Richard Avellán

Wake and Loss Analysis for a Double Bladed Swept Propeller

Inspired by Prandtl’s theory on aircraft wings with minimum induced drag, the authors introduced a double-bladed propeller, the Boxprop, intended for high-speed flight. The basic idea is to join the propeller blades pair-wise at the tip to improve aerodynamics and mechanical properties compared to the conventional propeller. The rather complex geometry of the double blades gives rise to new questions, particularly regarding the aerodynamics. This paper presents a propeller wake energy analysis method which gives a better understanding of the potential performance benefits of the Boxprop and a means to improve its design. CFD analysis of a five bladed Boxprop demonstrated its ability to generate typical levels of cruise thrust at a flight speed of Mach 0.75. The present work shows that the near tip velocity variations in the wake are weaker for this propeller than a conventional one, which is an indication that a counter rotating propeller designed with a Boxprop employed at the front may exhibit lower interaction noise.

Aeroacoustics and Performance Modeling of a Counter-Rotating Propfan

This paper presents a method for design and analysis of counter-rotating propfans with respect to performance and aeroacoustics. The preliminary design method generates the ideal optimum propeller design corrected for losses in terms of profile and compressibility drag. The propeller design is further analyzed by computational fluid dynamics, CFD, to calculate the performance and the deterministic interaction noise. The unsteady flow around the propellers is calculated using URANS such that only one blade per propeller needs to be discretized. The unsteady pressure distribution around the blades is integrated, using a Ffowcs Williams-Hawkings method, to an observer for noise evaluation. The results of the performance analysis, the CFD computations and the aeroacoustic analysis are compared with experimental data available from the nonproprietary reports regarding the counter-rotating propellers developed in the 1980s.Copyright

An Assessment of a Turbofan Engine Using Catalytic Interturbine Combustion

The potential for using catalytic combustion in aero engines is discussed. Some preliminaries relating to NOx formation and material capabilities are analyzed. Various means to integrate catalytic combustors in aero engines are described. In particular, catalytic interturbine combustion is investigated both in terms of technical feasibility and through a preliminary design exercise. A thermodynamic design point study is presented analyzing a configuration with a combustor located concentrically around the engine core receiving pressurized air through an interstage high pressure compressor bleed. A parameter study of the compressor bleed ratio is presented for the configuration. A substantial reduction in NOx emissions at the expense of an increase in mission fuel consumption is observed.The potential for using catalytic combustion in aero engines is discussed. Some preliminaries relating to NOx formation and material capabilities are analyzed. Various means to integrate catalytic combustors in aero engines are described. In particular, catalytic interturbine combustion is investigated both in terms of technical feasibility and through a preliminary design exercise. A thermodynamic design point study is presented analyzing a configuration with a combustor located concentrically around the engine core receiving pressurized air through an interstage high pressure compressor bleed. A parameter study of the compressor bleed ratio is presented for the configuration. A substantial reduction in NOx emissions at the expense of an increase in mission fuel consumption is observed.Copyright