• 대한기계학회논문집B
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• 제35권10호
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• pp.981-987
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• 2011

단기통 직접분사 가솔린엔진의 성층연소 조건에서 연소실험을 수행하였다. 각 분사압조건마다 실화가 발생하지 않는 성층연소가능 분사시기영역이 존재하였으며 이는 혼합기 형성과정의 분위기압에 따른 영향으로 판단하였다. 연소효율은 분사시기를 지각할수록 증가하며 32~28 CAD BTDC에서 최대값을 갖고 이후 감소하는 경향을 보였고 분사압이 높을수록 높은 연소효율이 나타났다. 이러한 연소효율의 경향은 IMEP와 다른 경향을 보였으며 그 이유는 높은 연소효율 조건에서 연소상이 진각되어 음의 일이 증가하였기 때문으로 판단된다. Smoke의 배출은 분사시기가 지각됨에 따라 증가하였으며 높은 분위기 압에서 국부적으로 농후한 영역이 증가하였기 때문으로 생각된다. NOx 배출도 분사시기를 지각함에 따라 감소하였으며 연소상의 지각으로 최대 연소실압력과 온도가 감소하였기 때문으로 생각된다.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.89-95
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• 2013

In this work, the evaluation of swirl nozzle injector performance was conducted by investigating effective area ($A_{eff}$), injection mass ($m_{inj}$), injection rate ($Q_{inj}$), and injection delay ($t_{delay}$) under various test conditions. To achieve these, fuel injection analysis system which was composed of fuel supply system, injection system, and control system was installed. At the same time, the swirl nozzle that had 12 orifice hole with $120^{\circ}$ injection angle was used in this work. It was revealed that the difference of injection mass ($m_{inj}$) between base and swirl nozzle injector increased as the injection pressure ($P_{inj}$) and energizing duration ($t_{eng}$) decreased under the same test conditions. The maximum injection rate ($Q_{inj}$) of swirl nozzle injector was higher than base nozzle injector about 2~5%. The injection performance of swirl nozzle was better than base nozzle at low injection pressure ($P_{inj}$) and short energizing duration ($t_{eng}$) conditions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.287-293
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• 2004

A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, an 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two $D_2$injector pressure cases; 192 torr and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the $D_2$injection pressure is lower. But, the higher $D_2$injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of $D_2$injector increases, the maximum small signal gain in the $V_{1-0}$ transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.r.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.59-66
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• 2001

This experimental study is to investigate the flow characteristics of the multi-hole nozzle used in the fuel injection system of a heavy-duty diesel engine. A multi-hole diesel nozzle with a 2-spring nozzle holder was used in this study and without changing the total orifice exit area, its hole number varied from 3($d_n$=0.42mm) to 8($d_n$=0.25mm). The injection pressure and needle lift were measured and Bosch type injection rates measurement system was used. The discharge flowrates of each orifice in the multi-hole nozzle changed by the flow conditions inside the nozzle sac hole. In case that pump speed and injection quantity were low, the orifice located in the vertex of nozzle tip had a great deal of injection quantity compared with that of others. As the increment of multi-hole number, the injection duration and the mean injection pressure decrease. The mean and peak injection rates, however, increase. Actually, the mean flow coefficient(${C_d}_{(mean)}$) increases, too. The flow coefficient of the multi 8 hole was evaluated as Cd(mean)=0.74 and that is the maximum value among the examined conditions.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.37-57
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• 2016

Reservoir geomechanics can play an important role in hydrocarbon recovery mechanism. In $CO_2$-EOR process, reservoir geomechanics analysis is concerned with the simultaneous study of fluid flow and the mechanical response of the reservoir under $CO_2$ injection. Accurate prediction of geomechanical effects during $CO_2$ injection will assist in modeling the Carbon dioxide recovery process and making a better design of process and production equipment. This paper deals with the implementation of a program (FORTRAN 90 interface code), which was developed to couple conventional reservoir (ECLIPSE) and geomechanical (ABAQUS) simulators, using a partial coupling algorithm. A geomechanics reservoir partially coupled approach is presented that allows to iteratively take the impact of geomechanics into account in the fluid flow calculations and therefore performs a better prediction of the process. The proposed approach is illustrated on a realistic field case. The reservoir geomechanics coupled models show that in the case of lower maximum bottom hole injection pressure, the cumulative oil production is more than other scenarios. Moreover at the high injection pressures, the production rates will not change with the injection bottom hole pressure variations. Also the FEM analysis of the reservoir showed that at $CO_2$ injection pressure of 11000 Psi the plastic strain has been occurred in the some parts of the reservoir and the related stress path show a critical behavior.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권4호
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• pp.141-148
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• 2009

Afterfogging of the regenerative gas turbine system has an advantage over inlet fogging in that the high outlet temperature of air compressor makes the injection of more water and the recuperation of more exhaust heat possible. This study investigates the effects of turbine inlet temperature (TIT) on the performance of regenerative gas turbine system with afterfogging through a thermodynamic analysis model. For the standard ambient conditions and the water injection ratios up to 5%, the variation of system performance including the thermal efficiency is numerically analyzed with respect to the variations of TIT and pressure ratio. It is also analyzed how the maximum thermal efficiency, net specific work, and pressure ratio itself change with TIT at the peak points of thermal efficiency curve. All of these are found to increase almost linearly with the increases of both TIT and water injection ratio.

• 한국수산과학회지
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• 제8권3호
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• pp.150-156
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• 1975

Diesel 기관의 연소는 매우 복잡한 현상이다. 이 복잡한 연소과정을 각운전조건하에서 구한 열발생율에 의해 해석했으며 그 결과 다음 사항이 밝혀졌다. 1. Diesel기관의 연소기간은 예혼합기연소기관과 황산연소기관으로 나누어 생각할 수 있다. 2. 예혼합기연소부분이 클수록 효율은 양호하나 최고압력이 높아져 정숙한 운전이 되지 못하고 확산연소기간이 길수록 운전은 정숙하나 효율은 떨어지고 배기온도는 상승한다. 3. 예혼합기 연소부분은 주로 발화지연에 지배되나 확산연소기간은 산소의 확산에 지배된다. 4. 실험범위내에서 기관의 효율은 분사량과 회전수가 일정하면 분사시기가 빠를수록 효율은 증가했으나 압력의 상승은 효율의 증가보다 높았다.

• 한국산학기술학회논문지
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• 제15권5호
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• pp.2573-2578
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• 2014

본 연구는 4실린더 커먼레일 디젤 기관에서 바이오 디젤 혼합 연료를 사용하여 예비 분사시기와 EGR율을 변화시켰을 때 연소 압력과 배기 특성에 미치는 영향을 조사하기 위하여 실험을 수행하였다. 예비 분사 시기와 EGR율은 디젤 기관의 연소 및 배기 배출 특성에 큰 영향을 미친다. 본 연구에서는 일반적으로 많이 사용되고 있는 기관 회전 속도 2,000rpm에서 바이오 디젤 혼합율 20%의 연료를 사용하여 예비 분사 시기와 EGR율에 다양하게 변화를 주어 실험을 하였다. 실험결과, 도시 평균 유효 압력은 예비 분사 시기가 상사점전 BTDC $10^{\circ}$에서 가장 높았으며, 연소 압력과 열 발생율은 동일 예비 분사 시기에서 EGR율에 비례하여 감소하였다. NOx배 출량은 예비 분사시기에 관계없이 EGR율이 증가할수록 큰 폭으로 감소하였으며, 매연(Soot)은 예비 분사 시기 BTDC $20^{\circ}$에서 가장 적게 배출되었다.

• Design & Manufacturing
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• 제14권1호
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• pp.1-7
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• 2020

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

• 한국분무공학회지
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• 제13권3호
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• pp.117-125
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• 2008

The correlations for the prediction of maximum liquid-phase penetration in diesel spray are reviewed in this study. The existing models developed for the prediction of maximum liquid-phase penetration can be categorized as the zero-dimensional (empirical) model, the multi-dimensional model and the other model. The existing zero-dimensional model can be classified into four groups and the existing multidimensional models can be classified into three groups. The other model includes holistic hydraulic and spray model. The maximum liquid-phase penetration is mainly affected by nozzle diameter, fuel volatility, injection pressure, ambient gas pressure, ambient gas density and fuel temperature. In the case of empirical correlations incorporated with spray angle, the predicted results will be different according to the selection of correlation for spray angle. The research for the effect of boiling point temperatures on maximum liquid-phase penetration is required. In the case of multidimensional model, there exist problems of the grid and spray sub-models dependency effects.