Main menu >> Mechanical and Industrial Engineering >> Combustion and Propulsion

Mechanical and Industrial Engineering

Combustion and Propulsion
^ 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 multiphase, reacting motor flowfield analysis. This correlation will include the important effects of variable ambient gas composition as well as thermal radiation.

^ Heterogeneous Solid Propellant Combustion Simulation
M. Q. Brewster,* G. M. Knott, G. Pascal
DOE Center for Simulation of Advanced Rockets, B341494

The combustion of two-dimensional AP/HTPB "sandwich" propellants is simulated computationally. The framework is mass and energy transport with simplified chemical kinetics. The predicted results include steady regression rate, propellant surface geometry (free surface), and gas-phase flame structure. These three quantities are also the basis for comparison with experiments for validation of the model. The goal is to develop a simplified kinetics and transport scheme that can be used in more complex (3-D, unsteady) simulations of composite propellants.

^ Novel Energetic Materials to Stabilize Rockets (MURI)
M. Q. Brewster,* N. Burnside, B. Saarloos, G. Pascal
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 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.

^ 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 (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.

^ Diamond Growth in Flames
N. G. Glumac,* R. Lucht* (Texas A&M), T. Hu
National Science Foundation, CTS-0096279

Atmospheric and low pressure flames have the potential to serve as cost effective sources for diamond films. Recent work has suggested that these flames may be characterized by two unusual phenomena: flame temperatures that significantly exceed the adiabatic flame temperature and a large temperature discontinuity at the growth surface. This study is a combined experimental and computational effort to investigate these diamond-forming flames and to identify the underlying sources for the unusual temperature behavior, as well as to assess the consequences of these factors on the diamond growth rate. The experimental portion of the study is at Texas A&M and the computational portion is being performed at the University of Illinois at Urbana-Champaign.

^ Nonagglomerated Nanopowder Synthesis in Low Pressure Flames
N. G. Glumac,* S. Bailey
National Science Foundation, CTS-0096278

This National Science Foundation CAREER Award program is a combined study of nonagglomerated nanopowder synthesis in low pressure flames, involving synthesis of new oxide nanopowders, diagnostics of the chemical and thermal fields in a reactor, and chemical modeling of the powder formation process. Such powders have applications in areas such as chemical mechanical polishing (silica), structural materials (zirconia, alumina), optics (silica), cosmetics (titania), batteries (vanadium oxide), and catalyst supports (alumina).

^ 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.

^ Dynamic Burning of Energetic Solid Propellants
H. Krier,* T. Hafenrichter
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 and show 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.

^ 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 under way 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.

^ Solid Rocket Motor Aluminum Burning Models
H. Krier,* J. C. Melcher
DOE Center for Simulation of Advanced Rockets; U.S. Department of Energy, B341494

This research is focused on developing quasi-steady burning rate models for both pure aluminum and agglomerated aluminum droplets produced from metalized solid propellants. Chemical kinetics for various propellant gas oxidizers must be considered. Models will be compared to data available in another research project at the University of Illinois at Urbana-Champaign.

^ Modeling of Microexplosion and Flash Boiling in Engines
C. F. Lee,* Y. B. Zeng, D. L. Chang
Center for Advanced Study; Ford Motor Company

Microexplosion and flash boiling phenomena affect both vaporization and atomization of fuel sprays. For multicomponent fuel droplets, light components are entrapped inside the droplet that possibly leads to a local super-heat region and produces bubbles inside the droplet. The droplet then undergoes a violent expansion resulting in secondary breakup (so-called microexplosion). Fundamentally, flash boiling is similar to microexplosion. Both are believed to have positive effects on engine performance since they tend to produce smaller droplets compared to conventional breakup mechanisms. The theory and model for the breakup due to microexplosion and flash boiling will be developed and verified.

^ Direct Injection of Natural Gas: In-Cylinder Measurements and Calculations
J. E. Peters, C. F. Lee,* G. C. Martin, 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.

^ 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 under way. 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 fuel/air mixing, flame structure and stabilization, and pollutant formation.

^ DNS of 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, researchers 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.


Summary of Engineering Research