Investigation of multiphase flow and cavitation processes in transparent injection nozzles under highest pressure condition

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For the mobility-based society the internal combustion engine will continue to be of major importance, particularly with regard to medium and long distance traffic as well as commercially used vehicles. In this context the technical knowledge about the fuel injection is of significant relevance, since the initial conditions for the subsequent combustion and pollutant formation are determined here. This is especially true with the focus on the potential savings of CO2, fuel economy and declining emission limits. This research project involves the development and application of methods, which also include the investigation of transient and dynamic flow processes inside the injector and in close proximity to the nozzle. This is not only technologically but also scientifically extremely challenging, as it includes dimensions of modern injectors in the sub-millimeter range (spray hole diameter 100-200 microns), the injection pressure of diesel injectors from with 2000 bar and more, multi-phase processes, for example, with cavitation in the needle seat and the injection port of the nozzle and highly transient effects, whose influence becomes increasingly dominant in terms of multi injections.In recent years great progress could be achieved by means of high temporal and spatial resolution measurement techniques at the ITV-Hanover. This research project is proposed to experimentally examine the processes in diesel injectors in order to collect and provide reliable measurement data for numerical modelling. The project consists of 3/4 experimental and 1/4 numerical work, because experience has shown that a close connection between experimental work and calculation methods is necessary. Furthermore, selected nozzles are provided for other research institutions for a collaborative survey within the framework of the international "Engine Combustion Network" (ECN) initiative. Also the achieved measurement results will be published so that other working groups can use them for the purpose of model development and validation.The following questions and objectives are pursued:1. Improved production of transparent injectors being close to realistic geometries. The strength of the transparent acrylic glass nozzles must be enhanced in real geometries for the investigation of very high injection pressures above 800 bar with defined boundary conditions.2. Experimental investigations of influence factors on transparent injector nozzles with defined and adjustable nozzle needle. Measurement for physical modelling of two-phase processes, especially with regard to the cavitation processes.3. Selected nozzle geometries with measured data for the CFD model development shall be provided, for example within the ECN network.4. Modelling of transient flow processes in injectors with CFD and verification of current CFD models of multiphase flow and cavitation in the high pressure range.