• 오토저널
• /
• 제8권1호
• /
• pp.62-74
• /
• 1986

The simulation of power cycle and unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 2-stroke cycle compression ignition engine was studied in this paper. In power cycle process, the single-zone model proposed by Whitehouse and Way was used, and the convective and radiative heat transfer from cylinder contents to surroundings was considered. To solve the equations for gas exchange process, the generalized method of characteristics including area change, friction, heat transfer and entropy gradients was used. Also with the path line calculation, the entropy change along the path line and the variation of specific heat due to the change of temperature and the composition of cylinder gas were considered. As a result of the simulation, the change of pressure and temperature in the cylinder against the crank angle, the rate of net heat release, and the change of properties at each point in the inlet and exhaust pipe against the crank angle were obtained. The engine performances under various operating conditions were also calculated.

• 한국소음진동공학회논문집
• /
• 제24권6호
• /
• pp.452-461
• /
• 2014

Two stroke low speed diesel engines that have many advantages such as high thermal efficiency and durability have been widely used for marine engine. However, it is also true that many problems have occurred due to the high explosion pressure and severe operating environment. Especially problems of shaft damage etc. intensively occurred due to the phenomenon of crankshaft exceeding the allowable stress, including the shaft vibration of the engine model in the early stage. In this study, the crankshaft fracture phenomenon of early engine model was evaluated and analyzed by using up-to-date torsional vibration calculation program and measurement instrument. And this was numerically shown.

• Journal of Advanced Marine Engineering and Technology
• /
• 제7권2호
• /
• pp.22-28
• /
• 1983

In former papers which were published already, authors had derived calculation formulae for the axial stiffness and the radial force conversion factor of crankshaft. In this paper, crankthrow axial stiffness and radial force conversion factors of actual engines are calculated by these theoretical formulae and then their characteristics are investigated. As the results, the axial stiffness and the radial force conversion factor of the latest super-long stroke engine are smaller than those of old-type engines. The influence of the former brings down the resonance speed of engine and the latter reduces the exciting force of axial vibration, but as the harmonic component of axial vibration force becomes rather strong, its effect of reducing is considerably canceled. In conclusion, as the latest super-long stroke engine is seemed to be liable to axial vibration of crankshafat, it is recommend that, in the design stage of propulsion shaft, its axial vibration condition must be more carefully checked.

• Journal of Mechanical Science and Technology
• /
• 제15권1호
• /
• pp.108-116
• /
• 2001

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry. Thus, the quantitative analysis of the in-cylinder flow characteristics plays an important role in the improvement of engine performances and the reduction of exhaust emission. In order to obtain the quantitative analysis of the in-cylinder gas flows for a gasoline engine, the single-frame particle tracking velocimetry was developed, which is designed to measure 2-dimensional gas flow field. In this paper, influences of the swirl and tumble intensifying valves on the in-cylinder flow characteristics under the various intake flow conditions were investigated by using this PTV method. Based on the results of experiment, the generation process of swirl and tumble flow in a cylinder during intake stroke was clarified. Its effect on the tumble ratio at the end of compression stroke was also investigated.

• 대한기계학회논문집B
• /
• 제34권12호
• /
• pp.1043-1050
• /
• 2010

HCCI엔진에는 농도성층화와 열적성층화가 존재하고, 이것들은 착화와 연소과정에 영향을 미치고 있다. 본 연구에서는 예혼합기의 불균질성이 HCCI연소과정에 미치는 영향에 대해서 조사하였다. 우선 4행정광학엔진을 이용하여 잔류가스가 있는 경우와 급속압축장치를 이용하여 잔류가스가 없는 경우의 예혼합기의 불균질성에 대하여 비교분석하였다. DME를 연료로 이용하고 프래밍카메라를 사용하여 2차원화학발광이미지를 취득하였다. 그 결과, 잔류가스가 있는 불균질 한 경우에 4행정엔진실험에서는 연소현상이 공간적으로 연소현상의 시간차이가 발생하였다. 잔류가스가 없는 급속압축장치의 실험에서는 4행정기관의 결과에 비해서 더 적은 공간적인 변화가 존재하는 것을 알 수 있었다.

• 한국자동차공학회논문집
• /
• 제17권1호
• /
• pp.105-113
• /
• 2009

The performance of a direct-injection type diesel engine often depends on the strength of swirl or squish, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the combustion in the cylinder was affected by the mixture formation process. In this paper, combustion process of biodiesel fuel was studied by employing the piston which has several grooves with inclined plane on the piston crown to generate swirl during the compression stroke in the cylinder in order to improve the atomization of high viscosity fuel such as biodiesel fuel and toroidal type piston generally used in high speed diesel engine. To take a photograph of flame, single cylinder, four stroke diesel engine was remodeled into two stroke visible engine and high speed video camera was used. The results obtained are summarized as follows; (1) In the case of toroidal piston, when biodiesel fuel was supplied to plunger type injection system which has very low injection pressure as compared with common-rail injection system, the flame propagation speed was slowed and the maximum combustion pressure became lower. These phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of swirl groove piston, early stage of combustion such as rapid ignition timing and flame propagation was activated by intensifying the air flow in the cylinder. (3) Combustion process of biodiesel fuel was improved by the reason mentioned in paragraph (2) above. Consequently, the swirl grooves would also function to improve the combustion of high viscosity fuel.

• 한국자동차공학회논문집
• /
• 제20권6호
• /
• pp.52-60
• /
• 2012

Minimizing the cylinder wear and the consumption rate of cylinder oil in a large two-stroke diesel engine is of great economic importance. A motor-driven cylinder lubricator for Sulzer RT-flex large two-stroke diesel engines developed by authors is in need of modifying the lubricating system to lubricate cylinder parts optimally by an electronically controlled quill device according to changes of engine load and revolution speed. In order to apply the developed accumulating distributor to an integrated cylinder lubricator by the electronically controlled system as the third research stage, the lubricating system is improved in the electronically controlled quill device with a solenoid valve. In this study, the effects of lubricator revolution speed, driving pressure and cylinder back pressure on oil feed rate, maximum discharge and delivery pressures are experimentally investigated by using the integrated cylinder lubricator system with an accumulated distribution by the electronic control. It is found that the oil feed rate of the developed integral cylinder lubricator system is less than that of the motor-driven cylinder lubricator by the electronically controlled quill system equipped with an accumulating distributor because of the decrease of delivery speed by increasing the maximum delivery pressure in the same experimental condition.

• 한국군사과학기술학회지
• /
• 제25권5호
• /
• pp.539-544
• /
• 2022

This research shows the test performance of a 6 kW-scale hybrid electric power system for the high endurance drone. The power system is composed of a two-stroke reciprocal engine, starter-generator and battery, and they are integrated as one power unit. The engine is designed to provide the house for holding the starter-generator at the end of a crankshaft in turn the engine and starter-generator can maintain the same speed during the operational period. In this way, the generated power is readily controlled by just manipulating an engine throttle movement. Moreover, the starter-generator can initiate an engine operation with an aid of battery power until the combustion process becomes stabilized. In consequence, integration mechanism between an engine and generator is simplified, which results in weight reduction achieved. The duty of back-up battery is to provide a starting power to generator via a system controller in addition to covering momentarily power shortage. Therefore, the electric power system is vindicated to provide 6 kW power through a ground test.

• 기술사
• /
• 제34권2호
• /
• pp.31-36
• /
• 2001

The Otto Cycle of conventional gasoline engine has no difference between compression ratio and expension ratio. because of the same length of 4 strokes : Intake, compression, expension, exhaust. On the other hand, miller cycle engine achieves both low-compression ratio and high-compression ratio by shortening the length of compression stroke among 4 strokes. Therefore miller cycle engine is essential for lessening knocking and improving heat efficiency. This paper Is designed to discribe not only principle and the development trend of miller cycle engine but also the control system and the technical characteristics of it.

• 한국자동차공학회논문집
• /
• 제17권2호
• /
• pp.42-48
• /
• 2009

This paper is the second of 2 companion papers which investigate in-cylinder swirl generation characteristics according to inlet valve angle. Two DOHC 4 valve engines, one has wide intake valve angle and the other has narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port was deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. The results show that the flow patterns of narrow valve engine are much more stable and well arranged compared with the normal engine over the entire intake and compression stroke except early intake stage, and very strong swirl motion is generated at the end of compression stage in this engine nevertheless using straight port which is unfavorable for swirl generating. In the wide valve angle one, however, strong swirl motion induced during intake stroke is destroyed as the compression progresses.