Performance Comparison of More Electric Engine Configurations

Abstract

An analytical study was undertaken to investigate the fuel burn potential of More Electric Engine (MEE) configurations using the performance model of a 2-shaft high BPR 20–30 klbf turbofan in revenue service. The 3 following power off-take configurations were compared: an HP-generator, an LP-generator, and a split-power generator (small HP starter/generator and a main LP generator). For this study, because of the small performance differences, high accuracy steady-state and transient performance models must be used. For steady-state operating conditions, the design point was modified and the off-design redline margins were calculated; ground and flight idle settings were adjusted to yield both the lowest possible fuel burn and residual thrust within the surge margin of the compressor, and the resulting short range mission fuel burn was calculated. For transient conditions, the thrust response, as well as both HPC and LPC surge margin lapse during engine acceleration and deceleration, had to maintain those of the baseline engine and fulfill certification requirements. This was achieved by modifying the idle settings and acceleration/deceleration schedules. Subsequently, the resulting short range mission fuel burn was calculated. Lastly, an introduction to the business case is provided with a simple cost-effectiveness calculation. This study was an initial investigation into MEE’s that focused primarily on the propulsion unit. For further in-depth studies, it is recommended to consider in detail the business model, aircraft weight issues, and the interaction propulsion performance and aircraft performance.