Atomization processes

 

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.

 

Current Projects

We participate in different industrial and public projects in the field of atomization. In this context, manifold scientific questions are addressed as 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.

• DFG RE 4092/2-1: Development of an intrapulmonary spray method for cell therapy
• DFG SPP1980: Impact of atomization on particle synthesis in spray flames
• DFG KN 764/17-1: Experimental and numerical analysis of the interaction of sprays with thin wallfilms
• DFG ZUK II, RWTH Start-Up 333-18: Influence of pressure and velocity gradients during atomization on deformation and viability of mesenchymal stem cells
• DFG EXC 2186-FSC: Fundamental investigation of spray and droplet interaction phenomena in advanced combustion systems
• DFG EXC 2186-FSC: Fuel-adapted manipulation of nozzle-internal and external breakup mechanisms for molecularly-controlled mixture formation
• DFG EXC 2186-FSC: Local analysis and evaluation of innovative fuel-adaptive exhaust-gas abatement and aftertreatment strategies
• BMWi ZIM PPA-Profil PDA: Development of a line phase Doppler Anemometer for simultaneous measurement of position, size and velocity of droplets or particles

 

Completed Projects

• DFG EXC 236 TMFB
• ERS Seed Fund OPSF365 - CellSpray: Spray Application for Cell Therapy inside hollow organs
• Research Cluster Fuel in Oil: Fundamental research of spray-oil film interaction
• DFG SFB 686 Model-Based Control of Homogenized Low-Temperature Combustion

 

Methods

Copyright: WSA

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).

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