Search

This paper reports a low NOx and low smoke combustion concept for a DI diesel engine and an investigation into its combustion characteristics. In this concept of combustion, using a high EGR rate combining with head swirl, combustion chamber design and optimal injection timing, the combustion process occurred under a moderate reaction rate with greatly improved fuel mixing. As a result, both NOx and smoke emissions were reduced considerably. [ABSTRACT FROM AUTHOR]

Pre-mixed compression ignition (PCI) combustion of low NOx emission was realized in a multi cylinder diesel engine on a previous paper. The PCI combustion operation is limited on a low load and it must be transitioning to conventional combustion at a high load condition. In addition, black smoke emission was observed at transition process from PCI to conventional combustion on a vehicle. Control method of combustion mode transition of PCI combustion was researched with parametric study in this paper. And control method was developed with no increasing of NOx and SOOT emissions on combustion mode transition process. [ABSTRACT FROM AUTHOR]

Pre-mixed compression ignition (PCI) combustion of low NOx emission was applied to a multi cylinder diesel engine in a previous paper. It is known that the ignition timing varies with the ignitability of fuel (i.e., cetane number) in PCI combustion. For the commodification of a PCI combustion engine, it would be necessary to detect the start of combustion (SOC) timing and to compensate with the difference in cetane number. This paper shows the results of SOC detection and feedback control in PCI combustion using a knock sensor for a gasoline engine. [ABSTRACT FROM AUTHOR]

Many researchers have been investigating HCCI like combustion that can realize low NOx and SOOT emissions on DI diesel engines. Based on the study in the single cylinder research engine, we have tried to apply the Pre-mixed Compression Ignition (PCI) combustion on the multi cylinder diesel engine in this study. Minimizing the engine hardware modification and using rapid prototyping software development tools, PCI combustion was realized on the part load conditions frequently used in real driving cycle. After the investigations in engine test cell, PCI combustion showed the drastic reduction of NOx emission on the vehicle emission cycle. [ABSTRACT FROM AUTHOR]

Pulsed cathodic arc-plasma deposition was employed to create a few nanometre-thick Pt overlayer on a 50 μm-thick Fe-Cr-Al metal (SUS) foil, resulting in an effective NH 3 oxidation catalyst fabrication. This catalyst exhibited a turnover frequency (TOF) exceeding 100 times that of Pt nanoparticles. In this study, Pt overlayer catalysts with varying degrees of surface roughness were fabricated using different metal foil substrates: mirror-polished (Pt/p-SUS), unpolished (Pt/SUS) and roughened by the formation of a surface oxide layer (Pt/Al 2 O 3 /SUS). The nanoscale roughness was comprehensively analysed using electron microscopy, laser scanning confocal microscopy and chemisorption techniques. NH 3 oxidation activity, measured at 200 °C, followed an increasing trend in the order of Pt/Al 2 O 3 /SUS < Pt/SUS < Pt/p-SUS, despite a decrease in the apparent Pt surface area in the same order. Consequently, the calculated TOF was markedly higher for Pt/p-SUS (267 min -1 ) compared to Pt/SUS (107 min -1 ) and Pt/Al 2 O 3 /SUS (≤22 min -1 ). The smooth Pt overlayer surface also favoured N 2 yield over N 2 O at this temperature. This discovery enhances our fundamental understanding of high-TOF NH 3 oxidation over Pt overlayer catalysts, which holds significance for the advancement and industrial implementation of selective NH 3 oxidation processes.

In the present study, we prepared a 12 nm thick Ir overlayer via pulsed cathodic arc plasma deposition on a 50 μm thick Fe-Cr-Al metal (SUS) foil. Using this thin-film catalyst made NH 3 -O 2 reactions more environmentally benign due to a much lower selectivity for undesirable N 2 O (<5%) than that of a Pt overlayer (∼70%) at 225 °C. Despite its small surface area, Ir/SUS exhibited promising activity as an ammonia slip catalyst according to a turnover frequency (TOF) >70-fold greater than that observed with conventional Ir nanoparticle catalysts supported on γ-Al 2 O 3 . We found that the high-TOF NH 3 oxidation was associated with the stability of the metallic Ir surface against oxidation by excess O 2 present in simulated diesel exhaust. Additionally, we found that the Ir overlayer structure was thermally unstable at reaction temperatures ≥400 °C and at which point the Ir surface coverage dropped significantly; however, thermal deterioration was substantially mitigated by inserting a 250 nm thick Zr buffer layer between the Ir overlayer and the SUS foil substrate (Ir/Zr/SUS). Although N 2 O formation was suppressed by NH 3 oxidation over Ir/Zr/SUS, other undesired byproducts (i.e., NO and NO 2 ) were readily converted to N 2 by coupling with a V 2 O 5 -WO 3 /TiO 2 catalyst in a second reactor for selective catalytic reduction by NH 3 . These results demonstrated that this tandem reactor configuration converted NH 3 to N 2 with nearly complete selectivity at a range of 200-600 °C in the presence of excess O 2 (8%) and H 2 O (10%)., Competing Interests: The authors declare no competing financial interest., (© 2020 The Authors. Published by American Chemical Society.)