Optimization Methodology for Automotive Fuel Cell Centrifugal Compressors

Abstract In this paper we describe the optimization methodology and results for two different fuel cell centrifugal compressors for a 100 kW automotive application. One compressor features a vaneless diffuser and the other a vaned diffuser. The optimized compressors are integrated into a 1D fuel cell system model and evaluated for system level efficiency. The methodology is based on a commercial tool that includes a 3D CFD code to solve the Reynolds-averaged Navier-Stokes equations, a gradient-free Genetic Algorithm as an optimizer, and Radial Basis Function Networks as metamodels to efficiently find the global optimum. To ensure optimal performance across the entire operating range, multiple automotive fuel cell operating points, objective functions, and constraints are considered during the design optimization. At full load design conditions, the isentropic stage efficiency increases by 3.6% for the vaneless diffuser design and 6.2% for the vaned diffuser design compared to a reference design that performs similarly to an off-the-shelf compressor installed in a commercial fuel cell vehicle. Finally, the H2 consumption is predicted using a vehicle model with a stochastic hybrid strategy approach to determine the power split between the propulsion components based on extensive drive cycle data. A reduction in fuel consumption of 0.1% is achieved for the vaneless diffuser design and 0.2% for the vaned diffuser design. The results for the two optimal designs demonstrate the benefit of developing application-specific compressors to further reduce the H2 consumption of novel fuel cell vehicles instead of using existing off-the-shelf components from internal combustion engine applications. The assessment of the merits of the reduction is at the discretion of the fuel cell manufacturers and their specific applications and design objectives.