Efficient High-Precision Measurement for Micro-Orifice Parameters of Impinging Injectors

Impinging injectors are extensively utilized in liquid rocket engines, characterized by a large number of paired inclined injection orifices. The diameter and axis alignment deviation of these orifices directly influence propellant flow distribution, atomization and mixing behavior, and engine operational stability. To address the challenges associated with micro-sized orifices, inclined axes, large quantities, spatial intersection, and the low detection efficiency of conventional approaches, this paper proposes a dual-line laser 3D point cloud reconstruction-based method for measuring the diameter and impact alignment deviation of injector orifices. A dual-line laser measurement system is established to capture surface point clouds on both sides of the orifice inlets. Through system calibration and point cloud registration, the 3D point cloud data of the injector orifices within a unified coordinate system are reconstructed. Cross-sectional mapping, boundary extraction, and geometric fitting techniques are applied to determine the diameter and axis parameters of the orifices, and the spatial alignment deviation of paired orifices is subsequently calculated. To validate the feasibility of the proposed method, experimental investigation is conducted on test specimens with both 8 pairs of Φ2 mm through-holes and Φ0.5 mm micro-orifices. For the Φ2 mm specimen, the diameter measurement results are compared with industrial computed tomography (CT) data, while the alignment deviation results are verified using a combination of pin gauges and coordinate measuring machine (CMM) measurements. For the Φ0.5 mm micro-orifices, both diameter and alignment deviation results are verified using a 3D coaxial line confocal sensor. After system calibration, the fitting residuals of three Φ8 mm standard spheres are all maintained within 0.08 mm. The diameter measurement results of 8 selected Φ2 mm orifices show good overall agreement with industrial CT data: the maximum absolute deviation is 22 μm, the average absolute deviation is 15 μm, the maximum relative error is 1.09%, and the average relative error is 0.74%. The diameter and alignment deviation results of Φ0.5 mm micro-orifices show good consistency with the 3D coaxial line confocal sensor: the maximum absolute deviation is 13 μm for diameter and 0.047° for alignment deviation, with maximum relative errors of 2.41% and 0.058%, respectively. The alignment deviation results of 8 pairs of Φ2 mm orifices indicate that the proposed dual-line laser method is generally consistent with the combined pin gauge and CMM approach: the maximum absolute deviation is 0.170°, the average absolute deviation is 0.125%, the maximum relative error is 0.284%, and the average relative error is 0.125%. The results demonstrate that the proposed method enables non-contact and high-efficiency measurement of the diameter and alignment angle of injector orifices in impinging injectors for both conventional Φ2 mm orifices and micro Φ0.5 mm orifices, with high measurement accuracy and promising engineering application potential, thereby providing a new technical approach for the geometric parameter inspection of multi-scale micro-injection orifices.