The efficiency of the explosive discharge of the bombardier beetle, with possible biomimetic applications

摘要

The paper investigates the remarkable combustion chamber of the bombardier beetle with a view to learning from the great efficiency of blast that the 1mm combustion chamber of this creature achieves with repeated explosions at 2-3 per ms. In reality the two chemicals are trace species in water which is then heated to boiling point by the presence of a catalyst. To simplify the numerical study presented here, a two-phase (water / steam) computation is performed to simulate the hot discharge from the brachinine bombardier beetle. The study only concentrates on the heating process within the reaction chamber rather than modelling the full kinetics of the hydroquinone and hydrogen peroxide reaction (with catalysts catalase and peroxidase). Using this approach the numerical model (based on commercial CFX software) simulates the heat generation by following an artificially assigned scalar injected from the wall. The heat assigned to the scalar then converts some of the water by pool boiling into steam. The subsequent pressure increase in the two-phase system is modelled, and the ejection of the hot mixture up to the point of emergence is discussed and evaluated for different geometrical configurations. The aim of the study is to show the advantages of the naturally occurring design and identify the main parameters important for the high efficiency discharge. The results indicate that this rather unusual design of beetle combustion chamber does indeed have better performance in terms of efficiency of mass ejection. This is primarily due to the heart shaped combustor combined with a long narrow ejection tube. The results support the idea of a possible practical use for pilot ignition systems, such as re-igniters in aircraft gas turbines and automobile safety air bag ignition devices.