20 June 2026, Volume 50 Issue 6

    

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  Research on Evolution of Blade Wall Turbulence over Blades of Hydraulic Torque Converter Considering Stator Surface Roughness

  CHAI Bosen, ZHAO Tianyi, REN Yi, ZHENG Qiulin, MING Xiaoyu, GONG Hengte

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 1-8. https://doi.org/10.11832/j.issn.1000-4858.2026.06.001

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  The stator surface roughness significantly alters the blade wall turbulence structure of the torque converter, thereby affecting its operational performance. Therefore, studying the influence of stator surface roughness on flow field evolution holds important research significance and application value. Considering manufacturing constraints, several groups of stator blade surface roughness levels are selected. Based on CFD, the internal flow field of the torque converter is numerically simulated using the SST k-ω turbulence model, and the three-dimensional vortex structures under different stator surface roughness levels are comparatively analyzed. The results indicate that: the variation in stator surface roughness significantly affects its blade wall turbulence structure. As the roughness increases, the area of the high-velocity region on the blade suction side at the inlets of the stator, pump, and turbine gradually shrinks, the velocity magnitude drops significantly, and the overall vortex system becomes more chaotic. Under stall conditions, with the progressive increase in stator blade surface roughness, the error between the torque converter's torque ratio and the experimental value decrease by approximately 2.7%, 3.6% and 1.24%, respectively, compared to the smooth blade. The pump torque coefficient decreased by approximately 1.6%, 2% and 4.45%, respectively. The research results can provide certain technical guidance for the flow field analysis and blade manufacturing of torque converters.
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  Explicit Dynamic Modeling and Improved Fuzzy PID Control for Valve-controlled Air Springs

  YUAN Xiao, ZHU Qingbo, XIA Wan, YANG Sheng

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 18-31. https://doi.org/10.11832/j.issn.1000-4858.2026.06.003

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  We investigate dynamic decoupling modeling and intelligent control for valve-controlled air spring height servo systems facing strong nonlinearity and dead-zone oscillations. An explicit analytical model based on displacement-mass dual regression eliminates implicit pressure algebraic loops in Simulink co-simulations. Frequency domain analysis reveals the stabilization mechanism of negative derivative gain under coupled flow integration and time delay, proving its necessity for suppressing low-frequency divergence. Guided by these findings, an improved fuzzy PID controller with asymmetric rules addresses proportional valve dead-zones and start-up delays. Simulation results indicate that the proposed strategy significantly suppresses limit cycle oscillations and achieves steady-state tracking of ±0.005 mm under nominal loads. Moreover, the system maintains monotonic convergence under adverse perturbations, including a mass increase and deteriorated hardware parameters (dead-zone widening and time delay extension).
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  Design of Spool Position Control Strategy for High-response High-flow Electro-hydraulic Servo Valves Based on Backstepping Method

  CAI Pengyang, ZHANG Kai, CHEN Lijuan, CAO Xiaoming, AI Chao, GAO Wei

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 32-39. https://doi.org/10.11832/j.issn.1000-4858.2026.06.004

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  High-response and high-flow electro-hydraulic servo valves suffer from severe nonlinearity and poor control accuracy. Owing to large output flow, the flow force acting on the power-stage spool increases significantly, which intensifies system nonlinearity and reduces control accuracy substantially. As a result, it is difficult to improve the frequency response of high-flow electro-hydraulic servo valves. To address this issue, a mathematical model of the electro-hydraulic servo valve is established based on its high-response and high-flow structure. Taking the pilot-stage voltage as input and the power-stage spool position as output, a backstepping control method is designed to improve spool position control accuracy under high-response and high-flow conditions, ensuring high dynamic tracking performance of spool position. Joint simulations using MATLAB and AMESim are conducted under a main valve pressure difference of 7 MPa. Results verify that the proposed control method enables the high-response and high-flow electro-hydraulic servo valve to achieve a frequency response of 81 Hz and a flow rate of 732.56 L/min, meeting operational requirements.Research on the backstepping control method for spool position of high-response and high-flow servo valves provides a theoretical reference for the independent development of such valves in China.
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  Numerical Simulation of Compression Ignition in Lubricating Oil Mist Within High-pressure Flow Regulating Valves

  LI Jiacheng, GAO Longlong, HUANG Hejie, LI Baoren

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 52-59. https://doi.org/10.11832/j.issn.1000-4858.2026.06.006

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  Fire risks associated with lubricating oil mist leakage during the rapid closure of flow regulating valves in high-pressure pneumatic systems are addressed in this study. A numerical model of high-pressure mixture compression combustion is established to investigate the ignition characteristics and underlying mechanisms. High-pressure air and a lubricating oil mixture are taken as the working media. The combustion model and multicomponent transport model are coupled through C-language user-defined functions. The flow field, temperature field, and combustion reaction kinetics characteristics during valve closure are simulated. The compression ignition behavior of lubricating oil mist is revealed. Ignition is promoted by air shock waves through adiabatic compression heating in the stagnation zone and turbulence-enhanced mixing. During rapid valve closure, the small enclosed air region upstream of the valve is subjected to adiabatic isentropic compression. Compression heat is thereby generated, the air volume is rapidly reduced, and the pressure and temperature are sharply increased. As a result, ignition at two key locations is triggered under the combined effects of compression heating and turbulence-enhanced evaporation and oxidation. A reference for improving the reliability of high-pressure pneumatic systems is provided by this model.
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  Analysis Method for Working Status of Aviation Fuel Gear Pump

  HONG Li, BAI Wenfeng, HUA Shiyang, ZHANG Chao, ZHOU Muhang

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 60-68. https://doi.org/10.11832/j.issn.1000-4858.2026.06.007

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  Aviation fuel gear pumps suffer from severe wear of floating bushings under high-speed operation due to uneven dynamic loads. Moreover, the micro-motion of the floating bushings affects end-face leakage of fuel gear pumps, which further affects the outlet pressure and flow rate. To address this issue, a lumped parameter model is proposed to simulate the pressure distribution in the internal flow field of gear pumps. According to the operating characteristics of fuel gear pumps, a lumped parameter mathematical model is established. Simulations are carried out using the co-simulation platform of MATLAB+AMESim. The results show that the simulation results agree well with actual working conditions, and the computational efficiency of the internal flow field solution is significantly improved. The proposed method can effectively reflect the influence of gear leakage caused by floating bushing micro-motion on the internal flow field pressure. Compared with most existing simulation methods based on preset constant end clearances and complex 3D discrete solutions using Navier-Stokes equations, it has obvious advantages in practicality and efficiency and provides a more efficient and accurate technical approach for the performance research and optimization of aviation-fuel gear pumps.
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  Analysis of Deformation Characteristics of Electro-hydraulic Servo Valve Spool Under Action of Fluid-structure Interaction

  GAO Wei, LI Wenhan, CAO Xiaoming, HAN Xinlong, GAO Xiang, CHEN Lijuan

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 69-76. https://doi.org/10.11832/j.issn.1000-4858.2026.06.008

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  As the core component of a hydraulic control system, the spool valve stage of an electro-hydraulic servo valve deforms under multi-physics coupling, which changes the clearance between components and further affects the valve performance. To explore the structural deformation characteristics of the spool valve stage under fluid-structure interaction at different opening degrees, a 3D simulation model is established, and the one-way fluid-structure interaction numerical simulation is adopted to systematically study the deformation laws of the valve spool, valve body and valve sleeve within different opening degree ranges, while the dynamic change of the matching clearance is quantified by a radar chart. The simulation results show that when the valve port pressure difference is 7 MPa, the maximum deformation of the valve body reaches 11 μm and is concentrated at the oil return port, and the maximum deformation of the valve spool is 1.86 μm and that of the valve sleeve is 2.32 μm, both concentrated at the oil inlet port; with the increase of opening degree, the valve spool and valve sleeve show an inward compression trend, while the valve body shows an outward expansion trend. This study reveals the structural deformation characteristics and dynamic clearance changes of the spool valve stage under different opening degree conditions and provides an important basis for the structural optimization design of electro-hydraulic servo valves.
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  Optimization and Experiment of High-pressure-ratio Ejector Nozzle

  FENG Chunyu, WANG Jintao, ZHONG Ziyi, QI Jun, YU Hongyi, YANG Yingqiang

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 77-86. https://doi.org/10.11832/j.issn.1000-4858.2026.06.009

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  When boost pressure ratio exceeds 2.5, ejectors suffer flow fluctuations and instability. We use numerical simulation with entrainment coefficient as the index. It investigates the effects of key nozzle structural parameters on performance via single-factor analysis and response surface method. Results show that nozzle throat diameter and length both significantly affect internal flow and entrainment, with clear interaction. Throat diameter is the dominant factor. The optimal range is throat length 0.63~0.68 mm and throat diameter 6.42~6.52 mm. Verified by field tests, under high-pressure inlet of 44.97 MPa, the ejector entrains low-pressure inlet of 4.89 MPa and boosts it to pipeline pressure of 12.5 MPa, achieving a boost ratio of 2.6. This confirms the optimization's feasibility and engineering application. The results provide theoretical basis and engineering reference for ejector structure design.
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  Simulation Analysis and Experimental Verification for Sealing Performance of PTFE Lip Seals

  HUANG Tingzhen, CHAO Qun, XU Min, WU Xuan, LIU Chengliang, LUO Hao

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 98-107. https://doi.org/10.11832/j.issn.1000-4858.2026.06.011

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  This study focuses on PTFE lip seals for aircraft fuel pumps. A three-dimensional finite element model is developed in MSC MARC software to simulate the full sequence of seal assembly, fluid pressurization, and shaft rotation. Additionally, an experimental test platform is built to measure the friction torque of PTFE lip seals. Experimental results demonstrate that at the majority of rotational speeds, the simulation error of the friction torque does not exceed 5%, validating the effectiveness of the simulation model. The simulation analysis reveals that the primary seal lip experiences much higher contact stress than the secondary lip and plays a dominant role in sealing performance. The peak stress consistently occurs at the edge region of the lip contact zone and remains relatively stable during rotation. As the inclination angle of the primary seal lip increases, the maximum contact stress rises by 15.37%, while the contact width varies slightly within 8.94%. When the thickness of the primary seal lip increases from 0.5 mm to 0.9 mm, the maximum contact stress surges by 345.65%, whereas the contact width shows negligible variation. Furthermore, interference between the primary and secondary seal lips after assembly can be effectively avoided when the primary seal lip thickness is less than 0.6 mm.
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  Rolling Contact Fatigue Properties of Water-lubricated Carbon Fiber Reinforced Polyetheretherketone

  ZHANG Xiaoqiong, SHUAI Aozu, LI Donglin, NIU Rongjun, LI Fugui, LIU Yinshui

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 9-17. https://doi.org/10.11832/j.issn.1000-4858.2026.06.002

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  Carbon fiber reinforced polyetheretherketone is an ideal material for water hydraulic pump friction pairs due to its high mechanical strength, corrosion resistance, and self-lubricity. Studying its rolling contact behavior under water lubrication provides new options for pump development. A micro-scale fiber-matrix model is established to simulate the internal stress distribution of carbon fiber reinforced polyetheretherketone under rolling contact. Simulation results show significant stress concentration at the fiber and interface regions. A rolling contact test bench is built, and rolling contact experiments are conducted. The contact fatigue S-N curve of carbon fiber reinforced polyetheretherketone is established at a 95% confidence level. Results show that the rolling contact fatigue life decreases significantly with increasing contact pressure, following typical material fatigue behavior. At contact stresses of 165~233 MPa, the fatigue life ranges from 2×10⁶ to 1×10⁷ cycles. At 135 MPa, carbon fiber reinforced polyetheretherketone exhibits excellent fatigue resistance under water lubrication. Surface damage analysis reveals that interface debonding and fiber breakage are the main failure modes. This study offers theoretical and experimental support for developing water-lubricated rolling friction pairs.
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  Optimization of Frequency Response Characteristics of Reverse Follow-up Proportional Valve Based on Orthogonal Test

  ZHOU Yuheng , MIN Wei , WANG Jiamin, LIAN Jie

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 40-51. https://doi.org/10.11832/j.issn.1000-4858.2026.06.005

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  To address the insufficient working frequency bandwidth, large pilot spool dead zone, and low steady-state control accuracy of a reverse follow-up proportional valve, we target three key structural parameters of the feedback valve port: notch depth, notch length, and notch angle. A mathematical model of the valve is established. The influence of these parameters on the system corner frequency and dynamic characteristics is analyzed. An orthogonal test with three factors and five levels is designed. The dead zone of the pilot spool, displacement ratio, and flow area gradient are used as evaluation indicators. Range and variance analysis determine the weight and significance of each structural parameter. The optimization scheme is validated by AMESim dynamic simulation and prototype tests. Results show that the optimized valve achieves a stable displacement ratio of about 1.17, an 11.09% reduction in pilot spool dead zone, an effective working frequency increased from 20 Hz to 35 Hz, and an opening/closing time below 14 ms, significantly improving the dynamic response characteristics of the reverse follow-up proportional valve.
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  Coupling Modeling and Reliability Optimization Design for Coordinated Retraction-extension Function of Aircraft Landing Gear

  LIU Shuangquan, REN Bo, ZHOU Changcong, CUI Lijie

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 87-97. https://doi.org/10.11832/j.issn.1000-4858.2026.06.010

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  We carry out reliability optimization design for the coordinated retraction-extension function of the landing gear hydraulic system. It addresses the harsh landing condition of aircraft after high-altitude, low-temperature and long-endurance cruising, and solves the engineering problems of insufficient reliability in left-right coordinated retraction-extension of landing gear and asymmetric failure caused by low-temperature medium characteristics. Based on the AMESim-MATLAB parametric joint simulation platform, we establish a reliability analysis model with series failure modes considering timeliness and symmetry. It completes the reliability evaluation and sensitivity analysis of the coordinated retraction-extension function of the landing gear hydraulic system for a certain aircraft. We take the maximization of the comprehensive reliability of the coordinated retraction-extension function as the optimization objective. It constructs a multi-constrained reliability optimization model that includes retraction-extension timeliness constraint, action symmetry constraint and parameter engineering constraint to realize the optimal matching of design parameters. Results show that the comprehensive reliability of the coordinated retraction-extension function of the landing gear hydraulic system is improved from 0.6520 to 0.9801 after optimization, which meets the design threshold requirement. The retraction-extension timeliness and action symmetry are both significantly improved. The proposed method provides theoretical support for the reliability design, parameter matching and maintenance support of complex aerospace electromechanical-hydraulic systems.
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  Real-time Monitoring Method for Check Valve Chattering Based on Wavelet Packet Decomposition and Support Vector Machine

  ZHANG Jiawei, ZHANG Wensheng, WANG Ji, QU Dechao, CAI Xiangui, LIU Fanghua

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 108-118. https://doi.org/10.11832/j.issn.1000-4858.2026.06.012

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  Check valves are critical components in hydraulic and pneumatic systems. Chattering phenomena can significantly degrade system performance and lead to premature valve failure. To achieve real-time monitoring and early warning of check valve chattering, we investigate the adaptation and application of an intelligent monitoring method based on wavelet packet decomposition and support vector machine specifically for check valves. Pressure signals are collected from the valve outlet using a pressure sensor during operation. Wavelet packet decomposition is applied to extract time-frequency features, and the energy distribution and energy entropy of each sub-band are calculated. A training sample set is then constructed, and a support vector machine based chattering recognition model is established. Finally, a real-time monitoring system is designed for online condition evaluation of the check valve. Experimental results show that the proposed method achieves 94% accuracy on the test set and 97.2% accuracy in cross-validation, effectively identifying the chattering state of the check valve. This provides a reliable technical means for real-time monitoring of check valves in industrial applications.
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  Development and Test of Three-Directional Six-degree-of-freedom Hydraulic Vibration Table System

  WANG Lijuan, HAO Yanyan, DOU Xuechuan, WANG Meng, HOU Jingfeng, CUI Guangzhi

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 119-126. https://doi.org/10.11832/j.issn.1000-4858.2026.06.013

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  A three-directional six-degree-of-freedom hydraulic vibration table test system with a 3-2-1 configuration is developed. It has a rated load capacity of 500 kg, an operating frequency range of 0.1 Hz to 100 Hz, and a maximum amplitude of ±125 mm. The system composition and working principle of the hydraulic vibration table are introduced and tests on its core performance indicators are conducted, including maximum excitation force, peak velocity, random vibration test capability, and sine sweep test function. The test results show that all performance indicators meet the design requirements, with some even exceeding the design specifications. Key equipment such as the vibration controller, servo controller, and acceleration sensors are independently developed, with a domestically sourced content rate exceeding 95%.
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  Waveform Reproduction Control Method for Electro-hydraulic Servo Systems Based on Composite Sliding Mode Control

  GUO Chen, KONG Weijian, ZHU Zhiying

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(6): 127-136. https://doi.org/10.11832/j.issn.1000-4858.2026.06.014

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  Waveform reproduction control for electro-hydraulic servo systems is essential for simulating road spectrum. The target signals typically exhibit broadband and non-stationary characteristics, making it challenging for traditional control methods to balance low-frequency tracking accuracy with high-frequency dynamic response. To address this, a waveform reproduction method based on composite sliding mode control is proposed. To overcome the instability induced by high-frequency phase lag and the increased steady-state error caused by small-error overshoot—both inherent to the fixed gain in traditional integral sliding mode control—a variable-gain nonlinear integral sliding mode control is designed. Specifically, the target signal is pre-processed to filter out high-frequency transients, and a custom nonlinear function is integrated into the sliding surface. Furthermore, to tackle inaccurate system modeling and model uncertainty, a dual-loop control structure is constructed: the inner loop employs the aforementioned sliding mode controller for dynamic tracking and suppression of uncertainties, while the outer loop incorporates iterative learning control to refine trajectory tracking through feedback correction of historical iteration errors. Based on the publicly available Centro earthquake waves and class D road spectrum datasets, simulations are conducted to compare with methods such as adaptive inverse control, iterative learning control, and sliding mode control. The results show that when the reference signal is the class D spectrum and Centro earthquake waves, the relative root mean square errors of the proposed method are 2.94% and 8.28%, respectively, demonstrating higher reproduction accuracy and validating its effectiveness.