Real-Time Optical Smoke Meters

The SAE Aerospace Recommended Practice (ARP) 1179C is the regulatory method for determining the exhaust Smoke Number from jet engines. This methodology is slow and cumbersome and requires handling and analyzing paper filters which have been exposed to the jet engine exhaust effluent which has been transported via a sampling rake and heated sample lines. In Phase I, Advanced Fuel Research, Inc. successfully field-demonstrated an in-situ, non-intrusive optical-based method that correlated with the burdensome ARP. Also demonstrated was an optical-based extractive sampling cell for also measuring Smoke Number. Demonstration measurements on a J-85 turbojet with an 18-inch nozzle were successful. Extinction values over a broad range of smoke conditions correlated well with the traditional method, thus showing the potential of the optical method for real-time Smoke Number measurements. The plan for Phase II is to complete the design of two advanced prototypes, and then improve and document performance through field trials. These designs will benefit from a reduced number of optical components, thereby adding stability and simplifying installation in an engine test environment. Phase II will deliver two advanced prototypes and a draft Aerospace Information Report (AIR) for consideration as an alternative to the SAE ARP 1179C filter-paper method.