Dynamic flow instabilities of hydrocarbon fuel in a horizontal heating tube

To investigate dynamic flow instabilities of hydrocarbon fuel in thermal protection structure of the scramjet, experiment was conducted at the pressure of 1.5-3.0 MPa, heat flux of 190-250 kMfm(-2), and the charge pressure at the surge tank of 0.5-1.0 MPa. Three main types of dynamic flow instabilities, pressure drop oscillation, density wave oscillation, and thermal oscillation took place during some experimental conditions. The influence of hydraulic characteristics of the test loop on dynamic flow instabilities was discussed. It was found that dynamic flow instabilities were mainly affected by the hydraulic characteristics of the test loop rather than the heating section. Pressure drop oscillation with large fluctuation amplitude and long period occurred in the negative slope region of the pressure drop curve. Density wave oscillation appeared in the positive slope region with low flow rate. The fluctuation amplitude and period of density wave oscillation were much smaller than those of pressure drop oscillation. Dynamic flow instabilities were more intense at lower pressure and higher heat flux. The oscillation region was independent of the compressible volume. However, a large compressible volume could promote the fluctuation amplitude of both inlet mass flow rate and outlet fuel temperature.