This paper describes a practical approach used within the UK contribution to the UNECE PMP study in adopting some of the recommendations stated in the draft 2007 regulations for the measurement of particulate mass emissions from heavy-duty diesel engines in the US. This approach was named “2007PM” but the intention was to align rather than fully comply with the draft requirements for the US.
In the PMP test work, four main changes were made to the standard European method of particulate emissions measurement (SPM). These were adopted as the 2007PM method. These were the application of a cyclone pre-classifier to 2007PM - with a 50% cut-size at 2.5μm, the use of a single 47mm filter rather than primary and back-up filters, close control of the filter face temperature to 47°C +/-5°C by heating of the dilution air and an increased filter face velocity. Measurements were predominantly made from aerosols generated by engines equipped with Diesel Particulate Filters (DPFs).
Repeatability day-to-day and within a single day was considerably better with 2007PM than with the SPM method. These improvements were attributed to the removal of the back-up filter and the difference in filter face velocity (or sample flow rate). A further study revealed that filter face velocity was less important than flow rate and filter area.
Overall, the 2007PM system proved to be applicable to both low levels of carbonaceous and post-DPF aerosols. However, mass results from 2007PM were typically lower than observed from simultaneously sampled SPM measurements, though this difference could be virtually eliminated by reintroducing a back-up filter. This suggests that any switch to 2007PM may require a redefinition of engine emissions limits, or the retention of a back-up filter - though this may reduce the level of improvement observed.