Browse Publications Technical Papers 2020-01-1634
2020-10-05

Enclosure-In-Chamber Setup to Achieve Near-Zero Background Concentrations for Brake Emissions Testing 2020-01-1634

Measuring brake emission is still a challenging non-standardized task. Extensive research is ongoing. Updates of work in progress are presented at SAE Brake Colloquium and PMP meetings. However, open items include how to achieve lower background concentration and how to design the brake enclosure. A low background concentration is essential as brake events are short and some emit in the range of reported background levels. Hence these emissions are difficult to distinguished from the background level. Even more critical, a high background concentration can result in a wrong particle number emissions value, either overestimated, background counted as emissions, or underestimated, background level subtracted, and low emission events no longer detected and counted. However, reducing the background level to less than 100 #/cm³ appeared to be quite challenging. We applied our experience in validating automotive air filters and industrial HVAC filters and developed a chamber-in-chamber setup. We adapted and implemented the concept for the LINK 3900 dynamometer as for the outer chamber. The brake itself is placed in a rectangular chamber (inner chamber) with easy access to. Key enabler for a background level close to zero are an individual control of the inlet and outlet flow rate to this inner chamber and an additional H13 air filter besides other (sealing) measures. The (outer) chamber of the LINK 3900 is run at negative pressure, to prevent emissions to the workplace, and the inner chamber as an enclosure of the brake has a slight positive pressure to avoid particle intake through the gaps. We present the setup in detail, including ducting, particle measurement (PM and PN) as used for measurements at LINK Limburg, Germany. This work discusses the results showing a background concentration of less than 10 #/cm³ measured with a TSI CPC 3756. This low level of background concentration is stable over the entire cycle time and has been observed for WLTP exhaust as well as the Novel braking cycle (WLTP- Brake Cycle).

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