Harbin Foresty Machinery Institute

ABSTRACT Lower thermal stability class and thermal conductivity ( λ ) of mica tape limit the service life of stator winding insulation in large generators. A novel mica tape composite was prepared by replacing epoxy resin with heat‐resistant polyesterimine and incorporating hexagonal boron nitride (h‐BN) filler, mica paper, and glass fiber cloth, which can overcome the thermal stability and λ of epoxy tapes, with a multiscale model established for performance prediction. The experimental results demonstrate that the h‐BN‐modified polyesterimine resin mica tape exhibits a heat‐resistant class of H. At an h‐BN loading of 25 wt%, the λ of the h‐BN‐modified polyesterimine resin mica tape attains 0.497 W/(m K), representing a 116.09% enhancement compared to the polyesterimine resin mica tape (0.23 W/(m K)). Through integration of the Y. Agari and Series model, a second‐order thermal conductivity model (Y–S) was developed for h‐BN‐modified polyesterimine resin mica tape composites, demonstrating enhanced accuracy in predicting λ . Furthermore, the h‐BN‐modified polyesterimine resin mica tape composites prepared in this paper exhibit excellent dielectric properties, with a material insulation strength of > 30 kV/mm. This provides a new approach for the preparation of mica tape composites with high heat‐resistance class and high thermal conductivity.

Turbogenerators are crucial equipment in power generation. Unreasonable design of the end of such generators can lead increased end losses that can impact the safety and stability of the system in operation. In this study, a 350-MW novel double-side counter-flow large turbogenerator is proposed. A three-dimensional transient nonlinear electromagnetic field model of the end region of the turbogenerator is established to analyze the electromagnetic field. In order to reduce the losses of end components, the novel structural optimization design is proposed. The influence of the modified end structure on the flux density of the end components is investigated by varying the relative lengths of the stator and rotor cores and the distances between the copper screen and windings. The losses of the end components are obtained under different end structures. The results show that a reasonable relative length between the stator and rotor cores and distance between the copper screen and winding effectively reduced losses from end components in the proposed design. The results of the calculation are verified experimentally. Thus, this study provides an important reference for the optimization of the end structures of turbogenerators.

The automatic classification of tree species using terrestrial laser scanning (TLS) point clouds is key in forestry research. This study aims to develop a robust framework for tree species classification by integrating advanced feature extraction and machine learning techniques. Such a framework is of great significance for investigating and monitoring forest resources, sustainable forest management, and biodiversity research. To achieve this, point cloud data from 360 trees of four species were collected at the Northeastern Forestry University in Harbin City, Heilongjiang Province. Three types of tree point cloud features were extracted: tree structure, bark texture, and bark color. In addition, to repair and optimize the bark point cloud data, improved bark texture features were generated using the kriging interpolation method. These four features were combined into seven classification schemes and input into a random forest classifier, which was used to accurately classify the tree species. The results showed that the classification scheme combining tree structure features, improved bark texture features, and bark color features performed the best, with an overall classification accuracy of 94.17% and a kappa coefficient of 0.92. This study highlights the effectiveness of integrating point cloud data with machine learning algorithms for tree species classification and proposes a feature extraction and classification framework that significantly enhances classification accuracy.

Abstract Recently, the development trend of large capacity generator has gradually shifted from electrical excitation generator to permanent magnet generator (PMG). As a result, the large capacity high‐speed permanent magnet generator (HSPMG) with high power density and high efficiency have received widespread attention. This paper aims to analyse the loss optimization of novel large capacity HSPMG under multi‐operating conditions. In terms of the parameter requirements, a 2.5 MW and 7000 rpm HSPMG is designed. To verify the accuracy of simulation model and the rationality of generator design, the output characteristics of large capacity HSPMG which has been combined with prototype experimental data are calculated under both no‐load and load conditions. Based on the load power characteristics of large capacity HSPMG, the optimization range of the magnetization angle under multi‐operating conditions is explored. By analysing the no‐load back electromotive force (EMF) and loss characteristics of large capacity HSPMG, the optimal magnetization angle that corresponds to the minimum loss under three conditions is obtained. The correctness of the analysis and optimization method is verified by comparing the loss distribution and electromagnetic results before and after the optimization. The research results provide a reference for the multi‐operating characteristics analysis and loss optimization of large capacity HSPMG.

To improve the utilization rate of fertilizers, realize the precise spreading of fertilizers in controllable strips, and ensure the uniformity of fertilizer spreading in both longitudinal and transversal directions, a bifurcated swing tube fertilizer spreading device driven by a spatial hammer pendulum crank mechanism was designed. First, the drive mechanism was designed based on the cylindrical pair of the mechanism. A mathematical model pendulum equation was used to design the swing tube, and the equation of motion of fertilizer particles was established by analyzing the motion and force of fertilizer particles in fertilizer spreading. The dynamic parameters of the fertilizer spreading device (nozzle height, forward velocity, and swing frequency) were identified as the test factors affecting the uniformity of fertilizer spreading. Second, the coupling model based on MBD-DEM was established, and the coupling simulation analysis of the fertilizer spreading process was carried out using EDEM-RecurDyn software. Taking the nozzle height, forward velocity, and swing frequency as test factors and the uniformity coefficient of longitudinal and transversal fertilizer spreading as evaluation indexes of the fertilizer discharging effect, we analyzed the influence of a single factor on the indexes. Moreover, the ternary quadratic generalized rotating combination response surface test established the regression equations of three factors and two evaluation indexes. Finally, the simulation and bench test were verified under the optimal combination of parameters and compared with the single swing tube bench test with the same parameter conditions. The results of the single-factor test showed that the fertilizer discharge effect was better when the nozzle height was 350.0-450.0 mm, the forward velocity was 0.5-1.5 m/s, and the swing frequency was 1.40-2.00 Hz. The results of the response surface test proved that the nozzle height, forward velocity, and swing frequency all had a highly significant effect on the uniformity coefficient of fertilizer spreading in the longitudinal and transversal directions (P<0.01). Moreover, the optimization concluded that when the nozzle height is 450.0 mm, the forward velocity is 0.5-0.8 m/s, and when the swing frequency is within the range of 1.40-2.00 Hz, the uniformity coefficient of longitudinal fertilizer spreading is ≤25% and the uniformity coefficient of transversal fertilizer spreading is ≤45%. The results of bench validation showed that the errors of longitudinal and transversal fertilizer spreading uniformity coefficients in the bench test were 3.46% and 1.44%, respectively, and the simulation agreed with the bench test. The results of comparative tests showed that the uniformity coefficient of the longitudinal and transversal of the fertilizer spreading device was reduced by 50.33% and 14.95%, respectively, for the bifurcated swing tube compared with that of the single swing tube. It is proved that the bifurcated swing tube strip fertilizer spreading device can achieve the purpose of uniform fertilizer spreading and performs better than the single swing tube in fertilizer spreading. The results and methods of this study can provide a reference for the design of swing tube strip fertilizer spreading devices and related fertilizer spreading performance tests.

Abstract The S shaped characteristics of pump-turbines have an important impact on the minimum pressure of draft tube. The quality of the S shaped characteristics is one of the key indicators to determine the success of model runner development, and this indicator is particularly important for ultra-high head pump-turbines. In order to delve deeper into the inherent relationship between the S-shaped characteristics of the runner and the optimization design and minimum pressure of draft tube, this article first defines a method for fixed-point quantitative analysis of the S shaped characteristic curve. Then, different experimental characteristic curves obtained from multiple optimized designs of the runner are used to calculate the hydraulic transition process. At the same time, the S shaped curve is quantitatively analyzed, and the relationship between the three is explored through continuous analysis. The results show that the bending degree of the equal opening lines in the middle at the S shape characteristics curves has the greatest influence on the minimum pressure at the draft tube inlet. The greater the ratio of unit flow difference to unit speed difference in the S shape characteristics curves of the equal opening line, the greater the runaway unit flow on the same equal opening line, the more favorable it is to increase the minimum pressure at the inlet of the draft tube. The optimal design of blade type and guide vane airfoil can improve the minimum pressure value of draft tube to a certain extent. The conclusions obtained in this paper can be used for reference in the research and development design of high head pump-turbine runner and the optimization calculation of transition.

In order to improve the performance of garbage collection truck manipulators, a three-dimensional model of the garbage collection truck manipulator is established based on SolidWorks. The dynamic analysis of the garbage collection truck manipulator model is carried out using the ADAMS software according to its movement in different working conditions, obtaining the displacement, force, and speed curves. The model is identical to garbage collection truck manipulators used in real situations. The static characteristics of the garbage collection truck manipulator model are analyzed in HyperWorks, which provides the conditions for the subsequent optimization. Finally, based on parametric modeling, taking the volume minimum as the goa, keeping the deformation and stress to meet the requirements for use as constraints, a genetic algorithm is used to optimize the weight of the manipulator. The optimization results show that the mass of the manipulator can be reduced by 17 kg (16.73%) while the strength meets the requirements.