A Computational Assessment of Surge-Induced Inlet Overpressure Distribution for Preliminary Design

Abstract

Emphasis on tactical aircraft cost reduction has motivated efforts to reduce air induction system cost, which is mainly driven by structural weight. Historically, inlet structural weight has been set by the peak loads associated with engine surge-induced hammershocks. Therefore, an accurate assessment of peak inlet pressure distribution occurring during an engine surge is critical to successful design of next-generation inlet structure for minimum weight and adequate safety margin. Current methods to quantify these inlet loads during preliminary design stages of an advanced inlet are inadequate. A cost-effective, computational methodology was developed to address this issue. This methodology predicted F-16 Normal Shock Inlet overpressure design loads to within 3% of existing methods. The sensitivity of inlet overpressure distribution to the engine face waveform and inlet geometry was investigated. This technique was also applied to an advanced inlet to study the effects of serpentine ducts and 3-D inlet apertures on hammershock loads.