Thermal and Element Analyses for Supercritical RP-3 Surface Coke Deposition under Stable and Vibration Conditions

A surface coke deposition mechanism on the supercritical aviation kerosene RP-3 was studied under stable and vibration conditions. The flowing RP-3 kerosene is pressurized to 5 MPa and heated from 400 to 723 K in a stainless tube (inner diameter, 1.8 mm; outer diameter, 2.2 mm; and length, 1800 mm) with a constant heat flux. The experimental mass flow rate is fixed at 3 g/s (1180 kg m(-2) s(-1)), and the working fuel flows downward through the test tube. The 1 h stable, 1 h with 600 Hz vibration, and long duration with 566 Hz vibration tube jam experiments were performed. The two vibration frequencies are close to the main frequencies of the combustion chamber vibration when it works. Flow resistance, heat-transfer characteristics, coking amount, and component analysis were compared between stable and vibration conditions. The results indicate that vibration can affect the coking distribution much more uniformly and extend the tube working time. Also, vibration inhibits the exponential growth of flow resistance by changing coke formation compared to the stable condition. Three obvious regions for heat transfer are considered during the long-duration vibration experiments. For coking element analysis, trace elements of Cu have more apparent catalytic effects under vibration conditions. The elements Fe and Cr have a higher content in the downstream section of the tube because of crushing caused by vibration.