Innovative solutions for reducing particulate emissions will be necessary in order to comply with the even more stringent exhaust-gas standards of the future.
The potential of a diesel nozzle with variable orifice geometry has long been common knowledge in the area of engine construction. But up to now, a fully functional solution of such a nozzle has not appeared which operates with a reduced orifice at low engine speeds and/or low loads. Here with regard to target costing, the requirements implicit in function and manufacture must also be taken into account.
Using calculations on nozzle interior flow and injection-spray investigations, it will be shown which nozzle geometries best fulfill the various requirements. In order to achieve low levels of particulate emission in an engine with a combustion chamber designed for optimum use of a hole-type nozzle, the injection-spray direction and its geometry must to a large extent correspond to those of a hole-type nozzle. This is decisive for the two-phase nozzle (VRD) to make full use of its potential in a conventional combustion chamber.
The two-phase nozzle with spray orifices arranged directly above one another provides the solution to this problem.
The spray geometry for the variable-orifice nozzle has been realised. The application of the needle control for the FTP75 test procedure is being worked on.