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This research investigates engine performance and the possibility of reducing exhaust emissions by using Dimethyl Ether (DME). There are high expectations for DME as a new alternative fuel for diesel engines for heavy-duty vehicles. In this experiment, a single cylinder direct-injection diesel engine with displacement of 1.05 liter and a compression ratio of 18:1 was used as a base engine. Common rail type DME fuel injection equipment for the single cylinder engine experiment was installed, and direct injection in the cylinder of DME was tried. Results indicated that high injection pressure, high swirl ratio, and supercharging using multi-hole injectors are effective for combustion promotion in the DME fueled diesel engine (DME engine). The output of the DME engine using supercharging with an intercooler and EGR was higher than that of a diesel engine. By increasing the EGR rate Nox emission was reduced to about 1/3 that of the diesel engine. Smoke was not completely emitted.

In this study, we investigated the combustion technology for the direct injection (DI) methanol engine for a heavy-duty vehicle that makes use of the fuel characteristics of methanol and achieves smokeless burning with high efficiency and low NOx emissions under the heavy load condition. A 3.3-liter 4-cylinder spark-assisted DI methanol engine was tested to investigate the combustion and NOx emission characteristics under the full load condition with supercharging and/or EGR. We believe that supercharging suppressed the stratified charge combustion, but accelerated the premixed combustion to increase the indicated mean effective pressure. Moreover, supercharging was helpful in carrying out EGR under the full load condition without deteriorating the thermal efficiency. Furthermore, heavy EGR during supercharging reduced the NOx emissions dramatically while maintaining the high thermal efficiency and controlling the unburned hydrocarbons emissions.

NOx selective reducing catalysts are expected to be used for lean-burn gasoline engines and diesel engines as an effective NOx reduction measure. We are interested in the combination of methanol, as a reducing agent, and alumina catalyst, and have considered the NOx reduction method using effectively much unburned methanol. In this report, in order to investigate the effect of NOx reduction by the alumina catalyst, the experiment was carried out by feeding the actual exhaust gas from the methanol engine into the alumina catalyst. As a result, it was confirmed that, without addition of any other reducing agents into the exhaust gas, the alumina catalyst has activity to reduce NOx.

It is well known that during engine cold-start, methanol fueled vehicles have a tendency to emit significant amount of unburnt methanol and formaldehyde, which is an oxidant of methanol The emission behavior and reduction methods of these components are studied in this paper The reduction rate of these unburnt components exceeds 99% when the temperature of a catalyst is enough high However during engine cold-start the oxidative reaction can not begin, and it takes several minutes to warm up the catalyst After the temperature of the catalyst reaches to the light-off temperature it rises steeply and high reduction rates of these components are obtained at the same time Therefore, the catalyst temperature must be raised quickly and effectively in order to realize the proper oxidative reduction of unburnt methanol and formaldehyde emissions during engine cold-start Consequently the effectiveness of installing pre-catalysts was examined in this study Some pre-catalysts (200cm3/piece) were placed after the exhaust manifold Results showed that within 10 minutes of initiating the idling experiment after engine cold-start the pre-catalysts were very effective and decreased emissions of the unburnt components by two thirds Moreover pre-catalysts which were electrically pre-heated with an external heater could more drastically decrease the amount of these components under the same experimental conditions However for such electrical heating to be practical it is necessary to reduce the level of heating energy to as low an amount as possible Therefore two power-saving methods were tried One method consisted of installing a glow plug in the upper stream of the pre-catalyst This method was based on an idea that unburnt components coming in contact with the glow plug are activated and easily oxidized and that they then release thermal energy for quick heating The results showed that this method was effective for reduction (more than 40%) of unburnt methanol but was ineffective for reducing formaldehyde since spot heating caused a balancing of formaldehyde formation/decomposition Therefore another method was examined A small-sized electric heated pre-catalyst(50cm3)was installed in order to heat a full section of the exhaust stream of the catalyst The results showed that this method had a great effect in reducing these harmful substances Moreover, it was demonstrated that this method consumes little energy and is more practical as a means of heating

Exhaust gas recirculation (EGR) was applied in a spark-assisted, direct-injection (Dl) neat methanol engine for light duty vehicles. An experimental study has been carried out to analyse for major factors of EGR that influence in the reduction of NOx mass emission and improvement in brake thermal efficiency. EGR on the Dl methanol engine alters intake charge, especially increasing the concentrations of H2O and unburned methanol with rising intake charge temperature. The results of qualitative analyses show that this phenomenon suppresses rapid heat generation at the initial combustion stage, therefore lowering the combustion temperature in the cylinders and leading to a reduction in NOx production.