Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p16
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 16/56)
Character Range: 339037–341941

is the instantaneous fuel mass flow rate, kg/s
 The flowmeters shall meet the linearity requirements of paragraph 9.2., but shall be accurate enough to also meet the linearity requirements for the exhaust gas flow.
8.4.1.5. Tracer measurement method
 This involves measurement of the concentration of a tracer gas in the exhaust.
 A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but shall not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample.
 In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine.
 The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyzer.
 The calculation of the exhaust gas flow shall be as follows:
  (29)
 Where:
                  qmew,i is the instantaneous exhaust mass flow rate, kg/s
                  qvt is tracer gas flow rate, cm³/min
                  cmix,i is the instantaneous concentration of the tracer gas after mixing, ppm
                  e is the density of the exhaust gas, kg/m³ (see Table 5)
                  cb is the background concentration of the tracer gas in the intake air, ppm
 The background concentration of the tracer gas (cb) may be determined by averaging the background concentration measured immediately before the test run and after the test run.
 When the background concentration is less than 1 per cent of the concentration of the tracer gas after mixing (cmix.i) at maximum exhaust flow, the background concentration may be neglected.
 The total system shall meet the linearity requirements for the exhaust gas flow of paragraph 9.2.
8.4.1.6. Airflow and air to fuel ratio measurement method
 This involves exhaust mass calculation from the air flow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows:
  (30)
 With
                      (31)

                     (32)
 Where:
                  qmaw,i is the instantaneous intake air mass flow rate, kg/s
                  A/Fst is the stoichiometric air to fuel ratio, kg/kg
                  i is the instantaneous excess air ratio
                  cCO2d is the dry CO2 concentration, per cent
                  cCOd is the dry CO concentration, ppm
                  cHCw is the wet HC concentration, ppm
 Air flow meter and analyzers shall meet the linearity