Turbo For Fuel Cell Electric Vehicle

Sammanfattning: Turbo systems have long been implemented into vehicles to increase the specific power. Increasing the pressure for conventional vehicles decreases the mass of the engine and increases the efficiency. Conventional vehicles do however produce carbon dioxide emissions which have become an increasing issue that needs a solution. One possible solution is the fuel cell utilizing hydrogen as fuel. This report studies and designs the turbo on such a fuel cell and compares how much more improvement a self-designed turbo has compared to a downsized turbo from Volvo. To be able to do the analysis, a simple fuel cell model was constructed in the software GT-Suite using literature and the already given downsized turbo. Here the main goal was to analyze the effect of a turbo’s efficiency on the cycle efficiency, and to acquire boundary conditions to develop a new turbo specifically made for the modeled fuel cell. Once the boundary conditions were given, the turbo was designed in Advanced Design Technology turbomachinery programs: TDpre, TD1 and TDvolute. The turbo consisted of a centrifugal compressor and radial turbine. An impeller, diffuser and volute were designed for the compressor and a volute, nozzle, rotor and diffuser for the radial turbine. In addition, an axial turbine was designed by a professor at LTH so that a comparison could be made between different turbines. All the evaluations of performance were made in CFD with Star CCM+ by Siemens. The thesis showed that the compressor is the most important turbo component when designing a fuel cell turbo. Furthermore, the importance of adding a turbine for the highest possible cycle efficiency was shown, where the cycle efficiency could be increased by up to 16 percentage points, i.e., 59% compared to using only a compressor. The designed turbo gave fuel cell system efficiencies in the range of 42-54%, with a compressor rated at 81% and a turbine rated at 84%. Comparing this to the downsized turbo that was given, gives a relative increase in cycle efficiency between 0.221-1.14%, showing the importance of designing a turbo specifically for the operating conditions.