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Beetles could prove a hit with the aircraft industry

December 08, 2003

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's unique natural combustion technique is being studied to see if it can be copied for use in the aircraft industry.

Scientists studying the bombardier beetle's jet-based defence mechanism hope it will help to solve a problem that can occasionally occur at high altitude - re-igniting a gas turbine aircraft engine which has cut out, when the outside air temperature is as low as minus
50 degrees Centigrade!

Due to start early next year, this innovative 3-year project at the University of Leeds is being funded by the Engineering and Physical Sciences Research Council (EPSRC).

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. Building on work by Professor Tom Eisner at Cornell University, the new project will set out to improve understanding of the beetle's unique pulse combustion and nozzle ejection mechanism. It 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.   

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. Professor McIntosh says: "The bombardier beetle's defence mechanism represents a very effective natural form of combustion. Copying such natural mechanisms is part of the growing field of biomimetics where scientists learn much from intricate design features already in nature. Understanding this beetle better could lead to significant advances in combustion research."

Notes for Editors:

The research initiative, "Learning from Controlled Explosions in Nature - Modelling the Catalytic Explosion Device of Bombardier Beetles", will receive funding from the EPSRC of nearly £135,000. The project is scheduled to begin in February 2004.

The series of repeated explosions involved in pulse combustion was used to power the Doodlebug V1 flying bomb of World War II. Each low-pressure part of the combustion cycle draws in more fuel, which is exploded in the high-pressure part of the cycle and ejected.

The liquid ejected by the bombardier beetle comprises mainly water mixed with quinones.

The project builds on biological research led by Professor Tom Eisner at Cornell University in the USA. This work discovered that the bombardier beetle combines hydrogen peroxidase and hydroquinone in a tiny combustion chamber and that, when these react, benzoquinone and steam are emitted in a jet at around 100 degrees Centigrade.

In preliminary studies, Professor McIntosh has already found that the shape of the bombardier beetle's tiny combustion chamber is very important in maximising the amount of material ejected for each explosion (about 300 explosions occur per second). The shape of the nozzle, which can swivel in any direction, is also critical.

The Engineering and Physical Sciences Research Council (EPSRC) is the UK's main agency for funding research in engineering and the physical sciences. EPSRC invests more than £500 million a year in research and postgraduate training to help the nation handle the next generation of technological change. The areas covered range from information technology to structural engineering, and from mathematics to materials science. This research forms the basis for future economic development in the UK and improvements in everyone's health, lifestyle and culture. EPSRC also actively promotes public awareness of science and engineering. EPSRC works alongside other Research Councils with responsibility for other areas of research. The Research Councils work collectively on issues of common concern via Research Councils UK. Website address for more information on EPSRC: www.epsrc.ac.uk/

Engineering and Physical Sciences Research Council (EPSRC)