• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.13-19
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• 2008

Among the various prime movers for combined heat and power (CHP) system, the CNG engine is the most commonly used power generation equipment of which power is less than 1MW. The 300 kW class CNG engine for CHP can meet stringent emission regulations with the adoption of stoichiometric air-fuel ratio control and three way catalyst. As the thermal efficiency of the stoichiometric ratio engine is lower than that of lean burn engine, it is necessary to operate the stoichiometric engine at its minimum spark advance for the best torque (MBT). However, knock control should be introduced for the engine under high intake air temperature conditions because MBT operating conditions are generally very close to those of knock occurrence. In this study, engine performances and knocking characteristics were experimentally investigated for the CNG engine that needs to be operated at higher intake air temperature conditions than normal conditions.

• Journal of Power System Engineering
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• v.22 no.6
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• pp.67-73
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• 2018

Gasoline that meets the quality standards is distributed in Korea. However, consumers who use toluene or solvent mixed with gasoline have appeared due to rising crude oil prices and for the purpose of tax evasion. Gasoline quality standard is enacted by the domestic and international research reference. A wrong fuel can influence automobile performance or environmental issue. Thus, empirical data from this issue is necessary. Therefore, this research observed catalyst influence by gasoline property change and inspect influence of environment. In this study, fuel property evaluation, lean-burn evaluation, and real vehicle exhaust emission test were performed. In the result of fuel property, the fuel "A" was measured to be up to 27% less octane than the normal gasoline and the distillation property was measured 24% higher than normal gasoline. In the test result of single cylinder engine lean-burn test, the fuels "A" and "B" show torque value 20% less than the normal gasoline. As a result of vehicle test using the catalyst, the fuel "A" was increased more than the normal gasoline with 83% THC, 1,806% CO and 128% NOx, and the fuel "B" was increased more than normal gasoline with 1.6% THC, 391% CO and 142% NOx.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.123-130
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• 2005

In this study, we evaluated the CH4 and CO conversion efficiencies over the oxidation catalysts for natural gas vehicle with lean-burn system. On the fresh catalyst, the conversion efficiency was increased when the loading of precious metal was increased. On the aged catalyst, the conversion efficiency was decreased as increasing the excess air ratio. We could confirm the measuring conversion efficiency of the unsteady state with the FTIR and that of steady state with the GC The temperature increasing ratio of unsteady state is acceptable from 3$^{\circ}C$/min. to 15$^{\circ}C$/min. for the evaluation of catalyst conversion performance , which has within the 4$\%$ of the difference of conversion efficiency. We observed a physical behavior of the thermal aged catalyst's surface using TEM and BET device. It was found that the precious metal was grown to the micro-scopic size by thermal aging process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.2 s.233
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• pp.180-188
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• 2005

It is well known that a lean burn engine caused by stratified mixture formation has many kinds of advantages to combustion characteristics, such as higher thermal efficiency and lower CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can achieve low fuel consumption technology, it produces much unburned hydrocarbon and soot because of heterogeneous equivalence ratio in the combustion chamber. Therefore, the stratified mixture formation technology is very important to obtain the stable lean combustion. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The local effect of mixture formation according to control air-fuel distribution in the chamber was examined experimentally. In addition, the effect of turbulence on stratified charge combustion process was observed by schlieren photography. From this study, we found that the flame propagation speed increase with swirl flow and the swirl promotes the formation of fuel and air mixture.

• International Journal of Automotive Technology
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• v.2 no.2
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• pp.63-75
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• 2001

This paper describes the development of THC reduction technologies compliant with SULEV regulations. Technologies embodied by the developmental work include improvement of fuel spray atomization, quick warm-up through coolant control shut of, and acceleration of fuel atomization for the fast rise of cylinder head temp inside the water jacket as well as the improvement of combustion state. The technologies likewise entail reduced HC while operating in lean A/F condition during engine warm-up with the cold lean burn technology, individual cylinder A/F control for improvement of catalytic converting efficiency, after-treatment such as thin-wall catalyst, HC-adsorber and EHC and etc, through vehicle application evaluation in cold start. We carried out an experimental as well as a practical study against SULEV regulations, and the feasibility of adopting these items in vehicle was likewise investigated.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.307-313
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• 2002

In the paper, the prototype development of a 75kW class microturbine for the distributed generation market is partly presented which has continued with the government funding. In the introduction, an overview of the development of microturbines in the world is presented. A series of development procedures are shown with design, manufacture and self-sustaining tests. During the first year, aerodynamic and structural design/analysis, mechanical design are performed for the compressor, the turbine and the combustor. A premixed lean burn combustor technology is used fur the low emission requirements. Foil air bearings and high-speed motors are employed for higher reliability. The self-sustaining conditions have been successfully achieved with the prototype manufactured engine as a preceding operation.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.66-79
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• 1993

To construct the design back data for a lean-burn gas engine, we have designed a constant volume combustion chamber with sub-chamber. With constant volume ratio of main-sub combustion chamber and constant equivalence ratio of methane-air mixture, the influence of geometric configurations(diameter, injection angle, number, length) of passagehole upon combustion characteristics were studied. It was found that combustion characteristics in the main combustion chamber were greatly influenced by the injection angle and length of passagehole.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.101-105
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• 1994

A/F sensor with a sensing and a pumping element, which is made of YSZ(yttria stabilized zirconia) sheets, can be used for the combustion control of lean burn engine. A/F sensor can detect the oxygen partial pressure in more wide range than the other oxygen sensors, such as the limiting current type oxygen sensor and λ-sensor. However this sensor has the disadvantage that the characteristics has been degraded rapidly due to the physical or electrochemical reasons. The blackening phenomenon is known as one of the degradations caused by high voltage biased for oxygen pumping. In this paper, we have studied to analyze the blackening phenomenon by comparing two characteristics between before and after blackening in impedance spectroscopy, and discussed the blackening mechanism.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.9-12
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• 2007

In this study, a new method of combustion characteristics have been proposed to reduce exhaust emissions in a diesel engine using four kinds of mixed fuel. Mixed fuels show four different torque ratios between diesel oil md natural gas, which are 4:0, 3:1, 2:2 and 1:3. In order to investigate the exhaust gas during combustion, exhaust gases are sampled by gas analyzer, for example NOx, Soot, CO, and HC, as the RPM changed. As a result, the NOx, CO, and HC concentrations of mixed fuel are higher than those of diesel oil only. However, the Soot concentration of mixed fuel is lower when diesel oil is burned.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.817-820
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• 2009

Research on usage of syngas produced by waste gasification is on going all around the world. Syngas which consists of $H_2$, CO, $CO_2$, $N_2$, has different combustion characteristics from current city gas; due to distinct flame propagation speed of the fuel, syngas has different spark timing and air fuel ratio at maximum generating efficiency. This is why finding both the optimum point of spark timing and air fuel ratio is so important in order to improve thermo efficiency and secure stable running of gas generated by relatively low heating value syngas. Moreover, since emission of $NO_x$ is strictly regulated, it is important to operate lean burn condition that reduces NOx emission.