(a) Derive the final weighted brake-specific mass emission rates (g/kW-hr) through the steps described in this section.
(b) Air and fuel flow method. If both air and fuel flow mass rates are measured, use the following equations to determine the weighted emission values for the test engine: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where: WHC = Mass rate of HC in exhaust [g/hr], GAIRD = Intake air mass flow rate on dry basis [g/hr],GFUEL = Fuel mass flow rate [g/hr],MHCexh = Molecular weight of hydrocarbons in the exhaust, see
the following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: [alpha] = Hydrogen/carbon atomic ratio of the fuel[beta] = Oxygen/carbon atomic ratio of the fuelMexh = Molecular weight of the total exhaust, see the
following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: WHC = HC volume concentration in exhaust, ppmC wetWCO = CO percent concentration in the exhaust, wetDCO = CO percent concentration in the exhaust, dryWCO2 = CO2 percent concentration in the exhaust,
wetDCO2 = CO2 percent concentration in the exhaust,
dryWNOX = NO volume concentration in exhaust, ppm wetWO2 = O2 percent concentration in the exhaust, wetWH2 = H2 percent concentration in exhaust, wetK = correction factor to be used when converting dry measurements to a
wet basis. Therefore, wet concentration=dry concentration x K,where K is: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] DH2 = H2 percent concentration in exhaust, dry,
calculated from the following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Wco = Mass rate of CO in exhaust, [g/hr]Mco = Molecular weight of CO=28.01WNOx = Mass rate of NOX in exhaust, [g/hr]MNO2 = Molecular weight of NO2=46.01KH = Factor for correcting the effects of humidity on
NO2 formation for 4-stroke gasoline small engines,
as follows: KH = (9.953 x H + 0.832) Where: H = the amount of water in an ideal gas; 40 CFR 1065.645 describes how
to determine this value (referred to as
xH2O).KH = 1 for two-stroke gasoline engines.
(c) Fuel flow method. The following equations are to be used when fuel flow is selected as the basis for mass emission calculations using the raw gas method. [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where:WHC = Mass rate of HC in exhaust, [g/hr]MHCexh = Molecular weight of hydrocarbons in the exhaust, see
following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
MC = Molecular weight of carbon=12.01 [g/mole]MH = Molecular weight of hydrogen=1.008 [g/mole]MO = Molecular weight of oxygen=16.00 [g/mole][alpha] = Hydrogen to carbon ratio of the test fuel[beta] = Oxygen to carbon ratio of the test fuelMF = Molecular weight of test fuelGFUEL = Fuel mass flow rate, [g/hr]TC=Total carbon in exhaust, see following equation: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] WCO = CO percent concentration in the exhaust, wetWCO2 = CO2 percent concentration in the exhaust,
wetDCO = CO percent concentration in the exhaust, dryDCO2 = CO2 percent concentration in the exhaust,
dryWHC = HC volume concentration in exhaust, ppmC wetWNOX = NOX volume concentration in exhaust, ppm
wetK = correction factor to be used when converting dry measurements to a
wet basis. Therefore, wet concentration=dry concentrationxK,
where K is:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
DH2 = H2 percent concentration in exhaust, dry,
calculated from the following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
WCO = Mass rate of CO in exhaust, [g/hr]MCO = Molecular weight of CO = 28.01WNOX = Mass rate of NOX in exhaust, [g/hr]MNO2 = Molecular weight of NO2=46.01
KH = Factor for correcting the effects of humidity on NO2 formation for 4-stroke gasoline small engines, as follows:
KH = (9.953 x H + 0.832) Where: H = the amount of water in an ideal gas; 40 CFR 1065.645 describes how
to determine this value (referred to as
xH2O).KH = 1 for two-stroke gasoline engines.
(d) Calculate the final weighted brake-specific emission rate for each individual gas component using the following equation: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where:AWM = Final weighted brake-specific mass emission rate (HC,
CO, NOX) [g/kW-hr]Wi = Mass emission rate during mode i [g/hr]WFi = Weighting factors for each mode according to
Sec. 90.410(a)Pi = Gross average power generated during mode i [kW],
calculated from the following equation,
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: speed = average engine speed measured during mode i [rev./minute]torque = average engine torque measured during mode i [N-m] [60 FR 34598, July 13, 1995, as amended at 70 FR 40449, July 13, 2005]