• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.40-46
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• 2015

Stoichiometric combustion engine with Three-way catalyst had an advantage that can reduce the harmful emissions effectively. Fuel equivalence ratio controlled from engine is very important because Fuel equivalence ratio with high conversion efficiency was narrow. This study analyzed the conversion efficiency under whole range of operating area for to evaluate the performance of three-way catalyst. In order to identify the Optimum conversion efficiency, the conversion efficiency due to change the control value of fuel equivalence ratio was investigated. The result show that conversion efficiency of emissions(more than 95%) has discovered by means of fuel equivalence ratio control at each test condition. As engine power increases, optimal fuel equivalence ratio tended to increase linearly under operating conditions of similar exhaust gas temperature.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.34-39
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• 2018

Natural gas is attracting attention as an alternative to existing fossil fuels. Natural gas has a high octane number. Therefore, knocking does not occur even if the compression ratio is increased, so that the thermal efficiency and the output can be improved. And it is relatively easy to apply the natural gas supply system to the internal combustion engine hardware system. In this study, a gasoline direct injection turbo engine was converted into a natural gas port injection type turbo engine. Therefore, the combustion and performance of the engine are measured and compared comprehensively in the region where the turbo operates.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2052-2060
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• 2006

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350$^{\circ}C$, and the test load was 1960 N. The test cycle number was $6.0{\times}10^6$. The mean ($\pm$standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 ($\pm$3.7)$\mu$m and 81.7 ($\pm$2.5)$\mu$m, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 ($\pm$3.9)$\mu$m and 91.2 ($\pm$2.7)$\mu$m, respectively. In the case of multi-Hz it was 70.7 ($\pm$2.4)$\mu$m and 77.4 ($\pm$3.8)$\mu$m, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.701-710
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• 2013

The purpose of this study is to investigate experimentally the effect of low purity methanol (LPM) on performance and smoke emission characteristics by using a four-cycle, four-cylinder, water-cooled, direct injection diesel engine with EGR system. The experiments are performed by the change of engine load in the engine load ranges of 25 to 100% with an interval of 25% under the constant engine speed of 2000 rpm. The LPM in the fuel blends contained 24.88% water by volume. The blended fuel ratios of diesel oil to LPM are maintained at 100/0, 95/5, 90/10 and 85/15% on the volume basis. In this paper, EGR rates are varied in three conditions of 0, 12.8 and 16.5%. The result shows that the brake power of a blended fuel with 15% LPM is reduced more 11.1% than that of the neat diesel oil at the full load with the EGR rate of 16.5%. At this condition, also, the brake specific fuel consumption (BSFC) is increased by 3.2%, the exhaust gas temperature is decreased by 10.7%, the smoke opacity is decreased by 18.7% and the brake thermal efficiency is increased by 7.3%. The sharp reduction of smoke opacity for a blended fuel with the LPM content of 15% at the full load without EGR system is observed by 68.4% compared with that of the neat diesel oil due to the high oxygen content of LPM.

• Journal of ILASS-Korea
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• v.16 no.4
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• pp.201-209
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• 2011

Optimum engine performance is obtained when the spray characteristics is well matched to the geometry of a combustion chamber. Among many parameters governing the combustion performance in internal combustion engine, fuel supply characteristics and atomization are important performance factors. Therefore, spray characteristics of high pressure multi-hole injector has been studied experimentally. An experimental test system has been made to operate high pressure injection system and to visualize spray behavior. Spray visualization has been performed to analyze spray formation, spray cone angle, bent angle and penetration length. Spray interaction with piston has been analyzed with various injector installation angle, injection pressure and ambient pressure. Test results show that penetration length is greatly influenced by the injection pressure. Penetration length is decreased as ambient pressure increased. Spray cone angle is increased as injection pressure and ambient pressure increased. However, bent angle is not influenced by the change of injection pressure and ambient pressure. Spray cone angle distribution map is plotted using the experimental data. Fuel movement around the spark-plug has been enforced as increasing injector installation angle.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.1-10
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• 2016

Cooling characteristics are investigated numerically in the chamber for high-performance burnout of wastes with solid phase. Before the combustion chamber is manufactured, combustion analysis is performed for evaluation of burning rate and cooling performance. A water cooling method is applied and its feasibility for cooling is examined depending on coolant flow rate. Another method of complex cooling is adopted by combining air film cooling with water cooling, leading to improved cooling performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.23-30
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• 2010

Trends of the automotive market require the application of new engine technologies, which allows for the use of different types of fuel. Since ethanol is a renewable source of energy and it contributes to lower $CO_2$ emissions, ethanol produced from biomass is expected to increase in use as an alternative fuel. It is recognized that for spark ignition (SI) engines ethanol has advantages of high octane number and high combustion speed. In spite of the advantages of ethanol, fuel supply system might be affected by fuel blends with ethanol like a wear and corrosion of electric fuel pumps. So the on-board hydrogen production out of ethanol reforming can be considered as an alternative plan. This paper investigates the influence of ethanol fuel on SI engine performance, thermal efficiency and emissions. The results obtained from experiments have shown that specific fuel consumption has increased by increasing ethanol amount in the blend whereas decreased by the use of hydrogen-enriched gas. The combustion characteristics with hydrogen-enriched gaseous fuel from ethanol reforming are also examined.

• Atmosphere
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• v.27 no.3
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• pp.317-329
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• 2017

Ocean mixed layer (OML) depth affects diurnal cycle of sea surface temperature (SST) induced by change of solar radiation absorption and heat budget in ocean. The diurnal SST variation can lead to convection over the ocean, which can impact on localized precipitation both over coastal and inland. In this study, we investigate the OML characteristics affecting the diurnal cycle of SST for the Korean Peninsula and surrounding areas. To analyze OML characteristics, HYCOM oceanic mixed layer depth (MLD) and wind field at 10 m from ERA-interim during 2008~2016 are used. In the winter, MLD is deeply formed when the strong wind field is located on perpendicular to continental slope over deep seafloor areas. Besides, cooling SST-induced vertical mixing in OML is reinforced by dry cold air originated from Siberia. The OML in summer is shallowly distributed about 20 m. In order to estimate the impact of OML model in high resolution NWP model, four experimental simulations are performed. At this time, the prognostic scheme of skin SST is applied in NWP to simulate diurnal SST. The simulation results show that CNTL (off-OML) overestimates diurnal cycle of SST, while EXPs (on-OML) indicate similar results to observations. The prediction performance for precipitation of EXPs shows improvement compared with CNTL over coastal as well as inland. This results suggest that the application of the OML model in summer season can contribute to improving the prediction for performance of SST and precipitation over coastal area and inland.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1009-1015
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• 2011

In this study, in the high expansion cycle was conduced by variable valve timing system composition to close intake valve late, and in the intake air reduction on the low compression was solved by supercharging pressure. In this wise, by constituting Diesel-Atkinson cycle, this study looked into a possibility of thermal efficiency improvement. As a result, there was improvement in thermal efficiency and output in a whole range of closing timing from ABDC $40^{\circ}$ to ABDC $80^{\circ}$. However, after ABDC $70^{\circ}$ of closing timing, the thermal efficiency increase was getting smaller. As the result of the study, the optimum intake valve closing timing was about ABDC $70^{\circ}$, high loading territory of engine was more effective than low loading territory, and engine operation in middle loading territory was stable. At this time, brake thermal efficiency was 12.5% higher than ordinary engine on average.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.107-114
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• 2013

In this paper, we propose controller to control the acceleration of unmanned aircraft turbojet engine. The high-gain observer to estimate the rotational speed of compressor is used, and the turbojet engine controller applying fuzzy heuristic techniques and PID control algorithm are designed. fuzzy PID controller produces the flow control input to prevent the surge and flame-out phenomena at the acceleration and deceleration of the turbojet engine. The standard acceleration is set and the fuel flow control is defined by the fuzzy heuristic. Computer simulations are performed using MATLAB in order to verify the performance of the proposed controller.