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In order to utilize bio-alcohols as the fuel for diesel engines, combustion characteristics of alcohol blended with gas oil were compared between ethanol and n-butanol in a direct injection diesel engine. In the case of the same cetane number between ethanol and butanol blends, the time-history of combustion, in other words, the ignition delay, the diffusion combustion and the combustion duration, coincided almost completely in both blend fuels. However, the smoke density of the butanol blend was smaller than that of the ethanol blend. This result must be caused by difference in soot formation process between ethanol and butanol blends. Thus, it is difficult to predict the trend of the soot emission in combustion of alcohol blends only by using the existing phenomenological model of the soot formation in the combustion of gas oil.

A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel sprays. The L2F has a micro-scale probe which consists of two foci. The focal diameter is about 3 μm, and the distance between two foci is 18 μm. The data acquisition rate of the L2F was increased to 15 MHz in order to capture every droplet appearing in the measurement volume. Diesel fuel was injected intermittently into the atmosphere using a 5-hole injector nozzle. The diameter of the nozzle orifice was 0.113 mm. The injection pressure was set at 80 and 120 MPa by using a common rail system and the ambient pressure was varied from 0.1 to 3 MPa. The period of injector solenoid energizing was set at 3.0 ms. Droplets were evaluated in a period of 0.2 ms just after the spray tip passed the measurement position. Measurement positions were located at 6, 9 and 12 mm from the nozzle exit. The effect of ambient pressure on the droplet velocity in the near-nozzle region was unremarkable.

A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel sprays. The L2F has a micro-scale probe which consists of two foci. Diesel fuel was injected intermittently into the atmosphere by using a 6-hole injector nozzle. The diameter of the nozzle orifice was 0.135mm. The injection pressure was set at 80MPa. Measurement positions were located at 5, 7, 10 and 15mm from the nozzle exit. The measurement result showed that the velocity of droplets at the spray center was the highest, and decreased in the direction towards the spray periphery. The size of droplets at the spray periphery was larger than the one at the spray center. The size of droplets decreased in the direction of droplet flight on the near nozzle plane. It is understood that the breakup of droplets occurred. The size of droplets increased in the direction of droplet flight at the spray periphery on downstream planes. It is understood that the coalescence of droplets occurred.

A laser 2-focus velocimeter(L2F) has been utilized for the measurements of the velocity and size of droplets in diesel fuel sprays injected from a 6-hole nozzle. The fuel was stored once in a common rail and was injected intermittently to the atmosphere by using a solenoid injector. The diameter of the nozzle orifice was 0.165 mm. The injection pressure was 60 MPa. The injector solenoid was driven by the current having a waveform consisted of 3 stages; boot, pull, and hold. The injection amounts were set at 0.8, 2.9, 3.9 and 4.7mg by changing the durations of the pull stage and the hold stage. The L2F measurement was conducted at 10 mm downstream from the nozzle exit. The fluctuation intensity of the droplet velocity was found to be larger under the smaller injection amount. It was clearly shown that the arithmetic mean droplet size under the smaller injection amount was smaller than that under the larger injection amount during the hold current duration.

A 2-D phase doppler technique was used for the measurements of the velocity, size, and flight direction of droplets in diesel sprays. The data acquisition rate of the phase doppler system was 250 kHz. Diesel fuel sprays injected intermittently into the atmosphere were investigated. The injector orifice was 0.113 mm in diameter. The rail pressure was set at 40 MPa by using a common rail system. The injection period was 3.0 ms and the time interval between injections was 330 ms. Measurement position was located at 40 mm from the nozzle exit for free sprays. In order to evaluate velocity vectors of each droplet, velocity components with angles plus and minus 45 degrees to the spray axis were measured. The data measured at each position was 10,000 and was accumulated over about 1,000 injections. It was found that most droplets near the spray center had velocity vectors along the spray axis.