• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.123-133
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• 1995

An injection control valve(ICV) was designed to control the fuel flow between a common rail and an injector with two commercial solenoids. To improve the performance of ICV, the characteristic method was applied. With this method, the flow characteristics in the ICV and the injector were studied and the parameters which affect the injection characteristics were also studied. From this study, following results were obtained. The injection duration can be controlled and with modifications of the effective valve stroke of ICV, the injection quantity and duration can be reduced to desired amount. Also the injection quantity and pressure can be controlled by reducing the hole size of the injector without the variation of the injection duration. For some conditions, the desired injection characteristics can be obtained by the changes of the valve timing, the effective valve stroke, the open pressure of the injector and the hole size of the injector.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.357-369
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• 2003

Electromagnetic valve (EMV) actuation system is a new technology for improving fuel efficiency and at the same time reducing omissions in internal combustion engines. It can provide more flexibility in valve event control compared with conventional variable valve actuation devices. The electromagnetic valve actuator must be designed by taking the operating conditions and engine geometry limits of the internal combustion engine into account. To help develop a simple design method, this paper presents a procedure for determine the basic design parameters and dimensions of the actuator from the relations of the valve dynamics, electromagnetic circuit and thermal loading condition based on the lumped method. To verify the accuracy of the lumped method analysis, experimental study is also carried out on a prototype actuator. It is found that there is a relatively good agreement between the experimental data and the results of the proposed design procedure. Through the whole speed range, the actuator maintains proper performances in valve timing and event control.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.348-355
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• 2007

To grasp a feasibility of back fire control by valve overlap period, back fire limit equivalence ratio was estimated with valve overlap period which has the same supply energy and positive intake pressure as valve overlap period $300^{\circ}\;CA$. As the result, it was shown that the smaller valve overlap period has the higher back fire limit equivalence ratio under valve overlap period $300^{\circ}\;CA$ as well as VOP $0^{\circ}\;CA$. This result means that expansion of back fire equivalence ratio by decreasing valve overlap period was caused by decrease of back flow duration of flame from in-cylinder to intake port than decrease of lower supply energy.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.42-49
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• 2006

In this research. the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engines to the high expansion diesel cycle, and general cycle features were analyzed after comparing these two cycles. Based on these analyses. an experimental single cylinder a long stroke with high expansion-diesel engine. of which S/B ratio was more than 3, was manufactured. After evaluating the base engine through basic experiments, a diesel engine was converted into the high expansion diesel engine by establish VCR device and VVT system Accordingly, the high expansion diesel cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case, heat efficiency increased by $5.0\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle, heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged pressure equipment. Then a high expansion diesel cycle engine is realized.

• International Journal of Automotive Technology
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• v.2 no.1
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• pp.1-7
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• 2001

This paper presents further investigation into the effect of over-expansion cycle in a spark-ignition engine. On the basis of the results obtained in previous studies, several combinations of late-closing (LC) of intake valve and expansion ratio were tested using a single-cylinder production engine. A large volume of intake capacity was inserted into the intake manifold to simulate multi-cylinder engines. With the large capacity volume, LC can decrease the pumping loss and then increase the mechanical efficiency. Increasing the expansion ratio from 11 to 23.9 with LC application can produce about 13% improvement of thermal efficiency which was suggested to be caused by the increased cycle efficiency. The decrease of compression ratio from 11 to 5.5 gives little effect on the thermal efficiency if the expansion ratio could be kept constant. Thus, the expansion ratio is revealed to be a determining factor for cycle efficiency, while compression ratio is no more important, which suggests the usefulness of controlling the intake charge with intake valve closure timing. These were successfully explained by simple thermodynamic calculation and thus the mechanism could be verified by the estimation.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.39-45
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• 2006

Fundamental informations on performance of sets of solenoid valve and nozzle were necessary to develop a target selectable spraying system. The experiments were performed for the sets of solenoid valves and flat spraying nozzles at 3 levels of the operating pressures, and the obtained results are as follows; Rise time of the system pressure to reach up to 90% of the operating pressure after the valve turned was affected by nozzle size and operating pressure. Maximum overshoot of the system pressure was about 170% not affected by the sets of valve and nozzle and operating pressure. The system pressure after its settle down within 5% of the set pressure showed good uniformity in any condition of the experiment as less as 2.3% of its coefficient of variation. Time requirement to lower the system pressure down to 50% after the valve power turned off was affected by valve and nozzle set and operating pressure.

• Journal of Energy Engineering
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• v.25 no.2
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• pp.29-36
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• 2016

In this study, diesel/natural gas dual-fuel engine was studied numerically using DoE method. The engine is CI engine for power generation and modelled by 1-D simulation GT-power. The combustion and emission characteristics were analyzed as a function of IVO, IVC and the ratio of natural gas to total fuel enegy. As the proportion of natural gas increases, the BSFC(Brake specific fuel consumption) is increased and BSNOx(Brake specific NOx) is decreased. If specific valve timing to improve the BSFC is applied to the engine, the BSFC is decreased by 1% and simultaneously BSNOx is decreased by 36%.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.4
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• pp.79-89
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• 1992

The behavior of belt tension in OHC drive timing belt system was investigated analytically and experimentally for (1)fixed and (2)automatic tensioner. From the numerical results it was found that the automatic tensioner makes the belt tension larger than those of the fixed tensioner. When the initial belt tension decreased due to the belt elongation, the belt tension of the fixed tensioner could decrease to near zero while the belt tension for the automatic tensioner maintained above zero by the tensioner spring. The mean valve and the difference between the maximum and the minimum belt tension for the automatic tensioner increased compared with those of the fixed tensioner. Also, the numerical results for a hydraulic tensioner showed that the hydraulic tensioner has the good parts of both tensioners; i.e., thesmaller amplitude in belt tension and the higher mean tension. Experimental results for the automatic and fixed tensioner of the OHC timing belt system were in agreement with the theoretical results.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.101-108
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• 2011

On cold start operation of an SI engine, a catalyst shows poor performance before it reaches activation temperature. Therefore, fast warmup of the catalyst is very crucial to reduce harmful emissions. In this study, an appropriate control strategy is investigated to increase exhaust gas temperature through changes of spark timing. Combustion stability is also considered at the same time. Exhaust gas temperature and pressure of combustion chamber are measured to investigate the effects of spark timings on cold start and idle performance. Experiments showed that retarded spark timing promotes the combustion at the end of expansion stroke and increases exhaust gas temperature during cold start.

• Journal of ILASS-Korea
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• v.18 no.2
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• pp.100-105
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• 2013

While variable valve actuation or variable valve lift (VVL) is used increasingly in spark ignition (SI) engines to improve the volumetric efficiency or to reduce the pumping losses, it is necessary to understand the impact of variable valve lift and timing on the in-cylinder gas motions and mixing processes. In this paper, characteristics of the in-cylinder flow and fuel distribution for various valve lifts (4, 6, 8, 10 mm) were simulated in a GDI engine. It is expected that the investigation will be helpful in understanding and improving GDI combustion when a VVL system is used. The CFD results showed that a increased valve lift could significantly enhance the mixture and in-cylinder tumble motion because of the accelerated air flow. Also, it can be found that the fuel distribution is more affected by earlier injection (during intake process) than that of later injection (end of compression). These may contribute to an improvement in the air-fuel mixing but also to an optimization of intake and exhaust system.