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

对于以机动性为基础的社会，内燃机将继续具有重要意义，特别是对于中长距离交通以及商用车辆。在这种情况下，关于燃料喷射的技术知识具有重要意义，因为在此确定随后燃烧和污染物形成的初始条件。这一点在关注二氧化碳的潜在节省、燃油经济性和排放限值下降时尤其如此。该研究项目涉及方法的开发和应用，其中还包括对喷射器内部和喷嘴附近的瞬态和动态流动过程的研究。这不仅在技术上而且在科学上都极具挑战性，因为它包括亚毫米范围内的现代注射器的尺寸（喷射孔直径100-200微米），柴油喷射器的喷射压力从2000巴和更高，多相过程，例如，在针座和喷嘴的喷射端口中的气穴现象和高度瞬态效应，近年来，ITV-Hanover的高时间和空间分辨率测量技术取得了很大的进展。本研究计划旨在以实验方式研究柴油机喷油器内的过程，以收集和提供可靠的测量数据，用于数值模拟。该项目包括3/4的实验和1/4的数值工作，因为经验表明，实验工作和计算方法之间的密切联系是必要的。此外，还为其他研究机构提供了选定的喷嘴，以便在国际“发动机燃烧网络”（ECN）倡议的框架内进行合作调查。此外，测量结果也将被公布，以便其他工作组可以将其用于模型开发和验证。改进透明注射器的生产，接近真实的几何形状。透明丙烯酸玻璃喷嘴的强度必须在真实的几何形状中得到增强，以研究在限定的边界条件下超过800 bar的非常高的注射压力。2.可调喷针透明喷嘴影响因素的实验研究。测量两相过程的物理模型，特别是关于空化过程。3.应提供选定的喷嘴几何形状和CFD模型开发的测量数据，例如在ECN网络中。4.用CFD模拟喷油器中的瞬态流动过程，并验证高压范围内多相流和空化的当前CFD模型。

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.