Aluminum Combustion in Solid Rockets
M. Q. Brewster,* K. C. Tang
DOE Center for Simulation of Advanced Rockets, B341494

The combustion of aluminum droplets in a solid rocket motor internal flowfield will be simulated using a simple vapor phase diffusion-limited droplet burning model. Two versions will be developed. First, a detailed model will be developed based on numerical solution of the governing differential equations for droplet burning in a convective, radiative environment. From the results of this detailed model, a 'd2' correlation will be extracted for use in the multi-phase, reacting motor flowfield analysis. This correlation will include the important effects of variable ambient gas composition as well as thermal radiation.

Combustion of Aluminum in Solid Rocket Motors
H. Krier,* R. L. Burton* (Aero. & Astro. Engr.), J. C. Melcher
U.S. Office of Naval Research, N00014-95-1-1339

Using a laboratory-scale, end-burning solid propellant rocket motor, ignition and combustion of aluminum particles generated from aluminized solid propellant are observed by spectroscopic techniques and optical measurements. Theoretical models are being tested to confirm the metal burning rate as a function of gas composition and pressure. Measurements will be compared to an unsteady metal combustion model.

Combustion of Energetic Materials
M. Q. Brewster,* A. Ali
Los Alamos National Laboratory, DOE ANL 2434V00163G

The objectives of this study are (1) to develop and validate a one-dimensional, premixed gas phase reaction code to be coupled with an existing condensed phase code which will calculate burning rate, temperature profile, and species profiles; (2) to use this code to investigate the domain of validity of existing activation energy asymptotics analytic results; (3) to develop new analytic results that can predict variations in steady burning rate and flame standoff distance with pressure, initial temperature, and radiant heat flux; and (4) to apply these models to steady and oscillatory (quasi-steady) burning of RDX and HMX.

DNS of a Two-Phase Flow in a Solid Rocket Motor
S. P. Vanka,* S. L. Rani
U.S. Department of Energy, DOE B341494

This effort is part of a large project to develop advanced simulation tools for a solid rocket motor. Under this task, we will be developing the fluid flow aspects of the project. This will include large eddy simulations of the core flow in a rocket motor. Computations are being performed for two-phase particle laden turbulent flow in a pipe with one-way and two-way couplings.

Direct Injection of Natural Gas-In-Cylinder Measurements and Calculations
J. E. Peters,* R. P. Lucht,* G. C. Martin, T. J. Schmid, J. J. Stephens
Caterpillar, Inc.

Natural gas is an attractive alternative fuel for diesel engines because of the potential for achieving high thermal efficiencies and power densities, reduced fuel costs, and reduced particulate emissions. A single-cylinder engine has been modified to provide optical access to the cylinder for measurements of fuel/air mixing, flame propagation, and NO formation using laser-induced fluorescence. The goal of the research is to provide a better understanding of the mixing and combustion processes within the cylinder in order to improve performance and reduce emissions.

Dynamic Burning of Energetic Solid Propellants
H. Krier,* J. J. Murphy, S. Chai, C. Brdar
U.S. Ballistic Missile Defense Organization, N00014-95-1-1339

To explain rocket motor combustion instability, one must know the propellant burning rate response to pressure transients. Two end burning solid propellant rocket motors, where the motor throat area is modulated, give rise to pressure fluctuations during which instantaneous burning rate, gas species, and gas temperature are measured. Laser diagnostics and ultrasonic techniques are being used, showing significant nonsteady burning rate responses. Data generated allows for propellant ratings toward combustion instability. The ultrasound techniques for measuring burning rate employ sophisticated digital signal processing techniques and require careful evaluation of, and correction for, the effects of the material properties of the propellant.

Fuel/Air Mixing and Flame Structure Measurements in Premixed Gas Turbine Combustors
J. E. Peters,* R. P. Lucht,* R. E. Foglesong, T. R. Frazier
General Electric Aircraft Engines; U.S. Air Force Office of Scientific Research, AF6E200-1Q14N44083, F49620-97-1-0456

In a collaborative effort with General Electric Aircraft Engines, an experimental investigation of gas turbine combustor concepts is underway. Advanced nonintrusive laser diagnostics including CARS and LIF are being used to probe the fuel/air mixing and combustion processes. The purpose of this research program is to 'bridge the gap' from more fundamental experimental and modeling studies of turbulent mixing and combustion to the combustor design process. The technical issues that are being addressed include (1) fuel/air mixing, (2) flame structure and stabilization, and (3) pollutant formation.

Modeling Nonideal Detonation Structure
H. Krier*
University of Illinois

The task of developing a multicomponent, multiphase hydrodynamic model that describes all the salient features of an underwater explosion of metal-loaded high explosives is addressed. The models represent a significant advancement over previous efforts because they include nonideal phenomena not previously considered (e.g., combustion of metal-loaded high explosives). The primary purpose of this work is to predict eigenvalue detonation speeds with resolved structure of such waves.

Modeling the Unsteady Burning of Heterogeneous Solid Propellants
H. Krier,* J. J. Murphy
DOE Center for Simulation of Advanced Rockets; U.S. Department of Energy, B341494; U.S. Ballistic Missile Defense Organization, N00014-95-1-1339

Current models describing unsteady burning in homogeneous solid propellants are extended to include several phenomena that are believed to be important to unsteady burning in heterogeneous solid propellants. The goal is to predict certain features observed in the experimentally measured burning rate response.

Novel Energetic Materials to Stabilize Rockets (MURI)
M. Q. Brewster,* B. Chorpening, G. Knott
Ballistic Missile Defense Organization/U.S. Office of Naval Research, N00014-95-1-1339

As new energetic materials are developed for use as propellants in solid rockets, it will be necessary to consider their combustion stability at an early stage of propellant development. This will require a multidisciplinary approach including complex chemistry, combustion, and fluid dynamics. The overall objective of this project is to conduct a coordinated, multidisciplinary investigation to advance our knowledge of dynamic burning response of new combinations of energetic materials. The specific objective is to develop an understanding of the combustion behavior of new energetic materials as monopropellants and combinations of new and conventional energetic materials as composite propellants.

Radiation Heat Transfer in Solid Rocket Motors
M. Q. Brewster,* K. C. Tang
DOE Center for Simulation of Advanced Rockets, B341494

Thermal radiation is an important mode of heat transfer in rocket motor internal flowfields. The primary source of thermal radiation is the field of submicron, liquid phase Al2O3 'smoke' particles formed by aluminum droplet combustion. In addition, pressure-broadened line radiation from molecular gases such as CO2, H2O, and HCl is also important at the elevated pressures in rockets. A hybrid radiation model will be developed with an N-flux description near the propellant surface matched with a diffusion approximation in the core region. A k-distribution technique will be used to accommodate the continuum particle radiation and the molecular gas line radiation.

Shock Ignition of Energetic Metals
H. Krier,* R. L. Burton* (Aero. & Astro. Engr.), J. Servaites
U.S. Ballistic Missile Defense Organization, N00014-95-1-1339

New energetic solid propellants will contain metals such as aluminum, magnesium, and boron. Experiments in a high-pressure shock tube measuring aluminum ignition delay and combustion (burn) time, as well as measurements by emission and absorption spectroscopy of the transient reactive species are underway, and will impact chemical kinetic theories on reaction pathways for such two-phase mixtures. This data is necessary for predicting aluminum particle combustion in solid rocket motors.

Simulation of Interior Ballistics of Solid Rocket Motors
H. Krier,* F. Najar, R. Fiedler, P. Alavilli
DOE Center for Simulation of Advanced Rockets; U.S. Department of Energy, B341494

To coordinate the overall predictions of the interior ballistics of modern solid-propellant rocket motors, simulation codes are used to predict steady-state performance. Calculation of pressure distribution, burning rates, and overall rocket thrust are made, and will be used as control predictions for multidimensional, transient codes being developed by CSAR.

Solid Propellant Combustion Modeling
M. Q. Brewster,* K. C. Tang
DOE Center for Simulation of Advanced Rockets, B341494

The heterogeneous combustion zone near a composite propellant surface is being simulated. The first approach will be to utilize the quasi-static approximation (quasi-steady gas and solid preheat zones). For sufficiently rapid transient events (i.e., of time scales less than the thermal relaxation time of the propellant which is on the order of 1 to 10 ms), the quasi-static of approximation fails and a second approach will be utilized: a modification of the Zeldovich-Novozhilov (ZN) method for extending steady state burning data to the unsteady regime, still retaining the quasi-steady gas assumption.

Solid Rocket Motor Combustion Instability
H. Krier,* J. J. Murphy
DOE Center for Simulation of Advanced Rockets; U.S. Department of Energy, B341494

Using coupled Navier-Stokes equations and compressible energy conservation is solving the unsteady, two-dimensional flow of gases inside a solid rocket motor. Propellant response functions to both pressure oscillations and velocity fluctuations show regimes where motor instability is predicted. Rocket motor combustion instability continues to be a problem that can cause overpressurization with motor failure.