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.

On the mechanism of carrier recombination in downsized blue micro-LEDs

The mechanism of carrier recombination in downsized μ-LED chips from 100 × 100 to 10 × 10 μm2 on emission performance was systemically investigated. All photolithography processes for defining the μ-LED pattern were achieved by using a laser direct writing technique. This maskless technology achieved the glass-mask-free process, which not only can improve the exposure accuracy but also save the development time. The multi-functional SiO2 film as a passivation layer successfully reduced the leakage current density of μ-LED chips compared with the μ-LED chips without passivation layer. As decreasing the chip size to 10 × 10 μm2, the smallest chip size exhibited the highest ideality factor, which indicated the main carrier recombination at the high-defect-density zone in μ-LED chip leading to the decreased emission performance. The blue-shift phenomenon in the electroluminescence spectrum with decreasing the μ-LED chip size was due to the carrier screening effect and the band filling effect. The 10 × 10 μm2 μ-LED chip exhibited high EQE values in the high current density region with a less efficiency droop, and the max-EQE value was 18.8%. The luminance of 96 × 48 μ-LED array with the chip size of 20 × 20 μm2 exhibited a high value of 516 nits at the voltage of 3 V.

Emission performance of major ship classes: An estimation based on a new set of emission factors and realistic activity profile data

The maritime sector significantly contributes on the major environmental problems that humanity is being confronted with their consequences. The Greenhouse Gases (GHGs) emitted from the sector, which are responsible for the global phenomenon of climate change, are estimated in 2,89% of total anthropogenic GHGs. Ships are also an important source of local air-quality degradation in coastal areas by emitting major quantities of pollutants such as Nitrogen Oxides (NOx), Sulphur Oxides (SOx) and Particulate Matter (PM). The overall emitted quantities of the sector seem not to be equally allocated to the major ship classes (containers, dry and liquid bulk carriers, cruise ships, ro-ro ships etc.), even though the engine technologies that are being used in these classes are approximately the same (slow speed, medium speed, high speed diesel engines). A factor of differentiation among the ship types is the activity profile. Depending on the ship type, engines (main, auxiliary, boilers) present different power needs and therefore are being operated at different load points which among others are related with the sailing profile (cruising, maneuvering, hoteling), the cargo type and weight conditions (laden, ballast). In this context the target of the present paper is to evaluate the emission performance of the major ship classes. This evaluation is performed by using a new set of engine load-dependent Emission Factors for ships, which have been derived by a statistical analysis of emission rates found in literature, in combination with average activity profiles per ship type as these are found in dedicated shipping inventory databases and in literature. These activity data concern a global scale of consideration. Results aim to highlight the differences and similarities in the emission performance of ship types, enhancing the understanding of policy makers and ship operators, on the principle of tackling pollutants especially at ports, close to cities.