An Experimental study of heat transfer on a heated flat plate by a circular impinging jet

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열연 ROT 냉각 전열특성 해석(I)-단일노즐에 의한 수분류냉각

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Combustion Improvement by Tumble Flow in Engines

Tumble flow is very effective for turbulence enhancement near the spark timing, and eventually improves the combustion performances in spark-ignition engines. In this paper the effects of tumble flow on combustion characteristics in a four-valve engine was investigated by using LDV measurements and combustion pressure inside engine cylinder. Tumble flow patterns was changed by intake port flow angles which is implemented by an aluminum cassette. The results show that high tumble flow can be generated during intake by a moderate inlet angle and decreases burning duration in lean mixture operation condition

The Development of an Optical Single Cylinder Engine for Combustion Visualization Studies

A single-cylinder optical research engine for combustion visualization has been developed by modifying a 4-cylinder DOHC, spark-ignition engine. The design tips for the optical engine development are described and the visualized flame images are given. The optical engine has a piston-top window in the extended piston which allows optical access into the combustion chamber for flow and combustion research. The flame propagation at 800rpm was imaged by an ICCD camera for stoicheometric mixture under idling condition.이 연구는 통산산업부에서 수행한 G7 차세대자동차 저공해 공통기반기술과제의 연구비 지원에 의해 수행된 결과의 일부입니다

Effects of Stratified EGR under lean operation of a Liquid Phase LPG Injection Engine

Stratified EGR (Exhaust Gas Recirculation) achieves not only reductions in NOx emission and fuel consumption but also combustion stability improvement for highly diluted mixture. In this study, the timing and duration of a fast-response solenoid valve installed in the midst of EGR line was controlled to form the axial stratification of EGR within the cylinder. Lean burn of LPG with both stratified and homogeneous EGR was examined in terms of the rate of heat release, combustion stability (or EGR tolerance), fuel consumption and engine-out emissions. Since stratified EGR showed faster combustion and improvement in combustion stability, more EGR amount was admitted and more reduction of NOx emission with less increase in HC emission was attained with stratified EGR than homogeneous EGR.본 연구는 과학재단 우수연구센터사업(ERC)의 지원 아래 연소기술센터 (CERC)의 과제로 수행되었으며 이에 관계자 여러분께 감사드립니

Effects of Stratified EGR on the Performance of a LPLI Engine

EGR (exhaust gas recirculation) utilizes the diluents into the engine cylinder to control combustion leading to enhanced fuel economy and reduced emissions. However, with high diluent rate, the occurrence of excessive cyclic variation brings about an undesirable combustion instability resulting in the deterioration of engine performance. Proper stratification of diluent could improve the combustion stability under high diluent environment. EGR stratification within the cylinder was made by adopting a fast-response solenoid valve in the midst of EGR line and controlling its timing and duty. With supplying EGR in both homogeneous mode and stratified mode, thermodynamic heat release and flame propagation characteristics were investigated in an optically accessible single cylinder engine. Shorter burning duration and faster flame propagation were found in the case of stratified EGR than homogeneous EGR PLIF images gave the EGR distribution within cylinder to show that EGR occupied the lower part of cylinder through the stratification process and this could help reducing the burning duration.본 연구는 LP 가스보급협의회와 과학기술부 우수연구센터사업(ERC)의 지원으로 수행되었으며 이에 관계자 여러분께 감사드립니다

Effects of swirl and squish flow upon fuel stratification

Lean burn considered to overcome high thermal load and improve fuel economy in heavy duty si engine however, lean burn generally causes unstable engine operation due to combustion instability such as cyclic variation,misfire, or partial buning, to overcome such undesirable phenomena charge statification inside the engine cylinder through fuel injection strategy was utlized and flow field enhancement through intake port and pistion shape was adopted. in this study, the effects of swirl ratio and piston bowl shape on the mixture preparation were investigated. high intensity of squish flow as well as swirl flow was acquired by the enlarged pistion squish area and helical intake port. to obtain two dimensional fuel distribution planar laser induced fluorescence(PLIF) was used. acetone was excited by KrF exciner laser(248nm) and its fluoresoence image was acquied by ICCD camera. fuel injection stategy with respect to the intake process was found to have the key role of the whole stratification process. the intense squish flow was found to be effective to place relatively rich mixture to the vicinity spark plug in the end period of compression processqhs dusrnsms LP가스보급협의회와 과학기술부 우수연구센터사업(ERP)의 지원으로 수행되었으며 이에 과계자 여러분께 감사드립니다

Fuel Stratification in Liquid-Phase LPG Injection Engine

This study investigated combustion characteristics paying particular attention to a mass flow rate pattern under stratification charge mode. The mass flow rate was changed using two injector drivers with different operating characteristics for an injector. These injection systems were employed in an optical single-cylinder engine. Three different injection timings under late injection modes were set to simulate the stratification charge combustion. To obtain the mass flow rate, the experiments of fuel metering and injection rate measurement were performed with a fixed injection quantity. In-cylinder pressure was measured to analyze combustion characteristics. Initial flame size and its developments were also visualized. In addition, the mixture distribution prior to ignition was obtained using PLIF technique. As the mass flow rate has a higher value, more stable and faster combustion was achieved. The mixture distribution showed more uniform and higher concentration in the bowl mear the spark plug as the mass flow rate increases