MICHAEL PHELAN / LONDON
The UK's University of Leeds is to study the natural combustion techniques of an unusual insect in a quest to improve turbine engine combustor performance.
The bombardier beetle squirts its predators with a high-pressure spray of boiling liquid in a process called "pulse combustion", and Andy McIntosh, professor of thermodynamics and combustion theory at the University of Leeds' energy and resources research institute, hopes that understanding the beetle's combustion technique will help refine traditionally inefficient high-altitude turbine relight techniques.
"Engine relights involve passing a huge electrical current across a gap in the combustion chamber to separate the fuel-air mixture into 'radicals'," he says. The tendency for the radicals to recombine quickly inhibits the efficiency and reliability of the process, however, and the challenge is to project the radicals far enough into the engine's combustion chamber to chemically induce re-ignition.
"We'd like to be able to project the jet about 100-200mm [4-8in] before recombination," says McIntosh, to ensure the best chance of re-ignition."
The bombardier beetle mixes hydrogen peroxidase and hydroquinone in a 1mm heart-shaped combustion chamber, and expels steam and quinones at around 100°C (212°F) in a 20mm jet from its anus. The beetle is far more efficient at producing such a jet than current re-igniters, and the shape of its combustion chamber and nozzle is thought to be a crucial factor.
The Leeds team are hoping to work out how the beetle is so efficient, and plan to simulate a larger 10-20mm combustion chamber, in which gases would be ignited by raising the chamber's surface temperature. Different chamber and nozzle shapes will be studied to produce the best jet results.
The three-year £135,000 ($235,000) study is due to begin in February next year, and will be fully funded by the UK Engineering and Physical Sciences Research Council. McIntosh is hopeful of industry interest once initial results are achieved.
Source: Flight International