Investigation of the Primary Spray Breakup Close to the Nozzle of a Common - Rail High Pressure Diesel Injection System

Many details of the diesel spray breakup in real technical applications are still quite unknown because of the difficulties in the measurement techniques to obtain data inside the dense spray within the first millimeters downstream the nozzle exit. At the LTT-Erlangen the time-resolved Mie scattering technique in combination with a high resolving long distance-microscope is used to investigate this region. In contrast to previous works published by the LTT, the presented investigations have been carried out using a passenger car common-rail injection system equipped with six different injection nozzles. The aim of the presented investigations is to identify the influence of the nozzles geometry on the primary spray break up. With the taken 2D Mie scattering images many information can be extracted according to this topic, e. g., the development of the microscopic spray angle and local droplet size distributions. Additionally, the velocity vectors at the boundaries of the spray close to the nozzle hole have been determined by using double pulse techniques. If possible, microscopic and macroscopic structures of the spray are compared.