TITLE AND SUBTITLE Computational Method To Predict Thermodynamic , Transport , and Flow Properties for the Modi ed Langley 8 - Foot High - Temperature Tunnel

The Langley 8-Foot High-Temperature Tunnel (8-ft HTT) is used to test components of hypersonic vehicles for aerothermal loads de nition and structural component veri cation. The test medium of the 8-ft HTT is obtained by burning a mixture of methane-air under high pressure; the combustion products are expanded through an axisymmetric conical-contoured nozzle to simulate atmospheric ight at Mach 7. This facility has been modied to raise the oxygen content of the test medium to match that of air and to include Mach 4 and Mach 5 capabilities. These modi cations will facilitate the testing of hypersonic air-breathing propulsion systems for a wide range of ight conditions. A computational method to predict the thermodynamic, transport, and ow properties of the equilibrium chemically reacting oxygen-enriched methane-air combustion products has been implemented in a computer code. This code calculates the fuel, air, and oxygen mass ow rates and test section ow properties for Mach 7, Mach 5, and Mach 4 nozzle con gurations for given combustor and mixer conditions. Salient features of the 8-ft HTT are described, and some of the predicted tunnel operational characteristics are presented in the carpet plots to assist users in preparing test plans. Introduction The Langley 8-Foot High-Temperature Tunnel (8-ft HTT), which became operational in the 1960's, primarily has been used to de ne thermal and structural loads on large models at hypersonic speeds. Although many other hypersonic facilities were abandoned in the early 1970's, this tunnel is still operational and quali es as a unique national facility. A resurgent interest exists in the development of airbreathing hypersonic vehicles that can y at hypersonic speeds within the atmosphere. This interest is evident from the current development program of the National Aero-Space Plane (NASP), which is envisioned to be a hypersonic aircraft that can y directly into orbit from a conventional runway (refs. 1 and 2). To develop and improve advanced propulsion systems required for vehicles such as NASP, test facilities must simulate conditions that are encountered by the vehicle during its mission. Although the high-temperature test medium of the methaneair combustion products produced in the 8-ft HTT does not have the oxygen content of air, it has been useful for aerothermal loads de nition and structural component veri cation. However, engine testing requires oxygen enrichment because most of the oxygen available in the air is used in the combustion of methane and the test medium cannot support further combustion in the engine. The need for largeengine test facilities to develop air-breathing engines for hypersonic ight prompted the modi cation of the 8-ft HTT. The modi ed facility can be operated in the oxygen-enriched combustion mode to produce 21 percent oxygen by volume in the test section or in the no-oxygen-enriched mode. The addition of Mach 4 and Mach 5 nozzle con gurations will also complement the existing Mach 7 capability. Figure 1 illustrates the operational envelopes, in terms of Mach number and pressure altitude, for the 8-ft HTT and two other facilities (the Aero Propulsion Test Unit (APTU) and the Aero Propulsion System Test Facility (ASTF) of the U.S. Air Force Arnold Engineering Development Center (AEDC)). Also superimposed around the facility operational envelope is a typical air-breathing engine operational envelope. The upper altitude limit is imposed by the ability of the engine to sustain combustion, and the lower altitude limit is imposed by the ability of the structure to survive the aerothermal loads. The inclusion of Mach 4 and Mach 5 capabilities enhances the testing envelope of the 8-ft HTT in the turbojet and ramjet operating ranges. However, the lower altitude limit of the facility with oxygen enrichment is restricted because the LOX (liquid oxygen) tank pressure limit is 2300 psia, which limits the combustor pressure to 2000 psia. This report describes a computational method to predict test section ow properties at the nominal Mach numbers of 7, 5, and 4 for the 8-ft HTT. The ow is assumed to be in chemical equilibrium. Salient features of the 8-ft HTT are discussed to make the code requirements clear. The tunnel operational characteristics are presented for both the methaneair and methane-air-oxygen modes. Symbols A nozzle throat cross-sectional area, ft a acoustic velocity, ft/sec Cp molar heat capacity of species, Btu/moleR cp speci c heat capacity of gaseous mixture, Btu/lbmR FSA ow survey apparatus g acceleration due to gravity, ft/sec2