• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.146-153
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• 2013

CNG buses has contributed to improve air quality in cities. But it is difficult to meet the next emission regulations such as EURO-VI without the help of additional post-processing device. Hydorgen has higher flame speed and lower combustion temperature that make it thermal efficiency increase with leaner operation. Using hydrogen natural gas blend (HCNG) fuel is promising technology which can reduce $NO_x$ and $CO_2$ emissions for a natural gas vehicle. However, fuel flow rate of HCNG should be increased since hydrogen's energy density per volume is much smaller than natural gas. In the present study, the characteristics of fuel supply system and its applicability were evaluated in a heavy duty natural gas engine. The results showed that the potential of fuel pressure regulator and fuel metering valve had enough capacity with HCNG. Employed mixer did not affect the distribution characteristics of mixture.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.147-157
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• 1996

Natural gas is gaining more attraction as a future fuel in particular both for environmental protection and energy conservation. In order to bring about more widespread use of gaseous engines, the technology capable of achieving output and efficiency performance equivalent to that of diesel engines needs to be developed. In the present paper, the requirements of the pilot torch from pre-chamber for ensuring ignition and promoting combustion are discussed by means of taking high-speed flame photography and system can run with leaner mixture of various fuels comparing to the electric plug ignition system cause the ignition delay period ignited with the torch and the combustion period are very short in spite of changing A/F of gaseous fuels in the main chamber. However, the suitable piston-cavity design for the use of lower-hydrocarbon fuels such as propane and butane must be discussed increasingly in the mear future.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.148-155
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• 2005

In this study, Development of 300,000kcal/hr high velocity Injection burner with fuel multi-stage was performed using experiments. The characteristics of NOx emission in multi fuel/air staged combustor have been experimentally studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is largest access air combustion and the secondary flame is complete combustion zone, where most of fuel bums. Experiments were performed on an industrial scale in a laboratory furnace and Liquefied Natural Gas(LNG) was used as primary and secondary fuels. Comparison of outlet NOx and outlet Temperature under various air rate and primary/ secondary fuel ratio was performed. The test demonstrated that NOx emission con be reduced by 70% in accordance with operating conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.509-518
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• 1995

A study for the flame stability and the combustion characteristics of coaxial diffusion flame was conducted. The fuel employed was natural gas. The experimental variables were rim thickness of fuel tube, blockage ratio of the outer diameter of fuel tube to the inner diameter of air tube, and momentum ratio of fuel to air. It was consequently found that the stability in the neighborhood of the fuel rim depended on the rim thickness, especially in the case of above 3 mm, and that the stable region of the flame extended remarkably due to the formation of recirculation zone above rim. The effect of the blockage ratio on the flame stability was found to be minor in the case of above 3 mm of rim thickness. Between the momentum ratio 2 and 3, the stable flame zone was widely established as well good combustion. With increasing the fuel-air momentum ratio, axial velocity, turbulence intensity, and Reynolds stress increased.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.139-146
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• 2001

The experimental study was carried out for the diffusion flame characteristics of second stage combustor with the variations of temperature and supplying rate of hot exhaust gas from first stage combustor. It also examined the flame structure and NOx formation of the second stage combustor in which the fuel(natural gas) is supplying into the mixture of oxygen hot exhaust gas from first stage combustor. The results show that the increasement of temperature and flow rate of exhaust gas lead to increase the NOx up to 30ppm with 19% $O_2$ condition

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.221-223
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• 2012

Since gas turbine using biogas can reduce carbon dioxide ($CO_2$), the biogas gas turbine is becoming more attractive to renewable energy utilization business sector. Natural gas and $CO_2$ mixture was used to simulate the biogas fuel. At the experiments pressure losses, pattern factor, and emissions were measured. The results revealed that methane concentrations of the fuel mixture showed little effects on the combustor performance except emissions. As methane concentrations in fuel decreased, emissions measured at the exit of the combustor decreased.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.107-112
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• 2010

A gas turbine consists of an upstream compressor and a downstream turbine with a combustion chamber, and also the compressor and the turbine are generally coupled using a single shaft. Large scale gas turbine compressor is designed as multi-stage axial flow and the blade is fan-type which is thick and wide. Recently radial cracking happens occasionally at the compressor blade tip of large scale gas turbine. So, FEM was performed on the compressor blade and vibration modes and dynamic stresses were analyzed. According to the analysis, 9th natural frequency mode of the blade, which is 2 strip mode, is near the vane passing frequency by the vane located at the upstream of the blade.

• International Journal of Automotive Technology
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• v.7 no.1
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• pp.1-7
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• 2006

The ignition delay of a dual fuel system has been numerically investigated by adopting a constant volume chamber as a model problem simulating diesel engine relevant conditions. A detailed chemical kinetic mechanism, consisting of 28 species and 135 elementary reactions, of dimethyl ether (DME) with methane ($CH_{4}$) sub-mechanism has been used in conjunction with the multi-dimensional reactive flow KIVA-3V code to simulate the autoignition process. The start of ignition was defined as the moment when the maximum temperature in the combustion vessel reached to 1900 K with which a best agreement with existing experiment was achieved. Ignition delays of liquid DME injected into air at various high pressures and temperatures compared well with the existing experimental results in a combustion bomb. When a small quantity of liquid DME was injected into premixtures of $CH_{4}$/air, the ignition delay times of the dual fuel system are longer than that observed with DME only, especially at higher initial temperatures. The variation in the ignition delay between DME only and dual fuel case tend to be constant for lower initial temperatures. It was also found that the predicted values of the ignition delay in dual fuel operation are dependent on the concentration of the gaseous $CH_{4}$ in the chamber charge and less dependent on the injected mass of DME. Temperature and equivalence ratio contours of the combustion process showed that the ignition commonly starts in the boundary at which near stoichiometric mixtures could exists. Parametric studies are also conducted to show the effect of additive such as hydrogen peroxide in the ignition delay. Apart from accurate predictions of ignition delay, the coupling between multi-dimensional flow and multi-step chemistry is essential to reveal detailed features of the ignition process.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.28-46
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• 2001

Natural gas is a mixture of hydrocarbon gases and impurities such as nitrogen, hydrogen sulfide, and carbon dioxide and a clean energy producing no pollution materials for combustion. Currently, the demand of the natural gas is rapidly increasing due to worldwide environmental problems. According to Hubbert's study in the past, the natural gas was predicted as rapidly depleted resources, and then the results led to high gas price and limitation of usage during 1980s. Afterward, the study of natural gas resources based on geology identified the additional natural gas resources that were not considered in Hubbert's study. They are unconventional gas, additional resources in the existed reservoirs, and natural gas in deep subsurface areas. Such additional resouces made the future of natural gas bright and pormised low and stable gas price in the future. Deep natural gas is defined as the gas existing at or below 15,000ft$(4,752{\cal}m)$ in depth from the surface. According to the study from the U.S. Geological Survey(USGS) in 1995, 1,412 TCF of technically recoverable natural gas was remained to be discovered or developed in the onshore of United States. A significant part of that resource base, 114 TCF, exists at deep sedimentary basins, and it shows wide distribution with various geological environments. In 1995, the deep gas contributed to $6.7\% of total supply amount of natural gas in the United States and is expected to be $18.7\% by 201.5. However, the development of the deep gas is a high risky business due to expensive investment and high portion of dry holes, although it is developed. Thus, for developing the deep gas economically, it is necessary to overcome many technical challenges. In this paper, for increasing success rate of the deep gas, 1) geologic and compositional characteristics, and production cost have been analyzed according to depth, 2) technical problems related to deep gas production have been summarized, and 3) finally future study areas for increasing application of the deep gas have been suggested. For reference, this paper was written based on the study results from USGS and Gas Research Institute(GRI), for the United States is doing the most active R&D in the deep gas area, and thus, has many reliable data.

• Journal of Ocean Engineering and Technology
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• v.35 no.6
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• pp.393-402
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• 2021

As greenhouse gas emissions from maritime transport are increasing, the International Maritime Organization is continuously working to strengthen emission regulations. Liquefied natural gas (LNG) fuel is less advantageous as a point of CO₂ reduction due to the methane leakage that occurs during the bunkering and operation of marine engines. In this study, greenhouse gas emissions from an LNG-fueled ship were analyzed from the perspective of the life cycle. The amount ofmethane emission during the bunkering and operation procedures with various boil-off gas (BOG) treatment methods and gas engine specifications was analyzed by dynamic simulation. The results were also compared with those of other liquid fuel engines. As a result, small LNG-fueled ships without a BOG treatment facility emitted 32% more greenhouse gas than ships utilizing marine gas oil or heavy fuel oil. To achieve a greenhouse gas reduction via a BOG treatment method, a gas combustion unit or re-liquefaction system must be mounted, which results in a greenhouse gas reduction effect of about 25% and 30%. As a result of comparing the amount of greenhouse gas generated according to the BOG treatment method used with each tank size from the perspective of the operating cycle with the amounts from using existing marine fuels, the BOG treatment method showed superior effects of greenhouse gas reduction.