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Recently, environmental problems come to be taken prosperously, and the reduction of environmental effects is demanded in an automobile section. The alternative fuels for diesel engines have been also developed for emission regulations. In this study, the authors proposed and estimated the validity of the hybrid system, which combines a dimethyl ether (DME) diesel engine and a DME fuel cell for commercial vehicles such as buses and tracks. DME is adopted as the both fuels for good environment and high efficiency of the system. DME has received a lot of attention recently as a possible alternative to diesel engines for a little environmental effects and stable distribution. It has the same cetane number as that of diesel fuel and emits no smoke from diesel engines. The conventional LPG stations are possible to provide DME because of the same handling as LPG.

Hydrogen has difficulties in handling in a fuel cell vehicle, and has a fault with taking a big space there. The authors have proposed a hydrogen generation system using ammonia as a liquid fuel for fuel-cell electric vehicles. Ammonia has an advantage not to emit greenhouse effect gases because it does not contain a carbon atom. Hydrogen content of ammonia is 17.6 wt% and hydrogen quantity per unit mass is large. Ammonia can be easily dissociated to hydrogen and nitrogen by heating. Therefore, ammonia is an attractive hydrogen supply source for fuel cell vehicles. The ammonia hydrogen generation system of this study consists of a vaporizer, a heat exchanger and a cracking reactor with a separator. Ammonia is heated with the heat exchanger and sent to the cracking reactor, after it is evaporated through the vaporizer from the liquid ammonia. The ammonia is cracked to hydrogen and nitrogen with an appropriate catalyst.

Fuel without carbon is essential effective in preventing global warming by carbon dioxide. Hydrogen has no carbon and can be made also from the resources such as nuclear energy or renewable energies. However hydrogen is lack of portability for automobiles because of its difficulty in liquefying. Ammonia also has an advantage in terms of global warming because of carbon-free fuel. A hydrogen generation system fueled with ammonia from urea for a fuel-cell electric vehicle is described in this paper. In ammonia, the handling must be careful of safety specifically because toxicity of ammonia affects a human body and a fuel cell. On the other hand, urea can be easily changed into ammonia and dealt with safety. The license for handling of urea is unnecessary, and there are also achievements as a NOx reducing agent for diesel engines. The authors have proposed urea as a hydrogen carrier via ammonia.

Clean fuels that emit no greenhouse effect gas are requested in various fields especially of the global warming issue. The authors have proposed a hydrogen generation system using ammonia as a liquid fuel for fuel cells. The system consists of a cracking reactor, a heat exchanger and an ammonia separator to remove residual ammonia. It have been clarified that ammonia by 13 ppm or more causes an output decrease in polymer electrolyte fuel cells. In this study, the cracking efficiencies of ammonia were investigated with two kinds of and two shapes of catalysts to review the optimum conditions of the system. The conditions were decided by analyzing hydrogen concentration and residual ammonia concentration for some cracking temperatures and space velocities. At the cracking temperature of 500°C, the cracking efficiency of Ru/Al2O3 catalyst has shown sufficient results.

Dimethyl ether (DME) has received a lot of attention recently as a possible alternative to diesel engines for little environmental effects and stable distribution. DME can be made from various resources in large quantities and easily transported. It has the same cetane number as that of diesel fuel and emits no smoke from diesel engines. Moreover it is also expected to be a fuel for fuel cells because much hydrogen can be obtained by steam reforming. This paper focuses on a hybrid power system for commercial vehicles with a diesel engine and a fuel cell fueled with DME as a single fuel. The system obtains a driving power by diesel engines with DME combustion and at the same time generates electricity by a fuel cell with hydrogen generated from DME reforming. The electric power can be supplied to a refrigerator or batteries. The total energy loss will be less in DME reforming by recovering the exhaust heat from the engine.

In this paper, the authors have described a fuel-cell electric vehicle for trial purposes with the hydrogen generation system fueled with ammonia for compact vehicles. The system consists of a dissociator with Ruthenium/Alumina catalyst, a heat exchanger and an ammonia separator to remove residual ammonia. The dissociation system compactly unifies the heat exchanger and the dissociator to effectively rise the temperature of the system by installing some alumina balls just before catalyst. Therefore the system can be small in size enough to be installed on-board in the vehicle. The cruising time is about 160 minutes in the system. If the concentration of residual ammonia in the dissociated gas becomes 13 ppm or more, the residual ammonia will poison the proton exchange membrane (electrolyte) of the fuel cell, and cause the fuel cell to decrease the output.

Ammonia has a potential as a liquid fuel for fuel cell vehicles, because it can be easily liquefied at a lower pressure and theoretically dissociated to the mixture of high-content hydrogen and nitrogen. Ammonia also has an advantage in terms of global warming because of carbon-free fuel. A fuel cell vehicle system with an ammonia onboard dissociator is proposed in this paper. The effects of temperature, pressure, and space velocity on concentrations of hydrogen and residual ammonia are investigated in the experiment. The residual ammonia separator, necessary even in the optimal condition obtained in the experiment, is designed and prepared. It is demonstrated that the fuel cell vehicle with the ammonia onboard dissociator has the potential as a new concept future vehicle.

Unreacted fuel in ring crevice volumes is a significant source of hydrocarbon emissions from spark ignition engines. If the ring crevice is designed with a wider clearance into which the flame will propagate, the unreacted fuel can be reduced. In this paper, the conditions of flame propagation into the ring crevice are investigated by using ionization probes imbedded in the moving piston of a four-stroke spark ignition engine. It is found that the flame propagates into the ring crevice if the quenching distance when the flame reaches the crevice is narrower than the piston top land clearance.

A dual fueled diesel engine system with diesel fuel and reformed methanol has been investigated. Methanol can be reformed to reformed methanol (hydrogen 67% + carbon monoxide 33%) over suitable catalyst. The reformed methanol contains 20% more energy than methanol. Fundamental data of an electric heated reformer, performance of the dual fueled diesel engine to which hydrogen and carbon monoxide fed from gas bombs as a preliminary experiment, and then performance of the diesel engine with an onboard reformer were tested. In consequence, the feed of the reformed methanol improves the diesel engine performance.