• 한국추진공학회지
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• 제25권3호
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• pp.42-55
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• 2021

본 연구에서는 중심선 방정식 선정에 따른 노즐 성능 영향성을 확인하고자 하였다. 곡선 방정식과 설계 형상 파라미터를 활용하여 S-형 노즐 3조와 Double S-형 노즐 3조를 설계하였고 노즐 차폐 성능은 차폐율 정의를 이용하여 평가하였다. 그리고 내부 유동을 분석하기 위해 속도 분포도와 압력분포도로 특성을 연구하였고, 노즐 성능 계수로는 총 추력 비(f)와 노즐 단열 효율계수(η)를 통해 노즐의 성능을 평가하였다. 중심선에 따른 S-형 노즐의 성능 영향성을 분석한 결과 출구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 우수한 반면 차폐율이 낮은 특징이 있다. 반면에 입구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 낮아지고 차폐율이 높은 특징이 있다. Double S-형 노즐은 첫 번째 곡률에서 완만한 특징을 보이는 중심선을 사용하는 것이 노즐 성능과 차폐율이 우수하였다.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.60-65
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• 2004

Numerical simulations and experiments have been carried out to investigate the effect of fuel injection nozzles on the combustion and NOx formation processes in a medium-speed marine diesel engine. Spray visualization experiment was performed in the constant-volume high-pressure chamber to verify the numerical results on the spray characteristics such as spray angle and spray tip penetration. Time-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the information on the spray parameters. Spray and combustion phenomena were examined numerically using FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Numerical results were verified with experimental data such as cylinder pressure, heat release rate and NOx emission. Finally, the effects of fuel injection nozzles on the engine performance were investigated numerically to find the optimum nozzle parameters such as fuel injection angle, nozzle hole diameter and number of nozzle holes. From this study, the optimum fuel injection nozzle (nozzle hole diameter, 0.32 mm, number of nozzle holes, 8 and fuel injection angle, $148^{\circ}$) was selected to reduce both the fuel consumption and NOx emission. The reason for this selection could be explained from the highest fuel-air mixing in the early phase of injection due to the longest spray tip penetration and the highest heat release rate after $19^{\circ}$ ATDC due to the increased injection duration.

• Journal of Mechanical Science and Technology
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• 제15권8호
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• pp.1174-1180
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• 2001

Various experimental data, including mixing areas, cross correlation factors, surface flow patterns on nozzle walls, and far field noise spectra, was used to draw a noise control mechanism in a supersonic jet. In the underexpanded case, mixing of the jet air with ambient air was significantly enhanced as presented before, and mixing noise was also dramatically reduced. Screech tones, in the overexpanded case, were effectively suppressed by trailing edge modifications, although mixing enhancement was not noticeable. From mixing and noise performance of nozzles with modified trailing edges, enhancing mixing through streamwise vortices seems an effective way to reduce mixing noise in the underexpanded flow regime. However, screech tones in the overespanded flow regime is well controlled or suppressed by making shock cells and/or spanwise large scale structures irregular and/or less organized by a proper selection of trailing edges. The noise field in the overexpanded flow regime was greatly affected by the symmetricity of the nozzle exit geometry. In the underexpanded flow regime, the effects of the symmetricity of the nozzle exit on mixing were negligible.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1361-1369
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• 2013

본 연구에서는 다공홀 인젝터 내부 유동에 대한 CFD 시뮬레이션 해석(ANSYS 13.0 CFX)을 직접 수행하였다. 이러한 결과를 바탕으로 인젝터 노즐 설계변수가 캐비테이션에 미치는 영향을 파악하기 위해 실험계획법이 적용되었다. 각 설계변수의 설계민감도 및 신호 대 잡음비 분석을 위해 캐비테이션 유동에 영향을 미친다고 판단되는 설계변수는 노즐 홀 직경, 노즐 홀 길이, 노즐 홀 각도 및 노즐 홀의 K-factor로 지정하였다. 또한 16 개 실험점으로 각 변수의 영향을 분석하였다. 본 연구에서 노즐 내부유동을 파악하기 위하여 수치해석 프로그램과 신호 대 잡음비 분석이 본 논문에 적용되었고 그 결과, K-factor의 변화가 노즐 홀 길이와 노즐 홀 각도의 변화보다 인젝터 내부 캐비테이션 생성에 미치는 영향이 더 크다는 것을 알 수 있었다.

• 한국해양공학회지
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• 제32권2호
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• pp.138-142
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• 2018

The marine industry is rapidly developing as a result of the increase in various needs in the marine environment. In addition, accidents involving ship fires and explosions and the resulting casualties are increasing. Generally, manpower and safety problems exist in fire fighting. A fire fighter in the form of an autonomous surface robot would be ideal for marine fire safety, because it has no manpower and safety problems. Therefore, an autonomous surface robot with the abilities of fire recognition and tracking, nozzle selection, position and attitude control, and fire fighting was developed and is discussed in this paper. The test and evaluation results of this robot showed the possibility of real-size applications and the need for additional studies.

• 한국기계가공학회지
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• 제12권1호
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• pp.63-69
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• 2013

Many researchers are trying to reduce the use of lubrication fluids in metal cutting to obtain safety, environmental and economical benefits. The aim of this study is to determine the optimization lubrication conditions in minimum quantity lubrication(MQL) turning of workpieces with taper angle. This study has been considered about various conditions of MQL. The objective functions are cutting force and surface roughness. Design factors are nozzle diameter, nozzle angle, MQL supply pressure, distance between tool and nozzle and length of supply line. The cutting force and surface roughness were statistically analyzed by the use of the Box-Behnken method. As a results, optimum lubrication conditions were suggested and verification experiment has been performed. The results of this study are expected to help the selection of lubrication conditions in MQL turning.

• 한국시뮬레이션학회논문지
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• 제15권4호
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• pp.59-67
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• 2006

본 연구에서는 갠트리타입 기종을 사용한 PCB 조립 생산시 생산시스템의 수행도 향상을 위한 방안을 개발하여 제시한다. 갠트리타입의 기종에서는 헤더나 슬롯의 이동보다는 노즐의 교체가 시스템의 수행도 향상에 주된 걸림돌이 되므로 동시흡착을 최대화할 수 있는 방안을 모색하였다. 본 연구에서 제시된 해법은 피더의 위치와 노즐의 위치를 감안하여 동시흡착을 수행하도록 함으로써 노즐 교체를 최소화하고, 기판당 조립시간의 감소도 이루어지도록 하였다. 제안 해법의 유효성을 입증하기 위해 시뮬레이션 모형을 구축하고 부품의 수를 변화시켜가면서 다음 작업대상피더와 교체노즐의 선정을 다양하게 하여 여러 운영방안들의 수행도와 비교 분석하였다. 시뮬레이션 결과, 동시흡착을 유도하는 노즐교체를 할 경우 전반적인 수행상태가 양호한 것으로 나타났다.

• 설비공학논문집
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• 제23권11호
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• pp.754-761
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• 2011

The present study numerically investigates two-dimensional flow and heat transfer in the multiple confined impinging slot jet. Numerical simulations are performed for the different Reynolds numbers(Re=100 and 200) in the range of nozzles from 1 to 9 and height ratios(H/D) from 2 to 5, where H/D is the ratio of the channel height to the slot width. The vector plots of velocity profile, stagnation and averaged Nusselt number distributions are presented in this paper. The dependency of thermal fields on the Reynolds number, nozzle number and height ratio can be clarified by observing the Nusselt number as heat transfer characteristic at the stagnation point and impingement surface. The Nusselt number at the stagnation point of the central slot shows unsteadiness at H/D=3 and Re=200. The value of Nusselt number at the stagnation point of the central slot decreases with higher Reynolds number and number of nozzle although overall area averaged Nusselt number increases. Hence careful selection of geometrical parameters and number of nozzle are necessary for optimization of the heat transfer performance of multiple slot impinging jet.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.175-179
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• 2000

A combustion project was completed regarding the development of a high-flow-rate purge burner in cooperation with three city gas companies(Pusan, Taegu, Samchulli). The project, started in May 1991, aimed at purging the line-packed-gas safely and quickly before getting into gas pipe working or relocation. According to the results, the purging noise is less than 80dB due to silencer screen. multi-nozzle and outlet inserted tube employed. In addition, the developed burner shows an increased work efficiency of 40-50% more as compared to the performance of conventional purge equipments. The project result is regarded as the first high-flow-rate purge burner developed within Korea. contributing to shortening purge hours, safe field work and easiness of purge site selection.

• 한국CDE학회논문집
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• 제16권1호
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• pp.61-72
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• 2011

As the customer's needs for diverse colors, the process of bus painting shop is becoming more and more complex. In particular, frequent changes of paint colors in each spray process require the cleaning of the painting nozzles and setting them up for the new paints, which results in increased time and cost and reduced production. This also increases environmental influences. This paper proposes, as a solution to this issue, the use of color selection field (CSF). CSF is physically a system of conveyors that are used to rearrange objects in a flow line. CSF is proposed, in this paper, to be introduced right before the spray process so that buses are better grouped according to their desired colors. Various parameters of the CSF, such as the number of conveyors and algorithms to determine the rearranged sequence of buses, have been determined by running simulations using the digital manufacturing technology, and investigating the simulation results. As an outcome of the proposed solution, the CSF system is expected to reduce approximately 30% of the nozzle cleaning cost for a Korean motor company case, which will not only benefit the company economically, but will also benefit the environment.