Total Temperature Probes for High-Temperature Hypersonic Boundary-Layer Measurements

Abstract

this report is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration. Summary This paper presents design details and test results of two types of total temperature probes that were used for hypersonic boundary-layer measurements in the Langley 8-Foot High-Temperature Tunnel. The intent of each probe design was to minimize the total error and maintain a minimal size for measurements in boundary layers 1.0 in. thick and less. A single platinum--20-percent-rhodium shield, used in both designs, minimized radiation heat transfer losses during exposure to the high-temperature test stream. The main design difference was the vent-to-inlet area ratio. To reduce vertical averaging effects on the data, the shield of the initial design (probe A) was flattened at the flow entrance to an interior height of 0.03 in., which resulted in a vent-to-inlet area ratio of 50 percent; to reduce vertical averaging effects near the wall even further, the shield of the later design (probe B) was flattened to 0.02 in., which resulted in an area ratio of 60 percent. A stainless steel structural support sleeve that was installed on probe A was excluded from probe B, which resulted in a probe B outer diameter of 0.059 in., to allow closer placement of the probes to each other and to the wall. These small design changes to improve the resolution did not affect probe performance. Tests were conducted at boundary-layer-edge Mach numbers of 5.0 and 6.2. The nominal free-stream total temperatures were 260