Fuel Burn and Energy Consumption Reductions of a Single-Aisle Class Parallel Hybrid Propulsion System

A conventional high performance tube and wing single-aisle aircraft class, parallel hybrid propulsion system comprised of 2 under wing gas turbine engines and a 4.5 MW electric drive train has been studied. The electric drive train (EDT) is comprised of 2 2.1 MW motors, 1 connected to the low spool of each under wing mounted gas turbine engine, 2 motor drives, a 1000 V electric distribution system, a 1500 kW-hr battery pack capable of 4.5 MW discharge (c-rate of 3) and a thermal management system (TMS) capable of maintaining component temperatures at levels required for high life. The system gas turbine (GT) cores are sized for the max cruise condition, thus providing a lower cruise thrust specific fuel consumption (TSFC) at cruise than a conventional GT sized at max climb. The system GT core cannot provide enough max power for take-off and climb, thus the make-up power comes from the low spool motors and the energy comes from a ground charged battery pack. The EDT and TMS weight and performance analysis and the overall propulsion system performance analysis are described. Two mission CoOs (concept of operations) are analyzed with the resultant fuel and energy consumption quantified and compared to a conventional propulsion system based aircraft. The first 900 nm mission CoO carries only the battery pack mass required for boosted take-off and climb, with all energy for cruise supplied by on board fuel. This mission only carries enough fuel to complete the 900 nm mission (plus reserves), thus the vehicle TOGW is well below the vehicle max TOGW capability. The second CoO also considers a 900 nm mission, in which the entire vehicle TOGW capability is utilized. The mix of fuel and battery pack energy/weight is determined to provide minimal mission energy. A fuel burn reduction of 3.4% and energy increase of 0.6% are predicted for CoO-1. CoO-2 provides a fuel burn and energy increase compared to CoO-1. Thus it is not recommend to use the battery back and motors for cruise energy but instead use only Jet-A during cruise.