Selective laser melting (SLM) technology is widely utilized in various industries such as aerospace, engineering machinery, and medical sectors due to its benefits in lightweight construction, rapid manufacturing cycles, and design adaptability. However, reducing pipes produced via SLM often exhibit significant and irregular surface roughness, posing challenges in accurately predicting their local resistance coefficients using conventional hydrodynamic theories. Aiming at resolving this problem, the present study fabricates numerous Ti6Al4V reducing pipes with varying cone angles using SLM technology. The internal surface roughness distribution of these pipes is characterized and quantified. Through extensive experiments and numerical simulations, the local resistance coefficients of SLM reducing pipes are investigated, leading to the development of a novel prediction model. The study identifies several influencing factors on the local resistance coefficient, including cone angle, area ratio, Reynolds number, and surface roughness. It is observed that SLM reducing pipes encompass two distinct flow regions: the smooth region and the rough region, with the Reynolds numbers in the latter increasing with surface roughness. Moreover, a model incorporating critical values for both regions is established. The predicted local resistance coefficient model demonstrates a maximum error of only 10.96% when compared to experimental data, highlighting a substantial enhancement in prediction accuracy over traditional models.

Fluid–solid erosion wear may damage the port structure and change the linear characteristics of the spool valve. They may also affect null characteristics and the control accuracy of the valve, resulting in production and safety accidents. In the present study, the prediction model of the orifice throttling coefficient and worn profile for engineering applications such as compensation control and life degradation assessment is established. The collision probability between particles and the wall surface is particularly considered based on the E/CRC erosion wear model. The relationship between the spool opening and the impact angle of particles is investigated numerically when developing collision probability model. Meanwhile, the influence of particle concentration, spool opening, and differential pressure on the orifice throttling coefficient and worn profile is analyzed by experiments, and the microcosmic surface morphology of the spool metering edge is analyzed by scanning electron microscopy (SEM). The results show that the impacting of solid particles on the orifice will result in extrusion-thin platelets flaking wear and deformation wear. The maximum relative error between the predicted results and the experimental measurements is 2.25%. Moreover, the predicted results of the model are in good agreement with the measured values under different particle concentrations, spool openings and differential pressure.

Aerospace hydraulic integrated blocks, which are used as the connection carriers for hydraulic lines and components on aircraft, are currently mostly of block design and have great potential for weight reduction. Topology optimisation is a structural design method to achieve the best distribution of materials under a set load, which can effectively reduce the weight of the hydraulic block, but the result is generally irregular structure, which makes it difficult to achieve its processing using traditional manufacturing methods. With the development of AM technology, the machining of topologically optimised hydraulic integrated blocks has become possible. In this paper, we will take the small hydraulic integrated block with curved flow channel and the large hydraulic integrated block with complex structure as the research object, and design the topology optimisation idea of the integrated block with the goal of reducing the weight of the integrated block, and accordingly carry out the simulation using ABAQUS. The simulation results show that the topology optimisation can reduce the weight of the hydraulic integrated block studied in this paper by more than 50%, which is a significant contribution to reducing the weight and improving the performance of the aircraft.

Aircraft hydraulics pipelines is one of the most important components in aircraft hydraulics system. As a structure used for oil steering, the bent pipes are the most numerous components in the aircraft hydraulics pipelines. However, the local resistance of bent pipe is large, resulting in lower energy utilization. In order to reduce the local resistance of aircraft hydraulics bent pipes, this research proposes the design of guide vanes inside the aircraft hydraulic bent pipes. The velocity field and pressure field of bent pipes with guide vane are simulated and analyzed by COMSOL. The effects of the number, size, and position of the guide vanes on the local resistance are investigated. The simulation results show that two guide vanes can effectively reduce the local resistance of the bent pipe (diameter of 6–30 mm). For the bent pipe of common size (diameter of 10 mm), the position of the guide vane is presented to minimize the local resistance. The local resistance of bent pipes decreases as the thickness of the guide vane decreases. In addition, through the analysis of the pressure field of the hydraulic oil in bent pipes with guide vane, it is found that the guide vane effectively reduces the pressure gradient of the hydraulic oil at the bent pipe outlet. This research will effectively reduce the energy loss of hydraulic oil during transmission, and provide a reference for the design of aircraft hydraulics bent pipes.

Laser powder bed fusion (L-PBF) technology is an appropriate scheme for producing intricate components with complex internal structures, such as the intricate flow channel networks in aircraft hydraulic manifolds. However, it is an enormous challenge to fabricate circular channels without support structures that exhibit low shape deviation and high surface quality through L-PBF. This study introduces an innovative annular gradient-forming process that divides the circular flow channel into three sections, namely the inner layer, the transition layer, and the substrate, sequentially from the inside to the outside along the radial direction. Throughout the L-PBF process, the laser energy density is incrementally increased for the inner layer, transition layer, and substrate. The research focuses on manufacturing Ti6Al4V (TC4) circular channels with a diameter of 10 mm, exploring various process parameters to achieve low surface roughness, high dimensional accuracy, and low porosity through the annular gradient process. The effectiveness of the proposed annular gradient process and its parameters is validated through the fabrication and testing of circular channels with diameters of 8 mm, 10 mm, and 12 mm. The results demonstrate that the root mean square deviation (RMS) of the horizontal circular channels using the annular gradient process is reduced by over 80%, and the surface roughness Ra is reduced by over 50%. Furthermore, the channels also have better mechanical properties.

Laser powder bed fusion (L-PBF) technology offers significant advantages, such as lightweight and miniaturized product fabrication and short manufacturing cycles. Circular channels are widely utilized in hydraulic manifold blocks due to their favorable hydrodynamic properties. However, when manufactured using L-PBF, circular channels often exhibit shape deviations caused by residual stresses. In this study, Ti6Al4V (TC4) circular channels with various processing parameters were produced through L-PBF. The influence of scanning speed and laser power on the actual channel profile was investigated. A novel deformation prediction model for circular channels was established based on the Euler–Bernoulli theory. This model accurately predicts deformations resulting from residual stresses during horizontal manufacturing of circular channels using L-PBF, considering the interaction between forces and deformations across different manufactured layers. Furthermore, the model can be employed for channel shape compensation design. The results indicated excellent agreement between the proposed deformation prediction model and the profile of the experimentally manufactured samples. Using the channel shape compensation model for circular channels substantially can reduce the root mean square (RMS) deviation, thereby improving dimensional accuracy.

Electro-hydraulic proportional servo valve (EHPSV) is a typical precision hydraulic component, widely used in construction machinery, aircraft, ships and other important equipment. When the electro-hydraulic proportional servo valve is working, the pollution particles in the hydraulic oil will cause erosion and wear of the valve element and seriously affect the control precision of the valve. In addition, the hydraulic system is a typical nonlinear system, if the traditional PID controller is used for control, the control precision of the system can not be guaranteed. In this paper, the typical valve controlling cylinder system in hydraulic system is taken as the research object. An ARC controller is designed to control the system, and an erosion wear prediction model is established by finite element simulation to control the valve-controlled cylinder system with high-quality flow compensation under the ARC control architecture. In this paper, the modeling and simulation of valve controlling cylinder system are carried out by MATLB/Simulink. The results show that the adaptive robust controller with erosion wear prediction model can effectively improve the control precision of proportional servo valve.

Aviation hydraulic integrated block is an important part of aircraft hydraulic system, but its large volume, mass weight and internal pipeline pressure loss greatly limit the increase of hydraulic system power density ratio, is one of the components with the greatest weight reduction potential in aircraft hydraulic system. The application of AM technology can greatly improve the design freedom of aviation hydraulic integrated block. Proper design can not only reduce weight and volume, but also improve the internal fluid performance. In this paper, by means of COMSOL, finite element analysis and simulation are carried out on the velocity field and pressure field of circular turning pipe, continuous radius change pipe and B-spline curve pipe. In this paper, the influence of structural parameters of continuous radius change pipe and B-spline curve pipe on pressure loss is investigated in detail. The simulation results show that compared with the traditional machined transition pipe, the circular turning pipe, continuous radius change pipe and B-spline curve pipe can improve the flow performance of the internal fluid, and reasonable structural parameters can further reduce the pressure loss. This result lays a theoretical foundation for the structural optimization design of the internal flow path of the additive manufacturing hydraulic integrated block.