Advanced Engine Designs and Concepts Beyond the Geared Turbofan

Abstract

The fundamental aircraft engine performance design drivers of propulsive efficiency, cycle thermal efficiency, and engine thrust to weight, along with underlying operational considerations of safety, reliability, and cost, have produced today's state‐of‐the‐art high bypass ratio turbofan found on virtually all commercial aircraft. These same engine performance parameters will continue to drive future aircraft propulsion system design, but will likely require significant changes in engine architecture and engine/airframe integration. Concepts such as the open rotor, distributed propulsion, electric and hybrid gas turbine/electric propulsion, and boundary layer ingestion could significantly alter the way future aircraft appear to the average passenger. Less visibly, alternate engine thermodynamic cycles, such as pressure gain combustion, alternative fuels, and real‐time engine health and performance monitoring may also work to improve engine performance. This chapter examines the role that various advanced propulsion concepts may have in continuing the steady improvement in aircraft propulsion performance that has taken place over the last 100+ years and how these concepts can contribute to reducing the environmental impact of aviation.