• The Journal of the Acoustical Society of Korea
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• v.22 no.2
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• pp.104-112
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• 2003

The in-duct acoustical sources of fluid machines are often characterized by the source impedance and strength using the linear time-invariant model. However, negative resistances, which are physically unreasonable, have been found throughout various measurements of the source properties in IC-engines and compressors. In this paper, the effects of the time-varying nature of fluid machines on the source characteristics are studied analytically. For this purpose, the simple fluid machine consisting of a reciprocating piston and an exhaust is considered as representing a typical periodic, time-varying system and the equivalent circuits are analyzed. Simulated measurements using the analytic solutions show that the time-varying nature in the actual sources is one of the main causes of the negative source resistances. It is also found that, for the small magnitude of the time-varying component, the source radiates large acoustic power if the piston operates at twice the natural frequency of the static system. or integral submultiples of that rate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.415-416
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• 2002

Experiments have been conducted to investigate scuffing mechanism in oil lubricated piston-ring /cylinder sliding contacts. Samples were extracted from actual components to simulate the real contact geometry and other influencing conditions. A standard test machine. with some modifications, has been used for the investigation of the effects of surface temperature load and sliding velocity. preliminary tests were carried out to find the critical temperature of scuffing using gradient temperature under a constant load, reciprocating frequency and stroke. The experimental and analytical results show that a transition from lubricated contact to adhesion, accompanied by the phenomena such as material transfer between the two sliding surfaces, local contact welding and temperature rise, and sharp increase in friction coefficient, appears to contribute to the final failure of scuffing.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1031-1036
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• 2007

Torsional vibration analysis is necessary at design stage to ensure the reliability of a system particularly when the driven machine is a reciprocating compressor. This paper contains the results of torsional vibration analysis and fatigue strength evaluation for 540 kW compressor driving motor. Torsional vibration analysis showed that the $2^{nd}$ torsional mode of the entire shaft system has the possibility of resonance with the $14^{th}$ order excitation of compressor and twin line frequency of motor at operating speed. Therefore, the analyses were required to ensure the structural reliability of the motor. The fatigue strength was evaluated for the shaft and inner fans using the results of forced vibration analysis. It is concluded that the motor has sufficient fatigue strength under normal operating condition.

• Tribology and Lubricants
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• v.25 no.2
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• pp.125-131
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• 2009

Biodiesel produced from triglyceride which is main component of animal fats and vegetable oils by methanolysis was known for excellent lubricity. In this study, the lubricity of 12 kinds of biodiesel come from vegetable oils were analyzed using HFRR(High frequency reciprocating rig). The biodiesel synthesized from soybean oil has best lubricity by $153{\mu}m$ of wear scar in HFRR and used fried oil's biodiesel has slightly low lubricity by $299{\mu}m$. Also we have found that the lubricity of diesel was improved when mixing ratio of soybean biodiesel was increased in base diesel.

• Journal of KSNVE
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• v.9 no.1
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• pp.42-48
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• 1999

In this paper, a computer simulation method for dynamic analysis of the hydraulic engine mount system is proposed. The hydraulic engine mount system controls the damping characteristics using the viscosity of fluid flow The complex stiffness of the main rubber of the hydraulic engine mount system is computed by finite element analysis for the viscoelastic materials and hydro-static elements. A numerical analysis method is presented to solve nonlinear equations of the hydraulic engine mount system. which is composed of an engine mass, fluid in inertia track and a vertical inertia force of reciprocating mass in the engine. Also. dynamic properties of the hydraulic engine mount system are analyzed in the frequency domain. Effects of the hydraulic engine mount system running over the rough road are investigated using a vehicle dynamic model. These results are compared with those of the rubber mount system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.824-829
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• 2002

Since many reciprocating and rotating components are attached to jet loom structure. it is exposed to a more vibration and moise problems than the other textile machinery. Thus the design of the jet loom frame is very important to characterize the dynamic response. In this study, a finite element model of jet loom main frame was developed to investigate the dynamic characteristics of jet loom. Two different finite element models of different main frames were constructed and these models were validated by the experimental results. Dynamic characteristics such natural frequencies and mode shapes were in good agreement between the finite element analysis and experimental results within 10% error range. It is expected that the result from this study can be used as the basic information of jet loom dynamic analysis and be extended for further analysis of forced response case.

• Tribology and Lubricants
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• v.26 no.3
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• pp.190-198
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• 2010

GTL(gas-to-liquid) fuel produced by the Fischer-Tropsch process using carbon monoxide(CO) and hydrogen(H2) is expected to be one of the environmental friendly fuel for alternative and blended to petrodiesel. But GTL have poor lubricity due to paraffin as main component of GTL which is not involve polar materials. In this paper, we had investigated the lubricity improvement of GTL fuels with various lubricants using HFRR(high frequency reciprocating rig).

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.45-51
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• 2000

Investigators who study on combustion in the cylinders of reciprocating piston type internal combustion engines have been encountered embarrassments due to the difficulties of adjusting specific parameter without interfacing other parameters such as cylinder wall temperature composition of gas in the cylinder existence of cylinder lubricant etc. Rapid compression-expansion machine the position and speed of piston of which are able to be controlled by means of a system controlled electrically and speed of piston of which are able to be controlled by means of a system controlled electrically and actuated hydraulically could be utilized as one of the most preferable countermeasures against those difficulties. Several units of rapid compression-expansion machines were developed but the speed up of frequency of piston movement still is the problem to be improved to cope with actual speed of internal combustion engines. Authors designed and manufactured a new rapid compression-expansion machine electrically controlled hydraulically actuated and computer programed and then examined the performance of one. Results of a set of experiments revealed acquirements of certain improvement of frequency of piston movement preserving the stability of system response and reproducing accurate compression ratio of cylinder those are the key function for the in-cylinder combustion experiments of internal combustion engines.

• Tribology and Lubricants
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• v.30 no.1
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• pp.21-28
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• 2014

Damage to the cylinder liner of large ship engines, such as scuffing on the surface, can occur very easily because it is operated in a corrosive environment. This scuffing may be due to oil film destruction and corrosive wear caused by water and sulfur included in the fuel, abrasive impurities, and poor lubricants. Thus, a method for monitoring the condition and diagnosing the failure of the cylinder liner and piston ring is needed. In this study, a reciprocating friction and wear test was carried out with a cast iron specimen, which simulated an engine cylinder in a corrosive atmosphere. The lubricants used were base oil, stirred oil with distilled water, a NaCl solution, and dilute sulfuric acid. The friction coefficient and frequency spectrum were measured using a load cell and acceleration sense in each experimental condition. We then used these results to diagnose the failure of the cylinder liner.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.1028-1035
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• 2007

this study, forced vibration analysis was performed on the composite main wing structure of a small scale WIG craft which is equipped two-stroke pusher type reciprocating engine. The structural vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the H-mode(horizontal mode), the V-mode(vertical mode) and the X-mode(twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the L-mode(longitudinal mode) with the oscillating propeller thrust which occurs.