窪山 達也

<div class="section abstract"><div class="htmlview paragraph">The previously developed capacitance sensor for detecting a liquid fuel film was modified to apply to the in-cylinder measurement. On the developed sensor surface, comb-shaped electrodes were circularly aligned. The capacitance between the electrodes varies with the liquid fuel film adhering. The capacitance variation between the electrodes on the sensor surface was converted to the frequency variation of the oscillation circuit. In the previous study, it was revealed that the frequency of the oscillation circuit varies with the variation of the liquid fuel coverage area on the sensor surface. The developed sensor was installed in the combustion chamber of the rapid compression and expansion machine, and the performance of the developed sensor was examined. Iso-octane was used as a test fuel to explore the sensor that had been developed. As a result, the adherence of the liquid fuel directly injected into the cylinder was successfully detected under the quiescent and motoring conditions without a combustion event. The frequency decreases with the increase in the duration and amount of fuel injection. The frequency variation was saturated for more than 4 ms injection duration. With the combustion event, the frequency varied during combustion duration even without fuel injection and fuel adhering—the cause of the variation during combustion. The liquid fuel adhering before the combustion event can be detected. The sensor can be applied to the fuel film measurement during cold start and warm-up conditions.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Pre-chamber combustion is well known for the effective way to improve thermal efficiency in internal combustion engine. An active pre-chamber can accomplish super lean burn while a passive pre-chamber can easily improve combustion with low-cost. Therefore, various studies have been carried out. However, since its combustion characteristics are very complicated, the sequence of events for torch ignition and flame propagation in main-chamber from ignition and flame propagation inside pre-chamber have not been well clarified. Especially, investigation on the process from torch ejection to ignition of mixture in main-chamber has been carried out using combustion vessels and rapid compression machines, but this phenomenon has not been clarified.</div><div class="htmlview paragraph">In this study, three types of optically accessible passive pre-chamber with different orifice patterns (normal six orifices, asymmetric five orifices and tangential five orifices) were designed and installed to a single-cylinder gasoline spark ignition engine. Also, an optical-scope was designed uniquely and installed to main-chamber. The flame propagation inside pre- and main-chambers was taken simultaneously by using two high speed cameras. In addition, the temperature distribution around the torch ejection in main-chamber was taken by high speed IR (Infrared) camera. As a result, cyclic variation in flame propagation direction inside pre-chamber and variation in timing of torch ejection in main-chamber were observed. In the cycles when torch ejected to the intake side first, the flame propagation was shifted to the same side inside pre-chamber. This variation of flame propagation direction changed by the orifice pattern of pre-chamber, the flame propagation direction of pre-chamber with tangential orifices were the most stable inside both pre-chamber and main-chamber. Visualizing the temperature distribution during torch ejection showed that the mixture in main-chamber was ignited locally around the torch.</div></div>

<div class="section abstract"><div class="htmlview paragraph">It is becoming increasingly clear that research into alternative fuels, including drop-in fuels, is essential for the continued survival of the internal combustion engine. In this study, the authors have evaluated olefinic and oxygenated fuels as drop-in fuels using a single-cylinder engine and considering fuel characteristic parameters. The authors have assessed thermal efficiency by adding the EGR amount from 0 to the maximum value that allows stable combustion at the theoretical air-fuel ratio. Next, we attempted to predict fuel efficiency for three types of passenger cars (Japanese small K-car N/A, K-car T/C, and Series-HV) by changing the fuels. We created a model in OpenModelica to estimate fuel efficiency during WLTC driving. The results indicated that fuel economy could potentially be improved by adding an olefin fuel that burns stably even with a large amount of EGR and an oxygen fuel whose octane number increases. It was observed that the fuel economy improvement rate was particularly notable for Series-Hybrid Vehicle (HV) with operating under specific load and engine speed conditions.</div></div>