In all cases, the maximum value of nvPMMC is then divided by the coefficients listed in A16V2, Appendix 6, Table A6-1 (provided as Attachment 3 to this AC), as described in 13.2.1 of this AC.
OEMs may request approval from FAA for variations to this approach for curve fitting and averaging, with supporting justification.
14.2. Section 34.73 nvPM Demonstration of Compliance Section 34.73 (14 CFR 1031.140) requires that the equipment and procedures specified in Appendix 6 of A16V2 be used to determine whether an engine meets the applicable nvPM limit specified in § 34.25. A demonstration of compliance includes calculations to determine the characteristic nvPM emissions levels for maximum nvPMMC, nvPMmass, and nvPMnum by using the measurements collected in accordance with §
34.71. The applicant's compliance demonstration must be conducted within 90% confidence intervals (§
34.73(d)), use the required rounding in calculations (§ 34.73(a)(3)), and correct for standard temperature and pressure as prescribed in the Annex 16, Volume II, Appendix 1 for the measurement of reference pressure ratio.
Section 34.73(c)(1) directs the applicant to conduct the minimum number of measurements at the thrust settings given in § 34.71(h). This section also provides an applicant with the flexibility to make as many additional measurements as it chooses across the entire thrust range of an engine when measuring nvPM. Additional measurements conducted across the thrust range of an engine result in a more precise understanding of any trending nvPM behavior.
Section 34.73(c)(1) allows an applicant to use one of the three equivalent evaluation methods listed in that section when calculating nvPMMC. Once nvPM emissions certification testing is complete, § 34.73(e) identifies the required information to be reported to the FAA in the emissions test report.
The nvPM rule is written based on corrected thrust as the correlating parameter. However, the FAA recognizes that for each thrust setting there is one unique combustor inlet temperature (T 3). Therefore, thrust and T3 may be used interchangeably as a correlating parameter in demonstrating nvPM compliance.
Note: EPA has separate reporting requirements in 40 CFR 1031 that are different than those required under part 34.
14.3. Corrections to Reference Atmospheric Conditions The reference atmospheric conditions to which the gaseous emissions (HC, CO and NO x) are to be corrected are the reference day conditions, as follows: temperature = 15°C, humidity = 0.00634 kg H2O/kg of dry air, pressure = 101.325 kPa.
The requirements and procedures to correct gaseous emissions indices to reference day conditions are provided in A16V2, Appendix 3, 7.1 – 7.3. These procedures require defining a constant through curve fitting techniques of the measured emissions data, and applying the constant to the me asured gaseous emissions indices for CO, HC, and NOx.
Corrections to reference atmospheric conditions for nvPM emissions is done automatically by the nvPM mass and number instrumentation that is calibrated and operated pursuant to A16V2, Appendix 7., 5.1. , and further discussed in 15.6 of this AC.
15. Guidance on ICAO A16V2, Appendix 7, Instrumentation and Measurement Techniques for nvPM Emissions Note: As defined in Attachment 2 of this AC, the FAA nomenclature used for nvPM is: nvPMMC, nvPMmass, and nvPMnum, while the ICAO nomenclature used for these terms is nvPMmass, EImass, and EInum, respectively. ICAO nomenclature is used throughout 15 of this AC.
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15.1. Appendix 7, 3.1: Data Required – nvPM Emissions The non-volatile particulate matter (nvPM) sampling and measurement system is standardized to measure nvPM mass and number engine emissions. In addition, it uses the measurement of the full gaseous emissions as specified in A16V2, Appendix 3. The measurement of the full gaseous emissions allows a more precise calculation of nvPM mass concentration and nvPM mass and number emission indices (EIs), based on wet gaseous concentrations. In this case, the matrix solution described in Attachment A of A16V2 for the calculation of emissions parameters is typically used to perform necessary corrections to determine gaseous concentrations on a wet basis. For that reason, the CO, HC and NO x concentrations are listed as data required.
15.9 of this AC (ETMV2, Appendix 7, 6.1.2) provides an equivalent procedure for the calculation of EImass and EInum (nvPMmass and nvPMnum in this AC) using only nvPM and dry or wet CO2 measurements. Since the combustion efficiencies of modern turbine engines are greater than 95 per cent, it is reasonable to assume that all of the fuel carbon is converted to CO2. Thus, CO2-only (undiluted and diluted) measurements could be used to determine nvPM emission factors. In this case, measurements of [HC], [CO] and [NOx] are not required.
15.2. Appendix 7, 4 General Arrangement of the nvPM Sampling and Measurement System The nvPM sampling and measurement system specified in A16V2, Appendix 7 addresses the collection, transport and quantification of mass and number of particles emitted from the engine. The measurement environment behind a gas turbine engine places significant constraints on the sampling system used to collect the exhaust sample. The high temperature, high velocity exhaust requires a robust probe at the engine exit and transports the sample to the measurement instruments. The system requirements are compounded by the need to minimize the influence of the sampling system on the exhaust sample. Thus, a sophisticated system is specified. The transfer part of the system has been physically standardized to minimize variability between test facilities and operators, including the sampling lines. The exhaust sample is diluted and maintained at prescribed temperatures and flow rates to prevent condensation, minimize coagulation of particles to be measured and minimize particle transport loss prior to measurement. Once the sampling system has transported the exhaust sample to the measurement instruments, nvPM mass and number concentrations are measured.
The nvPM sampling and measurement methodology is established upon SAE International Aerospace Information Report (AIR) 6241 — Procedure for the Continuous Sampling and Measurement of Non- Volatile Particle Emissions from Aircraft Turbine Engines and documented in SAE International Aerospace Recommended Practice (ARP) 6320A – Procedure for the Continuous Sampling and Measurement of Non-Volatile Particulate Matter Emissions from Aircraft Turbine Engines.
15.3. Appendix 7, 4.1 nvPM Sampling and Measurement System (connections) An example of an acceptable sample line connection for use in Modules 2 to 4 is shown in Figure 2- 7.
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Figure 2-7. Example of a sampling line connection heating An example of an acceptable bulkhead connection for use in Modules 2 to 4 is shown in Figure 2- 8.
Appendix 7, 4.2: Collection Part (traverse measurements) For existing certified engines:
Where detailed traverse measurements for gaseous and smoke emissions testing have been conducted prior to the applicability of Amendment 9 to A16V2, and have been agreed to by FAA, the probe configurations already established may be acceptable for nvPM certification measurements.
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For new engine types or modifications that invalidate the previous probe configuration for emissions certification:
Where traverse measurements are required to demonstrate representative sampling, all emissions certification species should be taken into account for the evaluation of representativeness.
15.4. Appendix 7, 4.4.1: nvPM Mass Measurement (instrument conformity) A16V2, Appendix 7 requires the nvPM mass instrument (nvPMmi) to have a certificate showing the instrument has demonstrated conformity to the performance specifications listed in Appendix 7, 8.1.
Each instrument is delivered with a user manual to provide operating instructions and instrument specific calibration procedures. As standard practice, this manual includes the performance specifications of the instrument. The performance specifications which must be met to demonstrate conformity should normally be contained in this manual.
If the manual provides sufficient information to demonstrate conformity, the manual can serve as the instrument’s certificate. If this information is not contained in the manual, then an appendix to the manual or another separate document should be provided.
The data that could be expected is:
- Instrument make, model, sub-model/version number
- Versions of instrument software and hardware
- The values of the performance specifications with the indication of the determination methods used (e.g. test protocol, numerical results)
- The aerosol source recommended for annual calibration The instrument certificates are documents required by Appendix 7 and should be provided to the FAA during the aircraft engine certification process. If FAA determines the instrument certificates are not sufficiently detailed, further details may be requested.
As stated in Appendix 7, “each make and model of the nvPMmi shall receive a certificate from the instrument manufacturer or from another competent testing and calibration laboratory confirming that the make and model of the nvPMmi meets the performance specifications”. It is assumed that the instrument manufacturer has at least the same level of expertise as a competent laboratory, as defined in Appendix
7.
15.5. Appendix 7, 4.4.2 nvPM Number Measurement (instrument conformity) Annex 16, Volume II, Appendix 7 requires the nvPM number instrument (nvPMni) to have certificates showing the VPR and CPC have demonstrated conformity to the performance specifications listed in Appendix 7, 9.1.
Each instrument is delivered with a user manual to provide operating instructions and instrument specific calibration procedures. As standard practice, this manual includes the performance specifications of the instrument. The performance specifications which must be met to demonstrate conformity should normally be contained in this manual.
In the case the manual provides sufficient information to demonstrate conformity, the manual can serve as the instrument’s certificate. If this information is not contained in the manual, then an appendix to the manual or another separate document should be provided.
The data that could be expected is:
- Instrument make, model, sub-model/version number
- Versions of instrument software and hardware Page 27 of 57
- The values of the performance specifications with the indication of the determination methods used (e.g. test protocol, numerical results) The instrument certificates are documents that may be required by the certificating authority during the aircraft engine certification process.
As stated in Appendix 7, 9.1.3.1, “each make and model of the CPC shall receive a certificate from the instrument manufacturer or from another competent testing and calibration laboratory confirming that it meets the performance specifications listed”. It is assumed that the instrument manufacturer has at least the same level of expertise as a competent laboratory, as defined in Appendix 7.
15.6. Appendix 7, 5.1: Calibration and Maintenance Once an nvPMmi or nvPMni has been demonstrated to comply with the performance specifications (Table A7-5 of A16V2, Appendix 7, 8.1 for nvPMmi, Appendix 7, 9.1.3 for nvPMni), its configuration, both in hardware and software affecting data acquisition and signal processing must be maintained. For example, an nvPMmi may relate optical or other physical properties of the engine particles to the particle used in the calibration method performed in a laboratory using signal processing methods. Changes or improvements to hardware and such processing software or firmware of the nvPMmi or nvPMni, which affect the fundamental processing and the measurement of reported quantities, will require a new demonstration of conformity to the requirements in 8.1 for the instrument for use in engine certification.
This requirement does not include the routine or annual calibration of the instrument. The calibration of the instrument may lead to entering a different calibration factor into the instrument software but does not change the way measured physical properties are processed.
Any changes to the nvPMmi should be documented to allow the FAA to determine if changes affecting data acquisition and processing have been made.
To determine if changes affect data acquisition and processing, an independently calibrated and approved nvPMmi and an independently calibrated nvPMmi with hardware and software changes should be configured in parallel with the thermal optical transmittance (TOT) instrument behind the engine source, as specified in Annex 16, Volume II, Appendix 7, 8.3.3.
In addition to the four filters acquired to meet the verification requirement (Appendix 7, 8.3.3.2), data points should be obtained with the two nvPMmi (filters not required) at a minimum of 10 mass concentrations, at relatively uniform intervals, up to the maximum mass concentration measured for the verification (as specified in Table 2-2). A minimum of three or six (at respective relative mass Once an nvPMmi or nvPMni has been demonstrated to comply with the performance specifications (Table A7-5 of A16V2, Appendix 7, 8.1 for nvPMmi, Appendix 7, 9.1.3 for nvPMni), its configuration, both in hardware and software affecting data acquisition and signal processing must be maintained. For example, an nvPMmi may relate optical or other physical properties of the engine particles to the particle used in the calibration method performed in a laboratory using signal processing methods. Changes or improvements to hardware and such processing software or firmware of the nvPMmi or nvPMni, which affect the fundamental processing and the measurement of reported quantities, will require a new demonstration of conformity to the requirements in 8.1 for the instrument for use in engine certification.
This requirement does not include the routine or annual calibration of the instrument. The calibration of the instrument may lead to entering a different calibration factor into the instrument software but does not change the way measured physical properties are processed.
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Table 2-2.
Elemental carbon (EC) mass loading parameters for demonstration of conformity for a nvPMmi after a hardware or software (HW/SW) change Verification (Appendix 7, 8.3.3)
(Reference mass from TOT EC filters) Repeatability, Linearity, and Accuracy
(Reference mass from approved nvPMmi) Target Concentration (Relative to Maximum Verification Concentration — µg/m3) No. of Tests Target Concentration (Relative to Maximum Verification Concentration — µg/m3) No. of Tests minimum ≤ 0.67 × middle concentration (< 120 µg/m3) 1 or 2 0.0 6
0.10 ± 0.05 × maximum 6
0.20 ± 0.05 × maximum 6
0.30 ± 0.05 × maximum 3
0.40 ± 0.05 × maximum 3 middle ≤ 0.67 × maximum 1 or 2 0.50 ± 0.05 × maximum 3
0.60 ± 0.05 × maximum 3
0.70 ± 0.05 × maximum 3 maximum (> 120 µg/m3) 1 or 2 0.80 ± 0.05 × maximum 3
0.90 ± 0.05 × maximum 3 maximum 6 Total: 4 Total: 45
For verification, a minimum of four filters are required, as stated in Appendix 7,8.3.3.
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15.7. Appendix 7, 5.3: Carbon balance check for nvPM using air/fuel ratio (AFR) Since it is possible to perform the full gaseous emissions measurement with the nvPM sampling and measurement system, the carbon balance check for nvPM measurements should be achieved using the air/fuel ratio (AFR) formula given in Annex16, Volume II, Appendix 3, 7.1.2:
where P0 includes all gaseous emissions concentrations.
Since the combustion efficiencies of modern turbine engines are greater than 95 per cent, it is reasonable to assume that all of the fuel carbon is converted to CO2. Thus, CO2-only measurements could be used for determination of the AFR and the equation could be simplified using a simplified P 0.
[CO2]b Gas concentration of CO2 in dry air, by volume = 0.0003 [CO2]S Mean gas concentration of CO2 vol/vol in undiluted exhaust as sampled, wet, semi-dry or dry MAIR Molecular mass of dry air = 28.966 g or, where appropriate, = (32 [O2]b + 28.156 4 [N2]b + 44.011 [CO2]b) g MC atomic mass of carbon = 12.011 g MH atomic mass of hydrogen = 1.008 g [N2]b Gas concentration of N2 + rare gases in dry air, by volume = 0.790 2 [O2]b Gas concentration of O2 in dry air, by volume = 0.209 5 m number of C atoms in characteristic fuel molecule n number of H atoms in characteristic fuel molecule The AFR estimated from the CO2 measured concentration should agree with the estimated engine AFR with an accuracy of ±15 per cent for the taxi/ground idle mode and with an accuracy of ±10 per cent for all other operating modes.
For modern engines, the simplified AFR estimation always predicts a slightly higher AFR than the full gaseous estimation. The estimated bias is:
a) less than 1 per cent for high power settings due to the high combustion efficiency; and
b) less than 3 per cent for idle conditions.
This impacts the carbon balance accuracy comparison to the estimated engine AFR. It is possible that the simplified carbon balance method could exceed the requirement. Thus, care should be taken to take account of the bias.
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15.8. Appendix 7, 6.1.1: nvPM mass concentration correction for first stage dilution factor (DF1) The nvPM mass concentration has to be corrected for the first stage dilution factor (DF 1). DF1 is determined using the following equation:
where [CO2] is calculated using the full gaseous emissions concentrations, as specified in Annex 16, Volume II, Attachment A for the wet correction.
Since the combustion efficiencies of modern turbine engines are greater than 95 per cent, it is reasonable to assume that all of the fuel carbon is converted to CO2, and CO2-only measurements could be used for determination of nvPM emissions. In this case, the CO2 concentration cannot be wet-corrected and the first stage dilution factor is calculated using directly the sampled [CO2]S:
Thus, the nvPM mass concentration could be calculated using the following equation:
For modern engines, the uncertainties introduced by using the simplified equation result in an increase of nvPMmass by up to 5 per cent for high power settings. This number decreases towards low power settings.
15.9. Appendix 7, 6.1.2: nvPM mass and nvPM number and CO2 only measurements for determination of EImass and EInum Since the combustion efficiencies of modern turbine engines are greater than 95 per cent, it is reasonable to assume that all of the fuel carbon is converted to CO2. nvPM and CO2-only measurements could be used for determination of EImass and EInum using the following simplified equations:
where DF1_S is the first stage dilution factor calculated using directly sampled [CO 2]S:
For modern engines, the uncertainties introduced by using the simplified equations result in an increase of the EImass and EInum by less than 0.1 per cent for high power settings due to the high combustion efficiency, and by less than 5 per cent for idle conditions.
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15.10. Appendix 7, 6.1.2: Examples of nvPM mass and nvPM number calculations using full gaseous emissions concentrations and simplified method Examples of nvPM mass and number calculations, using the full gaseous emissions concentrations to obtain more precise EIs and using the simplified method.
In these examples, the engine operates at an idle power condition and Jet A1 fuel is used. The engine exhaust plane temperature is 405°C (TEGT) and Diluter 1 inlet temperature is 163°C (T1).
Given parameters:
[CO2]dry 26051 ppm = 0.026051 [CO]dry 1012 ppm = 0.001012 [H2O] 0.0244 [HC] 0.000117 [CO2]b 0.0003 nvPMmass_STP 19 [µg/m3] nvPMnum_STP 2.18×103 [number/cm3] [CO2]dil1 2591 ppm/1000000 = 0.002591 DF2 100 α 1.92 (typical Jet A1)
1. Full gaseous method nvPM mass and number emission indices and nvPM mass concentration calculation examples
• nvPM primary mass concentration
• nvPM mass emission index Page 32 of 57
• nvPM number emission index
2. Simplified nvPM mass and number emission indices and nvPM mass concentration calculation examples
• nvPM primary mass concentration
• nvPM mass emission index Page 33 of 57
• n vPM number emission index
15.11. Appendix 7, 6.2.2: Correction for fuel composition using legacy, EEDB hydrogen to carbon ratio Legacy data in the Engine Emissions Databank may contain only the hydrogen to carbon ratio. Assuming the Jet-A fuel is comprised only of hydrogen and carbon, it is recommended to use the equation below to calculate %H (mass) from H/C ratio:
This equation can be inverted to calculate H/C ratio from %H (mass):
15.12. Appendix 7, 7.2: Examples of splitter geometries and assemblies Figures 2-9 and 2-10 show examples of splitter geometries and assemblies that meet the requirements and are acceptable for use. Note that there are many other possible geometries and assemblies that could meet the requirements and could be acceptable for use.
The number of Splitter 1 flow paths depends on the number of undiluted sample measurement lines and/or the need to relieve large excess sample pressure. Additional emission diagnostic instrumentation may be placed in the make-up flow path downstream of Splitter 2.
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Splitter design is not based upon hydraulic flow considerations but on the desire for standardization between sampling systems. Consideration of splitter design may not be necessary for the measurement of turbine engine nvPM emissions, since theoretically there is no impact on small particles (less than 300 nm diameter).
Figure 2-9. Schematic examples of splitter geometries Page 35 of 57