Methodology of diesel particulate filter testing on test bed for non-road engine application

This paper describes the methodology and test results of diesel particulate filter (DPF) functional testing performed on non-road compression ignition engine installed on test bed. The scope of work included testing of various DPF regeneration strategies, backpressure and balance point tests and emission performance evaluation during a legislative test cycles. The aim of this study was to observe and investigate the influence of exhaust gas parameters on DPF functionality in terms of soot loading, type and duration of the regeneration and emission performance. Under investigation was also the capability of soot burning rate. The DPF sample under test was part of the complete exhaust aftertreatment system (ATS) which consisted of: a diesel oxidation catalyst (DOC), a DPF and a selective catalytic reduction system (SCR). Testing was carried out on a heavy-duty diesel engine installed on a test stand with a dynamic dynamometer and equipped with an emission bench. The test program allowed to assess the engine matching to exhaust aftertreatment system with regard to emissions compliance, in-service operation and necessary engine control unit (ECU) calibration works. The results show the influence of the DPF regeneration strategy on its duration and on the soot mass burn rate. Passive DPF regeneration was a favorable mode of DPF cleaning, due to lack of fuel penalty and lower aging impact on the entire ATS. Optimization of soot flow rate, exhaust gas temperature and the chemistry of the DOC/DPF was further recommended to ensure the long-term durability of the entire system.

Concepts for Hydrogen Internal Combustion Engines and Their Implications on the Exhaust Gas Aftertreatment System

Hydrogen as carbon-free fuel is a very promising candidate for climate-neutral internal combustion engine operation. In comparison to other renewable fuels, hydrogen does obviously not produce CO2 emissions. In this work, two concepts of hydrogen internal combustion engines (H2-ICEs) are investigated experimentally. One approach is the modification of a state-of-the-art gasoline passenger car engine using hydrogen direct injection. It targets gasoline-like specific power output by mixture enrichment down to stoichiometric operation. Another approach is to use a heavy-duty diesel engine equipped with spark ignition and hydrogen port fuel injection. Here, a diesel-like indicated efficiency is targeted through constant lean-burn operation. The measurement results show that both approaches are applicable. For the gasoline engine-based concept, stoichiometric operation requires a three-way catalyst or a three-way NOX storage catalyst as the primary exhaust gas aftertreatment system. For the diesel engine-based concept, state-of-the-art selective catalytic reduction (SCR) catalysts can be used to reduce the NOx emissions, provided the engine calibration ensures sufficient exhaust gas temperature levels. In conclusion, while H2-ICEs present new challenges for the development of the exhaust gas aftertreatment systems, they are capable to realize zero-impact tailpipe emission operation.

Effects of Renewable Diesel Exhaust on Lung Function and Self-rated Symptoms for Healthy Volunteers in a Human Chamber Exposure Study

Background: Diesel engine exhaust causes adverse health effects. Meanwhile, the impact of renewable diesel exhaust on human health is less known. In this study, nasal patency, pulmonary function, and self-rated symptoms were assessed in 19 healthy volunteers after two separate 3-hour exposures to renewable diesel (hydrotreated vegetable oil [HVO]) exhaust, and exposure to filtered air (FA) for comparison. The HVO exposures were generated with two modern non-road vehicles (2019) having either: 1) no aftertreatment system (HVOPM+NOx), or 2) an aftertreatment system containing a diesel oxidation catalyst and a diesel particulate filter (HVONOx). The exposure concentrations complied with current EU occupational exposure limits (OELs) of NO, NO2, formaldehyde, polycyclic aromatic hydrocarbons (PAHs), and future OELs of elemental carbon (EC) from 2023. Results: Exposure to HVOPM+NOx consisted of PM1 (≈90 µg m-3, 54 µg m-3 EC) and NOx (NO 3.4 ppm, NO2 0.6 ppm). The average total respiratory tract deposition of PM1 was 27 µg h-1. The deposition fraction of HVO PM1 was 40-50% higher compared to diesel exhaust PM1 from an older vehicle, due to smaller particle sizes of the HVOPM+NOx exhaust. Exposure to HVONOx consisted mainly of NOx (NO 2.0 ppm, NO2 0.7 ppm) with low level of PM1 (~1 µg m-3). Compared to filtered air, exposure to HVOPM+NOx and HVONOx caused higher incidence of self-reported symptoms (78%, 63%, respectively, vs. 28% for FA, p<0.03). Especially, exposure to HVOPM+NOx showed 40-50% higher eye and throat irritation symptoms. Compared to filtered air, a decrement in nasal patency was found for the HVONOx exposures (-18.1, 95%CI: -27.3 to -8.8 L min-1), and for the HVOPM+NOx (-7.4 (-15.6 to 0.8) L min-1). Overall, no change was indicated in the pulmonary function tests (spirometry, peak expiratory flow, forced oscillation technique), except a slight increase in FEV1/FVC after exposure to HVONOx.Conclusion: Short-term exposure to HVO exhaust below the EU OELs did not cause severe pulmonary function changes in healthy subjects. However, an increase in self-rated mild irritation symptoms, and mild decrease in nasal patency after two HVO exposures may indicate irritative effects from exposure to HVO exhaust from modern non-road vehicles below future OELs.