Calculating the heat of explosion for non-ideal explosives

Abstract

Non-ideal explosives are typically highly porous, low-density heterogeneous materials. They differ from ideal explosives in that fuel and oxidiser are separated at the molecular level. As such, non-ideal explosives demonstrate lower detonation pressures and velocities than ideal explosives, with more extended detonation reaction zones. These longer detonation reaction zones produce higher heat of explosion due to secondary and tertiary combustion reactions occurring behind the detonation front. Non-ideal explosives are increasingly used as homemade explosives (HME), and it is often challenging to determine likely performance without detailed chemical analysis, or an understanding of loading density, critical diameter, and stoichiometry. Detailed analysis is not an option in security-related settings where preservation of life and property is often challenged by time. Using Hess’ law of enthalpy, and empirical and quantitative thermochemical methods to determine the products of detonation, this paper introduces a simple method to determine the heat of explosion of any non-ideal explosive composition during three specific stages: anoxic detonation; anaerobic combustion; and aerobic combustion. The values calculated compare favourably to heats of explosion for non-ideal explosives published in open-source literature, suggesting that the approach can be developed into a user-friendly application for first responders.