Atomization processes are widely used whenever liquids must be rapidly evaporated, efficiently burned or homogeneously coated. Atomization processes are essential for realization and optimization of manifold technical applications (humidifiers, drying plants, internal combustion engines, turbines, printers, painting systems etc.). During atomization, liquid is entering the ambience through a suitable nozzle at sufficiently high injection pressures and thereby breaks up into a swarm of small ligaments and droplets – so-called sprays. Since spray droplets are characterized by large surface-area-to-volume-ratios while interacting with each other and the surrounding gas, they allow a significant increase of momentum-, heat- and mass-transfer processes.
The complexity and relevance of sprays is considered by a particular research group “Atomization Processes” at the institute WSA. The scientific focus of the group is the analysis of sub-processes and physical mechanisms, which are relevant for development and propagation of sprays. In this context, different complementary macroscopic and microscopic methods are used.
We participate in different industrial and public projects in the field of atomization. In this context, manifold scientific questions are addressed in context of clusters of excellence („EXC 236 TMFB“ und „EXC 2186 The Fuel Science Center“), priority program (SPP1980) or different research grants. We investigate e.g.:
- the influence of fuel properties on the development of engine sprays in context of energy revolution
- the atomization of precursor solutions for systematic control of spray-flame-synthesis of nano-materials or
- the interdependency of stem-cells and atomization in context of regenerative medicine.
In each case the focus of our work is the comprehensive laser-optical characterization of spray processes as there are: nozzle internal flow, primary breakup, spray propagation and evaporation (mixture formation) as well as the spray-wallfilm-interaction. In this context different kinds of nozzles are used: high-pressure atomizers (such as Diesel or GDI nozzles for mixture formation in internal combustion engines) or low-pressure atomizers (for example endoscopic coaxial atomizer in context of intrapulmonary cell therapy).Copyright: WSA
For a comprehensive laser-optical characterization on macroscopic and microscopic level different complementary methods are developed and applied. The underlying test-benches are stationary installed, enabling a continuous advancement of respective measurement techniques. Highlights and unique selling points are:
- the analysis of nozzle-internal and external flow phenomena under technical relevant conditions and for different fuels (liquid, liquefied gas) by using a specialized microscopy test-rig, consisting of:
- a highly resolving high-speed microscopy
- a high-pressure microscopy chamber
- a modular nozzle heating unit for fuel temperature control
- a fuel variable injection system
- and transparent nozzles with 3D internal geometry
- the quantification of temperature fields inside of micro-droplets and sprays using the highly-resolving planar 2-color LIF with MDR-enhanced energy transfer, abbreviated 2D-2c LIF-EET.
- the spatial resolution of concentration- and film-thickness-footprints in context of spray-wallfilm-interaction using a specialized laser-optical system, consisting of
- a high-speed-Fizeau-interferometer,
- a pulsed UV-laser induced Fluorescence-method
- an optically accessible high-pressure-spin-coater.
- the spatial and temporal characterization of droplet size distributions and velocity distributions in engine sprays and technical sprays using
- a fiber-free Phase-Doppler-Anemometry (DPSS Laser based) and
- a high-speed-shadowgraphy method including an in-house image analysis
List of current public funded projects: