Jerry Seitzman

Bio: Jerry Seitzman is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Combustor & Combustion. The author has an hindex of 31, co-authored 149 publications receiving 3357 citations. Previous affiliations of Jerry Seitzman include Georgia Tech Research Institute & ExxonMobil.

The effects of bimodal aluminum with ultrafine aluminum on the burning rates of solid propellants

Abstract: Burning rates were measured for aluminized composite propellants with different aluminum (Al) sizes(monomodal distribution) and with bimodal Al distributions containing various amounts of ultrafine Al (UFAl). Enhanced rates were found for fine Al, with the enhancement increases for reduced Al size. The fine Al also burned in an intense region very close to the propellant surface, suggesting improved heat feedback in the form of radiation and conduction. Major modification of the burning rate could be achieved with moderate amounts of UFAl. Results obtained with various fine oxidizer particle sizes and mass fractions suggest that the degree of burning-rate modification depends on the ability to ignite the UFAl, for example, with leading-edge flames, as well as the availability of oxidizer near the Al-containing regions of the propellant.

Flame transfer function saturation mechanisms in a swirl-stabilized combustor

Abstract: An understanding of the amplitude dependence of the flame response to harmonic acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the mechanisms for nonlinearity of the heat release response to imposed acoustic oscillations using phase-locked, two-dimensional OH PLIF imaging. It focuses upon two representative conditions from a larger test set, corresponding to fundamentally different mechanisms of nonlinearity in flame response. The first mechanism is vortex roll-up at large disturbance amplitudes, similar to the observations of Balachandran et al. [R. Balachandran, B.O. Ayoola, C.F. Kaminski, A.P. Dowling, E. Mastorakos, Combust. Flame 143 (2005) 37–55.]. This roll-up causes the destruction rate of flame surface area by flame propagation to grow with disturbance amplitude, resulting in a flame surface area which does not grow proportionately with the disturbance amplitude. The second mechanism is unsteady flame liftoff, which occurs during the phase of the cycle of peak instantaneous axial velocity. This causes the flame attachment point to move off of the center body to a downstream location for part of the cycle. During this part of the cycle, the flame surface area decreases due to a merging of flame branches. Interestingly, while the flow field is highly three-dimensional and non-axisymmetric, the two key mechanisms identified here are essentially axisymmetric in nature. Furthermore, both mechanisms of nonlinearity are ultimately due to reduction in flame area by flame propagation normal to itself.

Pressure and preheat dependence of laminar flame speeds of H2/CO/CO2/O2/He mixtures

Abstract: Laminar flame speeds of lean H2/CO/CO2 (syngas) fuel mixtures have been measured for a range of H2 levels (20–90% of the fuel) at pressures and reactant preheat temperatures relevant to gas turbine combustors (15 atm and up to 600 K) A conical flame stabilized on a contoured nozzle is used for the flame speed measurement, which is based on the reaction zone area calculated from chemiluminescence imaging of the flame An O2:He mixture (1:9 by volume) is used as the oxidizer in order to suppress the hydrodynamic and thermo-diffusive instabilities that become prominent at elevated pressure conditions for lean H2/CO fuel mixtures All the measurements are compared with numerical predictions based on two leading kinetic mechanisms: a H2/CO mechanism from Davis et al and a C1 mechanism from Li et al The results generally agree with the findings of an earlier study at atmospheric pressure: (1) for low H2 content ( 60%) H2 content fuels, especially at very lean conditions At elevated pressure, however, the effect is less pronounced than at atmospheric conditions The exaggerated temperature dependence of the current models may be due to errors in the temperature dependence used for so-called “low temperature” reactions that become more important as the preheat temperature is increased There is also evidence of slight radiative heat transfer effects on the laminar flame speed for lean syngas mixtures associated with CO2 addition to the fuel (up to 40%) at elevated pressure and preheat temperature

CH∗ chemiluminescence modeling for combustion diagnostics

Abstract: CH∗ chemiluminescence is often employed in combustion diagnostics, for example as a measure of heat release rate and for equivalence ratio sensing. However, most interpretations of CH∗ chemiluminescence rely either on heuristic arguments or empirical data gathered under limited conditions. More rigorous analysis is required to understand the effects of combustion conditions, e.g., pressure, reactant composition and preheat, strain and exhaust gas recirculation, on CH∗ chemiluminescence. Chemiluminescence modeling holds promise in this regard. The predictive accuracy of four proposed CH∗ chemiluminescence formation models were experimentally tested in premixed, methane–air and prevaporized Jet-A–air flames. Two of the models, based on CH∗ formation via reactions between C2H and O or O2, are able to predict the experimental data within the experimental uncertainty, in both room temperature methane and preheated Jet-A flames. The utility of CH∗ chemiluminescence for sensing heat release rate and equivalence ratio (ϕ), when combined with OH∗ chemiluminescence, is then analyzed in methane flames for varying pressure, preheat temperature and strain. The CH∗/OH∗ chemiluminescence ratio is found to be useful for sensing equivalence ratio in lean methane systems, but only at certain pressure and reactant temperature conditions. The relationship between CH∗ chemiluminescence and heat release varies with ϕ, pressure, temperature and strain. At high pressures, however, the dependence on ϕ and strain are small, making CH∗ attractive for heat release sensing applications in gas turbine combustors.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.