TY - JOUR
T1 - Transient radiative initiation of the heterogeneous flame in self-propagating high-temperature materials synthesis
T2 - 30th International Symposium on Combustion
AU - Makino, Atsushi
AU - Law, C. K.
N1 - Funding Information:
A.M. and C.K.L. were respectively supported by the Grant-in-Aid for Scientific Research of the Ministry of Education, Japan, and the Microgravity Combustion Program of NASA, USA.
PY - 2000
Y1 - 2000
N2 - Radiative initiation of a combustion wave in the self-propagating high-temperature materials synthesis (SHS) process was analyzed for a mixture compact by use of a heterogeneous theory which accounts for the premixed mode of bulk flame propagation as well as the nonpremixed mode of consumption of the non-metal (or higher-melting-point metal) particles. In the realistic limit of diffusion-controlled combustion, which nevertheless is still highly temperature sensitive because of the Arrhenius nature of mass diffusion, the analysis successfully identified the functional dependence of the various system parameters related to flame initiation on the particle size, a feature of which was not captured in previous theoretical works based on homogeneous flame propagation. Specifically, calculated results showed that the ignition delay increases with decreasing mixture ratio, increasing dilution, decreasing intensity and beam diameter of the heat flux, and increasing particle size. Furthermore, in the presence of heat loss which is inevitable, there also exist absolute ignition limits beyond which the mixture compact is not ignitable. Such nonignition events are manifested by the failure to either establish a combustion wave, for large particles or moderate heat fluxes, or sustain the propagation of an established wave even though the particle size is small and the heat flux is strong. Comparison with experimental data showed satisfactory agreement, both qualitatively and quantitatively, thereby substantiating the viability of the present heterogeneous theory of flame initiation.
AB - Radiative initiation of a combustion wave in the self-propagating high-temperature materials synthesis (SHS) process was analyzed for a mixture compact by use of a heterogeneous theory which accounts for the premixed mode of bulk flame propagation as well as the nonpremixed mode of consumption of the non-metal (or higher-melting-point metal) particles. In the realistic limit of diffusion-controlled combustion, which nevertheless is still highly temperature sensitive because of the Arrhenius nature of mass diffusion, the analysis successfully identified the functional dependence of the various system parameters related to flame initiation on the particle size, a feature of which was not captured in previous theoretical works based on homogeneous flame propagation. Specifically, calculated results showed that the ignition delay increases with decreasing mixture ratio, increasing dilution, decreasing intensity and beam diameter of the heat flux, and increasing particle size. Furthermore, in the presence of heat loss which is inevitable, there also exist absolute ignition limits beyond which the mixture compact is not ignitable. Such nonignition events are manifested by the failure to either establish a combustion wave, for large particles or moderate heat fluxes, or sustain the propagation of an established wave even though the particle size is small and the heat flux is strong. Comparison with experimental data showed satisfactory agreement, both qualitatively and quantitatively, thereby substantiating the viability of the present heterogeneous theory of flame initiation.
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U2 - 10.1016/S0082-0784(00)80360-4
DO - 10.1016/S0082-0784(00)80360-4
M3 - Conference article
AN - SCOPUS:84939779209
SN - 1540-7489
VL - 28
SP - 1439
EP - 1446
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
Y2 - 25 July 2004 through 30 July 2004
ER -