Search Results

Measurements of temporal and spatial changes in the velocity and size of droplets of diesel fuel sprays under two injection pressures were conducted near the nozzle orifice by a laser 2-focus velocimeter (L2F). The result showed that the size of droplets under higher rail pressure was larger than that under lower rail pressure at the spray center and was smaller than that under lower rail pressure at the spray periphery. It was found that the size of droplets deceased in the downstream direction of the spray and the decrease rate increased with the rail pressure. The cross-sectional average velocity increased and the cross-sectional average size decreased with the rail pressure in the spray near the nozzle exit.

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.

In order to realize a premixed compression ignition (PCI) engine by utilization of bio-alcohol, combustion characteristics of bio-alcohol blended with gas oil were compared between ethanol and n-butanol in a diesel engine. The effects of the ethanol blend ratio and the butanol blend ratio on ignition delay, premixed combustion, diffusion combustion, fuel consumption and exhaust emissions such as smoke density and NOx were investigated experimentally. It is found that ethanol almost burns out together with combustion of low evaporation temperature composition of gas oil in the premixed combustion period and the heat release in the diffusion combustion is based on mainly high evaporation temperature composition of gas oil, then, soot is formed in the diffusion combustion of gas oil. On the other hand, a part of butanol burns in the diffusion combustion, however, the combustion of butanol in the diffusion stage is not the cause of soot formation.

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) has been applied for the measurements of velocity and size of droplets in the core region of diesel spray. The L2F had a micro–scale probe which consists of two foci. The distance between two foci was 14 µm and the focus size was nominally 3 µm. Valid data were extracted by the criteria that a downstream signal was sequentially observed after an upstream signal. The maximum data sampling rate of the L2F was set at 15 MHz. Fuel was intermittently injected into the atmosphere by using a common rail injector. The nozzle orifice diameter of the injector was 0.113 mm and the injection pressure was set at 70 MPa. Five measurement positions were located in the plane of 15 mm from the nozzle orifice. The L2F could detect droplets just after the spray tip reached the measurement position. Measurement result showed that the velocity and size of droplets in the spray core decreased at the off–axis region.

A laser 2-focus velocimeter (L2F) has been applied for the measurements of velocity and size of droplets in the core region of diesel spray. The L2F had a micro-scale probe which consists of two foci. The distance between two foci was 14 μm and the focus size was nominally 3 μm. Valid data were extracted by the criteria that a downstream signal was sequentially observed after an upstream signal. The maximum data sampling rate of the L2F was set at 15 MHz. Fuel was intermittently injected into the atmosphere by using a common rail injector. The nozzle orifice diameter of the injector was 0.113 mm and the injection pressure was set at 70 MPa. Five measurement positions were located in the plane of 15 mm from the nozzle orifice. The L2F could detect droplets just after the spray tip reached the measurement position. Measurement result showed that the velocity and size of droplets in the spray core decreased at the off-axis region.

In order to get fundamental information about the droplet disintegration in the core region of diesel fuel spray, an advanced laser 2-focus velocimeter (L2F) was used for the measurements of velocity and size of droplets. The L2F with micro-scale probe has high optical SN ratio and high spatial resolution. Measured was the fuel spray injected into the atmosphere intermittently from a single hole nozzle. The diameter of the orifice was 0.2 mm. Measurements were conducted on four planes where the axial distances were 10, 20, 30, and 40 mm respectively downstream from the orifice exit. As the injection pressure and needle valve lift change unsteadily in case of the intermittent injection spray, time change of spatial distributions of velocity and size was measured and time change of the joint probability density associated with velocity and size was examined.