• 한국분무공학회지
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• 제21권1호
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• pp.47-52
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• 2016

This paper describes the modeling of CNG direct injection using gaseous sphere injection model. Simulation of CNG direct injection does not need break up and evaporation model compared to that of liquid fuel injection. And very fine mesh is needed near the injector nozzle to resolve the inflow boundary. Therefore it takes long computation time for gaseous fuel injection simulation. However, simulation of CNG direct injection could be performed with the coarse mesh using gaseous sphere injection model. This model was integrated in KIVA-3V code and RNG $k-{\varepsilon}$ turbulence model needs to be modified because this model tends to over-predict gas jet diffusion. Furthermore, we preformed experiments of gaseous fuel injection using PLIF (planar laser induced fluorescence)method. Gaseous fuel injection model was validated against experiment data. The simulation results agreed well with the experiment results. Therefore gaseous sphere injection model has the reliability about gaseous fuel direct injection. And this model was predicted well a general tendency of gaseous fuel injection.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.50-59
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• 2003

It was known that high pressure injection is an effective method to enhance thermal efficiency and decrease exhaust emissions in diesel engines. If injection pressure becomes ultra high, it is predicted that there may be a suitable injection pressure which the enhancement rate of spray characteristics is moderate. Also, there may be a limit injection pressure which spray characteristics is reversed and get worse. But these are unknown. To investigate a suitable injection pressure and a limit injection pressure, ultra high pressure injection equipment(UHPIE), which can realize the injection pressure of 3,200bar, was developed. UHPIE is a basic apparatus of single shot injection, and ultra high pressure was achieved by second stage rapid compression in short time. From the evaluation of UHPIE, a injection curve like a conventional diesel engine(jerk type) was realized. Also, it was proved that repetition of experiment was excellent. Therefore it was found that there was no problem to perform the study on the ultra high pressure injection with UHPIE. Consequently, the foundation of the study on ultra high pressure injection could be established.

• 한국생산제조학회지
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• 제6권1호
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• pp.84-91
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• 1997

In producing moldings by using an injection mold, several variables such as the metal mold and the condition of injection molding should be selected properly in order to obtain good quality of moldings. In this study, focussed are the mechanical properties of injection moldings, since many researches on injection have been focussed mainly on the molding quality, injection pressure, and bulk temperature but the properties of injection moldings have not been studied extensively. The mechanical properties of present injection moldings can be improved simply by changing the molding material and the injection conditon without changind the metal mold. To have the final products meet the specified molding quality and mechanical properties at the same time, the bulk temperature of injection, pressure variation, volumetric shrinkage, stress, and cooling should be analized by CAE(computer aided engineering) after injection mold design. In this paper, the effects of dischare condition on mechanical properties of injection moldings are studied by testing the moldings which are injected by varying injection conditions.

• 한국분무공학회지
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• 제24권4호
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• pp.171-177
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• 2019

This paper describes numerical study of combustion characteristics in CNG(compressed natural gas) DI(direct injection) engine using gaseous sphere injection model. Simulations were conducted using KIVA-3V Release 2 code. Gaseous sphere injection model, which is modified model of liquid fuel injection, was used to simulate the CNG direct injection. Until now, a very fine mesh smaller than the injector nozzle has been required to resolve the gas-jet inflow boundary. However, the gaseous sphere injection model simulates gaseous fuel injection using a coarse mesh. This model injects gaseous spheres as in liquid fuel injection and the gaseous spheres evaporate together without the latent heat of evaporation. Therefore, it does not require a very fine mesh and reduce calculation time. Combustion simulation were performed under various injection timings and injection pressures.

• 한국분무공학회지
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• 제12권3호
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• pp.166-171
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• 2007

Recently, many studies on HSDI diesel engines have been performed to reduce the fuel consumption and $CO_2$ emission. One of the prominent technique to reduce emission is a high pressure multiple injection. For this technique, the injection rate is a critical parameter in order to determine precise injection duration and timing for combustion control. Thus the purpose of this study was to investigate relationship between the injection rate and the time-signature of chamber pressure at different injection pressure conditions in a common rail direct injection type injector using the Zeuch method. Using the measured correlation constants, estimated fuel injection rates are presented at many different injection conditions.

• 한국분무공학회지
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• 제18권4호
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• pp.176-181
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• 2013

In this study, injection quantity, rate and spray image of multiple injections which are important design parameters for a piezo type injector have been investigated. Interval of injections and a number of injections in multiple injection strategy has been controlled to verify interaction of each injection. Spray characteristics of multiple injections have been researched through optical process with a high speed camera in a high pressure chamber. In addition, a method of RMS(Root Mean Square) process has been used for comprehending the distribution of injection easily. As a result, in case of piezo type injector, characteristics of injection quantity according to charging voltage and the difference of injection quantity between single and triple injection were confirmed. Also, injection rate for increasing injection duration was confirmed. And spray characteristics of multiple injections were improved; multiple injections were possible in a shorter time interval between each injection. With this study, a possibilities of more accurate multiple injection control would be expected.

• 설비공학논문집
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• 제21권8호
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• pp.425-432
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• 2009

In this study, the improvement of cooling capacity by applying gas injection technique in a two-stage heat pump using R410A was experimentally investigated. A twin rotary type compressor with gas injection was applied to the heat pump system. The optimum refrigerant charge for the injection and the non-injection cycles was selected to achieve the maximum COP at the cooling standard condition. The injection cycle showed less optimum refrigerant charge than that of the non-injection cycle. The cooling performances of the injection and the non-injection cycles were measured and compared by varying compressor frequency from 40 to 90 Hz. The cooling capacity of the gas injection cycle was 1.6% -11.3% higher than that of the non-injection cycle. The COP of the gas injection cycle was 13.7% to 28.9% higher than that of the non-injection cycle at the same cooling capacity. The heat pump system showed stable operation after 30% of the injection valve opening.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.619-626
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• 2002

In this study, a correlation among pressure, time and quantity of injection was organized from the laboratory tests, which were executed many times representing in-situ soil conditions carefully and then it would be applied to the in-situ soil injection simulator which will be developed for optimal injection into the ground. The sort of sample soils were both sand(A specimen) and silty sand(B specimen). Injection tests were gone into operation by compaction state, injection velocity and the depth individually. In the ground improved with permeation Infection, the relation among injection pressure of the same depth, the injected quantities and time were systematic by the depth. By defining the limit range of injection pressure and quantity about the variety of a linear equation obtained from lining each of their trend, the application of laboratory injection monitoring program and the data to evaluate its realization were produced. In the ground improved with root type injection, the relation between injection pressure and the injected quantities was irregular because fracture state occurred quickly.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.106-113
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• 2016

Lean burn engine, classified into port injection and direct injection, is recognized as a promising way to meet better fuel economy. Especially, LPG direct injection engine is becoming increasingly popular due to their potential for improved fuel economy and emissions. Also, LPDi engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. However, LPDi engine has many difficulties to be solved, such as complexity of injection control mode (fuel injection timing, injection rate), fuel injection pressure, spark timing, unburned hydrocarbon and restricted power. This study is investigated to the influence of spark timing, fuel injection position and fuel injection rate on the combustion stability of LPDi engine. Piston shape is constituted the bowl type piston. The characteristics of combustion is analyzed with the variations of spark timing, fuel injection position and fuel injection rate (early injection, late injection) in a LPDi engine.

• 한국분무공학회지
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• 제28권4호
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• pp.169-175
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• 2023

Multi-injection scheme is being applied to GDI combustion to reduce PM and PN emission to meet the EU7 regulation. However, very short injection duration encounters the ballistic injection region, which injection quantity does not increase linearly with injection duration when applying multi-injection. In this study, numerical studies were conducted to reveal the cause of ballistic injection and the effect of design parameters on ballistic region using 1-D simulation, AMESim. Injection rate and injection quantity were compared with experiment to validate the established model, which showed the accuracy with 10% error. The model revealed that the tendency of ballistic region coincides with the needle motion behavior, which means that parameters at the upper part of needle such as electro-magnetic force, needle spring force and needle friction force have dominant effect on ballistic injection. To figure out the effect of electro-magnetic and needle friction force on ballistic, those parameters were varied to plus and minus 10% with model. The result showed that those parameters clearly changed the ballistic region characteristics, however, the impact became insignificant for outside of ballistic region, which means that the ballistic injection is mainly influenced by initial motion of injector needle.