• 한국자동차공학회논문집
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• 제16권4호
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• pp.47-55
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• 2008

Turbocharger has a main purpose on recycling of the exhaust gas from the engine cylinder. On the basis of the facility characteristics, the turbocharger supported on floating ring bearings has some problems such as the large volume, oil supplement for lubrication and high power loss due to high operating torque. The air foil bearing has been studied as the bearing element to be able to alternate the floating ring bearing without the problems of the floating ring bearing. In this study, the air foil bearing has 2 parts; journal and thrust bearings, and the test facility consists of the engine, exhaust and intake parts. In addiction, the specification of the turbocharger follows a small turbocharger for SUV engine. The engine speed is varied from 750 (idle rpm) to 2,500 rpm and then, the rotating speed of the turbocharger rotor is accelerated from 0 to 100,000 rpm. From those experiments, the comparison between the performances of the air foil bearing and floating ring bearing is conducted and the results show that the air foil bearing has less power loss, maximum 770 watt, than the floating ring bearing, maximum 5,110 watt. This result verifies that the air foil bearing is more efficient and able to output more power under the same condition of the input power.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.121-130
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• 2014

This paper is the second investigation on the effects of intake flow control methods on the part load performance in a spark ignition engine. In the previous work, two control methods, port throttling and masking, were compared with respect to lean misfire limit, fuel consumption and emissions. In this work, the effects of these two methods on EGR characteristics were studied and simultaneously the differences between EGR and lean combustion as a dilution method were investigated. The results show that EGR limit is expanded up to 23% and 3 ~ 5% improvement in the fuel consumption are achieved around 8 ~ 13% rates by the flow controls comparing with 10% limit and 1.5% reduction around 3% rate of non-control case. The masking method is more effective on the limit expansion than throttling as like as lean misfire limit; however there is no substantial difference in fuel consumptions improvement regardless the control methods except high load condition. Also it is observed that there exist critical EGR rates around which the combustion performance and NOx formation change remarkably and these rates generally coincide with optimum rates for the fuel consumption. In addition, dilution with fresh air is much more advantageous than that of the exhaust gas from the view point of dilution limit and fuel consumption, while utilization of the exhaust gas is more effective on NOx reduction in spite of considerably small dilution compared with the use of fresh air. Finally, the improvement of fuel consumption by massive EGR is highly dependent on the EGR limit at which the engine runs stably, therefore the stratified combustion technique might be a best solution for this purpose.

• 한국자동차공학회논문집
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• 제23권2호
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• pp.221-229
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• 2015

The PFI dual injection engine using one injector per an intake port was developed for solving the DISI engine cost problem. Excellent fuel atomization and targeting of the PFI dual injection engine made enhancement on the fuel efficiency and engine power. In order to develop a PFI dual injection engine, characteristics of the in-cylinder flow and fuel behavior with respect to fuel injection angle and cone angle of the PFI dual injection engine was investigated. Numerical calculation was conducted to analyze 3D unsteady in-cylinder flow and fuel behavior using STAR-CD. The engine operating condition was 2,000rpm at WOT. As a result, the amount of intake air, evaporated fuel and fuel film according to injection angle and cone angle were presented. The results were influenced by interaction between injected fuel and intake port wall.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.331-335
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• 2006

초음속 흡입구는 안정한 유동은 설계점에서 얻을 수 있지만, 비행 중 나타나는 비설계점에서는 흔히 버즈라고 불리는 공력 불안정성에 직면하게 된다. 버즈가 일어나는 동안, 흡입구는 흡입구 선단에 큰 충격파 진동이 나타나며 그에 따라 후류에는 압력 섭동이 발생하며 이는 엔진의 성능감소를 야기한다. 본 연구는 버즈의 일반적인 특성을 파악하기 위해 1단 꺽임각을 갖는 외부 압축식 축대칭 흡입구를 이용하여 실험적, 수치적 연구가 수행되었다. 본 연구를 통해 간헐적으로 나타나는 버즈를 관찰할 수 있었고 배압이 증가할수록 버즈가 일어나는 주파수가 커짐을 확인할 수 있었다.

• 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.

• Asian-Australasian Journal of Animal Sciences
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• 제16권8호
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• pp.1126-1130
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• 2003

The conditions of measurement for the determination of bulk density were evaluated to assess the bulkiness of 8 kinds of forage. The bulkiness of the forages was determined with 4 different sizes of forage samples with 7 different pressure application under air-dry and wet conditions. The dry bulk density (DBD) curvilinearly regressed with the pressure applied. The particle size of the samples and kinds of forage used in the present study did not affect changes in values of DBD determined under pressures over $20g/cm^2$ up to $200g/cm^2$. The values of the wet bulk density (WBD) increased as an increment of particle size, but were not always regressed on the particle size of the 8 kinds of forage. The DBD determined on 8 mm particles showed a higher correlation coefficient with neutral detergent fiber (NDF) contents. The DBD may be a useful tool for the assessment of NDF in forage, when it is determined under condition of a pressure of $100g/cm^2$ or over with a particle size of 8 mm. The WBD may not be utilized for the direct measurement of the physical characteristics of forage, but may be required a thorough consideration on water solubility of forages. Further studies are needed to clarify the DBD contribution to the prediction of forage intake by ruminants.

• 한국분무공학회지
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• 제1권2호
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• pp.33-41
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• 1996

Mixture formation is one of the important factors to improve combustion performance of MPI gasoline engines. This is affected by spray and atomization characteristics of injector. Especially, in the case of EGI system, air-fuel mixing period is too short and formed a lot of fuel-film in the intake manifold and cylinder wall. This fuel-film is not burnt in cylinder, it is exhausted in the form of HC emission. In this paper, spray characteristics such as size distributions, SMD, and spray angle are measured by PMAS, and the fuel-film measuring device is developed specially. Using this device, the amount and distribution of fuel-film which flows into through valve can be measured Quantitatively. As the result of these experiments, the information of optimal spray characteristics and injection condition that minimize the fuel-film can be built up.

• EDISON SW 활용 경진대회 논문집
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• 제1회(2012년)
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• pp.77-80
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• 2012

초음속 흡입구는 설계점에서 안정적으로 작동하지만 설계점 밖에서는 엔진성능이 급격히 감소하거나 층 격파 불안정 문제가 발생할 수 있다. 초음속 흡입구의 일반적인 특성을 파악하기 위해 2단 꺾임각을 갖는 외부 압축식 2차원 흡입구를 설계하고 EDISON_열유체 시스템을 이용하여 최종적으로 설계 마하수 2.5에서 작동하는 형상을 얻었다. 그러나 설계 마하수 이하의 영역에서는 충격파-경계층, 충격파간 상호작용으로 인해 유동에서 박리가 발생하고 최종적으로 흡입구 목을 질식시켜 아임계 상태로 천이된다. 이를 해결하기 위해 유동 제어 방법 중 하나인 bleeding을 이용하여 경계층을 제거하거나 유동의 박리를 방지하여 충격파를 cowl lip 전방에 안정하게 고정시킬 수 있었으며, 결과적으로 목적하였던 마하수 2.0에서 2.5에 이르는 작동 영역에서 강건하게 운용될 수 있는 초음속 흡입구를 설계하였다.

• 대한기계학회논문집
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• 제19권10호
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• pp.2690-2698
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• 1995

Fuel atomization and mixture formation in an gasoline engine has influence on the engine performance and pollutant emission. The throttle valve installed in an intake system plays a greater role in control of mixture quantity in accordance with engine drive condition. In this study, the characteristics of secondary atomization developed at the downstream of the valves were observed using an image processing method. Two major kinds of valves, solid and perforated ones, are chosen in order to compare the valve performance with the experimental parameters of air flow rate, valve opening angle, and valve shapes. For the perforated valve, we can obtain the relatively small sized droplets, and nearly uniformed and dense distributed sprays with low loss coefficient than for the solid valve.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.80-86
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• 1996

In order to decrease fuel comsumption rate and emissions, lean burn engine which has equipped swirl control valve, is investigated experimentally on the test bench. Single cylinder engine was used to test the combustion and emission performance with 4 kinds of swirl valve. Decrease in the carbon monoxide, hyerocarbon and specific fuel consumption was shown at the lean condition, which means that a good choice of swirl valve on the given intake port geometry can be used to increase the combustion efficiency and lean limit.