Search

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All the studied droplets exhibit a short transient heating phase and a steady-state evaporation phase obeying d2. Notably, the expansion of the transient heating phase gradually increases with increasing ambient pressure. The change in diameter squared ∆d2max increases from 1.03% at 1 MPa to 12.48% at 5 MPa. Under subcritical conditions, the evaporation rate decreases linearly with decreasing droplet diameter, and the droplet evaporation lifetime increases linearly. Changes in the initial droplet diameter may still have a large effect on droplets smaller than those studied here. When the ambient pressure is not greater than 3 MPa, the change in the steady-state evaporation time for both medium- and large-diameter droplets accounts for more than 70% of the variation in the droplet evaporation lifetime. As the ambient pressure increases to 4 MPa and 5 MPa, the percentage of the change in the transient heating time contributing to the variation in the droplet evaporation lifetime gradually increases to more than 45%.

This study conducted 3D numerical simulations to investigate the impact of combustion chamber diameter on the combustion characteristics of liquid kerosene scramjet rotating detonation under high Mach number flow conditions (Ma6/28 km). After ignition, a local hotspot near the contact surface between the combustion product and fresh reactant facilitates the generation of new detonation wave heads, resulting in a co-directional multi-wave mode in the detonation combustion flow field. The higher total temperature of the incoming flow restricts the accumulation of a substantial fuel gas layer in the axial direction of the combustion chamber, resulting in a smaller fuel distribution area and a lower wave head. Increasing the inner diameter of the combustion chamber leads to an increase in the number of wave heads but a decrease in overall height. Specifically, when using diameters of 125 and 150 mm, we observed significant periodic low-frequency oscillations in the peak pressure of the detonation wave during stable propagation. The specific impulse of the fuel does not vary significantly across different combustion chamber diameters. However, when the inner diameter is 75 mm, periodic oscillations occur, which reduce thrust stability. These findings provide valuable insights into optimizing combustion chamber design and improving the efficiency and stability of liquid kerosene scramjet rotating detonation propulsion systems under high Mach number flow conditions.

A planar Langmuir probe, which can be used for both ion electric propulsion beam characteristics measurement and plasma diagnosis, was developed and applied to plume measurement and diagnosis experiments of an 8 cm Kaufman ion thruster to address the growing demand for miniaturized ion thruster plume measurement and diagnosis. The experimental results show that the plume area exhibits good symmetry along the central axis, and the beam dispersion angle of the 8 cm ion thruster is approximately 22.7°. The radial distributions of the floating potential, plasma space potential and ion density are similar, showing a high distribution in the middle and a relatively low distribution at the two ends. The miniaturized ion thruster plume measurement and diagnosis system is not only easy to manipulate, but also fast and efficient for plasma plume measurement and diagnosis, which provides more complete data support for analyzing the working state of the miniaturized ion thrusters and optimizing the design of the thruster structure.