Aerodynamic shape optimization framework for engine installation in an unconventional airframe

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The major challenge for the transport aircraft industry in the next 20-30 years is the reduction of its carbon dioxide emissions in operation. The development of technologies to increase the energy efficiency of the aircraft must continue in parallel with the efforts to switch the source of energy from fossil fuel to a carbon-free source, such as hydrogen or electricity. The contribution to the jump in efficiency from the change of aircraft configuration alone could be large, up to 30% in the case of the blended-wing body (BWB) through drag reduction. Such revolutionary development however represents an important financial and technological risk, until its associated technology roadblocks are removed. One of these roadblocks is that even though modern engines also improve from generation to generation, their operability and high efficiency remain susceptible to the quality of the flow at the face of the engine or the fan. As the fan blades rotate through successive pockets of changing flow properties, too much spatial gradients from pocket to pocket can lead to issues of stability and structural integrity for the engines. This problem is exacerbated by unconventional configurations, such as the flying wing or the BWB, particularly when the engines are integrated (buried) in the airframe. It is thus important to elevate the maturity of these unconventional configurations to reduce the technological risk. If the flow behavior is not examined early in the design phase and sufficiently stabilized, there is the high risk that the aircraft configuration becomes impractical and that the efficiency gain above is neither protected nor realized. It is proposed to elaborate aircraft configurations with highly integrated propulsion systems beyond the conceptual level, achieving low drag (high efficiency) and taking advantage of passive flow control to maintain adequate flow uniformity at the engine(s) with demanding spatial requirements. With examples of unconventional configurations in the available literature, it is proposed to review, explore and determine aerodynamic shapes for their inlet (S-duct) and the portions of their external surfaces that are affected by the installation of the engine(s), such that these will operate satisfactorily at any flight conditions, thereby removing the technological roadblock associated with propulsion/airframe integration (PAI). Multiple constraints that are representative of the realistic aircraft operating envelope will be considered. A virtual aerodynamics laboratory or test bed will be created through the construction of a design framework for automatic shape optimization. For example, the impact of aero-shaping of the airframe and the inlet will be quantified. The efficiency of a powerplant installed in nacelles on pylon will be compared accurately with that embedded in the airframe.