The wave compensation system of offshore trestle can realize the safe and efficient transfer of personnel and materials at sea, and is the key system of large marine operation and maintenance ships. Aiming at the bottleneck problem of high energy consumption in the wave compensation system of offshore trestle, a design scheme of active- passive composite wave compensation electro-hydraulic system for pitching joint of offshore trestle is proposed in this paper. Firstly, this paper analyzes the mechanical structure of the wave compensation system and its working principle of the pitching joint. A passive wave compensation system based on high-pressure gas follow-up support is designed to reduce the energy consumption caused by gravity during the pitching action of offshore trestle. An active wave compensation hydraulic control system based on electro-hydraulic valve group is designed to realize the closed-loop control of pitching motion of offshore trestle. Then, through theoretical modeling and simulation analysis, the mechanism of the designed system to compensate the trestle's dead load is revealed, the energy distribution of the passive compensation system and the active compensation system is analyzed, and the energy consumption characteristics of the designed active-passive composite wave compensation electro-hydraulic system under different passive compensation pressures are explored. Finally, the active-passive composite wave compensation electro-hydraulic system for pitching joint of offshore trestle is developed, and the driving and control capability of the designed system is verified by experiments. The results show that the designed active-passive composite wave compensation electro-hydraulic system can realize the low energy consumption and high precision control of the offshore trestle, which has important strategic significance for the future installation, operation and maintenance of offshore wind power in China.

Aiming at the high performance design of end face structure for spiral groove mechanical seals with liquid film lubrication, the entropy production loss method was adopted to carry out the numerical calculation of the three-dimensional turbulence flow field and groove optimization design of spiral groove mechanical seal; The pressure distribution of flow fields with different grooves were analyzed; The leakage rate, opening force and entropy production loss of the seal at different speed and groove depth conditions were calculated. The results show that the optimal spiral angle, groove-ridge ratio, groove-dam ratio and groove depth is 20°, 0.42, 0.63 and 13 μm, respectively; the optimal seal end face dynamic pressure opening ability is large, and the flow entropy production loss is small; The leakage rate and opening force increase linearly with the rotational speed and groove depth, the entropy production loss increases parabolically with the rotational speed and vary little with groove depth. The multi-objective optimization design method constructed can provide design guidance for low leakage, and low-energy mechanical seal structures.

In this paper, the finite element model of metal C-type seal ring is established through the finite element analysis software ABAQUS, and the main influencing factors and variation rules of compression recovery performance of C-type seal ring are obtained, which are compared with the test results. The effects of alloy layer thickness, opening size, material and temperature on the mechanical properties of metal C-type seal ring were studied, and the suitable deformation range, contact width and contact stress were obtained. The mechanical properties of metal C-type seal ring under self tightening and non self tightening installation modes are studied. It shows that self tightening installation has better mechanical properties, while non self tightening installation has little effect on mechanical properties.

This article introduces the structure and working principle of a fixed value pressure reducing valve used in a certain type of axial piston variable displacement motor, and theoretically calculates its structural parameters. The static and dynamic characteristics of the constant pressure reducing valve were analyzed, and a simulation model of the constant pressure reducing valve was built using AMESim software. The influence of the damping equivalent diameter of the constant pressure reducing valve on the pressure building process, delay time, and start stop process of the Br chamber was specifically discussed, and experimental verification was carried out, providing theoretical guidance for the subsequent design improvement and mass production of the constant pressure reducing valve.

Electro-hydraulic servo valve is the core control element in high-precision deep-sea hydraulic equipment, and its performance and reliability are the key factors to determine the control accuracy and reliability of deep-sea hydraulic system. Under the extreme working conditions of the deep sea, the tiny deformation of the valve spool and the valve sleeve affects the control performance of the electro-hydraulic servo valve. This paper establishes a three-dimensional model of the double-nozzle baffle valve, and based on the environmental conditions of the variable depth of the sea, it studies and analyzes the deformation law and internal leakage of the slide valve under different depths of the sea. The results show that when the sea depth is 12 000 m, the gap between the spool and the valve sleeve is reduced to 2.752 μm, and the leakage is reduced to 0.020 5 L/min, which is close to 50% of the deformation and 98% of the leakage compared with the land environment. The results can be used to predict the use of electro-hydraulic servo valves in deep-sea environments, and this study is of great significance to the research of hydraulic systems.

Numerous studies have revealed that the operation of wind power facilities alters the momentum and heat distribution in the atmospheric boundary layer. By combining a mesoscale weather forecasting model (WRF) with a wind farm parameterization scheme (WFP), a suitable parameterization scheme was selected for a wind farm in China to analyze the potential impacts of wind farm operation on the local atmospheric boundary layer. It was found that during the operation of the wind farm, when viewed horizontally: the ground turbulence intensity and temperature increased in the downwind region, while the opposite trend was observed in the upwind region; the relative humidity decreased in the downwind region, while it relatively increased in the upwind region. Analyzing the wake effect in the vertical direction: the intensity of ground turbulence increases overall, especially in the rotating region of the wheel; the temperature increases significantly below and near the wheel, especially near the top of the wheel, while cooling is generally observed in the region above the hub height; the relative humidity decreases below the hub height as well as at the ground level, while fluctuations of humidity, both decreasing and increasing, are observed above the hub height, decreases as well as increases. This study provides a deeper understanding of the impact of wind farms on the atmospheric boundary layer and provides a scientific basis for wind farm planning and environmental impact assessment.

Hydraulic cylinder is the most important actuator in hydraulic systems. This article proposes a mechanical self-locking hydraulic cylinder based on the pre tightening force of the disc spring. This hydraulic cylinder can accurately lock the piston rod in any position for a long time, meeting certain high positioning accuracy requirements in certain usage scenarios. This article first establishes a calculation model for the piston rod locking theory, designs a three-dimensional model of the locking mechanism, and uses the three-dimensional model to conduct ANSYS transient structural simulation. Finally, a prototype of a mechanical self-locking hydraulic cylinder was made based on theoretical calculation results and a three-dimensional model. Simulation and experimental results show that the model can achieve precise long-term locking of the hydraulic cylinder piston rod at any position.

Aiming at the impact and noise generated in the working process of the hydraulic check valve automatic oil filling and pressure retaining circuit, the AMESim simulation model of the automatic oil filling and pressure retaining circuit with pressure relief function is established. Through comparison and analysis with the original scheme, it is found that the pressure relief mode can achieve more stable pressure relief by setting a unidirectional throttle valve on the oil circuit of the piston rod up and back, so as to avoid large hydraulic shock and noise.

On January 8, 2025, Professor KONG Xiangdong from Yanshan University was invited to give a presentation titled “Conservation and Breakthrough Integration of Technological and Industrial Innovation Advancing Hydraulic Components and Systems Toward High-end, Intelligent, and Green Development” at the “2025 Welcome Spring Festival Seminar of China Hydraulics Pneumatics & Seals Association” held in Beijing. Professor KONG Xiangdong analyzed the development advantages, bottlenecks, and prospects of hydraulics pneumatics & seals industry in the transformation towards high-end, intelligent, and green (three modernizations). Starting from the theoretical core of “Conservation and Breakthrough” and “Integration of Technological and Industrial Innovation”, he emphasized that the industry needs to consolidate the foundation of theory and process inheritance with “Conservation”, promote high-level technological self-reliance and self-improvement in the field of hydraulics pneumatics & seals with “Breakthrough”, and drive the high-end, intelligent, and green development of hydraulics pneumatics & seals industry through “Integration of Technological and Industrial Innovation”. The report also combines the exploration and practice of the hydraulic major and its research team at Yanshan University on the path of “Three Modernizations” development, and introduces a series of practical measures such as talent cultivation, diversified integration development, and technological innovation and transformation of the research team in the hydraulic engineering major at Yanshan University, to help solve the “Three Modernizations” development problems in hydraulics pneumatics & seals industry. This article is compiled from on-site reports and provides a theoretical framework and practical inspiration for the development of the “Three Modernizations” in hydraulics pneumatics & seals industry.

The hydraulic servo electro-hydraulic actuator integrates the control module and the hydraulic power module, the control module issues instructions to the intelligent controllable servo valve, the control hydraulic power module outputs force (or torque) with linear displacement (or angular displacement), drives the controlled object and completes the adjustment process through displacement feedback and pressure feedback to achieve closed-loop control of various functions. The built-in Internet of Things communication module can remotely monitor the operating status and fault diagnosis of the valve and cylinder. Using high-performance microprocessing controller, it can communicate with a variety of fieldbus sensors, such as SSI, 5V differential pressure orthogonal TTL encoder, Profuse-DP bus and other digital sensor interfaces, and can realize a variety of fieldbus control. It can realize position control, real-time position speed control, pressure (force) control, position-pressure (force) compound control, speed-pressure (force) compound control, multi-axis synchronous control and coordinated control, multi-axis controller combination as the slave axis and the main controller communication, up to 64 axis synchronous control or 32 axis coordinated control.

To investigate the effect of dynamic and static pressure combined mechanical seal on liquid film cavitation, a three-dimensional liquid film model was established using the Rayleigh step ring groove static pressure step as the research object. A comparative analysis was conducted on the cavitation area and leakage rate of the Rayleigh step ring groove and Rayleigh step ring groove static pressure step models, revealing the sealing mechanism of the Rayleigh step ring groove static pressure step fluid dynamic and static pressure combined mechanical seal. The research results show that the cavitation area of Rayleigh step ring groove static pressure step is larger than that of Rayleigh step ring groove, and the former has a smaller leakage rate. The cavitation area extends from the root of the reverse groove to the groove area, and the ratio of cavitation area and gas phase volume fraction increase with the increase of rotational speed, but decrease with the increase of pressure and film thickness. Therefore, under high pressure conditions, the forward and backward Rayleigh step ring groove static pressure step fluid dynamic and static pressure combined mechanical seal can better reduce leakage.

Aiming at the erosion wear problem with blackwater valve in coal chemical pipeline system, taking V-type regulating ball valve as the research object, based on computational fluid dynamics (CFD) and erosion wear theory, the erosion wear numerical simulation of V-type ball valve was carried out. The distributive law of flow velocity, pressure and erosion morphology in the fluid domain of V-type ball valve is obtained, and compared with the engineering failure valve. The results show that there is obvious negative pressure in the V-type ball valve under the condition of small opening, and the negative pressure value is much lower than the saturated vapor pressure of blackwater at 170 ℃, and the valve is prone to flow cavitation. Under the typical adjustment opening condition, the flow channel upstream surface in the ball body forms an obvious target-like high-pressure area due to the high-speed jet of the V port. Under the high-frequency erosion of the solid medium, the target-like high-pressure area is prone to obvious wear pits. The serious wear area of V-type ball valve is mainly distributed in the front seat of the valve, the upstream surface of the flow channel in the ball body, the valve body and the rear seat of the valve. When the sealing pair area of the valve seat is seriously scoured and worn by particles, it is easy to cause sealing failure. In addition, the maximum wear rate and average wear rate of the valve wall gradually decrease with the increase of the opening degree. When the relative opening degree is greater than 40%, the wear rate is significantly reduced. In order to prolong the service life of the valve, the V-type ball valve should be reduced to work at a small opening degree.

The unique structural design of the three-anchor buoy system can further improve the observation ability, stability and working reliability, avoid the entanglement of underwater equipment and anchor chain, and help to realize the monitoring of marine water profile data, which plays an important role in the field of marine monitoring. To explore the static characteristics of a single anchor chain within a moored buoy system under shallow sea conditions and the effects of buoy offset on the tension in each anchor chain and the system's restoring force. Based on the catenary equation considering the ground chain, the static characteristics of a single anchor chain are solved according to the Newton-Raphson iteration method. Through the static analysis of the three-anchor buoy mooring system, the effects of different offset displacements and offset angles on the tension of each anchor chain, the length of the catenary in the water, the system restoring force and its direction angle are investigated. The results show that the stiffness of the anchor chain increases with the increase of the horizontal span of the catenary. When the offset angle is constant, the restoring force of the buoy system increases with the increase of the offset displacement of the buoy. When the offset displacement is constant, the recovery force of the buoy system increases first and then decreases with the increase of the offset angle.

As one of the key actuators to achieve multi-functionality and intelligence in mechanical equipment, hydraulic cylinders are affected by the compression, thermal expansion and other characteristics of medium hydraulic oil in production and use, and its most prominent quality problem is that internal leakage is difficult to be directly detected and monitored outside the hydraulic system, which affects the factory efficiency and detection accuracy. In this paper, the test requirements and operation process of the traditional internal leakage detection method are optimized when applied to the factory inspection of hydraulic cylinders and equipment: the temperature range of the hydraulic oil and the carrier itself, the initial flushing speed, the start time of the test timing, the temperature at the beginning and end of the test, and the volume of the closed hydraulic oil in the test, etc., which improves the accuracy and efficiency of the factory inspection and has a certain guiding role for the actual operation.

In response to uneven stress distribution along the internal curve-guided surfaces during operation of traditional radial piston hydraulic motors, this paper proposes an improved design scheme aimed at optimizing the motor's roller pair structure to mitigate stress concentration, enhance dynamic characteristics, and prolong service life, thereby comprehensively improving motor performance. Stress levels experienced by rollers at different angles serve as the evaluation criteria, with the finite element analysis method used to analyze stress in the optimization scheme. Furthermore, dynamic analysis of the improved radial piston hydraulic motor is conducted using ADAMS software to further evaluate its compliance with design requirements. Research results indicate that the optimized scheme effectively alleviates stress concentration in the roller pair, reducing the average stress to 49.31 MPa, a 26.53% reduction compared to traditional designs, while achieving an output torque of 6200 N·m that meets practical operational demands. The test results show that the motor torque is about 6200 N·m, the mechanical efficiency of the motor is about 95%, and the mechanical efficiency and torque are basically no attenuation. This study provides robust theoretical support for optimizing the internal curve of hydraulic motors and holds promise for broader practical applications, thereby advancing hydraulic motor technology.

A flexible operation and adaptive impedance control strategy for robotic excavator is proposed to address issues such as force impact and vibration during construction. First, the composition and fundamental characteristics of the electro-hydraulic servo system are analyzed, and a dynamic model of the interaction between the robotic excavator's bucket tooth tip and the environment is established. Next, based on the force tracking error, the expected position of the robotic excavator's tooth tip is adjusted in real time, which indirectly modifies the impedance parameters. This approach reduces the reliance of the compliant control system on environmental position and stiffness parameters, leading to the development of a new adaptive impedance control strategy for robotic excavator. The simulation results demonstrate that, compared to traditional impedance control methods, the strategy proposed achieves precise tracking of both constant and dynamic forces, thereby enhancing the stability and flexibility of robotic excavator operations.

Particle erosion wear phenomenon occurs on the blade surface when wind turbines operate in sandy and dusty weather, leading to changes in blade morphology and degradation of its aerodynamic performance. In this paper, the dynamic erosion prediction method based on the coupled flow-solid-erosion model is used to simulate the erosion process of the NREL S809 straight wing section, to study the dynamic evolution of the surface wear caused by the particle erosion of the S809 straight wing section, and to analyze the change of the surface morphology of the S809 straight wing section and its impact on the aerodynamic performance under the conditions of different particle sizes. The study shows that: with the advancement of the erosion time, the cumulative effect of the erosion wear on the leading edge of the S809 straight wing segment surface is obvious, and the wear caused by the particles on the surface of the wing segment is intensified, and the depth of the erosion crater is gradually increased, which results in the fluctuation of the pressure coefficient of the surface of the airfoil and the increase of the degree of the static pressure disorder. With the gradual change of leading edge wear morphology, the turning position of the suction surface of the airfoil is gradually disorganized.

To address the resonance risks induced by natural frequency reduction in large-capacity hydraulic turbine runners, this study investigates the wet modal characteristics of turbine blades and the coupling mechanism with hydraulic excitation through fluid-structure interaction (FSI) analysis. The results indicate that under rated operating conditions, the first-order wet modal frequency demonstrates significant spectral deviation from rotational natural frequency, suggesting low resonance probability. As modal order increases, nonlinear amplification of frequency attenuation emerges due to fluid-added mass effects, with notably distinct reduction patterns observed between air and water media. Hydraulic excitation analysis reveals that low-frequency perturbations governed by guide vane count and rotational frequency harmonics constitute primary excitation sources, exhibiting exponential amplitude decay with ascending orders. High-frequency vortex shedding regimes display broad-band energy concentration characteristics. Spectral comparison demonstrates that the dominant excitation frequency band maintains over 1.5fold safety margin relative to the first six wet modal frequencies, while frequency shift characteristics effectively mitigate resonance risks through natural frequency migration.

Under the influence of dynamic stall, the aerodynamic performance of vertical axis wind turbine decreases and the spindle polarization increases at low tip ratio, which leads to the increase of operation and maintenance cost of vertical axis wind turbine. In order to reduce the adverse effect of dynamic stall, the effect of vortex generator on the dynamic stall characteristics of vertical axis wind turbine airfoil is studied by numerical simulation. Based on SST k-ω turbulence model, the aerodynamic performance of vortex generators in dynamic stall process with different installation spacing (6 mm, 8 mm, 10 mm) and installation angle (12°,15°,18°,21°) is simulated. The installation spacing of vortex generator has little influence on dynamic stall, and the installation spacing of 8 mm has better effect on dynamic stall of airfoil. The installation angle of vortex generator has great influence on dynamic stall. When the installation angle of vortex generator is small and the airfoil is at a large angle of attack, vortex generator cannot inhibit flow separation, the dynamic stall of airfoil is improved better when the installation angle is 18°.

In response to domestic insufficiency in the development of testing methods and high-end testing equipment for integrated pump-motor products used in modern mobile machinery Hydrostatic Transmission (HST), a high-stiffness and high-strength mechanical test rig, which is capable of conducting comprehensive tests for various models of test pieces, was first designed using a modular design approach. A hydraulic system using a proportional relief valve for loading and a fuzzy-PID strategy for oil temperature control was also designed. Secondly, a measurement and control system hardware environment was constructed by using sensors, PLC and an industrial control computer, and the software for measurement and control of the upper and lower computers was developed. Finally, the designed and developed mechanical test rig, hydraulic system, and electrical and measurement and control systems were integrated and debugged to obtain a new type of comprehensive test system for HST integrated pump and motor. Prototype testing has shown that the developed equipment can carry out comprehensive performance tests for various models of HST integrated pump and motor products, including the factory and type tests, and is especially capable of conducting continuous impact and endurance performance tests under high temperature and high-speed conditions.

A medium-sized hydraulic excavator experienced a malfunction where the boom failed to lower, rendering the equipment inoperable. During troubleshooting, the pilot control pressure for boom descent, boom spool valve, boom load-holding valve, and hydraulic system cleanliness were inspected. Bench testing of the load-holding valve revealed delayed opening and sticking of the pilot stage under high-pressure conditions. Deformation simulations of the pilot valve sleeve and spool under varying pressures demonstrated significant sleeve deformation under high pressure, resulting in reduced clearance between the sleeve and spool. The primary root cause was identified as insufficient clearance in the load-holding valve pilot stage, with secondary contributing factors including hydraulic fluid contamination exceeding main valve specifications, creating spool sticking risks under high-pressure operation. Corrective measures involved optimizing the pilot stage clearance and implementing stricter hydraulic fluid cleanliness controls. Post-modification verification confirmed complete resolution of the boom descent failure, validating the effectiveness of the improvements.

In this paper, the effect of mineral oil content on the foam resistance of phosphate ester was studied. It was found that a very small amount of hydrocarbon oil (<0.1%) would lead to a significant increase in the foam resistance of fuel oil. The mineral oil content of two kinds of phosphate ester resistant fuels used in two power plants of CGN was determined by DL/T 1979—2019 method. The composition of the obtained mineral oil was detected by GC-MS. The results showed that the oil soluble substances (mineral oil) obtained after the new oil test were not completely hydrolyzed phosphate ester resistant fuel, partial hydrolyzed products and additives such as silicone oil. The oil soluble substance (mineral oil) obtained after the test of the old oil includes the incomplete hydrolyzed phosphate ester resistant fuel and some hydrolyzed products, as well as some high-boiling substances, which may be hydrocarbon mineral oil or the saponification of the hydrolyzed products and metal ions in the old oil. Therefore, the power plant should optimize the saponification and extraction methods when detecting the mineral oil content in the resistant fuel oil, to ensure that the resistant fuel oil is completely hydrolyzed during the test process, and to avoid the influence of hydrolytic products on the test results.

Digital twin can build a digital model in the virtual space that is similar in shape and behavior to the physical entity, which is an advanced technology to realize the fusion of virtual and real. The performance of relay valve directly affects the safe operation of EMU, so it is of great significance to study its behavior state under health and fault conditions. Based on the digital twin modeling technology and basic mathematical model principle, this paper constructs the digital twin model of relay valve, and corrects the digital model under health condition through genetic algorithm to improve the accuracy of the digital twin model of relay valve. By injecting common faults into the relay valve health model and simulating the working state of the relay valve under fault conditions, the digital twin model of the trunk valve is accurately mapped to the physical entity.

This paper analyzes the cause of failure of the normal braking function caused by decompression valve failure,which led to the aircraft crashing off the runway.Based on mechanism analysis,experimental verification,theoretical calculation,and other methods,an optimization plan is proposed to effectively reduce the occurrence of faults under existing structures.It is proposed that human control forces are relatively small compared to electromagnetic and hydraulic forces,and the adaptation frequency of valves that require human control in the hydraulic system should be increased to avoid accumulation of attachments and serious consequences caused by long-term non operation.

In response to the situation which some hydraulic cylinders can only use asymmetric structures but require closed systems, a symmetrical pump driven asymmetric hydraulic cylinder system scheme is proposed, which is to design a flow balance system on top of the conventional closed system structure. The scheme is designed, calculated, and simulated to obtain the static and dynamic characteristics of the system. And it has provided for the instantaneous suction problem which occurring in dynamic characteristics, and it has verified through actual machine testing.

Axial piston pumps, known for their high efficiency and high pressure characteristics, are widely used in hydraulic systems of various engineering equipment. However, when the pump operates at high speeds and low flow rates, cavitation phenomena are prone to occur at the pump inlet, which can reduce the efficiency and reliability of the pump. This paper focuses on the pressure-boosting characteristics of the centrifugal impeller at the inlet of the axial piston pump and employs Computational Fluid Dynamics (CFD) simulation methods to analyze the pressure-flow characteristics of the inlet centrifugal impeller. The research reveals the mechanism behind the cavitation phenomenon during the pressure-boosting process and explores the impact of the impeller on the inlet self-priming ability and cavitation characteristics. The results indicate that by optimizing the geometric structure of the centrifugal inlet and adjusting the operating parameters, the cavitation phenomenon can be effectively suppressed, enhancing the efficiency and reliability of the axial piston pump. The centrifugal impeller placed in front can increase the inlet pressure of the piston pump, and the pressure-boosting effect is significantly enhanced with the increase of speed, which is beneficial in addressing the suction problem of the piston pump. The volute casing structure of the centrifugal impeller is twisted, and the excessive number of blades results in poor hydraulic performance of the centrifugal impeller. From the overall pressure distribution of the pump, it can be seen that when the piston communicates with the damping groove, the pressure changes rapidly. In terms of cavitation simulation results, cavitation is prone to occur in the rotor oil window and the interior cavity of the piston at the inlet area.

The axial force of the double-circular-arc helical gear pump is relatively large, which affects the volumetric efficiency and service life. Accurate calculation of axial force is necessary for designing balancing devices. The “arc-involute-arc” tooth profile equation is established and the theoretical displacement calculation formula is derived. The relationship between hydraulic axial force, meshing axial force and theoretical displacement is established through theoretical analysis and calculation, and then a simplified simulation model for calculating the axial force of the end face oil film is given. The accuracy of theoretical calculation formulas and simplified simulation model results was verified using a dynamic flow field simulation model. The results indicate that the hydraulic axial force and meshing axial force are equal in magnitude and independent of the gear angle. The calculation method for the total axial force acting on the gear is ultimately obtained, providing a basis for the design of axial force balancing device.

The hydraulic system of the underwater control module in oil fields is exposed to high pressure, high temperature, and corrosive environments for a long time, facing extremely high risk of failure. Therefore, in order to effectively diagnose and prevent maintenance of hydraulic systems, a fault diagnosis model for hydraulic systems will be constructed based on dynamic Bayesian networks. The experimental results indicate that both the historical failure probability of the hydraulic system and the predicted failure probability value increase with time. At T=0, the predicted hydraulic system failure probability value is 0.106, which is very close to the historical hydraulic system failure probability of 0.117. At T=20, the predicted failure probability is 0.194 and the historical failure probability is 0.198, with a slight increase in the difference in diagnostic probability between the two. In addition, from T=0 to T=20, the accuracy of model fault diagnosis is above 85%, with the highest prediction accuracy of 96.2% at T=0 and the lowest prediction accuracy of 85.7% at T=20. Research has shown that the proposed diagnostic model has good accuracy and stability in fault diagnosis, providing a new solution for intelligent fault diagnosis of SCM hydraulic systems in oil fields.

To ensure that the hydraulic damping device of the stepper machine can maintain good stability and reliability under different operating conditions, dynamic response of the damping force, the internal friction characteristics, and return characteristics of the hydraulic damping device were tested and analyzed based on the WPW-30A comprehensive test stand. According to the composition and working principle of the hydraulic damping device, the excitation loading scheme was established. The variation laws of the damping force with respect to speed, stroke, and temperature were obtained through parameter setting. The friction response was tested under low-speed conditions to avoid the interference factors of the damping force. The variation laws of the residual displacement under different excitation frequencies and different limit stroke conditions were obtained. The research results show that the comprehensive mechanical properties of the hydraulic damping device are good. The fluctuation value of the friction force during the reciprocating stroke is less than 5%, the minimum return rate under the limit conditions is more than 85%, and the hysteresis problem under high-frequency excitation is not significant. The dynamic performance testing method can provide effective design ideas and technical solutions for the development of hydraulic damping devices.

Taking a high-speed swash plate axial piston pump as the research object, a mathematical model of cylinder overturning moment under radial and axial forces such as inertia force of plunger shoe assembly, oil pressure of plunger cavity, spring preload force and oil film supporting force of distribution pair was established. The variation trend of overturning moment and additional overturning moment of the same coaxiality error under different deviation angles under rated working conditions is discussed under the premise of considering the uneven distribution of cylinder mass around the cylinder. The results show with the increase of deviation angle, the additional overturning moment curve of the cylinder block around x and y axis caused by the radial force presents a decreasing-increasing-decreasing trend, and the additional overturning moment of cylinder block around x axis is much larger than that of the latter, but the latter has a zero crossing situation. Under different deviation angles, the variation trend of the additional overturning moment curve of the cylinder block around x and y axis is the same due to the axial force, but the proportional relationship between the amplitude of the additional moment curve and the deviation angle is exactly opposite in the curve rising and falling stages.

In order to further investigate the flow characteristics of dry gas seals under complex flow conditions, the influence of turbulence on the steady-state performance of these seals was taken into consideration. The research focused on analyzing the behavior of a classical spiral groove dry gas seal and establishing a governing equation to characterize the pressure distribution in its fluid lubrication's gas film. Numerical simulation was employed to obtain pressure distribution in different flow states within the seal's flow field. By examining structural parameters and operating conditions, their effects on steady-state performance were evaluated using opening force and leakage rate as key metrics. The results indicate significant fluctuations in film pressure within the spiral groove under turbulent flow, with maximum pressure concentrated at its top section. Moreover, turbulent flow exhibits higher opening force compared to laminar flow. Regarding groove depth, an initial increase leads to an increase in opening force followed by a slowdown effect; however, increasing film thickness gradually decreases opening force. The impact of fluid turbulence is intensified at high parameters resulting in an increased leakage rate. Variations in groove depth and film thickness can easily lead to uneven local pressures exacerbating fluctuations in leakage rate. This research provides a theoretical framework for optimizing the design of dry gas seals for high-performance rotating machinery.

Many vocational colleges currently offer practical training courses related to hydraulic and pneumatic technology, but due to space limitations or insufficient equipment, it is difficult to apply the complex hydraulic and pneumatic comprehensive training platform to the actual teaching process. In response to the appeal issue, this article designs a comprehensive teaching equipment for mechanical arms based on digital twin technology for the “Hydraulic Transmission and Pneumatic” course experiment, and conducts research on the teaching content of hydraulic and pneumatic technology training courses based on this set of training equipment. The content involves the recognition of basic knowledge of hydraulic and pneumatic, the assembly of mechanical arms, the connection of pneumatic (hydraulic) circuits, the design of control systems, and the digital twin debugging of the entire machine. Each teaching unit is divided into virtual debugging and physical operation parts. After students independently complete equipment cognition and system simulation debugging in the virtual equipment, they are divided into groups and batches for practical practice and functional verification of the physical devices. Through this virtual real teaching mode, the demand for physical equipment in the teaching process is reduced, and students have more practice opportunities in the practical training learning process, which can provide students with more practice opportunities during the practical training process, so as to improve the teaching quality of hydraulic and pneumatic technology training courses.

Proportional electromagnets are important electromechanical energy conversion components widely used in fluid proportional control and industrial sites. For proportional electromagnets, their structural parameters play a critical role in the force characteristics. Based on the initial rated parameters, preliminary structural parameters are calculated through formulas, and then a simulation model is established using finite element simulation software Ansys Maxwell to conduct finite element simulation analysis and experimental verification of their structure. The variation law of key structural parameters is determined, providing reference for subsequent product design research and large-scale production.

In light of the environmental and resource challenges posed by the growing global reliance on fossil fuels, wind energy has emerged as a pivotal sustainable energy solution. Vertical axis wind turbines (VAWTs) are increasingly recognized as crucial to the future development of wind energy technology, owing to their distinctive advantages. This paper meticulously evaluates the aerodynamic performance of both single and dual VAWTs under co-rotation and counter-rotation configurations, utilizing computational fluid dynamics (CFD) simulations. Additionally, a comparative analysis of the aerodynamic characteristics of single and dual units is conducted across various tip speed ratios (TSRs), employing the control variable method. The findings reveal that the wake dispersion of counter-rotating VAWTs is marginally broader in the transverse direction compared to that of co-rotating configurations, with a more pronounced flow acceleration effect observed at the gap. As the TSR increases, the wake recovers more swiftly, and the wind acceleration at the gap is enhanced, albeit within a more confined region. The optimization of TSR is thus identified as essential for boosting the power output of VAWTs and enhancing the wake recovery. These insights are instrumental in guiding the design refinement of VAWTs, optimizing the layout of wind farms, and advancing the implementation of wind energy technologies in both urban and offshore environments.

With the development of the automotive industry, the NVH issue of automotive systems has received widespread attention. This paper uses AMESim software for modeling and simulation to study the NVH problems of automotive hydraulic transmissions from the perspective of the hydraulic system. The simulation model of the hydraulic system of the transmission was established and calibrated with the test results. The steady-state and dynamic conditions were basically consistent with the actual situation, verifying the accuracy of the model. Through the simulation of pressure fluctuations and spectral analysis, it was found that the abnormal NVH was mainly caused by the meshing problem of the internal and external gear profiles of the pump, and the abnormal noise problem during oil filling mainly originated from the flow noise of the pipeline. The profile of the pump was redesigned by using AMESim. The simulation results show that in terms of the pressure fluctuation Angle, the use of the new cycloidal pump can effectively reduce the abnormal NVH of the system. After optimizing the profile of the pump, the 16th order multiplier of the system NVH is reduced by 75%, and the 48th order multiplier is reduced by 87%.

The aircraft hydraulic system has high pollution requirements. If the pollution exceeds the standard requirements, it will lead to the loss of functions such as clamping and sliding of the hydraulic system accessories, resulting in the failure of the hydraulic system. Therefore, the oil filter is set in the hydraulic system, and the off-pressure oil filter is arranged on the high-pressure line of the hydraulic system to the filter out impurities in the high-pressure pipeline. The high-pressure oil filter inlet and outlet connection pipe, the joint is straight screwed in, the joint is set in the rubber ring, to ensure that the sealing can be reliable under high pressure. But during the aircraft repair stage, it is found that due to the wear of the high-pressure oil filter thread, pressure impact and other reasons, the high-pressure oil filter thread and the joint thread clearance becomes larger, which also leads to the sealing gap becomes larger, and the rubber ring is extrusion-ground into powder from the gap, which resulting in seal failure and hydraulic system failure analysis. This will affect the completion of aircraft missions and flight safety. This paper studies the conventional seal failure analysis, improves and validates the seal structure, improves the seal reliability, and ensures the safety of hydraulic system and aircraft.

In centrifugal pumps and other rotating machinery, the mouth ring is usually used as a part to reduce the leakage flow, but with the decrease of the mouth ring clearance and the increase of the rotor speed, the influence of the rotor dynamic characteristics on the safe operation of high-speed pumps cannot be ignored. Based on the numerical simulation method, the stiffness damping characteristics of the mouth ring of a high speed centrifugal pump under working condition are calculated and studied in this paper. By modeling the flow field of a high speed centrifugal pump, the stiffness damping characteristics of the rotor in the mouth ring with different eccentricities and deviation angles are calculated. The results show that the stiffness damping characteristics of the mouth ring clearance are nonlinear related to the rotor eccentricity. The influence of inlet pressure distribution on stiffness damping of rotor under different eccentricity and deviation Angle is obvious. The circumferential asymmetry of inlet pressure causes the circumferential asymmetry of stiffness damping characteristics of mouth ring, in which the influence of main stiffness is most obvious.

The hydraulic system requires high cleanliness during its operation. As an important executing component in the hydraulic system, the cleanliness of the hydraulic cylinder will directly affect the performance and service life of the entire hydraulic system. Due to their large size specifications, it is difficult to clean the components of large hydraulic cylinders, and the cleanliness cannot be guaranteed. This study focuses on exploring a set of cleaning methods for large hydraulic cylinder barrels, piston rods, and small parts, providing effective cleaning techniques to ensure that the cleanliness level of large hydraulic cylinders is stably controlled below NAS 8, with high efficiency and low cost to ensure the cleanliness of large hydraulic cylinders, and to improve the reliability and service life of hydraulic systems.

Aiming at the issues of heavy workload and low efficiency in test data processing during hydraulic pump efficiency testing, an automated data processing method based on the zero-pressure intercept method was proposed. During the experiment, pressure and temperature compensation were applied to flow measurements, with error points eliminated using the least squares method. A MATLAB algorithm implementing this methodology was subsequently developed. The research demonstrates that the exclusion of error points enables high-precision measurement of no-load displacement, while the application of the MATLAB algorithm significantly improves testing efficiency for pump no-load displacement. Furthermore, the integrated approach of compensation and error elimination enhances the overall reliability of hydraulic pump performance evaluation.

The utilisation of underwater chemical injection technology has a plethora of applications in the fields of underwater energy extraction and marine environmental protection. In this paper, the recently developed CIMV (Chemical Injection Metering Valve) equipment, created by certain company is taken as the research object. Using experimental measurement methods, flow rate and differential pressure data for media with different viscosities were obtained. A fitting analysis was performed to establish the relationship between the flow coefficient and viscosity for the reference and calibration media. This relationship was then used to derive a general formula for the outflow coefficient and a general formula for flow rate, which can be applied to a range of viscosity media. The results of the formulae and the experimental error value were found to be less than 3.0%.