Performance Improvement of Turbofans by Electric Power Transfer

Abstract

With design trends toward the more electric engine (MEE) for the more electric aircraft (MEA), novel technologies can be pinpointed for multi-spool engines. Provided that a multi-spool MEE is equipped with electrical machines connected to each of its shafts, using power electronic converters (PECs) within a common high-voltage DC bus configuration, it is possible to redistribute a desired amount of power between the engine shafts independent of their speeds. This paper presents the impact of electric power transfer (EPT) on engine performance by using a developed 0-dimensional engine model based on the inter-component volume (ICV) method and engine component maps. Generic component maps are scaled to match the design point of the CFM56-3 engine. Validating the simulation results with engine performance data from literature shows that the steady-state error of the speed and fuel consumption is within 1% and 3.5% for the high- and low-speed settings, respectively, which is acceptable for the purpose of power transfer studies. It is shown that a 400 kW EPT system is the best performing for the cases run for the CFM56-3 engine, which can halve the amount of bleed air from variable bleed valves (VBVs). Results show that EPT with the rescheduled VBVs opening improves the engine performance significantly at low-speed settings by decreasing fuel consumption and increasing surge margins. Detailed simulation results from the engine model and EPT weight penalty analysis show that fuel consumption for short- and medium-haul flights reduces by up to 0.46% and 0.79% with state-of-the-art, and 0.60% and 1.0% with future technologies, respectively. Furthermore, results show that electric power transfer can recover the surge margins of degraded engines at high-speed settings.