Browsing by Subject "Scramjet"
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Item Computational Study of Shock/Plume Interactions Between Multiple Jets in Supersonic Crossflow(2016-08) Tylczak, ErikThe interaction of multiple jets in supersonic crossflow is simulated using hybrid Reynolds- Averaged Navier Stokes and Large Eddy Simulation turbulence models. The blockage of a jet generates a curved bow shock, and in multi-jet flows, each shock impinges on the other fuel plumes. The curved nature of each shock generates vorticity directly, and the impingement of each shock on the vortical structures within the adjacent fuel plumes strengthens vortical structures already present. These stirring motions are the major driver of fuel-air mixing, and so mixing enhancement is predicted to occur in multi-port configurations. The primary geometry considered is that of the combustion duct at the Calspan- University of Buffalo Research Center 48” Large Energy National Shock (LENS) tunnel. This geometry was developed to be representative of the geometry and flow physics of the Flight 2 test vehicle of the Hypersonic International Flight Research Experimenta- tion Program (HiFIRE-2). This geometry takes the form of a symmetric pair of external compression ramps that feed an isolator of approximately 4” × 1” cross-section. Nine interdigitated flush-wall injectors, four on one wall and five on the other, inject hydrogen at an angle of 30 degrees to the freestream. Two freestream flow conditions are consid- ered: approximately Mach 7.2 at a static temperature of 214K and a density of 0.039 kg/m3 for the five-injector case, and approximately Mach 8.9 at a static temperature of 167K and density of 0.014 kg/m3 for the nine-injector case. Validation computations are performed on a single-port experiment with an imposed shock wave. Unsteady calculations are performed on five-port and nine-port configura- tions, and the five-port configuration is compared to calculations performed with only a single active port on the same geometry. Analysis of statistical data demonstrates enhanced mixing in the multi-port configurations in regions where shock impingement occurs.Item Simulations of injection, mixing, and combustion in supersonic flow using a hybrid RANS/LES approach.(2011-09) Peterson, David MichaelThere is a great need for accurate and reliable numerical simulation of injection, mixing, and combustion in supersonic combustion ramjet engines. This study seeks to improve the accuracy and reliability which these flow can be simulated with by investigating the use of recent improvements in turbulence modeling and numerical methods. The present numerical simulations use implicit time integration and low-dissipation flux evaluation schemes in an unstructured grid framework. A hybrid Reynolds-Averaged Navier-Stokes and large-eddy simulation approach is used to model turbulence. The large-scale turbulent structure of the flow is resolved, while the near-wall structure is fully modeled. The effects of numerics, grid resolution, and boundary conditions are investigated. The simulation approach is thoroughly validated against available experimental data at a variety of flow conditions. The simulations focus on the injection of fuel through circular injector ports that are oriented either normal to the supersonic crossflow, or at a low angle with respect to the crossflow. The instantaneous flow structure resolved by the simulations is qualitatively compared to experimental flowfield visualization. Quantitative comparisons are made to mean wall pressure, mean velocity, turbulence quantities, and mean mixing data. The simulations are found to do very well at predicting the mean flowfield as well as fluctuations in velocity and injectant concentration. The simulation approach is then used to simulate the flow within a model supersonic combustor. The focus is on the non-reacting case. The simulation results are found to agree well with experimental measurements of temperature and species concentrations. The flow is examined to improve understanding of the mixing within the model combustor. Preliminary results for a simulation including hydrogen combustion are also presented.