See the standard-setting part to determine if you may correct NOX emissions for the effects of intake-air humidity or temperature. Use the NOX intake-air humidity and temperature corrections specified in the standard-setting part instead of the NOX intake-air humidity correction specified in this part 1065. If the standard-setting part does not prohibit correcting NOX emissions for intake-air humidity according to this part 1065, correct NOX concentrations for intake-air humidity as described in this section. See Sec. 1065.650(c)(1) for the proper sequence for applying the NOX intake-air humidity and temperature corrections. You may use a time-weighted mean combustion air humidity to calculate this correction if your combustion air humidity remains within a tolerance of 0.0025 mol/mol of the mean value over the test interval. For intake-air humidity correction, use one of the following approaches:
See the standard-setting part to determine if you may correct NOX emissions for the effects of intake-air humidity or temperature. Use the NOX intake-air humidity and temperature corrections specified in the standard-setting part instead of the NOX intake-air humidity correction specified in this part 1065. If the standard-setting part does not prohibit correcting NOX emissions for intake-air humidity according to this part 1065, first apply any NOX corrections for background emissions and water removal from the exhaust sample, then correct NOX concentrations for intake-air humidity. You may use a time-weighted mean combustion air humidity to calculate this correction if your combustion air humidity remains within a tolerance of 0.0025 mol/mol of the mean value over the test interval. For intake-air humidity correction, use one of the following approaches:
(a) For compression-ignition engines, correct for intake-air humidity using the following equation:[GRAPHIC] [TIFF OMITTED] TR30AP10.095 Example: xNOxuncor = 700.5 [micro]mol/molxH2O = 0.022 mol/molxNOxcor = 700.5 [middot] (9.953 [middot] 0.022 + 0.832)xNOxcor = 736.2 [micro]mol/mol
(b) For spark-ignition engines, correct for intake-air humidity using the following equation: [GRAPHIC] [TIFF OMITTED] TR30AP10.096 Example: xNOxuncor = 154.7 [micro]mol/molxH2O = 0.022 mol/molxNOxcor = 154.7 [middot] (18.840 [middot] 0.022 + 0.68094)xNOxcor = 169.5 [micro]mol/mol
(c) Develop your own correction, based on good engineering judgment. [75 FR 23056, Apr. 30, 2010, as amended at 76 FR 57466, Sept. 15, 2011]