• 대한기계학회논문집A
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• 제21권12호
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• pp.2081-2089
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• 1997

Accurate positioning of the throttle valve of a gasoline engine is required to implement various systems such as traction control system(TCS), cruise control system and drive-by-wire system. In this research, position control system has been developed for the throttle actuator system that uses one throttle actuation for small volume and DC servo motor for fast response. In order to drive the DC motor, PWM signal generator and PWM amplifier were built and interfaced to the motor and controller. Also, time delay control(TDC) law has been used as a basic control algorithm. A method of varying the reference model of the TDC according to the size of change in target throttle angle is proposed here. The simulation and experimental results show that both overshoot prevention and fast response are achieved by the TDC technique with this variable reference model.

• 한국분무공학회지
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• 제9권1호
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• pp.37-42
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• 2004

In a port fuel injection system of engine, a large part of fuel injected into an intake port adheres on its wall and inlet valve. Consequently, the wall impinging spray interaction might occur the generation of several harmful phenomena. There are uncontrollable mixture formation, an accidental backfire and unburned hydrocarbons. Therefore, it is important to analyze the fuel behavior during the spray-wall interaction. In this study, splash characteristics of impingement and reflecting or scattering behavior of droplets of fuel injected from EFI nozzle were studied experimentally. A test fuel used is LAWS and its physical characteristics are similar to the conventional gasoline except for the ignition point. Since the liquid film formed immediately after impinging on an impingement plate is unstable, it is easy to cause secondary disintegration. In addition, when the intermittently impingement on the impingement plate with LAWS, the splash ratio is around 0.6. If an injection period becomes longer, liquid film will become thick and the splash ratio will fall bout 10 percent. On the other hand, when the injection period of an intermittent spray is long, the same time lapse as a continuous spray is shown.

• 동력기계공학회지
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• 제14권1호
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• pp.16-21
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• 2010

This research focused on the spray and distribution characteristics of urea solution by applying flow visualization techniques and did durability and driver test on injectors as well. The spray characteristics of urea solution was observed by CCD camera. Also, the distribution characteristics of urea solution was evaluated quantitatively as well by using 3D laser scanner equipment. It was considered that it was reasonable to use the injector for gasoline engine in order to inject the urea. The best distribution chart result was observed near 45cm distance difference between catalyst and urea spray injector. As a result of trapped urea distribution chart analysis, optimal pressure and volumetric flow rates of air and urea were derived in order to improve the distribution of Urea. This information may contribute to provide fundamental data in the future.

• 오토저널
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• 제9권2호
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• pp.1-4
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• 1987

내연기관 연구에 전념하는 모든 사람들의 한결같은 3대 염원은 연비향상, 비출력증대 및 유해 배기가스 성분 감소이다. 이중 비과급 가솔린 기관의 경우 비출력 증대를 위한 4-stroke cycle 엔진에서의 여구는 현지까지 헤아릴 수 없이 많은 연구가 진행되어 발전의 한계에 도달한 느낌 이다. 따라서 이의 실질적인 증대는 시각을 달리하여 2-stroke cycle로의 전환으로서만 가능하리 라 본다. 2-stroke 엔진은 원래 이목적으로 고안된 것이라는 것은 주지의 사실이다. 그러나 이 장치가 비출력면에서 효과적인 가솔린엔진의 경우에서도 현재까지 별로 각광을 받지 못한 것은 다음과 같은 몇가지 두드러진 이유 때문이라고 본다. 첫째 흡입연료의 일부가 소기(scavenging) 과정에서 배기공으로 곧바로 유출됨으로 배기 공해성분을 증가시키고 연료손실에 따른 연비저감 을 초래하는 것이다. 둘째로 crankcase 소기를 이용하는 소형가솔린 2-stroke 엔진에서는 새 공 기의 흡입이 충분치 못하여 일방적으로 높지 않은 소기효율을 고려한 최종 흡입 체적효율은 상당 히 낮아지게 됨으로써 목적하는바의 비출력 증대의 득을 별로 얻지 못함은 물론 잔류가스율이 높아 저부하, 저속도에서 엔진의 구동이 손조롭지 못ㅎ하고 시동이 어려워지는 특성을 나타나게 된다. 따라서 이러한 바람직하지 못한 결과를 감수할 수 있는 경우에는 소형원동기에 주로 2-stroke 가솔린 엔진이 이용되어 왔다. 요사이 이러한 약점들을 타개할 수 있는 고안들이 미국 SAE지에 소개되어 관심을 끌고 있어 이에 대해 요저먹으로 소개하고자 한다.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.28-35
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• 2000

As a second part of the comparison study, microscopic features of an air-assisted fuel injector(AAFI) and a high-pressure swirl injector (HPSI) were characterized. They consist of the internal spray structure in terms of fuel mass and drop diameter, the overall atomization performance with respect to operating parameters and the drop size distribution. Large droplets are concentrated in around the head part of a spray field of the HPSI, while in the case of the AAFI, they were distributed in the tail part. Although the AAFI showed the better atomization performance, the feasible ranges of operating parameters such as injection and ambient pressure were found to be wider in the HPSI. Drop size distribution of the AAFI sprays was more dispersed than that of the HPSI. Drop size distribution of the AAFI sprays was more dispersed than that of the HPSI. However, at the well-atomized condition, it appeared to be very uniform.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.47-53
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• 2000

To overcome the shortage of conventional TWC that is activated at high temperature, higher than 25$0^{\circ}C$, photocatalyst is considered as an new technology. Because the photocatalytic reaction of photocatalyst is not a thermo mechanical reaction, it is necessary to heat the system to start the reaction. It can be activated just by ultra violet light that includes wavelengths shorter than 400 nanometers even at ambient temperature. In this study photocatalytic reduction of hydrocarbon was investigated with a model gas test. To understand the effects of co-existence gases on the hydrocarbon reduction by photoreaction, CO and NO, $O_2, H_2O$ gases those are components of exhaust gases of gasoline engine are supplied with C3H8/N2 to a photoreactor. The photoreactor contains $TiO_2$ photocatalyst powders and a UV bulb. The results show that oxygen is the most important factor to reduce HC emission with photocatalyst. Photocatalyst seems to have a good probability for automotive application to reduce cold start HC emissions.

• 한국분무공학회지
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• 제3권1호
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• pp.19-26
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• 1998

The effect of mixture component makes a nelay time and a long total combustion period $\tau_{p\;max}$. The flame propagation delay $\tau_{df}$ was determined by the record of current ion. The pressure release delay $\tau_{dp}$ and $\tau_{p\;max}$ were determined by the indicated pressure diagram in constant volume of the combustion chamber. The results are as follows: 1) The ignition delay $\tau_t$ time takes the minimum value around $\Phi=1.15$. 2) $\tau_{df}$ and $\tau_t$ time increased according to the increases of the concentrated dilution gases, because the adiabatic flame temperature decreased due to the increases of the heat capacity. But dilution gases have little effect on flame nucleus formation delay 3) The relation between $\tau_t$ time and reciprocal laminar burning velocity is almost linear. 4) The increase of the propagation length is accompanied with increased ratio of the $\tau_{df},\;\tau_{dp},\;\tau_{t},\;\tau_{p\;max}$.

• 한국분무공학회지
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• 제12권4호
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• pp.211-219
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• 2007

The liquid film thickness inside a pressure-swirl nozzle was measured, and then the measured liquid film thickness was compared with the results from previous empirical equations. The liquid film inside the nozzle was visualized using extended transparent nozzles and a microscopic imaging system, and then the measurement error was evaluated using optical geometry analysis. The high injection pressures up to 7MPa were adopted to simulate the injection conditions of the direct-injection spark-ignition engines. The totally different two injectors with different fuels, nozzle lengths, nozzle diameters and swirlers were utilized to obtain the comprehensive equations. The results showed that the liquid film thickness very slightly decreased at high injection pressures and the empirical equations overestimated the effect of injection pressure. Most of empirical equations did not include the effect of nozzle length and swirler angle, although it caused significant change in liquid film thickness. A new empirical equation was suggested based on the experimental results with the effects of fuel properties, injection pressure, nozzle diameter, nozzle length and swirler angle.

• 한국분무공학회지
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• 제22권1호
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• pp.8-12
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• 2017

Recently, manufacture and sales of passenger car with GDI (Gasoline Direct injection) were dramatically increased in Korea. In this study, investigation on the exhaust emission characteristics of GDI vehicles according to mileage were conducted by using chassis dynamometer and emission analyzer. Test cars selected 5 types with G4FD engine (1600 cc) and emissions of total 14 vehicles analyzed. Measurement and evaluation on emissions (CO, NOx, NMOG, $CO_2$) characteristics of GDI vehicles with mileages from 40,000 to 80,000 km in certification driving cycle (CVS-75) were carried out in this study. It is revealed that emission results of all test cars shows below emission standard, NMOG emission value of about 80,000 km doubled that of 40,000 km and emission increased by accumulated mileage. Also, increasing pattern of NOx emissions shows when the vehicle mileages was increased and $CO_2$ emission increasing trend obviously do not show according to mileages.