Analysis of Test-Cell Emission Measurements of Newly Overhauled Turbofan Engines

In this study, the gaseous emissions of newly overhauled CFM56-3B1 and -3B2 series turbofan engines are measured in a test-cell environment during typical functional and performance test procedures. The measured emissions are carbon dioxide, carbon monoxide, total hydrocarbons, and nitrogen oxides. A unique emissions sample system was used, where the sample probe was located behind the final stage of the low-pressure turbine rotor, avoiding having any bypass air or ambient air in the emissions. The emission production patterns are evaluated with the engine parameters of fan speed, fuel flow, and exhaust gas temperatures. Characterizing the concentrations and emission indices at stable power settings, the results also contribute to arguments on the effects of hot and cold idles, probe locations, and NO2/NOx ratios. Even though the present study differs from that of the International Civil Aviation Organization Aircraft Engine Emission Database in several respects, a comparison reveals relatively good agreement with regard to nitrogen oxides and reveals differences for carbon monoxide at low-power settings.