科研之友
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摘要
A new design method for inward-turning streamline-traced inlets is presented. Resulting designs are intended for low-supersonic low-drag low-boom applications such as that required for NASA's proposed low-boom flight demonstration aircraft. A critical feature of these designs is the internal cowl lip angle that allows for little or no flow turning on the outer nacelle. Present methods using conical-flow Busemann parent flowfields have simply truncated, or otherwise modified, the stream-traced contours to include this internal cowl angle. Such modifications disrupt the parent flowfield, reducing inlet performance and flow uniformity. The method presented herein merges a conical flowfield that includes a leading shock with a truncated Busemann flowfield in a manner that minimizes unwanted interactions. A leading internal cowl angle is now inherent in the parent flowfield, and inlet contours traced from this flowfield retain its high performance and good flow uniformity. Computational fluid dynamics analysis of a candidate inlet design is presented that verifies the design technique, and it reveals a starting issue with the basic geometry. A minor modification to the cowl lip region is shown to eliminate this phenomenon, thereby allowing starting and smooth transition to subcritical operation as backpressure is increased. An inlet critical-point total pressure recovery of 96% is achieved based on computational fluid dynamics results for a Mach 1.7 freestream design. Correction for boundary-layer displacement thickness and sizing for a given engine airflow requirement are also discussed.
- 出版日期2016-9
