhances fuel-air mixing through the distortion of coherent structures into counter-rotating vortex pairs that are tilted, stretched and then sundered by the velocity gradient in the cross-flow, eventually leading to turbulent mixing. The ignition process and flame characteristics depend sensitively on the extent and efficiency of this turbulent mixing process. We describe results from detailed 3D numerical simulations of a sonic circular jet of diameter (D$=$0.5 cm) issuing a mixture of H$_{2}$ (Fuel) diluted with 50{\%} N$_{2}$ at 300K into a turbulent, Mach 2 cross-flow of air at 1200K. The simulations were performed in a computational domain of 20x16x16 jet diameters using the compressible flow code FLASH [1], with modifications [2] to handle detailed (H$_{2}$-O$_{2})$ chemistry and temperature-dependent material properties. We discuss the role of shock driven mixing, ignition and flame anchoring on the combustion efficiency of the system. \\[4pt] [1] B. Fryxell et al., Astrophys. J., Suppl. Ser. 131,273(2000)\\[0pt] [2] N. Attal et al., Comput. Fluids(under review) [Preview Abstract] |
Sunday, November 23, 2014 5:24PM - 5:37PM |
E35.00004: Simultaneous high-speed schlieren and OH chemiluminescence imaging in a hybrid rocket combustor at elevated pressures Victor Miller, Elizabeth T. Jens, Flora S. Mechentel, Brian J. Cantwell In this work, we present observations of the overall features and dynamics of flow and combustion in a slab-type hybrid rocket combustor. Tests were conducted in the recently upgraded Stanford Combustion Visualization Facility, a hybrid rocket combustor test platform capable of generating constant mass-flux flows of oxygen. High-speed (3 kHz) schlieren and OH chemiluminescence imaging were used to visualize the flow. We present imaging results for the combustion of two different fuel grains, a classic, low regression rate polymethyl methacrylate (PMMA), and a high regression rate paraffin, and all tests were conducted in gaseous oxygen. Each fuel grain was tested at multiple free-stream pressures at constant oxidizer mass flux (40 kg/m$^{\mathrm{2}}$s). The resulting image sequences suggest that aspects of the dynamics and scaling of the system depend strongly on both pressure and type of fuel. [Preview Abstract] |
Sunday, November 23, 2014 5:37PM - 5:50PM |
E35.00005: Experimental characterization of solid propellants combustion by digital holography Jun Chen, Michael Powell, Jian Gao, Ibrahim Gunduz, Daniel Guildenbecher, Steve Son Aluminum and other additions are widely used in solid propellants to improve performance. In this study, we apply digital holography as a three-dimensional diagnostic tool to characterize the burning of composite solid propellants with addition of different composite particles. Structures around the burning surfaces and reaction zones are identified, whereas the drop morphologies and their size/velocity distributions are quantified. The nano-second exposure of this imaging technique enables time-freezing measurements of the highly dynamic combustion process. The results are compared with discoveries from high-speed imaging. This technique is also applied to study the combustions of solid propellants under high-pressure environment. [Preview Abstract] |
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