Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p53
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 53/71)
Character Range: 359190–361967

flow controller is necessary to maintain a differential pressure of zero between EP and ISP. The adjustment can be done by:

                (a)    controlling the speed or flow of the suction blower SB and keeping the speed or flow of the pressure blower PB constant during each mode (Figure 11); or

                (b)    adjusting the suction blower SB to a constant mass flow of the diluted exhaust gas and controlling the flow of the pressure blower PB, and therefore the exhaust sample flow in a region at the end of the transfer tube TT (Figure 12).

              In the case of a pressure controlled system the remaining error in the control loop must not exceed
              ± 3 Pa. The pressure oscillations in the dilution tunnel must not exceed ± 250 Pa on the average.

              For a multi-tube system (Figure 17), a flow controller is necessary for proportional exhaust splitting to maintain a differential pressure of zero between the exit of the multi-tube unit and the exit of TT. The adjustment is done by controlling the injection air flow rate into DT at the exit of TT.
              PCV1, PCV2 Pressure control valve (Figure 16)

              Two pressure control valves are necessary for the twin venturi/twin orifice system for proportional flow splitting by controlling the backpressure of EP and the pressure in DT. The valves shall be located downstream of SP in EP and between PB and DT.

              DC Damping chamber (Figure 17)

              A damping chamber shall be installed at the exit of the multiple tube unit to minimise the pressure oscillations in the exhaust pipe EP.

              VN Venturi (Figure 15)

              A venturi is installed in the dilution tunnel DT to create a negative pressure in the region of the exit of the transfer tube TT. The gas flow rate through TT is determined by the momentum exchange at the venturi zone, and is basically proportional to the flow rate of the pressure blower PB leading to a constant dilution ratio. Since the momentum exchange is affected by the temperature at the exit of TT and the pressure difference between EP and DT, the actual dilution ratio is slightly lower at low load than at high load.

              FC2 Flow controller (Figures 13, 14, 18, 19, optional)

              A flow controller may be used to control the flow of the pressure blower PB and/or the suction blower SB. It may be connected to the exhaust, intake air, or fuel flow signals and/or to the  CO2  or  NOx  differential signals. When using a pressurised air supply (Figure 18), FC2 directly controls the air flow.

              FM1 Flow measurement device (Figures 11, 12, 18, 19)

              Gas meter or other flow instrumentation to measure the dilution air flow. FM1 is optional if