As the regulations governing diesel engine emissions have become more stringent, it has become difficult to fulfill these new requirements by only using techniques that improve combustion. Therefore, more effective aftertreatment technology is needed, particularly for particulate matter. Although ceramic diesel particulate filter (DPF) is a leading technology in automobiles, their implementation in marine diesel engines operated with marine diesel oil (A-heavy fuel oil) containing sulfur presents a problem, in terms of soot removal or regeneration. In this study, a pilot-scale experiment is performed to establish a method implementing nonthermal-plasma-induced radicals for DPF regeneration of marine diesel engines. The pressure difference decreases only when plasma is turned on, and DPF regeneration is realized at 320 °C. The amount of ozone required for regeneration is determined under various engine operating conditions, and the basic characteristics of regeneration are elucidated. The plasma energy required for emission control of the entire gas is approximately 5% of the generated power of the marine engine.

Odor control has gained importance for ensuring a comfortable living environment. In this paper, the authors report the experimental results of a study on the detailed characteristics of a laminated film-electrode and a laminated film-electrode packed-bed nonthermal plasma reactor, which are types of dielectric barrier discharge (DBD) reactor used for odor control. These plasma reactors can be potentially used for the decomposition of volatile organic compounds (VOCs) and reduction of NO_x. The reactor is driven by a low-cost 60-Hz neon transformer. Removal efficiencies under various experimental conditions are studied. The complete decomposition of the main odor component, namely, NH₃, is achieved in a dry environment. The retention times are investigated for the complete removal of NH₃ in the case of the film-electrode plasma reactor and the film-electrode packed-bed plasma reactor. The removal efficiency of the former reactor is lower than that of the latter reactor. Mixing another odor component such as CH₃CHO in the gas stream has no significant effect on NH₃ removal efficiency.

An effective NO _x -reduction aftertreatment system for a marine diesel engine that employs combined nonthermal plasma (NTP) and adsorption is investigated. The system can also treat particulate matter (PM) that employs a diesel particulate filter (DPF) and its regeneration by NTP-induced ozone. The effect of the combined reduction of accumulated PM and NO _x is studied. The marine diesel engine of interest provides an output power of 1 MW at 100% of the engine load. The NO _x reduction is composed of repeated adsorption and desorption flow processes using NTP combined with NO _x adsorbents. With a view toward practical use, experiments on a higher number of cycles are carried out. The amount of adsorbents is 105 kg, which is greater than that in the authors’ previous study. As a result, NO _x reduction efficiency by NTP is higher than in the previous study and is greater at higher amounts of adsorbents owing to higher NO _x desorption. Furthermore, DPF regeneration with plasma-induced O ₃ injection is achieved simultaneously. This aftertreatment system demonstrates an excellent energy efficiency of 114 g(NO ₂ )/kWh. The present aftertreatment can generate a synergistic effect of PM and NO _x reduction.

Microfabrication by photolithography and nickel plating of fluoropolymer film, exposed to atmospheric-pressure nonthermal-plasma (NTP) graft polymerization, are investigated. Electroless nickel plating on the NTP-graft-polymerizationtreated polytetrafluoroethylene (PTFE) film is successfully achieved. Highly adhesive nickel plating is obtained by reverse bend test. Furthermore, photolithographic patterns are formed on the plated PTFE film. This process is expected to be applied to flexible printed substrates and millimeter-wave antenna.

An efficient NO_x reduction aftertreatment technology for a marine diesel engine that combines nonthermal plasma (NTP) and NO_x adsorption/desorption is investigated. The aftertreatment technology can also treat particulate matter using a diesel particulate filter and regenerate it via NTP-induced ozone. In this study, the NO_x reduction energy efficiency is investigated. The investigated marine diesel engine generates 1 MW of output power at 100% engine load. NO_x reduction is performed by repeating adsorption/desorption processes with NO_x adsorbents and NO_x reduction using NTP. Considering practical use, experiments are performed for a larger number of cycles compared with our previous study; the amount of adsorbent used is 80 kg. The relationship between the mass of desorbed NO_x and the energy efficiency of NO_x reduction via NTP is established. This aftertreatment has a high reduction efficiency of 71% via NTP and a high energy efficiency of 115 g(NO₂)/kWh for a discharge power of 12.0 kW.