Division 3.7.1 Sampling

United Kingdom

(a)

Sampling from a varying flow rate:

If a batch sample from a changing exhaust gas flow rate is collected, a sample proportional to the changing exhaust gas flow rate shall be extracted. The flow rate shall be integrated over a test interval to determine the total flow. The mean PM concentration ${\bar{M}}_{PM}$ (which is already in units of mass per mole of sample) shall be multiplied by the total flow to obtain the total mass of PM m _PM [g] by means of equation (7-121):

m_{PM} = {\bar{M}}_{PM} \times \sum_{i = 1}^{N} (ṅ_{i} \times Δ t_{i})

(7-121)

Where:

ṅ_i

instantaneous exhaust gas molar flow rate [mol/s]

{\bar{M}}_{PM}

mean PM concentration [g/mol]

t_i

sampling interval [s]

(b)

Sampling from a constant flow rate

If a batch sample from a constant exhaust gas flow rate is collected, the mean molar flow rate from which the sample is extracted shall be determined. The mean PM concentration shall be multiplied by the total flow to obtain the total mass of PM m _PM[g] by means of equation (7-122):

m_{PM} = {\bar{M}}_{PM} \times ṅ \times Δ t

(7-122)

where:

ṅ

exhaust gas molar flow rate [mol/s]

{\bar{M}}_{PM}

mean PM concentration [g/mol]

Δt

time duration of test interval [s]

For sampling with a constant dilution ratio (DR), m _PM [g] shall be calculated by means of equation (7-123):

m_{PM} = m_{PMdil} \times DR

(7-123)

where:

m _PMdil

PM mass in dilution air [g]

dilution ratio [-] defined as the ratio between the mass of the emission m and the mass of diluted exhaust gas m _dil/exh (DR = m/m _dil/exh).

The dilution ratio DR can be expressed as a function of x _dil/exh [equation (7-124)]:

DR = \frac{1}{1 - x_{dil ∕ exh}}

(7-124)