Division 3.5.3 Exhaust gas molar flow rate

The flow rate of the raw exhaust gas can be directly measured or can be calculated based on the chemical balance of point 3.4.3. Calculation of raw exhaust gas molar flow rate is performed from measured intake air molar flow rate or fuel mass flow rate. The raw exhaust gas molar flow rate can be calculated from the sampled emissions, ṅ_exh , based on the measured intake air molar flow rate, ṅ_int , or the measured fuel mass flow rate, ṁ_fuel , and the values calculated using the chemical balance in point 3.4.3. It shall be solved for the chemical balance in point 3.4.3 at the same frequency that ṅ_int or ṁ_fuel is updated and recorded.

1. (a)

   Crankcase flow rate. The raw exhaust gas flow can be calculated based on ṅ_int or ṁ_fuel only if at least one of the following is true about crankcase emission flow rate:

   1. (i)

      The test engine has a production emission-control system with a closed crankcase that routes crankcase flow back to the intake air, downstream of intake air flow meter;

   2. (ii)

      During emission testing open crankcase flow shall be routed to the exhaust gas according to point 6.10 of Annex VI;

   3. (iii)

      Open crankcase emissions and flow are measured and added brake-specific emission calculations;

   4. (iv)

      Using emission data or an engineering analysis, it can be demonstrated that neglecting the flow rate of open crankcase emissions does not adversely affect compliance with the applicable standards;

2. (b)

   Molar flow rate calculation based on intake air.

   Based on ṅ_int , exhaust gas molar flow rate ṅ_exh [mol/s] shall be calculated by means of equation (7-112):

   ${ṅ}_{\mathrm{exh}}=\frac{{ṅ}_{\mathrm{int}}}{1+\frac{\left(x_{\mathrm{int/exhdry}}-x_{\mathrm{raw/exhdry}}\right)}{\left(1+x_{\mathrm{H2Oexhdry}}\right)}}$

   (7-112)

   Where:

   ṅ _exh

3. raw exhaust gas molar flow rate from which emissions are measured [mol/s]

ṅ _ind

4. intake air molar flow rate including humidity in intake air [mol/s]

x _int/exhdry

5. amount of intake air required to produce actual combustion products per mole of dry (raw or diluted) exhaust gas [mol/mol]

x _raw/exhdry

6. amount of undiluted exhaust gas, without excess air, per mole of dry (raw or diluted) exhaust gas [mol/mol]

x _H2Oexhdry

7. amount of water in exhaust gas per mole of dry exhaust gas [mol/mol]