Jordan A. Snyder

Design and Characterization of the Stanford 6 Inch Expansion Tube

A new expansion tube facility has been constructed at Stanford University to enable research on scramjet combustor design and performance. The facility is designed to allow the duplication of combustor entrance conditions over a range of conditions covering vehicle flight Mach numbers of 4 to 9. The range can be extended to Mach 15 if the simulated pressures are allowed to vary from those of duplication. Details of the design and performance of the new facility are presented including an analysis of test repeatability, boundary layer thickness, and test gas uniformity.

Combustion Stability Regimes of Hydrogen Jets in Supersonic Crossflow

A mapping of regimes of stable, unstable, and no combustion in scramjet combustor conditions and other similar conditions has been undertaken in the recently constructed 6 inch expansion tube at Stanford University. The mapping investigated the effects of stagnation temperature, static temperature, and jet-to-freestream momentum flux ratio. The results agree with previous data, and indicate that for static temperatures of about T = 1375 K and static pressures of about P = 25 kPa, the transition from unstable to stable combustion occurs at a stagnation temperature of between T0 = 2600 K and T0 = 2700 K. Similarly, the transition from no combustion to unstable combustion occurs at a stagnation temperature between T0 = 2300 K and T0 = 2400 K. Increasing jet-to-freestream momentum flux ratio tends to increase combustion stability, while increasing static temperature tends to slightly decrease combustion stability.

Pressure-Sensitive Paint Measurements of Sonic Jet Injection into Supersonic Crossflow

A fast response, porous pressure-sensitive paint (PSP) technique was used to measure the surface pressure field resulting from a 2mm sonic jet injected into supersonic crossflow. These measurements were carried out in an expansion tube facility providing a freestream Mach number of 3.4 for a total test time of 400 μs. Initial work focused on validating the PSP technique and quantifying the response time for use in an impulse facility. Further studies investigated the effect of jet-to-freestream momentum flux ratio (J) at both normal and oblique injection angles. The resulting pressure fields show a strong dependence on J with both upstream pressure and downstream extent of the recirculation zone increasing with increasing J.