Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

Electric Power Systems in More and All Electric Aircraft: A Review

Abstract: Narrow body and wide body aircraft are responsible for more than 75% of aviation greenhouse gas (GHG) emission and aviation, itself, was responsible for about 2.5% of all GHG emissions in the United States in 2018. This situation becomes worse when considering a 4-5% annual growth in air travel. Electrified aircraft is clearly a promising solution to combat the GHG challenge; thus, the trend is to eliminate all but electrical forms of energy in aircraft power distribution systems. However, electrification adds tremendously to the complexity of aircraft electric power systems (EPS), which is dramatically changing in our journey from conventional aircraft to more electric aircraft (MEA) and all electric aircraft (AEA). In this article, we provide an in-depth discussion on MEA/AEA EPS: electric propulsion, distributed propulsion systems (DPS), EPS voltage levels, power supplies, and EPS architectures are discussed. Publications on power flow (PF) analysis and management of EPS are reviewed, and an initial schematic of a potential aircraft EPS with electric propulsion is proposed. In this regard, we also briefly review the components required for MEA/AEA EPS, including power electronics (PE) converters, electric machines, electrochemical energy units, circuit breakers (CBs), and wiring harness. A comprehensive review of each of the components mentioned above or other topics except for those related to steady state power flow in MEA/AEA EPS is out of this article's scope and should be found somewhere else. At the close of the paper, some challenges in the path towards AEA are presented. Unless the discussed challenges are satisfactorily addressed and solved, arriving at an AEA that can properly operate over commercial missions will not be possible.

Hybrid-Electric Propulsion for Aircraft

Abstract: Against a background of increasing energy demand and rising fuel prices, hybrid-electric propulsion systems have the potential to significantly reduce fuel consumption in the aviation industry, particularly in the lighter sectors. By taking advantage of both electric motor and internal combustion engine, hybrid-electric propulsion systems provide not only a benefit in fuel saving but also a reduction in takeoff noise and the emission levels. This research considers the design and sizing process of a hybrid-electric propulsion system for a single-seat demonstrator aircraft, the experimental derivation of the internal combustion engine map, and the electric motor parameters. In addition to the experimental data, a novel modeling approach including several linked desktop PC software packages is presented to analyze and optimize hybrid-electric technology for aircraft. Further to the analysis of a parallel hybrid-electric, midscale aircraft, this paper also presents a scaling approach for a 20 kg unmanned aer...

Parallel hybrid powertrain for an automotive vehicle

Abstract: A hybrid powertrain for an automotive vehicle comprising an internal combustion engine and transmission assembly providing a first selectably shiftable geared torque flow path to vehicle traction wheels and an electric motor-generator unit defining a second geared torque flow path that is located between the output of the first geared torque flow path and the traction wheels. Through the deployment of an appropriate control system, including the necessary control algorithms, the electric motor-generator unit can be operated to supply torque to the traction wheels while the torque flow in the first torque flow path is interrupted during the occurrence of a ratio change in the transmission assembly and during disengagement of a clutch. Because of this interactive control of two power sources, the vehicle driveability can be enhanced along with an improvement of the engine exhaust gas emissions. In addition, the electric motor-generator unit in the second torque flow path can be used to launch the vehicle electrically immediately upon request of the operator. This ability of the powertrain permits engine-off operation during vehicle coast-down and standstill periods without any loss of driveability. During electric launch of the vehicle, the interactive control of the two power sources permits the internal combustion engine to be restarted and then gradually take over the propulsion task from the electric motor-generator unit.

Enhanced low-Reynolds-number propulsion in heterogeneous viscous environments

Abstract: It has been known for some time that some microorganisms can swim faster in high-viscosity gel-forming polymer solutions. These gel-like media come to mimic highly viscous heterogeneous environment that these microorganisms encounter in-vivo. The qualitative explanation of this phenomena first offered by Berg and Turner [Nature (London) 278, 349 (1979)], suggests that propulsion enhancement is a result of flagellum pushing on quasi-rigid loose polymer network formed in some polymer solutions. Inspired by these observations, inertia-less propulsion in a heterogeneous viscous medium composed of sparse array of stationary obstacles embedded into a incompressible Newtonian liquid is considered. It is demonstrated that for prescribed propulsion gaits, including propagating surface distortions and rotating helical filament, the propulsion speed is enhanced when compared to swimming in purely viscous solvent. It is also shown that the locomotion in heterogenous viscous media is characterized by improved hydrodynamic efficiency. The results of the rigorous numerical simulation of the rotating helical filament propelled through a random sparse array of stationary obstructions are in close agreement with predictions of the proposed resistive force theory based on effective media approximation.