Rugged, Scramjet Inlet Temperature and Velocity Sensor: Design and Ground Test

Abstract

The design and testing of a gas temperature and velocity scramjet engine inlet sensor based on tunable diode laser absorption spectroscopy of oxygen is discussed. The robustness and stability of the optical design necessitated by the dynamic vibrational and thermal environment were balanced against the need for compact size and very high signalto-noise ratio in a low-pressure, high-altitude flight regime. Test results demonstrated very good mechanical and thermal stability and an adequate signal-to-noise ratio for altitudes up to 30 km with predicted O 2 absorbance peaks greater than the signal standard deviation by a factor of more than 3. Nomenclature I, I 0 = signal intensity with and without sample gas (arbitrary units) T= I∕I 0 , sample gas transmittance

Analysis of Stresses in Metal Sheathed Thermocouples in High-Temperature Flows

“…Both pressures vary with temperature, as they are the result of the bodies pushing against each other due to thermal expansion. Equations (11)(12)(13)(14)(15)(16) can be used to solve for the radial deformation and three principal stresses:…”

“…To use Eqs. (14)(15)(16) to find the stresses in each body, the four unknown pressures must be found. Using Eq.…”

“…Several other references [13][14][15] look at real-world experimental applications of thermocouples in high-speed flows which show a major need for an accurate and efficient way to predict the stresses in the sheath of a metal-clad thermocouple packed with ceramic material at elevated temperatures. The desire to have highsurvivability thermocouples at elevated temperatures stems from the frequent failure of these probes during testing [13][14][15][16]. The unpredictability of the structural strength of thermocouples even when using detailed three-dimensional (3D) finite element models at great cost and time limits the ability of the designer to achieve an optimized design for the specific application.…”