Surface Deposition Characteristics of Supercritical Kerosene RP-3 Fuel within Treated and Untreated Stainless-Steel Tubes. Part 1: Short Thermal Duration

The thermal oxidation deposition characteristics of kerosene RP-3 have been experimentally studied in the vertical tube at supercritical pressure as a crucial concern for the cooled cooling air (CCA) development. Thermal stressing of the fuel was carried out in a heated tube with stainless steel 321 (SS321, 1Cr18Ni9Ti), pre-oxidized, and electrolytically passivated for 1 h. Under the constant pressure of 5 MPa, all of the experiments were conducted at the fixed inlet and outlet fuel temperatures of 400 and 723 K, respectively, under the same heat flux and flow mass rate. Deposition of the different segments was analyzed using a weighting method to observe the deposition profile of the test section. Moreover, the morphology and components of the surface deposition were examined along each tube, with different surface treatments, to investigate the surface thermal oxidative deposit mechanisms. In this work, it was found that the pre-oxidized and electrolytically passivated treatments could reduce the total deposition about 35.83 and 58.33%, respectively, as a result of the formed passivation layer and reduced surface roughness in the treated progress in contrast to the as-received SS321 tube. On the basis of the scanning electron microscopy (SEM) images and component analysis of the surface deposit, the thermal oxidation deposit on the treated tube surface could be attributed to the adhered deposit formed in the liquid fuel rather than the surface catalytic filamentous deposition on the untreated tubes.