Transactions of the Canadian Society for Mechanical Engineering
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Volume 41 (2017), Issue 2
Towards understanding the influence of gradient reconstruction methods on unstructured flow simulations
Fadi Mishriky, Paul Walsh
In this paper, the formal order of accuracy of three commonly used gradient reconstruction methods is derived. The analysis showed that the Green–Gauss cell based (GGCB) method is intrinsically inconsistent, due to the leading error term that is independent of the mesh spacing. On the other hand, the Green–Gauss node based (GGNB) and the Least Squares cell based (LSCB) methods achieved a minimum of 1st order accuracy regardless of the mesh geometric properties. Implications of the former results were practically tested on four CFD applications to show that in three out of four cases, the LSCB method achieved the highest order of accuracy. In terms of the computational expenses, the GGNB method consumed 9–34% additional time when compared to the fastest converging method in each test case. Both the GGCB and the LSCB methods consumed nearly the same computational time to reach convergence.
Research on a flutter stability control measure of a fabricated steel truss bridge
He Xiaohui, Wang Qiang, Zhang Chengiong, Zhang Shunfeng, Gao Yaming
In order to improve the flutter stability of a certain type fabricated steel truss bridge, a method of setting guiding plates is proposed. Based on the two-dimensional 3 DOF coupling flutter method (2d-3DOF method), and by use of the numerical wind tunnel established by computational fluid dynamics (CFD), the flutter stability control measures of setting guiding plates are simulated. Through CFD numerical simulation, the flow field characteristics, flutter derivatives and critical flutter speed of original and guiding-plated models are obtained. It is found that for a certain type fabricated steel truss bridge, the guiding plates can improve its flutter stability. Thus, the feasibility and reliability of setting the guiding plates are proved, and the foundation for its further application in practical projects is laid.
Effect of pre- and post-weld shot peening on the mechanical & tribological properties of TIG welded aluminum 6061-T6 alloy
Anas M. Atieh, Rula M. Allaf, Abdulaziz AlHazaa, Mahmoud Barghash, Hasan Mubaydin
In this paper, the effects of shot peening on the performance of TIG welded 6061-T6 Al alloy are investigated. Six different scenarios are evaluated utilizing two levels of high/low shot peening intensities. The hardness profiles demonstrate a “W” shaped distribution, with low hardness values in heat affected zone, implying coarsening of precipitates. Except for ductility, the results indicate that all shot peening scenarios enhance the tensile properties of the welded specimens with respect to the unpeened control, with enhancements ranging from approximately 3 to 35%. Pre-weld low intensity shot peening results in the highest increase of tensile strength. The coefficient of friction ranges from approximately 0.4 to 0.9 compared to the unpeened control with a coefficient of approximately 0.6.
Design and analysis of constant-breadth cam mechanism with oscillating flat-faced follower
A simple yet comprehensive method is presented for the design and analysis of a constant-breadth cam mechanism with an oscillating flat-faced follower. In the proposed approach, the kinematic characteristics of the cam mechanism are first derived. The cam profile is then designed using homogenous coordinate transformation and conjugate surface theory. Moreover, the sliding velocity at the cam-follower contact points is determined. Finally, the pressure angle of the constant-breadth cam mechanism and the principal curvatures of the cam are analyzed. The validity of the proposed design methodology is verified by means of motion simulations performed using CAD software.
Development and optimization of a linear-motor-driven water hydraulic piston pump
Huang Ye-qing, Nie Song-lin, Ji Hui, Nie Shuang
This research develops a new piston pump driven by four double-action linear motors (abbr. FDLMP). The working principle of FDLMP is introduced, and the theoretical models of flow rates, effects of motion planning, and hysteresis of flat valve on pulsation ratio of combination flow rate of the piston pump are investigated systematically. The simulation and test results showed that the key design parameters such as the clearance of piston sector, spring preloading and stiffness of suction valve play important roles in the improvement of volumetric efficiency and flow pulsation rate of FDLMP. These research works lay the foundation for the further development of FDLMP.
Thermal barrier coating and turbulence intensity effects on leading edge cooling conjugate heat transfer analysis
Prasert Prapamonthon, Huazhao Xu, Zhaoqing Ke, Wenshuo Yang, Jianhua Wang
This is a numerical study of thermal barrier coating (TBC) and turbulence on leading edge (LE) cooling of a guide vane. Numerical results were carried out using 3D CFD with conjugate heat transfer analysis. Important phenomena were revealed. (1) TBC is effective in the LE region especially when free stream turbulence (Tu) increases. (2) At each Tu, TBC near the hub of the vane provides the most effective protection and at the highest Tu, TBC improves overall cooling effectiveness there by about 25%. (3) Near the exits of film hole, TBC may have negative effect, because of heat transfer impedance from the solid structure into the mixing fluid between mainstream and cooling air emitted from film holes.
Influence of external particles of heterogeneous condensation flow in cascades
Xu Han, Zhonghe Han, Peng Li
The wet steam nucleation zone is usually concentrated in the lower part of the throat. A double fluid numerical model and a shear stress transport (SST) k-ω-kd two-phase turbulence model were derived for the heterogeneous condensation flow of wet steam. The effect of the particle parameters on the condensation flow and the varying patterns of the nucleation rate and degree of super-cooling were investigated. The results show that external particles have a significant influence on the condensation flow, which weakens the condensation wave, restrains the development of thermodynamic imbalance and improves the flow conditions in the cascade.
A study on the improvement of meshing characteristics of a complementary curvilinear gear set generated by complementary back cutters
Yi-Cheng Chen, Zhi-Wei Li, Chien-Cheng Lo, Zhi-Gen Wang
This article focuses on improving the meshing characteristics of a complementary curvilinear gear set generated by complementary rack cutters. Firstly, the mathematical model of a complementary curvilinear gear set was developed based on the theory of gearing. Tooth contact analysis (TCA) was conducted to explore the influences of assembly errors on the transmission error (TE) and contact pattern. A stable point contact was successfully introduced to replace the original line contact in the improved complementary curvilinear gear set, resulting in less sensitivity to assembly errors. Finally, finite element analysis (FEA) was also utilized to calculate contact stress of the original and improved complementary curvilinear gear set.
The effects of inlet air quantity and inlet oxygen mole fraction on the combustion and fluid flow in a sulfur recovery unit thermal reactor
Owing to the high temperature inside a sulfur recovery unit (SRU) thermal reactor, detailed experimental measurements are difficult. In the author’s previous studies, several methods have been assessed to resolve the abnormality of the SRU thermal reactor under high temperature operation. This paper presents a new easier and more economical method. The effects of inlet air quantity and inlet O2 mole fraction on the combustion and fluid flow in a SRU thermal reactor are investigated numerically. The flow field temperature, S2 recovery, H2S mole fraction, and SO2 emissions are analyzed. This paper provides a guideline for adjusting the inlet air quantity and the inlet O2 mole fraction to reduce the high temperature inside a thermal reactor and to ensure an acceptable sulfur recovery.
The influence of medial-lateral contact pair conformity on contact stresses in total knee replacement
Usman, Shyh-Chour Huang
Eleven finite element models representing the medial-lateral conformity level and shape have been analyzed. From the result, we concluded that the flat-on-flat contact model of knee joint replacement was the most vulnerable to damage. Moreover, in the flat-on-flat model, the highest von Mises stress occurred at two points in a model, namely at the medial and lateral edge of the contact area. With respect to the sensitivity of the contact stresses to the conformity (frontal clearance) in the curved-on-curved model, the larger radius of the femoral indenter showed more contact stress sensitivity to the change in conformity. The von Mises stress dropped to almost half of its previous value when the frontal clearance decreased from 10 to 2 mm.
Design optimization of vertical needle geometry for bump water-level probing
Te-Ching Hsiao, Shyh-Chour Huang, Hao-Yuan Chang
The purpose of this paper is mainly to develop a method to use the Taguchi method with the L18 (21 × 37) orthogonal array to obtain an optimal geometrical design of the vertical probing needle and base on various criteria to minimize the stress on the probing needle during wafer-level probing test. Furthermore, importance of the factors on the probing mark area ratio was also ranked. The results shows that as probe length, offset, and lower die gap increase, stress on the probing decrease. On the contrary, vertical probe bends decrease, stress on the probe increase. Furthermore, the body of vertical probe with rectangle crosssection is better than square and circular sharp.
An integrated numerical and experimental investigation on improving acoustic and cooling performance of a high power motor
Sheam-Chyun Lin, Ming-Chiou Shen, Chen-Min Li, Fu-Yin Wang, Hung-Cheng Yen
This research focuses on noise reduction of a 175-Hp motor under the same cooling need. First, the electromagnetic field is calculated numerically to provide the total losses to be 5.7 KW. Later, based on the numerical predication, the appropriate design, which consists of an inline fan rotor with a 2-cm diameter reduction and a streamlined housing, successfully reduce the noise by 3–5 dBA over various locations under the 3,000 rpm. Furthermore, the motor mockup is manufactured for testing, and result indicates that a similar noise reduction (4–7 dBA) is obtained while an acceptable deviation range between CFD and test results is observed. Consequently, this design and analysis tool offers a rigorous and systematic scheme for the thermal management on the high-power motor.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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