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Bearings and Lubrication
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The effects of varying dimensions and clearance ratios are very significant in a bearing design. The radial clearance c (Figure 10.10) is contingent to some extent on the desired quality. Suitable values to be used for radial bearing clearance rely on factors that include materials, manufacturing accuracy, load-carrying capacity, minimum film thickness, and oil flow. Furthermore, the clearance may increase because of wear. The clearance ratios (c/r) typically vary from 0.001 to 0.002 and occasionally as high as 0.003. It would seem that large clearances increase the flow that reduces film temperature and hence increase bearing life. However, very large clearances result in a decrease in minimum film thickness. Therefore, some iteration is ordinarily needed to obtain a proper value for the clearance.
Bearings and Lubrication
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, MECHANICAL DESIGN of Machine Components, 2018
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The effects of varying dimensions and clearance ratios are very significant in a bearing design. The radial clearance c (Figure 10.10) is contingent to some extent on the desired quality. Suitable values to be used for radial bearing clearance rely on factors that include materials, manufacturing accuracy, load-carrying capacity, minimum film thickness, and oil flow. Furthermore, the clearance may increase because of wear. The clearance ratios (c/r) typically vary from 0.001 to 0.002 and occasionally as high as 0.003. It would seem that large clearances increase the flow that reduces film temperature and hence increase bearing life. However, very large clearances result in a decrease in minimum film thickness. Therefore, some iteration ordinarily is needed to obtain a proper value for the clearance.
Principles of Energy Conversion
Published in Hamid A. Toliyat, Gerald B. Kliman, Handbook of Electric Motors, 2018
Hamid A. Toliyat, Gerald B. Kliman
The construction differences between horizontal and HiThrust vertical motors are primarily dictated by the differences in radial bearings from thrust bearings. Radial bearings are designed to handle primarily radial loads. The deep-groove ball bearing is a modification capable of handling moderate axial loading. A thrust bearing is designed to handle axial thrust load in only one direction and radial loading which is small compared to the axial load.
Design and analysis of bionic cobweb Umbrella-Type deployable mechanism
Published in Mechanics Based Design of Structures and Machines, 2023
Jianwei Sun, Haoran Zhao, Wenrui Liu, Jinkui Chu
Figure 3(a) shows a unit of the cobweb structure model. The model consists of a center, a radial thread, and three-layer spiral threads. Based on the structural unit, a planar four-bar crank slider mechanism with a common slider was designed. As an expandable unit, the mechanism is composed of a common frame with two planar four-bar crank slider mechanisms. As shown in Figure 3(b), two crank slider mechanisms have a common frame AC. The crank corresponds to the radial thread in the cobweb structure, and the connecting rod corresponds to the spiral thread. Mechanisms AB1C and AB2C share the slider. As the sliding block slides on the support rod, the folding and unfolding processes of the deployable unit were realized. The kinematic chain of the deployable unit mechanism in Figure 3(a) includes five movable members, six rotating pairs, and one sliding pair. Based on the composition of the mechanism, the number of degrees of freedom of the mechanism can be determined as follows: where n represents the number of movable links, and pl represents the number of lower pairs.
Sealing reliability and reliability sensitivity analysis of the piston–cylinder bore friction pair in a hydraulic pump under incomplete probability information
Published in Mechanics Based Design of Structures and Machines, 2023
The working volume formed by the hydraulic pump piston and the cylinder bore changes periodically. In each cycle, when the working volume increases, it corresponds to the oil suction process; when the working volume decreases, it corresponds to the oil pressing process. When the hydraulic pump piston and the cylinder bore are working, a friction pair will form between the relatively moving piston and cylinder. A radial force will be transmitted between the piston and the cylinder through the cylindrical surface of the piston. The force analysis schematic diagram of the piston is shown in Figure 2, where the forces acting on the piston include: (1) Axial hydraulic pressure force, (2) axial motion inertial force, (3) centrifugal reaction force, (4) swashplate reaction force, (5) contact forces, and and (6) friction forces, and
Performance and combustion characteristics of a retrofitted CNG engine under various piston-top shapes and compression ratios
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Anh Tuan Le, Dang Quoc Tran, Thanh Tam Tran, Anh Tuan Hoang, Van Viet Pham
When the cylinder head or piston-top surface is not flat but is shaped such as bowl-in-piston combustion chamber, this piston-generated axial flow, during compression stroke and expansion stroke, produces radial or transverse flows due to variances in the axial gap between the cylinder head and piston-top surfaces across the cylinder cross-section, these flows are called squish. In short, squish is the transverse or radial mixture motion that happens toward the end of the compression stroke and the beginning part of the expansion stroke, when a portion of the piston-top and cylinder head approach (or separate from) each other closely. Figure 3 indicates how mixture is thereby moved into the open region of the combustion chamber at the end of compression process. The amount of squish is strongly affected by the proportion of the squish area and the cylinder cross-section area.