Alain Strzelecki

Experimental and Numerical Studies of Dilution Systems for Low-Emission Combustors

Numerical and experimental investigations of eight isothermal jets in crossflow (eight-JICF) issuing radially in a round pipe are presented to assess advanced numerical approaches in industry-like configurations. The simulations are performed with large-eddy simulations (LES). Numerical issues such as grid resolution and physical issues such as injection of turbulence in the crossflow are addressed in this work. Detailed analyses of the LES predictions and comparisons with data underline the potential of the approach for industry-like configurations. Unsteady and averaged LES solutions of eight-JICF picture most of the single JICF features. The counter-rotating vortex pair, the wake vortices, and the shear-layer vortices are clearly identified in the experiment and by LES. Spectral analysis of the LES predictions reveals proper physical behavior of the different structures and good energy content distribution. Characteristic Strouhal numbers are within experimental scatter

Full Coverage Film Cooling: Comparison Of Experimental And Numerical Data.

[Abstract] An experimental study is carried out on a cooling film issuing from a multiperforated wall of a simplified combustor. The objectives of this work are to achieve a better understanding of the dynamics of the film and to construct a database on a simplified geometry in order to test numerical models. RANS calculations using a multiperforation injection model are performed and compared to experimental results. This approach delivers promising results although some weaknesses appear very close to the wall in the recovery region.

Validation of an Infrared Extinction Method for Fuel Vapor Concentration Measurements Towards the Systematic Comparison Between Alternative and Conventional Fuels for Aviation

Due to an increasing oil price and the obvious influence of the combustion of fossil fuel-derivatives on climate change on one hand and the steady growth of transportation needs on the other, it is necessary to develop alternatives to oil for aviation. For this purpose a specific research program on the investigation of adequate alternative fuels for aviation has been founded by the European Commission’s Framework Program. The project Alfa Bird (Alternative Fuels and Bio-fuels in Aircraft Development) focuses on an identification of possible alternative fuels to kerosene, the investigation of the adequacy of the selected ones, an evaluation of the environmental and economical impact of those and finally the creation of a future perspective for the industrial use of the “best” alternative. The main part of the investigation activities at TU Graz, in cooperation with ONERA Centre de Toulouse and Fauga-Mauzac on these specific topics consists of the analysis of the evaporation of the previously chosen fuel types in comparison to Fully Synthetic Jet Fuel (FSJF). Therefore qualitative measurements to obtain vapor concentration gradients will be done using the Infrared Extinction (IRE) measurement method. Based on a simplified Beer-Lambert-Law the integral vapor concentrations can be obtained. The main hypothesis is that if the line-of-sight extinction due to Mie-scattering is similar for both infrared and visible wavelengths because of the presence of the spray, only infrared light will be absorbed by the fuel vapor, being transparent to visible light. This contribution focuses on the validation of the infrared measurement technique on a well characterized spray. The tests are performed under controlled boundary conditions. Therefore an existing IRE test arrangement at ONERA Toulouse using an ultrasonic atomizer injecting n-octane at atmospheric conditions has been analyzed. Error sources related to misalignments in the hardware have been considered and an iterative alignment method of the laser beams followed by a beam diameter and diffraction analysis have been performed. Optimizing the setup to obtain a stable operation point has been successful. Improved experimental results at this operation point were compared with existing simulation results for the evaporation of the used ultrasonic atomizer. The achieved data has shown good accordance to the existing simulation results. This work has been supported by the Eccomet project (Efficient and Clean Combustion Experts Training) in the framework of Alfa Bird.© 2011 ASME

Fuel Vapor Concentration Measurements by Laser Induced Fluorescence and Infra-Red Extinction: An Investigation on a Monodisperse Droplet Stream

The vapor mole fraction field around a stream of monodisperse acetone droplets is investigated by Planar Laser Induced Fluorescence (PLIF) and Infra-Red Extinction (IRE). The PLIF works develop an interface positioning method based on the Lorenz-Mie Theory and on geometrical optics, which can be applied to the images despite the blooming effect caused by the liquid phase. Quantitative results obtained at two different injection temperatures concur with the numerical predictions. IRE results — taken at a high repetition rate on the same configuration — are presented. The dynamical behavior, possibilities and constraints of the employed techniques are discussed and an outlook to following investigations is given. This paper presents some PLIF and IRE basics, a description of the test rigs, the post processing of the obtained data and a comparison of the results to a simplified numerical calculation. Finally a discussion of the results and suggestions for improvements are proposed.Copyright