Bibliography - T. F. Lu
- Seshadri, K., T. F. Lu, O. Herbinet, S. Humer, U. Niemann, W. J. Pitz, R. Seiser, and Chung K Law, 2009: Experimental and kinetic modeling study of extinction and ignition of methyl decanoate in laminar nonpremixed flows. Proceedings of the Combustion Institute, 3(1), doi:10.1016/j.proci.2008.06.215 1067-1074
[ Abstract ]Methyl decanoate is a large methyl ester that can be used as a surrogate for biodiesel. In this experimental and computational study, the combustion of methyl decanoate was investigated in non-premixed, nonuniform flows. Experiments were performed employing the counterflow configuration with a fuel stream made up of vaporized methyl decanoate and nitrogen, and an oxidizer stream of air. The mass fraction of fuel in the fuel stream was measured as a function of the strain rate at extinction, and critical conditions of ignition were measured in terms of the temperature of the oxidizer stream as a function of the strain rate. A detailed mechanism of 8555 elementary reactions and 3036 species has been developed previously to describe combustion of methyl decanoate. Since it is not possible to use this detailed mechanism to simulate the counterflow flames because the number of species and reactions is too large to employ with current flame codes and computer resources, a skeletal mechanism was deduced from this detailed mechanism using the "directed relation graph" method. This skeletal mechanism has only 713 elementary reactions and 125 species. Critical conditions of extinction and critical conditions of ignition were calculated using this skeletal mechanism and they were found to agree well with experimental data. In general, the methyl decanoate mechanism provides a realistic kinetic tool for simulation of biodiesel fuels.
- Law, Chung K., A. Makino, and T. F. Lu, 2006: On the off-stoichiometric peaking of adiabatic flame temperature. Combustion and Flame, 145(4), doi:10.1016/j.combustflame.2006.01.009 808-819
[ Abstract ]The characteristic rich shifting of the maximum adiabatic flame temperature from the stoichiometric value for
mixtures of hydrocarbon and air is demonstrated to be caused by product dissociation and hence reduced amount
of heat release. Since the extent of dissociation is greater on the lean side as a result of the stoichiometry of
dissociated products, the peaking occurs on the rich side. The specific heat per unit mass of the mixture is shown
to increase monotonically with increasing fuel concentration, and as such tends to shift the peak toward the lean
side. It is further shown that this is the cause for the lean shifting of the adiabatic flame temperature of oxidizerenriched
mixtures of NmHn and F2 and of NH3 and O2, with various amounts of inert dilution, even though their
maximum heat release still peaks on the rich side.
- Lu, T. F., and Chung K Law, 2006: Linear-Time Reduction of Large Kinetic Mechanisms with Directed Relation Graph: n-Heptane and iso-Octane. Combustion and Flame, 144(1-2), doi:10.1016/j.combustflame.2005.02.015 24-36
[ Abstract ]The algorithm of directed relation graph recently developed for skeletal mechanism reduction was extended to
overall linear time operation, thereby greatly facilitating the computational effort in mechanism reduction, particularly
for those involving large mechanisms. Together with a two-stage reduction strategy and using the kinetic
responses of autoignition and perfectly stirred reactor (PSR) with extensive parametric variations as the criteria
in eliminating unimportant species, a detailed 561-species n-heptane mechanism and a detailed 857-species
iso-octane mechanism were successfully reduced to skeletal mechanisms consisting of 188 and 233 species,
respectively. These skeletal mechanisms were demonstrated to mimic well the performance of the detailed mechanisms,
not only for the autoignition and PSR systems based on which the reduced mechanisms were developed
but also for the independent system of jet-stirred reactor. It was further observed that the accuracy of calculated
species concentrations was equivalently bounded by the user-specified error threshold value and that the reduction
time for a single reaction state is only about 50 ms for the large iso-octane mechanism.
- Lu, T. F., and Chung K Law, 2005: A Directed Relation Graph Method for Mechanism Reduction. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.145 1333-1341
[ Abstract ]A systematic approach for mechanism reduction was developed and demonstrated. The approach consists
of the generation of skeletal mechanisms from detailed mechanism using directed relation graph with
specified accuracy requirement, and the subsequent generation of reduced mechanisms from the skeletal
mechanisms using computational singular perturbation based on the assumption of quasi-steady-state species.
Both stages of generation are guided by the performance of PSR for high-temperature chemistry and
auto-ignition delay for low- to moderately high-temperature chemistry. The demonstration was performed
for a detailed ethylene oxidation mechanism consisting of 70 species and 463 elementary reactions, resulting
in a specific skeletal mechanism consisting of 33 species and 205 elementary reactions, and a specific
reduced mechanism consisting of 20 species and 16 global reactions. Calculations for laminar flame speeds
and nonpremixed counterflow ignition using either the skeletal mechanism or the reduced mechanism show
very close agreement with those obtained by using the detailed mechanism over wide parametric ranges of
pressure, temperature, and equivalence ratio.
- Zheng, X. L., T. F. Lu, Chung K Law, C. K. Westbrook, and H. J. Curran, 2005: Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.241 1101-1109
[ Abstract ]The ignition temperature of nitrogen-diluted dimethyl ether (DME) by heated air in counterflow was
experimentally determined for DME concentration from 5.9% to 30%, system pressure from 1.5 to
3.0 atm, and pressure-weighted strain rate from 110 to 170 s-1. These experimental data were compared
with two mechanisms that were, respectively, available in 1998 and 2003, with the latter being a substantially
updated version of the former. The comparison showed that while the 1998-mechanism uniformly
over-predicted the ignition temperature, the 2003-mechanism yielded a surprisingly close agreement for
all experimental data. Sensitivity analysis for the near-ignition state based on both mechanisms identified
the deficiencies of the 1998-mechanism, in particular, the specifics of the low-temperature cool flame chemistry
in effecting ignition at higher temperatures, as the fuel stream is being progressively heated from its
cold boundary to the high-temperature ignition region around the hot-stream boundary. The 2003-mechanism,
consisting of 79 species and 398 elementary reactions, was then systematically simplified by using
the directed relation graph method to a skeletal mechanism of 49 species and 251 elementary reactions,
which in turn was simplified further by using computational singular perturbation method and quasisteady-
state species assumption to a reduced mechanism consisting of 33 species and 28 lumped reactions.
It was demonstrated that both the skeletal and reduced mechanisms mimicked the performance of the
detailed mechanism with high accuracy.
Direct link to page: http://cmi.princeton.edu/bibliography/results.php?author=3915
