Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p57
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 57/71)
Character Range: 369644–372653

used to correct the sample flow rate through the particulate filters of the particulate sampling system (see Section 2.4, Figures 21, 22), accordingly.

              DT Dilution tunnel

              The dilution tunnel:

                —    shall be small enough in diameter to cause turbulent flow (Reynolds Number greater than 4 000) and of sufficient length to cause complete mixing of the exhaust and dilution air; a mixing orifice may be used;

                —    shall be at least 460 mm in diameter with a single dilution system;

                —    shall be at least 210 mm in diameter with a double dilution system;

                —    may be insulated.

              The engine exhaust shall be directed downstream at the point where it is introduced into the dilution tunnel, and thoroughly mixed.

              When using single dilution, a sample from the dilution tunnel is transferred to the particulate sampling system (Section 2.4, Figure 21). The flow capacity of the PDP or CFV must be sufficient to maintain the diluted exhaust at a temperature of less than or equal to 325 K (52 °C) immediately before the primary particulate filter.

              When using double dilution, a sample from the dilution tunnel is transferred to the secondary dilution tunnel where it is further diluted, and then passed through the sampling filters (Section 2.4, Figure 22). The flow capacity of the PDP or CFV must be sufficient to maintain the diluted exhaust stream in the DT at a temperature of less than or equal to 464 K (191 °C) at the sampling zone. The secondary dilution system must provide sufficient secondary dilution air to maintain the doubly-diluted exhaust stream at a temperature of less than or equal to 325 K (52 °C) immediately before the primary particulate filter.

              DAF Dilution air filter

              It is recommended that the dilution air be filtered and charcoal scrubbed to eliminate background hydrocarbons. At the engine manufacturers request the dilution air shall be sampled according to good engineering practice to determine the background particulate levels, which can then be subtracted from the values measured in the diluted exhaust.

              PSP Particulate sampling probe

              The probe is the leading section of PTT and:

                —    shall be installed facing upstream at a point where the dilution air and exhaust gas are well mixed, i.e. on the dilution tunnel (DT) centreline approximately 10 tunnel diameters downstream of the point where the exhaust enters the dilution tunnel;

                —    shall be of 12 mm minimum inside diameter;

                —    may be heated to no greater than 325 K (52 °C) wall temperature by direct heating or by dilution air pre-heating, provided the air temperature does not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel;

                —    may be insulated.

2.4.                            Particulate sampling system