• 에너지공학
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• 제5권1호
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• pp.42-49
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• 1996

천연가스는 기존 내연기관의 구조를 크게 변경시키지 않고도 사용이 가능하며, 저공해성, 안전성, 내구성 등에 있어서 우수한 특성을 가지고 있고, 매장량이 풍부하다는 점에서 자동차용 대체연료로서 유망시 되고 있다. 본 연구에서는 기존 가솔린 기관을 CNG 전용기관으로 개조한 후, 공연비, 점화시기 등과 같은 기관 운전조건들을 최적화한 CNG전용기관을 기존 가솔린차량에 탑재하여, 샤시동력계상에서 연료소비량 및 배기배출물 농도를 측정·비교하였다. 또한, 실도로상에서 가속성, 운전성 등의 차량 주행특성에 대해서도 평가하였다. 그 결과, 시작 CNG차량의 경우에는 가솔린 차량에 비하여 연비는 향상되었고 배기배출물은 저감되었으나 출력은 약간 감소되었다.

• 한국가스학회지
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• 제28권2호
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• pp.1-6
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• 2024

구형 디젤 엔진들을 대체할 수 있는 손쉬운 접근 방식은 CNG나 LPG와 같은 연료를 활용한 가스 엔진으로 대체하는 것이다. 그러나, LPG와 같은 연료는 대형 가스 엔진에 적용된 사례가 많지 않아서 CNG 연료를 기반으로 하는 가스 엔진에서의 성능을 예측하기가 쉽지 않다. 이에 본 연구에서는 CNG 기반 대형 가스 엔진에 LPG 연료를 적용하여 성능과 배출가스 특성이 어떠한지 살펴보았다. 특히, NOx 저감을 위해 널리 사용되는 EGR 적용 시에 어느 정도의 효과를 보이는지에 대해서도 시험을 통해 결과를 확인하였다. 그결과, LPG의 경우에는 심각한 노킹을 배제할 수준까지 운전 조건을 확보하였음에도 고부하에서 약한 수준의 노킹은 여전히 CNG보다는 빈도수가 높음을 알 수 있었고, 다만 고속 영역에서는 CNG와 유사한 출력 수준을 확보할 수 있었다. CNG보다는 빠른 연소 속도로 인해 LPG의 효율이 높았고, EGR 적용을 통해 NOx는 물론 동시에 약한 노킹의 빈도수를 동시에 저감 가능할 수 있음을 확인하였다.

• 한국환경과학회지
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• 제21권2호
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• pp.241-251
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• 2012

The emissions of several air pollutants ($NO_x$, CO, VOCs, etc.) for the replacement of all diesel buses by Compressed Natural Gas (CNG) buses were estimated in the Busan Metropolitan Area (BMA). These emissions were calculated from emission factors considering the different driving speeds with bus routes, distance traveled, and deterioration factors. For the purpose of this study, three categories of fuel type were selected: (1) the combination of diesel (65%) and CNG buses (35%) (DSL+CNG case), (2) all diesel buses (DSL case), and (3) all CNG buses (CNG case). The emissions of $NO_x$ and CO in the CNG case were estimated to be significant decreases (by about 50% and 98%, respectively) relative to the DSL case. Conversely, the emission of VOCs (980.7 ton/year) in the CNG case were a factor of 3.3 higher than that (299.8 ton/year) in the DSL case. In addition, the diurnal variations of emissions between two city buses (e.g. diesel and CNG) and all other vehicles were distinctly different because the two city buses operate at a regular time interval. Our overall results suggest the possibility that the pollutant emissions from the CNG buses can exert less influence on air quality in the target area than those from the diesel buses.

• 한국가스학회지
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• 제24권1호
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• pp.41-48
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• 2020

본 연구는 기존의 CNG충전소에 복합으로 수소충전소를 건설하는 형태의 수소-CNG 복합충전소에 대한 정량적 위험성평가를 수행하였다. 수소충전소와 CNG충전소에서 발생할 수 있는 사고시나리오를 도출하고 각 시나리오에 대한 사고발생빈도를 고려하여 개인적, 사회적 위험도를 계산하였다. 위험성평가 결과 사회적 위험도는 허용가능 범위에 들어 왔으나, 개인적 위험도에 있어서는 일부 지역에서 허용범위를 벗어나는 구간이 발생하였고, 위험성기여도 분석을 통해 고위험요소를 발굴하였다. 수소-CNG 복합충전소에서는 CNG 저장용기, 압축기, 제어 판넬에서 대규모 누출이 발생할 경우 높은 위험도를 보이게 되며 충전소 전체 위험도의 약 88%를 기여하게 된다. 따라서 이러한 고 위험요소에 대하여는 주기적이고 집중적인 안전관리가 이루어져야 한다.

• 한국분무공학회지
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• 제19권1호
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• pp.40-46
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• 2014

Recently rise in oil prices feet the burden on not only diesel vehicle driver but also LPG vehicle driver, and get interested in various way to reduce fuel costs. In this study discuss on exhaust emissions characteristics on driving cycle mode and ignition advance condition change of CNG/LPLI Bi-Fuel vehicle. Experimental test was performed by changing the conditions of fuel (LPG/CNG), spark advance (Base, $10^{\circ}CA$, $15^{\circ}CA$), and driving mode (FTP-75, HWFET, and NEDC). In case of CO emission, in the order of CNG Base, CNG S/A10, S/A15 condition are average reduced -21%, -35%, -29% respectively compared to LPG fuel. The active emission reduction from the initial engine start, spark retard is likely to be beneficial in catalyst warm-up and improve combustion stability rather than spark advance.

• 한국분무공학회지
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• 제21권1호
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• pp.47-52
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• 2016

This paper describes the modeling of CNG direct injection using gaseous sphere injection model. Simulation of CNG direct injection does not need break up and evaporation model compared to that of liquid fuel injection. And very fine mesh is needed near the injector nozzle to resolve the inflow boundary. Therefore it takes long computation time for gaseous fuel injection simulation. However, simulation of CNG direct injection could be performed with the coarse mesh using gaseous sphere injection model. This model was integrated in KIVA-3V code and RNG $k-{\varepsilon}$ turbulence model needs to be modified because this model tends to over-predict gas jet diffusion. Furthermore, we preformed experiments of gaseous fuel injection using PLIF (planar laser induced fluorescence)method. Gaseous fuel injection model was validated against experiment data. The simulation results agreed well with the experiment results. Therefore gaseous sphere injection model has the reliability about gaseous fuel direct injection. And this model was predicted well a general tendency of gaseous fuel injection.

• 동력기계공학회지
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• 제16권5호
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• pp.5-12
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• 2012

희박예혼합기의 급속연소에 관한 연구를 위하여 2-실린더 가솔린 엔진을 부실 타입의 압축천연가스(CNG) 분사 엔진으로 개조하였다. 본 연구에서는 부실의 최적설계에 관심을 두고 두 종류의 부실을 적용하여 실험을 실시하였고, 부실의 체적과 홀 개수는 1.5cc와 6개로 각각 동일하게 하고, 홀 직경을 0.8mm 및 1.1mm로 달리하였다. CNG연료는 포트연료분사(Port fuel injection; PFI)와 부실분사(Sub-chamber injection; SCI)에 의해 엔진에 독립적으로 공급되고, 그 실험결과로 구한 연소압력, 평균유효압력(IMEP), 질량연소분율과 사이클변동계수(COV) 등을 서로 비교하였다. 본 연구의 대표적 실험연구결과로서 PFI 타입의 엔진연소특성은 희박예혼합기의 경우를 제외하고 모든 조건에 있어서 기존의 가솔린 엔진과 비슷하였고, SCI 타입의 엔진연소특성으로 평균유효압력은 부실 내에 불완전 예혼합기형성으로 PFI 타입보다 낮았으며, COV는 SCI 타입이 희박가연한계가 확대됨으로 인하여, 특히 높은 공기과잉률 범위에서 PFI 타입과 비교해 보다 좋은 결과를 나타내었다.

• 한국안전학회지
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• 제19권1호
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• pp.6-11
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• 2004

CNG buses were introduced in 2002 to reduce air pollution to the big cities. The durability and safety evaluation were performed for the NGV-2 type cylinders taken from two buses after 30 months of running. No external damage and no internal corrosion was observed on the container surfaces. Defect exceeding the allowable limit was not found in the UT test. Permanent volume expansion was about 1.2% which is much smaller than the required design limit. Cycling test showed no failure after 11,250cycles and burst pressures were still above the maximum design pressure. Both the longitudinal and circumferential failure mode were observed, where both the fracture strengths were far above the design limit. This study showed the present CNG fuel cylinders were safe enough for further usage.

• 한국생산제조학회지
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• 제23권2호
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• pp.103-108
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• 2014

Growing concerns about environmental pollution have led to an increase in the demand for compressed natural gas (CNG) vehicles in recent years. CNG vehicles are equipped with a cylinder valve installed in a high-pressure vessel to control the CNG flow. The cylinder valve must meet high quality safety standards because the pressure vessel stores high-pressure CNG. Therefore, safety evaluation of the cylinder valve is necessary to ensure the safety of CNG vehicles. In this study, fluid-structure interaction analysis for the structural integrity of the cylinder valve were conducted using a commercial finite element analysis code(ANSYS WORKBENCH V14). The CFD analysis was performed using a steady-state technique according to the inlet and outlet pressures in order to predict the pressure distribution. Structural analysis was performed by a static structure technique at the maximum working pressure to evaluate the structural integrity of the cylinder valve. From the results, the safety factor of the valve component is between 1.57 and 21.5.

• 한국분무공학회지
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• 제21권1호
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• pp.37-46
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• 2016

For the SI engines, at only full load, the pumping loss has a negligible effect, while at part load conditions, the pumping loss increases. To avoid the pumping loss, the spark-ignited engines are designed to inject gasoline directly into the combustion chamber. In the spark-ignited direct-injection engines, ignition probability is important for successful combustion and the flame propagation characteristics are also different from that of pre-mixed combustion. In this paper, a visualization experiment system is designed to study the ignition probability and combustion flame characteristics of spark-ignited direct-injection CNG fuel. The visualization system is composed of a combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. It is found that ambient pressure, ambient temperature and ambient air flow velocity are important parameters which affect the ignition probability of CNG-air mixture and flame propagation characteristics and the injected CNG fuel can be ignited directly by a spark-plug under proper ambient conditions. For all cases of successful ignition, the flame propagation images were digitally recorded with an intensified CCD camera and the flame propagation characteristics were analyzed.