We invite you to try out our new beta eCFR site at
https://ecfr.federalregister.gov. We have made big
changes to make the eCFR easier to use. Be sure to leave feedback using the Feedback button on the bottom
right of each page!

e-CFR data is current as of November 23, 2020 |

Title 40 → Chapter I → Subchapter U → Part 1066 → Subpart G → §1066.630 |

Title 40: Protection of Environment

PART 1066—VEHICLE-TESTING PROCEDURES

Subpart G—Calculations

This section describes the equations for calculating flow rates from various flow meters. After you calibrate a flow meter according to §1066.625, use the calculations described in this section to calculate flow during an emission test. Calculate flow according to 40 CFR 1065.642 instead if you calculate emissions based on molar flow rates.

(a) PDP. (1) Based on the speed at which you operate the PDP for a test interval, select the corresponding slope, a1, and intercept, a0, as determined in §1066.625(a), to calculate PDP flow rate, v̇, as follows:

Where:

fnPDP = pump speed.

Vrev = PDP volume pumped per revolution, as determined in paragraph (a)(2) of this section.

Tstd = standard temperature = 293.15 K.

pin = static absolute pressure at the PDP inlet.

Tin = absolute temperature at the PDP inlet.

pstd = standard pressure = 101.325 kPa.

(2) Calculate Vrev using the following equation:

pout = static absolute pressure at the PDP outlet.

Example:

a1 = 0.8405 m3/s

fnPDP = 12.58 r/s

pout = 99.950 kPa

pin = 98.575 kPa

a0 = 0.056 m3/r

Tin = 323.5 K

Vrev = 0.063 m3/r

v̇= 0.7079 m3/s

(b) SSV. Calculate SSV flow rate, v̇, as follows:

Where:

Cd = discharge coefficient, as determined based on the Cd versus Re# equation in §1066.625(b)(2)(viii).

Cf = flow coefficient, as determined in §1066.625(b)(2)(ii).

At = venturi throat cross-sectional area.

R = molar gas constant.

pin = static absolute pressure at the venturi inlet.

Tstd = standard temperature.

pstd = standard pressure.

Z = compressibility factor.

Mmix = molar mass of gas mixture.

Tin = absolute temperature at the venturi inlet.

Example:

Cd = 0.890

Cf = 0.472

At = 0.01824 m2

R = 8.314472 J/(mol·K) = 8.314472 (m2·kg)/(s2·mol·K)

pin = 98.496 kPa

Tstd = 293.15 K

pstd = 101.325 kPa

Z = 1

Mmix = 28.7789 g/mol = 0.0287789 kg/mol

Tin = 296.85 K

V̇ = 2.155 m3/s

(c) CFV. If you use multiple venturis and you calibrated each venturi independently to determine a separate calibration coefficient, Kv, for each venturi, calculate the individual volume flow rates through each venturi and sum all their flow rates to determine CFV flow rate, V̇. If you use multiple venturis and you calibrated venturis in combination, calculate V̇ using the Kv that was determined for that combination of venturis.

(1) To calculate V̇ through one venturi or a combination of venturis, use the mean Kv you determined in §1066.625(c) and calculate V̇ as follows:

Where:

Kv = flow meter calibration coefficient.

Tin = temperature at the venturi inlet.

pin = absolute static pressure at the venturi inlet.

Example:

Kv = 0.074954 m3·K0.5/(kPa·s)

pin = 99.654 kPa

Tin = 353.15 K

V̇= 0.39748 m3/s

(2) [Reserved]

[81 FR 74211, Oct. 25, 2016]