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You searched for subject:(Supersonic combustors). Showing records 1 – 2 of 2 total matches.

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1. Haimovitch, Yaacov. Investigation of Wall Injectors for Supersonic Mixing Enhancement.

Degree: PhD, Mechanical Engineering, 1994, Old Dominion University

A comparative study of the interaction between wall mounted swept-ramp injectors and injector nozzle shape has been conducted in a constant area duct to explore techniques to enhance mixing in scramjet combustors. The scramjet combustors are currently being developed for propulsion systems applications on the envisioned hypersonic vehicles. Short combustor residence time, a requirement for fuel injection parallel to the main flow in the combustor, and an overall strong sensitivity of the vehicle performance to the propulsion system motivated the investigation. The swept-ramp injector investigated in this study produces vortex shedding and local separation downstream of the injector's nozzle exit, at the ramp's base. Six different injector nozzle inserts for preconditioning the fuel flow were tested to explore the interaction between the preconditioned fuel jet and the vortical flowfield produced by the ramp. The six injector nozzle inserts were: circular nozzle (baseline), nozzle with three downstream facing steps in the divergent section, nozzle with four vortex generators, elliptical nozzle, tapered-slot nozzle, and trapezoidal nozzle, all having equal exit and throat areas. The main flow was air at Mach 2, and the fuel was simulated by air injected at Mach 1.63 and by helium injected at Mach 1.7. The main portion of the research involved a series of experiments conducted at the NASA Langley Research Center in the Mach 2 Traverse Jet Facility. Extensive flow field surveys, combined with Mie and Rayleigh scattering visualization were used to investigate the flow field. An existing three-dimensional Navier-Stokes code was used to conduct a numerical study which closely tracked the experimental effort. The injector performance was evaluated in terms of both the experimental and computational results. The different nozzle inserts showed only minor performance differences, indicating that the injectant/air mixing in the far-field is independent of the injector geometry, molecular weight of the injectant, and the initial convective Mach number. However, the nozzle with vortex generators displayed the highest mixing performance, and there is evidence that the tapered-slot nozzle has a promising mixing performance. In the vicinity of the ramp base, the flow is dominated by the strong vortical flow field generated by the swept-ramp while well downstream of the base ramp the quasi-axisymmetric flow pattern indicates a "loss of memory" of the near-field stirring, the flow being controlled by small-scale turbulence. The flow field characteristics (mixing and losses) of this mixing scheme are determined by the ramp, the injector inner geometry having a very little effect. The injectant penetration into the main flow at an average angle that is equal to the initial injection angle, suggests that the penetration can be controlled by changing the injection angle. Advisors/Committee Members: A. Sidney Roberts, Jr., E. Gartenberg, G. B. Northam, S. Tiwari, O. Baysal.

Subjects/Keywords: Wall injectors; Supersonic mixing; Scramjet combustors; Aerospace Engineering; Mechanical Engineering; Structures and Materials

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Haimovitch, Y. (1994). Investigation of Wall Injectors for Supersonic Mixing Enhancement. (Doctoral Dissertation). Old Dominion University. Retrieved from https://digitalcommons.odu.edu/mae_etds/135

Chicago Manual of Style (16th Edition):

Haimovitch, Yaacov. “Investigation of Wall Injectors for Supersonic Mixing Enhancement.” 1994. Doctoral Dissertation, Old Dominion University. Accessed January 24, 2021. https://digitalcommons.odu.edu/mae_etds/135.

MLA Handbook (7th Edition):

Haimovitch, Yaacov. “Investigation of Wall Injectors for Supersonic Mixing Enhancement.” 1994. Web. 24 Jan 2021.

Vancouver:

Haimovitch Y. Investigation of Wall Injectors for Supersonic Mixing Enhancement. [Internet] [Doctoral dissertation]. Old Dominion University; 1994. [cited 2021 Jan 24]. Available from: https://digitalcommons.odu.edu/mae_etds/135.

Council of Science Editors:

Haimovitch Y. Investigation of Wall Injectors for Supersonic Mixing Enhancement. [Doctoral Dissertation]. Old Dominion University; 1994. Available from: https://digitalcommons.odu.edu/mae_etds/135

2. Donde, Pratik Prakash. LES/PDF approach for turbulent reacting flows.

Degree: PhD, Aerospace Engineering, 2012, University of Texas – Austin

The probability density function (PDF) approach is a powerful technique for large eddy simulation (LES) based modeling of turbulent reacting flows. In this approach, the joint-PDF of all reacting scalars is estimated by solving a PDF transport equation, thus providing detailed information about small-scale correlations between these quantities. The objective of this work is to further develop the LES/PDF approach for studying flame stabilization in supersonic combustors, and for soot modeling in turbulent flames. Supersonic combustors are characterized by strong shock-turbulence interactions which preclude the application of conventional Lagrangian stochastic methods for solving the PDF transport equation. A viable alternative is provided by quadrature based methods which are deterministic and Eulerian. In this work, it is first demonstrated that the numerical errors associated with LES require special care in the development of PDF solution algorithms. The direct quadrature method of moments (DQMOM) is one quadrature-based approach developed for supersonic combustion modeling. This approach is shown to generate inconsistent evolution of the scalar moments. Further, gradient-based source terms that appear in the DQMOM transport equations are severely underpredicted in LES leading to artificial mixing of fuel and oxidizer. To overcome these numerical issues, a new approach called semi-discrete quadrature method of moments (SeQMOM) is formulated. The performance of the new technique is compared with the DQMOM approach in canonical flow configurations as well as a three-dimensional supersonic cavity stabilized flame configuration. The SeQMOM approach is shown to predict subfilter statistics accurately compared to the DQMOM approach. For soot modeling in turbulent flows, an LES/PDF approach is integrated with detailed models for soot formation and growth. The PDF approach directly evolves the joint statistics of the gas-phase scalars and a set of moments of the soot number density function. This LES/PDF approach is then used to simulate a turbulent natural gas flame. A Lagrangian method formulated in cylindrical coordinates solves the high dimensional PDF transport equation and is coupled to an Eulerian LES solver. The LES/PDF simulations show that soot formation is highly intermittent and is always restricted to the fuel-rich region of the flow. The PDF of soot moments has a wide spread leading to a large subfilter variance. Further, the conditional statistics of soot moments conditioned on mixture fraction and reaction progress variable show strong correlation between the gas phase composition and soot moments. Advisors/Committee Members: Raman, Venkat (advisor), Clemens, Noel (committee member), Ezekoye, Ofodike (committee member), Goldstein, David (committee member), Moser, Robert (committee member).

Subjects/Keywords: Probability density function approach; Large eddy simulation; Supersonic combustion modeling; Soot modeling; Turbulent reacting flows; Direct quadrature method of moments; Semi-discrete quadrature method of moments; Quadrature based methods; Lagrangian Monte Carlo methods; Supersonic combustors; Flame stabilization; Polycyclic aromatic hydrocarbons; Soot-turbulence-chemistry interactions; Shock-turbulence-chemistry interactions

…The first involves flame stabilization in supersonic combustors, while the second problem… …Stable and robust supersonic combustors are critical for design and development of scramjet… …milliseconds. Also, supersonic combustors are characterized by shocks, and shock-combustion-turbulent… …supersonic combustors is necessary for the design of reliable scramjet engines. 1.2 Soot… …1.1 and 1.2. Flame stabilization in supersonic combustors is characterized by strong shock… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Donde, P. P. (2012). LES/PDF approach for turbulent reacting flows. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/19481

Chicago Manual of Style (16th Edition):

Donde, Pratik Prakash. “LES/PDF approach for turbulent reacting flows.” 2012. Doctoral Dissertation, University of Texas – Austin. Accessed January 24, 2021. http://hdl.handle.net/2152/19481.

MLA Handbook (7th Edition):

Donde, Pratik Prakash. “LES/PDF approach for turbulent reacting flows.” 2012. Web. 24 Jan 2021.

Vancouver:

Donde PP. LES/PDF approach for turbulent reacting flows. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2012. [cited 2021 Jan 24]. Available from: http://hdl.handle.net/2152/19481.

Council of Science Editors:

Donde PP. LES/PDF approach for turbulent reacting flows. [Doctoral Dissertation]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/19481

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