Research Fellows Directory
Dr John Black
Work on the interaction of a low cost, compact continuous wave laser with aerosols of absorbing nanoparticles such as soot in flames and in aero-engine exhausts has continued. Three publications in scientific journals are in preparation. As well as detection and measurement of particles concentration by observing light emitted by laser heated particles (Laser-Induced Incandescence - LII) other processes have been observed when continuous lasers are used. These include particle trapping in the laser beam, which enables measurement of very low concentrations of black carbon and other absorbing species present in ambient air, and photophoresis, the movemen of particles induced by the laser beam. An increase of chemical reaction rates in flames through coupling of laser energy into the gas flow via particle heating has been studied. This effect has potential applications in laser ignition which may improve the efficiency and emissions characteristics of car engines and improve high altitude relight capability of aero-engines.
A test on an aero-engine with two standards of fuel injectors installed in the same annular combustor showed that small changes in the amount of soot emitted by individual fuel injectors can be detected by examining the soot distribution pattern in the exhaust using LII equipment placed 3 m outside the exhaust flow. This confirms the potential of non-intrusive LII as a technique for engine health monitoring - the ability to detect faults developing in specifiic parts of the engine well in advance of failure - which does not require any engine mounted sensors or internal inspection of the engine and which can be installed in any maintenance facility.
Investigations of the use of the RGB colour capability of a standard digital camera to record the emission spectum of flames and of laser heated soot continues. Processing of digital camera images of LII recorded during the aero-engine test continues.