In the turbine blade fractal cooling channels, developing shaped fractal units based on mass flow distribution is crucial for enhancing the cooling effect. Detailed analyses of flow and heat transfer in typical shaped fractal units are conducted in this study, and the performance differences of fractal plates with different shaped units are compared. Additionally, a fully automatic topology optimization process is developed to achieve fractal units' mass flow adjustment and performance optimization. It is indicated that the sensitivity of pressure loss in shaped fractal units to the position of typical control points is significantly higher than that of cooling effects. Within the same range of movement, maximum and minimum pressure losses differ by 279.2%, while cooling effects vary by only 7.3%. Outlet flow uniformity is significantly improved by adding branches to multi-entrance units. When optimization parameters target values are known, such as outlet flow distribution, the gradient descent method can be employed in the automatic optimization process. In contrast, for unknown parameters like minimum pressure loss, accuracy is significantly enhanced through the use of particle swarm optimization. The cooling air across different regions is redistributed by the shaped unit arrangement, thereby improving the fractal plate thermal uniformity.

Permanent magnet synchronous arc motor (PMSAM) can directly output arc motion. Compared to the combination of rotary motor and transmission mechanism, it exhibits advantages such as compact volume and simplified structure, making it more suitable for applications in electric actuators. The high torque density requirements pose challenges to its thermal characteristics. Based on additive manufacturing (AM) technology, this paper proposes a fully-covered direct cooling AM cooling channel to achieve efficient thermal management of the AM-winding PMSAM. The accuracy of the calculations is ensured through anisotropic thermal parameter modeling. A radially variable-height design is employed to balance the radial temperature distribution. A double-layer parallel channel layout is adopted, which eliminates cooling dead zones at the ends while maintaining low pressure loss. The AM cooling channel design significantly increases the electrical loading of PMSAM, and provides experience for improving the thermal characteristics of PMSAM applications in electric actuator system.

As additive manufacturing (AM) technologies rapidly advance, their application in fabricating structural components for motors has received significant attention. This paper presents the design of two concentrated winding structures with variable cross-sectional shapes based on AM, which can significantly improve the slot fill factor. Achieving a high slot fill factor significantly enhances the motor's output torque. However, AM windings exhibit increased sensitivity to frequency variations, leading to higher winding losses. An analysis of the loss distribution in AM windings reveals that losses primarily concentrate in the conductors near the slot opening. To minimize these losses, this paper proposes a loss suppression strategy for AM windings that does not compromise the slot fill factor. The optimized windings demonstrate a 26.5% reduction in losses and a 13% decrease in winding temperature. Finally, two distinct prototypes are developed: one utilizing AM windings and the other conventional windings. Both prototypes are tested to assess their electromagnetic and thermal performance.

Metal additive manufacturing (AM) technology enables the design of advanced winding structures for coreless permanent magnet synchronous linear motors (PMSLMs), addressing the challenges, such as low magnetic loading and excessive heating, but the exposure to the magnetic field leads to significant eddy currents. This article presents an overlapping winding configuration using tangentially arranged flat conductors. It is designed to enhance electrical load capacity while minimizing induced eddy currents and reducing the end volume. The models for eddy current and output thrust are developed to quantitatively analyze the electromagnetic and loss characteristics. The structure of end winding and finite eddy current circuit is considered. By incorporating eddy current effect into the motor constant and thrust density, the key geometrical parameters of the AM winding are analyzed. The design criteria for these winding parameters to achieve optimal performance are established. The validity of the analytical model is verified through finite element analysis and testing on a PMSLM prototype with AM overlapping winding.

Additive manufacturing (AM) enables advanced winding geometries with improved electromagnetic properties, making it well suited for coreless motor applications. Understanding the loss mechanisms and thermal behavior of AM windings is critical for reliable motor operation. This paper investigates the relationship between winding loss, conductivity, and frequency in coreless permanent magnet synchronous linear motors (PMSLMs). An anisotropic equivalent thermal conductivity model for rectangular conductors is developed based on heat-flow distribution. Analytical expressions are derived from key winding parameters and validated through finite element method (FEM). A three-dimensional FEM thermal model is established to analyze winding thermal behavior. It considers structural dimensions, operating conditions, material properties, and high ampere-turns scenarios. The results demonstrate that AM windings significantly improve thermal performance, enabling a 10.8 % increase in ampere-turns capacity and a 34.2 % improvement in thrust density for coreless PMSLMs. Finally, AM winding samples and a motor prototype are fabricated. Experimental results confirm the simulation.

The demand for arc motion in the field of intelligent machining is increasingly growing. The permanent magnet synchronous arc motor (PMSAM) can directly output arc motion, offering significant advantages over traditional structures. High-end equipment manufacturing imposes increasingly stringent requirements on the torque ripple and torque density of PMSAMs. This paper proposes a PMSAM with a variable-arc armature core. By adjusting the core’s arc on the inner and outer diameter sides, the end torques at different radii cancel each other out. Compared with conventional methods such as adding end teeth, this approach achieves comparable suppression effects while reducing core weight. The variable-arc design creates a skewing effect between the teeth and permanent magnets, further reducing the cogging torque. Additionally, an additively manufactured (AM) lightweight core, designed with consideration of magnetic flux density distribution characteristics, is developed to further enhance torque density. This study provides experience for the design of the intelligent manufacturing systems.

This paper proposes a double-sided consequent-pole permanent magnet synchronous linear motor (DS-CP-PMSLM) with interleaved permanent magnets (PMs). It can adjust the detent force period and symmetry, as well as suppress even harmonics of the back electromotive force (EMF). By designing the PM (w(PM)) and iron pole (w(IP)) with unequal widths and optimizing the alpha coefficient (alpha(1)=w(PM)/tau, alpha(2)=w(IP)/tau) to adjust the sine of the detent force, combined with optimizing the length of the primary iron core, it is possible to suppress the detent force and thrust ripple. In order to obtain a DS-CP-PMSLM with interleaved PMs outputing greater thrust, the primary can be expanded from a single module to two or more modules. Modular optimization and resting winding phase can be used to minimize thrust ripple and maximize average thrust.

The transient turbine tip clearance (delta) throughout the engine process is crucial to modern high-performance aero engines. However, there is still a lack of efficient and accurate transient prediction models of tip clearances with active thermal control (ATC) system, especially for the tip clearances of the complex turbine structures with various parameters. This study develops a transient prediction model for the tradeoff between computational efficiency and accuracy, which includes an offline dataset generation process and an online delta prediction process. The offline dataset is first generated using an in-house finite element analysis code, which is validated against a transient tip clearance experiment, and data splicing and sensitivity analysis are applied to enrich the sample features and reduce the input parameters' dimensionality. Then, the long short-term memory neural network (LSTM) is employed to learn the transient tip clearances' timing information. The time consumption for the transient prediction model is significantly shorter than that for the tip clearance calculation method by three orders, and the maximum relative error is as low as 3.59%. In addition, the transient characteristics, including the overshoot value (sigma) and the response time (t(s)), are investigated with different jet Reynolds numbers (Re-c) and temperatures (T-fc) of ATC cooling flow. The ts decreases with larger Rec and smaller T-fc due to a more significant cooling effect. However, the sigma increases with the increase of Rec and Tfc due to the different sensitivity of cooling parameters. This study provides a reference for the transient tip clearance prediction and the adjustments in the cooling strategies.

Room temperature grown Fe monolayer (ML) on the Ir(111) single crystal substrate has attracted great research interests as nano-skyrmion lattice can form under proper growth conditions. The formation of the nanoscale skyrmion, however, appears to be greatly affected by the diffusion length of the Fe adatoms on the Ir(111) surface. We made this observation by employing spin-polarized scanning tunneling microscopy to study skyrmion formation upon systematically changing the impurity density on the substrate surface prior to Fe deposition. Since the substrate surface impurities serve as pinning centers for Fe adatoms, the eventual size and shape of the Fe islands exhibit a direct correlation with the impurity density, which in turn determines whether skyrmion can be formed. Our observation indicates that skyrmion only forms when the impurity density is below 0.006/nm2, i.e., 12 nm averaged spacing between the neighboring defects. We verify the significance of Fe diffusion length by growing Fe on clean Ir(111) substrate at low temperature of 30 K, where no skyrmion was observed to form. Our findings signify the importance of diffusion of Fe atoms on the Ir(111) substrate, which affects the size, shape and lattice perfection of the Fe islands and thus the formation of skyrmion lattice.

Magnetic ultrathin films grown on heavy metal substrates often exhibit rich spin structures due to the competition between various magnetic interactions such as Heisenberg exchange, Dzyaloshinskii-Moriya interaction and higher-order spin interactions. Here we employ spin-polarized scanning tunneling microscopy to study magnetic nano-skyrmion phase in Fe monolayer grown on Ir(111) substrate. Our observations show that the formation of nano-skyrmion lattice in the Fe/Ir(111) system depends sensitively on the growth conditions and various non-skyrmion spin states can be formed. Remarkably, the application of voltage pulses between the tip and the sample can trigger a non-skyrmion to skyrmion phase transition. The fact that nano-skyrmions can be created using voltage pulse indicates that the balance between the competing magnetic interactions can be affected by an external electric field, which is highly useful to design skyrmion-based spintronic devices with low energy consumption.

This paper developed a process for turbine tip clearance prediction and control considering performance degradation to address the contradiction between computational efficiency and computational accuracy. The developed process consists of an offline high-accuracy database establishment for tip clearance with performance degradation and an online fast tip clearance prediction and control using machine learning. For the former, the steady-state tip clearance is obtained by the calculations for the two-dimensional axisymmetric casing and disk deformations using the finite element method and the one-dimensional blade deformation using the engineering calculation method. The effects of performance degradation, including blade creep and turbine inlet temperature degradation are introduced to update the boundary conditions in gas path and initial clearance. For the latter, the multilayer perceptron is used to realize the fast tip clearance prediction. Considering the independence of component deformations, the tip clearance prediction is achieved by the component deformation predictions, which also reduces the dimension of input parameters for each prediction model and improves the prediction accuracy. Combining the above two parts, the tip clearance with performance degradation can be obtained within 0.00025 s/time, and the maximum absolute error is only 0.012 mm. In addition, with the help of the process, the optimized tip clearance control strategy can be obtained for the performance degradation states, which restores the tip clearance with a 17.66% increment to the initial state without performance degradation. This paper will provide a reference for the tip clearance prediction and control with small computation and high accuracy.

Improving transpiration cooling performance is a challenge to meet the requirements for the cooling perfor- mance and thermal stress restrict. In the current study, numerical simulations are carried out to investigate the transpiration cooling performance with different porosity configurations and mainstream pressure gradients. Eight porosity configurations, three mainstream pressure gradients, and three injection ratios are considered. Cooling effectiveness distributions and cooling effectiveness uniformities are evaluated. Velocity distributions and coolant allocations are also studied to reveal the cooling mechanism. Results show that all the transpiration cooling cases gain higher cooling effectiveness than the film cooling cases, and the maximum enhancement reaches up to 100%. However, the transpiration cooling cases have non-uniformity distributions of cooling effectiveness due to the uneven coolant allocations caused by the superposition effects. For uniform porosity configuration cases, the cooling effectiveness increases monotonically with the increasing porosity due to the enhanced external coolant coverage, whereas the uniformity of cooling effectiveness decreases due to the more uneven coolant allocation distribution along the mainstream direction, especially for the configurations with large porosity. In addition, when streamwise pressure gradients exist in the mainstream, only the TC-3 case with a small uniform porosity and the TC-8 case with a streamwise decreasing porosity perform better robustness. Among them, the TC-8 case gains obvious advantages in engineering applications due to the highest cooling effectiveness and the smallest non-uniformity, which is caused by the better coolant coverage and more uniform coolant allocation.

With the rapid development of additive manufacturing (AM), applying this technology to the fabrication of structural components for motors has received widespread attention. The low slot fill factor and low thermal conductivity of traditionally-manufactured windings prevent further improvements of motor performance. Therefore, this paper proposes two concentrated winding structures with variable cross-sectional area based on AM that can significantly improve the slot fill factor. The realisation of high slot fill factor greatly improves the output performance of the motor. However, the design of the variable cross-sectional area also increases the sensitivity of the winding losses to frequency variations. On this basis, the temperature rise modelling method and temperature rise distribution of AM windings are discussed, taking into account the special structure of AM windings. The above characteristics have also been compared with traditional windings.

Vortex generators (VGs), as novel measures for suppressing a crossflow, have been used for the promotion of jet impingement heat transfer. In this study, to explore more VGs' benefits, numerical simulations are investigated for the comparisons of a jet in crossflow with four VGs, considering the heat transfer performances and the flow interaction mechanisms. VGs with common-flow-up or common-flow-down configurations are arranged in the upstream or downstream of the jet hole. Parameter studies are carried out by varying the crossflow-to-jet ratio from 0.19 to 0.32, VG heights from 1/8H to 1/2H (H is the jet-to-wall distance), and spacings between the jet and the VGs from 0d to 2d (d is the jet hole diameter). Results show that a new VGs with downstream common-flow-down configuration (DCFD) is obtained with favorable enhancement of heat transfer, which is competitive to the upstream common-flow-up configuration (UCFU) studied in previous work. With the DCFD configuration, the extrusion of the counter rotating vortex pair is caused by a recirculation region generated behind the jet, which gives more blockage to the crossflow. In addition, the heat transfer for the DCFD case is promoted with the increasing height of the VGs, and decreasing the spacing between the VGs and the jet. The maximum enhancement in area averaged Nusselt number for DCFD case can reach up to 69.7% with a small increase in the friction coefficient of lower than 10%. This study will present much more possibilities for the heat transfer enhancement in more complex system, such as jet array system and nonuniform crossflow system.

In the jets array cooling system of the gas turbine, the downstream jets will be deflected by the crossflow and the heat transfer in the downstream will be suppressed. In this paper, the rectangular vortex generators are arranged in the jet arrays to enhance the jet impingement heat transfer. Through the numerical simulations, the configuration of rectangular vortex generators (Common-flow-down CFD and Common-flow-up CFU) and the relative position (l2) between the impingements and the rectangular vortex generators are studied. The results show that both of configurations are beneficial to the suppression of the crossflow and enhance the heat transfer in the downstream. The maximum enhancement of the whole regional average Nusselt numbers in CFD-VGs configuration can reach up to 9.09% with lower than 5% increase of the pressure loss and that in CFU-VGs configuration can reach up to 10.8% with lower than 4.8% increase of the pressure loss. From the perspective of the whole regional average Nusselt numbers and the overall thermal efficiency, the CFD-VGs with l2 = 0 has the best performance. However, from the perspective of the whole regional average Nusselt numbers, the CFU-VGs with l2 = 0 has the best performance, while from the perspective of the overall thermal efficiency, the CFU-VGs with l2 = 3 has the best performance.

A small transonic centrifugal compressor with 3D vaned diffuser has been developed for a turbine engine by Nanjing University of Aeronautics and Astronautics. The centrifugal impeller's' diameter is approximately 80 mm. The impeller was improved by reducing the static pressure gradient in spanwise direction. But the improvement is reduced by the interaction between the impeller and the diffuser, when it works with the diffuser. So, the effect of the vaned diffuser on the performance and flow structure of the impeller was studied by steady and unsteady numerical simulations.The total pressure ratio and efficiency of the impeller with a vaned diffuser are lower than those with a vaneless diffuser. Further, the difference decreases as the operation point moves from the surge to the choke. Analysis of steady flow proves that the meridional bend and the vanes in the 3D vaned diffuser are the main causes. When the impeller operates with the vaned diffuser, the vortex at the shroud of the impeller exit is pushed toward the trailing edge of the impeller blade, which leads to an altered flow structure in the impeller passages. As a result, the loss of the impeller increases, and consequently the efficiency as well as the pressure ratio drops. On the other hand, the unsteady analysis shows that the flow pattern at the impeller exit is circularly affected by features of the stagnation, the local acceleration, and the shock wave in the semi-vaneless space of the diffuser. The flow at the different spanwise location in the trailing edge of the impeller blade can be influenced by the different flow feature, therefore, the spanwise distributions of the flow parameters is disturbed.