• 한국자동차공학회논문집
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• 제13권5호
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• pp.64-74
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from two-holes two-sprays type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.38-43
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• 2011

A CNG/diesel dual-fuel engine uses CNG as the main fuel and injects a small amount of diesel as an ignition priming. This study proposed the modification of the existing diesel engine into a dual-fuel engine that injects diesel with a high pressure by common rail direct injection (CRDI) and by injecting CNG at the intake port for premixing. And experiment was progressed for understanding about effect of CNG mixing ratio. The CNG/diesel dual-fuel engine showed equally satisfactory coordinate torque and power regardless of CNG mixing ratio. The PM emission was low at any CNG mixing ratio because of very small diesel pilot injection. In case of NOx and HC, high CNG mixing ratio showed low NOx and HC emissions at low speed. At medium & high speed, low CNG mixing ratio showed low NOx and HC emissions. Therefore, it would be optimized by controlling CNG mixing ratio.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.57-64
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• 1999

Initial flame development and propagation were visualized under the new ignition system developed to estimate the effects of ignition characteristics on the engine performance in a port injection SI engine. Effects of intake air flow characteristics were also investigated by three different kinds of the swirl control valve. Experiments were performed in an optical single cylinder engine modified form a commercial engine. Flame images were captured through the quartz window mounted in the piston by the high speed video camera and analyzed to compare initial flame development. Results show that IMEP tends to rise slightly as the ignition duration gets longer. The direction of flame propagation is decisively governed by the in-cylinder flow motion. Every flame grows toward the exhaust valve forming a kind of turbulent flame. Initial flame propaagation characteristics are very similar to ones analyzed form pressure data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2082-2087
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• 2004

In this study, the variation of spark plug location in the combustion chamber was investigated for the sake of emission characteristics from SI engine by using PDA valve. The swirl is ong of the important parameters that effects emission characteristics. PDA valve has been used to satisfy the requirements of sufficient swirl generation to improve combustion and emission reduction to effect on flow profile on a combustion chamber. Especially, the variation of spark plug location have an important effect to analyze exhaust gas and the early flame propagative process. Therefore, this test is forced that injection timing, spark timing and intake air motion govern the stable combustion. From the results, it showed that the variable spark plug location and PDA valve can be reduced exhaust gas.

• 한국가스학회지
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• 제23권6호
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• pp.90-96
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• 2019

셰일가스의 채굴량 확장과 러시아를 통한 PNG (Pipeline Natural Gas)의 도입은 천연가스가 유력한 대체 연료임을 시사해주고 있다. 따라서 향후 증대될 천연가스의 공급에 맞추어 해당 연료의 수요처 증대가 필수적인 상황이다. 이와 같은 상황에서 수송분야는 저탄소 기체 연료인 천연가스를 적용하기 적합한 분야이며, 이를 통해 이산화탄소와 입자상 물질 등의 유해 배기물질을 저감하는 데 큰 역할을 할 것으로 기대된다. 천연가스는 자발화 특성이 낮고, 내노킹(Anti-knocking)성이 우수하기 때문에 전기점화 방식에 적합하다. 최근 가솔린 엔진은 연비 개선을 위해 연소실에 직접 분사하는 방식을 주로 채택하고 있으나,연소실 내로 액상 직분사를 하는 반면 천연가스의 경우 액상분사 혹은 고압 분사가 어렵다. 따라서 포트에 분사하는 방식을 사용하므로 동등 흡기압력에서 연료의 분율이 흡입공기의 체적을 대체하여 가솔린 직분 방식에 비해 출력이 저하되는 현상을 피할 수 없게 된다. 이에 본 연구에서는 터보차저를 천연가스 포트 분사 엔진에 적용하여 흡기 압력 상향을 통한 출력 보상을 도모하고자 하였다.그 결과 천연가스 적용 시 흡기압력을 기존 가솔린 대비 5-27 % 상향 시 가솔린 직분사 엔진과 동등 출력을 확보함과 동시에 향상된 제동 열효율을 확인 할 수 있었다.

• 한국가스학회지
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• 제25권5호
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• pp.11-18
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• 2021

수소는 동일한 공연비(AF ratio, Air-to-fuel ratio)에서 가솔린에 비해 점화에너지가 현격히 낮기 때문에, 희박한 혼합기 조건에서도 안정적으로 연소할 수 있는 장점을 가지고 있어 연소를 기반으로하는 내연기관에도 적용이 가능하다. 그러나 일부 연소조건에서 역화(Back-fire) 혹은 조기 점화(Pre-ignition)와 같은 이상 연소가 발생하기 쉬운 문제를 가지고 있다. 따라서 본 연구에서는 엔진의 흡기(Intake gas mixture)를 구성하는 신기(Fresh air)와 수소 연료를 각각 냉각하여 공급함으로써, 역화를 최소화하여 최고 출력을 향상하는 연구를 진행하였다. 2.4 L급 전기점화(SI, Spark-ignition)엔진이 사용되었으며 수소는 포트분사 방식(PFI, Port Fuel Injection)으로 공급하였다. 신기의 온도는 터보차저가 장착된 상황에서 인터쿨러(Intercooler)를 이용하여 제어하였으며, 수소의 냉각은 칠러의 냉매와 열교환기를 통하여 직접 냉각 후 공급하였다. 그 결과 신기의 온도를 10~20 ℃가량 냉각시킬 경우 최고출력이 약 6.5~8.6 % 가량 향상되는 것을 확인할 수 있었으며, 수소를 -6 ℃까지 냉각하여 공급할 경우 마찬가지로 약 7.7 % 가량의 최고 출력을 향상할 수 있었다.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.10-16
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• 2005

Recently, the international regulations about the exhaust emissions of the motorcycle have been strengthened. The electrically controlled fuel injection type motorcycle has been emphasized to meet with this regulation. However, since the pulsation phenomenon happens in the intake port of the motorcycle because of the characteristic of high speed and the smaller layout than the passenger car, there are many difficulties to select the factor about control parameters needed to develop the ECU system. In this paper, the pulsation values measured from the engine test were compared with the calculated one by WAVE, and it was analyzed the pulsation characteristic according to the driving condition and estimated the mass flow rate. This research showed that the lowest point of the pressure gets lowin the low load and the pulsation of pressure were increased in the high load. Also, the simulation program was verified by showing good prediction of the pulsation and air mass flow rate.

• 한국분무공학회지
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• 제14권1호
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• pp.34-38
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• 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.

• 한국생산제조학회지
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• 제19권6호
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• pp.812-828
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• 2010

A fuel injection system using an ECU HILS as an alternate to a vehicle test for the fuel injectors was developed. The throttle position, vehicle speed, engine speed, crank position, cam position, intake air flow, and several other sensor signals that are supplied to the ECU were measured and recorded as a data file for a vehicle driven in the FTP-75 mode in a chassis dynamometer. Electric signals that are equivalent to the sensor signals from the vehicle are reconstructed from the recorded data file using data acquisition boards, microprocessors, and computers. All sensor signals are supplied to the ECU with synchronized timing using a computer program. The findings show that the cost and time of vehicle experiments can be reduced using the ECU HILS system. Moreover, the repeatability of the generation of sensor signals can enhance the accuracy of a range of experiment related to vehicle testing. An ECU scanner that scans the sensor signals that are input to the ECU through a serial port was used to assess the accuracy of the reconstructed signals. The scanning results show good agreement with the reconstructed input signals. Injectors were connected to the ECU HILS system and were driven by the system to measure the quantity of injected fuel.

• 한국공작기계학회논문집
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• 제14권4호
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• pp.32-40
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• 2005

The purpose of this study is to investigate variation of spark plug protrusion and PDA valve on the exhaust emission in a gasoline engine. Swirl is one of the important parameters that affects the characteristics of combustion. PDA valve has been developed to satisfy requirements of sufficient swirl generation for improving the combustion and reducing of emission level. Also, especially, the variation of spark plug protrusion have an important effect to the early flame propagative process. This is largely due to the high flame speed by short of flame propagation distance. So, this is forced that injection timing, spark timing and intake air motion govern the stable combustion. As a result, using two combustion chamber, without charge of engine specification and the variable spark plug location and PDA valve could be reduced exhaust gas at a part load engine conditions(1500rpm imep 3.9bar, 2000rpm imep 3.2bar, 2400rpm imep 3.9bar).