• Journal of ILASS-Korea
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• v.27 no.2
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• pp.101-108
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• 2022

Performance and emissions with different diesel injection methods were analyzed in a natural gas-diesel, dual-fuel engine under low-load conditions. Natural gas was supplied to intake port during the intake stoke to form a natural gas-air premixed mixture for all methods. Diesel was injected directly into the cylinder during the compression stroke in three ways: early injections, late injections, and a combination of early and late injections. The early injections had the highest thermal efficiency among the three methods owing to its highest combustion efficiency. The wide dispersion of diesel before the combustion initiation also allowed superior emissions characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.5
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• pp.661-671
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• 1998

It is unavoidable that the fuel spray impinges on the wall of piston cavity in a compact high-pressure D.I. diesel engine. Therefore the characteristics of impinging spray are the very significant information on the consideration and the simulation of its combustion processes including the formation mechanism of exhaust emission and the design of the combustion chamber. In this paper, the numerical simulation was performed to study the characteristics of impinging spray. The spray-wall impingement model used is Watkins and Park's model. Calculation parameters are the inclination angles and the ambient pressures. As the inclination angle increases, the impinging spray develops mainly to the direction of the downstream and scarcely flows to that of the upstream. The shape on the wall of the impinging spray is the circle in the case of the normal impingement, while it is the ellipse in that of the oblique impingement. As the ambient pressure increases, the growth of impinging spray on the wall in the radial direction decreases owing to the increase in the resistance of the ambient.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.727-736
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• 2016

Numerical simulations of n-heptane spray characteristics in a constant volume combustion chamber under diesel engine like conditions with increasing ambient gas density ($14.8-142kg/m^3$) and ambient temperature (800-1000 K) respectively were performed to understand the non-vaporizing and vaporizing spray behavior. The effect of fuel temperature (ranging 273-313 K) on spray characteristics was also simulated. In this simulation, spray modeling was implemented into ANSYS FORTE where the initial spray conditions at the nozzle exit and droplet breakups were determined through nozzle flow model and Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) model. Simulation results were compared with experimentally obtained spray tip penetration result to examine the accuracy. In case of non-vaporizing condition, simulation results show that with an increment of the magnitude of ambient gas density and pressure, the vapor penetration length, liquid penetration length and droplet mass decreases. On the other hand vapor penetration, liquid penetration and droplet mass increases with the increase of ambient temperature at the vaporizing condition. In case of lower injection pressure, vapor tip penetration and droplet mass are increased with a reduction in fuel temperature under the low ambient temperature and pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.16-23
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• 2001

Spray dispersion in high pressure diesel engines have been simulated experimentally with a special emphasis on the effect of swirl by using a liquid injection technique. A constant volume chamber was designed to be rotatable in order to generate a continuous swirl and to have the flow field closely resembling a solid body rotation. Emulsified fuel was injected into the chamber and the developing process of fuel sprays was visualized. The effect of swirl on the spray dispersion was quantified by calculating non-dimensionalized dispersion area according to the spray tip penetration length. The results show that the effect of swirl on the spray dispersion is different between short and long spray penetrations. For short range of spray tip penetration, the effect of swirl on spray dispersion is quite small. However, as the spray tip is penetrated into longer distance in spray chamber, the effect of swirl on spray dispersion becomes larger. These results can be used as a basic data for designing combustion chamber and injection system of direct injection diesel engine.

• Journal of the Korean Institute of Gas
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• v.20 no.4
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• pp.44-49
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• 2016

This paper presents characteristics of diesel combustion and emissions according to adoption of various combustion chamber geometry. In order to suggest suitable combustion chamber geometry of the common rail diesel engine for electric generative use, 5 type of geometry chamber was found performance for combustion chamber to respond fuel efficiency. Combustion chamber geometry affects combustion characteristics due to change target area of spray in the combustion chamber and the main factor was the bowl aspect ratio of combustion chamber. Using the results of simulation, the effects of the variable combustion chamber can be improved the fuel efficiency for electric generation.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.5
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• pp.26-35
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• 1990

This is an experimental study to investigate the characteristics of Diesel spray and Diesel engine performance using ultrasonic injection nozzle (A, B type) and conventional commercial injection nozzle (C type). The results are obtained as follows: 1. SMD and range of size distribution of Diesel spray using the ultrasonic nozzle are smaller than those using the conventional injection nozzle, and spray angle is spread. 2. Because of the difference of the ultrasonic vibration energy transfer in the same condition, the effects of A-type ultrasonic vibration are larger than those of B-type ultrasonic vibration. 3. Attaching the ultrasonic vibrator to the conventional injection nozzle of the Diesel engine, engine performances i.e. BMEP, BSFC, and cylinder peak pressure are improved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.60-67
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• 2000

An experimental investigation on transient heat transfer phenomena of impinging diesel-spray on a flat plate in a pressurized chamber is carried out. A diesel spray is injected from a single-hole nozzle and impinges to a heated flat plate in the chamber. A fast-response thermocouple installed in the top surface of the plate measures the transient variation of surface temperature of the plate under various conditions of the chamber pressures. Utilizing the semi-infinite model, the temporal variation of the heat flux on the plate is determined. Effects of various parameters, such as vertical distances between the nozzle and the plate, radial distances from the injection-axis, and the chamber pressures, on the heat flux characteristics of impinging diesel-spray are studied.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.16-22
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• 2004

Dimethyl Ether (DME) has been considered as one of the most attractive alternative fuels for a compression ignition engine. The major advantage of DME-fuelled engine is a great potential for soot-free combustion without sacrificing an inherent high thermal efficiency of diesel engine, despite a necessity for modification of the conventional fuel injection system. An experimental study on DME and conventional diesel sprays was conducted by employing a common-rail type fuel injection system with a 5-holes sac type nozzle, including a constant volume vessel pressurized with nitrogen gas. The injection rates of DME and diesel fuel were recorded with the Bosch type injection rate meter. The injection delay of DME was shorter than that of diesel fuel. The measured injection rates of DME and diesel fuel were correlated with spray penetrations. The prediction method of spray penetration was established using the injection rates, which was verified with the Dent's penetration model and found to agree well for DME case.

• Journal of the Korean Society of Combustion
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• v.17 no.2
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• pp.24-31
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• 2012

Diesel engines exhaust much more NOx(Nitrogen Oxides) and PM(Particulate Matter) than gasoline engines, and it is not easy to reduce both NOx and PM simultaneously because of the trade-off relation between two components. This study investigated flame characteristics of the partial premixed compression ignition known as new combustion method which can reduce NOx and PM simultaneously. The investigation was performed through the analysis of the flame images taken by a high speed camera from the visible engine which is the modified single cylinder diesel engine. The results obtained through this investigation are summarized as follows; (1) The area of the luminous yellow flame was reduced due to the decrease of flame temperature and even distribution of temperature. (2) The darkish yellow flame zone caused by the shortage of the remaining oxygen after the middle stage of combustion was considerably reduced. (3) Since the ignition delay was shortened, the violent combustion did not occur and the combustion duration became shortened.

• Journal of ILASS-Korea
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• v.16 no.1
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• pp.51-57
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• 2011

An experimental study was performed to explore characteristics of combustion and exhaust emissions in the compression ignition engine of RCCI (reactivity controlled compression ignition) using diesel-gasoline dual fuel. A dual-fuel reactivity controlled compression ignition concepts is demonstrated as a promising method to achieve high thermal efficiency and low emissions. For investigating combustion characteristics, engine experiments were performed in a light-duty diesel engine over a range of SOIs (start of injection) and gasoline percents. The experimental results showed that cases of diesel-gasoline dual fuel combustion is capable of operating over a middle range of engine loads with lower levels of NOx and soot, acceptable pressure rise rate, low ISFC (indicated specific fuel consumption), and high indicated thermal efficiency.