Combustion of the Silicon-Red Lead System. Temperature of Burning, Kinetic Analysis and Mathematical Model

Abstract

The results of both experimental and theoretical research on the Silicon-Red Lead pyrotechnic system are reported. The overall aim of the study was to investigate burning temperatures and to model mathematically the combustion behavior of this system.

The maximum burning temperatures of various Silicon-Red Lead compositions have been evaluated by means of thermocouples embedded in the burning mixtures. The measured temperature-time curves were first extrapolated to zero size of the thermocouple junctions and then used for determining the maximum temperatures of combustion.

Because the probes used were not capable of withstanding the high temperatures produced by compositions containing less than 45 mass % of silicon, a computer program was used to calculate their theoretical adiabatic combustion temperatures.

The results obtained showed that, in the range of composition from 25 to 55% Si, decreasing the fuel content caused higher burning temperatures. This general tendency became more complicated for those compositions where large quantities of heat were absorbed during phase transitions occurring in the samples. Calculated theoretical temperatures of combustion were higher than those measured.

Based on the results of the temperature profile measurements, kinetic parameters for the processes occurring during combustion of the Silicon-Red Lead system have been estimated. Two mathematical approaches, referred as Boddington and Zenin methods, have been used for the analysis of the temperature profiles. A comparison of the results showed only minor differences caused by inequality of the methods.

Also results of thermal conductivity and specific heat capacity measurements are reported.

The obtained kinetic information has been utilized in a simple mathematical model designed to predict the propagation of combustion waves in gasless pyrotechnic compositions. The model has been used to study the effects of chemical composition, exothermicity and ambient temperature on burning rates of the Silicon-Red Lead system. Results obtained show that the model reproduces reasonably well the observed trends in burning velocity.

Keywords:

• pyrotechnic
• silicon
• red lead
• burning temperature
• temperature profile analysis
• kinetics
• specific heat capacity
• thermal conductivity
• mathematical model