The understanding of blast loads is critical for the development of infrastructure that protects against explosions. However, the lack of high-quality experimental work on the characterisation of such loads prevents a better understanding of many scenarios. Blast loads are typically characterised by use of some form of pressure gauge, from which the temperature can be inferred from a pressure measurement. However, such an approach to temperature measurement is limited; it assumes ideal gas laws apply throughout, which may not be the case for high temperature and pressure scenarios. In contrast, infrared radiation thermometers (IRTs) perform a measurement of temperature based upon the emitted radiance from the target object. The IRTs can measure fast changes in transient temperature, making them seemingly ideal for the measurement of a fireball’s temperature. In this work, we present the use of a high-speed IRT for the measurement of early-stage explosive development and fireball expansion within a confined blast, with the temperature of the explosive fireball measured from its emitted radiance. The temperature measured by the IRT was corroborated against the temperature inferred from a pressure gauge measurement; both instruments measured the same temperature from the quasi-static pressure (QSP) point onwards. Before the QSP point, it is deduced that the IRT measures the average temperature of the fireball over a wide field-of-view (FOV), as opposed to that inferred from the singular shocks detected by the pressure gauge. Therefore, use of an IRT, in tandem with a pressure gauge, provides a potential invaluable measurement technique for the characterisation the early stages of a fireball as it develops and expands.
A significant amount of scientific effort has been dedicated to measuring and understanding the effects of explosions, leading to the development of semi-empirical methods for rapid prediction of blast load parameters. The most well-known of these, termed the Kingery and Bulmash method, makes use of polylogarithmic curves derived from a compilation of medium to large scale experimental tests performed over many decades. However, there is still no general consensus on the accuracy and validity of this approach, despite some researchers reporting consistently high levels of agreement. Further, it is still not known whether blast loading can be considered deterministic, or whether it is intrinsically variable, the extent of this variability, and the range and scales over which these variations are observed. This article critically reviews historic and contemporary blast experiments, including newly generated arena tests with RDX and PETN-based explosives, with a view to demonstrating the accuracy with which blast load parameters can be predicted using semi-empirical approaches.
Accurate modelling of free-field detonations needs to account for both the initial energy release and gas generation, and the subsequent reaction of the initial detonation products with external oxygen. An upper limit for the extent of ‘afterburn’ can be ascertained from comparison of contained blasts in reactive (air) and inert (nitrogen) bath gases. The peak quasistatic pressures (QSP) and the gas phase products were determined in a 0.276 m3 blast chamber following detonations of the plastic explosive PE4. The experimental observations were compared to predictions based on standard models, CEA and EXPLO5. The best agreement between models and experiment, for both products and QSPs, was obtained from the Springall-Roberts treatment of detonation products in nitrogen, and complete combustion of these in air.
Accurate modelling of free-field detonations needs to account for both the initial energy release and gas generation, and the subsequent reaction of the initial detonation products with external oxygen. An upper limit for the extent of ‘afterburn’ can be ascertained from comparison of contained blasts in reactive (air) and inert (nitrogen) bath gases. The peak quasistatic pressures (QSP) and the gas phase products were determined in a 0.276 m3 blast chamber following detonations of the plastic explosive PE4. The experimental observations were compared to predictions based on standard models, CEA and EXPLO5. The best agreement between models and experiment, for both products and QSPs, was obtained from the Springall-Roberts treatment of detonation products in nitrogen, and complete combustion of these in air.
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