| A study of in-tube aerodynamic heating of ram accelerator projectiles is presented. The ram accelerator is a ramjet-in-tube device which propels projectiles supersonically through a combustible gas mixture. Many aspects of ram accelerator operation have been studied extensively in the past few years; however, to date most research has not focused on the effects of projectile heat transfer. The current study involves computer simulations of ram accelerator operation, emphasizing the study of aerodynamic heating. The computer simulation couples a TVD finite-difference CFD solution of a viscous turbulent flow field with a semi-implicit solution for the temperature of the solid projectile material. Typical material properties and velocity histories from laboratory experiments were used in the simulations. The results of these computer simulations show that significant increases in temperature are predicted on the nose tip and near the base of the nose cones, where shock impingement occurs. A stress analysis shows that aluminum nose cones are predicted to blunt significantly. Additional simulations show that other aluminum nose configurations, including hemispherical tips and larger nose cone angles are predicted to experience significant tip erosion. In contrast, nose cones made of more refractory alloys, including titanium, titanium-coated aluminum, and steel are predicted to retain structural integrity, and thus attain higher maximum speeds. |
