Conventional Regional Propulsion vs Distributed Propulsion: Which Is More Efficient?
Propulsive efficiency is a metric used to evaluate the relationship between energy consumption and thrust generation after a propulsion system converts an input energy source into thrust. When propulsion–airframe aerodynamic integration is neglected, larger-diameter propulsors generally exhibit higher propulsive efficiency because they generate thrust by accelerating a greater mass flow of air with a smaller velocity increment. High-bypass turbofan engines are a representative example of this principle. In contrast, when propulsion–airframe aerodynamic integration is taken into account, propulsion architectures employing multiple small propulsors in a distributed propulsion system can achieve higher overall propulsive efficiency through wake-filling effects.
The distinction between these two approaches lies in determining which provides superior propulsive efficiency. Should higher propulsive performance be achieved by employing a small number of large turbofan engines to accelerate a greater mass of air or by adopting a large number of small propulsors that reduce energy losses through wake-filling effects? This question has become an important topic in the development of future aircraft propulsion systems.
The comparison between large turbofan propulsors and distributed propulsion systems is not merely a matter of propulsor size but a system-level design problem that requires integrated optimization. Such system-level optimization encompasses multiple aspects, including aircraft configuration, propulsion system architecture, energy systems, etc. Once alternative energy sources are introduced, the overall aircraft configuration can no longer be designed according to the principles established for conventional fossil fuel-powered aircraft. Instead, future aircraft configurations have to be re-evaluated based on the features and integration needs of the new propulsion-energy system.
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