• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2000.11a
• /
• pp.108-114
• /
• 2000

The excitation forces from the periodical firing pressure in cylinder and the rotating crank mechanism cause lots of vibration problems in diesel engine. In this paper, the theoretical formulas for excitation forces are introduced and computational program for the optimization of crank angle is also developed to reduce the free moments in diesel engine. The computational results of 4-stroke in-line engine are applied to verify the reliability of the program.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.1018-1025
• /
• 2003

The diesel engine is often a serious excitation source in ships. Both the varying cylinder gas forces and the reciprocating and rotating mass forces associated with the crank and the connecting rod mechanism produce ample possibilities for excitation of the engine structure itself, the shafting, the surrounding substructures as well as the hull girder. This paper presents a guide for optimization of excitation forces produced by the marine propulsion 2-stroke diesel engine. The computational program for predicting the excitation forces is developed and applied to 2-stroke in-line engines. The object function is defined as the work done by every cylinder excitation force which is related to the mode shape of the diesel engine system, especially in the torsional vibration of the shafting. As a practical application of the presented method, the crank angle of 7 cylinder 2-stroke engine is optimized to reduce torsional vibration stresses on the shafting. Compared with the regular firing angle, about 60% of the 4th order torsional vibratory stress on the propeller shaft can be reduced by optimizing the crank angle irregularly. The usefulness of the presented optimization method is confirmed by the measurements.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.8
• /
• pp.709-717
• /
• 2004

The diesel engine is often a serious excitation source in ships. Both the varying cylinder gas forces and the reciprocating and rotating mass forces associated with the crank and the connecting rod mechanism produce ample possibilities for excitation of the engine structure itself, the shafting, the surrounding substructures as well as the hull girder. This paper presents a guide for optimization of excitation forces produced by the marine propulsion 2-stroke diesel engine. The computational program for predicting the excitation forces is developed and applied to 2-stroke in-line engines. The object function is defined as the work done by every cylinder excitation force which is related to the mode shape of the diesel engine system, especially in the torsional vibration of the shafting. As a practical application of the presented method. the crank angle of 7 cylinder 2-stroke engine is optimized to reduce torsional vibration stresses on the shafting. Compared with the regular firing angle, about 60 ％ of the 4th order torsional vibratory stress on the propeller shaft can be reduced by optimizing the crank angle irregularly. The usefulness of the presented optimization method is confirmed by the measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.10a
• /
• pp.792-796
• /
• 2013

A practical process to optimize engine mounts on construction equipment is presented in this research. Transmitted force from the engine is estimated by using stiffness of the mount rubber which varies with frequency, amplitude and pre-load, and by the engine excitation force that comes from piston mass and gas pressure and so on. The transmitted force is measured through TPA(Transfer Path Analysis) and is then compared with the estimated force. The optimum mount position and stiffness are solved using MATLAB. The result shows the improvement on engine mount vibration.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.3
• /
• pp.1-7
• /
• 2007

Torque fluctuation of an engine and angular velocity variation of a propeller shaft are the main excitation sources in a vehicle driveline. This paper presents the mechanism of these excitation sources. An equivalent model of the engine system and propeller shaft system is constructed to simulate the excitation phenomena. The analytical model contains the geometrical and dynamic mechanism. Combustion pressure of the cylinder is measured from dynamometer. The computer simulation is carried out by commercial program package. Results of the simulations show the characteristics of the torsional excitation source of the driveline.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.654-657
• /
• 2014

In this paper, we study the analytical method to predict the excitation forces for the engine system. The engine system on the construction equipment is one of the important power sources, and the characteristics of the engine decide the performance of noise and vibration for the equipment. We predict the excitation forces using the geometrical data of the crank system and the combustion pressure in the cylinder. The excited forces are represented by the torque fluctuation above the center of the crank shaft.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11a
• /
• pp.213-218
• /
• 2001

A magnetorheological(MR) engine mount for a passenger vehicle and its vibration control performance is experimentally evaluated. A mixed-mode model for the MR engine is derived by incorporating Herschel-Bulkely model of the MR fluid. After analyzing the field-dependent damping force, a appropriate size of the MR engine mount is manufactured. The field-dependent is displacement transmissibility of the engine mount is evaluated in the frequency domain at various excitation levels. In addition, time-dependant damping force is experimentally investigated by changing the excitation amplitude.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.5
• /
• pp.129-137
• /
• 2000

The powertrain is an important factor for the interior and exterior noise behavior of the vehicle Thus, the noise vibration and harshness(NVH) behavior of an engine is becoming a major target of the powertrain development. This paper describes the analyses with the aim to reduce the vibration and noise of an advanced inline 4-cylinder diesel engine block by use of CAE methods. The characteristics of an engine block as a main excitation source of car interior noise is studied. Particularly, The effect of balance shaft to reduce the 2nd order engine excitation force is calculated by forced vibration and radiated noise analysis. The engine exitation forces are obtained under real operating conditions. It is shown that the reduction of vibration and noise level by adapting blancing shaft is well predicted and rediated noise is directly related to the surface velocity of engine block.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.840-843
• /
• 2006

The determination of firing order is very significant procedure in initial stage of design for medium speed diesel engine. Generally, the selection of firing order has been accomplished in view of minimum excitation forces condition. In this paper all possible firing orders under the given number of cylinder were considered to decide the optimum. Meanwhile torsional vibration characteristics using the phase vector sum method and minimum excitation force concept were applied. From these results, some superior cases were selected. And then, the torsional vibration response analysis and the resonance characteristics of engine structure were investigated for the final decision.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.912-918
• /
• 2004

Main vibration problems of a transaxle type forklift truck are caused by the resonance of engine excitation force and natural mode shade of major components such as engine-mount system, mast, and main frame. But, it is well known that the reduction of vibration is very difficult because of the limitation of structural modifications. In this paper, the vibration characteristics of engine-mast system including engine mount were firstly identified by the experimental and simplified numerical methods. And also, the free and forced vibration characteristics of a whole forklift truck were surveyed with modal test and ODS(operation deflection shape) measurement. Based on these results, the reliable finite element model was developed. Finally, various countermeasures were considered and applied to a real forklift truck and then its effects were confirmed.