In the fields of agriculture, medical treatment, food, and packaging, polymers are required to have the characteristics of self-cleaning, anti-icing, and anti-corrosion. The traditional preparation method of hydrophobic coatings is costly and the process is complex, which has special requirements on the surface of the part. In this study, fused deposition modeling (FDM) 3D printing technology with design and processing flexibility was applied to the preparation of hydrophobic coatings on polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) parts, and the relationship between the printing process parameters and the surface roughness and wettability of the printed test parts was discussed. The experimental results show that the layer thickness and filling method have a significant effect on the surface roughness of the 3D-printed parts, while the printing speed has no effect on the surface roughness. The orthogonal experiment analysis method was used to perform the wettability experiment analysis, and the optimal preparation process parameters were found to be a layer thickness of 0.25 mm, the Grid filling method, and a printing speed of 150 mm/s.

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Fouling is the most important performance degradation factor, so it is necessary to accurately predict the effect of fouling on engine performance. In the previous research, it is very difficult to accurately model the fouled axial flow compressor. This paper develops a new performance calculation method of fouled multistage axial flow compressor based on experiment result and operating data. For multistage compressor, the whole compressor is decomposed into two sections. The first section includes the first 50% stages which reflect the fouling level, and the second section includes the last 50% stages which are viewed as the clean stage because of less deposits. In this model, the performance of the first section is obtained by combining scaling law method and linear progression model with traditional stage stacking method; simultaneously ambient conditions and engine configurations are considered. On the other hand, the performance of the second section is calculated by averaged infinitesimal stage method which is based on Reynolds' law of similarity. Finally, the model is successfully applied to predict the 8-stage axial flow compressor and 16-stage LM2500-30 compressor. The change of thermodynamic parameters such as pressure ratio, efficiency with the operating time, and stage number is analyzed in detail.

Particles contained in air can deposit on the blade surface to cause fouling when lubricating oil and water steam are existed. Fouling changes blade geometry and blade surface roughness is increased, thus aerodynamic performance is affected. Many researchers simulated axial flow compressor fouling by adding constant surface roughness and modifying blade thickness which can’t reflect the real status of fouled compressor. In this paper, reverse technology is introduced to reconstruct the solid model of fouled compressor which is imported into fluid flow simulation software. The flow of gas phase and gas-solid coupling phase are implemented to reveal the nature of flow in fouled axial flow compressor. Based on Euler-Lagrange model, this paper made numerical simulation of gas-solid two phase flow in the axial flow compressor rotor cascade. Simulation result shows that fouling causes the decrease of effective flow area, thus thermodynamic performance is degraded. Gas-solid phase flow shows that particles are not uniformly deposited on the blade surface. When particle is smaller and rotor blade is rough, it is more easily deposited on the surface. And particle mass concentration is affected by ambient conditions such as inlet temperature, rotational speed, particle diameter, particle mass flow rate.