Vehicle-Level Optimization of Rotorcraft Propulsion Systems

The authors have developed a new design and optimization framework to perform conceptual design studies in order to improve the fuel-efficiency of rotorcraft. The framework ties together the state-of-the-art NASA propulsion modeling program, NPSS, and NASA's rotorcraft modeling tool, NDARC. The OpenMDAO multidisciplinary design, analysis, and optimization toolset was used to integrate these two analysis codes. The NPSS and NDARC test-case models have been validated against experimental data and have shown good agreement. In an initial study, advanced technology engines have been evaluated for a search and rescue mission. All engines evaluated showed significant increases in rotorcraft performance in the BK-117 helicopter model, as compared to the baseline engine. An optimized simple cycle engine (low weight and size) and a recuperated engine performed best in the analysis. If minimizing fuel usage for environmental concerns is the key objective, then the recuperated engine is the superior choice. To perform the same search and rescue mission as the baseline BK-117, roughly a 50% fuel savings is predicted.