Non-intrusive Optical Smoke Meter for Turbine Emission

Military and Civil standards (SAE ARP 1179B, ICAO Annex 16 Volume II) for aircraft gas turbine engine smoke emissions are based upon an essentially manual extractive probe sampling method with off-line sample analysis and data processing. These standards,which are similar, were designed to demonstrate compliance with regulatory standards for plume opacity or visibility and were specifically developed because of the widespread use of similar techniques throughout the industry and, most particularly, becauseof the absence of a viable or suitable opacity measuring device. These methods have been demonstrated to be fairly reliable and repeatable over more than three decades of use but they continue to be problematic in that they are slow, testing isexpensive, they require highly trained sophisticated operators and they do not provide a direct measure of the parameters of interest, either plume opacity or carbon (particulate) loading. A rapid, low-cost, non-intrusive method for measuring smoke numberis desirable. An extension of classical optical transmissometry is proposed for directly measuring turbine smoke number. The proposed system is designed for use in detecting absorbing gas stream from an aircraft turbine engine. The measurement techniqueand instrumentation are entirely non-intrusive to the emission gas stream. The necessary optical components can be located a few meters apart on opposite sides of the emission stream; the proposed set-up is simple and extremely rugged for the harsh engineenvironment. Alignment to achieve sufficient accuracy can be done simply by eye. The result of the measurement is shown to be directly proportional to the conventional definition of smoke number SN, a not surprising result since