Author(s)

N. Beheshti & A. C. McIntosh

Abstract

In this paper we describe an experimental rig which has been built as a result of inspiration from the bombardier beetle. This beetle is such that it has the capacity to fire a spray of hot water, steam and noxious chemicals from a nozzle at the rear end of its abdomen in any direction it wishes (even over its head). An example of controlled combustion in nature, it has led to first to simulations using CFD (computational fluid dynamics) of the spray system and the testing of an experimental rig replicating the physical process of the beetle system. The experiments verified the theories developed through the CFD simulations and produced excellent results that have important applications in different industries dealing with sprays such as drug delivery inhalers, fuel injectors and fire-fighting water mists. This novel spray technology has the trademark µMist. Keywords: sprays, mists, Bombardier beetles, biomimetics, flash evaporation, pharmaceutical, fire extinguishers, fuel injectors. 1 Introduction Bombardier beetles have a very remarkable defence mechanism. They spray a hot irritant aqueous solution onto their predators. This is done by an ingenious mechanism such that an aqueous solution of quinones is heated up to above its boiling point (by means of exothermic catalytic chemical reactions) in a combustion chamber which remarkably is less than 1mm in size. There are two such chambers each of which ejects the noxious mixture in the form of a steamy spray from one of the twin nozzles at its posterior. Among these beetles, the Brachina branch, and in particular some variants such as the African Stenaptinus

Keywords

sprays, mists, Bombardier beetles, biomimetics, flash evaporation,pharmaceutical, fire extinguishers, fuel injectors.