The proton exchange membrane fuel cell (PEMFC) is a type of efficient and environmentally friendly battery. The structure of its bipolar plate directly affects reactant transport and liquid water removal and thereby affects the fuel cell performance. An improved three-partition trapezoidal baffle flow field based on the conventional trapezoidal baffle flow field design is proposed in this paper. A three-dimensional multiphase PEMFC model was established by considering the Forchheimer inertial effect. The mass-transfer characteristics and fuel cell performance of the improved three-partition baffle flow field were compared with those of the conventional parallel flow field and ordinary trapezoidal baffle flow field. It was observed that both improved three-partition baffle flow field and ordinary trapezoidal baffle flow field reduced the flow velocity near the baffle to enhance the inertial effect and mass transfer. In addition, improving the three-partition baffle flow field by further optimizing the baffle heights in different regions of the ordinary trapezoidal baffle flow field improved the transverse flow transmission and the inertial effect near the three-partition baffles. The water removal capability of the porous electrode and the PEMFC performance also improved. The net power of the improved three-partition baffle flow field increased by 4.8% compared with that of the conventional parallel flow field. This study provides an effective reference for the study of the PEMFC bipolar plate structure.

The increasing operation speed of high-speed trains allows the pantograph to continuously interact with the catenary over a long distance in a short time, and many new methods have been developed to efficiently calculate its dynamics. However, the existing methods only consider simple catenary systems, which limits their application in high-speed railway systems. In this work, a reduced pantograph–stitched-catenary interaction model is developed to simulate pantograph–stitched-catenary interactions during long-distance travel. Based on the existing reduced catenary model, the stitched catenary system is first considered, where the stitched wire is simplified into a part of the messenger wire supported by two spring-damping elements. The present model is validated by test results and the EN 50318:2018 standard, and it is subsequently used to study the dynamic performance of the pantograph–stitched-catenary system at an overdesigned speed in Sweden. The results show that the proposed model can be seven times faster than the traditional modal superposition method with the same accuracy in a stitched catenary system, and the existing catenary system cannot be operated at an overdesigned speed without increasing the contact wire tension. The present model gives an efficient solution to pantograph–stitched-catenary interaction problems.

The aim of this study is to design and analyze a variable compression ratio (VCR) technology gasoline engine variable compression ratio connecting rod set and to verify its kinematic properties through numerical simulations. This study first constructs a mathematical model of the VCR connecting rod set and derives its kinematic equations. Numerical simulations were carried out using MATLAB R2022b software to analyze the kinematic state of the piston under different compression ratio conditions. The results show that the equations of motion of the VCR mechanism realize continuously variable compression ratios from 8 to 14, which provides a valuable reference for the study of overall engine performance control. This study also verified the accuracy of the theoretical model through the multibody dynamics software ADAMS 2020 to ensure the reliability of the model. The results of this study show that the piston position is jointly influenced by the crankshaft angle and the control shaft angle, and a change in the control shaft angle leads to a change in the piston upper and lower stop positions and stroke. With the increase in the control shaft angle, the maximum velocity (absolute value) of the piston gradually decreases, while the maximum acceleration (absolute value) gradually increases. The results of this study provide important reference data for the development of variable compression ratio engines.