Exhaust Gas Trace Species Detection System for Turbine Engines

"Microdischarge based chemical sensing is a novel detection scheme that relies on extremely sensitive emission spectroscopy, without the need for expensive plasma sources and vacuum systems required in large scale plasmas. This technique provesparticularly powerful for metals detection due to strong emission spectra from metals in a discharge. Additionally, the sensors presented are small, rugged, and require very little power to operate. The detector is composed of the following components:a small discharge device (less than 1/100th of an inch) in which the chemical of interest is excited; a fiber optic coupler; and a small commercial spectrometer, which outputs data to a computer for analysis. The small size of these detectors makes themideal for incorporation on systems that have limited interference from the size and shape of the sensor, such as in aircraft turbine engines. Preliminary spectral analysis of mercury in a microdischarge has clearly shown that this technology is capable ofsensing 250 parts per billion of mercury in air with a signal to noise ration in excess of 10, and further sensitivity is anticipated with improved design. Caviton expects to achieve similar results with the detection of aluminum and nickel in engineexhaust. The products being developed at Caviton will provide the military with a new generation of small, sensitive, rugged sensors capable of detecting metals at parts per billion concentrations.