Laseroptische Untersuchungen von düseninternen Phänomenen und deren Auswirkung auf den Primärzerfall von Hochdruckzerstäubern
- Laser optical investigations of nozzle internal phenomena and their impact on primary breakup of high pressure atomizers
Kirsch, Valeri; Kneer, Reinhold (Thesis advisor); Pitsch, Heinz (Thesis advisor)
Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis
Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021
The focus of this thesis lies on the investigation of the relevant breakup mechanisms for the primary breakup of high-pressure atomizers. For this purpose, a transmitted light microscope in combination with a microscopy chamber is developed in order to visualize the primary breakup directly at the nozzle outlet under engine-relevant ambient densities. Based on these developments, the LCV velocity measurement system introduced by Chaveset al. (1993) is implemented, adjusted and calibrated close to the nozzle at overpressure conditions. First measurements of the primary breakup at injection pressures of up to 100 MPa and ambient pressures of up to 0,80 MPa show that the exclusive investigation of the primary breakup without knowledge of the nozzle’s internal flow gives only an insufficient understanding of the underlying physics. For this reason, a new transparent nozzle design is being developed and successfully established in first measurements. The transparent nozzle is produced with an innovative manufacturing process (Selective Laser-induced Etching) and glued to an original nozzle body. This method allows the realization of the transparent nozzle with realisticgeometrical parameters such as e.g. nozzle inlet rounding, k-factor, conical nozzle hole in unknown accuracy of up to 1 µm. Therefore, simultaneous visualization of the inner and outer phenomena is given with that nozzle. Based on the microscopy technique, injection chamber, LCV measurement method, the glass nozzle and additional measuring methods, local and global effects and their significance for flow development and primary breakupunder engine-relevant ambient densities are analyzed in detail.