Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p8
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 8/27)
Character Range: 571108–574156

type (as described in Appendix 2 to this annex, paragraph A.2.2.1.) the sampling probe shall be installed near the tunnel centre line, 10 to 20 tunnel diameters downstream of the gas inlet, facing upstream into the tunnel gas flow with its axis at the tip parallel to that of the dilution tunnel. The sampling probe shall be positioned within the dilution tract so that the sample is taken from a homogeneous diluent/exhaust mixture.
               In the case of partial flow dilution systems of the total sampling type (as described in Appendix 2 to this annex, paragraph A.2.2.1.) the particle sampling point shall be located in the particulate transfer tube, upstream of the particulate filter holder, flow measurement device and any sample/bypass bifurcation point. The sampling point or sampling probe shall be positioned so that the sample is taken from a homogeneous diluent/exhaust mixture.
               Sample gas drawn through the PTS shall meet the following conditions:
               It shall have a flow Reynolds number (Re) of < 1,700;
               It shall have a residence time in the PTS of ≤ 3 seconds.
               Any other sampling configuration for the PTS for which equivalent particle penetration for particles of 30 nm electrical mobility diameter can be demonstrated will be considered acceptable.
               The outlet tube (OT) conducting the diluted sample from the VPR to the inlet of the PNC shall have the following properties:
               It shall have an internal diameter of ≥ 4 mm;
               Sample gas flow through the POT shall have a residence time of ≤ 0.8 second.
               Any other sampling configuration for the OT for which equivalent particle penetration for particles of 30 nm electrical mobility diameter can be demonstrated will be considered acceptable.
              A.8.1.4.3. Particle pre-classifier
               The recommended particle pre-classifier shall be located upstream of the VPR. The pre-classifier 50 per cent cut point particle diameter shall be between 2.5 µm and 10 µm at the volumetric flow rate selected for sampling particle number emissions. The pre-classifier shall allow at least 99 per cent of the mass concentration of 1 µm particles entering the pre-classifier to pass through the exit of the pre-classifier at the volumetric flow rate selected for sampling particle number emissions. In the case of partial flow dilution systems, it is acceptable to use the same pre-classifier for particulate mass and particle number sampling, extracting the particle number sample from the dilution system downstream of the pre-classifier. Alternatively separate pre-classifiers may be used, extracting the particle number sample from the dilution system upstream of the particulate mass pre-classifier.
              A.8.1.4.4. Volatile particle remover (VPR)
               The VPR shall comprise one particle number diluter (PND1), an evaporation tube and a second diluter (PND2) in series. This dilution function is to reduce the number concentration of