UV Absorption Technique for Monitoring Mobile Source NO Emissions

Abstract : Ultraviolet (UV) absorption techniques developed and used by the Arnold Engineering Development Center (AEDC) for measurements of nitric oxide (NO) in exhaust flows of turbine and liquid-propellant rocket engines have been adapted for measurements of NO in the exhausts of automobiles. Measurements were performed across a roadway with a 10-percent mixture of NO being released into the exhaust stream of a small truck traveling at speeds ranging from 6 to 30 mph. Emission factors for these simulated exhausts ranged from 0.92 to 23.05 gm/ mi. Nitric oxide was detected in measurements using NO-resonance lamp radiation passed twice across the roadway for emission factors as low as 1.78 gm/mi. Nitric oxide absorption was not detected on exhaust measurements of automobiles traveling (coasting) at constant speeds. Nitric oxide was detected at measurable levels on automobiles forced to stop and then accelerate through the measurement station.