• 한국연소학회지
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• 제12권2호
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• pp.20-25
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• 2007

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Hydrogen Fuel is injected in the cavity parallel with air(or nitrogen) flow. The equivalence ratios in this study are 0.132 and 0.447. Experimental measurements use OH-PLIF near the cavity and pressures in the combustor. For parallel fuel injection case, direct fuel add into cavity leads to increase of cavity pressure. And Flame exists just near the bottom wall for low equivalent ratio. There is no flame in the cavity because of no mixing in it. Compared to the inclined fuel injection, ignition delay length is longer for low equivalence ratio in both case. OH distribution is not a single line but a repeatable fluctuation flame structure by turbulence. Pressure distributions have nothing to do with the fuel injection position.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.31-36
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• 2007

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Hydrogen Fuel is injected in the cavity parallel with air(or nitrogen fuel) flow. The equivalence ratios in this study are 0.132 and 0.447. Experimental measurements use OH-PLIF near the cavity and pressures in the combustor. For parallel fuel injection case, direct fuel add into cavity leads to increase of cavity pressure. And Flame exists just near the bottom wall for low equivalent ratio. There is no flame in the cavity because of no mixing in it. Compared to the inclined fuel injection, ignition delay length is longer for low equivalence ratio in both case. OH distribution is not a single line but a repeatable fluctuation flame structure by turbulence. Pressure distributions have nothing to do with the fuel injection position.

• 대한기계학회논문집B
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• 제24권6호
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• pp.870-879
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• 2000

An experimental investigation is conducted to improve a slot film cooling system which can be used for the cooling of gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical, and combined to the slot lip. The investigation is focused on the coolant supply systems of normal-, parallel-, and counter-flow paths to the mainstream direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot with various injection types and coolant feeding directions. The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The secondary flow at the lip exit has uniform velocity distributions for the parallel and vertical injection types, which are similar to the results of a two-dimensional slot injection. In the results of local heat/mass transfer coefficient, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effect of jet impingement. The lateral distributions of Sh with the parallel- and counter-flow paths are more uniform than the normal flow path. The averaged Sh with the injection holes are $2{\sim}5$ times higher than that of a smooth two-dimensional slot path.

• 한국멀티미디어학회논문지
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• 제22권11호
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• pp.1223-1232
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• 2019

The injection is the input method of the image feature vector from the encoder to the decoder. Since the image feature vector contains object details such as color and texture, it is essential to generate image captions. However, the bidirectional decoder model using the existing injection method only inputs the image feature vector in the first step, so image feature vectors of the backward sequence are vanishing. This problem makes it difficult to describe the context in detail. Therefore, in this paper, we propose the parallel injection method to improve the description performance of image captions. The proposed Injection method fuses all embeddings and image vectors to preserve the context. Also, We optimize our image caption model with Bidirectional Gated Recurrent Unit (Bi-GRU) to reduce the amount of computation of the decoder. To validate the proposed model, experiments were conducted with a certified image caption dataset, demonstrating excellence in comparison with the latest models using BLEU and METEOR scores. The proposed model improved the BLEU score up to 20.2 points and the METEOR score up to 3.65 points compared to the existing caption model.

• 설비공학논문집
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• 제12권9호
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• pp.802-809
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• 2000

This study numerically analyzes the thermal and flow characteristics inside the header in PFHE(parallel-flow heat exchanger) by employing a three-dimensional turbulence modeling. The following quantities are examined by varying the injection angle of the working fluid, the location of entrance and the shape of entrance: flow nonuniformity, heat transfer rate, and flow distribution in each passage. The result shows that the degree of significance among the parameters affecting the header part is in the order of the injection angle, the shape of entrance, and the location of entrance. The result also indicates that heat transfer rates compared to the reference model are increased by about 152% for the angle of injection of -$20^{\circ}C$, by about 127% for the shape of entrance with right and left long rectangular form, and by about 108% for the location of entrance located at the lowest Position.

• 한국전산유체공학회지
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• 제17권3호
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• pp.93-98
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• 2012

The injection molding process is suitable for manufacturing complicated plastic products. As the customer request higher quality products increase, realization of the precise dimensional and shape controls is getting more important. For this purpose it is important to obtain uniform cooling procedure over the whole surface of the high temperature molded plastic. Failure to this may lead to different shrinkage speed, internal stresses and unwanted shape deformations. It is necessary to distribute coolant flow rates to the main channel and to the sub-channels properly to insure uniform cooling process when there are parallel cooling channels. In this study, three-dimensional turbulent flow simulations for representative parallel cooling channels were performed. To insure the intended flow rate to each sub-channels, various shape designs for the channel system were investigated. The results show that as the Reynolds number increases the effect of shape design is more profound. Through the proper flow distribution, uniform cooling effects would be expected.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.950-958
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• 2002

The combustion characteristics of a low NOx burner using reburning technology have been experimentally studied. The return burner usually has three distinct reaction zones which include the primary combustion zone, the reburn zone and the burnout zone by provided secondary air. NOx is mainly produced in a primary combustion zone and a certain portion of NOx can be converted to nitrogen in the rebury zone. In the burnout zone, the unburned mixtures are completely oxidated by supplying secondary air. Liquefied Petroleum Gas (LPG) was used as main and reburn fuels. The experimental parameters investigated involve the main/reburn fuel ratio, the primary/secondary air ratio, and the injection location of rebury fuel and secondary air. When the amount of return fuel reaches to the 20-30% of the total fuel used, the overall NO reduction of 50% is achieved. The secondary air is injected by two different ways including vertical and parallel injection. The injector of secondary air is located at the downstream region of furnace for a vertical-injection mode, which is also placed at the inlet primary-air injection region for a parallel-injection mode. In case of the vertical injection of the secondary air flow, the NOx formation of stoichiometric condition at a primary combustion zone is nearly independent of the rebury conditions (locations, fuel/air ratios) while the NOx emission of the fuel-lean condition is considerably influenced by the reburn conditions. In case of the parallel injection of the secondary air, the NOx emission is sensitive to the air ratio rather than the fuel ratio and the reburning process often coupled with the multiple air-staging and fuel-staging combustion processes.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.293-296
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• 2007

호주국립대학의 T3 자유충격파관을 이용하여, 마하수 3.7의 유입 유동에 대해 비분사유동, 공동이전 경사분사유동, 공동내부 평행분사유동, 공동내부 역분사유동에 대해 주파수를 확인하고, 공동 유동 특성을 살펴보았다. 비분사유동은 고조파 형태의 주파수가 나타나지 않았으나 10 kHz 부근에서 비교적 큰 압력 스펙트럼이 나타났다. 공동 이전 경사분사는 공동의 앞전에서 박리되는 전단층의 두께를 증가시켜 공동 뒷전에서 발생하는 유동의 진동 현상을 현저히 감소시켰다. 공동 내부 평행분사는 공동의 뒷전에 분사 유동이 직접 부딪히게 되고, 공동의 진동 현상을 오히려 증가시켰다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.216-226
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• 2015

The neutral beam injection generate ultra-high temperature energy in the tokamak of nuclear fusion. The neutral beam injection make up arc power supply, filament power supply and acceleration & deceleration power supply. The arc power supply has characteristics of low voltage and high current. Arc power supply generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The proposed buck converter used parallel switch because it can be increased capacity and decrease conduction loss. When an arc generated, the neutral beam injection chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus the proposed converter should be designed for the characteristics of low voltage and high current. Also, the arc power supply should be guaranteed for system stability. The proposed parallel buck converter enables the system stability of the divided low output voltage and high current. The proposed converter with constant output be the most important design of the output inductor. In this paper, designed arc power supply verified operation of system and stability through simulation and prototype. After it is applied to the 288[kW] arc power supply for neutral beam injection.

• Design & Manufacturing
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• 제2권4호
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• pp.54-61
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• 2008

Warpage, which is one of the molding trouble, acts as possible factor which results in defect in assembly. In this study, a mold was designed to produce specimens with rib parallel to flow direction, specimens with rib perpendicular to flow direction and specimens without rib. This work researched change of warpage according to injection molding condition such as injection pressure, packing pressure, packing time, resin temperature, mold temperature in non-crystalline resins(PC, ABS), crystalline resins(PP, PA66), and 30% glass fiber reinforced-resins(PC, ABS, PP, PA66).Specimens with rib and Crystalline resins show more warpage than specimens without rib and non-crystalline resins, respectively. Glass fiber reinforced-resins and specimens with rib parallel to flow direction show smaller warpage than conventional resins and specimens with rib perpendicular to flow, respectively. Specimens with rib and specimens without rib show reduced warpage as packing time increases. In addition, warpage increase as resin temperature increases. It is found that CAE shows similar tendency with experiment as packing time, resin temperature. when the rib is caused, warpage will reduce and prevent the transformation. product of a irregular form occurs warpage. In the study It'll be basic data that product occurs warpage, preferablity.