Beetles could prove a hit with the aircraft industry

A species of beetle that squirts its predators with a high-pressure spray of boiling liquid could provide the key to significant improvements in aircraft engine design.

The bombardier beetle defends itself by squirting predators (ants, frogs, spiders) with a high-pressure jet of boiling liquid in a rapid-fire action called pulse combustion.

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Professor Tom Eisner at Cornell University in the US discovered that, to do so, the beetle combines hydrogen peroxidase and hydroquinone in a tiny combustion chamber and, when these react, benzoquinone and steam are emitted in a jet at around 100 degrees Centigrade.

Now, scientists at the University of Leeds hope that by studying the mechanism further they can solve a problem that can occasionally with aircraft flying at high altitude – re-igniting a gas turbine aircraft engine which has cut out when the outside air temperature is as low as -50 degrees Centigrade!

In a new three-year project, they will set out to improve understanding of the beetle’s unique pulse combustion and nozzle ejection mechanism. The project also aims to identify how combustion engineers could exploit this understanding to practical effect. For example, knowledge gained could aid the development of a device that helps relight aircraft engines at high altitude by squirting plasma into the engine’s combustion chamber more accurately.

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The project will involve computer-based numerical and mathematical modelling. Initially, it will focus on understanding the beetle’s heart-shaped miniature combustion chamber, which is less than 1 millimetre long. Simulations for a larger chamber around a few centimetres long will then be conducted in which gases are ignited by raising the chamber’s surface temperature. The effect of different shaped nozzle outlets and explosion chambers will also be examined.

The project team will be led by Andy McIntosh, Professor of Thermodynamics and Combustion Theory at the Energy and Resources Research Institute in the University of Leeds.