Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:10:p1
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 10 (pt 1/3)
Character Range: 535942–538570

10           9, 9    2.440  9       1.833

Annex 4 ‑ Appendix 4 Carbon flow check
A.4.1. Introduction
 All but a tiny part of the carbon in the exhaust comes from the fuel, and all but a minimal part of this is manifest in the exhaust gas as CO2. This is the basis for a system verification check based on CO2 measurements.
 The flow of carbon into the exhaust measurement systems is determined from the fuel flow rate. The flow of carbon at various sampling points in the emissions and particulate sampling systems is determined from the CO2 concentrations and gas flow rates at those points.
 In this sense, the engine provides a known source of carbon flow, and observing the same carbon flow in the exhaust pipe and at the outlet of the partial flow PM sampling system verifies leak integrity and flow measurement accuracy. This check has the advantage that the components are operating under actual engine test conditions of temperature and flow.
 Figure 18 shows the sampling points at which the carbon flows shall be checked. The specific equations for the carbon flows at each of the sample points are given below.
              Figure 18
              Measuring points for carbon flow check
A.4.2. Carbon flow rate into the engine (location 1)
 The carbon mass flow rate into the engine for a fuel CHO is given by:
 (112)
 Where:
 qmf is the fuel mass flow rate, kg/s
A.4.3. Carbon flow rate in the raw exhaust (location 2)
 The carbon mass flow rate in the exhaust pipe of the engine shall be determined from the raw CO2 concentration and the exhaust gas mass flow rate:
 (113)
 Where:
 cCO2,r is the wet CO2 concentration in the raw exhaust gas, per cent
 cCO2,a is the wet CO2 concentration in the ambient air, per cent
 qmew is the exhaust gas mass flow rate on wet basis, kg/s
 Me is the molar mass of exhaust gas, g/mol
 If CO2 is measured on a dry basis it shall be converted to a wet basis according to paragraph 8.1. of this annex.
A.4.4. Carbon flow rate in the dilution system (location 3)
 For the partial flow dilution system, the splitting ratio also needs to be taken into account. The carbon flow rate shall be determined from the dilute CO2 concentration, the exhaust gas mass flow rate and the sample flow rate:
 (114)
 Where:
                  cCO2,d is the wet CO2 concentration in the dilute exhaust gas at the outlet of the dilution tunnel, per cent
                  cCO2,a is the wet CO2 concentration in the ambient air, per cent
                  qmew is the exhaust gas mass flow rate on wet basis, kg/s
                  qmp is the sample flow of exhaust gas into partial flow dilution