Student Theses

The efficiency of fuel cell systems can be drastically increased by using a turbocharger. Operation with humid air as the working fluid leads to a condensing two-phase flow in the turbine. Depending on the operating point, the number and size of the droplets as well as the location of droplet formation vary. While primary droplets mainly lead to a reduction in efficiency, coarse water (secondary) droplets can cause erosion damage to the turbine. 
Optical measuring systems for determining droplet distributions are being developed and used at the ITSM. Current systems can measure small (primary) droplets in the range of 0.1 - 10 µm. As larger (secondary) droplets are also expected, a new laser-based system is currently being developed that can measure droplets from 10 - 500 µm. Calibration is essential for this. 
In this work, an existing calibration system is to be redesigned and optimized for the present application.

Supervisor: Dominik Bezler

Type of work: experimental

The ITSM develops and uses optical measuring systems to determine droplet distributions. These systems are based on the light extinction method, which uses the wavelength-dependent attenuation of light to determine the droplet size and number of droplets. Complex numerical methods are used to evaluate such measurements, which can lead to uncertainties and is associated with high manual effort. 
In this work, a new algorithm for the evaluation of droplet measurements is to be developed at the ITSM. This is to be developed using mathematical surrogate models in MATLAB. Various surrogate models such as Kriging or ANN (artificial neural networks) are to be generated and compared on the basis of their prediction accuracy.

Supervisor: Dominik Bezler

Type of work: theoretical, numerical

Especially for heavy-duty applications (Trucks, short-range aviation, ...), hydrogen fuel cells have gained a lot of attention in recearch. For operation at high efficiencies, the ambient air is compressed upstream of the fuel cell. The compressor is usually one of the main parasitic work consumers in the air management system of hydrogen fuel cell applications. The reduction of compression work through droplet injection and evaporation inside the compressor has been discussed for variuos applications in the literature. This work is focussed on assessing the impact of Inlet Fog Boosting regarding the system efficiency of hydrogen fuel cell applications using 3D CFD.

Betreuer: Adem Tosun

Art der Arbeit: numerisch, theoretisch

Thermodynamic cycles are historically driven by air and/or water vapor. For quite som time CO₂ is duscussed as a superior working fluid, due to advantages in necessary compression work and efficient integration of recuperating cycles. CO₂ is thereby operated in the supercritical regime during the thermodynamic cycle. The complex thermodynamic processes and the potential for condensation at supercritical conditions pose uniqe requirements onto the design of turbomachines for these applications. This work focusses on applying an existing model for calculating condensing flow with CFD on flows with the working fluid CO₂.

Betreuer: Adem Tosun

Art der Arbeit: numerisch, theoretisch

The flow near the stability limit shows unstationary phenomena. The aim of the investigations is to calculate these phenomena using CFD and to compare the results with experimental data.

Supervisors: Maiken Günther, Daniel Nagel

Type: Numerical

The flow profile in the axial compressor test rig is to be determined using a pressure probe. For this purpose, a traversing system is to be constructed and assembled, the control and evaluation of which is to be implemented in LabView. The probe will then be used in test operation. The work can be carried out purely experimentally or extended with numerical components.

Supervisors: Maiken Günther, Daniel Nagel

Type: Experimental, numerical

Turbines for hydrogen fuel cell e-turbos are operated with humid air. For an accurate represantation of the working fluid (air+water vapor) and possible phase transitions, a numerical model is developed for the design of these machines.

Supervisor: Adem Tosun

Type: Numerical

A screen mesh module is used to generate a correct flow profile in a channel of a test rig. Due to the size of the cells, this can not be directly simulated. In scope of the work the approach models will be investigated.

Supervisors: Anastasia Fomina, Manuel Maqueo

Type: Numerical