• 한국음향학회지
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• 제29권8호
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• pp.497-503
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• 2010

본 논문은 여객선용 HVAC 시스템 목업을 구축하여 HVAC 요소의 성능평가를 수행한 결과를 다루었다. 측정은 룸 유니트 (Room Unit), 소음기 등 6가지 종류에 대해 이루어졌으며 여러 유량에 대해 삽입손실을 측정하였다. 소음기 직경이 작고 유량이 클수록 유동소음이 커져서 소음저감효과를 방해하지만, 직경이 커질수록 유동소음의 효과는 작아지고 삽입손실은 최대 25 dB까지 나타남을 확인하였다. 디퓨저 형태의 룸 유니트는 대체로 삽입손실이 0 - 10 dB 이지만 노즐 형태는 삽입손실이 최대 -15 dB 까지 소음이 커질 수 있음을 확인하였다. 또한 덕트 배열에 따라 최대 2 dB 까지 실내소음이 차이날 수 있음을 보였으며 각 룸 유니트에 동일한 유량이 배출하도록 조절하는 것이 보다 낮은 소음레벨을 얻을 수 있음을 확인하였다.

• 한국항공우주학회지
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• 제47권9호
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• pp.629-641
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• 2019

고온, 고압의 연소가스에 의해 유입되는 많은 열을 효과적으로 차단하여 고체 로켓 노즐의 공력형상을 최대한 유지하면서 구조물의 온도 상승을 일정수준 이하로 제한하기 위해 연소가스와 접하는 위치에 내삭마성이 우수한 C/C 복합재 등의 내열재를, 그 배면에는 열확산계수가 낮은 단열재를 적용한다. 내산화성이 우수한 SiC/SiC 복합재는 가스터빈 엔진에 적용되고 있으며, 경량화와 내열성 향상으로 인해 엔진 성능 증가에 기여하고 있다. 극초음속으로 비행하는 스크램제트는 흡입 공기 온도가 매우 높아서 흡열 연료를 냉각제로 사용하는 C/SiC 구조물 개발 연구가 수행되고 있다. 본 논문에서는 고체 로켓 노즐, 가스터빈 엔진 및 램제트/스크램제트 추진기관에 사용되는 다양한 내열 복합재의 특성, 적용사례 및 개발 동향을 고찰하였다.

• 한국염색가공학회지
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• 제34권2호
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• pp.109-116
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• 2022

Tire codes are made of materials such as hemp, cotton, rayon, nylon, steel, polyester, glass, and aramid are fiber reinforcement materials that go inside rubber to increase durability, driveability, and stability of vehicle tires. The reinforcement of the tire cord may construct a composite material using tires such as automobiles, trucks, aircraft, bicycles, and fibrous materials such as electric belts and hoses as reinforcement materials. Therefore, it is essential to ensure that the adhesive force between the rubber and the reinforced fiber exhibits the desired physical properties in the rubber composite material made of a rubber matrix with reinforced fibers. This study is a study on the heat treatment conditions for improving the adhesion strength of the tire cord and the reinforced fiber for tires. The core technology of the drying process is a uniform drying technology, which has a great influence on the quality of the reinforcement. Therefore, the uniform airflow distribution is determined by the geometry and operating conditions of the dryer. Therefore, this study carried out a numerical analysis of the shape of a drying nozzle for improving the performance of hot air drying in a dryer used for drying the coated reinforced fibers. In addition, the flow characteristics were examined through numerical analysis of the study on the change in the shape of the chamber affecting drying.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1135-1143
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• 2002

The intermittent spray characteristics of the single-hole diesel nozzle (d$\sub$n/=0.32 mm) used in the fuel injection system of heavy-duty diesel engines were experimentally investigated. The mean velocity and turbulent characteristics of the diesel spray injected intermittently into the still ambient were measured by using a 2-D PDPA (phase Doppler particle analyzer) . The gradient of spray half-width linearly increased with time from the start of injection, and it approximated to 0.04 at the end of the injection. The axial mean velocity of the fuel spray measured along the radial direction was similar to that of the free air jet within R/b= 1.0-1.5 regardless of elapsing time, and its non-dimensional distribution corresponds to the theoretical velocity distributions suggested by Hinze in the downstream of the spray flow fields. The turbulent intensity of the axial velocity components measured along the radial direction represented the 20-30% of the U$\sub$cι/ and tended to decrease in the outer region. The turbulent intensity in the trailing edge was higher than that in the leading edge.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.367-370
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• 2006

This paper deals with the modeling and simulation of the internal flowfield in a valveless airbreathing pulse detonation engine (PDE) currently under experimental development at the U.S. Naval Postgraduate School. The system involves no valves in the airflow path, and the isolation between the inlet and combustor is achieved through the gasdynamics in an isolator. The analysis accommodates the full conservation equations in axisymmetric coordinates, and takes into account variable properties for ethylene/oxygen/air system. Chemical reaction schemes with a single progress variable are implemented to minimize the computational burden. Detailed flow evolution during a full cycle is explored and propulsive performance is calculated. Effect of initiator mass injection rate is examined and results indicate that the mass injection rate should be carefully selected to avoid the formation of recirculation zones in the initial cold flowfield. Flow evolution results demonstrate a successful detonation transmission from the initiator to the combustor. However, strong pressure disturbance may propagate upstream to the inlet nozzle, suggesting the current configuration could be further refined to provide more efficient isolation between the inlet and combustor.

• 한국분무공학회지
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• 제2권2호
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• pp.8-15
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• 1997

Combustion chamber systems using spray impinged on walls have been studied for improving combustion characteristics in high speed direct injection diesel engines. The fuel spray injected in a small combustion chamber may be easily impinged and deposited on the wall. The fuel deposit has been considered as the cause for unburned emission due to difficulty of fuel-air mixing. In this paper w-shaped combustion chamber which has four raised pips on the side wall is introduced and discussed by comparing with conventional chamber with no pips. The computer code employing new spray-wall interaction model in general non-orthogonal grids is used in here. The model is applied into the new chamber shape with raised pips. In this chamber system four-hole nozzle is used, and the sprays injected from the each hole impact on lands raised from the chamber wall surface. After impacting, the sprays break up into much smaller drops and distribute over all the chamber space, instead of distributing just near the wall surface in conventional omega-shape. The results showed the potential of the w-shaped chamber employing pips for dispersing droplets so as tn avoid the fuel deposit regions.

• 항공우주시스템공학회지
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• 제11권1호
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• pp.8-13
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• 2017

한국형 발사체 3단 엔진용 터보펌프 터빈에 관해 성능 시험을 수행하여 성능 특성 결과를 분석하였다. 터빈은 초음속 충동형 방식의 단단 형태이며, 노즐은 시동 노즐 1개와 정상 운전용 노즐 4개로 이루어졌으며, 부분 분사 형태로 되어 있다. 한국항공우주연구원 내의 고압 공기 터빈 상사 시험 설비를 이용하여 상사 시험을 수행하였다. 시험 결과 효율은 회전수 변화에 크게 변화하며, 이에 반해 압력비 변화에는 다소 작게 변화하는 초음속 충동형 터빈의 일반적인 특성을 보이고 있다.

• 한국추진공학회지
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• 제10권2호
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• pp.115-128
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• 2006

스크램제트 추진기술에 대한 최근 개발동향과 주요기술을 분석하였다. 스크램제트엔진은 지난 10여년간 급속한 기술 발전으로 지상시험에서 비행시험 단계에 접어들고 있으며, 수년 내 실용시험을 목표로 활발하게 연구개발 중이다. 광범위한 비행 마하수를 만족하는 이중연소램제트와 이중모드램제트 형태의 엔진은 각각 군용과 민수용으로 개발되고 있으며, 복합엔진은 차세대 우주발사체의 대안으로 개발되고 있다. 엔진 작동 특성의 미케니즘에 대한 정확한 이해와 이에 상응되는 기술, 흡열연료 및 CSiC 복합재료를 사용한 내열 문제 해결, 가변 흡입구와 노즐을 이용한 안정된 추진력 구현을 목전에 두고 있다.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2000년도 추계학술대회
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• pp.39-41
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• 2000

Newly modified spray Pyrolysis system was developed to Produce ultra Pure and fine Powder by spray Pyrolysis Process. In this system, raw material solution was effectively atomized and sprayed into the reaction furnace. Also, thermal decomposition process fully completed in the three zone reaction furnace, and produced powder was effectively collected. A technology to reduce impurities in complex acid solution below 20ppm was also developed. The characteristics of produced powder were studied by changing the reaction conditions such as reaction temperature, the injection velocity of the solution and air, nozzle tip size and concentration of solution. The morphology of powder had spherical shape under the most experimental conditions, and the composition and the particle size distribution were almost uniform. Under the most experimental conditions average particle size of most produced powder was below 100nm.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.843-851
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• 2022

This paper was conducted to study the conditions for the manufacture and operation of artificial snow removal and ice-making test facilities so that the test equipment can be tested in a low-temperature environment using the polar environment performance test facility. The polar environment performance test Facility is designed to artificially simulate extreme environments up to -65 ℃, and is a mid-to-large low-temperature environment test facility that can perform performance tests on offshore plant equipment, ships, leisure, and offshore structures. To verify the safety of deck work of ships operating in polar environments, artificial snow removal and artificial ice making devices were manufactured, and we conducted research on various operating environments using these facilities. For the efficient operation of artificial snow and ice making facilities, it is important to continuously supply dry air, and it has been found that installing an additional heater at the tip of the nozzle is effective in preventing freezing.