['Air Programs']
['Mobile Emission Sources']
07/23/2024
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(a) The following equations are used to calculate the evaporative emissions from gasoline- and methanol-fueled vehicles, and for gaseous-fueled vehicles.
(b) Use the measurements of initial and final concentrations to determine the mass of hydrocarbons and methanol emitted. For testing with pure gasoline, methanol emissions are assumed to be zero.
(1) For enclosure testing of diurnal, hot soak, and running loss emissions:
(i) Methanol emissions:
Where:
MCH3OH = Methanol mass change, μg.
Vn = Net enclosure volume, ft 3 , as determined by subtracting 50 ft 3 (volume of vehicle with trunk and windows open) from the enclosure volume. A manufacturer may use the measured volume of the vehicle (instead of the nominal 50 ft 3) with advance approval by the Administrator: Provided, the measured volume is determined and used for all vehicles tested by that manufacturer.
TE = Temperature of sample withdrawn, R.
f = Final sample.
CMS = GC concentration of sample, μg/ml.
1 = First impinger.
AV = Volume of absorbing reagent in impinger.
2 = Second impinger.
VE = Volume of sample withdrawn, ft 3 . Sample volumes must be corrected for differences in temperature to be consistent with determination of Vn, prior to being used in the equation.
TSHED = Temperature of SHED, R.
i = Initial sample.
MCH3OH,out = mass of methanol exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, μg.
MCH3OH,in = mass of methanol entering the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, μg.
(ii) Hydrocarbon emissions:
Where,
(A) MHC = Hydrocarbon mass change, g.
(B) CHC = FID hydrocarbon concentration as ppm including FID response to methanol (or methane, as appropriate) in the sample.
(C) CCH3OH = Methanol concentration as ppm carbon.
(D) Vn = Net enclosure volume ft 3 (m 3) as determined by subtracting 50 ft 3 (1.42 m 3) (volume of vehicle with trunk and windows open) from the enclosure volume. A manufacturer may use the measured volume of the vehicle (instead of the nominal 50 ft 3) with advance approval by the Administrator, provided the measured volume is determined and used for all vehicles tested by that manufacturer.
(E) r = FID response factor to methanol.
(F) PB = Barometric pressure, in Hg (Kpa).
(G) T = Enclosure temperature,°R(°K).
(H) i = initial reading.
(I) f = final reading.
(J) 1 = First impinger.
(K) 2 = Second impinger.
(L) Assuming a hydrogen to carbon ratio of 2.3:
(1) k = 2.97; and
(2) For SI units, k = 17.16.
(M) MHC, out = mass of hydrocarbons exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, g.
(N) MHC, in = mass of hydrocarbons entering the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, g.
(iii) For variable-volume enclosures, defined in §86.107(a)(1)(i), the following simplified form of the hydrocarbon mass change equation may be used:
(2) For running loss testing by the point-source method, the mass emissions of each test phase are calculated below, then summed for a total mass emission for the running loss test. If emissions are continuously sampled, the following equations can be used in integral form.
(i) Methanol emissions:
MCH3OH = ρCH3OH Vmix ×
(CCH3OH, rl−CCH3OH, d)
Where,
(A) MCH3OH = methanol mass change, µg.
(B) ρCH3,OH = 37.71 g/ft 3, density of pure vapor at 68°F.
(C) Vmix = total dilute sample volume, in ft 3, calculated as appropriate for the collection technique used.
(D) CCH3OH, rl = methanol concentration of diluted running loss sample, in ppm carbon equivalent.
(E) CCH3OH, d = methanol concentration of dilution air, in ppm carbon equivalent.
(ii) Hydrocarbon emissions:
MHC = ρHC Vmix10−6 × (CHC, rl−CHC, d)
Where,
(A) MHC = hydrocarbon mass change, g.
(B) ρHC = 16.88 g/ft 3, density of pure vapor at 68°F (for hydrogen to carbon ratio of 2.3).
(C) Vmix = total dilute sample volume, in ft 3, calculated as appropriate for the collection technique used.
(D) CHC, rl = hydrocarbon concentration of diluted running loss sample, in ppm carbon equivalent.
(E) CHC, d = hydrocarbon concentration of dilution air, in ppm carbon equivalent.
(c) If the test fuel contains at least 25% oxygenated compounds by volume, measure the concentration of oxygenated compounds directly using a photoacoustic analyzer specified in 40 CFR 1065.269 or using impingers as described in 40 CFR 1065.805(f). Calculate total hydrocarbon equivalent emissions with the following equation, using density values specified in 40 CFR 1066.1005(f):
Where:
mTHCE = the sum of the mass of THCE in the SHED.
mTHC = the mass of THC and all oxygenated hydrocarbons in the SHED, as measured by the FID. Calculate THC mass based on ρTHC.
rTHC = the effective C1-equivalent density of THC as specified in 40 CFR 1066.1005(f).
mOHCi = the mass of oxygenated species i in the SHED.
rOHCi = the C1-equivalent density of oxygenated species i.
RFOHCi[THC-FID] = the response factor of a THC-FID to oxygenated species i relative to propane on a C1-equivalent basis as determined in 40 CFR 1065.845.
(d)(1) For the full three-diurnal test sequence, there are two final results to report:
(i) The sum of the adjusted total mass emissions for the diurnal and hot soak tests (MDI + MHS); and
(ii) The adjusted total mass emissions for the running loss test, on a grams per mile basis = MRL/DRL, where DRL = miles driven for the running loss test (see §86.134-96(c)(6)).
(2) For the supplemental two-diurnal test sequence, there is one final result to report: the sum of the adjusted total mass emissions for the diurnal and hot soak tests (MDI + MHS), described in §§86.133-96(p) and §86.138-96(k), respectively.
[58 FR 16043, Mar. 24, 1993, as amended at 59 FR 48510, Sept. 21, 1994; 60 FR 34348, June 30, 1995; 60 FR 43897, Aug. 23, 1995; 79 FR 23698, Apr. 28, 2014; 81 FR 73979, Oct. 25, 2016; 88 FR 4475, Jan. 24, 2023]
['Air Programs']
['Mobile Emission Sources']