Mechanics

Numerical Study of Particle Impingement on Aeroengine under Mixed-Phase Conditions

Qilei GUO — 2024-10-30

In this approach, considering to ice crystal sticking effects, a numerical model was established to solve the particle impingement property of a large bypass ratio aeroengine under mixed-phase icing conditions. The collection efficiency of droplets obtained by the proposed model is are well in agreement with the literature and the collection efficiency of ice crystals is significantly higher than that of droplets due to the greater inertial force. The mechanism of liquid film acting on the ice crystal adhesion affect was investigated. It is found that the greater melt ratio can lead to more sufficient liquid water and more extended wetting limit, which have more significant capability of sticking ice crystals. Meanwhile, due to ice crystals subjected to centrifugal force, the sticking coefficient of ice crystal will cliff-like drop, and the cliff-like effect is more pronounced accompanied by the greater centrifugal force.

Performance of a Small Hydrodynamic Journal Bearing Involving Adsorbed Layer and Surface Elastic Deformation

Shuxiong XIAO — 2024-10-30

The load and friction performances of a small elastohydrodynamic journal bearing with the shaft radius 1mm have been computationally studied. The effect of the adsorbed layer is incorporated and the multiscale hydrodynamic flow theory is used. It is shown that the multiscale performance of this bearing occurs in the wide eccentricity ratio range from 0.3 to nearly unity because of the influence of the adsorbed layer, and thus the generated pressures and carried load of this bearing are significantly greater than the classical hydrodynamic theory calculations. The effect of the adsorbed layer is more stronger for rigid bearing surfaces than for elastic bearing surfaces especially for a strong fluid-bearing surface interaction, and it is strong for the high eccentricity ratios over 0.9. In this bearing, when the effect of the adsorbed layer is incorporated, the friction coefficients on both bearing surfaces are reduced in the wide eccentricity ratio range as compared to the classical calculation; Stronger the fluid-bearing surface interaction, greater the reduction of the friction coefficient, showing the pronounced non-continuum effect of the adsorbed layer. However, for elastic surfaces the friction coefficient is a bit higher than that for rigid surfaces especially for high eccentricity ratios and strong fluid-bearing surface interactions.

Evaluation of Energy Conversion and Distribution on the SI-PFI Engine Fueled by A Gasoline-Bioethanol Blend with AFR Variations

Marthen PALOBORAN — 2024-10-30

This study aims to investigate the engine performance of spark-ignition engines with port fuel injection using E50 fuel, which contains 50% gasoline or pertalite (in Indonesia) and 50% hydrate bioethanol, at air-fuel ratio variations of 10:1, 12:1, and 14:1. The experiments were conducted using a 1-cylinder, 662 cc engine research test with a constant load of 3 kg and engine speed variations of 1500 and 1800 RPM, as well as a compression ratio of 10:1 and standard ignition timing. The engine ran with E50 fuel, and the experimental results were compared with those of E0 for an air-fuel ratio of 14:1. According to the data, the fuel energy of E50 in an AFR of 14:1 is 0.11 kW higher than that of E0, and it increases by 21.6% when the engine speed increases from 1500 to 1800 RPM. The results also indicate that the efficiency of all performance indicators, such as indicative thermal efficiency, brake thermal efficiency, and mechanical efficiency, is maximized when the engine is operated at an AFR of 10:1 for E50 fuel. Additionally, the volumetric efficiency of E50 reaches its maximum when the fuel is burned at an AFR of 14:1, and it increases as the engine speed increases. However, it should be noted that the brake power decreases due to the frictional power of the fuel increase.

Performance Evaluation of Directional Porous Oil Storage Medium Fabricated by PTFE and Naphthalene

Haiyong WU — 2024-10-30

Porous oil storage media is the core of self-lubricating rolling functional components. The internal pore directivity of porous oil storage media is different，and it reduces the utilization rate of lubricating oil. In this paper, a new fabrication method of porous oil storage media with directional pores is carried out, and the properties of the porous media, such as hardness, density, porosity, oil storage rate and oil retention rate are evaluated. The experimental results show that the fabrication pressure has a linear positive effect relationship with the hardness of the porous media, and has no significant effect on the density, porosity, oil storage rate and oil retention rate. The mass fraction of pore former has a linear negative effect relationship with the hardness and density of the porous media, and a linear positive effect relationship with the porosity the greater the mass fraction of pore former, the greater the initial oil seepage rate of oil rejection. The internal pores of the porous media have a fibrous structure of the karst cave type, and the internal pores are interconnected and have good orientation. This study aims to provide a lubricating theoretical reference for the fabrication of porous oil storage media.

The Analysis and Compensation Experiment of Linear Feed Axis Positioning Error Based on Matrix Operation

Bo YU — 2024-10-30

The positioning accuracy of the linear feed axis is a key factor affecting the machining accuracy of CNC machine tools. The generation process of the positioning error of the linear feed axis is expounded. The Z axis of the vertical linear feed axis of the machining center is the research object, the positioning error analytical matrix is established, and the positioning error calculation of the Z axis of the vertical linear feed axis is completed based on the principle of solving the inhomogeneous linear equation. The positioning error detection of the vertical linear feed axis Z axis of the CNC machining center is carried out. Based on the characteristics of the error detection data, an error compensation model is constructed. , the variance of the positioning error detection point after compensation is reduced to 1.562, which meets the needs of precision machining.

Loading and Friction of Elastoplastic Line Contact with Thermal Deformation

Zhipeng TANG — 2024-10-30

The loading and friction of the elastoplastic line contact in boundary lubrication is studied by accounting for the
contact thermal deformation effect. When the contact is
mainly in the elastic deformation, the contact thermal
deformation has significant influences on both the contact width and contact friction coefficient for a given load, and it reduces their values; However when the contact is
mainly in the plastic deformation, the effect of the contact thermal deformation is weak or even negligible. Owing to the contact thermal deformation, the critical load for the initiation of the contact plastic deformation is also reduced.

Stress Analysis of Vibrating Screen Side Plate based on Elastic Theory

Zongpeng ZHANG — 2024-10-30

To achieve a more precise understanding of the stress distribution state of the side plate and support beam of the shaker box, a mechanical model for plane stress distribution has been established. This model is based on the plane stress theory of elastic theory. Furthermore, using this model, we have predicted the plane stress distribution of the shaker box's side plate and support beam when subjected to excitation forces generated by both unilateral and bilateral rotor arrangement structures. The findings indicate that the mechanical model rooted in elastic mechanics accurately depicts the stress distribution within the perforated side plate structure and screen support beam. Specifically, the peak stress in the side plate of a symmetrically distributed structure is merely half of that observed in a unilateral structure. Furthermore, the cumulative effect of shear stress on both sides of the side plate serves to mitigate the overall shear stress on the plate. Additionally, the planar stress within the support beam is exclusively influenced by the excitation force exerted by the vibrating screen on a single support beam.

A New Two-Phase Design Process for a Compliant Mechanism Gripper

Gopal VIJAYAN — 2024-10-30

The structural design of the components with high accuracy and controllable motion is the focus of precision industries. As a result, researchers found that components created via compliant mechanisms were much preferable. Monolithic structures known as compliant mechanisms allow motion to be achieved without the need of traditional joints. The compliant mechanisms make it easier to build microscale devices because they do not have hard junctions. In this study, a novel two-phase design methodology for compliant mechanism forceps is proposed. In order to eliminate high-stress areas, forceps are often constructed as a distributed compliant mechanism. To offer a distributed planar design, topological optimization is introduced with new approach. Design domain introduced with pattern of holes restricts the single point contact formation and large area formation which yield distributed compliant mechanism. The parametrization technique is implemented to convert the conceptual design to working design. The design of compliant forceps is assessed using finite element analysis (FEA) based on structural considerations. Finally, a handle-equipped microgripper prototype has been developed. Experimental verification demonstrates the gripper's performance and variation is less than 3% with numerical results. Integerated force sensor measure the gripping force and compared the reaction force estimated through FEA.

Effect of Elements Connection Types on Mixing Performance of Kenics Static Mixer

Zhijun LI — 2024-10-30

In this work, we analyzed the influence of four connection types of Kenics static mixer, namely direct connection static mixer (DSM), transition blade static mixer (TSM), plug-in static mixer (PSM) and solder joints static mixer (SSM) on the mixing performance. The effects of transition blade diameter, groove depth and solder joint diameter on segregation scale (S) and pressure drop (Δp) were studied. The results indicated that a better mixing performance and Δp were found in the mixers of DSM and three other small-sized connection types. The smallest Δp of 1.29 MPa were found in DSM, TSM3 and SSM2. The smallest S of 0.101 mm were found in PSM0.5. In addition, Δp and S increased as the connection size increases, in TSM, PSM and SSM. The agglomeration of particles was obvious in TSM and PSM with large connection sizes, but not in SSM.

Using of Grasshopper Optimization Algorithm Approach for Optimal Weight Design Problem of the Spur Gear

Harun GÖKÇE — 2024-10-30

Gears are undoubtedly the most important parts of motion transmission. One way to increase the motion performance of the system is to reduce the weights of the gears without sacrificing the strength capability. Today, various optimization techniques that rely heavily on analytical and heuristic approaches are used for this problem. In this study, the gear optimization problem in accordance with the minimum weight was solved with Grasshopper Optimization Algorithm (GOA). Introduced in recent years, GOA is a meta-heuristic optimization technique that stands out with its successful performance in engineering applications. This approach was used in a spur gear formation case as per the minimum weight for the first time. Compared to previous studies, the results obtained in this paper show that it is possible to design a lighter gear with GOA.

Structure Analysis for Plate Components Using an Advanced Boundary Element Method

Yudong ZHONG — 2024-10-30

Accurate and effective evaluation of physical variables is of great significance to the design safety and stability of plate structure. In this paper, an advanced boundary element method is developed to perform the structure analysis for plate components. The method is implemented as follows: Firstly, a novel interpolation method is developed to improve the simulation accuracy of the physical quantities on various structural models of plate components, which can improve the order of interpolation polynomials without changing the degrees of freedom of system equations, and eliminate the influence of the fitting error of physical variable in integral equation; And then an integral transformation frame is employed to remove the influence of the singular and nearly singular integrals in integral equation and ensure the accurate calculation of elastic parameters of plate components; Finally, several numerical examples (a porous plate, a deck framing and a propeller structure are included) are given to verify the feasibility of the proposed method. The results show that the proposed method can accurately evaluate the physical variables of the plate components.

Elasticity study of SLA Additively Manufactured Composites

َAlireza SHAHIDI — 2024-10-30

This study investigates the mechanical properties of ceramic and photopolymer composites created using stereolithography (SLA) 3D printing. It aims to evaluate and compare the performance of two SLA materials: Liqcreate Composite-X and Phrozen's Water-Washable Resin, using dynamic flexural vibration tests to determine Young's modulus. Liqcreate Composite-X, a photopolymer resin with excellent mechanical properties, including high tensile and flexural strength, showed a first resonance frequency of 318 Hz and a Young's modulus of 0.93 x 10¹⁰ Pa. Phrozen's Water-Washable Resin, designed for easy post-processing, had a first resonance frequency of 210 Hz and a Young's modulus of 0.30 x 10¹⁰ Pa. In conclusion, Liqcreate Composite-X demonstrates superior mechanical performance, making it suitable for high-strength applications, while Phrozen's Water-Washable Resin, with lower mechanical properties, is more suited for less demanding uses. This study enhances the understanding and application of SLA-based ceramic composites in various engineering domains.