(3-06) Smokeless and Low NOx Combustion in a Dual-Fuel Diesel Engine with Induced Natural Gas as the Main Fuel((AF-2)Alternative Fuels 2-Gas Engines)

概要

論文の詳細を見る
In a compression ignition engine, using a rich and lean biform mixture composition that avoids near stoichiometric and extremely over-rich regions would be effective to suppress NOx formation without increasing smoke when the overall excess air ratio approaches the stoichiometric ratio. To realize the formation of rich and lean mixtures and the control of ignition timing, a dual-fuel diesel engine with an induced gas with resistance to self-ignition as the main fuel and with a small quantity of diesel fuel for the ignition source has potential merits. However, this method has the problem of knocking and misfiring when the percentage of inducted fuel is increased. In this research smokeless and ultra low NOx combustion without knocking over a wide operating range was established in a dual-fuel diesel engine with induced natural gas as the main fuel. Optimizations of the combustion chamber shape and operating factors, including EGR and intake air throttling, which determine conditions of the in-cylinder gas, were investigated at several IMEP conditions. A lean quasi-homogenous mixture was formed with induced natural gas in the whole combustion chamber while a small quantity of diesel fuel was directly injected for an ignition source, as shown in figure 1. The injection timing of the diesel fuel was set at a relatively early stage in the compression stroke to avoid smoke emissions. A piston cavity divided by a lip in the sidewall, shown in the figure, was suitable to confine diesel fuel into the lower part of the cavity, and this suppressed knocking just after ignition. It was also expected that a slightly richer than stoichiometric mixture is formed in the lower part of the cavity, and a leaner mixture is formed in the upper part of the cavity. This mixture formation process was analyzed with a CFD simulation, which showed the possibility for biform mixtures without near stoichiometric or extremely over-rich regions in the chamber. The results of the experiments showed that a combination of the divided cavity, EGR, and intake air throttling was effective to simultaneously eliminate knocking and reduce THC and NOx over a wide IMEP range. At high IMEP silent and smooth combustion without knocking was achieved even with a large amount of induced natural gas. Moreover, the maximum IMEP increased in comparison with conventional diesel operation with a lower injection pressure system because smoke emission was not a limitation. At medium IMEP it was effective to adopt EGR and intake air throttling for ultra low NOx under relatively lower THC. However, at low IMEP it was difficult to avoid increases in THC and ISEC while realizing ultra low NOx and smokeless operation. At lower overall excess air ratio conditions, NOx reduction was shown with a biform mixture composition without near stoichiometric or extremely rich regions.
一般社団法人日本機械学会の論文
2001-07-01

(3-06) Smokeless and Low NOx Combustion in a Dual-Fuel Diesel Engine with Induced Natural Gas as the Main Fuel((AF-2)Alternative Fuels 2-Gas Engines)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク