In response to the issues of low energy recovery efficiency, single- and low-capacity energy storage methods, and insufficiently diverse control strategies in hydrostatic transmission systems, this paper analyzes hydrostatic systems from the perspectives of hydraulic principles and control strategies. Hydrostatic transmission systems are divided into three types: pump-controlled hydraulic systems, secondary regulation hydraulic systems, and adaptive regulation systems. The design concepts and working principles of hydraulic systems are discussed, and the control strategies for hydrostatic transmission systems are categorized into torque control, fuzzy control, and optimal control strategies. Operating conditions are analyzed, and the advantages and disadvantages of traditional control strategies are compared. The results show that utilizing techniques such as adaptive regulation to reduce the loss of energy in the transfer process and in the transformation of secondary components, as well as combining a variety of methods for integrated control, can effectively improve the efficiency of these systems. The development direction of hydrostatic transmission systems is also discussed, including further development into oil–hydraulic hybrid systems, utilization of artificial intelligence technology and network technology, optimized design concepts, and the intelligence of hydrostatic transmission systems.

Hydraulic synchronous control systems are widely used in various industrial fields. This paper deeply analyzes the research status and development trend of the hydraulic synchronous control system. Firstly, it gives a brief introduction of the research significance control theory and control methods of the hydraulic synchronous control system. Secondly, the hydraulic synchronization control system is classified, the synchronization error is analyzed, and some solutions to synchronization error are given. Then, according to the classification of the hydraulic synchronous control system, relevant research is carried out. In this paper, three control modes (equivalent, master–slave and cross-coupling) and related control algorithms (fuzzy PID control, sliding mode control, robust control, machine learning control, neural network control, etc.) of closed-loop hydraulic synchronous control systems are studied in detail. Finally, the development trend of the hydraulic synchronization control system is predicted and prospected, which can provide some reference for promoting the research and application of hydraulic synchronization technology in the future industrial field.

This paper establishes a mathematical model of the high-pressure common rail injection system used in diesel engines according to the parameters of its key components, and AMESim 2020 software was used to establish a simulation model of the common rail injection system used in diesel engines. The simulation model mainly includes a high-pressure oil pump model, a common rail pipe model, and a model of four injectors. This paper also describes an experimental analysis of the accuracy of the established simulation model. Through a simulation analysis of the system rail’s pressure fluctuation and pressure characteristics, it was concluded that the length of the common rail pipe, the diameter of the common rail pipe, and the inner diameter of the high-pressure fuel pipes are important influencing parameters for the rail pressure characteristics of the system. In this study, according to the original common rail pipe and high-pressure fuel pipe model, a response surface methodology was used to optimize and analyze the parameters of the common rail pipe and high-pressure fuel pipes, and the optimal size parameters for the common rail pipe and high-pressure fuel pipes were obtained with the minimum rail pressure fluctuations and the average rail pressure setpoint. After the optimization, the pressure for the common rail pipe of the high-pressure common rail system was increased by 0.82%, the pressure fluctuation was reduced by 21.66%, the injection pressure was increased by 1.15%, the single injection volume was increased by 0.86%, and its fuel injection characteristics were significantly improved.

The damping groove structure of the port plate plays a crucial role in the pulsation suppression, vibration reduction, and noise optimization of the piston pump. Different damping groove structures have a significant impact on the flow distribution process during the normal operation of the port plate, affecting the pump outlet flow and pressure pulsations, which in turn influence the noise level of the piston pump. Therefore, the damping groove in the piston pump is one of the key structures influencing the pump’s pressure and cavitation behavior. To address the pressure shocks and oscillations caused by the distribution process in the piston pump, this study proposes a novel damping groove and performs CFD simulations on the non-damped groove. The analysis focuses on the pressure pulsation characteristics in the plunger chamber and the cavitation behavior of the pump. Additionally, an optimization analysis of the structural parameters of the new damping groove is conducted, which effectively reduces pressure shocks and cavitation in the swash plate axial piston pump. This study provides a theoretical foundation for improving the performance and lifespan of piston pumps.

The influence of the geometric parameters of the common rail pipe on the in-rail fuel flow and pressure is a key issue in the study of high-pressure common rail systems. In this study, based on the principle of fluid dynamics, the effects of the geometric parameters of the common rail pipe inlet on the fuel flow characteristics and pressure distribution in the common rail pipe are analyzed using a combination of numerical simulation and experiment. It was found that the best pressure stabilization was achieved when the fuel inlet was conical with an angle of 120°, which indicates that both the geometry and angle of the fuel inlet have a significant effect on the fuel flow in the common rail pipe. The optimized design in this study has reduced the rail pressure fluctuation value by 3.3 MPa compared to the initial geometry parameters. It is expected to play a role in improving fuel efficiency as well as enhancing system reliability.