Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p40
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 40/57)
Character Range: 202009–204852

time corrected and aligned in accordance with paragraph 3 of this annex.

       6.2. Calculating NMHC and CH4 concentrations

For methane measurement using a NMC-FID, the calculation of NMHC depends on the calibration gas/method used for the zero/span calibration adjustment. When a FID is used for THC measurement without a NMC, it shall be calibrated with propane/air or propane/N2 in the normal manner. For the calibration of the FID in series with a NMC, the following methods are permitted:
(a) the calibration gas consisting of propane/air bypasses the NMC;
(b) the calibration gas consisting of methane/air passes through the NMC.
It is strongly recommended to calibrate the methane FID with methane/air through the NMC.
In method (a), the concentrations of CH4 and NMHC shall be calculated as follows:
In method (b), the concentration of CH4 and NMHC shall be calculated as follows:
where:
cHC(w/oNMC)  is the HC concentration with CH4 or C2H6 bypassing the NMC [ppmC1]

cHC(w/NMC)   is the HC concentration with CH4 or C2H6 flowing through the NMC [ppmC1]

rh           is the hydrocarbon response factor as determined in paragraph 4.3.3.(b) of Annex 5

EM           is the methane efficiency as determined in paragraph 4.3.4.(a) of Annex 5

EE           is the ethane efficiency as determined in paragraph 4.3.4.(b) of Annex 5

If the methane FID is calibrated through the cutter (method b), then the methane conversion efficiency as determined in paragraph 4.3.4.(a) of Annex 5 is zero. The density used for calculating the NMHC mass shall be equal to that of total hydrocarbons at 273.15 K and 101.325 kPa and is fuel-dependent.

       7. Determination of exhaust mass flow rate

       7.1. Introduction

The calculation of instantaneous mass emissions according to paragraphs 8. and 9. requires determining the exhaust mass flow rate. The exhaust mass flow rate shall be determined by one of the direct measurement methods specified in paragraph 7.2. of Annex 5. Alternatively, it is permissible to calculate the exhaust mass flow rate as described in paragraphs 7.2. to 7.4. of this annex.

       7.2. Calculation method using air mass flow rate and fuel mass flow rate

The instantaneous exhaust mass flow rate can be calculated from the air mass flow rate and the fuel mass flow rate as follows:

              where:

qmew,i  is the instantaneous exhaust mass flow rate [kg/s]

qmaw,i  is the instantaneous intake air mass flow rate [kg/s]

qmf,i   is the instantaneous fuel mass flow rate [kg/s]

If the air mass flow rate and the fuel mass flow rate or the exhaust mass flow rate are determined from ECU recording, the calculated instantaneous exhaust mass flow rate shall meet the linearity requirements specified for the exhaust mass flow rate in paragraph 3. of Annex 5 and the validation requirements specified in