• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.28-44
• /
• 2020

In this paper, the scavenging process of various transfer ports was evaluated to improve the performance of a small two-stroke engine for unmanned aerial vehicles. Three-dimensional computational fluid dynamics simulations were performed to four transfer ports for the evaluation, and a three-phase scavenging model was developed and applied to the simulation results for the quantitative comparison of scavenging performance. the short-circuit of fresh charge was restrained and an in-cylinder turbulent kinetic energy was enhanced by changing the transfer port. Also, a difference in the scavenging for each port were confirmed by applying the three-phase model to the simulation results.

• Journal of ILASS-Korea
• /
• v.14 no.1
• /
• pp.34-38
• /
• 2009

This paper presents the pulsation of carburetor inlet and outlet pressure of a small SI gasoline engine. The engine used in this paper is a 23cc, single cylinder, diaphragm carburetor, two-stroke, air-cooled for brush cutter. The rpm and pressure wave pulsation at the inlet and the outlet of carburetor were measured and analysed for the understand of the internal air flow into the barrel on the diaphragm carburetor. These data should be used for the development of the duel fuel injection system for gasoline and LPG. The results showed that the carburetor inlet pressure variations were very steady, but the pressure variations at carburetor outlet were very sensitive to the pressure variation into the crank case and were to similar independently to the engine speed on partial opened throttle conditions. According to increasing engine speed, the pressure waves started to come out and be developed after closing the intake port of the engine at carburetor outlet. Reverse flow occurred on the WOT (wide open throttle) condition.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.8
• /
• pp.827-836
• /
• 2006

• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.9
• /
• pp.10-19
• /
• 1999

In this study , a simple method has been developed to detect the required spark voltage by using the primary spark voltage instead of the secondary spark voltage. Through engine motoring experiments, this method testified to be quite satisfactory. Though the required spark voltage is affected by many in-cylinder conditions, temperature is one of the most important factors. The temperature increases significantly by combustion and the required spark voltage also changes by the temperature during the expansion stroke. On the basis of this fact, misfire can be monitored by comparing the required spark voltage between compression stroke and expansion stroke. So, in this study, two step ignition method is introduced to monitor combustion at expansion stroke. The test result shows that this method can be used to detect complex misfire pattern.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.4
• /
• pp.91-98
• /
• 2011

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 mounting a quill system to lubricate cylinder parts for smoother operation. In order to apply the common-rail lubricating system to the developed cylinder lubricator as the second research stage, the quill system with a progressively quantitative distributor is improved in the electronically controlled quill system with an accumulating distributor. In this study, the effects of lubricator motor speed, plunger stroke and cylinder back pressure on oil feed rate, maximum discharge and delivery pressures are experimentally investigated by using the electronically controlled quill system with an accumulating distributor in the developed cylinder lubricator. It is found that the oil feed rate of the electronically controlled quill system with an accumulating distributor is larger than that of the quill system with a progressively quantitative distributor because of the increase of delivery speed and volume by changing the location of accumulator in the same experimental condition.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.3
• /
• pp.26-36
• /
• 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 mounting a quill system to lubricate cylinder parts for a smooth operation. In order to apply the common-rail lubricating system to the developed cylinder lubricator as the second research stage, the mechanical quill system with a progressively quantitative distributor (M.D.S.) is improved in the electronically controlled quill system with an accumulating distributor (E.D.S.). In this study, the effects of lubricator motor speed, plunger stroke and cylinder back pressure on oil feed rate and inequality rate are experimentally investigated by applying E.D.S. to the developed cylinder lubricator. It is found that the oil feed rate of E.D.S. is higher than that of M.D.S. because of the increase of delivery speed and volume by changing the role of accumulator in the same experimental condition. It can be also shown that, in E.D.S., the inequality rate is decreased a little or hardly unchanged as the cylinder back pressure and plunger stroke is elevated, while the inequality rate increased in M.D.S.. The inequality rates of E.D.S. and M.D.S. are lowered as the lubricator motor speed is increased.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.1
• /
• pp.165-176
• /
• 1996

The flow field and spray characteristics for loop scavenged type 2stroke engine having pancake shape was numerically computed using KIVA-Ⅱ code. The cylinder has 1intake port, 2side intake ports and 1exhaust port with induced flow angle 25 deg. In engine calculation, the chop techniques is used to strip or add planes of cells across the mesh adjacent to the TDC and the BDC(ports parts) for preventing the demand of exceed time during the computation, providing a control on cell height in the squish region. The modified turbulent model including the consideration of the compressibility effect due to the compression and expansion of piston was also used. The case of 25 deg.(injection angle) which is opposite to scavenging flow direction shows better the distribution of droplets and the evaporation rate of droplets compared to other cases(0 deg., - 25 deg.). When injection pressure was increased, the spray tip penetration became longer. When injection pressure was increased, the interaction between the upward gas velocity and spray droplets strongly cause. Thus the breakup of droplets is strongly occurred and the evaporation rate of droplets was found to be better.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.17 no.4
• /
• pp.3970-3979
• /
• 1975

On account of the development of the high speed internal combustion engines, several methods for increasing burning velocity has been investigated lately. Installation of a squash area on a cylinder head is one of the simple and practical method to induce the strong tubulant flow of air-fuel mixtureinto a combustion chamber. In this study, a four-stroke engine used for agricultural purpose was tested as an experimental model. A mathematical model of the squash velocity was derived, and also, several characteristics of the squash phenomena during the motoring of the engine used as a modelwere investigated. The results obtained were as follows: (1) Mathematical model of squash velocity was established and cheked (2) Squaash velocity and engine speed were found to be proportional to the squash area while they were inversely proportional to the squash width. (3) Squash velocity and crank angle at which the squash velocity become its peak were influenced by the magnitude of squash clearance: increase of squash clearance made squash velocity reduced acd made the peak of the squash velocity for from the top dead center and (4) When the squash area is divided in small areas baving unit width along the squash section, squash velocity at each unit width was proportional to the magnitude of the squash distance covered by the unit width.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.2
• /
• pp.132-137
• /
• 2007

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.2
• /
• pp.69-79
• /
• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.