Wei Li

This study investigates the effects of inlet rotation angle on the lean ignition and blowout characteristics of an integrated afterburner under high-temperature rotating inflow conditions. Ignition and blowout experiments are conducted in an integrated afterburner with a single strut-cavity structure. The lean ignition and blowout fuel–air ratios are measured at strut trailing-edge Mach numbers ranging from 0.20 to 0.35 and rotation angles from 0° to 15°. Numerical simulations are also performed to analyze the effects of inlet rotation angle on the flow field structure, fuel atomization and mixing, and combustion characteristics. The results show that: 1) as the inlet rotation angle increases, the lean ignition and blowout fuel–air ratios follow a nonmonotonic trend, initially decreasing and then increasing, with optimal performance occurring at a rotation angle of 5°; 2) a small rotation angle enhances flame retention within the recirculation zone, promotes secondary fuel atomization and mixing, and improves local combustion conditions; 3) a larger rotation angle weakens the recirculation zone downstream of the strut, shifts the shear layer outward, and increases local heat dissipation, raising the risk of flame blowout. This study provides a valuable reference for optimizing combustion organization and designing stable lean-blowout combustion in integrated afterburners.

In this study, a high-speed camera was used to investigate the effects of auxiliary atomization methods on the spray characteristics of a direct-injection nozzle operating under high-temperature and large-Mach-number conditions. Three configurations were examined: (1) adjusting the coflow pressure of circular holes, (2) varying the nozzle insertion depth, and (3) altering the relative position between the circular-corner rectangular coflow holes and the nozzle. The quantitative analysis focused on the breakup length, fuel concentration, droplet size distribution, and oscillation behavior. The results are summarized as follows: (1) The flow boundary layer is thinner than the thermal boundary layer; thus, increasing the nozzle insertion depth decreases the penetration breakup length, while the impinging breakup length remains unchanged with variations in coflow pressure or hole configuration. (2) Because the circular coflow air jet exhibits weak momentum, the coflow pressure hardly affects the breakup length, concentration boundary, droplet distribution, or main oscillation frequency. (3) For the circular-corner rectangular coflow, the relative position of the liquid and low-temperature air jets does not change the breakup length but affects the pulsation frequency and fuel concentration boundary. Moreover, the concentration boundary is maximized when the air jet is upstream and the fuel jet is downstream.

To reconstruct the three-dimensional (3D) cold flow field of a triple-stage axial swirler, this study uses two-dimensional (2D) particle image velocimetry (PIV) to capture flow structures across multiple axial, radial, and tangential sections. Downstream 3D flow features—velocity fields, recirculation zones, streamlines, turbulence, and vorticity distributions—are reconstructed using linear interpolation and velocity filling techniques. The key findings are as follows: (1) Interpolated data at integer–coordinate sections closely correspond to experimental results, confirming the accuracy of the linear interpolation method. (2) Flow structures from densely interpolated sections show strong agreement with original data, with maximum absolute and relative errors for all three velocity components staying within acceptable engineering tolerances. (3) The reconstructed sections exhibit flow structures consistent with the original measurements, validating the accuracy of the 3D reconstruction methods. (4) Momentum exchange between the swirler stages generates a unified clockwise swirling jet. Downstream, the flow develops a layered structure consisting of three zones: the corner recirculation zone, the high-speed swirling shear layer zone, and the central recirculation zone. Turbulent intensity and kinetic energy peak near the swirler exit and in high-shear regions. (5) Inner and outer shear layers appear as inherent characteristics of swirling flows, independent of the triple-stage design. By combining experimental PIV measurements with computational reconstruction techniques, this study characterizes the 3D cold flow dynamics of a triple-stage axial swirler. This methodology provides a novel way to transform 2D PIV data into volumetric flow information.

A rapid engineering ignition prediction method for an aero-engine swirling two-phase spray was developed using the commercial software Fluent combined with user-defined function, which considers the influence of spray dispersity on the ignition process. Experimental data related to the ignition study were obtained via optical measurements to verify the reliability of the proposed ignition prediction method. Then, the ignition performance at various ignition positions within a combustor was predicted under ground conditions. Results indicate the following: (1) The numerical calculation method for nonreacting flow is verified using particle image velocimetry and planar Mie scattering test data, which can be used to accurately capture the flow field and fuel mist field distribution characteristics of the swirling two-phase spray combustor. (2) A low Karlovitz number and an appropriate flammability factor are exhibited in the vicinity of the igniter plug and throughout most regions in the combustor. Such distribution characteristics provide favorable conditions for the formation and growth of the initial flame kernel. (3) Within the investigated range of ignition positions, the ignition performance improves with the ignition position gradually moving away from the dome of the combustor. Consequently, to improve the ignition performance within the combustor under ground conditions, it is recommended to move the existing igniter plug backward along the central axis of the combustor. The above-mentioned research results provide a rapid numerical research method for the ignition optimization design of aero-engine combustors in engineering.

Pre-filming atomizers are used in low pollution center staged combustion chambers, which face high-altitude and low-temperature ignition problems during the operation of aircraft engines. By using a pre-filming atomizer, a thin liquid sheet is formed on the plate and encounters a high-velocity swirling airstream which lead to the atomization of the fuel. In this study, an experimental investigation was conducted to explore the flow characteristics and atomization characteristics of a pre-filming atomizer with low-temperature fuel. The dynamic process of the fuel atomization in the pre-filming atomizer was measured, and the fluctuation frequency, breakup length of the liquid film surface, and the spray particle size in the secondary atomization area were obtained. The results demonstrate that the atomizer flow number increases with a reduction in fuel temperature, attributed to the increased fuel density and mitigated cavitation effects. Concurrently, as the fuel temperature decreases, the surface fluctuation frequency of liquid film diminishes due to the heightened surface tension and internal viscosity of the fuel. The aerodynamic shear force reduces as the relative velocity between the fuel and air flow decreases, leading to an extended average liquid film breakup length. And the spray particle size generated in the secondary atomization area increases slightly due to the relatively minor impact of fuel temperature on atomization characteristics compared to the dominant role of aerodynamic forces. Finally, the fuel temperature mainly affects the atomization characteristics of the pre-filming atomizer by the physical properties and fuel flow rate, which is primarily represented under small air flow conditions.