Analysis of spray characteristics on a counter-bore fuel injector nozzle for diesel engine application

摘要

In the current paper, an investigation of a counter-bore diesel injector nozzle geometry for on the injector hydraulics and spray formation characteristics is done. Results show that, despite the nozzles were defined at same flow number, higher effective diameter is achieved for the counter-bore nozzle, producing higher maximum injection rate and momentum flux. No negative effect of the counter-bore on the effective outlet velocity has been observed, except for very high injection pressure cases. Tests using multiple injection strategies show that the nozzle outlet conditions are more sensitive to the specific dwell time when using the counter-bore configuration. Liquid and vapor spray visualization tests are performed on a high pressure and high temperature constant pressure vessel, using Mie-scattering and shadowgraphy techniques. Spray penetration is faster for the counter-bore nozzle due to its larger effective diameter, and longer stabilized liquid length values are achieved. Nevertheless, the combination of cumulative injection rate data and spray volume from spray visualization confirms that air entrainment characteristics are more significant for the counter-bore nozzle. This mixing efficiency improvement has been finally assessed in finer details by means of a 1-dimensional spray model. Finally, preliminary engine results show benefit in fuel consumption and soot emissions for this nozzle concept.