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7 S e c t i o n II Project Plan and Approach II.1 Project Stages and Tests that the precision in the trends observed in the staged aircraft testing is robust, the operational testing can yield information Figure II-1 depicts the four stages of this project. The first about the in-use engine state (Herndon et al. 2009). This type stage involved developing a test matrix suitable for probing of data can also be used to investigate whether there are near- near-idle engine states using in-service aircraft engines. The field atmospheric processes that could skew or undermine second and fourth stages were conducted at a cold weather the effective use of an emissions inventory based exclusively airport in winter. For the third stage, the detailed probe work on exhaust plane characterization. was conducted at a warm weather airport. We quantified emissions from both staged aircraft and in-use aircraft. Staged aircraft tests involved running tests on II.2Test Venues, Temperatures, an out-of-service aircraft under controlled conditions using and Engines a test matrix developed specifically for this project. Testing An overview of the test venues, ambient temperatures, and was conducted using one of four exhaust sampling methods engines sampled is presented in Table II-1. In the MDW 2009 (three based on a one-meter probe and one using the mobile test, a subset of the complete instrument suite was deployed laboratory as a mobile probe). A total of 12 aircraft were to characterize engine exhaust using a preliminary version of sampled with this approach at three airport campaigns: MDW the test matrix that employed the mobile laboratory for sample 2009, DAL 2010, and MDW/ORD 2010. The analysis of these acquisition. test results form the basis of the temperature dependence of In the DAL 2009 test, the same subset of analytical equip- the near-idle HAP/VOC emission indices. ment was deployed, but the sampling probe developed by In addition to the staged aircraft sampling, the emissions Robert Howard (Arnold Engineering Development Center) from in-use aircraft were also quantified. These tests were was coupled to the probe stand developed by Phil Whitefield conducted in the provisional days at the end of each test, (Missouri University of Science and Technology). At DAL once the scheduled staged work was completed. To charac- 2009, various test protocols were used to compare and evaluate terize the VOC emissions of in-use aircraft, exhaust plumes sampling methodologies using a probe and stand situated were continuously sampled and analyzed using high-time- behind the aircraft engine. These included the use of a heated response instrumentation downwind of an active taxiway. transfer line, immediate dilution at the probe tip, and dilution This approach measures diluted engine exhaust plumes formed plus pressure drop. The same aircraft was also characterized under true operational conditions. Aircraft tail numbers were on an abbreviated test matrix using the mobile lab sampling recorded and matched to time-coded video records to allow methodology used in the first test. attribution of specific combustion plumes to the correspond- In the MDW 2010 test, a comprehensive set of instru- ing source engines. The in-use aircraft tests were conducted ments was used, including the instrumentation deployed by at various ambient temperatures and included a variety of the Pacific Northwest National Laboratory's Environmental aircraft engine types and taxiway operational throttle points. Molecular Sciences Laboratory. For the ORD 2010 test, the The analysis of the naturally diluted plume characterization mobile laboratory sampling method was used for two dif- produces a distribution of emission indices arising from air- ferent engine technologies (non-CFM56) that had not been craft operating with unknown fuel flow rates. To the extent previously studied.

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8 Table II-1. Testing overview. Test Engine Types Temperature CFM56-3B1 -8C to -4C Staged MDW 2009 CFM56-7B24 Airport Taxiway Various Staged CFM56-7B24 23C to 25C DAL 2009 Airport Runway Various Staged CFM56-7B24 -6C to -4C MDW 2010 Airport Taxiway Various V2527-A5 -3C to 2C Staged Figure II-1. Chronological ORD 2010 PW4090 depiction of the project Airport Taxiway stages. This project also seeks to construct an empirically based eters that influence the VOC emission index independently. model that will estimate VOC emissions as a function of fuel Following the description and quantification of the near-idle flow and ambient temperature. The methodology this work fuel flow dependence, the data related to the ambient tem- adopts is to treat fuel flow and ambient temperature as param- perature dependence will be discussed.