• 한국자동차공학회논문집
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• 제7권8호
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• pp.17-23
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• 1999

This paper presents the characteristics of the gas flow in the engine cylinder under various intake flow conditins. The particle tracking velovimetry(PTV) was used to anlayze the gas flow pattern and flow field in the cylinder. Effects of tumble intensifying valve(TIV), swirl intensifying valve(SIV) and one-valve deactivated condition on in-cylinder flow patterns were compared with the baseline engine udner 600rpm motoring condition. In addtion, tumbel ration was estimated rwith results of in -cylinder flow fields. Base on experimental results, the tumble ration of in-cylinder flow field has the maximum value at the bottom dead center for the different four inlet conditions. In TIV condition, the tumble ration is 1.35 times larger than that of baseline engine and 1 intake valve deactivated condition is effective to improve in-cylinder swirl motion.

• 동력기계공학회지
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• 제14권3호
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• pp.13-18
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• 2010

HCCI engines fueled DME and natural gas have been studied on single-cylinder engine due to availability of reducing on $NO_X$ and PM simultaneously without deteriorating into high thermal efficiency, and thus it is clarified that higher maximum engine load is achieved as DME equivalence is smaller. In this study, combustion tests were accomplished on multi-cylinder engine for practical use of it. When minimum DME equivalence achieved maximum engine load on single-cylinder engine was applied to 4-cylinders engine, there was in unstable running condition that engine revolution fluctuated greatly and cyclically. It is the reason what misfire occurred intermittently with one the same as minimum DME equivalence on single-cylinder due to increase in energy for ignition at No. 1 cylinder with lower cylinder liner temperature. Maximum engine load was achieved by adopting EGR, though it decreased because of knocking at smaller engine load than single-cylinder due to increase in minimum DME equivalence.

• 한국유체기계학회 논문집
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• 제12권1호
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• pp.16-21
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• 2009

In the last five years, 91 accidents from portable gas ranges and non-refillable metallic gas cartridges have occurred. The gas cylinder installed with a relief valve was developed to prevent an explosive accident from the gas cartridge. In this study it was carried out to evaluate the safety of a gas cylinder mounted with a relief valve which can prevent an explosion. Under the real using condition and the extreme condition the gas cylinder is heated with an electric heater. Simultaneously, the operating pressure is checked and the suitability of releasing flux is evaluated. And the possibility of fire or explosion was tested when the gas was released from the relief valve at the real using condition. Using a numerical simulation method, the diffusion of butane gas released from a relief valve was visualized.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.82-88
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• 2001

The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.55-60
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• 2004

Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was suggested. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual gas fraction was derived by comparing the total charging and fresh air. This results coincide with measured EGR value very well.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1524-1532
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• 2001

The effects of recirculated exhaust gas on the wear of cylinder liner and piston were experimentally investigated by a two-cylinder, four cycle, indirect injection diesel engine operating at 75% lo ad and 1600 rpm. For the purpose of comparison between the wear rates of the two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot in exhaust emissions was removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors(A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out with the fuel injection timing fixed at 15.3$^{\circ}$ BTDC. It was found that the mean wear rate of cylinder liner with EGR was greater in the measurement positions of the second half than those of the first half, that the mean wear rate without EGR was almost uniform regardless of measurement positions, and that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR.

• 한국자동차공학회논문집
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• 제3권3호
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• pp.90-96
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• 1995

In general, natural gas engine converted from gasoline engine has disadvantage of power decrease. In order to increase power output in natural gas engine, the improvement of in-cylinder flow motion has been believed as the most effective method. In this study, the geometry of combustion chamber in 4 valve DOHC natural gas engine is modified, and in-cylinder flow patterns is analyized. Also engine performance is evaluated according to the modification of in-cylinder flow motion.

• 한국가스학회지
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• 제18권2호
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• pp.16-20
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• 2014

본 논문에서는 현재 캠핑 문화의 확산에 따라 수요가 증가하는 LGP 재충전 용기에 관한 내압성능을 실험적으로 검증하였다. 겨울철에 부탄가스는 높은 비점의 영향으로 기화가 쉽게 일어나지 않는 물적 특성을 지니고 있다. 하지만 프로판의 경우 비점이 낮아 겨울철에도 기화가 쉽게 일어나 연료로써 공급 필요성이 증가되고 있다. 하지만 프로판은 높은 증기압으로 인해 많은 안전상의 문제가 존재하며, 이를 극복하고 연로로써 유통되기 위해서는 안전한 용기의 공급이 우선시 되어야 한다. 국내외적으로 고압용 소형 재충전 용기의 보급을 시도하고 있으나, 프로판의 높은 증기압으로 인한 안전상의 문제로 제재가 되고 있다. 본 논문은 재충전 용기의 내압성능을 검증하기 위해 수압장치를 이용하여 용기의 가압 및 파열 실험을 수행하였다. 또한 고온에서 프로판의 증기압과 용기 파열시 수압과 비교하여 그 특성을 제시하였다. 수압가압 실험 및 파열 실험을 통해 토출 된 본 논문의 결과는 향후 소형 재충전 용기 개발 연구의 기초가 될 것으로 기대하며, 재충전 용기의 보급에 있어 기준 자료로 활용 될 것으로 사료된다.

• 한국기계가공학회지
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• 제16권5호
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• pp.13-18
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• 2017

In this work the augmented safety of Type 4 composite vessel in accordance with uniform-stress design has been demonstrated through a series of burst tests and structural analyses. For this end, three sample vessels were used: (1) designed as guided by the isotensoid dome theory (called iso-dome cylinder); (2) with dome longer compared to uniform-stress design (called prolate cylinder); and (3) with dome wider than uniform-stress design (called oblate cylinder). Structural analyses have been performed using ABAQUS finite element code based on the periodic symmetry to circumferential direction. As a result, the maximum stresses are induced around the bodies of all three cylinders. However, the analyses, with the assumption of possible defect demonstrate that the maximum stresses are induced around the dome knuckles for the prolate and the oblate cylinders. The results of the burst tests for the three cylinders show that the burst initiates from the cylinder body of the iso-dome cylinder and from the dome knuckles of the prolate and the oblate cylinders. Finally, it is recommended that, to comply with DOT CFFC 2007, the dome shape should be designed and fabricated as guided by the isotensoid dome theory.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.404-409
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• 2007

For a hermetic reciprocating compressor, it has been known that the gas pulsation in the suction line affects the compressor performance, and suction muffler design has been focused on both of noise reduction and minimum pressure drop across the muffler. Some studies have been carried out on the mutual interaction between the gas pulsation and the cylinder pressure to investigate some supercharging effects, but their efforts were limited on rather simple geometries. In this paper, interaction of the gas pulsation in the compressor suction line with cylinder pressure via suction valve motion has been calculated; for the gas pulsation analysis, modeling of Helmholtz resonators in series was used, and for cylinder pressure calculation, energy equations was set up for the gas inside the cylinder. For demonstration of this calculation method, four different types of suction line configurations for a hermetic reciprocating compressor were compared in terms of compressor performance and gas pulsation level.