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Journal ArticleDOI

Turbulent flame dynamics of homogeneous solid propellant in a rocket motor

01 Jan 2000-Vol. 28, Iss: 1, pp 903-910
TL;DR: In this article, a comprehensive numerical analysis has been conducted to study the combustion of a double-base homogeneous propellant in a rocket motor, where the motor internal flow development and its influence on propellant combustion were considered.
Abstract: A comprehensive numerical analysis has been conducted to study the combustion of a double-base homogeneous propellant in a rocket motor. Emphasis was placed on the motor internal flow development and its influence on propellant combustion. The formulation is based on the Favre-averaged, filtered equations for the conservation laws and takes into account finite-rate chemical kinetics and variable thermophysical properties. Turbulence closure is obtained using the large-eddy-simulation technique. The contribution of large energy-carrying structures to mass, momentum, and energy transfer is computed explicitly, and the effect of small scales of turbulence is modeled. The governing equations and associated boundary conditions are solved using a time-accurate, semi-implicit Runge-Kutta scheme coupled with a fourth-order central difference algorithm for spatial discretization. The motor internal flowfield is basically determined by the balance between the inertia force and the pressure gradient arising from the mass injection at the propellant surface. The temporal evolution of the vorticity field shows a laminar upstream region, a transition zone in the midsection of the chamber, and a fully developed turbulent regime further downstream. The turbulent mixing proceeds at a rate faster than chemical reactions, and the flame stretch is strong enough to regard propellant combustion as a well-stirred reactor. The combustion wave in the laminar region exhibits a two-stage structure consisting of a primary flame, a dark zone, and a secondary luminous flame. The enhanced energy and mass transport in the turbulent region partially merges the primary and secondary flames, thereby raising the temperatures in the dark zone. In the present study, the smoother axial velocity gradient and vertical flow convection prevent turbulence from deeply penetrating into the primary flame zone. The turbulence energy spectra indicate dominant harmonics in a frequency range capable of triggering combustion instabilities.

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Citations
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Journal Article
01 Jan 1998-Scopus
TL;DR: In this paper, the results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale combustion models.
Abstract: Results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale (SGS) combustion models. Both a priori and a posteriori assessments are conducted. The SGS turbulence model used is the dynamic Smagorinsky model (DSM). Two classes of SGS combustion models are employed in this study. These include the conserved scalar approach and the direct closure approach. Specifically, the SGS combustion models involve several forms of direct filtered reaction rate closures, including a scale similarity filtered reaction rate model (SSFRRM), and a mixing controlled strained laminar flamelet model (SLFM) in the form of thermochemical state relationships, obtained from the DNS, and two assumed forms for the subgrid mixture fraction filtered density function (FDF). In general, LES results are in reasonable agreement with DNS results and highlight the performance of the various SGS combustion models. In particular, in the context of the present study, it is found that: (1) the SLFM cases overpredict product formation due to their inability to capture finite-rate chemistry effects; (2) due to the relatively low values of the SGS mixture fraction variance in the flow under study, the SLFM results are not sensitive to the form of the assumed FDF; and (3) in comparison to the other models investigated, the SSFRRM combustion model provides the best agreement with the DNS for product formation.

169 citations

Journal ArticleDOI
TL;DR: The effect of unresolved subgrid scales is treated by using a dynamic Smagorinsky model extended to compressible flows with high injection rates in a chamber closed at one end and connected to a divergent nozzle at the exit as discussed by the authors.
Abstract: The unsteady flow evolution in a porous chamber with surface mass injection simulating propellant burning in a nozzleless solid rocket motor has been investigated by means of a large-eddy simulation (LES) technique. Of particular importance is the turbulence-transition mechanism in injection-driven compressible flows with high injection rates in a chamber closed at one end and connected to a divergent nozzle at the exit. The spatially filtered and Favre-averaged conservation equations of mass, momentum and energy are solved for resolved scales. The effect of unresolved subgrid scales is treated by using a dynamic Smagorinsky model extended to compressible flows. Three successive regimes of flow development are observed: laminar, transitional, and fully developed turbulent flow. Surface transpiration facilitates the formation of roller-like vortical structures close to the injection surface. The flow is essentially two-dimensional up to the mid-section of the chamber, with the dominant frequencies of vortex shedding governed by two-dimensional hydrodynamic instability waves. These two-dimensional structures are convected downstream and break into complex three-dimensional eddies. Transition to turbulence occurs further away from the wall than in standard channel flows without mass injection. The peak in turbulence intensity moves closer to the wall in the downstream direction until the surface injection prohibits further penetration of turbulence. The temporal and spatial evolution of the vorticity field obtained herein is significantly different from that of channel flow without transpiration.

70 citations


Cites background from "Turbulent flame dynamics of homogen..."

  • ...…numerical study also serves as a foundation for our parallel efforts to explore the effects of unsteady heat release and turbulent flame dynamics on the microscale motions close to the propellant surface and macroscale motions in the bulk of the chamber (Roh, Apte & Yang 1998; Apte & Yang 2000b)....

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  • ...Our earlier numerical investigations of injection-driven flows in rocket motors (Apte & Yang 2000a, 2001, 2002; Apte 2000) indicated two-dimensional roll-up-like vortical structures throughout the chamber....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a time-resolved numerical analysis of combustion dynamics of double-base homogenous solid propellant in a rocket motor is performed by means of a Large-Eddy Simulation (LES) technique.

49 citations

Journal ArticleDOI
TL;DR: In this article, a detailed theoretical/numerical framework is established to study the mechanical erosion of graphite-nozzle materials in solid rocket motors with aluminized ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants.
Abstract: A detailed theoretical/numerical framework is established to study the mechanical erosion of graphite-nozzle materials in solid rocket motors with aluminized ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants. The analysis is based on a combined Eulerian–Lagrangian approach for treating multiphase motor flowfields. The multicomponent reacting gas-phase dynamics is formulated using the conservation equations of mass, momentum, and energy in the Eulerian framework. Turbulence closure is achieved using the standard k-e two-equation model. The dispersed phase, consisting of aluminum and alumina droplets, is treated in the Lagrangian framework. Combustion of aluminum droplets to aluminum-oxide smoke is considered. Two empirical correlations are first calibrated and then employed to predict the mechanical-erosion rate of the nozzle surface. The estimated erosion rates fall within the range of the available experimental data. Mechanical erosion is prevalent in the convergent section of ...

34 citations

Journal ArticleDOI
TL;DR: In this article, the interphase coupling between the gas and particle under the ine uence of acoustic excitation and turbulence dispersion and the intraphase interactions among particles such as collision and coalescence is investigated.
Abstract: Two-phase e ow interactions with vorticoacoustic oscillations in simulated solid-propellant rocket motors have been studied numerically using a combined Eulerian ‐Lagrangian approach The model accommodates the complete conservation equations in axisymmetric coordinates and, consequently, allows for a detailed treatment of particle dynamics and unsteady motor internal e ow evolution Emphasis is placed on the interphase coupling between the gas and particle e elds under the ine uence of acoustic excitation and turbulence dispersion and the intraphase interactions among particles such as collision and coalescence The study demonstrates that acoustic oscillations provide additional mechanisms to transfer energy from periodic motions to turbulence, leading to an enhanced level of turbulence intensity and an early transition from laminar to turbulence On the other hand, turbulence-induced eddy viscosity tends to suppress vortical e ow motions caused by acoustic waves The thermal and momentum relaxation times of particles, along with acoustic characteristic time, play an important role in dictating thetwo-phase e ow interactionswith oscillatory motorinternal e ows Amaximum attenuation of acoustic waves occurs when those timescales become comparable Small particles, however, usually exert greater ine uence on thedispersion ofacousticwave through its effectivemodie cation of mixturecompressibility Particleintraphase interactions are signie cant mainly in situations with a wide range of particle size distribution

33 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a class of numerical dissipation models for central-difference schemes constructed with second and fourth difference terms is considered, where the notion of matrix dissipation associated with upwind schemes is used to establish improved shock capturing capability for these models.

482 citations

Journal ArticleDOI
TL;DR: In this paper, it is shown that the creation of vorticity is due primarily to the axial unsteady pressure gradient across mean flow streamlines at the surface, and that there is a transfer of energy from the pressure oscillations (acoustic field) to the rotational waves (vorticity field).
Abstract: Combustion stability computations are currently based on an irrotational model that allows slip flow at the burning surface. However, the no-slip boundary condition must be satisfied when gas motions are parallel to the combustion zone. Then waves of vorticity are created that distort the acoustic wave structure and modify the fluctuating normal velocity component upon which system stability is so strongly dependent. This flow problem is solved here in analytical form to bring the physical details into focus. Crocco's theorem shows that the creation of vorticity is due primarily to the axial unsteady pressure gradient across mean flow streamlines at the surface. Hence, there is a transfer of energy from the pressure oscillations (acoustic field) to the rotational waves (vorticity field). It is in this interaction that the incoming flow acquires the axial motion of the acoustic wave. Stability calculations based on this model yield the three-dimensional form of Culick's one-dimensional flow-turning correction and clarify its origin. However, continuity at the burning surface requires a correction to the radial velocity fluctuations. Incorporation of this new driving effect leads to a motor system that is significantly less stable than in the classical prediction (Standard Stability Prediction Program) for some configurations.

193 citations

Journal Article
01 Jan 1998-Scopus
TL;DR: In this paper, the results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale combustion models.
Abstract: Results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale (SGS) combustion models. Both a priori and a posteriori assessments are conducted. The SGS turbulence model used is the dynamic Smagorinsky model (DSM). Two classes of SGS combustion models are employed in this study. These include the conserved scalar approach and the direct closure approach. Specifically, the SGS combustion models involve several forms of direct filtered reaction rate closures, including a scale similarity filtered reaction rate model (SSFRRM), and a mixing controlled strained laminar flamelet model (SLFM) in the form of thermochemical state relationships, obtained from the DNS, and two assumed forms for the subgrid mixture fraction filtered density function (FDF). In general, LES results are in reasonable agreement with DNS results and highlight the performance of the various SGS combustion models. In particular, in the context of the present study, it is found that: (1) the SLFM cases overpredict product formation due to their inability to capture finite-rate chemistry effects; (2) due to the relatively low values of the SGS mixture fraction variance in the flow under study, the SLFM results are not sensitive to the form of the assumed FDF; and (3) in comparison to the other models investigated, the SSFRRM combustion model provides the best agreement with the DNS for product formation.

169 citations

Journal ArticleDOI
TL;DR: In this article, the mean and fluctuating speed and turbulent shear stresses were measured in the principle coordinate directions using three-element hot-wire anemometers, showing that noticeable velocity fluctuations in the head end region generally decrease in intensity, relative to centerline speed, over the first five port diameters.
Abstract: The objective of these studies is to experimentally characterize the mean and fluctuating flow field that develops along the length of a simulated cylindrical port rocket chamber. Flow simulation was accomplished by injecting ambient temperature nitrogen uniformly along the walls of 10.2-cm (4-in.) diam, porous-tube chambers connected to a choked sonic nozzle. Experiments were conducted with chamber L/D ratios of 9.5 and 14.3, at injection Mach numbers and Reynolds numbers typical of rocket motor values. Maximum Reynolds numbers based on injection and centerline velocities were, respectively, 1.8 x 10 and 1.6 x 10. Mean and fluctuating speed and turbulent shear stresses were measured in the principle coordinate directions using three-element hot-wire anemometers. The data show that noticeable velocity fluctuations in the head-end region generally decrease in intensity, relative to centerline speed, over the first five port diameters. At this point, regular velocity oscillations appear near the wall, just prior to the transition to turbulent flow. The oscillation frequency characteristics suggest the occurrence of vortical disturbances which exhibit pairing as they move away from the wall. The downstream turbulence development is characterized by a slow spreading toward the centerline: peak values of turbulence intensity and shear stress occur a few tenths of a port radius from the wall and remain relatively constant. Mean velocity profiles prior to transition show fair agreement with those derived for a rotational inviscid flow injected normal to the surface. A slow transition from these profiles occurs downstream in the turbulent region. Two surprising features of the flow were the occurrence of both buoyant flow influences and flow spinning in forward regions of the chamber.

167 citations

Journal ArticleDOI
TL;DR: In this article, the results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale combustion models.
Abstract: Results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale (SGS) combustion models. Both a priori and a posteriori assessments are conducted. The SGS turbulence model used is the dynamic Smagorinsky model (DSM). Two classes of SGS combustion models are employed in this study. These include the conserved scalar approach and the direct closure approach. Specifically, the SGS combustion models involve several forms of direct filtered reaction rate closures, including a scale similarity filtered reaction rate model (SSFRRM), and a mixing controlled strained laminar flamelet model (SLFM) in the form of thermochemical state relationships, obtained from the DNS, and two assumed forms for the subgrid mixture fraction filtered density function (FDF). In general, LES results are in reasonable agreement with DNS results and highlight the performance of the various SGS combustion models. In particular, in the context of the present study, it is found that: (1) the SLFM cases overpredict product formation due to their inability to capture finite-rate chemistry effects; (2) due to the relatively low values of the SGS mixture fraction variance in the flow under study, the SLFM results are not sensitive to the form of the assumed FDF; and (3) in comparison to the other models investigated, the SSFRRM combustion model provides the best agreement with the DNS for product formation.

152 citations