Research projects at ITT
Research Group 1447: Safety Realted Ignition Processes
Combustible mixtures can be ignited by various ignition sources. Within the research group FOR 1447 five important ignition sources shall be examined varying from hot surfaces to hot free jet flows. Concerning typical applications in the field of safety engineering, the ignition process can be influenced by different transport processes, which normally disturb the ignition via heat losses etc. In the case of hot surfaces the autoignition of a combustible mixture is mainly dominated by chemical reactions. The influence of perturbations on the ignition process becomes more and more important considering hot particles, mechanical sparks, electrical discharges or hot free jet flows as ignition sources. Additionally, various transport processes like molecular transport, laminar flow, and turbulent flow have to be considered. The ignition delay times of the combustible mixtures have to be reduced to compensate the losses, and sufficient energy has to be delivered from the ignition sources.
Modelling, Simulation and Compensation of Thermal Effects for Complex Machining Processes
In almost all machining processes, the components, which are to be manufactured, are to a large extent thermally affected. The thermal energy, which results in these processes mainly from shearing, friction, and cutting energy, is dispersed to the workpiece, the chip, the cutting tool, and the cooling lubricant. At the same time, the lubrication effect also reduces the frictional heat. In dry machining and minimum quantity lubrication, the cooling aspect does not exist and the lubrication is at least reduced. Transient thermal fields, generated during the manufacturing process, and the heat, accumulating in the workpiece, cause a considerable impairment of the finished part with regard to tolerance compliance. Numerous dry processes or processes with minimum quantity lubrication induce a complex thermal load spectrum, which leads to thermally caused form deviations in the finished component and changes its behavior in future use. Due to lack of fundamental knowledge, these influences can at the moment only be avoided by conducting extensive run-in experiments.
Decomposition kinetics of organic fluorescent tracer under combustion engine conditions: modeling
Many species such as NO, CO, C 2 H, CH, CH 2 O or OH that occur as products or as intermediate species during or after a combustion processes can be visualized by laser-induced fluorescence. In engine diagnostics methods for determining local fuel concentrations and temperature fields are of great interested. This can be achieved by adding a fluorescing species (so-called tracer) to the fuel as an additional component. Task of the tracer is to visualize the fuel distribution using laser light. At the Institute of Technical Thermodynamics (ITT) numerical studies of tracer/fuel/air mixtures are performed under conditions relevant in IC engines. For the modeling reliable reaction mechanisms are needed.
Flame acceleration in vortex tubes by combustion-induced vortex bursting
The objective of this project is the investigation of combustion-induced vortex bursting in its various manifestations and its modelling at different levels of detail. It will be attempted, in particular, to elucidate the coupling of the interaction between the chemical reaction and the vortex dynamics with the feedback of the vortex dynamics via the turbulence to the chemical conversion rate, which so far has been understood only in outline, and make it amenable to efficient computation.
Controlled self-ignition - HCCI
The goal in the development of modern internal combustion engines must be to decrease emissions and fuel consumption, without thereby reducing performance. This makes a detailed understanding of the processes taking place in the internal combustion engine's combustion chamber indispensable. Optical methods such as laser-induced fluorescence (LIF) offer new options for investigating these processes directly in the combustion chamber. Together with advanced numerical methods, this provides engine diagnostics that can help to develop more efficient and lower-emission engine. One promising combustion process is the self-ignition of homogeneous fuel-air mixtures (HCCI), which will be investigated here in more detail.
Modern internal combustion engines, as are used in vehicles, should exhibit high efficiency and low weight. Therefore, the trend is towards ever smaller units with very high specific power. This leads to ever higher gas pressures and temperatures in the cylinder; increasingly frequently nowadays, further engine improvement is limited by so-called pre-ignition.
Experimental investigation of turbulent reactive multiphase flows
Combustion processes of defined droplet chains in a natural gas envelope flame or spray flames are investigated with the help of modern laser optical methods. The results of these experiments can be compared with computer simulations that model the vaporisation, mixing and combustion process.
Even in the combustion of small hydrocarbons, the chemical kinetics have very extensive underlying reaction mechanisms. Thus for example, the reaction mechanism for the combustion of methane consists of 34 different chemical species, which react with each other in 302 elementary reactions. If one considers the combustion of complex hydrocarbons, the number of chemical species can increase to several hundreds, that of elementary reactions to several thousands. Accurate knowledge of these detailed reaction mechanisms is of great importance for a correct description of kinetically controlled processes such as pollutant formation, ignition and flame extinction.