MEASUREMENT OF NO AND NOY EMISSION INDEXES DURING SUCCESS

Exhaust measurements in the wake vortex regime of the NASA Boeing 757 aircraft were made during the SUbsonic aircraft: Contrails and Cloud E ffects Special Study. Emission indices for NO and NOy were calculated from in situ measurements taken on board the NASA DC-8 for plumes aged 20 - 300 seconds. The average NO emission index is 7.5 g NO2/kg fuel for mean conditions of 37 kft altitude, 0.7 Mach and 0.34 kg/s fuel fl ow rate. Comparison is made between measured indices and predictions b ased on ground engine test data and a fuel flow model. Measurements ar e positively correlated but are on average 22% higher than predictions , with considerable scatter and systematic deviations in measurements made under low thrust conditions. These conditions are lower than typi cal in commercial cruise operation of the 757, for which the model was optimized. No statistically significant change in nitrogenous emissio ns is observed for an order of magnitude change in fuel sulfur content . Estimation of the NO2 from photochemical calculations implies a cont ribution to NOx of 5-19%. Examination of exhaust composition shows tha t 95% of the NOy is in the form of NOx.