Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
25 This project has assessed the temperature dependence of idling aircraft engine emissions for selected variants of the CFM56 engine type. The project has characterized engine emissions of on-wing commercial aircraft (equipped with CFM56-7B24 engines) and explored the impact of fuel flows below the ICAO reference fuel flow rate for idle. The test matrix development process incorporated airline guidance on which fuel flow rates would be representative of actual idle phase during routine operation. The projectâs results, together with data from other sources, have been assimilated into an empirical model that strives to describe the temperature and fuel flow dependence for near- idle VOC emissions. The model described in this work is only appropriately applied to idling aircraft engines and ambient temperatures between 260K and 310K (8°F to 98°F). It is currently based on the observations of the CFM56 engine. The project has proposed a framework for data assimilation that can tie future observations to ICAO certification data. The approach described in this study can be used to estimate emissions during airport operations in the context of scenario analysis. The simple model described in this work can be used to help quantify the emissions benefit from proposed improvements to terminal area and taxiway operational protocols. Based on the observed temperature dependence, it is clear that practices that limit the amount of excess time spent at idle during the winter months will significantly limit the HAP emissions burden. This project has completed the following for the CFM56- 7B24 engine: ⢠Developed empirical corrections for fuel flow and tem- perature; ⢠Demonstrated applicability of the corrections to both individual VOC species and UHC; ⢠Corroborated the near-idle VOC scaling effect (described in Section VI.2); ⢠Demonstrated that emissions of HAP species can be esti- mated using the EPA Speciate profile with the ICAO data- bank UHC emissions performance value; and ⢠Provided a tool for airport operators to compute near-idle HAP and VOC emissions as a function of ambient tempera- ture and airport operational conditions. The results from this study can be applied in detailed anal- ysis to study the HAP/VOC emissions trade-offs for a variety of scenarios, such as the following: ⢠Optimizing the takeoff queue length during operational pushes, ⢠Quantifying the benefit of switching to APU during cold weather ground stop, and ⢠Assessing HAP and VOC benefits from single engine taxiing. S e c t i o n V i i Applicability to Airport Practice
