• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.15-22
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• 1987

이상 최근 10년 사이 현저하게 보여준 엔진관계의 신기술과 그 배경 등을 돌아 보았을 때 발전하 는 가운데 특히 4륜차용 2사이클 엔진의 몰락이나 엔진의 주요 부품인 기화기의 쇠태는 그 어느 것이나 시대의 요구에 대한 기술의 한께 혹은 신기술의 개발 템포에 추종키 여려웠던 때문인 것 으로 생각된다. 2사이클 엔진은 비출력이 높고 밸브기구가 없어서 구조가 간단한 등의 장점이 있는 반면 배출가스대책(특히 HC), 경부하시의 부정연소 등의 문제를 가지고 있어 4륜차용으로 서는 배출가스규제를 계기로 SAAB(스웨덴), DKW(서독)의 2사이클 엔진이 자취를 감추게 되었 고 현재 남아있는 것은 일본의 경트럭용 엔진에 지나지 않는다. 또 기화기에 대해서도 배출가 스규제에 대한 대응에 밀려 공연비의 제어성, 고도에 대한 보정성, 내열신뢰성, 제어성, 고도에 대한 보정성, 내열신뢰성, 운전성 등의 요구에 엄해진 반면 흡기포트내(PI), 혹은 흡기관 중양부 내(SPI) 가솔린분사방식에 눌려서 가변벤투리식 등도 미국(1982), 일본(1983)에서 발표되었으나 1985년형의 미국차 엔진에는 기화기의 정착율이 50%에 지나지 않는등승용차용 분야에서는 그 사용이 점차 줄어두는 추세에 있다.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.188-196
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• 1997

Many researchers have developed the measurement technique of in-cylinder flow characteristics and found the effect of intake port geometries on engine performance. The flow characteristics of four-valve cylinder head were examined in a steady flow rig for different intake ports. Tumble intensity of intake configurations with different entry angles were quantified with a tumble meter. The velocity and angular momentum distributions in the tumble adaptor were measured under steady conditions with PIV(Particle Image Velocimetry). We have obtained the results that flow structure becomes complicated by valve interference at low valve lift. As the valve interferences were reducing and the flow pattern changed to large vortex structure with tumble direction, intake ports with different entry angles have different tumble centers. Tumble eccentricity of intake port with low entry angle was large, so that the port had relatively much angular momentum compared to others which was expected to improve combustion performance.

• Journal of ILASS-Korea
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• v.23 no.1
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• pp.36-41
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• 2018

Fuel wall film effects power output and cycle deviation by changing the amount of fuel flowing into cylinder in PFI gasoline engines. Reduction of wall film can reduce fuel consumption and improve combustion stability. In this research, the effects of injection strategies including injection pressure and dual injection system is investigated for reducing wall film formation. The CONVERGE software is used for numerical analysis tool and O'Rourke film splash model was used for wall film prediction model. Compared with the reference case wall film decreased with increase of injection pressures, and the film formation reduced when the dual injection system was used.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

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

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3306-3310
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• 2007

Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. Specially because the combustion flame speed is mainly determined by the turbulence at the end of compression process. Tumble and Turbulence ahead of combustion is very important phenomenon. As this phenomenon make research certainly, combustion condition will effectively be improve. This paper describes analytical results of the tumble flow, intensity, turbulence inside the cylinder of maritime engine. 3-D computation has been performed by using STAR-CD v3.26 solver and es-ice

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.20-27
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• 2003

In this paper, the fuel transport characteristics during transient condition was studied by using a Fast Response Flame Ionization Detector(FRFID). The quantitative measurement method for the inducted fuel mass into cylinder is studied. The inducted fuel mass into the cylinder was estimated by using calculated air-fuel ratio by hydrocarbon concentration of cylinder and air flow model. In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient $\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-off To reduce an air/fuel ratio fluctuation during rapid throttle opening, the appropriate fuel injection rate was obtain from the wall wetting model with empirical coefficients. Result of air/fuel ratio control, air/fuel excursion was reduced.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.921-924
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• 2010

기존의 소형엔진은 캬브레이터 연료 공급 장치를 사용하는 방식으로 연비 및 배기가스 성분이 매우 열악한 실정이다. 본 연구에서는 이러한 단점을 극복하기위하여 전자분사장치를 장착하기위한 설계 및 작동기법에 대한 연구를 수행하였다. 소형엔진은 저가의 범용 동력장치로서 전자화를 위하여 최소한의 제어장치 만으로 구성되어야 한다 일반적으로 전자화를 위해서는 크랭크 축과 캠축의 위상각 신호를 통하여 연료분사와 점화를 제어하는 것이 일반적인 통례이나 본 연구에서는 크랭크 축의 CPS센서와 흡기포트의 압력변동을 이용하여 연료분사와 점화를 제어하는 기구와 장치를 설계 개발하였다. 본 장치는 저가의 범용 엔진에 적용이 가능하며 제어반복성에도 우수한 특성을 보였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.13-21
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• 2007

This paper presents characteristics of steady flow by variation of a combustion chamber and an intake port. Gas flow field inside a combustion chamber is the important factor in improving combustion stability and reduction of emission level. The flow characteristics such as flow coefficient, tumble ratio and swirl ratio are measured by the steady flow rig test with an impulse meter in this study. In the measuring, the valve lifts are varied between 1mm to 10mm. The three combustion chambers and two intake ports were applied to the steady flow apparatus in order to investigate the effect of swirl and tumble on the in-cylinder flow. As a result, tumble ratio were found to be different by variation of the combustion chambers and the intake ports. The data from the present study can be applied to design of a similar engine as basic data.