Browse Topic: Power and Propulsion

Items (65,025)

A Simple and Efficient THINC Scheme for Multiphase Flow via Dominant-Material Selective Reconstruction

2026-99-1229

9/4/2026

Multiphase compressible flow problems are widespread in aviation, aerospace, transportation, military, and industrial fields, for instance, in underwater explosion bubble dynamics, fuel injection for hypersonic vehicles, liquid sloshing in propellant tanks, and supercavitating underwater vehicles. This paper proposes an improved THINC (Tangent of Hyperbola for Interface Capturing) method for multiphase flow simulations, based on a selective reconstruction strategy for the dominant material. The core of the strategy is to apply the THINC reconstruction exclusively to the material with the largest volume fraction within a multiphase mixed cell, which numerically governs the local interface evolution. The volume fractions of non-dominant materials are then obtained through a proportional distribution that inherently ensures the summation (Σαk = 1) and boundedness (0 ≤ αk> ≤ 1) constraints are met without explicit corrections. This approach reduces the number of THINC reconstructions for each time step in a multiphase mixed cell from Nm (the number of materials) to one, significantly simplifying the algorithm and lowering computational cost. It thereby avoids the error accumulation and complex renormalization procedures associated with conventional schemes that reconstruct all materials. While strictly maintaining volume fraction conservation, the proposed method preserves interface sharpness through the underlying THINC framework. The method is implemented in a diffuse-interface, multiphase Eulerian framework and validated with a series of challenging benchmarks, including shock-helium bubble interaction, triple-point problem, gas impact, and the more complex modified gas impact. Numerical results show that, compared with conventional multiphase THINC approaches that reconstruct every material, the proposed scheme can reduce CPU time by about 40.0% without compromising the accuracy of key physical quantities.

Wang, Wei, Zhong, Yanxu, Hu, Qinghua, Yang, Canqun

Dynamic Characteristics Analysis of Needle Roller Bearings in Planetary Gear Trains with Consideration of Inner Bore Spalling Defects of Planet Gears

2026-99-1279

9/4/2026

Driven by the growing demand for higher efficiency and load-bearing capacity in fields such as new energy vehicles and heavy-duty engineering machinery, planetary gear sets are increasingly operating at elevated rotational speeds, coupled with a corresponding expansion of their revolution radii. This dual trend directly induces a substantial surge in centrifugal acceleration acting on the internal needle roller bearings. Under the cyclic stress inherent to transmission operations, such enhanced acceleration not only accelerates the initiation of spalling faults on the inner bores of planet gears but also exacerbates the propagation and deterioration of these faults throughout the service life. To elucidate the influence mechanism of inner bore spalling on the dynamic response of planetary gear bearings, this study develops a specialized dynamic model. This model explicitly incorporates the compound kinematic effects of simultaneous rotation and revolution, thereby ensuring a high-fidelity reconstruction of actual operating scenarios. The research systematically investigates how different spalling types and dimensional parameters affect the system’s dynamic behavior. Numerical results demonstrate a positive correlation between the severity of the spalling defect and the dynamic response intensity. Specifically, the expansion of defect dimensions under harsh operating regimes markedly exacerbates both the contact impulses at the needle-roller interface and the overall vibration acceleration amplitudes. Notably, the amplitude increment of the needle rollers is far more pronounced than that of other components. These findings enrich the theoretical understanding of fault-induced dynamic responses in planetary gear systems and provide a solid theoretical and model-based foundation for optimizing the fault diagnosis, condition monitoring, and maintenance strategies of the associated needle roller bearings.

Zou, Desheng, Lai, Junbin, Guo, Wei, Dong, Peng, Xu, Xiangyang, Sun, Qiang

Development of Engine Nozzle Characteristic Determination System

2026-99-1242

9/4/2026

The determination of flight thrust for aircraft engines is an important means of evaluating engine and aircraft performance. The characteristics of the tail nozzle of the tested engine are an important data support for calculating flight thrust. In order to accurately evaluate the flight thrust of a certain type of engine, an “engine nozzle characteristic determination test system” is developed to obtain the thrust characteristic curve and flow characteristic curve of the nozzle. A calibration device and calibration process were designed for the experimental system to achieve in-situ calibration of the system.

Ren, Boyang, Jia, Wenjie, Song, Jiangtao

Research on Scalelike Adaptive Suction Flow for Wide-Speed Range Hypersonic Inlets

2026-99-1252

9/4/2026

As critical components of aircraft, hypersonic inlets utilize shock wave compression effects to pressurize incoming flow. The interaction between shock waves and the boundary layer tends to generate separation zones, and it adversely affects inlet performance. As a method to significantly enhance inlet performance, suction technology can substantially reduce the size of separation zones when they form in the inlet. However, when the inlet is started and operating normally, suction configurations may cause mainstream leakage and make it difficult to meet the requirements of inlets with wider speed ranges. This paper designs an adaptive scaliform suction structure that utilizes a lift-generating design to induce a slight upward deflection of high-speed near-wall flow. It can reduce high-speed mainstream leakage without compromising the effectiveness in low-speed separation zones. Numerical simulations are employed to evaluate its suction performance in both inlet separation zone flow fields and supersonic mainstream flow fields. The internal flow mechanisms of the scaliform suction structure are investigated, and differences in its behavior across various suction flow fields, as well as its interference with the mainstream, are discussed. The study reveals that when the height of the scaliform suction structure is approximately 1/8 of the incoming flow’s velocity boundary layer height, the suction flow coefficient in the separation zone is twice that in the hypersonic mainstream. Furthermore, the loss in Mach number and total pressure recovery coefficient of the near-wall supersonic mainstream is controlled within 5%. This structure exhibits an adaptive suction capability for separation zones, thereby extending the starting speed range of the inlet.

Zhao, Xuening, Zhao, Yilong

Design and Analysis of Transmission Line Tower Erection Equipment

2026-99-1240

9/4/2026

In response to the industry's problems of transportation difficulties, low efficiency, and high safety risks during the erection of high-voltage transmission line towers in mountainous areas, this paper proposes a light tower erection device that integrates connection, assembly, and fixing functions. The device adopts 180 mm Q345 equal-angle steel tower legs and is equipped with a hydraulic drive system. The tower body is raised through the coordinated work of the main and secondary hydraulic cylinders. In contrast, the vertical and horizontal hydraulic cylinders are used for auxiliary descent and precise fine adjustment. Its modular and lightweight structural design meets the transportation needs in narrow spaces in mountainous areas. The specifications of the hydraulic cylinder are determined by mechanical calculation, and the structural strength of the square tube and the main and secondary hydraulic cylinder connecting rods is verified by finite element analysis. Kinematic simulation confirms that the operating performance of the device is stable. This device provides an efficient and reliable piece of technical equipment for the construction of transmission lines in mountainous areas, which has important engineering application value and broad promotion and application prospects.

Li, Hailong, Chen, Zhen, He, Longping, Wang, Zhongpan, Li, Cheng

Optimal Design of the Driving Axle Housing of a Heavy-duty Automobile

2026-99-1225

9/4/2026

As one of the important freight modes, heavy trucks need a high- strength and high-reliability drive system to carry huge goods. Therefore, the drive axle housing, a key component, significantly influences the performance and service life of vehicles, and its design and optimization have high practical significance. Firstly, this study begins by creating a geometric model of the axle housing using SW and analyzes its stress distribution under four typical operational conditions. Through static analysis, it is concluded that the most critical operational conditions are the maximum deformation of 2.151 mm and the peak stress of 272.3 MPa; in the fatigue analysis of ANSYS Workbench, the minimum life is 820,000 times. Results from both static and fatigue assessments indicate that the initial axle housing design satisfies stiffness, strength, and fatigue requirements. There is a large margin in the structure, which has certain optimization space. Considering the most dangerous working condition, the response surface optimization module of ANSYS Workbench is used with the objective of mass reduction. Finally, the axle housing is reduced by 4.09 kg; the corresponding maximum deformation is 2.262 mm, meeting stiffness criteria, while the peak equivalent stress reaches 280.3 MPa, remaining below the material's yield strength. The minimum life is about 620,000 times, and the maximum fatigue life is 1 million times, which still meets the requirements of the vertical bending fatigue test. This lightweight redesign reduces material and manufacturing costs while maintaining the requirements for deformation, stress, and fatigue strength.

Zhao, Shenglian, Zhong, Weijie, Zhang, Jian

Comprehensive Analysis of Torsional Vibration Response in Marine Propulsion Shafting Systems

2026-99-1274

9/4/2026

The marine propulsion shafting system serves as the core component of ship power transmission, wherein torsional vibrations can easily lead to shaft cracking and failure. Thus, avoiding shafting resonance is vital for ship safety. Previous research primarily focuses on a single vibration mechanism of diesel engine propulsion shafting systems, lacking a comprehensive analysis of modal characteristics, frequency, and transient responses. This paper systematically investigates the torsional vibration characteristics of shafting systems, constructs a mathematical model for torsional vibrations, deduces a method for solving natural frequencies, and establishes a frequency-domain transfer function matrix using the Laplace Transform to theoretically derive the transient response of damped forced vibrations. Taking the propulsion shafting system of a low-speed diesel engine in a 10,000-ton oil tanker as an example, a multi-condition analysis based on a simplified shafting model is conducted. This includes modal solution analysis, 0–2000 Hz frequency sweep tests, and comparative experiments on transient responses under different excitation frequencies with a 1000 Nm torque. The study reveals the influence mechanism of the coupling between excitation frequency and natural frequency on the dynamic characteristics of the shafting system. By investigating torsional vibration patterns, this research provides a theoretical basis for vibration reduction design and resonance avoidance in marine propulsion shafting systems.

Zhang, Jiayi

Design and Performance Verification of a Wheel-Track Transformable Mobile Platform Based on a Four-Bar Mechanism for Rescue Scenarios

2026-99-1246

9/4/2026

Contemporary disaster rescue operations face challenges due to complex and hazardous terrains. Existing rescue robots with single locomotion mechanisms (wheeled, legged, tracked) and some hybrid ones have limitations in adaptability, efficiency, or structure. To meet the dual demands of complex terrains and limited space, this paper proposes a wheel-track transformable mobile platform based on a four- bar mechanism, which adopts a modular structure. A servo motor drives the active link to adjust the spatial position of the movable link (equipped with movable wheels), enabling smooth switching between wheeled and tracked modes. Key link lengths are determined via kinematic analysis, and a two-stage gear transmission system is designed. Adams simulation verification shows the platform completes wheel-track mode conversion on flat ground without component interference and can lift the center of gravity (CG) to surmount obstacles during slope climbing. The platform's feasibility is verified, providing a technical reference for designing highly adaptable rescue robots suitable for small spaces and complex terrains in post-earthquake or post-disaster scenarios.

Ma, Shangyuan

Research on Reliability and Durability Testing and Evaluation Technology for Hub Motor Corner Modules

2026-99-1236

9/4/2026

With the development of high-performance hub motors and modular assembly integration technologies, their reliability and durability have become key factors restricting industrial applications. Existing standards are mostly aimed at the hub motor itself, lacking systematic testing methods for highly integrated corner module systems. Based on a National Key Research and Development Program project, this paper conducts a series of research on reliability and durability test and evaluation technologies for the hub motor corner module system. By means of collecting vehicle-load spectra and combining user- relevance techniques, a multidimensional assessment framework is established, encompassing bench-scale axle-coupled tests, full- vehicle road reliability tests, and component-level environmental tests. The research outcomes have been applied to the testing and validation of actual prototype vehicles and components. Test results indicate that the developed testing methodology can effectively identify potential failure, providing crucial technical support for the optimized design and industrialization of hub motor corner modules.

Wu, Zhen, Liang, Dong, Gao, Fengling, Wang, Runze, He, Junnan

Assembly Accuracy Optimization of Aero-engine Section Based on Dynamic Weighting Multi-Objective Optimization Algorithm

2026-99-1272

9/4/2026

The pose-solving method for aero-engine component docking assembly often faces challenges such as slow convergence and susceptibility to local optima when dealing with complex optimization problems involving multiple features and constraints. This paper proposes an optimized assembly pose solution method for engine sections based on an improved multi-objective optimization algorithm. The method first preprocesses the high-density point clouds obtained from 3D scanning to extract geometry such as feature points, lines, and surfaces. It builds an assembly constraint model with geometric relations and process needs. It focuses on the pose solution phase: we transform the assembly problem into a nonlinear optimization problem to minimize parallelism error, gap error, and step error. In order to solve this multi-objective problem efficiently, we propose an iterative multi- objective optimization algorithm as the optimization engine and propose a dynamic weight allocation strategy. During iteration, the strategy adaptively adjusts the weight coefficients of three error terms in the overall fitness function due to the evolution of the population and convergence of each error term, guiding the search direction and balancing the algorithm's global exploration and local exploitation ability. Our results show that instead of adopting an optimization algorithm with fixed weights and a multi-Objective optimization system with fixed weight, the proposed pose solution method based on dynamic weight multi- objective optimization algorithm achieves a high accuracy and stability of the solution and can easily and accurately produce a good pose matrix which meets challenging assembly constraints, providing a practical theoretical framework and technical support for achieving high-quality automated engine assembly.

Huang, Mi, Wu, Guanghui, Su, Xun, Xu, Yongqian, Ding, Han, Liu, Xiaopeng

Experimental Testing and Finite Element Simulation on Tensile Mechanical Behavior of Nickel-based Superalloys

2026-99-1224

9/4/2026

The accurate prediction of high-temperature mechanical behavior of GH3230, as a core material for the new generation of combustion chambers in China, is a key technical prerequisite for promoting engineering applications. This article is the first to conduct a systematic study on the tensile properties of the alloy at three typical service temperatures of 200°C, 550°C, and 900°C, combining high- temperature tensile testing with numerical simulation. Through metallographic observation, the excellent microstructure characteristics of the alloy, including no grain boundary defects, inclusion phase size less than 5 μm, and uniform distribution, were clarified. Based on this, a multi-temperature adaptive tensile simulation model was established. Experimental verification showed that the model can accurately reproduce stress-strain tensile curves at different temperatures, with prediction errors controlled within a reasonable range, effectively breaking through the limitations of traditional single-temperature simulation. This study not only provides an efficient and accurate new method for the performance analysis and safety evaluation of GH3230 in a wide temperature range but also provides practical technical means to support the component-level engineering application of this material. At the same time, the research results also provide a reference technical path and research ideas for the multi-temperature mechanical performance prediction of other nickel-based high-temperature alloys.

Qiao, Yongle, Xie, Jiahui, Li, Lei, Zhou, Jie, Zhu, Yankun, Wang, Yifei

Study on the Vehicle Unsteady Vibration Control with a Semi-Active Strut

2026-99-1231

9/4/2026

Unsteady vibrations of vehicles, which can be easily perceived by the human body, may affect the driving experience and compromise driving comfort. However, the conventional three-point powertrain mounting system (PMS) often fails to offer a satisfactory solution. Here, a novel four-point PMS was proposed by introducing a semi-active strut (SAS), which can provide stronger damping in a low-frequency range to resolve this problem. Specifically, a thirteen degrees of freedom (DoFs) vehicle dynamic model (VDM) with four mounts was constructed, and the evaluation indices for unsteady vibration responses of the vehicle were determined and analyzed; Next, the PMS optimization design approach was employed to identify the proper position of installation and dynamic stiffness of the SAS, and meanwhile the 13 DoFs VDM and the force-sharing principle were used to identify the structural parameters of the strut; Last, comparative experiments were performed to analyze the effect of the strut on alleviating the unsteady vibration of the vehicle under varied unsteady vehicle states. The results showed that the SAS has significantly reduced the seat rail peak acceleration, verifying the effectiveness of our novel PMS in alleviating the unsteady vibration. The research provided a feasible solution to alleviate the unsteady vibration of vehicles and improve the driving experience.

Wang, Daoyong, Liu, Yongjiang, Ma, Bo

A Coaxiality Measurement Method Applicable to the Three Holes of an Engine

2026-99-1226

9/4/2026

To address the measurement challenges posed by the large diameters and wide spans of engine crankshaft holes, cylinder holes, and camshaft holes, as well as the abnormal laser measurement data caused by oil film adhesion and local protrusion structures on their inner walls, this paper proposes a non-contact coaxiality measurement method based on a laser displacement sensor (LDS) and a threshold-modified least squares ellipse fitting (TMLSE) algorithm. The method first preprocesses the data through median filtering and then employs an adaptive distance threshold based on maximum inter-class variance to eliminate outliers caused by oil film scattering and protrusions, achieving robust fitting of the cross-sectional centers. Subsequently, the datum axis is established using the least squares midline method, ultimately enabling the evaluation of coaxiality error. In the simulation experiments, a dual-hole model with an inner diameter of 100 mm and a spacing of 700 mm was simulated, where the right hole was translated by 1.5 mm to introduce coaxiality error. Each cross-sectional point cloud included 10% protrusion points (protrusion height of 10 mm) along with random noise and data loss simulating the effects of oil film. To assess the robustness of the method, a systematic analysis was conducted on the influence of laser incidence angles [80°,89°]on measurement accuracy. The results show that across different incidence angles, the maximum deviation between the coaxiality error obtained by the TMLSE method and the theoretical value is only 0.1582 mm, which is significantly better than that of the RANSAC, MZC, and MIC methods. Meanwhile, TMLSE demonstrates stable and efficient computational speed. The simulation verifies that this method offers higher fitting accuracy and robustness under both optical interference and variations in installation angle, making it suitable for the precision measurement of key engine hole systems.

Yin, Jiakuo

Compact Design and Simulation of a Four-Degree-of-Freedom Articulation Mechanism for Articulated Tracked Vehicles

2026-99-1292

9/4/2026

To address the compact design requirements of articulation mechanisms for articulated tracked vehicles, a collaborative design methodology integrating kinematic modeling and configuration optimization is proposed. First, kinematic models of the steering and pitching devices are established, and analytical relationships between hydraulic cylinder stroke and vehicle body articulation angles are derived, along with an analysis of how articulation point positions affect kinematic characteristics. Second, a calculation method for minimizing the longitudinal dimension of the articulation mechanism is established, with the constraint that the front and rear vehicle body tracks do not interfere during motion. On this basis, an integrated layout strategy and design procedure for the four-degree-of-freedom articulation mechanism are proposed by optimizing the cylinder connection method and installation angle. The proposed method is applied to the design of an unmanned articulated tracked vehicle, and a virtual prototype is developed for simulation verification. The results demonstrate that the articulation mechanism achieves a steering angle of 45.2°, a pitching angle range of −47.9° to 48.7°, and enables the vehicle to negotiate obstacles of at least 900 mm in height, which validates the effectiveness and feasibility of the design approach.

Li, Ningyi, Zhang, Chuanqing, Zhang, Shaoliang, Liu, Xixia

CFD Numerical Simulation Study on Flow Field Characteristics of Umbrella-Frame Combined Impeller

2026-99-1208

9/4/2026

For the mixing of hydroxy-terminated polybutadiene (HTPB) with silicon dioxide particles, this study adopts the Computational Fluid Dynamics (CFD) method to conduct a visual analysis on the fluid flow field characteristics generated by the umbrella-frame impeller (UF impeller) and umbrella-frame combined impeller (UFC impeller). Comparative studies are carried out from the dimensions of particle concentration distribution, fluid flow trend, vorticity, and path line. The results show that compared with the UF impeller, the UFC impeller, equipped with an upper blade structure, enables its generated flow field to cover the entire stirred tank more effectively, significantly improving the solid-liquid mixing efficiency. In addition, the fluid-structure coupled numerical method is used to analyze the structural deformation characteristics and stress distribution law of the impellers. The research findings can provide a reference for the optimization of dispersion and mixing processes of solid particles in high-viscosity fluids.

Li, Ruizheng, Sun, Zhenxing, Zhang, Yan, Wu, Qiong

Experimental Verification of Chatter Optimization for Deep Small Hole Micro-Boring Based on 05Cr17Ni4Cu4Nb

2026-99-1273

9/4/2026

Aircraft engine parts are extremely precise, and for deep, small-hole machining of the stainless steel 05Cr17Ni4Cu4Nb valve seat, the quality and sealing of the parts machined with current machining parameters are poor. This greatly affects production efficiency and quality. This article takes the optimization of the three elements of cutting as the starting point, uses the orthogonal experimental method to study which force most affects machining quality in the three directions of boring force, and selects the appropriate three elements of cutting to reduce cutting force. And analyzed the simulated chip shapes before and after optimization, and finally verified the optimization effect through the instrument equipment. A micro three- axis accelerometer was used to conduct machining experiments on deep small holes with cutting parameters before and after optimization. After optimization of cutting parameters, the tool's maximum axial deformation showed a reduction of about 51.60%, a reduction of approximately 58.75% was achieved in the maximum radial deformation, the maximum tangential deformation exhibited a decline of about 45.17%, and the peak overall deformation was reduced by approximately 50.66%. Compared with the pre-optimized state, using optimized cutting parameters to machine deep small holes resulted in a 72.31% reduction in the tool's axial acceleration, the radial acceleration by 63.36%, and the tangential acceleration by 71.68%, the tangential force by 65.29%, the axial force by 27.93%, and the radial force by 31.16%. Effectively reducing tool chatter and lowering chatter amplitude led to the disappearance of surface vibration patterns on the machined parts.

Liu, Xinwei, Shi, Guangfeng, Zhou, Yuning, Gao, Jinglong

Low-Cycle Fatigue Life Prediction Model Considering Mean Strain Effect for HTPB Propellant

2026-99-1290

9/4/2026

In order to investigate the effects of different strain levels on the low-cycle fatigue life of hydroxyl-terminated polybutadiene (HTPB) propellant, a series of fatigue tests were conducted under various combinations of strain amplitude and mean strain. The results indicate that fatigue life exhibits a decreasing trend with increasing strain amplitude and mean strain, while the effect of mean strain on fatigue life gradually weakens as the strain amplitude rises. Additionally, a distinct trend is observed at high strain levels: the higher the strain amplitude is, the lower the coefficient of variation is. Based on the fatigue life data obtained from the tests, with strain amplitude as the characteristic parameter, a mean strain function is incorporated into the classical log-log linear model, and a stepwise fitting of model parameters is implemented using the chaotic adaptive genetic algorithm (CAGA) and the least squares method. For the selection of the mean strain function, the coefficient of determination is adopted as the goodness-of-fit criterion to evaluate the modeling accuracy of the power function, exponential function, and quadratic polynomial, respectively. Ultimately, the power function is identified as the most suitable mathematical form for characterizing the mean strain effect, leading to the establishment of a low-cycle fatigue life prediction model considering both strain amplitude and mean strain. Compared with the measured fatigue lives, more than 90% of the predicted lives obtained from the proposed model fall within the two-fold scatter band, and 100% within the three-fold scatter band. This demonstrates that the model’s prediction accuracy satisfies practical engineering requirements, thereby providing reliable data support for the development of propellant damage models and the assessment of cumulative damage in solid rocket motors (SRMs).

Jiang, Yuke, Sun, Haitao, Ai, Junzhuo, Shen, Zhibin, Yuan, Jiehong

Design and Validation of a 7-DoF Robotic Arm Featuring Hybrid Pneumatic-Electric Actuation

2026-99-1222

9/4/2026

To enable more natural motion mapping between the human arm and a robotic counterpart while reducing control complexity, this paper presents a novel seven-degree-of-freedom (7-DoF) bionic robotic arm with hybrid pneumatic–electric actuation in an antagonistic configuration inspired by the skeletal structure and muscular actuation of the human upper limb. The design combines the high power density and intrinsic compliance of pneumatic artificial muscles with the precision and stability of electric motors, improving motion adaptability and payload-to-weight performance. Kinematic feasibility and motion smoothness for human-like waving are validated via forward kinematics and redundancy-resolved inverse kinematics, together with trajectory simulations. To quantitatively evaluate dexterity and operational range, Monte Carlo sampling is used to generate reachable postures across the workspace, producing a wrist activity map that characterizes attainable orientations and maneuverability. A prototype testbed is built to verify physical performance. Joint-angle tracking experiments for the wrist and elbow, as well as whole-arm coordinated-motion tests, demonstrate accurate trajectory tracking, smooth transitions, and stable motion. These results confirm the mechanical soundness and effectiveness of the proposed hybrid antagonistic actuation scheme. This work provides a practical basis for advanced control development and offers insights into hybrid actuation design for bionic robotic systems.

Dai, Yuanquan, Guo, Zhiqin, Zi, Mingkang, He, Zhaoyang, Song, Yongwei, Xie, Yinhui, Li, Jun

An Effective Pathway for Off-Road Tier 5 Emission Compliance

03-19-08-0041

8/31/2026

Proposed Tier 5 off-highway emission regulations for the 19–56 kW engine class pose significant technical and economic challenges. Unlike larger platforms, where selective catalytic reduction (SCR) is the standard nitrogen oxide (NOX) control strategy, engines in this class face cost and packaging constraints that limit complex aftertreatment adoption. This article investigates whether a production Tier 4 diesel engine and its existing aftertreatment can meet proposed Tier 5 limits through calibration and minor hardware changes alone, without major redesign or SCR. The approach combined a cooled exhaust gas recirculation (EGR) strategy with start of injection (SOI) timing optimization to manage the NOX–particulate matter (PM) trade-off, using the stock diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) system for particulate control. An EGR/SOI design-of-experiments (DOE) sweep identified an optimal calibration, validated over both the ramped modal cycle (RMC) and non-road transient cycle (NRTC) per Title 13 California Code of Regulations (CCR) Section 2423 for certification of variable-speed engines in this power category. Results indicate that the system can be a viable pathway of meeting upcoming Tier 5 final emission standards.

Patil, Shubham Vishwanath, Michlberger, Alexander, Bachu, Pruthvi R., Amaral Garcia, Herbert, Smith, Edward M.

A Study on the Dynamic Characteristics of Long-Span Single Conductors Using Meshfree Methods

2026-99-0424

8/28/2026

The free vibration characteristics of long-span transmission conductors form the fundamental basis for vibration control design, as their natural frequencies and mode shapes directly affect line safety and the selection of vibration suppression devices. In this study, the three-dimensional linear free vibration governing equations were derived through functional integration of the kinetic and potential energies by using Hamilton’s variational principle. Compared with the conventional integral transform method, an improved meshfree discretization strategy is proposed: the shape functions are constructed using the moving least squares (MLS) method, while the boundary conditions are treated with a fully transformed approach, thereby converting the partial differential equations into ordinary differential equations. Subsequently, a corresponding eigenvalue problem is solved to calculate the first few frequencies of the system, and the effect of conductor natural parameters on these frequencies for the transmission conductor is investigated. The results indicate that the natural frequency decreases when the conductor length becomes larger, and the rate of decrease becomes more gradual as the length increases; it decreases with increasing cross-sectional diameter; it decreases linearly with increasing material density; and it increases linearly with increasing elastic modulus. These findings demonstrate that conductor length, cross-sectional diameter, material density, and elastic modulus all have significant effects on the natural frequency. Among them, length and diameter affect the frequency by altering the conductor’s inertia and structural characteristics, whereas density and elastic modulus govern the frequency from the perspectives of inertia and stiffness, respectively.

Li, Chen, Cheng, Yongfeng, Li, Danyu, Qiu, Gang

Objective Quantification of Harmonic Impulsive Sounds and Interval Prediction of Sound Quality in Hybrid Vehicle Engines

10-11-01-0003

8/28/2026

Steady advancement is observed in global research on eco-friendly and sustainable transportation. Rapid technological evolution of hybrid electric vehicles (HEVs) is documented. Lower overall noise output and more compact structures are achieved in HEV engines relative to conventional internal combustion engines. The perceptibility of harmonic impulsive sounds is significantly enhanced by these design characteristics. A close correlation is observed between these acoustic phenomena and negative human auditory perceptions. These events are treated as a core focus for HEV noise, vibration, and harshness optimization. Accurate quantification of harmonic impulsive sounds is not achieved by conventional objective indicators. A favorable balance between reliability and accuracy is not established by existing subjective prediction models. Practical engineering applications of these methods are severely restricted. A novel objective quantification method for harmonic impulsive sounds is proposed in this study. The method is established based on time–frequency masking theory and tonal strength. Bench tests in a semi-anechoic chamber and subjective evaluation experiments with standardized rating scales are performed for data collection. Collected sound signals are decomposed through an integrated approach of wavelet transform and variational mode decomposition. Targeted feature extraction is completed for harmonic impulsive sounds. A quantitative index incorporating human auditory temporal and frequency masking effects is developed. The proposed index exhibits a significantly stronger correlation with subjective evaluation results than traditional objective metrics, confirming its superior ability to reflect actual perceived sound quality. An interval prediction model for sound quality evaluation is established based on support vector machines and kernel density estimation. Traditional objective metrics and the proposed index are introduced as key input parameters. Effective and reliable prediction of HEV engine noise subjective satisfaction is achieved by the model.

Lin, Xu, Liang, Xingyu, Shi, Zhiyuan

Study of Port Fuel Injection Engine Cold Start Unburned Hydrocarbons Reduction Using Computational Fluid Dynamics with a Reduced Iso-Octane Mechanism Considering Various Isomers and Thermal Decompositions

03-19-04-0021

8/27/2026

A modeling study was performed to find solutions to reduce the unburned hydrocarbons during cold start of a PFI (port fuel injection) SI (spark ignition) engine. Through modeling, the root cause for the high unburned hydrocarbons of the baseline engine during cold start was found. The slow combustion, which is due to the high amount of exhaust gas flowing back into the intake port and then becoming trapped inside the cylinder, is the root cause. A new valve lift, which can reduce the internal residual by 26%, was designed. Along with a fuel amount decrease of 35%, the UHC (unburned hydrocarbons) before the three-way catalyst can be reduced by 40%. The exhaust temperature using the new valve lift design increases by 400°C, which improves the performance of the three-way catalyst for further reducing UHC. In addition to the adoption of the new valve lift, an active SAI (secondary air injection) strategy was also investigated. Modeling results show that SAI can promote secondary combustion in the exhaust pipes to increase exhaust temperature and thus is beneficial for further oxidizing unburned hydrocarbons. The amount of active SAI mass flow rate should be controlled to less than 25% of the intake air flow rate to avoid the cooling effect dominating over the oxidation process. The duration of SAI should be from EVO (exhaust valve opening) to IVO (intake valve opening). For combustion modeling, a newly reduced iso-octane chemical kinetic mechanism was developed using carbon flux analysis to extract major reaction pathways for a wide range of practical engine temperature conditions. In the new reduced mechanism, a skeletal sub-mechanism for species starting from iso-octane to C4 is coupled with a recently updated H2/O2/CO/C1–C4 detailed sub-mechanism. Including a reduced NOx (oxides of nitrogen) sub-mechanism, the final mechanism has 681 species and 3332 reactions. Before the new reduced iso-octane mechanism was used, it had been validated with available experimental data of ignition delay times, laminar flame speeds, and important species profiles in the literature. Both the investigation of PFI engine unburned hydrocarbons reduction under cold start operating conditions and the development of a reduced chemical mechanism are the objectives of this work.

Guo, Dongshao, Zhang, Licheng, Yang, Shiyou, Bourg, Cyrus, Sun, Yong, Abidin, Zainal, Lin, Shujun

Performance and Emission Control Enhancement Using Green-Synthesized Additives in Diesel Engine

03-19-04-0020

8/24/2026

Cashew nut shell oil–based biodiesel (BD) is an environmentally friendly and sustainable alternative energy source that can help decrease the depletion of fossil fuels and reduce environmental pollution. In this research, the BD extracted from cashew nut shell was enriched with green-synthesized nanoparticles with various blends and evaluated for its performance. The BD20A blend recorded the best thermal efficiency of the brake, 29.5%, which was a boost of about 20.4% over diesel when using a medium load of 2.7 kW. Furthermore, the decrease in brake-specific fuel consumption was 36.2%, and exhaust gas temperature improved by 26.1% due to enhanced combustion, indicating better combustion and utilization of heat. The BD10A and BD20A recorded a considerable decrease in emissions compared to diesel under full-load conditions, with carbon monoxide and hydrocarbons reducing by 35.7% and 33.3%, respectively, and a moderate increase of nitrogen oxides. Among the multi-objective optimization approaches, the Jaya algorithm exhibited the fastest convergence rate and identified the optimum operating condition that achieved the best trade-off between engine performance and exhaust emissions. BD blends, particularly BD20A, provide greater thermal performance and better combustion behavior as well as lower exhaust emissions, making them viable as green alternatives to the traditional diesel fuel.

Victor Soosai Irudayaraj, S., Thanigaivelan, V., Brucely, Y., Lenin, N.

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, STEEL AMS6322, CADMIUM PLATED, .190-32 UNJF-3A

AS9914C (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - STEEL, DIFFUSED NICKEL-CADMIUM PLATED, DOUBLE HEXAGON EXTENDED WASHER HEAD, UNS K14675, 195 KSI MIN, .2500-28 UNJF-3A

AS9209D (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, CORROSION AND HEAT RESISTANT NICKEL ALLOY (UNS N07001), 165 KSI MIN, .3750-24 UNJF-3A

AS9699D (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, NICKEL ALLOY, UNS N07718, 185 KSI MIN, .3125-24 UNJF-3A

AS3245E (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE-DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, CORROSION RESISTANT STEEL (UNS S17400), 140 KSI UTS MIN, .2500-28, UNJF-3A

AS3168C (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, FULL SHANK, STEEL AMS6322, CADMIUM PLATED, .250-28 UNJF-3A

AS9933C (Current)

8/18/2026

E-25 General Standards for Aerospace and Propulsion Systems

Engine Intake Air Water Separation Test Procedure

J2554_202608 (Current)

8/18/2026

This water separation technical report has been established to cover heavy-duty engine intake filter systems. It may also be applicable to some automotive and industrial air inlet systems where water separation is an issue.

Air Cleaner Test Code Standards Committee

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, CORROSION-RESISTANT STEEL (UNS S17400), 140KSI UTS MIN, .3125-24, UNJF-3A

AS3169C (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, AMS5643 (UNS S17400), . 3750-24, UNJF-3A

AS3170C (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, AMS5643 (UNS S17400), .4375-20, UNJF-3A

AS3171C (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, AMS5643 (UNS S17400), 140 KSI, .5000-20, UNJF-3A

AS3172C (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX, EXTENDED WASHER HD, PD SHANK, CUP WASHER LOCKED, CADMIUM PLATED, STEEL, UNS G87400, 125 KSI MIN, .2500-28 UNJF-3A

AS9681C (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, UNS S66286, 130 KSI, .3125-24 UNJF-3A

AS9112D (Current)

8/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, CORROSION AND HEAT RESISTANT STEEL, UNS S66286, UTS 130 KSI MIN, .3750-24 UNJF-3A

AS9559F (Current)

8/15/2026

E-25 General Standards for Aerospace and Propulsion Systems

SCREW, MACHINE - STEEL, DIFFUSED NICKEL-CADMIUM PLATED, DOUBLE HEXAGON EXTENDED WASHER HEAD, UNS K14675, 195 KSI MIN, .1640-36 UNJF-3A

AS9207D (Current)

8/14/2026

E-25 General Standards for Aerospace and Propulsion Systems

Numerical Simulation Study on Fire Prevention in Aero-Engine Fuel Tube

2026-99-0303

8/14/2026

Transient gas-liquid two-phase flow in aero-engine fuel pipelines was examined using numerical simulations, focusing on the influence of flow rate on phase change behavior. Under low-flow conditions, phase change occurred repeatedly near the pipe wall, where vapor layers formed and collapsed in an intermittent manner. These processes introduced noticeable unsteadiness in the local mass flow and pressure fields. When the flow rate was increased, vapor generation was largely confined to a narrow region adjacent to the wall, and the overall flow exhibited a more stable character. The results suggest that flow-rate-dependent phase change plays an important role in determining the stability of fuel transport and should be considered in the fire safety assessment of aircraft fuel systems.

Wu, Bin, Xin, Bo, Zeng, Tai, Su, Zhengliang

Influence of Roundness and Geometric Errors on Lubrication Performance of Engine Journal Bearings

2026-99-0321

8/14/2026

This paper focuses on the critical issue of lubrication performance in journal bearing manufacturing, employing numerical simulation techniques to investigate how manufacturing errors from processing accuracy impact lubrication behaviors. As core components in mechanical systems—especially diesel engine crankshaft bearings operating under complex conditions—journal bearings’ lubrication performance directly determines equipment stability, energy efficiency, and service life. Manufacturing deviations-induced poor lubrication can cause increased friction, severe wear, or even failures, underscoring the research’s practical value. The study constructs a refined numerical model based on the Navier-Stokes equations within the Computational Fluid Dynamics (CFD) framework, ensuring it reliably depicts fluid flow in bearing clearances. It then systematically analyzes the lubrication responses of diesel engine crankshaft bearings under diverse operational scenarios, varying key manufacturing-related parameters: roundness degrees and clearance dimensions, which mimic real production discrepancies like tool wear or machining vibration. Additionally, the research explores shaft center trajectory variations under two extreme operating conditions, as shaft movement reflects the lubrication film’s loadbearing and stability capacities. Surface roundness and clearance are identified as pivotal to journal bearing performance: they significantly alter oil film thickness distribution—critical for avoiding metal contact—and determine the maximum fluid pressure within bearings, a key load-bearing indicator. Moreover, the amplitude and phase angle of roundness fluctuations (often overlooked) exert substantial impacts on lubrication stability and load-bearing properties, offering insights for optimizing manufacturing processes to mitigate such adverse effects: -Journal bearings. -hydrodynamic lubrication. -Form error.

Liu, Jun, Liu, Deliang

Research on the Fault Diagnosis Method for Key Components of Inertial Friction Welding Equipment

2026-99-0309

8/14/2026

Inertial Friction Welding (IFW) equipment is essential for the welding process of aircraft engine shaft components. However, the absence of comprehensive fault-handling standards for domestically produced inertial friction welding equipment has hindered its further development. This study focuses on the connecting rod and motor of the 30T-IFW equipment, employing a model-based fault detection method. Through simulation, the deformation of the connecting rod and the frequency response of motor vibration acceleration under different working conditions are obtained. Additionally, a monitoring platform is proposed to collect real-time data on connecting rod deformation and motor vibration from actual welding equipment. By establishing a quantitative correlation model of connecting rod deformation-force and revealing the coupling mechanism between motor eccentricity faults and modal frequency vibrations, a hybrid diagnostic framework that combines simulation of primitive warning and measurement of calibration is proposed. At last, the simulation and experimental results verify the effectiveness of the fault diagnosis method proposed in this paper.

Yang, Haifeng, Yuan, Mingqiang, Sun, Tao, Liang, Wu, Gong, Maolin, An, Xingyi, Wang, Qisong, Liu, Dan

Design of a Four-Wheel Turning Tobacco Harvester Suitable for Hilly Areas

2026-99-0333

8/14/2026

To address the core requirement of “layered ripeness and non-destructive harvesting” in tobacco-growing hilly regions of China, a specialized tobacco leaf harvester was developed. Considering the challenges posed by scattered plots and complex terrain, a four-wheel steering chassis system was proposed. The platform adopts a four-wheel independent drive and steering (4WID-4WIS) configuration, powered by DC servo motors and integrated with a microcontroller-based ROS system. The resulting drive chain—comprising motors, gear reducers, and off-road tires—achieves a maximum operating speed of 0.5 m/s. A novel rotary cross-blade harvesting module was designed in conjunction with a conveyor-based transmission mechanism, enabling stratified harvesting and leaf transport. Full-condition field tests were conducted. In terms of mobility, the harvester achieved stable operation at 0.5 m/s on cement roads, 0.1–0.2 m/s in fields, and demonstrated slip-free climbing on 20° slopes. In terms of harvesting performance, the system’s adjustable modules accommodated varying plant heights; however, issues with blade grip were observed when handling irregularly slanted stalks, affecting collection efficiency. During continuous field entry and exit operations, no mechanical failures occurred, verifying the prototype’s operational stability. This study introduces an innovative combination of omnidirectional mobile chassis and stratified blade modules, offering technical support for the modernization of tobacco agriculture. Further refinement of the harvesting strategy will be pursued to enhance practicality.

Guo, Ting, Gu, Jin, Li, Wen, Tang, Xiaoming, Long, Chao, Yang, Dongchao

Modeling Method of Aircraft Hydraulic Pipeline Cleaning Test Equipment Based on MBSE

2026-99-0331

8/14/2026

With the continuous improvement of performance requirements for aviation equipment, the importance and complexity of hydraulic systems as the core carrier of flight control are becoming increasingly prominent. The cleanliness of aircraft hydraulic pipelines directly affects the reliability and flight safety of hydraulic systems, and it is necessary to use specialized cleaning and testing equipment during design and manufacturing to achieve efficient cleaning. The design of traditional cleaning equipment relies on experience-driven development, with mechanical, hydraulic, and electrical systems developed independently. There are problems such as unclear requirement definitions, low efficiency of interdisciplinary collaboration, and lagging validation, making it difficult to achieve the goal of forward design. Therefore, this study introduces Model-based Systems Engineering (MBSE) method in the development process of pipeline cleaning test equipment, proposes a modeling process based on RFLP (Requirements-Function-Logical-Physical), and uses SysML system modeling language to construct a top down design model system for aircraft hydraulic pipeline cleaning equipment. Through requirement analysis modeling, functional behavior definition, and system architecture design, the significant advantages of MBSE method in the development of complex aviation test equipment have been verified, effectively improving the bold design capability and top down design efficiency. MBSE method can not only improve the design efficiency of equipment, but also promote the intelligent and efficient operation of equipment, which has important significance for the development of intelligent manufacturing and electromechanical integration technology.

Zhang, Yuxin, Ma, Zichen, Li, Qi, Song, Guoqiu, Li, Haiwei, Zhang, Jingjing

Research on Asymmetric Gear Stiffness

2026-99-0332

8/14/2026

To meet the need for optimizing the dynamic performance of asymmetric gear transmissions operating under high-speed and heavy-load conditions, this study presents a refined stiffness modeling approach. A tooth-surface contact stiffness model is formulated based on Hertzian contact theory. By integrating the energy method, a coupled stiffness model is established that incorporates bending, shear, axial compression, and foundation stiffness components. Stable curves depicting the variation of mesh stiffness with the path of contact are subsequently derived by leveraging the principle of stiffness superposition. The findings demonstrate that the proposed mathematical model accurately represents the stiffness behavior of asymmetric gears as governed by the changing contact length, thereby providing a theoretical foundation for enhancing gear dynamics and extending the service life of transmission systems.

Zhao, Zeyi, Sun, Xiaoyan, Wu, Ziheng, Tang, Xin, Liu, Yanxia, Li, Fajia

Modeling and Simulation of the Quick Discharge Hydraulic System of an Internal Mixer

2026-99-0305

8/14/2026

The hydraulic system of the mechanical lever locking device of the internal mixer and the hydraulic system of the gear rack swing hydraulic cylinder are developed. The AMESim simulation models of the two systems are established, and the simulation parameters of each hydraulic element are reasonably set. Firstly, the relationship between the opening time of the mechanical lever locking device of the internal mixer and the charging volume and pressure of the accumulator is analyzed. It is found that the locking time of the mechanical lever locking device of the internal mixer needs about 10 s, while the unlocking time is less than 0.05 s. The unlocking and rubber discharging speed is very fast, and the opening time of the mechanical lever locking device of the internal mixer will become shorter when the pressure or volume of the accumulator air bag becomes larger; Through the analysis of the hydraulic system of the rack and pinion swing hydraulic cylinder, it is obtained that when the air bag volume of the accumulator is 7.557 L, the displacement of the piston rod of the rack and pinion swing hydraulic cylinder rises fastest, which is shortened from 20 s to about 15 s; The greater the air bag pressure of the accumulator is, the faster the displacement of the piston rod of the gear rack swing hydraulic cylinder rises, which is shortened from 20 s to 18 s.

Zhang, Haoqiang, Cai, Liu

Design and On-Vehicle Validation of a Clutchless Electro-Pneumatic Gear-Shifting System for a Formula Student Race Car

2026-01-5069

8/14/2026

Gear-shift execution is critical to power delivery, vehicle acceleration, and driver workload in Formula Student racing vehicles. Conventional shifting solutions for sequential gearboxes are often limited by driver-dependent operation, insufficient actuator authority, incomplete torque coordination, or the absence of closed-loop gear-state confirmation. This study develops and validates a clutchless electro-pneumatic gear-shifting system for a CF700-powered Formula Student vehicle equipped with an integrated sequential dog-engagement gearbox. The system is treated as a shift-assist form of automated manual transmission, in which the driver retains gear-selection authority while shift actuation and engine torque coordination are performed electronically. Although pneumatic shifting systems are already established in motorsport applications, the present work focuses on their vehicle-specific integration through measured shift-load characterization, geometry-based actuator design, gear-position-based closed-loop control, and electronic-throttle-assisted torque intervention. Vehicle tests were conducted under straight-line acceleration, high-speed obstacle-avoidance, and endurance-oriented training conditions. Across 76 recorded shift events, no failed gear transition or missed target-gear confirmation was observed. In straight-line acceleration tests, the mean target-gear confirmation time for recorded upshifts was 96 ± 5 ms, and the representative gear-position transition interval was approximately 20 ms. The full Engine Control Unit (ECU)-controlled upshift event was 0.50 ± 0.10 s because it included the calibrated low-torque dwell and torque-recovery phase, and should therefore be interpreted as a control-event window rather than the mechanical shift duration. After powertrain-specific actuation and torque-control calibration, the developed system provides an implementation basis for similar electronically controlled sequential-gearbox racing platforms, with potential to reduce shift time and driver workload and to support improved autocross drivability and performance.

Cao, Yuanyi