Investigation on the Near-nozzle Field Flow of Liquid Jet in a Supersonic Crossflow

摘要

The present paper focused on the near-nozzle field flow characteristics of a liquid-fuel jet injected into a supersonic crossflow, where clear flow structures were imaged by using the high-speed schlieren method. The influence of operating conditions on the shock and separated region was the key mission. A real flight condition with Mach number of 4.5 and flight altitude of 18.5km was simulated. The stagnation temperature and Mach number of the supersonic air flow in the chamber maintained at the constant of 300K and 2.1, respectively. Pure water was chosen as the injection medium instead of actual fuel in this experiment. Three main parameters were tested, including two different diameters of 1mm and 1.4mm, two different stagnation pressures of 700kPa and 891kPa, and injection pressures ranging from 1.25MPa to 3.08MPa. In the study, the transient images at high temporal-spatial resolution were obtained, and clear structures of shock waves were captured. Based on the regularity of a large number of image data, the flow field waves are divided into three parts, named 'zone I ', 'zone II', and 'zone III' respectively. It is found that the position of the separated region characterized by X -type shock in the 'zone I' is relatively stable and hardly affected by operating parameters. The starting position and separate distance of the bow shock are determined primarily by the nozzle diameter, the density and Mach number of supersonic crossflow. And separate distance could be fitted into an empirical formula. The angle of the bow shock is obviously affected by the limited space. Under the experimental conditions, the angle of the bow shock is less affected by the operating parameters. While because of the limited space, the angle value is approximately equal to the oblique shock angle of a 3.1° tip in the supersonic airflow.