Measurement of Gaseous HAP Emissions from Idling Aircraft as a Function of Engine and Ambient Conditions (2012)

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28 Introduction Staged tests were performed with both a stationary one-meter probe or by using the Aerodyne Mobile Laboratory as a mobile probe driving through the exhaust plume with a prevailing headwind. Staged tests performed at DAL 2009 and MDW 2010 provided an opportunity to test with a one-meter probe placed directly behind and engine operating at various ground idle conditions. Tests performed on the taxiways of all three airports visited under this project allowed measure- ments of exhaust plumes after natural dilution. In these latter measurements specific information on the engine operating conditions is not known, however this constitutes a dataset comprised of a multitude of different engines sampled while in-use. The testing from DAL 2009 can be compared to testing at MDW and ORD to get comparison of emissions at dif- ferent ambient temperatures. DAL 2009 was conducted with warm ambient temperatures (24°C) while MDW and ORD tests were performed during the winter (-5°C). The dataset produced from this project is described in this appendix. The dataset is available as an excel format spreadsheet. A01—Staged Aircraft Testing from the MDW 2009 Mission The testing conducted during the MDW 2009 mission involved staging four Boeing 737 aircraft on two separate early mornings where the weather forecast called for cool precipitation free conditions. A single 737-300 and three 737-700 were tested. The 737-700 aircraft were equipped with a digital flight data record system that specified the engine state during the test. The 737-700 aircraft tested were equipped with CFM56-7B22 engines that had been upgraded via software to perform as a CFM56-7B24 engine type. This section of the Appendix will briefly discuss the sam- pling and analysis method before discussing the results of the MDW 2009 measurement campaign. Sampling and Analysis Methodology Figure A01-1 depicts a schematic of the methodology used to sample engine emissions during the MDW 2009 quick look study. In this approach, the aircraft engine is not operated above N1 = 25% (CFM56-7B24), which ensures that the engine thrust does not damage the mobile laboratory in the thrust wake. The air mass, sampled continuously, consists of a dynamic mixture of core-flow emissions mixed with an unknown and dynamically varying dilution fraction. The measurement as a function of time can be described by the following equation. X f X measured post combustion core emiss[ ] = × [ ] − − − ion ambientf X+ −( ) × [ ]1 ( )A-1 The method used to distinguish the core-flow plume constituents from the ambient is based on time series analy- sis (Herndon et al. 2004). The measurement at each of the continuous instruments will be a comprised of a mixture of core-flow combustion and ambient mixing ratios. In expression (A-1), f represents the time dependent volume fraction of core flow that is being sampled. The quantity f(t) is modulated by the engine by-pass flow turbulently mixing with the atmospheric shear field. Should f(t) be zero for an entire sampling period, there will be no capacity to estimate [X]post-combustion-core-emission with the dataset. To illustrate how (A-1) has been used to deduce [X]post-combustion-core-emission the time series for multiple measured quantities are used. The apparent baseline magnitudes for each of these species are equivalent to the ambient values measured when the mobile lab is outside of the engine flow (e.g., upwind of the aircraft) or when a crosswind compo- nent is pushing the engine core flow away from the sample location. Using equation (A-1) for compounds such as those in Figure A01-2, it can be shown that for a time series contain- ing time periods from non zero values of f(t) the relationship A p p e n d i x A Project Results

29 between two species, as X in (A-1) in the exhaust can be deter- mined by, a a b b measured ambient measured ambien [ ] − [ ] [ ] − [ ] t post combustion core emission ambi a a = [ ] − [ ] − − − ent post combustion core emission amb b b [ ] − [ ] − − − ient m= ( )A-2 If the time response of both species a and b is matched in time and any potential lag between the two measurements accounted for, when the measurement of a is plotted against the measurement of b, for a time interval that contains non- zero f(t) a linear fit of the correlation plot will yield a slope, m, in (A-2). The slope of the fit of HCHO with respect to CO2 (depicted in Figure A01-3) is 0.75±0.02 with units of ppbv pppm-1 (R2 = 0.98) where the error bar tabulated is twice the standard error of the slope parameter. The slope is related to the desired quantity, the emis- sion ratio of a (depicted in Figure A01-3 as HCHO) to CO2 (labeled b in the formulas) in the post-combustion-exhaust by rearranging without approximation to yield equation (A-3). a b post combustion core emission post com [ ] [ ] − − − − bustion core emission ambient post m b b − − = − [ ] [ ]1 − − −     + [ ] combustion core emission ambient a b post combustion core emission[ ] − − − ( )A-3 In the case of using CO2 to act as the dilution tracer the following limits can be used to estimate the systematic error inherent to this approach by making the reasonable assump- tion that the CO2 in the core flow is 2% (or 20,000 ppmv) and CO2 in the ambient is ~390 ppmv. a b post combustion core emission post com [ ] [ ] − − − − bustion core emission m ppmv ppmv − − = −1 390 20 000,     + [ ]a ppmv ambient 20 000, ( )A-3a The first term in this expression suggests that the error introduced by assuming that m is equivalent to the ratio of Figure A01-1. Sampling Scheme using the mobile laboratory inlet as the exhaust probe. Figure A01-2. Example time series of CO2, CO, formaldehyde and ethene during a plume encounter at MDW (2009). Figure A01-3. Correlation plot of HCHO and CO2 from MDW 2009 testing.

30 the a to CO2 in the core flow is less than 2%. The second term in this expression depends on the magnitude of [a]ambient which is compound specific, however it can be asserted that this error is much less than 0.01% for CO and the hydrocarbon compounds. An uncorrected application of the methodology of com- pound slopes diluted to an unknown extent in the ambient, systematically biases calculated emission indices high by 1.7 to 2.1% for aircraft exhaust emissions when the CO2 core flow is ~1.9 to 2.2% by volume and the species being studied is present in the ambient at less than 1 ppmv. Results from CFM56-7B24 MDW 2009, DAL 2010 and MDW 2010 Testing The results from the testing conducted where the digital flight data record is available are tabulated and depicted below. The table and figure numbers have been generated based on the engine test in question. The number following the letter E denotes which engine index is associated with the test result. At the request of the cooperating airline, the associated aircraft tail number and additional information is available by special request only and not part of the public release of this project. Table A01-E1a. Selected test results for engine SA001 (MDW2009), aircraft test conducted from 3/3/09 04:00 to 3/3/09 05:00, ambient temperature 266.91K, relative humidity 71%. Fuel Flow 2σ N1 2σ CO EI S FID EI 2σ kg s -1 kg s -1 % % g kg -1 g kg -1 g kg -1 g kg -1 0.0910 20.900 0.000 78.340 0.800 8.170 0.410 0.0985 0.0007 20.650 0.071 73.955 0.616 8.275 0.502 0.1050 0.0014 25.000 0.141 56.055 0.895 6.030 0.439 Engine SA_001 Fuel Flow 2σ C 2 H 4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s -1 kg s -1 g kg -1 g kg -1 g kg -1 g kg -1 g kg -1 g kg -1 0.0910 2.990 0.010 2.480 0.050 0.270 0.007 0.0985 0.0007 2.450 0.098 2.155 0.055 0.215 0.006 0.1050 0.0014 1.785 0.063 1.630 0.028 0.160 0.006 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.091 0.173 0.003 0.166 0.003 0.113 0.003 0.0985 0.0007 0.137 0.004 0.122 0.005 0.102 0.002 0.105 0.0014 0.111 0.002 0.112 0.004 0.087 0.004 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

31 Figure A01-E1b. Emission Index for engine SA001 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA-001. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

32 Figure A01-E1c. Emission Index for engine SA001 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA-001. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

33 Figure A01-E1d. Emission Index for engine SA001 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 1. Table A01-E2a. Selected test results for engine SA002 (MDW 2009). Aircraft test conducted from 3/3/09 04:00 to 3/3/09 05:00, ambient temperature 266.91K, relative humidity 71%. Fuel Flow 2σ N1 2σ CO EI 2σ FID EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 g kg-1 g kg-1 0.0828 0.0004 21.320 0.130 76.0 1 9.7 0.75 0.0910 21.200 0.000 71.25 0.4 9.0 0.29 0.0965 0.0007 23.000 2.970 63.1 4 7.5 0.67 0.1030 26.100 0.000 55.3 1.1 7.5 0.50 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0828 0.0004 2.616 0.07 2.21 0.05 0.242 0.007 0.0910 2.190 0.01 1.99 0.03 0.210 0.006 0.0965 0.0007 1.875 0.06 1.70 0.07 0.175 0.006 0.1030 1.570 0.02 1.44 0.05 0.160 0.008 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0828 0.0004 0.158 0.005 0.163 0.007 0.101 0.005 0.0910 0.132 0.002 0.136 0.002 0.088 0.001 0.0965 0.0007 0.112 0.002 0.119 0.010 0.086 0.009 0.1030 0.100 0.003 0.116 0.003 0.083 0.003 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

34 Figure A01-E2b. Emission Index for engine SA002 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA-002. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

35 Figure A01-E2c. Emission Index for engine SA002 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA002. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

36 Figure A01-E2d. Emission Index for engine SA002 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 2. Table A01-E3a. Selected test results for engine SA003 (MDW 2009). Aircraft test conducted from 3/4/09 03:45 to 3/4/09 04:30, ambient temperature 270.81K, relative humidity 53%. Fuel Flow 2σ N1 2σ CO EI s FID EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 g kg-1 g kg-1 0.0830 20.70 67.5 1.7 6.7 1.4 0.0895 0.0007 20.30 0.14 72.0 0.9 9.5 1.4 0.0953 0.0006 20.10 70.4 1.2 7.6 1.0 0.1020 25.20 38.2 0.4 3.2 0.2 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0830 1.880 0.020 1.74 0.06 0.200 0.014 0.0895 0.0007 2.155 0.046 1.99 0.06 0.240 0.011 0.0953 0.0006 2.147 0.031 1.93 0.05 0.230 0.015 0.1020 0.620 0.010 0.77 0.06 0.090 0.003 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0830 0.123 0.006 0.076 0.006 0.112 0.013 0.0895 0.0007 0.134 0.002 0.094 0.003 0.116 0.006 0.0953 0.0006 0.128 0.005 0.085 0.005 0.120 0.011 0.1020 0.051 0.001 0.039 0.001 0.093 0.003 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

37 Figure A01-E3b. Emission Index for engine SA003 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA003. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

38 Figure A01-E3c. Emission Index for engine SA003 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA003. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

39 Figure A01-E3d. Emission Index for engine SA003 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 3. Table A01-E4a. Selected test results for engine SA004 (MDW 2009). Aircraft test conducted from 3/4/09 03:45 to 3/4/09 04:30, ambient temperature 270.81K, relative humidity 53%. Fuel Flow 2σ N1 2σ CO EI 2σ FID EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 g kg-1 g kg-1 0.0810 0.0000 20.75 0.07 77.625 1.277 9.260 1.314 0.0920 0.0000 21.20 0.00 78.260 1.070 10.150 0.450 0.0945 0.0007 20.40 0.14 69.400 0.677 7.765 0.713 0.1020 0.0000 25.30 0.00 46.710 0.760 4.470 0.620 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0810 0 2.510 0.083 2.215 0.049 0.270 0.012 0.0920 0 2.520 0.020 2.210 0.030 0.290 0.009 0.0945 0.0007 2.070 0.026 1.865 0.027 0.220 0.011 0.1020 0 1.100 0.010 1.150 0.010 0.130 0.009 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0810 0.0000 0.149 0.007 0.113 0.004 0.096 0.005 0.0920 0.0000 0.163 0.004 0.130 0.003 0.096 0.003 0.0945 0.0007 0.120 0.003 0.083 0.003 0.097 0.005 0.1020 0.0000 0.070 0.003 0.047 0.003 0.068 0.005 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

40 Figure A01-E4b. Emission Index for engine SA004 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA004. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

41 Figure A01-E4c. Emission Index for engine SA004 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA004. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

42 Figure A01-E4d. Emission Index for engine SA004 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 4. Table A01-E7a. Selected test results for engine SA007 (MDW 2009). Aircraft test conducted from 3/4/09 04:50 to 3/4/09 05:30, ambient temperature 270.81K, relative humidity 56%. Fuel Flow 2σ N1 2σ CO EI s FID EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 g kg-1 g kg-1 0.0860 20.90 0.00 71.490 1.540 8.950 0.690 0.0938 0.001 20.32 0.15 75.320 2.087 8.283 1.397 0.0990 20.10 0.00 71.145 0.828 8.655 1.240 0.1060 25.30 0.00 42.860 0.690 3.410 0.090 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0860 2.480 0.010 2.060 0.060 0.220 0.009 0.0938 0.001 2.668 0.101 2.232 0.087 0.218 0.019 0.0990 2.295 0.039 1.970 0.049 0.190 0.011 0.1060 0.920 0.000 0.990 0.050 0.090 0.002 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0860 0.121 0.003 0.080 0.004 0.097 0.004 0.0938 0.001 0.120 0.008 0.082 0.009 0.090 0.009 0.0990 0.099 0.004 0.064 0.005 0.084 0.015 0.1060 0.052 0.001 0.039 0.001 0.052 0.001 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

43 Figure A01-E7b. Emission Index for engine SA007 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA007. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

44 Figure A01-E7c. Emission Index for engine SA007 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA007. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

45 Figure A01-E7d. Emission Index for engine SA007 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 7. Table A01-E8a. Selected test results for engine SA008 (MDW 2009). Aircraft test conducted from 3/4/09 04:50 to 3/4/09 05:30, ambient temperature 270.81K, relative humidity 56%. Fuel Flow 2σ N1 2σ CO EI s FID EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 g kg-1 g kg-1 0.0870 20.85 0.07 70.745 0.615 8.370 1.159 0.0900 20.80 0.00 71.310 0.490 8.990 1.000 0.0930 20.80 0.14 67.905 0.653 7.940 1.253 0.0997 0.0006 20.23 0.06 67.400 1.281 6.077 0.722 0.1050 25.20 0.00 43.340 0.580 3.360 0.310 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0870 2.230 0.028 1.935 0.025 0.195 0.008 0.0900 2.220 0.010 1.940 0.060 0.180 0.010 0.0930 2.140 0.026 1.850 0.033 0.185 0.007 0.0997 0.0006 1.947 0.045 1.750 0.050 0.153 0.014 0.1050 0.910 0.010 0.990 0.020 0.080 0.003 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0870 0.106 0.005 0.075 0.002 0.078 0.005 0.0900 0.108 0.004 0.076 0.003 0.083 0.005 0.0930 0.100 0.003 0.071 0.002 0.072 0.003 0.0997 0.0006 0.082 0.005 0.057 0.004 0.068 0.008 0.1050 0.048 0.001 0.037 0.001 0.048 0.002 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

46 Figure A01-E8b. Emission Index for engine SA008 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA008. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

47 Figure A01-E8c. Emission Index for engine SA008 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA008. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

Figure A01-E8d. Emission Index for engine SA008 using the continuous FID instrument. The grey data points and error bars are the full FID EI dataset collected during the project, which only includes CFM56-7B24 data at MDW 2009. The larger points, in blue are the results for engine 8. Table A01-E9a. Selected test results for engine SA009 (DAL 2009). Aircraft test conducted from 10/15/09 02:30 to 10/15/09 03:30, ambient temperature 297.51K, relative humidity 94%. Fuel Flow 2σ N1 2σ CO EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 0.0854 0.0009 21.14 0.11 60.594 2.514 0.0927 0.0005 22.07 1.50 53.100 2.397 0.0955 0.0007 21.15 0.21 53.575 2.127 0.1013 0.0006 22.20 0.95 34.903 1.240 0.1050 0.0000 24.00 0.00 31.120 1.240 0.1100 0.0000 25.60 0.00 27.430 1.100 Engine SA_009 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0854 0.0009 1.456 0.087 0.896 0.142 0.186 0.032 0.0927 0.0005 1.212 0.077 0.880 0.085 0.155 0.022 0.0955 0.0007 1.210 0.105 0.850 0.146 0.165 0.024 0.1013 0.0006 0.490 0.018 0.393 0.024 0.067 0.009 0.1050 0 0.350 0.010 0.320 0.020 0.050 0.010 0.1100 0 0.320 0.010 0.280 0.020 0.040 0.010 Engine SA_009 Fuel Flow 2σ Toluene EI 2σ C2- Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0854 0.0009 0.080 0.009 0.071 0.008 0.048 0.006 0.0927 0.0005 0.056 0.009 0.060 0.007 0.036 0.006 0.0955 0.0007 0.066 0.011 0.062 0.009 0.040 0.007 0.1013 0.0006 0.028 0.004 0.039 0.005 0.020 0.003 0.1050 0.0000 0.020 0.003 0.025 0.002 0.015 0.002 0.1100 0.0000 0.017 0.004 0.020 0.002 0.015 0.003 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

49 Figure A01-E9b. Emission Index for engine SA009 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA009. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

50 Figure A01-E9c. Emission Index for engine SA009 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA009. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

51 Table A01-E10a. Selected test results for engine SA010 (MDW 2010). Aircraft test conducted from 2/15/10 04:50 to 2/15/10 05:30, ambient temperature 267.41K, relative humidity 78%. Fuel Flow 2σ N1 2σ CO EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 0.0870 0.0000 21.37 0.40 78.183 3.468 0.0930 0.0000 20.85 0.07 75.890 2.832 0.0970 0.0000 22.95 2.62 61.680 8.640 0.1007 0.0012 23.67 2.31 62.287 5.225 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0870 0 2.487 0.157 2.007 0.150 0.280 0.018 0.0930 0 2.270 0.104 1.915 0.128 0.251 0.012 0.0970 0 1.690 0.299 1.460 0.242 0.184 0.032 0.1007 0.001154699 1.750 0.147 1.547 0.151 0.197 0.016 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2- Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0870 0.0000 0.175 0.012 0.182 0.010 0.132 0.010 0.0930 0.0000 0.155 0.010 0.154 0.009 0.113 0.010 0.0970 0.0000 0.113 0.018 0.114 0.014 0.088 0.014 0.1007 0.0012 0.121 0.010 0.119 0.005 0.096 0.007 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

52 Figure A01-E10b. Emission Index for engine SA010 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA010. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

53 Figure A01-E10c. Emission Index for engine SA010 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA010. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

54 Table A01-E11a. Selected test results for engine SA011 (MDW 2010). Aircraft test conducted from 2/15/10 07:00 to 2/15/10 07:40, ambient temperature 266.41K, relative humidity 77%. Fuel Flow 2σ N1 2σ CO EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 0.0840 0.0000 21.10 0.26 72.837 3.116 0.0910 0.0000 20.95 0.07 68.780 2.389 0.0970 0.0000 20.70 0.00 63.460 2.102 0.0990 0.0017 25.13 0.40 48.070 2.416 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0840 0 2.000 0.123 1.677 0.116 0.212 0.013 0.0910 0 1.800 0.070 1.555 0.090 0.190 0.008 0.0970 0 1.595 0.053 1.370 0.075 0.159 0.005 0.0990 0.00173205 1.090 0.077 1.000 0.078 0.118 0.009 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0840 0.0000 0.126 0.009 0.119 0.007 0.101 0.008 0.0910 0.0000 0.111 0.005 0.097 0.004 0.087 0.006 0.0970 0.0000 0.092 0.004 0.074 0.003 0.074 0.005 0.0990 0.0017 0.069 0.007 0.065 0.007 0.060 0.007 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

55 Figure A01-E11b. Emission Index for engine SA011 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA011. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

56 Figure A01-E11c. Emission Index for engine SA011 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA011. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

57 Table A01-E12a. Selected test results for engine SA012 (MDW 2010). Aircraft test conducted from 2/16/10 02:30 to 2/16/10 03:10, ambient temperature 269.81K, relative humidity 80%. Fuel Flow 2σ N1 2σ CO EI 2σ kg s-1 kg s-1 % % g kg-1 g kg-1 0.0817 0.0006 20.17 0.23 86.163 3.228 0.0880 0.0000 19.75 0.21 79.595 2.665 0.0930 0.0008 19.80 0.34 76.555 2.761 0.0955 0.0021 25.25 0.21 58.720 2.238 Engine SA_001 Fuel Flow 2σ C2H4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0817 0.0006 3.027 0.143 2.360 0.143 0.405 0.026 0.0880 0 2.505 0.090 2.020 0.107 0.329 0.016 0.0930 0.0008 2.185 0.085 1.778 0.108 0.279 0.018 0.0955 0.0021 1.725 0.084 1.440 0.088 0.228 0.024 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0817 0.0006 0.255 0.019 0.211 0.014 0.193 0.012 0.0880 0.0000 0.205 0.014 0.152 0.010 0.157 0.010 0.0930 0.0008 0.171 0.012 0.126 0.013 0.129 0.012 0.0955 0.0021 0.139 0.014 0.112 0.016 0.119 0.012 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

58 Figure A01-E12b. Emission Index for engine SA012 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA012. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

59 Figure A01-E12c. Emission Index for engine SA012 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA012. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

60 Table A01-E13a. Selected test results for engine SA013 (MDW 2010). Aircraft test conducted from 2/16/10 04:30 to 2/16/10 05:15, ambient temperature 269.71K, relative humidity 80%. Fuel Flow 2σ N1 2σ CO EI 2σ kg s -1 kg s -1 % % g kg -1 g kg -1 0.0860 0.0014 20.55 0.42 100.033 3.885 0.0920 0.0000 20.05 0.21 86.645 3.029 0.0973 0.0005 20.20 0.45 78.808 3.093 0.0997 0.0015 25.37 0.45 65.287 3.780 Engine SA_001 Fuel Flow 2σ C 2 H 4 EI 2σ HCHO EI 2σ Benzene EI 2σ kg s kg s -1 -1 g kg -1 g kg -1 g kg -1 g kg -1 g kg -1 g kg -1 0.0860 0.0014 3.118 0.150 2.285 0.147 0.323 0.016 0.0920 0 2.450 0.101 1.875 0.111 0.251 0.013 0.0973 0.0005 2.070 0.098 1.580 0.104 0.209 0.012 0.0997 0.0015 1.577 0.149 1.290 0.124 0.165 0.025 Engine SA_001 Fuel Flow 2σ Toluene EI 2σ C2-Benzene 2σ Styrene 2σ kg s-1 kg s-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 g kg-1 0.0860 0.0014 0.191 0.012 0.155 0.008 0.138 0.009 0.0920 0.0000 0.144 0.008 0.106 0.006 0.108 0.007 0.0973 0.0005 0.118 0.009 0.083 0.006 0.087 0.007 0.0997 0.0015 0.095 0.019 0.075 0.012 0.076 0.014 Table Notes. The 2σ value is computed as twice the standard error of the fit emission ratio converted to emission index. When multiple data points have been averaged at the noted fuel flow rate, these errors have been added in quadrature.

61 Figure A01-E13b. Emission Index for engine SA013 for CO, HCHO, C2H4, and C6H6. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA013. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left CO in black; upper right HCHO in orange; lower left ethene (C2H4) in magenta; and lower right benzene (C6H6) in violet.

62 Figure A01-E13c. Emission Index for engine SA013 for Toluene, C2-Benzene, Styrene, and Naphthalene. C2-Benzene refers to the sum of the xylene isomers and ethyl-benzene. The four figures depict the emission indices in grey with the precision-based error bar from the entire CFM56-7B24 dataset. The colored data points are the emission index for the species in question averaged for the nominal engine state during the test of engine index SA013. In many cases the precision based error bar for the emission index is smaller in magnitude than the size of the data point. See companion table for precision-based error bars. The absolute averaged emission indices for the fuel flow repeats during the test are depicted in the four panels; upper left Toluene in red; upper right C2-Benzene in light-blue; lower left Styrene in light green; and lower right naphthalene in the larger grey squares.

63 Testing on the V2527-A5 At the conclusion of the MDW 2010 testing campaign, the mobile laboratory was driven to Chicago ORD airport in order to collect abbreviated test data on engine technologies in addition to the CFM56 type engine. One of the two aircraft tested in this phase of the project, provided by United Air Lines, was an A320-232 equipped with the V2527-A5 engine variant. The sampling style employed was identical to that used in the MDW 2009 phase, where the mobile laboratory was maneuvered behind the aircraft. Figure A01-Va depicts the results of the determination of CO and HCHO emission indices as a function of fuel flow noted in the cockpit. All of the data collected in this test, {engine 1, engine 2 and at distances where the sample was a mixture of both engines} has been plotted together. Where the digital readout in the cockpit indicated a difference in fuel flow between the two engines and the sampling distance was such that we could not plausibly argue the sample was domi- nated by one engine or the other, the average has been used in the graphical representation. The CO EI tabulated in the ICAO databank has been placed on the figure as a black diamond. The dashed line is approxi- mately 37% greater than the ICAO databank value at a fuel flow rate of 0.128 kg/s. This qualitatively agrees with the trend observed in the CO EI temperature dependence in other work (AAFEX) as well as the temperature dependence derived for the near-idle hydrocarbon EI (see main project narrative). The simple two point temperature dependence derived from this single engine test indicates the engine is slightly less dependent on ambient temperature than the CFM56-7B24 and CFM56-2C1 engine tests. This engine type does warrant additional study in the future, but the single test described here should not be over-interpreted. The ICAO databank HC EI for the V2527-A5 is 22 times lower than the HC emission index tabulated for the CFM56-7B24. As a result, the limits of detection in the analytical instrumenta- tion preclude assigning any speciated VOC emissions for this engine type beyond formaldehyde. Using the tabulated emission index of 0.105 g HC per kg fuel, and the ratio of HCHO to HC measured in the MDW 2009 tests (0.2 g HCHO per “g” HC), it suggests the HCHO EI for this engine type at the 7% thrust fuel flow rate should be 21 mg HCHO per kg fuel. In the right hand panel of Figure A01-Va, this estimate is quite close to what is actually observed at the fuel flow rate of 0.128 kg s-1. This would suggest that the dependence of HCHO EI on ambient temperature is weaker than that observed in the CFM56 engine testing. Testing of the PW4090 Following the testing of the V2527-A5, the United Air Lines personnel suggested that a 777-222ER equipped with PW4090 be tested next. The data from this test are tabulated here, however it was unscheduled work and as a result the precise engine settings required to match the ICAO 7% engine condi- tion were not known during the test. The PW4090 represents a much higher thrust engine class then either of the CFM56 or V2500 engine types and we had to trust the experience of the maintenance crew we were working with in order to keep a safe condition for the mobile laboratory maneuvering behind the idling engine. Due to the spontaneous nature of the test, we did not attempt to operate the engines independently. The test matrix was Figure A01-Va. Emission Indices for CO and HCHO for the V2527-A5 test. The left hand panel depicts the measured CO EI as a function of engine fuel flow rate. The right hand panel plots the measured HCHO EI (in mg kg21) as a function of fuel flow rate.

64 simplified to include the conditions described in Appendix B as ground-idle with zero bleed air demand, ground-idle with nominal bleed air demand and at N1 = 25%. This last test condition was a guess on what N1 setting would correspond to 7% thrust for this engine. The Figure A01-Pa depicts the CO emission index vs. the fuel flow rate for the test. Note that it is clear that the ICAO 7% fuel flow condition was not matched in this test. The range of noted N1 rotation speeds for the clus- ter of data measured below 0.24 kg s-1 were all in the range of 18.9 to 20.0%. The range of noted N1 rotation speeds for the three measurements above 0.3 kg s-1 were all 24.1 to 25.6%. In this engine test, the effect bleed air demand on fuel flow was considerably less than was observed in the CFM56 tests. The comparison to the ICAO CO certification value is challenged because the fuel flow rate needed to match the 7% thrust condition was apparently not met. If the dashed line drawn between the cluster of CO points is taken to represent the CO emission index at intermediate fuel flows, then the comparison could be termed “favorable”. The very puzzling aspect of this comparison, however is the apparent agreement. The ambient temperature was 270.3K (RH = 67%) for this test is sufficiently less than the ICAO reference temperature of 288K that the understanding of ambient temperature depen- dence developed in this study (based on the CFM56 tests) suggests the measured CO should have been greater. The qualitative observation of emission index trend with fuel flow is matched here though. The emission index for CO (and the hydrocarbons not depicted) is approximately double (N1 = 20% relative to N1 = 25%). Additional work will be needed to extract a quantitative comparison with ICAO for this engine test. An additional evaluation can be performed that com- pares the hydrocarbon profile of this “large engine” to the more thoroughly tested CFM56 engines. The HC EI at 7% tabulated in ICAO is nearly identical for the PW4090 and the CFM56-7B24, indicating that unlike the comparison between the CFM56-7B24 and the V2527-A5, there should at least be hydrocarbons present of a similar magnitude to verify the hydrocarbon profile for the selected species mea- sured at this test. Figure A01-Pb depicts the correlation of the emission indices of 1,3-butadiene and formaldehyde for the PW4090 test. The grey dashed line in Figure A01-Pb is a linear least squares fit to the data forced through the origin which suggests the relationship between 1,3-butadiene and formaldehyde is 103±4 mg:g-1. This compares favorably to the current value asserted in the SPECIATE profile (137 mg:g-1). Additional hydrocarbon ratios tabulated in Table A01-Pc suggest generally good agreement with the SPECIATE profile for this test (EPA 2008). While the compound ratios for the other VOCs, except for ethene, tend to be lower than that predicted by SPECIATE, such a good correlation might not have been expected given that SPECIATE is derived from CFM56 engine (EPA 2008). This singular comparison should not be over interpreted, but it does suggest that VOC emis- sion profile is not highly dependent on combustor design. Figure A01-Pa. CO Emission Index vs Fuel Flow for PW4090. The Grey squares are the CO emission index plotted vs engine average fuel flow (see text for details). The black diamond is the ICAO reference CO EI at 7% fuel flow rate.

65 Table A01-Pc. PW4090 compound ratios. (g / g formaldehyde) uncertainty SPECIATE Ethane 1.30 0.04 1.25 1,3 butadiene 0.103 0.004 0.137 Benzene 0.128 0.006 0.137 Toluene 0.036 0.006 0.052 C2-benzenes 0.046 0.008 0.050 Naphthalene 0.032 0.002 0.044 Additional engines needed to be studied to further corroborate this finding. A02—Additional Findings on the Near-Idle Hydrocarbon Emission Profile Our characterization of VOC emissions from Jet aircraft engines has spanned a period of 8 years and 12 separate mea- surement opportunities (Herndon et al. 2006, Herndon et al. 2009, Knighton et al. 2007, Yelvington et al. 2007) (need to include AAFEX NASA reference). During these studies, we have observed a consistent and repeatable phenomenon, in which we find that nearly all of the VOC exhaust emissions components scale in a near-linear relationship with one another under low power conditions. We refer to this obser- vation as near-idle emissions scaling. In this section, we first briefly review the instruments and sampling methods and then present results that illustrate the near-idle VOC emissions scaling phenomenon. This is followed by a discussion of how this relationship can be used to interrogate our analytical methodology, probe sampling effects, gaps in existing VOC speciation profile, and the validity of predicting VOC emissions that were not directly measured. Before we present any data, it is important to review the analytical methods and sampling strategies employed. Sampling strategies differed in how the engine exhaust samples were delivered to the instruments. During MDW 2009, a down-wind plume intercept approach was used, which allowed the exhaust to cool and dilute naturally into ambient air. The concentration of the components within the exhaust plume dilutes continuously with down-wind distance and is modulated further by wind speed and direc- tion. The plume intercept method requires that all of the instruments operate at 1 Hz. Extraction probes were used during DAL 2009 and MDW 2010 to transport the exhaust sample to the instruments. At DAL 2009, three different extraction probes were used and differed on how and where Figure A01-Pb. 1,3-butadiene EI vs. HCHO EI. The PW4090 test results for the NO-MS measurement of 1,3-butadiene are plotted against the QCL measurement of HCHO. The color scaling indicates the time since the engines were turned on. The ratio between these hydrocarbon species does not depend on the engine warm up.

66 the exhaust was diluted. At MDW 2010 a single extraction probe was deployed. VOC measurements were made using a total of four differ- ent instruments, one of which (MSU PTR-MS) was operated in two different chemical reagent ion modes. Formaldehyde and ethene were measured spectroscopically using QCL TILDAS instruments. The remaining VOCs were measured using a pair of chemical ionization mass spectrometers, except at DAL 2009 where only one instrument was deployed. Table A02-1 lists VOC species measured and identifies which instrument method was used. The compound list in Table A02-1 rep- resents only those compounds that were measured during all of the deployments. The instruments are designated as follows: QCL represents the QCL TILDAS instruments. MSU H3O+ and MSU NO+ refer to the MSU PTR-MS operated in standard proton transfer (H3O+) or alternative ion (NO+) mode. The PNL PTR-MS was only operated in the standard H3O+ mode. In cases where the same species was measured by more than one instrument, only the “best” measurement is reported. At MDW 2010 the PNL PTR-MS measurements were chosen for styrene and naphthalene because of evidence that there were interferences to NO-MS measurements. For toluene, the calibration of the NO-MS is less robust and the PTR-MS measurement was considered as the best. The near-idle VOC scaling phenomenon is illustrated in Figure A02-1, where we have taken the EI data for each of the VOC species and plotted it versus the corresponding ethene measurement. The plot colors identify the different measurements, MDW 2009 (red), DAL 2009 (green) and MDW 2010 (blue), while the different aircraft tested are identified by a different marker style. Overall, there is also a strong suggestion that all of the measurements are correlated in a near-linear fashion even though these profiles show varying degrees of scatter. Closer inspection reveals that the scatter in the plots, however, is not random. In most cases, the profiles exhibit a linear ray for each aircraft. It is from this behavior that the term near-idle VOC scaling concept arose. While it is not clear why near-idle VOC scaling should exist, it does collapse much of the variability observed in the absolute EI measurements. This is important, because it allows us to identify which measurements don’t follow the trend and then interrogate those measurements more carefully. We can now examine the profiles shown in Figure A02-1 more carefully with the goal of identifying the source or sources that lead to the observed variability. Formaldehyde and acetaldehyde both show similar behavior except for the five formaldehyde data points that lie below the rest of the data. These data were all measured using the gas probe during DAL 2009. This is not a sampling anomaly as the PTR-MS measurement of formaldehyde exhibited an identical result. It is not immediately obvious why formaldehyde should be lost or consumed within the gas probe, but it certainly casts some doubt about the use of this type of probe. In fact, it leads one to question if the reason why both formaldehyde and acetaldehyde measurements from MDW 2009 lie above those made using extractive probes isn’t the result of a probe effect. We also note that there is some curvature in the formaldehyde and acetaldehyde plots at the highest emissions. This result seems to suggest that the fuel continues to decompose to ethene but that combustion begins to diminish under these conditions. Inspection of the other profiles shows that there is inherently more variability in the hydrocarbon emissions, in part due to their lower concentrations (molar basis). It is logical to question whether this variability originates from the measurements or reflects differences in the engine exhaust emissions. In cases where the results show obvious differences between the test periods (i.e., 1,3-butadiene), Table A02-1. Instrumental methods used for the measurement of the selected VOCs. Compound MDW 2009 DAL 2009 MDW 2010 formaldehyde QCL QCL QCL ethene QCL QCL QCL acetaldehyde PNL-H3O+ MSU-H3O+ PNL-H3O+ 1,3-butadiene MSU-NO+ ---- MSU-NO + benzene MSU-NO+ MSU-H3O+ MSU-NO+ toluene MSU-NO+ MSU-H3O+ PNL-H3O+ styrene MSU-NO+ MSU-H3O+ PNL-H3O+ C2-benzenes MSU-NO+ MSU-H3O + MSU-NO+ naphthalene MSU-NO+ MSU-H3O + PNL-H3O+

67 Figure A02-1. Near-idle VOC emissions scaling profiles. Marker color indicates the measurement date and location. Marker styles identify the different aircraft.

68 it seems logical to question if the variability isn’t the result of the analytical measurement. An incorrect instrument calibration factor could lead to such a result, even though every effort was made to check the calibrations before, during and after the studies. When differences are observed within the aircraft studied at a given test, it would appear that the variability is related either to the fuel, the engine or some other unknown external influence. We can now examine the results of this study to that reported elsewhere, such as SPECIATE or our previous AAFEX results (Anderson et al. 2010, EPA 2008). To make this comparison we have normalized our data to that of ethene and fit the fre- quency distribution to a Gaussian. The centroid of the Gaussian distribution is taken as the best value with the width represent- ing the uncertainty. For 1,3-butadiene the average and standard deviation are reported, because the frequency distribution is bimodal. These results are summarized in Table A02-2 along with those reported in SPECIATE (EPA 2008) and from AAFEX for JP-8 (Anderson et al. 2010). The ACRP data agree within the uncertainty limits with the other measurements except for acetaldehyde, which is approximately 30% high. Near-idle VOC emissions scaling allows us to decouple changes in the VOC composition of the exhaust from the variability in the absolute VOC EIs exerted by engine power and ambient temperature. The near-linear relationships observed in Figure A02-1 and the overall agreement between the ethene normalized EIs found here with that reported elsewhere, strongly suggests that the VOC composition is relatively insensitive to engine condition or fuel composition, at least over the limited range of engines studied and fuel compositions. The relative consistency of the VOC exhaust composition allows one to then project the emissions of chemical species not directly measured by scaling the emis- sions to that of ethene. The obvious question arises. Over what range of conditions can the near-idle VOC emission scaling be applied? To address this question we need to exam- ine how our speciated VOC emissions vary with CO and UHC (unburned hydrocarbons). Figures A02-2 and A02-3 examine the relationship between the emission of ethene with those of CO and UHC as measured with an FID. Two very different behaviors emerge. When the ethene EI is less than 2g/kg the ethene emissions appear to scale in a near-linear fashion with both CO and UHC. As the ethene EIs increase above 2g/kg nonlinearities appear. The CO emissions stop increasing at the same rate and the UHC emissions start increasing more rapidly with respect to ethene. This result suggests that the engine reaches a condition where it is no longer burning most of the fuel. If one views combustion as a simple two step process, where the fuel pyro- lyzes decomposes into smaller molecules (ethene) followed by combustion (oxidation), then it follows that ethene pro- duction would continue longer than the combustion process. Likewise, the ethene production will diminish relative to the UHC at the point where unburned fuel actually escapes from the combustor. While this argument explains the relationship between ethene and UHC, why don’t the VOCs in Table 2 (i.e., the aromatics) exhibit more non-linearity at the higher EIs? Some of the species in Table A02-2 are only combus - tion products and are not present in the liquid fuel. Others, such as the aromatics, are both combustion products and components of the liquid fuel. It is beyond the scope of this report to do a detailed examination of how the VOC emissions vary with fuel composition, but the observation of the near-idle VOC emission scaling exhibited by the aromatics infers that, under the conditions studied, their presence in the exhaust is dominated by combustion and not the escape of unburned fuel into the exhaust. In con- trast the FID is most sensitive to the presence of large hydrocarbons, such as the long chained alkanes that make Species Speciate EIx/EIethane AAFEX EIx/EIethene ACRP EIx/EIethene formaldehyde 0.80 0.75 0.79 (0.12) acetaldehyde 0.28 0.27 0.35 (0.04) 1,3-butadiene 0.11 ---- 0.10 (0.03) Benzene 0.11 0.12 0.10 (0.04) Toluene 0.042 0.057 0.056 (0.007) Styrene 0.020 0.026 0.043 (0.016) C2-benzenes 0.040 (0.053)a 0.047 (0.026) Naphthalene 0.035 0.028 0.028(0.015) (a) The PTR-MS determination reports the sum of the C2-benzenes + benzaldehyde. The data entry here has been adjusted to correct for the benzaldehyde contribution assuming that 43% of the response is from benzaldehyde. Table A02-2. Comparison of compound EIs normalized to ethene.

69 up a large fraction of the liquid fuel. The bias in the UHC towards the presence of unburned fuel is further exacer- bated by the fact that FID detector response is diminished to carbons that are bonded to an oxygen. The FID is essen- tially blind to the presence of formaldehyde, which rep- resents approximately 12% of the organic carbon in the exhaust. Scaling emissions from either CO or UHC measurements using databases such as SPECIATE (EPA 2008) need to recog- nize the limits where these relationships become non-linear. Anecdotally, it appears that there is little error introduced under moderate to warm ambient temperatures. A linear scaling to CO or UHC is not appropriate at low ambient temperatures. Figure A02-3. Correlation scatter plot of ethene EI versus CO EI. Figure A02-2. Correlation scatter plot of ethene EI versus unburned hydrocarbon UHC EI.

70 Near-idle VOC emissions scaling can be a valuable tool for projecting jet engine exhaust emissions, providing it is properly applied. Its validity, however, is only as good as the knowl- edge of VOC speciation profile. Databases such as SPECIATE (EPA 2008) contain extensive listing, but are still not com- prehensive and only identify 70% of the VOC mass emissions. The bulk of the missing mass is most likely in the higher molecular hydrocarbons, which are difficult to conclusively identify by GC/MS because of their similar mass spectral fragmentation patterns. There is also evidence from studies conducted elsewhere (Anderson et al. 2010, Timko et al. 2011) using a GC/PTR-MS that indicates the presence of unsaturated aldehydes, corresponding to C4H6O and C5H8O that are not included in SPECIATE (EPA 2008). These species are more likely to be on the HAPs list and thus represent species of concern. References Cited in Appendix A Anderson, B. E., et al. 2010. Alternative Aviation Fuel Experiment (AAFEX) Rep. EPA. 2008. SPECIATE, edited. US EPA. Herndon, S. C., T. Rogers, E. J. Dunlea, R. C. Miake-Lye, and B. Knighton. 2006. Hydrocarbon emissions from in-use commercial aircraft during airport operations. Environmental Science and Technology. 40 (14): 4406–4413. Herndon, S. C., E. C. Wood, M. J. Northway, R. C. Miake-Lye, L. Thornhill, A. Beyersdorf, B. E. Anderson, R. Dowlin, W. Dodds, and W. B. Knighton. 2009. Aircraft Hydrocarbon Emissions at Oakland International Airport, Environ Sci. Technol. 43. 1730–1736. Herndon, S. C., et al. 2004. NO and NO2 Emissions Ratios Measured from in use Commercial Aircraft during Taxi and Take-Off. Environ. Sci. Technol. 38: 6078–6084. Knighton, W. B., T. Rogers, C. C. Wey, B. E. Anderson, S. C. Herndon, P. E. Yelvington, and R. C. Miake-Lye. 2007. Quantification of Aircraft engine Hydrocarbon Emissions Using Proton Transfer Reaction Mass Spectrometry. Journal of Propulsion and Power 23 (5): 949–958. Timko, M. T., S. Herndon, E. de la Rosa Blanco, E. Wood, Z. Yu, R. C. Miake-Lye, W. B. Knighton, L. Shafer, M. DeWitt, and E. Corporan. 2011. Combustion Products of Petroleum Jet Fuel, a Fischer Tropsch Synthetic Fuel, and a Biomass Fatty Acid Methyl Ester Fuel for a Gas Turbine Engine. Combust. Sci. Technol. in press. Yelvington, P. E., S. C. Herndon, J. C. Wormhoudt, J. T. Jayne, R. C. Miake-Lye, W. B. Knighton, and C. C. Wey. 2007. Chemical Specia- tion of Hydrocarbon Emissions from a Commercial Aircraft Engine. Journal of Propulsion and Power. 23: 912–918.