• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.56-61
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• 2010

This paper presents dynamic clearance verification considering engine movement for vehicle engine room package and validates through physical vehicle test. Traditionally, static clearance guide has been used for engine room package, but it's only 2-dimension criteria that results in requiring unnecessary space and it's not possible to conduct engine movement with real driving conditions. Thus, the dynamic DMU considers engine movement based on 28 load cases that are Roll Data analyzed by CAE for maximum engine movement and visualizes part-to-part dynamic clearance into virtual space. The dynamic DMU enables to develop compact engine room package without unnecessary space. The result of comparison between simulation and physical test has 0.892 correlation coefficient.

• Tribology and Lubricants
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• v.26 no.4
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• pp.240-245
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• 2010

This paper describes the influence on engine main bearing behavior of the oil film when the fuel is diluted on a diesel engine equipped with DPF system. Oil film pressure and the thickness is calculated in accordance to the fuel dilution. The calculation is based on the numerical analysis of the engine main bearing. As a result, the engine oil viscosity decreased as the fuel dilution increased. This led the increment of the maximum oil thickness pressure. Verification of the minimum oil film thickness settlement by the engine gas pressure and the fuel dilution was confirmed. Destruction possibility of the engine main bearing was foreseen when the engine speed was 2000 rpm with the fuel dilution 15% and the 5W40 engine oil.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.257-260
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• 2003

Dynamic simulation program for a smart UAV turbojet engine was developed. The transient simulation program utilized the CMP(Constant Mass flow) method and Euler integration method for integration of excess torque. The transient performance analysis was carried out by increasing from the idle to the maximum rotational speed of the gas generator. To observe engine dynamic behavior, fuel flow was monitored through a step and a ramp increase. When the fuel was increased as a step function the overshoot of the turbine inlet temperature exceeded the limit temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.409-412
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• 2009

A 75ton thrust turbopump system for liquid rocket engine was analyzed thermally and mechanically. A 2D axisymmetric model of the turbopump assembly was created. In the analysis operation cycle including chill-down, operation and post operation steps were considered. Appropriate heat transfer conditions for each step were modeled and applied. Transient temperature distribution was calculated, consequent mechanical analysis was conducted to predict stress and deformation. Effects of external heat insulators and heat dissipation at the bearings were considered in the heat transfer analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.64-75
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• 2009

The shipbuilder's requirement for a higher power output rating has led to the development of a super large two stroke low speed diesel engines. Usually a large-sized bore engine ranging from $8{\sim}14$ cylinders, this engine group is capable of delivering power output of more than 100,000 bhp at maximum continuous rating(mcr). Other positive aspects of this engine type include higher thermal efficiency, reliability, durability and mobility. This plays a vital role in meeting the propulsion requirement of vessels, specifically for large container ships, of which speed is a primary concern to become more competitive. Consequently, this also resulted in the modification of engine parameters and new component designs to meet the consequential higher mean effective pressure and higher maximum combustion pressure. Even though the fundamental excitation mechanisms unchanged, torsional vibration stresses in the propulsion shafting are subsequently perceived to be higher. As such, one important viewpoint in the initial engine design is the resulting vibration characteristic expected to prevail on the propulsion shafting system(PSS). This paper investigated the torsional vibration characteristics of these super large engines. For the two node torsional vibration with a nodal point on the crankshaft, a tuning damper is necessary to reduce the torsional stresses on the crankshaft. Hence, the tuning torsional vibration damper design and compatibility to the shafting system was similarly reviewed and analyzed.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.99-106
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• 1998

The performance of the turbofan engine, a medium scale civil aircraft which has been developing in Rep. of Korea, was analyzed and the control scheme for optimization the performance was studied. The dynamic and real-time linear simulation was performed in the previous study The result was that the fuel scedule of the step increase overshoot the limit temperature(3105 $^{\cire}R$) of the high pressure turbine and got small surge margine of the high pressure compressor. Therefore a control scheme such as the LQR(Linear Quadratic Regulator) was applied to optimizing the performance in this studies. The linear model was expected for designing controller and the real time linear model was developed to be closed to nonlinear simulation results. The system matrices were derived from sampling operating points in the scheduled range and then the least square method was applied to the interpolation between these sampling points, where each element of matrices was a function of the rotor speed. The control variables were the fuel flow and the low pressure compressor bleed air. The controlled linear model eliminated the inlet temperature overshoot of the high pressure turbine and obtained maximum surge margins within 0.55. The SFC was stabilized in the range of 0.355 to 0.43.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.127-138
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• 2018

In this study, the operational characteristics of a domestic vegetable transplanter were investigated. The main functional components and power path of the tranplanter were analyzed. The link structure of transplanting device waskinematically analyzed, and 3D modeling and dynamic simulation were performed. Based on this analysis, the trajectory of the bottom end of the transplanting hopper was analyzed. Also, the plant spacing according to the engine speed and the shifting stage of transplanting transmission was analyzed and verified by field test. As main results of this study, the transplanting device is one degree of freedom(DOF) 4-bar link type mechanism which comprises 10 links and 13 rotating joints. The transplanting hopper plants seedlings in a vertical direction while maintaining a constant posture by the links of transplanting device. The power is transmitted to both the driving part and transplanting part from the engine, and the maximum and minimum plant spacing of the transplanting device were 428.97 mm and 261.20 mm.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.275-282
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• 2004

The engine bearing transmits the powers from cylinder to crankshaft with small clearance between con-rod and crankpin. The minimum oil film thickness is a significant parameter in the operation of bearing. The contact pressure of bearing should be considered for the reason that elastic deformation of bearing be caused by contact pressure of bearing. There are important factors which are maintaining of minimum oil film thickness expecting of the length of maximum and minimum oil film thickness with changing of the loads to keep running normally. Furthermore, this study is very crucial to develop the design of engine bearing and crankshaft system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.65-70
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• 1996

엔진소음을 소음특성에 따라 분류하면 공력소음(Aerodynamic Noise), 연소소음(Combustion Noise), 기계적인 소음(Mechanical Noise)으로 나눌 수 있으며 소음원의 종류에 따라 분류하면 배기계소음(Exhaust System Noise)으로 나눌 수 있으며 소음원의 종류에 따라 분류하면 배기계소음(Exhaust System Noise), 흡기계소음(Intake System Noise), 냉각계소음(Cooling System Noise), 엔진표면소음(Engine System Noise)등으로 분류할 수 있다. 이러한 여러소음중 엔진 내부의 유동에 의한 흡배기계통으로의 소음방출은 자동차 실 내외 소음의 중요한 문제로 대두되는데, 이를 줄이기 위해 그 동안 소음기 등의 서브시스템의 형태와 그 위치조정에 관한 연구가 수행되어 왔다. 그러나 이것이 비용 또는 성능에 영향을 미치므로 본질적인 소음원을 규명해 내는 것이 필요하게 되었다. 흡배기계의 소음은 엔진의 흡입, 배기행 정시 피스톤의 운동에 의해 팽창 및 압축파 형태의 압력파(pressure wave)로 발생하게 되고, 밸브근방에서는 유동의 박리(separation)에 의해 발생하게 된다. 소음기 등의 서브시스템에서도 유동의 박리에 의해 발생하게 되며 특히 배기행정시 발생하는 압력파는 비선형영역에 있게된다. 흡기소음은 배기에 비해 그 크기가 작아서 그동안 등한시 되어왔으나 이것이 소비자의 불평요인으로 작용하므로써 이에 대한 연구도 활발히 수행되어야 한다. Bender, Bramer[1]는 흡배기계 소음의 외부 방사에 관하여 전반적으로 기술하였고 Sierens등[2]은 흡기계에서 1차원 MOC(Method of Characteristics)방법으로 비정상 유동해석을 하고 실험결과와 비교하였다. J.S.Lamancusa 등[3]은 흡기 소음원을 실험을 통해 예측하였고, 흡기소음도 비선형 거동을 보인다고 밝혔다. Yositaka Nishio 등[4]은 새로운 흡기실험장치를 고안하여 공명기(resonator)의 위치 변화에 의한 저소음 흡기계를 설계 초기단계에서부터 적용하려 하였다. 일반적으로 흡배기계의 복잡한 형상 때문에 대부분 실험을 통해 문제를 해결하려 하였고, 수치해석은 피스톤의 운동을 배제한 단순화한 흡배기계의 정상상태 유동해석이 주를 이루어왔다. Taghaui and Dupont 등[5]은 KIVA코드를 사용하여 흡기포트와 연소실 그리고 밸브의 움직임을 동시에 고려한 수치해석을 도입하였다. 하지만 이들이 밸브의 운동을 고려하기 위해 사용한 이동격자는 격자점은 시간에 따라 변화하지만 그 격자의 수가 일정하게 유지되어 있어서 밸브의 완전개폐를 해석할 수가 없다. 강희정[6]은 단일 실린더와 단일 배기밸브를 갖는 문제로 단순화하여 피스톤과 밸브의 움직임을 고려하므로써 배기행정 후 소음이 어떻게 전파해 나가는가를 연구하였다. 본 연구에서도 최소밸브간격과 최대밸브간격 사이에서만 계산이 가능하나 흡기의 경우는 밸브가 닫힐 때 생기는 압력파가 중요하므로 실린더와 밸브사이에 벽면조건을 주어 밸브의 개폐를 모사하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1151-1159
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• 2012

Spray visualization and computer simulation of a DME injector have been conducted to investigate the enlarged injection hole diameter effect. To increase the reliability of the computational result, simulation results have been compared with the visualization test results, and the behaviors of a DME spray under various high-pressure and -temperature conditions have been computed. This study shows a discrepancy of 3.57% between the experimental and the computational results of penetration length for an injection pressure of 35 MPa and ambient pressure of 5 MPa. When simulating the engine conditions, the maximum penetration length of a fully developed DME spray is 42 mm when the temperature to pressure ratio is 300 K/MPa. The DME spray behavior is dominantly affected by the ambient pressure under the condition that the ratio is less than 300 K/MPa, and by the ambient temperature under the condition that the ratio is more than 300 K/MPa.