Fast-response, electronically-scanned multi-port pressure system for low-pressure hypersonic wind tunnel applications

Abstract

A fast-response, multi-port, electronically-scanned pressure (ESP) system applicable to very low pressure hypersonic wind tunnel environments has been developed and demonstrated. The system incorporates a Pressure Systems Incorporated (PSI) Model 8400 pressure measurement system with remote processor, and two 48-port PSI ESP modules of 0.36 psid and 1.0 psid full-scale-output, respectively.To achieve minimum pressure lag time, the modules are mounted internal to a variable-geometry, 10.39 in. long, 4.00 in. base diameter wind tunnel model, and are provided with a zero reference to yield absolute pressure. The use of minimum length tubing has led to observed pressure lag times of 0.3 sec or less for all pressure ports and flow conditions. Absolute pressure measurement accuracy is typically +/-0.001 psia. The fast response and high accuracy make feasible the design and execution of precision CFD code validation esperiments in lowpressure hypersonic wind tunnel flows. The pressure system is described in detail and representative results presented for a hypersonic research vehicle configuration in Sandia's Mach 8 Hypersonic Wind Tunnel at freestream static pressures of ii 0.04 psia. Measured surface pressures range from 0.006 psia to over 1.2 psia. Free-stream Reynolds number is approximately 2 milliodft. At this Reynolds number, flow over the model is laminar. ' -