Experimental Characterization of the LENS Expansion Tunnel Facility Including Blunt Body Surface Heating

Abstract

LENS XX, a new large-scale expansion tunnel facility, has been designed and constructed at CUBRC. This stand-alone facility was designed after successful testing in the prototype LENS X facility. This facility is the largest known expansion tunnel in the world with an inner diameter of 24 inches and an end to end length of more than 240 ft. Aerothermal measurements on blunt bodies are presented as part of the characterization of the new facility. Preliminary results indicate stagnation point heating appears to be enhanced due to a small amount of Mylar debris in expansion tube configuration, but not in the expansion tunnel configuration where the flow is expanded and negligible amounts of debris exist. Data are presented for air near 14 and 21 MJ/kg over a hemispherical and cylindrical model, respectively. Shock layer and stagnation line radiation measurements on a cylinder at 28 MJ/kg are also reported as an example of direct radiation measurements on blunt bodies. Expansion tunnels have showed much promise in recent years with their ability to generate a wide range of hypervelocity conditions with reduced chemistry effects at high-enthalpy conditions in comparison with shock tunnels; however, short test times and test gas disturbances are still practical limitations of this type of facility. The large scale of this new facility offers a large core-flow with increased test time far exceeding other expansion tubes and tunnels.