• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.99-106
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• 2010

A piezo-driven injector was applied with a purpose to evaluate the effect of induced voltage on spray characteristics. For this, injection rate, macroscopic imaging, ambient gas entrainment and particle sizing were carried out. It was shown that initial slope of injection rate was steeper as induced voltage increased, while slope of injection rate became mostly constant with fully opened needle. From macroscopoic imaging, longer spray tip penetration was produced with higher induced voltage. Moreover, wider spray angle was detected in the early stage of spray development, when higher induced voltage was applied. Ambient air entrainment rate was increased and particle size was reduced with higher induced voltage.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.7-12
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• 2005

In order to analyze the microscopic spray characteristics of free spray in ultra high pressure region, the droplets size and velocity of free spray injected under atmosphere condition were measured by PDPA. As injection pressure became ultra high pressure, the droplets size was decreased continuously due to the increase of mutual reaction between droplets and air. But the decreasing rate became moderate. The velocity was increased until 250 MPa, and then decreased over that of injection pressure. It was seemed that the droplet size was similar in range of $280\~350\;MPa$, but increased in 414 MPa, even though injection pressure was increased. The microscopic spray characteristics of free spray got worse in 414 MPa.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.155-163
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• 2007

The control of the fuel to be introduced into the combustion chamber under idling and low-load conditions is known to be a problem in Diesel engines, owing to the relatively small fraction of the full-load fuel needed under light loads. Thus, particular attention should be paid to the behavior of the injector with reference to short injection events. This work presents the results of an experimental campaign carried out with two different types of common rail injectors, a standard injector and a modified one. The latter, coming from a simple modification realized in a standard injector, exhibits linear behavior between injected fuel and solenoid energizing time in the field of short injections. A direct comparison of the two injection behaviors suggests a possible way to better control short or pilot injections.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.185-192
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• 2016

Low operational cost and high efficiency is absolute requirements in the mass production of the ship engine. Increasing the performance of the fuel injection system in the diesel engine is one kind of solution to improve the efficiency. Modern diesel engines are using electronic control module as the main controller in the fuel injection control system, however the mechanical system still involved in the modern control system. In modern ship engine, a control valve was used in injection fuel to regulate the flow of the fuel. High pressure and friction are intensively occur within this part, therefore high wear resist and low friction coefficient material including fine lubricating are needed. This study is to figure out the wear resist material and proper lubricant in the control valve fuel injection. The experiment has been tested using pin on disk in several treatments those are used various lubricants and non-lubricant condition. Two kinds of lubricant were used in this experiment such as INDERIN AW-32 and paraffin oil. INDERIN AW-32 has a better result compared to non-lubricant condition, which are 20% performance increases than non-lubricant condition. SCM 440 was providing small friction coefficient in the lower velocity. The friction coefficient was constantly maintains at 0.1 m/s of velocity or above respectively with the increment of the loads. Using INDERIN AW-32 and paraffin oil the lowest friction coefficient occurred at the lower load, and increases side by side with the increment of loads.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1199-1206
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• 2015

In this study, the exhaust gas of a diesel engine operating on biodiesel(BD) fuel(a mixture of diesel and soybean oil) was investigated for different fuel mixing ratios in the range of BD3 to BD100. The experiments were conducted using injection pressures of 400, 600, 800, 1000, and 1200 bar. The Pearson correlation coefficient and Spearman rank-order correlation coefficient were used to quantify the NOx and Soot emissions based on the fuel mixing ratio and injection pressure. Consequently, the Pearson correlation coefficient obtained for NOx and Soot emissions according to the mixing ratio and injection pressure was -0.811 and the corresponding Spearman rank-order correlation coefficient was -0.884, which indicated that the correlation of the NOx and Soot emissions was linear. Thus, the NOx and Soot have a trade-off relationship. Moreover, at each injection pressure, the Pearson correlation coefficient was a negative number, which indicated an inversely proportional relationship between NOx and Soot.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.32-38
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• 2006

Currently, due to the serious world-wide air pollution by substances emitted from vehicles, emission control is enforced more firmly and it is expected that the regulation requirements for emission will become more severe. A new concept combustion technology that can reduce the NOx and PM in relation to combustion is urgently required. Due to such social requirement, technologically advanced countries are making efforts to develop an environment-friendly vehicle engine at the nation-wide level in order to respond to the reinforced emission control. As a core combustion technology among new combustion technologies for the next generation engine, the homogenous charge compression ignition(HCCI) is expanding its application range by adopting multiple combustion mode, catalyst, direct fuel injection and partially premixed combustion. This study used a 2-staged injection method in order to apply the HCCI combustion method without significantly altering engine specifications in the aspect of multiple combustion mode and practicality by referring to the results of studies on the HCCI engine. In addition, this study confirmed the possibility of securing optimum fuel economy emission reduction in the IMEP 8bar range(which could not be achieved with existing partially premixed combustion) through forced charging, exhaust gas recirculation(EGR), compression ratio change and application of DOC catalyst.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.319-327
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• 1988

A new measuring method is proposed, which measures the atomization characteristics of a non-evaporating, axi-symmetric diesel spray by means of an image analysis of high speed shadow photographs. The instantaneous sauter mean diameter and the fuel concentration in the spray are calculated of the splay axis and in the radial direction and the data of the fuel injection rate, using an onion peeling model. Some examples of application of this method to eight different diesel sprays are demonstrated, and the results are compared to predicted results by the conventional immersion method and a quasi-steady one dimensional spray model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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• pp.454-460
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• 2009

To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Then the effects of change in density of ambient gas on spray structure in high temperature and pressure field have been investigated in this study. The ambient gas density was changed from ${\rho}_a=5.0kg/m^3$ to ${\rho}_a=12.3kg/m^3$ with CVC(Constant Volume Chamber). Also, simulation study by modified KIVA-II code was conducted and compared with experimental results. The ambient temperature and injection pressure are kept as 700K and 72MPa, respectively. The images of liquid and vapor phase in the evaporating free spray were simultaneously taken by exciplex fluorescence method. As experimental results, with increasing ambient gas density, the tip penetration of the evaporating free spray decreases due to the increase in the drag force from ambient gas. The spatial structure of a diesel spray can be verified as 2-regions consisted of liquid with momentum decrease and vapor with large-scale vortex. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.26-31
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• 2011

In this study, it made to run conventional single direct injection(DI) diesel engine, which adapted bulk combustion system not following spark ignition system without any ignition apparatus. It was heated and controlled inlet-air into conventional single DI diesel engine. The maximum value of brake thermal efficiency was at 35 region of air-fuel ratio. On the contrary, when the region of air-fuel ratio leaner than 35, brake thermal efficiency was decreased suddenly. And brake thermal efficiency was increased as much as inlet-air heating temperature increased. So, when air-fuel ratio was decreased and inlet-air heating temperature was higher, the engine was in optimal operation condition.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.4
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• pp.306-318
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• 2017

Heavy diesel vehicles are one of major sources of urban fine dust in Korea and other developing countries. In this study, an auxiliary device assisting fuel atomization, which is called FAD (Fuel Activation Device), was closely reviewed through numerical simulation. As calculated, the diesel flow velocity passing across FAD increased up to 1.68 times, and it enhanced the cavitation effect which could improve the injected fuel atomization. Super cavitation phenomenon, which is the most important effect on nozzle injection, has occurred until the cavitation number (${\sigma}$) decreased from 1.15 to 1.09, and atomized droplets via a nozzle of which opening was $500{\mu}m$ distributed less than $200{\mu}m$ in sauter mean diameter (SMD).