One of the fundamental topics in the design of new injection systems for Dl Diesel engines is to decrease the soot emissions. A promising approach to minimize soot production are injection nozzles having clustered holes. The basic idea of Cluster Configuration (CC) nozzles is to prevent a fuel rich area in the center of the flame where most of the soot is produced. For this purpose each hole of a conventional nozzle is replaced by two smaller holes, which are sized to yield the same flow rate. The basic strategy of the cluster nozzles is to provide a better primary break up, and therefore a better mixture formation, caused by the smaller nozzle holes, but a comparable penetration length of the vapor phase due to merging of the spray plumes. Within this study, six cluster nozzles with cluster angles from 0° up to 15° are investigated and compared to two nozzles of a conventional design, one with the same flow number as the cluster nozzles and the other one with 50%of this value, according to a single hole of the cluster nozzles. The common rail diesel injector is installed in a combustion vessel, in order to provide nearly quiescent high-pressure and high-temperature conditions. Each injection is investigated using three different measurement techniques quasi-simultaneously
. The liquid and the vapor phase are visualized using the scattered light of a Nd:YAG laser and back-lit schlieren imaging, respectively. Furthermore, the hot reaction zone is visualized using OH* chemiluminescence imaging. OH* occurs during the second stage of the ignition process. The penetration lengths of the liquid and the vapor phase, as well as the lift-off length and the ignition delay, are determined. The influence of the cluster configuration and the cluster angle on the penetration and the subsequent combustion are analyzed and discussed.
One of the fundamental topics in the design of new injection systems for Dl Diesel engines is to decrease the soot emissions. A promising approach to minimize soot production are injection nozzles having clustered holes. The basic idea of Cluster Configuration (CC) nozzles is to prevent a fuel rich area in the center of the flame where most of the soot is produced. For this purpose each hole of a conventional nozzle is replaced by two smaller holes, which are sized to yield the same flow rate. The basic strategy of the cluster nozzles is to provide a better primary break up, and therefore a better mixture formation, caused by the smaller nozzle holes, but a comparable penetration length of the vapor phase due to merging of the spray plumes. Within this study, six cluster nozzles with cluster angles from 0° up to 15° are investigated and compared to two nozzles of a conventional design, one with the same flow number as the cluster nozzles and the other one with 50%of this value, according to a single hole of the cluster nozzles. The common rail diesel injector is installed in a combustion vessel, in order to provide nearly quiescent high-pressure and high-temperature conditions. Each injection is investigated using three different measurement techniques quasi-simultaneously. The liquid and the vapor phase are visualized using the scattered light of a Nd:YAG laser and back-lit schlieren imaging, respectively. Furthermore, the hot reaction zone is visualized using OH* chemiluminescence imaging. OH* occurs during the second stage of the ignition process. The penetration lengths of the liquid and the vapor phase, as well as the lift-off length and the ignition delay, are determined. The influence of the cluster configuration and the cluster angle on the penetration and the subsequent combustion are analyzed and discussed.
