(Georgia Institute of Technology, 2023-01)
Clark, Robert A.; Perron, Christian; Tai, Jimmy C. M.; Airdo, Benjamin; Mavris, Dimitri N.
The development of an open rotor propulsion system architecture model and fuel burn-minimizing power management strategy is investigated.
The open rotor architecture consists of a single-rotor open rotor (SROR) connected to the low speed shaft of a traditional turbojet engine in a puller configuration. The proposed architecture is modeled in the Numerical Propulsion System Simulation (NPSS) tool, and performance is evaluated across a complete flight envelope typical for a narrow body commercial airliner. Rotor performance maps are generated using a custom blade element momentum theory (BEMT) code, while compressor performance maps are created using CMPGEN. The performance of the overall propulsion system is detailed in the context of a notional 150 passenger aircraft mission, and a method for scheduling rotor power across the flight envelope is developed in order to minimize aircraft mission fuel burn. It is demonstrated that the power absorbed by the rotor can be optimized by scheduling rotor blade pitch angle versus fan speed. A power management technique using the optimal blade pitch angle at only six points in the flight envelope was shown to provide significant computational benefits without sacrificing any fuel burn when compared to a method using a schedule generated from data across the complete flight envelope.
(AIAA, 2023-01)
Clark, Robert; Tai, Jimmy C. M.; Mavris, Dimitri N.
The development of a parametric variable cycle engine (VCE) model is investigated. The model is developed using the multiple design point (MDP) approach, which allows for the sizing of an engine that meets design criteria across multiple flight conditions. The proposed architecture, a three-stream double-bypass architecture, is modeled in the Numerical Propulsion System Simulation (NPSS) tool. A double bypass architecture is selected due to the need to maintain continuous third-stream flow to be used as a heat sink for cooled-cooling and aircraft cooling heat exchangers. Results show that a VCE utilizing an aft variable area bypass injector (VABI), variable compressor inlet guide vanes (IGVs), and variable nozzle throats can be modulated to provide higher sea-level static (SLS) thrust and lower cruise specific fuel consumption (SFC) than a standard mixed-flow turbofan engine. Furthermore, engine pressure ratio (EPR) is shown to be a convenient thermodynamic parameter, such that variable geometry schedules can be developed as a function of EPR only, without respect to flight altitude or Mach number.