• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.439-445
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• 2011

Forensic Engineering is the art and science of professionals qualified to serve as engineering experts in courts of law or in arbitration proceedings. Buses using compressed natural gas (CNG) trend to be extended in use internationally as optimal counterplan for reducing discharge gas of light oil due to high concern about environment. However, CNG buses have to be equipped with composite pressure vessels (CPVs); since the CPVs contain compressed natural gas, the risks in the case of accident is very high. Hence, the investigation of such accidents is usually associated with engineering analysis. Among the possible reasons for such CNG explosion accidents is vehicle fire and vessel fracture. By conducting formal inspection and engineering tests, in this study, the cause of vessel explosion is investigated by analyzing the failure mechanism by fractography and by comparing the material properties of a reference part with those of a problem part by adopting instrumented indentation technique.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.410-419
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• 2015

In this study, the roadability, fuel economy and emission characteristics were evaluated for a natural gas converted vehicle. The results are as follows; Not only the shortage of power was observed in stall test, but also large deterioration of acceleration performance was exposed in roadability. Compared to the original LPG system, the acceleration is 76% in start acceleration and 45 ~ 65% in overtaking acceleration, especially the decline became larger when air conditioner is at work. Furthermore, because the mapping data, which controls the injection depending on driving condition, do not match up with injection system, the failure of air-fuel ratio feedback control occurs resulting from the large gap between the required and the really supplied amount of fuel. This failure cause the exhaust gas to emit without catalytic conversion and the fuel economy based on the fuel heat value to get worse 22% in the mode test and 16% in road test respectively. In addition, the existing injection system does not secure enough fuel at the starting so that it may lead to the fail of clod start, the deterioration of hot start and inharmonic of engine at the idle after start.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.379-386
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• 2008

The 36 liter LNG tank is designed to fit in the limited installation space of a small truck. Two LNG tanks allow one ton truck to run about 432 km per fueling. which is about 1.8 times longer than CNG mileage for the same truck. The variation of BOG with car acceleration for the different fuel liquid/vapor ratios in a tank is analysed by the modified Fortran program "Pro-Heatleak". Computational analyses show that the relationship between the BOG and liquid/vapor ratio is linearly proportional at a given acceleration. Fuel consumption decreases the volume of liquid fuel in the tank but increases the specific BOG. BOG increases with increasing of car acceleration when fuel liquid/vapor ratio is greater than 0.5 and decreases with increasing of car acceleration when fuel liquid/vapor ratio is less than 0.5. The difference between maximum and minimum BOG for full tank is about 12 percents. For the fuel liquid/vapor ratio equal to 0.5 BOG does not depend on car acceleration.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.42-49
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• 1996

Natural gas is one of the promising alternative fuels for automotive vehicles, because it has lower exhaust emissions and better fuel economy characteristics than those of gasoline, and can be used in conventional gasoline engines without major modifications. In the present study, a conventional gasoline engine was modified to a CNG engine, which can be operated with CNG only, and an engine bench test was performed to calibrate the operating parameters of the engine such as air fuel ratio, spark advance, etc. at various operating conditions. The modified CNG engine, then, was installed on a commercial gasoline vehicle and a vehicle driving test on chassis dynamometer was performed to examine the fuel economy and exhaust emission characteristics. As a result, the prototype CNG vehicle showed lower exhaust emissions and better fuel economy characteristics, but slightly reduced brake horse power, compared to the gasoline vehicle.

• Steel and Composite Structures
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• v.45 no.5
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• pp.641-652
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• 2022

Fluid-conveying tubes are widely used to transport oil and natural gas in industries. As an advanced composite material, functionally graded carbon nanotube-reinforced composites (FG-CNTRC) have great potential to empower the industry. However, nonlinear free vibration of the FG-CNTRC fluid-conveying pipe has not been attempted in thermal environment. In this paper, the nonlinear free vibration characteristic of functionally graded nanocomposite fluid-conveying pipe reinforced by single-walled carbon nanotubes (SWNTs) in thermal environment is investigated. The SWCNTs gradient distributed in the thickness direction of the pipe forms different reinforcement patterns. The material properties of the FG-CNTRC are estimated by rule of mixture. A higher-order shear deformation theory and Hamilton's variational principle are employed to derive the motion equations incorporating the thermal and fluid effects. A two-step perturbation method is implemented to obtain the closed-form asymptotic solutions for these nonlinear partial differential equations. The nonlinear frequencies under several reinforcement patterns are presented and discussed. We conduct a series of studies aimed at revealing the effects of the flow velocity, the environment temperature, the inner-outer diameter ratio, and the carbon nanotube volume fraction on the nature frequency.

• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.40-47
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• 2010

Calorific value of mixed gas, like liquefied natural gas (LNG), is strongly depends on its compositions which are affected by the mining place and producing time. The variation in calorific value have an direct influence on the combustion characteristics and performances of boiler, burner, vehicle, power plants etc. Thus, developing experimental method to measure exact calorific value is becoming an issue in the related industrial fields. Flame calorimeter is developed to get calorific value at the dynamic equilibrium state using electric substitution method. Refrigerant-11 carries heat from combustor and/or heater to the Peltier elements which pumped it out to the cooling water. It is found out that error in the measured calorific value of methane is 2.86% compared with the theoretical one. Developed design technique and the experimental data will be applied to design the national standard gas calorific value measuring apparatus.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.29-33
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• 2009

In this study, the strength safety of a composite fuel tank which is fabricated by an aluminum liner of Al6061-T6 materials and composite layers of carbon/epoxy-glass/epoxy composites has been analyzed by using a finite element analysis technique. In order to enhance the durability of the composite fuel tank, an autofrettage process was used and compressed natural gas was supplied to the prestressed fuel tank. The FEM computed results on the stress safety of autofrettaged gas tanks were compared with a criterion of design safety of US DOT-CFFC and Korean Standard. The FEM computed results indicated that the stress safety of autofrettaged fuels tanks shows instability at the dome zone and uniform stability at the parallel body, which provide an evaluation data for a strength safety of autofrettaged composite fuel tanks. The computed results show that the stress safety of 9.2 liter composite fuel tanks satisfied the safety criteria of four evaluation items, which are provided by US DOT-CFFC and KS and indicated a safe design.

• Journal of the korean Society of Automotive Engineers
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• v.17 no.2
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• pp.1-6
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• 1995

천연가스 자동차의 배출가스 정화특성은 가솔린보다 우수하며 대기오염물질이 전반적으로 매우 낮아 천연가스 자동차의 저공해성을 확인할 수 있다. 이를 위한 촉매개발 기술에서는 Pb촉매가 메탄의 산화에 유리하며, 촉매구조는 Single-bed 보다 Dual-bed type이 메탄의 정화율에 유리하다는 것을 알았다. 각종 배기성분의 공존영향에서는 공존하는 NOx, H$_{2}$O가 메탄의 산화반응을 억제하는 요인으로 작용함을 알았다. 그리고, 천연가스 전용촉매는 초기 내구성이 급격히 저하하는 특성이 있는데, 이는 Lanthanoid 조촉매를 사용하므로써 개선의 가능성을 보이고 있다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2000.11a
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• pp.33-38
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• 2000

최근 들어 환경문제, 특히 대도시 대기오염으로 저공해자동차의 보급에 관심이 대두되고 있는 가운데 전세계적으로 많이 활용되고 있는 천연가스자동차(Natural Gas Vehicle)가 국내에서 높은 관심과 함께 서울을 비롯한 대도시를 중심으로 보급이 추진 되고 있다. 현재 정부는 심각한 대기오염을 줄이기 위해 월드컵이 열리는 2002년에는 5000대, 그리고 2007년까지는 서울, 부산 등 7대 도시에서 운행되고 있는 시내버스 2만 여대를 천연가스 연료로 전환할 계획을 세우고 있다. (중략)

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.911-915
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• 2007

This paper deal with the design concept of traction motor for Bimodal low floor vehicles that are CNG(Compressed Natural Gas) hybrid bus and Fuel-cell bus. The design concept of the traction motor is studied in terms of electrical characteristics and mechanical construction. Finally, this paper introduces the characteristic of the traction motor for low floor vehicles which are applied in the world, and mentioned the detail design concept of traction motor.