In the future, fossil fuels will be replaced by renewable sources. Hydrogen seems to be a promising energy carrier (fuel). A lot of research has been conducted on the combustion of hydrogen, but the effect of the high diffusivity of hydrogen compared to other species (differential diffusion) was often not included in simulations of turbulent flames because turbulent mixing is expected to suppress strong influence of differential diffusion. Nevertheless effects of differential diffusion have been reported in experiments. The main purpose of this thesis is to include the effect of differential diffusion in a CFD model of turbulent non-premixed hydrogen flames and to validate the models with available experimental data. The validation data set used in this study is a non-premixed turbulent jet flame of hydrogen diluted with nitrogen on 50/50 volume ratio. This flame is interesting because the role of differential diffusion in this flame has been a matter of discussion in the literature.

A review is given of previous work on turbulent non-premixed hydrogen flames and effects of differential diffusion. It is concluded that the Flamelet Generated Manifold (FGM) model and the Transported Probability Density Function (PDF) model are both promising turbulent combustion models for these flames. Next, a new comparative study is made of several turbulence and combustion models using Reynolds-averaged Navier Stokes simulations in Ansys Fluent, and focusing on FGM as turbulent combustion model. It is concluded that the standard k-e with a correction as suggested by Pope is the best choice for the turbulence model. The ANSYS Fluent implementation of FGM does not have the option to include differential diffusion. Therefore it is added in a separate way. To do this, flamelets are created with the help of CHEM1D, a tool developed by TU Eindhoven. These flamelets are combined to an FGM table also including the effect of turbulence via a PDF and this table is imported into Fluent with the help of a user-defined function overwriting the default Fluent FGM table.

In order to clearly see the effects of differential diffusion, simulations with and without differential diffusion are made. Good agreement is obtained between experimental results and the numerical simulation for the models without differential diffusion. This confirms that turbulence can suppress strong influence of differential diffusion. In experiments effects of differential diffusion have been observed at the base of the flame, close to the burner nozzle. The model simulations with differential diffusion included, provide a slightly more accurate prediction of the mean temperature close to the nozzle but still large discrepancies remain.
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Multiple concepts for hybrid vehicles capable of both road and flight transport are becoming a reality. However, through incorporation of both flight and road hardware into one vehicle these designs become inefficient. The aim of this project is to design an alternative strategy for realising optimised hybrid vehicles. The objective of this project is to "Develop a personal transport vehicle suitable for commuter use on which flight hardware can be attached within 5 minutes, by 10 students within 10 weeks". This was derived from the mission statement which was to "Develop a faster and cheaper personal transport vehicle for the European market with detachable flight/road hardware that combines the advantages of road transport with flight capability". From this objective, the three most key requirements are that the vehicle shall have a road and flight configuration, that the flight hardware shall be separable from the road hardware and that the flight hardware shall be attached/detached from the road hardware within 5 minutes. When analysing the performance of the vehicle, typical flight stages and stalling configurations were investigated in terms of speed and power setting. At cruise speed, the 12 DEP (Distributed Electric Propulsion) propellers in the midsection of the wing are turned off and folded . However, for take-off and landing configuration, all the propellers are switched on. For fuel use two options are present. E10 gasoline for maximum range, or E85 for decent range, but a 70% lower eco-impact. 122 kW of power is supplied to the 6 outboard motors during cruise. The take-off distance is 450 m and the landing distance is 462 m. Two different propellers were designed and optimized for DEP and cruise conditions. To verify the noise requirements, a propeller noise analysis of the vehicle was carried out, since that is the largest contributer to overall vehicle noise. From that analysis it was concluded that the propeller noise level of the vehicle is 52.3 dBA at 1000 ft, which is low compared to other general aviation aircraft. The airfoil of the wing was selected using the design lift coefficient of 0.56. The airfoils chosen for the wing and tail are, respectively, theNACA4418 andNACA0012. Thewingwas designed to have an aspect ratio of 17, a surface area of 8.414 m2 and a span of 11.96 m. Using these values, the induced drag and pitching moment coefficients were determined. To investigate the overall efficiency of the aerodynamics of the wing, the lift over drag ratio (L/D) was calculated for each configuration. For cruise, landing and take-off, the L/D is 12.93, 7.74 and 9.48, respectively. The packaging of the vehicle resulted in the centre of gravity of the operative empty weight of the full configuration to act at 37.4% of the fuselage length at an empty mass of 1174.7 kg. The longitudinal and lateral stability and control of the vehicle were assessed. Due to the large downwash caused by the DEP propellers of the wing, a T-tail configuration was designed to move the tail away from the downwash and make it more effective. A fully-movable horizontal tail was necessary to counter the large lift coefficient and, consequently, the moment created by distributed electrical propulsion. The horizontal and vertical stabiliser were designed with a surface area of 2.42m2 and 1.1m2 respectively. After analysing the strengths and manufacturing methods of several materials it was found that the wingbox would be made using aluminium (AL7075-T6) with taper in the sheet thickness. Due to the slender wing, the weight of the wing became relatively high at 200 kg. For the skin, the most suitable material was polyester with glass fibres for its specific strength, price and compatibility with a foam or balsa core. For the linkage system, the location where the linkage is established needed to be considered. After investigating this, it was determined that the best place for the linkage would be the rear of the road hardware and the front of the flight hardware. For the linkage the Scharfenberg train coupling was used together with safety pins. The Scharfenberg connection was scaled down to suit the vehicle as it was originally designed for trains. After the final design is concluded, it is necessary to plan for future research in order to make this concept a reality. There are still uncertainties in how DEP affects the performance and aerodynamics of the concept. Therefore, it is recommended to conduct more lowspeed tests to properly establish those effects. Computational FluidDynamics (CFD) and wing tunnel testing is also recommended to visualise and analyse the fluid flow of the wing. A structural analysis using the finite elementmethod and full scale tests of themajor components are also recommended. As the coupling mechanism has never been used in aerospace application, further research into the adaptability and the integration of this mechanism should be performed. As a single-engine Private Pilot License is preferred, recommendations were also made on tests that need to be performed in order to make a case for the airworthiness authorities. ... Read more