The Effect of Sand Erosion on a Compressor Blade and its Modal Properties

The wear and damage of High-Pressure Compressor (HPC) blades due to erosion or Foreign Object Damage (FOD) have a significant influence on HPC aerodynamic performance, vibration resistance against High-Cycle Fatigue (HCF) and thus component lifetime. The changes in airfoil geometry reduce the overall engine efficiency. Furthermore extended off-wing engine maintenances due to blade failures are increasing the cost of ownership. The safe operation of every engine within a reduced number of shop visits requires a reliable prediction of future deterioration. This enables the optimization of services and off-wing time. One contribution to this is a better understanding of the component’s dynamics and based on this providing an improved wear modeling to reliably predict the remaining lifetime and the decreased efficiency. This contribution determines the material removal of HPC blades due to sand erosion. Originally, this stage was built as a blisk (Blade Integrated Disk). After sand erosion test completion, the blisk was cut into segments containing one airfoil only. First, the material removal is determined for ten blades of one exemplary rotor. A blue light fringe projector is employed to identify the geometrical differences between the eroded blades and the nominal design. Second, realistic finite element models are generated to enable comparable modal analyses of eroded blades. This procedure suffers from unavoidable and mostly random imperfections due to the manufacturing process, which significantly affects the blade surface before the erosion test can be conducted. Therefore, an already published approach is implemented in the third step to predict the blade surface after erosion based on nominal blade design. The investigation is completed by comparing measured and predicted surfaces. Finally, the aforementioned tool is employed to predict the locations and intensities of the material losses and the accompanying change in modal properties of this compressor blade concerning operational time.

An optimization study of polishing efficiency of blisk and its technological parameters

When applied to blisk blade profile polishing of aero-engines, “five-axis NC + flexible grinding head + elastic grindstone” polishing technological equipment has advantages of high precision, minor interference, favorable adaptivity, etc. In order to improve the polishing quality and polishing efficiency, a mathematical calculation formula of polishing efficiency was established according to the polishing principles of elastic grindstone (sanding wheel). The optimized combination of technological parameters ( ω = 6000 r/min, ap = 0.9 mm, vf = 320 mm/min) was obtained through the range method of orthogonal test results with double optimization objectives—surface roughness and polishing efficiency. Based on the relationship between number of polishing times and surface roughness, a technological program was put forward, that is, polishing is firstly conducted using 320# sanding wheel for 6 times and then 400# sanding wheel for 9 times (totally 15 times) under the optimized combination of technological parameters, then surface roughness less 0.4 μm can be achieved. Blade polishing test results indicate that: efficiency-optimized technological parameters can not only significantly shorten polishing time but also acquire qualified blade surface roughness less 0.4 μm, thus verifying reliability of the optimization method and results.

ENHANCED MATERIAL REMOVAL RATE AND SURFACE QUALITY IN Ti-6Al-4V BLISK BLADE POLISHING BY GRA-RBF-FA METHOD

As an efficient and fast developing surface finishing technique, polishing processes have been widely used in the machining of aero-engine blisk blade. Since a number of processing input variables will influence surface quality and production time, controlling surface finish and machining efficiency require a carefully designed combination of various processing parameters. Therefore, this paper presented a comprehensive multi-objective parameter optimization method that integrates grey relational analysis (GRA), radial basis function (RBF), as well as firefly algorithm (FA). The purpose is to simultaneously obtain the optimal parameter combination for minimum surface roughness and the greatest material removal rate by optimizing rotational speed, feed rate and polishing force in Ti-6Al-4V blisk blade polishing. The hybrid experiments were carried out by combining the orthogonal experimental design with the single-factor experimental design. GRA was run for converting multi-objective response into the single-objective response. Then, RBF was applied to build the relationship between the grey correlation degree and the control variables. Finally, FA was utilized to obtain the optimal grey correlation degree in the range of control variables. The verification tests showed the highest material removal rate of 5.370[Formula: see text]mm2/s and surface quality of 0.374[Formula: see text][Formula: see text]m have been successfully achieved.