- 著者
- Tie LI Keiya NISHIDA Yuyin ZHANG Tuyoshi ONOE Hiroyuki HIROYAU
- 出版者
- 社団法人 日本機械学会
- 雑誌
- JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)
- 巻号頁・発行日
- vol.48, no.4, pp.687-694, 2005 (Released:2006-05-15)
- 参考文献数
- 9
- 被引用文献数
- 5 19
The effect of split injection on the mixture characteristics of DISI (Direct Injection Spark Ignition) engines was investigated firstly by the Laser Absorption Scattering (LAS) technique. Through splitting the fuel injection process, two possible benefits were found: 1) High density liquid droplets piling up at the leading edge of the spray can be circumvented, subsequently the reduction of the spray tip penetration; 2) The quantity of “over lean” (φv<0.7, φv: equivalence ratio of vapor) mixture in the spray can be significantly reduced. These are believed to contribute to the reduction of the engine-out smoke and HC emissions. In order to clarify the mechanism behind the effect of the split injection, the spray-induced ambient air motion was investigated by the LIF-PIV technique. The strong ambient air entrainment into the tail region of the spray and a counter-vortex structure were found in both the single and split injections. In the case of the single injection, the spray develops in extending its length, subsequently a larger volume results and thus it is diluted to “over lean” by the ambient air entrainment. In contrast, in the case of split injection, the second spray is injected into the tail region of the first spray and its evaporation is promoted by the ambient air motion induced by the first spray. Hence the replenishment of the liquid fuel into the leading edge of the first spray is reduced. As a consequence, the high density liquid droplets piling up at the leading edge is avoided. Furthermore, a more compact spray results so that the ambient air motion plays a positive role on evaporating the spray into “more combustible” (0.7<φv<1.3). This is especially true in the tail region of the spray and the region where the counter-vortex motion is occurring.
- 著者
- Yuyin ZHANG Keiya NISHIDA Takuo YOSHIZAKI
- 出版者
- 社団法人 日本機械学会
- 雑誌
- JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)
- 巻号頁・発行日
- vol.46, no.1, pp.100-108, 2003 (Released:2004-06-25)
- 参考文献数
- 17
- 被引用文献数
- 2 10
Recent experimental studies have shown that with split injection strategy, the soot and NOx emissions from a diesel engine can be reduced significantly in comparison with a conventional non-split injection. To understand the mechanism of emissions reduction, it is essential to clarify the process of mixture formation in the diesel spray. For characterizing the droplets and vapor concentration distributions inside a fuel spray, a dual-wavelength laser absorption-scattering technique (LAS) was developed by using the 2nd harmonic (532nm) and the 4th harmonic (266nm) of an Nd: YAG laser and using dimethylnaphthalene as a test fuel. By applying the ultraviolet-visible LAS imaging technique, the distributions of droplets and vapor concentrations in the spray, which was injected into a high-temperature and high-pressure nitrogen ambient in a constant volume vessel by a common-rail diesel injection system, were measured and quantitatively analyzed. The effect of injection mass ratio of double-pulse injections on distributions of equivalence ratios of vapor and droplets in the sprays was examined.