• Structural Engineering and Mechanics
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• 제90권1호
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• pp.97-106
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• 2024

This paper presents a significant contribution to aided design by conducting an analytical examination of geometric links with the aim of establishing criteria for assessing an analogy measure of the extrinsic geometric and kinematic characteristics of the Variable Compression Ratio (VCR) engine with a Geared Mechanism (GBCM) in comparison to the existing Fixed Compression Ratio (FCR) engine with a Standard-Reciprocating Crankshaft configuration. Employing a mechanical approach grounded in projective computational methods, a parametric study has been conducted to analyze the kinematic behavior and geometric transformations of the moving links. The findings indicate that in order to ensure equivalent extrinsic behavior and maintain consistent input-output performance between both engine types, precise adjustments of intrinsic geometric parameters are necessary. Specifically, for a VCR configuration compared to an FCR configuration, regardless of compression ratio and gearwheel radius, for the same crankshaft ratios and stroke lengths, it is imperative to halve lengths of connecting rods, and crank radius. These insights underscore the importance of meticulous parameter adjustment in achieving comparable performance across different engine configurations, offering valuable implications for design optimization.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.549-553
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• 2007

Moving parts of the rotating and reciprocating mechanism are the most important components of the diesel engines and require very high reliability in their design. Especially the crankshaft, the key component of running gear (powertrain), is subject to complicated loadings such as bending, shear and torsion coming from firing pressure, inertia forces and torsional vibration of crankshaft system. Intrinsically they show different cyclic patterns of loading in both direction and magnitude, and thus ordinary approach of proportional loading is less valid to analyze the dynamic structural behavior of crankshaft. In this paper, new fatigue analysis method is introduced to analyze and design the crankshaft of a medium-speed diesel engine in order to consider the non-proportional multi-axial loads realistically as well as to present the general fatigue analysis approach for an engine crankshaft.

• Tribology and Lubricants
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• 제11권5호
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• pp.162-171
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• 1995

The application of reciprocating engine crankshaft bearings is of particular importance and interest among the plain bearing, not only because the sheer volume of intemal combustion engines now produced, but because the severe operating conditions they are subjected to. Demands for better performances of crankshaft bearings have provide an important impetus in the development of bearings and bearing materials. As engine design progresses toward higher outpt and higher efficiency, crankshaft bearings must perform under more seveve operating conditions. Higher load, temperature, and speed as well as lower viscosity oil are applied to the bearing sysem, resulting in a smaller minimum oil film thickness. This means more solid-solid contact between the shaft and bearing, and the bearing is exposed to more danger of seizure. Some engines may experience bearing seizure problems. However, understanding about the seizure behavior and mechanism is far from being enough. Seizure resistance of a bearing-shaft system will be affected by the properties of the shaft and bearing, especially their materials and surface texture. Commonly used engine bearing materials include Al-Pb-Si, Al-Sn-Si, Al-Sn, and Cu-Pb with Pb-Sn-Cu overlay. These materials have very different properties. They showed different behaviors dering seizure tests and seizure may occur with different mechanism for different bearing material. Shaft materials also affect the seizure resistance of the system. Surface texture of the bearing and shaft have apparent effects on the lubrication and solid-solid contact pattern, and therefore will affect the seizure behavior of the system. Bearings and shafts which are made of different materials and have different surface textures have been tested and analyzed. Their effects on seizure resistance are discussed and possible seizure mechanisms for different beatings are presented in this paper.

• 소음진동
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• 제10권3호
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• pp.465-473
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• 2000

In this crankshaft of marine diesel engines the exciting torques are produced by gas pressure and reciprocating masses. These torques are periodically changing and are extremely out of balance. To calculate the torsional vibrations of propulsion shafting caused by unbalanced torque the torque harmonics are utilized. Until now to calculate the torsional vibrations of propulsion shafting. the torque harmonics have been supplied by the engine maker. When the torque harmonics of an engine are not available the torque harmonics of a similar engine type had to be used. However such data is not suitable for the reliable calculations of torsional vibrations. In this paper the combustion characteristics of marine diesel engines including $\rho{-}\upsilon$ diagram are investigated and the torque harmonics based on these are theoretically calculated. reliability of the calculations is confirmed by comparing them with those of an engine maker. This study should prove useful for the calculations of torsional vibrations for diesel engine propulsion shafting. particularly for 4-stroke engines whose torque harmonics are difficult to obtain directly from the engine and not ordinarily supplied by the engine maker.