Ploughing ahead with tractor testing

Working with Emissions Analytics, engineering researchers at Harper Adams University have developed a new method to accurately measure the exhaust emissions of agricultural machinery.

Traditionally, machines such as tractors are tested in controlled environments such as a soil hall, not taking into account the many variables from real-life scenarios, which result in transient engine loads.

With support from CLAAS and EA, the postgraduate students used PEMS equipment quite literally in the field. Two engine exhaust after treatment systems commonly used by tractors to reduce emissions were tested; a CLAAS Axion 830 with a selective catalytic reduction system and a CLAAS Arion 650 using exhaust gas recirculation combined with a diesel particulate filter.

Both tractors were trialled in three conditions – using a dynamometer to add a variable load to the PTO shaft; road testing at high speed with a fully laden trailer; and in a field with a subsoiler and power harrow. As with road vehicles the CO, CO2, NOx and THC data was combined with vehicle data such as GPS position, engine load and speed.

The project was designed to investigate the differences between theoretical CO2 conversion factors and real-world factors for non-road mobile machinery; and to demonstrate the feasibility of using PEMS equipment for such a task. The results, analysed by Miles Metcalfe with supervision from PhD student Rob Fillingham, were written up for his MEng Agricultual Engineering dissertation for which he was awarded a first class.

Metcalfe demonstrated that the assumed linear relationship between engine load and CO2 conversion factor was in fact better suited to an exponential curve, and that by using the traditional conversion factors supplied by DEFRA, CO2 is in fact being over estimated as there is a significant difference of p<0.001 between the DEFRA value and the PEMS result.

IMG_1470Observations made, such as an increase in CO2 conversion factors whilst the tractor was turning at lower engine speeds or loads at the field’s headlands, show that this innovative collaboration between Emissions Analytics and the agricultural sector has the potential to allow farmers to not only save fuel but reduce damaging emissions by using data gathered from real agricultural practices. And, as regulations change for N-RMM, the  power of PEMS to measure compliance is evident.