Instrumentation for transient gas velocity, pressure and heat flux measurements in a gun simulator

Microcomputer-based instrumentation for transient measurements of pressure, wall heat flux, and gas velocity in a Lagrangian gun simulator is described, and sample results are presented. The breech pressure was measured by a piezoelectric transducer and the surface temperature was measured by a fast-response thin-film resistance thermometer. The pressure and temperature signals were sampled by a microcomputer and transferred into memory at an overall rate of 80 kHz using a 12-b analog/digital and direct memory access board. Gas velocity measurements were obtained by a dual-beam laser Doppler velocimeter with a counter-based signal processor interfaced via a purpose-built buffer memory to the microcomputer, capable of data rates up to 500 kHz. The microcomputer controls the simultaneous sampling of all three signals and is activated by an external pulse from an optical trigger circuit. The microcomputer stores the data for each test, subsequently processes the temperature data to evaluate the heat flux, and performs statistical calculations on the velocity data to yield ensemble averaged quantities