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Current as of October 02, 2022 | Updated by FindLaw Staff
You may correct NOX emissions for intake-air humidity as described in this section if the standard-setting part allows it. See § 1066.605(c) for the proper sequence for applying the NOX intake-air humidity correction.
(a) For vehicles at or below 14,000 pounds GVWR, apply a correction for vehicles with reciprocating engines operating over specific test cycles as follows:
(1) Calculate a humidity correction using a time-weighted mean value for ambient humidity over the test interval. Calculate absolute ambient humidity, H, using the following equation:
Where:
MH2O = molar mass of H2O.
pd = saturated vapor pressure at the ambient dry bulb temperature.
RH = relative humidity of ambient air
Mair = molar mass of air.
patmos = atmospheric pressure.
Example:
MH2O = 18.01528 g/mol
pd = 2.93 kPa
RH = 37.5% = 0.375
Mair = 28.96559 g/mol
patmos = 96.71 kPa
(2) Use the following equation to correct measured concentrations to a reference condition of 10.71 grams H2O vapor per kilogram of dry air for the FTP, US06, LA–92, SC03, and HFET test cycles:
Where:
χNOx = measured NOX emission concentration in the sample, after dry-to-wet and background corrections.
Hs = humidity scale. Set = 1 for FTP, US06, LA–92, and HFET test cycles. Set = 0.8825 for the SC03 test cycle.
H = ambient humidity, as determined in paragraph (a)(1) of this section.
Example:
H = 7.14741 g H2O vapor/kg dry air time weighted over the FTP test cycle
χNOx = 1.21 ppm
(b) For vehicles above 14,000 pounds GVWR, apply correction factors as described in 40 CFR 1065.670.
Cite this article: FindLaw.com - Code of Federal Regulations Title 40. Protection of Environment § 40.1066.615 NO X intake-air humidity correction - last updated October 02, 2022 | https://codes.findlaw.com/cfr/title-40-protection-of-environment/cfr-sect-40-1066-615/
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