This study presents a systematic investigation into the transverse spray dispersion characteristics of three pressure nozzles, a self-excited sweeping nozzle, a plain-orifice nozzle, and a hollow-cone swirl nozzle, under high-speed crossflow conditions at Mach number 0.4. Initial characterization of their fundamental atomization performance was conducted in quiescent air, followed by spray field visualization in high-speed flow using planar laser Mie scattering imaging to quantify transient spray structures and time-averaged droplet concentration distributions. The results show that the self-excited sweeping nozzle demonstrated intermediate atomization performance between plain-orifice nozzle and hollow-cone swirl nozzle in quiescent environment. In high-speed crossflow, however, the self-excited sweeping nozzle achieves a 67% greater maximum penetration depth than the swirl nozzle and reaches 79% of that of the plain-orifice nozzle, and its spanwise spread distance matches the swirl nozzle, both 150% exceeding the plain-orifice nozzle. Assuming a rectangular spray distribution area, the total coverage area of the self-excited sweeping nozzle is 1.67 times that of the swirl nozzle and 2.17 times that of the plain-orifice nozzle. Moreover, the high-concentration droplet regions in both the central and lateral cross-sections of the self-excited sweeping nozzle are significantly larger than those of the other two nozzles, demonstrating superior spray uniformity. This study preliminarily confirms the unique advantages of the self-excited sweeping nozzle in enhancing spanwise diffusion, total spray coverage, and distribution uniformity in high-speed airflow environments. These findings provide a novel technical solution for liquid injection applications under high-speed airflow conditions such as scramjet/afterburner combustors and jet precooling systems.

To prove the feasibility of applying the self-excited sweeping nozzle in the afterburner, and the effectiveness of high frequency dynamic sweeping fuel injection methods for improving the efficiency of afterburner combustion, this study designed a fuel spray bar integrated with the self-excited sweeping nozzles, tested its basic working characteristics, such as flow rate, frequencyand sweeping angle, and further compared these characteristics with the plain-orifice spray bar. Then, based on the rectangular afterburner test rig, under the same test conditionsand the fuel-to-air ratio range, the overall combustion efficiencies are testedand the dynamic wall pressure pulsation information is monitored, employing the plain-orifice spray barand self-excited sweeping spray bar respectively. The results show that multiple self-sweeping nozzles can be integrated into the spray bar with the diameter limitation of 10mm. the flow capability of the self- excited sweeping spray bar is increased by 23%, compared to the plain-orifice spray bar with the equivalent geometric flow area. For the nozzles in the same spray bar, their operating frequencyand sweeping angle responses to the pressure drop are basically the sameand have good consistency. The afterburner combustion efficiency is improved by 3.7%, by employing the self-excited sweeping spray bar, and no dynamic pressure pulsation frequency is detected which is the same or close to the operating frequency of self-excited sweeping nozzle, indicating that high frequency dynamic sweeping fuel injection has no direct impact on the flame thermoacoustic oscillation modeand large scale shedding vortex structure downstream the flameholder.

To further prove the effectiveness of self-excited sweeping nozzles in enhancing afterburner combustion performances under the constraints of practical application conditions, this study first designed an afterburner fuel spray bar containing 10 self-excited sweeping nozzles, and then a plain-orifice spray bar was designed for comparison with the same nozzle number, injection locations, and total flow rate. The flow rate, frequency, and injection angle of both spray bars were measured and analyzed. Then, under the typical bypass airflow conditions of a turbofan engine with an airflow of high speed and medium temperature, combustion efficiency at the exit cross-section, temperature distribution along the path, and dynamic wall pressure fluctuations were measured using on a rectangular afterburner combustion performance test bench with the plain-orifice and self-excited sweeping spray bars respectively. The results showed that the self-excited sweeping spray bar significantly expanded the blowout limit of the combustion chamber compared to the plain-orifice spray bar, and improved combustion efficiency across the entire fuel-to-air equivalence ratio range, with a maximum improvement of 8.5%, and the gas temperature along the path increased by up to 181 ℃. At a higher equivalence ratio, the plain-orifice spray bar induced a low-frequency longitudinal thermoacoustic coupling oscillation at around 140 Hz, with a pressure relative pulsation amplitude of 16.3%. In contrast, under the same conditions, the self-excited sweeping spray bar reduced the pressure relative pulsation amplitude to only 2.3%, effectively suppressing combustion instability. This study fully demonstrates the notable results of self-excited sweeping nozzles in improving combustion efficiency, expanding the blowout limit and suppressing combustion instability of the afterburner.

This paper studies the internal flow dynamics of a continuous-discrete pulsing jet fluidic oscillator and the influence of splitter on its outlet peak velocity and oscillating frequency. For that purpose, two-dimensional unsteady numerical simulations were conducted, covering five different inlet mass flowrates $\dot{m}$ and three oscillator models (two continuous-discrete pulsing oscillators with different splitting distances and a continuous sweeping oscillator).Results show that there are at least three different velocity peaks in one period at both outlets of continuous-discrete pulsing oscillators. When the splitting distance increases, the first peak velocity (U_max,1,O) decreases, the third one (U_max,3,O) increases, while the second peak velocity (U_max,2,O) is less affected; the three peak velocities generally satisfy U_max,3,O＞U_max,1,O＞U_max,2,O , unless $\dot{m}$ is extremely large or small.When the splitting distance increases, oscillating frequency decreases at first and then increases, but the frequency of continuous sweeping oscillator is always the highest and the difference of the other two keeps rising as $\dot{m}$ increases.Results also show that when the splitting distance was increased or $\dot{m}$ was reduced to a certain extent, the outlet velocity’s oscillating pattern changes, including the significant velocity fluctuations both before and after U_max,1,O, the phase shift and the great amplitude increase of U_max,2,O.The research results are of great importance in supporting the design optimization of the continuous-discrete pulsing oscillator and the development of flow control method with this kind of fluidic actuators.